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Ogden, Sam. "High-Pressure Microfluidics." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208915.
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In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps. A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax. A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption. In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling. One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.
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Gomez, Nicasio. "PCV valve flutter : vibration characterization through pressure and flow." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32895.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 51).
A Positive Crankcase Ventilation, or PCV, valve is required by internal combustion engines in order to regulate the flow of blow-by gases out of the crankcase and into the intake air stream. Fluctuations in the pressure and flow of these gases lead to poor performance and can be detrimental to engine durability. This thesis addresses a specific case of PCV valve component vibration, or flutter, which in certain conditions has been severe enough to be perceived by the customer. Tests monitoring pressure and flow were performed in a variety of test setups in order to simulate every real-world scenario possible at the bench level. Data attained was analyzed in order to identify and characterize any and all patterns in pressure and flow indicative of flutter conditions. The end result of this thesis is summarized in a recommended test procedure to be followed in future cases of PCV valve flutter.
by Nicasio Gomez, III.
S.B.
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Ozkan, Tulay. "Leakage Control By Optimal Valve Operation." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609419/index.pdf.
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The main function of a water distribution system is to supply water in sufficient quantity at appropriate pressure with an acceptable quality and as economically as possible. Water leakage in distribution networks may account from 5% to 50% and even larger of the total water delivered. The amount of leakage in a network is directly related to system service pressure. Therefore, reductions in high service pressures will result in considerable reductions in leakage. A methodology for leakage reduction has been presented in context of a developed computer program, LEAKSOL with two sub-programs. The first code, CODE I, provides solution by using optimization techniques with defined pressure-leakage and pressure-demand relations in order to find optimal flow control valve settings minimizing water leakage. The second one, CODE II, makes hydraulic analysis of the network in order to solve the system and to compute the amount of leakage and the amount of water consumed, by using different combinations of isolation valves generated according to the number of valves given and employing the relationships among pressure, leakage and consumption. Computer program application was performed for different scenarios in a sample network previously used in literature and also in N8-3 pressure zone of Ankara Municipal Water Supply System. Leakage reduction up to 10 % has been achieved in N8-3 pressure zone for eight valves located at the entrances of sub-zones, depending on the defined pressure-leakage relationship.
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Huang, Jiahai, Long Quan, and Youshan Gao. "Characteristics of Proportional Flow Control Poppet Valve with Pilot Pressure Compensation." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-199471.
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Electro-hydraulic proportional flow valves are widely used in hydraulic industry. There are several different structures and working principles. However, flow valves based on the existing principles usually have some shortcomings such as the complexity of the system and additional energy losses. A concept for a two-stage poppet flow valve with pilot pressure drop – pilot spool opening compensation is presented, and the linear relationship between the pilot stage and main stage, the semi-empirical flow equation are used in the electronic flow controller. To achieve the accurate control of the outlet flow, the actual input voltage of the pilot spool valve is regulated according to the actual pilot pressure drop, the desired flow rate and the given input voltage. The results show that the pilot pressure drop – pilot spool opening compensation method is feasible, and the proposed proportional flow control valve with this compensation method has a good static and dynamic performance.
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Ritchie, Greg. "Minimizing pressure relief valve seat leakage through optimization of design parameters." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/31013.
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Nasr, Ahmed. "Computational and experimental studies of flow through a plate valve." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243954.
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CARNEIRO, LEONARDO MOTTA. "STUDY OF THE DYNAMIC BEHAVIOR OF SPRING PRESSURE RELIEF VALVE FOR PIPELINES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=21693@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA grande maioria dos dutos de transporte de petróleo e derivados no Brasil trabalha com válvulas de alívio no projeto dos seus sistemas de proteção. Desta forma, o perfeito dimensionamento e funcionamento destas válvulas são fundamentais para garantir a segurança de dutos de transporte e dos terminais de carga e descarga, caso haja alguma condição anormal de operação que gere sobrepressões. Estas válvulas aliviam a pressão interna do duto caso a mesma ultrapasse um valor definido e calibrado na válvula. Simplificadamente, a válvula de alívio de pressão tipo mola possui um disco o qual é pressionado pela mola contra o bocal de entrada. Quando a pressão do duto se eleva, a força gerada na superfície do disco aumenta e, dependendo do ponto de ajuste da mola, supera a força exercida pela mesma fazendo com que o disco se eleve, descarregando pelo bocal de saída o fluido para o tanque de alívio e, consequentemente, reduzindo a pressão no duto. Desta forma, a válvula de alívio garante que o duto não seja submetido a pressões superiores às pressões de projeto, o que poderia levar a uma falha do duto e a um possível vazamento de produto para meio ambiente. Este trabalho propõe um estudo experimental e numérico para determinar o comportamento dinâmico de válvulas de alívio de mola. Foi realizada a montagem de uma bancada experimental com um circuito de água contendo uma bomba, uma válvula de alívio e uma válvula de bloqueio capaz de interromper o fluxo no circuito gerando um transiente de pressão que obriga a abertura da válvula para aliviar a pressão interna no sistema. A válvula de alívio foi instrumentada para medir as grandezas necessárias para estudar o comportamento dinâmico da válvula e os transientes de pressão e vazão gerados no duto. Os resultados experimentais foram comparados com os resultados obtidos de modelos computacionais proporcionando o aperfeiçoamento e validação destes modelos.
The majority of oil and refined product pipelines in Brazil employ pressure relief valves in the design of their protection system. Thus, the perfect design and operation of these valves is essential to ensure the safety of transport pipelines and loading and unloading terminals, under any abnormal condition of operation that generates overpressures. These valves work by relieving the internal pressure in case it exceeds a pre-set and calibrated value. In a nutshell, the spring-type pressure relief valve has a disk which is pressed by a spring against the inlet nozzle of the valve. When the pressure rises, the force generated on the surface of the disc increases and, depending on the pressure relief valve set point, the pressure force overcomes the force exerted by the spring, causing the disk to rise and thus discharging the fluid through the outlet nozzle to the relief tank, consequently reducing the pressure in the pipeline. Using this principle, the relief valve ensures that the pipeline is not subjected to high transient pressures, which could lead to pipeline or equipment rupture and possible product leak. The present dissertation describes a numerical and experimental study conducted to determine the dynamic behavior of spring-type relief valves. The experiments were conducted in a water pipe loop equipped a pump, a block valve to generate the pressure transients and a commercial spring-type pressure relief valve. The loop was instrumented with pressure, flow and temperature transducers. The relief valve was instrumented to measure the variables necessary to study the dynamic behavior of the valve and the transient pressure and flow generated in the pipeline. The experimental results were compared with results obtained from computer models allowing the improvement and validation of these models.
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PÉREZ, MARCOS JOSÉ BABILONIA. "STUDY OF THE DYNAMIC BEHAVIOR OF A SPRING-TYPE PRESSURE RELIEF VALVE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=28093@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
As válvulas de alívio de pressão (PRVs, do inglês, pressure relief valves) são dispositivos fundamentais para a segurança de operações em dutos de transporte de fluidos, sendo encarregadas de garantir a integridade das instalações no caso de algum bloqueio súbito do escoamento. Dependendo da natureza e duração do evento de bloqueio, das características da válvula de alívio e do comprimento do duto, o comportamento dinâmico da PRV, i.e., seu tempo de resposta e o coeficiente de descarga em função da abertura, podem variar consideravelmente. Estas informações mais detalhadas sobre o comportamento transiente da válvula não são especificadas em normas e raramente são disponibilizadas pelos fabricantes. Uma caracterização detalhada do comportamento dinâmico da válvula de alívio é informação importante para a simulação computacional de transientes hidráulicos em dutos de líquido. Em particular, o comportamento dinâmico do coeficiente de descarga da válvula não é conhecido, sendo por vezes simplificadamente representado por dados obtidos em condições de regime permanente. No presente trabalho foi realizado um estudo detalhado do comportamento dinâmico de um modelo de válvula de alívio, com o objetivo de obter informações comparativas sobre o comportamento do coeficiente de descarga da válvula quando investigada sob condições de regime permanente e transiente rápido. Para isso, construiu-se um modelo de PRV transparente, permitindo a medição de campos instantâneos de escoamento em seu interior com a técnica de Velocimetria por Imagem de Partículas em duas dimensões (PIV). Transdutores de pressão e deslocamento foram devidamente instalados de maneira a fornecer informações instantâneas sobre a queda de pressão e posição de abertura da válvula, com alta resolução temporal. O modelo da válvula transparente foi montado em um circuito fechado, no qual água era bombeada através de uma tubulação longa, passando pela PRV e por uma válvula de bloqueio com tempo de fechamento controlado eletronicamente, podendo produzir bloqueios súbitos no escoamento, com tempos na faixa de 4 ms a 3,5 s. Sistemas de controle foram especialmente desenvolvidos para sincronizar os eventos de bloqueio da válvula, disparo do laser do sistema PIV, aquisição de imagens e dados de pressão e deslocamento. Estes dados permitiram a determinação do valor instantâneo e de média de fase para o coeficiente de descarga da válvula de alívio de pressão no caso transiente.
Pressure relief valves (PRVs) are important devices which guarantee the safe operation of liquid pipelines, being responsible for preserving the integrity of the duct in case a sudden flow blockage event occurs. The PRV s dynamic behavior, that is, its response time and discharge coefficient as a function of open fraction, can vary considerably depending on the nature and duration of the blockage event, on the valve s characteristics and on the duct length. This more detailed information on the valve s transient behavior is not specified in standards and is rarely made available by valve manufacturers. A detailed characterization of the valve s dynamic behavior is relevant information for the computational simulation of hydraulic transients in liquid pipelines. In particular, the dynamic behavior of the valve discharge coefficient is not known, being normally replaced by data obtained from tests under steady state conditions. In the present work, a detailed study was conducted using a valve model with the objective of obtaining comparative information on the valve discharge coefficient for steady and transient conditions. To this end, a transparent PRV model was constructed in order to allow for the use of the two-dimensional Particle Image Velocimetry technique (PIV) for measuring the instantaneous flow field inside the valve. Pressure and displacement transducers were employed to yield instantaneous information on the pressure drop and valve opening. The valve model was installed in a closed circuit where water was pumped through a long pipe, passing through the PRV and through the blockage valve that was capable of producing flow blockage events in the range of 4 ms to 3.5 s. Control systems were specially constructed to synchronize the events of valve blockage, PIV laser firing, and acquisition of pressure, and displacement data. These data allowed the determination of the instantaneous and phase-averaged values for the valve discharge coefficient.
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McGregor, Brian. "The left ventricle, aortic valve, and arterial tree - a fresh engineering perspective." Thesis, University of Ulster, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339346.
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Brubaker, Christopher L. "Dynamic Model of a Non-Linear Pneumatic Pressure Modulating Valve Using Bond Graphs." Cleveland State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=csu1432264539.
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Rannow, Michael. "Fail Operational Controls for an Independent Metering Valve." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200685.
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As intelligent hydraulic systems with embedded sensors become more ubiquitous, the real or perceived reliability challenge associated with sensors must be addressed to encourage their adoption. In this paper, a fault-tolerant control strategy for an intelligent independent metering valve that allows continued operation if a sensor fails is described. The twin-spool valve example utilizes position sensors to stabilize the spool positions and eliminate hysteresis, and pressure sensors to provide digital pressure compensation, electronic load sensing, and other features. An independent metering valve has redundancy provided by four sensors working together to control the flow into and out of a single actuator. Although two sensors are needed to control the flow through a spool, the controller can be reconfigured to ensure the flow is always controlled on the spool with both sensors working. To accomplish this, the concept of cross-port pressure control is introduced that uses the faulty side of the valve to maintain constant pressure on the non-faulty side. By maintaining a constant pressure, the flow in and out of the actuator are balanced. Experimental results on the boom of a backhoe demonstrate the operation of the fault tolerant control strategy.
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Almström, Linda, and Camilla Söderström. "Alternative materials for high-temperature and high-pressure valves." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-7393.
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AB SOMAS Ventiler manufactures valves for different applications. A valve of type DN VSSL 400, PN 100, used in high-temperature and high-pressure applications was investigated in this thesis. This type of valve is coated with high cobalt alloys to achieve the tribological properties needed for this severe condition. However there is a request from AB Somas Ventiler to find another solution. This request is based on the fact that demands on higher temperatures, from customers, yields higher requirements on the material. It is also a price issue since cobalt is quite expensive. Materials investigated were high-nitrogen steel, Vanax 75, nickel-based superalloy Inconel 718 and hardened steels, EN 1.4903 and EN 1.4923 presently used as base material in the valve. Calculation of contact pressure that arises when the valve is closed was first approached by using finite element method (FEM). Several models were constructed to show the behavior of the valve during closing in terms of deformation. Hot wear tests, in which a specimen was pressed against a rotating cylinder, were performed to be able to compare the materials to the solution of today and among each other. Data extracted from the tests were compiled in the form of coefficients of friction. Profilometer examinations were used to reveal the volumes of worn and adhered material and together with scanning electron microscopy (SEM) the wear situation for each material couple could be assessed. Wear mechanisms detected in SEM were adhesive and abrasive and the results clearly showed that the steels were not a good solution because of severe adhesive wear due to the similarity of mating materials creating a more efficient bonding between the asperities. Vanax 75 showed much better performance but there was still an obvious difference between the steels and the superalloy in terms of both coefficient of friction and amount of wear. On this basis, Inconel 718 was selected as the most suitable material to replace the high cobalt alloys used in the valves today.AB Somas ventiler är ett företag som tillverkar ventiler för ett brett spann av applikationer. I det här examensarbetet har undersökningar genomförts på en ventil av modell DN VSSL 400, PN 100, som normalt används i applikationer för höga tryck och höga temperaturer. Ventilen beläggs i dagsläget med höghaltiga koboltlegeringar för att uppnå de tribologiska egenskaper som krävs i de påfrestande arbetsförhållanden som råder. AB Somas Ventiler har dock framfört en förfrågan om att hitta en alternativ lösning, en förfrågan som grundar sig i att kundernas ständiga önskemål på att ventilerna ska klara högre arbetstemperaturer också medför högre krav på ventilmaterialen. Det är även en prisfråga, då kobolt är en dyr legering att använda sig av. De material som inkluderades i undersökningen var det kvävelegerade stålet Vanax 75, nickelbaserade superlegeringen Inconel 718 samt de två stålen EN 1.4903 och EN 1.4923 i härdat tillstånd. De två sistnämnda används idag som basmaterial i ventilen. Genom att använda den finita element metoden (FEM) kunde en första beräkning göras av det kontakttryck som uppstår då ventilen stängs. Flera modeller konstruerades för att simulera ventilens deformation vid stängning. Där efter utfördes nötningstester i hög temperatur på de alternativa materialen, genom att låta en provbit pressas mot en roterande cylinder, för att sedan kunna göra en jämförelse mellan materialen och även med den nuvarande lösningen. Från nötningstesterna erhölls data som kunde användas för att ta fram friktionskoefficienter för de olika materialparen. Med hjälp av undersökningar med profilometer och svepelektronmikroskop (SEM) kunde värden på nötta och vidhäfta volymer erhållas tillsammans med information om nötningssituationer för ytorna mellan de olika materialparen. De nötningsmekanismer som påvisades med hjälp av SEM-undersökningen var adhesiv och abrasiv nötning, och resultaten visade tydligt att nötningen av stålen var omfattande, på grund av att lika material i kontakt med varandra skapar starkare band mellan ytorna, och att de därför inte var en intressant lösning. Det kvävelegerade Vanax 75 uppförde sig visserligen bättre men en tydlig skillnad mot superlegeringarna kunde dock fortfarande konstateras, sett till både friktionskoefficient och mängden slitage. Baserat på dessa resultat valdes Inconel 718 som det bäst lämpade materialet att ersätta de höghaltiga koboltlegeringarna som idag används i ventilen.
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Sutherland, Erika Susanne. "Analysis of the performance and stability of a passive recirculation loop for hydrogen delivery to a PEM fuel cell system." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/443.
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Proton Exchange Membrane (PEM) fuel cells are becoming an increasingly important alternative to combustion engines as the fossil fuel reserves are depleted. Several papers have presented steady state analyses of the system, but few are known to present dynamic analysis of the flow and control of the hydrogen delivery process. This thesis presents the dynamic analysis of hydrogen delivery to a PEM fuel cell system. The hydrogen is delivered to the anode with use of an ejector for passive recirculation. The system to be studied consists of the manifolds, ejector, and pressure control valve. Models describing the elements of the anode delivery systems are formulated. The governing nonlinear equations are solved analytically and numerically, and the regimes of stable hydrogen delivery process are established. The linearized models are used for performance analysis and optimization of the hydrogen delivery process. The nonlinear model is used to improve the simulation of the dynamics of the PEM fuel cell system and validate the parameters at optimal linearized stability. Experiments are conducted to find the parameters used in the model, as well as validate the results. Both the linear and nonlinear models are implemented in Simulink and tested against the laboratory data from the PEM fuel cell system. The analysis showed that the models have the same time constant and dynamic behavior as the PEM system. The optimal parameters for stability and a faster response with no oscillations in the output are obtained. The redesigned valve and resulting dynamics of the PEM fuel cell system provides improved system performance.
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MendonÃa, Doglasse Ernesto. "Osmosis reverse plant powered by photovoltaic modules with MPPT and self regulated pressure valve." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=16455.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoThis project presents a brackish water desalination plant via Reverse Osmosis (RO) powered by Photovoltaic Modules (PV) with Maximum Power Tracking (MPPT) and a self â regulating pressure valve. The developed unit is installed on Alternative Energy Laboratory (LEA), which is located on the campus of PICI at Federal University of CearÃ. To extract maximum power from the PV module a Buck type converter was developed for this application. The Incremental Conductance algorithms (IncCond) is used. The MPPT technique was simulated, tested and validated, showing an efficiency of 86.8%. An innovation in this plant is the use of a self-regulating pressure valve installed in the concentrate output, which ensures a smaller pressure and power variation in the pump that is responsible for pressurizing the water to the membranes. The technical feasibility of the RO plant is checked in two phases: one without the presence of the self- regulating pressure valve in the concentrated output and other with the self-regulating pressure valve in the concentrated output. The plant is tested for two salinity levels 1000 and 1500 mg/L of TDS (Total Dissolved Solids) levels. These salinity levels chosen are commonly found in most brackish water wells of the semi-arid region of Northeastern Brazil. For operation without selfregulating pressure valve the obtained average values are: recovery rate 8.03% (relation between permeate flow and feed water flow), 151.7 L of daily production of drinking water with 130 mg/L of TDS, specific energy consumption of 2.68 kWh/m3. For operation with self-regulating pressure valve the obtained average values are: recovery rate 8.14%, 175.3 L of daily production of drinking water with 120 mg/L of TDS, specific energy consumption of 2.56 kWh/m3. Thus the configuration system using the self â regulating valve showed better results
O presente projecto apresenta uma planta de dessalinizaÃÃo de Ãgua salobra por osmose reversa (OR) acionada por mÃdulos fotovoltaicos (FV) com seguimento de potÃncia mÃxima (MPPT - Maximum Power Point Tracking) e vÃlvula autoreguladora de pressÃo. A planta desenvolvida està instalada no LaboratÃrio de Energias Alternativas (LEA), situado no Campus do PICI da Universidade Federal do CearÃ. Para extraÃÃo da mÃxima de energia do mÃdulo FV foi desenvolvido um conversor do tipo Buck, usando a tÃcnica CondutÃncia Incremental (CondInc). A tÃcnica de MPPT foi simulada, testada e validada, apresentando uma eficiÃncia de 86,8% no seguimento do ponto de potÃncia mÃxima. Uma inovaÃÃo na planta proposta à o uso de uma vÃlvula autoreguladora de pressÃo instalada na saÃda do concentrado, que garante uma menor variaÃÃo de pressÃo e corrente eletrica na motobomba responsÃvel por pressurizaÃÃo da Ãgua para as membranas. A planta de OR foi testada em duas etapas: uma sem a presenÃa da vÃlvula auto-reguladora de pressÃo e a outra com a vÃlvula, para uma Ãgua de alimentaÃÃo entre os nÃveis de salinidade de 1000 e 1500 mg/L de STD (SÃlidos Totais Dissolvidos). Estes nÃveis de salinidade adotados sÃo geralmente encontrados em poÃos com Ãgua salobra do semiÃrido do Nordeste do Brasil e noutros casos maior 1500 mg/L de STD. Para a operaÃÃo sem a vÃlvula autoreguladora de pressÃo foram obtidos os seguintes valores mÃdios: taxa de recuperaÃÃo 8,03%, produÃÃo de Ãgua potÃvel de 151,7 L/dia com 130 mg/L de STD, consumo especÃfico de energia de 2,68 kWh/m3. Para a operaÃÃo com a vÃlvula autoreguladora de pressÃo foram obtidos os seguintes valores mÃdios: taxa de recuperaÃÃo 8,14%, produÃÃo de Ãgua potÃvel de 175,3 L/dia com 120 mg/L de STD, consumo especÃfico de energia de 2,56 kWh/m3. No entanto a configuraÃÃo da planta operando com a vÃlvula autoreguladora de pressÃo apresenta melhores resultados relativamente a operaÃÃo sem a vÃlvula.
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Thomas, Vineet Sunny. "A Comparative Study for the Effect of Tissure Anisotropy on the Behavior of a Single Cardiac Pressure Cycle for a Symmetric Tri-Leaflet Valve." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1284703306.
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Sors, Felix, and Patrik Holm. "Development of Steam Turbine Inlet Control Valve for Supercritical Pressure at Siemens Industrial Turbomachinery AB." Thesis, Linköping University, Machine Design, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-57805.
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The development in the steam turbine business is heading for applications with much higher steam parameters since this enables a raised efficiency. Steam parameters refer to the pressure and the temperature of the steam. The aim of this study was to generate concepts for steam turbine inlet control valves designed for higher pressure and temperature in comparison with the present design. Future steam power plants using solar energy, based on tower technology, request this kind of performance and are an important potential market.
This master thesis at Linköping University has been written in collaboration with Siemens Industrial Turbomachinery AB. The performed work has incorporated literature studies, functional analysis and solid mechanics analysis, flow analysis, evaluation of sealings and cup springs and development of the dimensioning data for the future control valve. The aim was to find a design concept that sustains the new and higher steam parameters and is tolerant concerning vibrations.
A systematical way to work has been applied during the project and a detailed planning was continuously followed and adjusted. Major methods used were product design specification, quality function deployment, morphological matrices, decision matrices and failure mode and effect analysis. Important programs used during the project were Pro/ENGINEER, MATLAB, FloEFD and MS Excel.
Today’s valves are dimensioned for much lower performance than the new requirements in terms of pressure and temperature. The main problem for the present design is that the opening and closing forces requirements, with the new higher pressure, get unreasonably large. Therefore were many of the developed concepts equipped with a pressure balancing feature. This feature also gives another desirable result; the vibrations (that is the source of many of the problems with the present design) will also be reduced.
During the early concept development phase, 15 different concepts were generated and after the concept evaluation only three concepts remained. These concepts were further developed in different areas of interest and finally one of the three was chosen to be the winning concept. The new valve design will most likely meet the requirements and has the potential to be refined for even higher pressure for future demands.
Utvecklingen inom ångturbiner går mot applikationer med mycket högre ångdata eftersom detta möjliggör en ökad effektivitet. Ångdata refererar till ångans tryck och temperatur. Uppgiften var att generera koncept för inloppsreglerventiler (till ångturbiner) dimensionerade för högre tryck och temperatur jämfört med dagens design. Framtida ångkraftverk som drivs av solenergi, så kallade soltorn, efterfrågar denna prestanda och är en viktig framtida marknad.
Detta examensarbete vid Linköpings Universitet har skrivits i samverkan med Siemens Industrial Turbomachinery AB. Det genomförda arbetet har innefattat litteraturstudier, funktionsanalys och hållfasthetsanalys, flödesanalys, utvärdering av tätningar och tallriksfjädrar samt framtagning av dimensioneringsunderlag för den framtida reglerventilen. Målet var att finna ett koncept som klarar av dessa nya och högre ångdata och är tåligt beträffande vibrationer.
Ett systematiskt arbetssätt har anammats under projektet och en detaljerad planering upprättades och uppdaterades kontinuerligt. Viktiga metoder som använts är PDS (Product Design Specification), QFD (Quality Function Deployment), morfologisk matris, relativ beslutsmatris och feleffektanalys. Viktiga program som använts i projektet är Pro/ENGINEER, MATLAB, FloEFD och MS Excel.
Dagens ventiler är dimensionerade för mycket lägre prestanda än de nya kraven kräver i termer av tryck och temperatur. Det huvudsakliga problemet med den nuvarande designen var att kraven på de öppnande och stängande krafterna, med dessa nya ångdata, blir orimligt höga. Därför har många av de framtagna koncepten utrustats med tryckbalanserande funktion. Denna funktion ger också ett annat önskvärt resultat; vibrationerna (som är källan till många problem med dagens design) kommer även de att reduceras.
Under den tidiga konceptutvecklingsfasen genererades 15 olika koncept och efter konceptutvärderingen återstod bara tre. Dessa koncept vidareutvecklades inom olika intressanta områden och slutligen valdes ett av koncepten som det vinnande. Den nya ventildesignen kommer med stor sannolikhet att uppfylla kraven och har potential att förfinas för ännu högre tryck för framtida krav.
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Schipke, Kimberly Jo. "DESIGN OF A CYCLIC PRESSURE BIOREACTOR FOR THE EX VIVO STUDY OF AORTIC HEART VALVE MECHANOBIOLOGY." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07112008-155755/.
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The differentiation of myosin into the respective heavy chain isoforms has shown a correlation with high mechanical stress. Aortic valve myosin expression has been reported; however, the characterization of the pressure response has yet to be fully developed. Thus, a cyclic pressure bioreactor was developed to elucidate the á/â-myosin heavy chain (MHC) expression in aortic valve leaflets subject to physiological and pathological transvalvular pressure loads. The pressure bioreactor achieved the desired pressure modulation via LabVIEW controlled solenoid valves. Results showed á/â-MHC expression on the fibrosal endothelium and minimal dispersal in the subendothelium, indicating the presence of smooth muscle cells. Endothelial layer denudation was evident with time progression while protein expression was limited to sites of excision or injury, indicating a causal relationship with high shear stress. In conclusion, á/â-MHC expression is limited by endothelium detachment and lack of smooth muscle cells, possibly on account of insufficient mechanical stimuli.
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Jönsson, Emil. "Pressure distributions on a valve disk at different opening angles and their impacts on the shaft." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-44367.
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Valves are used in the most pipe systems today. There are a lot of different valves used depending on the system. They all do have in common to withstand all possible kind of failure that might occur. Common issues are cavitation, water hammer and friction torque. Friction torque is dependent on the deflection of the valve due to the high load on the valve body, for a butterfly valve this will be the disk. The pressure distributed on the disk differ depending on the opening angle of the butterfly valve. Opening angles of 3, 15 and 30 degrees are investigated. The further the valve is opened the lower the pressure will be on the downstream side and also the total pressure on the disk is decreased. This investigation shows that the impact in terms of deflection angle is constant for the lower opening degrees but for 30 degrees of opening there is a drop in deflection angle on the shaft. This means that the shaft will absorb less force due to loading on the disk and lead to reduced friction torque. With use of the same inlet pressure the angle causing the deflection increased linearly.
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Gardell, Jens. "Benchmark of RELAP5 Check Valve Models against Experimental Data." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-103609.
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The use of check valves in the nuclear industry is of great importance from a safety precaution point ofview (McElhaney, 1995). Choosing check valves for these high-pressurized systems comes with agreat challenge. The valves causes what is called check valve slams when closing, leading to a hugepressure wave traveling through the system. To prevent this from happening calculations have to bedone to see what kind of forces are generated during a check valve slam. When the forces are known itis easier designing systems that will endure these slams. A commonly used software in the nuclearindustry is RELAP5 (Reactor Excursion and Leak Analysis Program), its main purpose is to calculatetransients in piping systems. This program can also be used when calculating a check valve slam. Buthow precise is the code compared to the real event? By doing an experiment measuring pressures created by swing check valves during slams, the codewas compared to real data and analyzed to decide what was of importance when modeling for thesetypes of simulations. The RELAP5 code was not initially designed to calculate transients during a check valve slam. This isclearly shown when the code overestimates the pressure waves in the system when using themanufacturer data for the check valve model. Matching the data from the simulations in RELAP5 withthe data recorded from the experiment is not easy. The parameters used for this have no connection tothe specifications for the check valve, which means that transients are hard to estimate withoutexperimental data.
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Taljaard, Francois George. "Analytical control valve selection for mine water reticulation systems / F.G. Taljaard." Thesis, North-West University, 2012. http://hdl.handle.net/10394/9703.
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Some of the largest and deepest mines in the world are situated in South Africa. Underground temperatures and humidity can be controlled by means of complex chilled water reticulation system. A cascade pumping system is used to pump the used water from the underground levels back to the surface.
The dewatering process is energy intensive. Large volumes of water are used during the general mine drilling periods (06:00 to 12:00). During blasting periods (15:00 to 18:00) a minimum amount of personnel are underground, yet large volumes of water are still sent underground due to a lack of control. Reducing the water sent underground, will reduce the amount of water pumped back to the surface; resulting in significant energy savings.
Water flow and pressure can be managed by installing control valves at appropriate positions throughout the water reticulation system. Selecting a control valve is typically governed by constraints such as cavitation, water hammer, flashing, safety ratings and control range. A basic set of calculations can be used to determine whether a valve conforms to a specific scenario. However, scenarios calculated by engineers are not indicative of all applied system scenarios.
When control valves are installed, to optimise the operation of a system, it affects the system’s characteristics. Sampled system data will therefore no longer provide adequate readings to help with selecting the correct control valve. An analytical control valve selection method has been developed and implemented. The case study shows the results and practical implications of applying this method in the mining industry. Implementing the analytical valve selection method is shown to be viable, realising electrical energy cost savings for the mine by reducing power requirements from Eskom. Analytical control valve selection for mine water reticulation systemsThesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.
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Aengenheister, Stefan, Chao Liu, Christoph Broeckmann, and Katharina Schmitz. "Functional proof of a flat slide valve as a 4/3-way proportional valve." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71085.
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With a flat slide valve concept, when compared to conventional piston spool valves, reduced leakage and increased service life could be achieved. In order to achieve a reduction of leakage flows and guarantee the adjustability of the valves at the same time, a correct design of the pressure compensation is essential. The magnitude of force depends on both the operating point of the valve and the position of the slider. Due to the design of the flat slide valve, it is possible to use ceramic semi-finished products for the main stage, which consist of control plates and a slide plate. The geometries are simple enough to be inexpensively manufactured with sufficient accuracy, using a ceramic pre-product using laser cutting technology. This article introduces the concept of the flat slide valve for a proportional 4/3-way valve. The design of the valve, including the design of the metallic main stage is presented. This includes the design of the flow channels, which have to be suitable for ceramic materials. Furthermore the design of the actuator and hydraulic circuit for testing is presented. With the shown design, the function of a 4/3-way valve, known from piston spool valves, can be implemented with a linear behavior between slide plate deflection and opening flow cross section.
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Kartmann, Sabrina [Verfasser], and Roland [Akademischer Betreuer] Zengerle. "Normally-closed dispensing valve and in-line pressure and flow sensor fabricated in low-cost polymer technology." Freiburg : Universität, 2021. http://d-nb.info/1237617987/34.
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Nyawo, Talent. "Design of a rotary valve for pressurised steam." Thesis, KTH, Maskinkonstruktion (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192859.
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Denna rapport är gjord på ett examensarbete som var utfört på uppdrag av det svenska företaget Ranotor AB. Syftet var att utveckla en konceptuell lösning för en rotationsventil som skall fungera i en miljö med hög temperatur och högt tryck. Ventilen skall arbeta under höga rotationshastigheter, vilket kräver korta öppettider.Tekniska hjälpmedel såsom SolidWorks, ANSYS och MATLAB användes för att modellera och analysera de konceptuella lösningarna. Slutlösningen valdes från ett flertal olika koncept, varpå detta vidareutvecklades och optimerades. Betydande material och gastätningslösningar identifierades och utvärderades för att hitta den bästa lösningen. Optimering av individuella komponenter och hela anordningen gjordes med avseende på spänning, termisk- och dynamisk analys. De givna specifikationerna uppfylldes och resultaten var tillfredsställande. Resultaten ger en teoretisk bas för vidareutveckling och applicering av en rotationsventil in en miljö med hög temperatur och högt tryck.This Master thesis is a project commissioned by the Swedish company Ranotor AB. The objective of this thesis is to develop a conceptual solution for a rotary valve mechanism that has to work efficiently in a high-temperature and high-pressure environment. The valve is to operate at high rotational speeds which calls for very short opening time.Modern engineering tools namely Solidworks, Ansys and Matlab, were employed for modelling and analysis of the conceptual solution.The best design solution was selected from three developed concepts, and the selected concept was further developed and optimized. Major material candidates and gas-tight sealing solution were identified and evaluated and the optimal material and seal design was chosen. Optimization of the individual components as well as the whole assembly was performed based on stress, thermal and dynamic analysis. The given design specifications and functions were fulfilled and the results were satisfactory. The obtained results provide a theoretical foundation for the development and application of a rotary valve in high-temperature and high-pressure environment.
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Taylor, David Donald James. "Reducing booster-pump-induced contaminant intrusion in Indian water systems with a self-actuated, back-pressure regulating valve." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92062.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 151-155).
Intermittently-operated water systems struggle to equitably and effectively distribute clean water to customers. One common customer response to intermittency is to supplement the water system's pressure by using a household, or residential, booster pump. When such booster pumps are directly connected to the water utility's supply pipe, without an underground isolation tank (sump), they often induce negative pressure in the supply pipe which increases the flow rate. Unfortunately, where leakage rates are high, this negative pressure also increases the risk of contaminant intrusion. This thesis presents the iterative design and field testing of a patent-pending, full-bore, back-pressure regulating valve. The valve's simple mechanism relies on a stabilized collapsing tube, or 'Starling Resistor,'which when installed at a customer's connection, controls the flow rate and prevents booster pumps from creating negative pressure in the supply pipe. In collaboration with the Delhi Jal Board and several private partners, the valve's performance was verified in two rounds of field trials in neighborhoods of New Delhi, India including Pitampura, Azad Market, Vivek Vihar, Malvia Nagar, and Vasant Vihar. Using a crossover study, the valve was found to reduce the total contamination risk across all 19 tested houses during supply times by a median of 80%. The valve prevented 96% of pressure below -1 meter and an average of 53 minutes per day, per connection of total negative pressure. In an estimated worst-case scenario for contaminant intrusion, the presence of the valve reduced the contamination risk by two orders of magnitude at six customer connections - enough to correspond to significant reductions in health risks.
by David Donald James Taylor.
S.M.
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Anim, Kwaku. "Design, Development, Testing, and Evaluation of a Prosthetic Venous Valve." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1269252194.
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Erhard, Michael, Jörg Schneider, and Jan Julius Stein. "Design and performance evaluation of next generation clutch control valve." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71223.
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Pressure reducing valves perform various control tasks in mobile machines. In many cases contamination sensitive environments require pilot-operated valves, because of its more robust performance. On the other hand, dynamic valve behavior can be critically in certain applications. Overcoming the restrictions resulting from stand-alone test rig attempts, suitable simulation principles are nowadays the state of art in valve design. Unsuitable model approaches and missing consideration of the application may result in wrong design decisions. This paper discusses two important modeling issues, in particular the solenoid and spool leakage behavior, in combination with the connected system under control, a pressure-actuated clutch. It is shown, that even for standard proportional valves a critical view on customers´excitation strategy and site of installation decides on success or failure of an already used design variant.
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Yildiz, Evren. "Evaluation Of Performance And Optimum Valve Settings For Pressure Management Using Forecasted Daily Demand Curves By Artificial Neural Networks." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613600/index.pdf.
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For the appropriate operation and correct short term planning, daily demand curve (DDC) of municipal water distribution networks should be forecasted beforehand. For that purpose, artificial neural networks (ANN) is used as a new method. The proposed approach employs already recorded DDCs extracted from the database of ASKI (Ankara Water Authority) SCADA center and related independent parameters such as temperature and relative humidity obtained from DMI (State Meteorological Institute). In this study, a computer model was developed in order to forecast hourly DDCs using Matlab and related modules.
Parameters that affect the consumption of the water were determined as temperature, relative humidity, human behavior (weekend or workday) and season. Randomly selected days were taken into account for performance of the ANN model. Forecasted DDC values were compared with recorded data and consequently the model gives relatively satisfactory results, an average of 75% match according to R2 values for Ankara N8-3 network. Same architecture was applied for Antalya network give better results, average of 85%. For planning purposestotal volume and peak water consumption values for the selected recorded days, the day before recorded days, ANN forecasted days and seasonal average was compared and seasonal average gave relatively better results. Using the forecasted DDC, (i) performance analysis of the pressure zone and (ii) optimum valve setting evaluation for pressure management were realized. The results of the study may help water utilities for short term planning of a water distribution network, rehabilitation of elements, taking counter measures and setting the valve openings for minimizing leakage and optimizing customer conformity of the distribution network.
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THOMAS, VINEET SUNNY. "A Multiscale Framework to Analyze Tricuspid Valve Biomechanics." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542255754172363.
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Kolář, Milan. "Návrh tvářecího nástroje a zařízení k vystřižení podložky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229095.
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The Diploma Thesis presents a draft of designated automatic apparatus for cutting out and assembling pads for pressure control valve (DRV2). The theoretical chapter of the Thesis contains selected findings from theory and technology for material cutting. The next chapter contains design solutions for a designated apparatus for cutting and assembling pressure control valves. The pads are etched from 0,08 mm steel plates X2CrNi Mol7-12-2. The shape of the pads is etched on a 35mm-wide belt that is wound up onto a drum. The draft of this new technological facility has been elaborated in accordance with the most suitable technological variant. The cutting tool is made of steel 19 437 that is thermally processed at HRC 62-4. Estimated annual volume of production series is 2 mil. pcs. The cutting and assembly processes are executed with the aid of this designated automatic apparatus.
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Teien, Dag. "Assessment of aortic stenosis with special reference to Doppler ultrasound." Doctoral thesis, Umeå universitet, Klinisk fysiologi, 1986. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-103813.
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Mastaler, Alexandre. "Elementos de suporte do comando de valvulas avaliado por modelo de diferenças finitas." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/262884.
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Orientador: Katia Maria Lucchesi CavalcaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-04T03:12:40Z (GMT). No. of bitstreams: 1 Mastaler_Alexandre_M.pdf: 8070977 bytes, checksum: 67729451cedeb65f0b15eb1a17a3fead (MD5) Previous issue date: 2004
Resumo: O comando de válvulas é um sistema utilizado em motores à combustão, que tem como função controlar a abertura e fechamento de válvulas de circulação dos gases envolvidos na combustão. Ele é composto por diversos subsistemas; Um desses subsistemas é o contato balancim/pivô, onde o comando aciona o balancim para que esse acione a válvula e utilize o pivô como elemento de suporte. O conhecimento desse subsistema é importante para a avaliação de desgastes e ruídos provenientes desse contato, assim como, avaliações do atrito para otimização geral do comando. Para que haja a redução de desgaste, o pivô deve girar em relação ao balancim, mas existem certas aplicações em que o giro do pivô não é possível. Baseando-se na equação de Reynolds, o filme de óleo ao redor do pivô será avaliado e calculado com relação à distribuição de pressão. Com o conhecimento da distribuição de pressão, poderemos saber quais as forças envolvidas no subsistema. Considerando-se o atrito e os momentos gerados pelo balancim no pivô, chegamos às condições de equilíbrio do sistema. Com essas avaliações observaremos as condições que permitam a rotação do pivô em relação ao balancim
Abstract: The Valve Train System used in combustion engines have the ability to command the opening and closure of gas circulation valves control that takes part in combustion. It is formed by many sub-systems. One of these systems is the finger follower/pivot contact, where the command starts the finger follower for valve starts and uses the pivot as a support element. The knowledge of this sub-system is important to ware and noise evaluation that came ftom this contact, as well as, ftiction evaluation for the command general optimization. To reduce wear, the pivot must turn in finger follower relation, but in some applications the pivot tum is not possible. The oil film around the pivot is ca1culated in relation of its pressure distribution as Reynolds Equation. Through the knowledge of pressure distribution, the forces in the sub-system are known. Considering the ftiction and the moments generated by the balancing in the pivot, we carne to balance conditions in the system. With these evaluations we noticed the condition that allows the pivot rotation in relation to the balancing
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Abuhaiba, Mohammad. "Mathematical Modeling and Analysis of a Variable Displacement Hydraulic Bent Axis Pump Linked to High Pressure and Low Pressure Accumulators." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1240528916.
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Dissertation (Ph.D.)--University of Toledo, 2009.Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy degree in Mechanical Engineering." Bibliography: leaves 203-209.
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Konduri, Suchitra. "The Influence of normal physiological forces on porcine aortic heart valves in a sterile ex-vivo pulsatile organ culture system." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-03042005-135623/unrestricted/konduri%5Fsuchitra%5F200505%5Fmast.pdf.
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Thesis (M. S.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2005.Dr. Athanassios Sambanis, Committee Member ; Dr. Timothy M. Wick, Committee Member ; Dr. Ajit P.Yoganathan, Committee Chair. Includes bibliographical references.
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Arizcun, Zúñiga Paula María. "Ram pump hydraulic air test. Pressure conditions and flow measurements: Experimental research and case study." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-26897.
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This study consists of the development of a ram pump, which will allow the pumping of water without the need of external energy sources. It is considered an analysis of interest since, once it is finished; it can be applied in reality improving and facilitating different activities related to agriculture and health. Previous studies have been made related to the ram pump; however, in this case, it is intended to understand the system that has been built in the laboratory in order to find the best combination of parameters that will lead to obtain the highest possible efficiency. The study will be carried out by studying scientific literature and by experimenting in the laboratory. Encompassing the experimental and literary field, it is expected to understand perfectly the advantages and disadvantages of the ram pump in order to determine if it is worth it to install in certain places. After the study, the most favourable parameters for the operation of the Bruzaholms Bruk pump have been obtained. It has been found that the use of a longer drive pipe favours the operation of the system, as it is possible to obtain a higher efficiency, although it must be taken into account that the mentioned length needs to be controlled, as it could reduce the working rhythm of the pump. It has also been seen that the pump gives better results if the impulse valve is completely opened. Finally, it has been proven that, as long as the height difference between the two tanks is enough, increasing the height of the water source will favour the operation of the system.
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Schmidt, Hein. "The design of a pressure vessel and testing procedures for the determination of the effect of high temperature pressurised helim on valve contact welding / Hein Schmidt." Thesis, North-West University, 2004. http://hdl.handle.net/10394/500.
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The PBMR (Pebble Bed Modular Reactor) is one of the current developments in the field of
nuclear power generators. The control philosophy of the PBMR system relies heavily on the
controlling of valves. The current control valves are subjected to a maximum temperature of
350°C with a pressure difference of 90 bar. Control optimisation can be obtained by including
'hot valves" into the system. The biggest improvement is possible with a bypass-valve after
the low-pressure turbine outlet. This valve will be subjected to a temperature of 720°C with a
pressure difference of 52 bar. PBMR personnel raised the concern that the components of
these valves (valve seat and sealing surfaces) in contact with the hot helium gas could tend to
weld to each other when they are in contact. An investigation was done to establish whether
these surfaces tend to weld together.
As no literature was found on testing for prevention of welding of materials under high
temperature pressurised helium conditions (Chapter 2), a testing facility was designed to test
the hot bypass-valve material (AISI H10) under operating conditions. This included the
design of a pressure vessel according to ASME Vlll Division 1 (Chapter 3) to be able to
simulate the helium operating conditions and a bolted connection (Chapter 4) to simulate the
valve contact conditions.
A finite element analysis was done, using ALGOR FEMPRO software (Chapter 5), to verify
the internal stresses of the pressure vessel based on the maximum allowable stresses for
material UNS NO6230 (Haynes® 230© Alloy), from Appendix 4 of ASME Vlll Division 2.
Firstly, a steady state heat transfer analysis was done to calculate the pressure vessel
temperature distribution. During a static stress analysis, these results were used to assign
the temperature dependent material properties to the various finite element elements. The
helium pressure and external pressure were simulated as uniform surface pressures. Based
on the Tresca effective stress results the maximum allowable 0.2% yield strength of Haynes
230 was exceeded. According to this analysis, the pressure vessel will yield when subjected
to the specified operating conditions. The calculated stresses also exceeded the ASME Vlll
Division 2 - Appendix 4 maximum allowable material stresses.
It is recommended that the same analysis be done with another FEM analysis software
package, to verify the calculated material stresses. This analysis should be incorporated into
the follow-up study, where the water-cooling system must also be designed. Before the
manufacturing of the pressure vessel can commence, a third party inspector must approve
the design. Any design updates necessary from the inspector's report should also be
included in the follow-up study.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2005.
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Real, Marcelo Alexandre. "Desenvolvimento de técnica de medição e obtenção de dados experimentais envolvidos no ciclo de trabalho dos compressores herméticos alternativos." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-18122015-110225/.
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Essa dissertação desenvolve e faz uso de uma técnica de medição com objetivo de obter dados experimentais envolvidos no ciclo de trabalho dos compressores herméticos alternativos, largamente utilizados nos sistemas de refrigeração. O trabalho mostra o comportamento das válvulas de admissão e descarga durante o funcionamento do compressor, as pressões no cilindro, na sucção, na descarga e também a variação de rotação do eixo durante um ciclo de compressão completo. Todas as características mensuradas estão referenciadas à posição angular do eixo do compressor, o que permitiu monitorar todos os eventos em função do seu deslocamento angular. Para o desenvolvimento desse trabalho foi necessário planejar um sistema de medição robusto, não vulnerável aos fatores ambientais, presentes dentro da carcaça do compressor. A limitação do espaço físico foi um fator de grande importância na escolha dos sensores, assim como a velocidade de resposta dos instrumentos, pois um ciclo de compressão tem período menor que 0,020 segundos. A coleta dos dados e a análise dos sinais foram realizadas com o auxilio de hardware apropriado e software especialmente desenvolvido.In this dissertation it is developed and applied measurement methods to obtain experimental data of a hermetic compressor work cycle, widely used in the refrigeration systems. This work shows the suction and discharge valve behaviors, the pressure in the cylinder, as well as in the discharge and suction chambers, and also crankshaft rotation variation during a complete compression cycle. All the measurements are reference to crankshaft angular position of compressor which allows to verify the events as a function of the crankshaft angular displacement. For the development of this work it was necessary to plan a reliability measure system, not affected by environmental factors inside the housing of compressor. The inner space limitation was an important feature for choosing the sensors as well as their time response, since the period compression cycle is less than 0.020 seconds. The data acquisition and signal analysis were done with appropriate hardware and it was developed a specific software.
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Macsek, Tomáš. "Vyhodnocení provozu tlakové kanalizace obce Hrádek u Sušice." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227546.
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The thesis deals with the assessment of a low pressure sewer system (LPS) in the village of Hrádek u Sušice during its test operation. It assesses the functionality of the LPS, parameters of operation and lists types of failures, which were found during the test operation, as well as the causes for the failings. For the purpose of determination of the LPS functionality and causes of failures, continual measurements of pressure have been made on selected sites followed by a thorough analysis of the data.
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Umlauf, Martin. "Vliv teplotních šoků na únavu materiálu částí tlakových zařízení." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241226.
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This thesis examines influence of thermal shock on fatigue of pressure equipment components. The paper relates to project of IMI CCI Brno, which is a leading manufacturer of valves for the energy and process industries. Analysis concerns the impact of thermal shock concentrating on high pressure part of the steam valve. And proposal for a new valve geometry that reduces machining operations and reduce financial costs of production. First part of the thesis presents a basic review of fatigue damage components concerning mechanical loading and thermal – mechanical loading. Second part of the study creates FEM model of the valve. FEM model simulate temperature field and stress during thermal shock. Influence of thermal shock to fatigue damage was computed on basis of stress tensor obtained from FEM simulation under Chapter 18 of the standard EN 13445-3. Existing valve geometry was verified and the new geometry was proposed that simplified and reduce financial costs of production.
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Battiston, Cristiane Collet. "Análise da dinâmica do escoamento a jusante de comporta de controle de vazão em aqueduto de eclusa de navegação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/107918.
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As Diretrizes da Política Nacional de Transporte Hidroviário apresentam metas ambiciosas para os próximos anos quanto à construção de eclusas e ao aumento da participação do transporte aquaviário de carga na matriz brasileira. A bibliografia expõe que os custos são otimizados quando um desnível é transposto com a construção do menor número eclusas, o que resulta na busca pela transposição de desníveis significativos com a execução de eclusas com uma única câmara. No entanto, problemas hidráulicos encontrados junto às comportas de enchimento e esvaziamento estão entre as principais limitações para o aumento da altura de queda das eclusas. Os diferenciais de pressão entre as faces de montante e jusante das comportas e a variação do seu grau de abertura durante as operações de enchimento e esvaziamento de eclusas de navegação de média e alta queda geram escoamentos turbulentos, com velocidades e pressões capazes de produzir danos às estruturas. Com o objetivo de analisar os parâmetros hidráulicos do escoamento médio a jusante de comportas dos sistemas de enchimento e esgotamento de eclusas, do tipo segmento invertida, e as pressões instantâneas ao longo do teto e da base do conduto, de forma a identificar e caracterizar padrões de comportamento que auxiliem na elaboração de projetos e no aperfeiçoamento dessas estruturas, foram conduzidas duas investigações complementares, a experimental e a numérica. A investigação experimental, desenvolvida no Laboratório de Obras Hidráulicas do Instituto de Pesquisas Hidráulicas da Universidade Federal do Rio Grande do Sul, proporcionou a geração de dados discretos de pressão instantânea ao longo do teto e da base do conduto para 53 condições de abertura e vazão, para escoamento em regime permanente. A investigação numérica, realizada com o software Flow-3D®, de Dinâmica de Fluidos Computacional, viabilizou a geração de dados do escoamento médio no interior do conduto para 12 condições de abertura e vazão, que reproduziam as simulações experimentais. Os resultados das simulações realizadas no Flow-3D® com modelo de turbulência k- e demonstraram a sua aplicabilidade no estudo do escoamento médio a jusante de comportas de sistemas de enchimento e esvaziamento de eclusas. O modelo numérico reproduziu os dados experimentais de pressão a montante da comporta e os formatos das curvas de pressão ao longo da base e do teto do conduto a jusante da comporta, apresentando resultados mais aderentes para a base. Para as condições operacionais com a comporta parcialmente aberta, as menores pressões ocorreram no teto do conduto próximo à comporta, região de recirculação do escoamento, e junto ao terminal da comporta. A partir da análise dos dados foi possível a caracterização do comportamento das pressões médias, das flutuações de pressão e das pressões máximas e mínimas ao longo da base e do teto do conduto por meio da relação entre coeficientes adimensionais de posição e de pressão.Brazilian Waterways Policy has ambitious goals for constructing navigation locks and increasing the participation of the cargo transport through waterways in the national transport matrix. Literature states that costs are optimized by the construction of fewer locks for the transposition of water levels by vessels, which results in the search for transposition of significant lifts by using navigation locks with single camera. However, the hydraulic problems in the filling and emptying systems, especially close to the valves, are among the major limitations to increase the lock lift. During filling and emptying operations of medium and high-lift locks, the pressure difference between upstream and downstream sides of lock valve and its opening generate turbulent flows with associated flow velocities and pressures capable of damaging the structures. In the current research, experimental and numerical investigations were conducted in order to analyze the mean flow through lock culvert valves and the instantaneous pressures behavior along the culvert roof and base, and to identify and to characterize hydraulic parameters which could be useful for project development and improvement of these structures. The experimental research was conducted at the “Laboratório de Obras Hidráulicas” of the “Instituto de Pesquisas Hidráulicas” of the “Universidade Federal do Rio Grande do Sul” and provided the generation of discrete data of instantaneous pressure along the culvert roof and base for 53 conditions of flow and valve opening. Experimental simulations were performed with steady state flow. Numerical investigation applied the Computational Fluid Dynamics software Flow-3D® and produced information for the mean flow inside the culvert for 12 valve opening and flow conditions, which reproduced the experimental simulations. valve opening and flow conditions, which reproduced the experimental simulations. The numerical results, obtained by using the k-e turbulence model, demonstrated the applicability of Flow-3D® in the study of the mean flow downstream of lock culvert valves. The numerical model was able to reproduce the experimental data of pressure along the culvert base and roof presenting more accuracy to base data. For partially open gate conditions, the lowest pressures were verified next to the valve lip and at the downstream culvert roof close to the valve, which correspond to the recirculating flow region. From data analysis it was possible to characterize the behavior of the mean pressure, pressure fluctuations and extreme pressures along the culvert base and roof by the relationship between dimensionless coefficients of position and pressure.
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Khaji, Zahra. "Extending Microsystems to Very High Temperatures and Chemically Harsh Environments." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302658.
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Aiming at applications in space exploration as well as for monitoring natural hazards, this thesis focuses on understanding and overcoming the challenges of extending the applicability of microsystems to temperatures above 600°C as well as chemically harsh environments. Alumina and zirconia high-temperature co-fired ceramics (HTCC) with platinum as the conductor material, have in this thesis, been used to manufacture a wide range of high-temperature tolerant miniaturized sensors and actuators, including pressure and flow sensors, valves, a combustor, and liquid monopropellant microthrusters. Interfacing for high temperatures is challenging. One solution is to transfer the signal wirelessly. Here, therefor, wireless pressure sensors have been developed and characterized up to 1000°C. It is usually unwanted that material properties change with temperature, but by using smart designs, such changes can be exploited to sense physical properties as in the gas flow sensor presented, where the temperature-dependent electrical conductivity of zirconia has been utilized. In the same manner, various properties of platinum have been exploited to make temperature sensors, heaters and catalytic beds. By in-situ electroplating metals after sintering, even more capabilities were added, since many metals that do not tolerate HTCC processing can be added for additional functionality. An electroplated copper layer that was oxidized and used as an oxygen source in an alumina combustor intended for burning organic samples prior to sample analysis in a lab on a chip system, and a silver layer used as a catalyst in order to decompose hydrogen peroxide in a microthuster for spacecraft attitude control, are both examples that have been explored here. Ceramics are both high-temperature tolerant and chemically resistant, making them suitable for both thrusters and combustors. The corresponding applications benefit from miniaturization of them in terms of decreased mass, power consumption, integration potential, and reduced sample waste. Integrating many functions using as few materials as possible, is important when it comes to microsystems for harsh environments. This thesis has shown the high potential of co-fired ceramics in manufacturing microsystems for aggressive environments. However, interfacing is yet a major challenge to overcome.
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Hrouzková, Andrea. "Optimalizace výrobní a montážní technologie ventilového čepu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229205.
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The thesis aimed to study the impact of manufacturing and assembly technology, the valve bolt fitted to diesel high pressure pump CP3 in the Bosch, which has been found to leak. As experimental material was chosen heat treated bolts M16x1,5 made of material 12 050th. Groups of samples were produced in two ranges hardness. Experimental determination of the optimum range of hardness was assessed on the basis of the results of the process of the screw and set the value of plastic deformation of the sealing surfaces of the parts. Experimental section also deals with the analysis of bearing surfaces on the pump and the components, after the screw process. To some extent, is observed as surface treatment
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Lim, C. S. "Plastic limit pressures for pressure vessels with defects at openings." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234339.
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Hájek, Daniel. "Zvýšení pružnosti zážehového motoru přeplňováním." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228975.
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The master’s thesis deals with the question of petrol engine boosting by rotary turbochargers. The objective of the thesis is to project suitable turbocharger for defined single-cylinder petrol engine. After selecting the suitable turbocharger type it will follow the construction of the computational model of the single-cylinder turbocharged petrol engine in the Lotus Engine Simulation software. In the computational model is boost pressure regulated by the turbine waste gate valve. The result will be the boost pressure values scheme for the highest possible torque so that the maximum combustion pressures will not exceed the value of 9,5 MPa. There are summarized findings and results in the conclusion of the thesis.
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Pavlík, Václav. "Dynamická charakteristika zpětné armatury." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-240979.
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This master´s thesis provides an overview of all designs of check valves, their usage and typical features. Main purpose of this work is to clear up the phenomenon of check valve slam and the other problems that occur during transients. The check valve slam was measured at the test rig in the hydraulic laboratory. For unsteady flow evaluation after pump shut down was used Gibson method. The dynamic characteristic was possible to create by results from this method. It was achieved without impact of the speed of sound in the fluid. This work also contains 2D transient CFD calculations, which was used for evaluation of the hydrodynamic torque acting on the hinge pin. This approach provides an option to calculate wide range of cases at the expense of not entirely exact geometry. The main contribution of the theoretical study at the beginning of this thesis is its entireness. It might give an important clue when right valve is selecting. For good choice of valve might be helpful to use dynamic characteristics in this thesis presented. Mentioned characteristics were created by new way and its background is in measurements and simplified CFD calculations.
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Cheade, Eduardo de Lima. "Atualização de sistema duplicador de pulsos para teste de proteses de valvulas cardiacas." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258952.
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Orientador: Eduardo Tavares CostaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: A utilização de próteses de válvulas cardíacas tanto mecânicas quanto biológicas tem se tornado cada vez mais freqüente. Estas próteses devem ser avaliadas (testes in-vitro e in-vivo) para que sejam utilizadas clinicamente. Os testes de desempenho hidrodinâmico são realizados in vitro, e a análise dos resultados é importante para a classificação e caracterização de uma determinada prótese, sendo atualmente um dos requisitos obrigatórios exigido por órgãos reguladores para a aprovação de próteses a serem empregadas clinicamente. Os testes de desempenho hidrodinâmico são realizados por sistemas complexos, denominados duplicadores de pulso, cuja finalidade é reproduzir o comportamento hidrodinâmico do coração e simular as variáveis fisiológicas às quais as válvulas são normalmente submetidas em condições reais. Neste trabalho foi desenvolvido, para uso na empresa Braile Biomédica, utilizando a plataforma de programação LabVIEW®, um programa capaz de fazer a aquisição e interpretação dos sinais de fluxo e pressão provenientes de transdutores específicos, bem como a realização dos cálculos necessários e a geração de um relatório resultante do teste. Também foram desenvolvidos circuitos condicionadores de sinais para os transdutores de pressão e fluxo inerentes ao sistema duplicador de pulso existente na empresa. A partir das medidas e dos gráficos de pressão e fluxo é possível calcular os seguintes parâmetros: área específica do orifício, coeficiente de descarga, fração de regurgitação e índices de performance e eficiência da válvula.
Abstract: It has become very frequent the use of mechanic or biological cardiac valve prostheses. These prostheses must be evaluated (in vitro and in vivo tests) in order to be used clinically. The hydrodynamic performance tests are carried out in vitro. The analyses of the test results are very important for the characterizations and classification of a given prosthesis, being one of mandatory requirements of the regulatory organs in order to approve its clinical use. The hydrodynamic performance tests are carried out by complex systems often called pulse duplicators, which must reproduce the heart hydrodynamic behaviour and simulate the physiological variables that the cardiac valves are submitted in real conditions. In this work it has been developed a software program to be used at Braile Biomedica based on the LabVIEW® platform, capable of acquiring and processing flux and pressure signals from specific transducers, as well as all the necessary calculi and generation of the test results report. It has also been developed the signal conditioning circuits for the pressure and flux transducers inherent to the company pulse duplicator. The following parameters are calculated and reported with several graphics showing flux and pressure signals: orifice specific area, discharge coefficient, regurgitation fraction and valve performance and efficiency indices.
Mestrado
Engenharia Biomedica
Mestre em Engenharia Elétrica
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Wang, Yue. "Numerical Studies of Flow and AssociatedLosses in the Exhaust Port of a Diesel Engine." Doctoral thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-134844.
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In the last decades, the focus of internal combustion engine development has moved towards more efficient and less pollutant engines. In a Diesel engine, approximately 30-40% of the energy provided by combustion is lost through the exhaust gases. The exhaust gases are hot and therefore rich of energy. Some of this energy can be recovered by recycling the exhaust gases into turbocharger. However, the energy losses in the exhaust port are highly undesired and the mechanisms driving the total pressure losses in the exhaust manifold not fully understood. Moreover, the efficiency of the turbine is highly dependent on the upstream flow conditions. Thus, a numerical study of the flow in the exhaust port geometry of a Scania heavy-duty Diesel engine is carried out mainly by using the Large Eddy Simulation (LES) approach. The purpose is to characterize the flow in the exhaust port, analyze and identify the sources of the total pressure losses. Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation results are included for comparison purposes. The calculations are performed with fixed valve and stationary boundary conditions for which experimental data are available. The simulations include a verification study of the solver using different grid resolutions and different valve lift states. The calculated numerical data are compared to existent measured pressure loss data. The results show that even global parameters like total pressure losses are predicted better by LES than by URANS. The complex three-dimensional flow structures generated in the flow field are qualitatively assessed through visualization and analyzed by statistical means. The near valve region is a major source of losses. Due to the presence of the valve, an annular, jet-like flow structure is formed where the high-velocity flow follows the valve stem into the port. Flow separation occurs immediately downstream of the valve seat on the walls of the port and also on the surface of the valve body. Strong longitudinal, non-stationary secondary flow structures (i.e. in the plane normal to the main flow direction) are observed in the exhaust manifold. Such structures can degrade the efficiency of a possible turbine of a turbocharger located downstream on the exhaust manifold. The effect of the valve and piston motion has also been studied by the Large Eddy Simulation (LES) approach. Within the exhaust process, the valves open while the piston continues moving in the combustion chamber. This process is often analyzed modeling the piston and valves at fixed locations, but conserving the total mass flow. Using advanced methods, this process can be simulated numerically in a more accurate manner. Based on LES data, the discharge coefficients are calculated following the strict definition. The results show that the discharge coefficient can be overestimated (about 20 %) when using simplified experiments, e. g. flow bench. Simple cases using fixed positions for valve and piston are contrasted with cases which consider the motion of piston and/or valves. The overall flow characteristics are compared within the cases. The comparison shows it is impossible to rebuild the dynamic flow field with the simplification with fixed valves. It is better to employ LES to simulate the dynamic flow and associated losses with valve and piston motion.QC 20131204
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Bento, Andre Moreira. "Efeitos hemodinâmicos da ventilação não invasiva com pressão positiva em pacientes com estenose mitral sintomática." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-02062008-093115/.
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Introdução: O uso de pressão positiva contínua em vias aéreas (CPAP) causa modificações hemodinâmicas favoráveis em pacientes com insuficiência cardíaca. Na presença de disfunção ventricular esquerda, mecanismos hemodinâmicos propostos associam seu uso ao aumento do débito cardíaco, através da redução do enchimento e da pressão transmural do ventrículo esquerdo. Estes efeitos talvez colaborem para o sucesso dessa terapia em pacientes com congestão pulmonar. Entretanto, até onde extensa revisão bibliográfica nos permite afirmar, não foram estudados os efeitos hemodinâmicos do CPAP em pacientes com estenose mitral, etiologia comum de congestão pulmonar em alguns países em desenvolvimento. Objetivos: Avaliar a resposta hemodinâmica dos pacientes portadores de estenose mitral sintomática durante o uso de CPAP. Métodos: Foram incluídos quarenta pacientes portadores de estenose mitral. Os critérios de exclusão foram: presença de disfunção ventricular esquerda, de outra valvopatia de grau moderado ou importante, de trombo intracavitário ao ecodopplercardiograma e de doença pulmonar obstrutiva crônica. Os pacientes foram avaliados em 3 condições diferentes: 1. condição basal, realizada ar ambiente; 2. uso de CPAP 7 cm H2O e 3. uso de CPAP 14 cm H2O. Foi realizada a medida de pressão arterial invasiva (aorta) e utilizado cateter de artéria pulmonar para a medida da pressão arterial pulmonar e débito cardíaco. Foram coletas amostras de gasometria arterial e venosa central. A variação percentual do volume sistólico (deltaVS) foi calculada tendo o valor na condição basal como 100% e foi correlacionada com as características clínicas, ecodopplercardiográficas, hemodinâmicas e gasométricas da condição basal. Os pacientes foram classificados em 3 grupos: grupo I - deltaVS <= -10%, grupo II - deltaVS entre -9,9% e +9,9% e grupo III - deltaVS >= +10%. Resultados: Durante a aplicação do CPAP, freqüência cardíaca, pressão arterial sistêmica e pressão arterial pulmonar não variaram significativamente. Na segunda condição, a deltaVS se correlacionou com a pressão arterial pulmonar diastólica e média, pressão de oclusão de capilar pulmonar e gradiente transvalvar mitral ao cateterismo. A análise dos grupos não identificou qualquer variável capaz de distingui-los. No uso de CPAP 14cmH2O, a deltaVS se correlacionou positivamente com a classe funcional, pressão sistólica do ventrículo direito (ao ecodopplercardiograma), freqüência cardíaca, pressão arterial sistêmica sistólica, pressão arterial pulmonar sistólica, diastólica e média, pressão de oclusão da artéria pulmonar e gradiente transvalvar mitral ao cateterismo. Além disso, nesta condição, a deltaVS se correlacionou inversamente com o volume sistólico indexado e saturação venosa de oxigênio. A análise comparativa dos grupos evidenciou, no grupo III, valores significativamente superiores de pressão sistólica do ventrículo direito (ao ecodopplercardiograma), pressão arterial pulmonar sistólica, diastólica e média, pressão de oclusão da artéria pulmonar e gradiente transvalvar mitral ao cateterismo. Não houve variável capaz de distinguir o grupo I do II. Conclusão: O uso de CPAP aumentou o volume sistólico nos pacientes com estenose mitral de maior impacto clínico e hemodinâmico, caracterizados por maior limitação funcional, hipertensão pulmonar e gradiente transvalvar mitral e menor saturação venosa de oxigênio e volume sistólico indexado.Background: Continuous positive airway pressure (CPAP) impacts hemodynamic changes in heart failure patients by impending cardiac filling and reduces cardiac afterload by reducing left ventricular transmural pressure. These effects may collaborate for the success of this therapy in patients with pulmonary congestion. However, to your knowledge, no study has evaluated the hemodymanic effects of CPAP in patients with mitral stenosis, which is a common etiology of pulmonary congestion in some developing countries. Objectives: analyze the effects of CPAP on hemodynamic parameters in patients with symptomatic mitral stenosis. Methods: Forty patients with symptomatic mitral stenosis were included. They were monitored by aorta pressure and the insertion of a pulmonary artery catheter. Hemodynamic and gasometrical data were collected in each study period. Patients were evaluated in three study periods. Baseline condition was during spontaneous breathing. We applied CPAP 7 cm H2O in the second period and 14 cm H2O in the last period of the study. Were excluded patients with left ventricular systolic dysfunction, other valvopathy more than mild, and left atrial thrombi assessed by echocardiography and patients with history or symptom of chronic obstructive pulmonary disease. Percentage changes of stroke volume (deltaSV) were calculated with the values at baseline set as 100% and were correlated to clinical, ecocardiographic, hemodynamic and gasometrical data (at baseline). Patients were classified in group I if deltaSV was <= -10%, group II if deltaSV was between -9,9% and +9,9% or group III if deltaSV >= +10%. Results: During CPAP use, heart rate, systemic blood pressure and pulmonary artery pressure did not significantly change. At CPAP 7 cmH2O, deltaSV correlated positively with baseline values of diastolic pulmonary artery pressure, pulmonary artery occlusion pressure and mean transmitral gradient. There was no variable capable to distinguish the groups. At CPAP 14 cmH2O, deltaSV correlated positively with functional class, pulmonary artery systolic pressure (measured by echocardiography), heart rate, systolic blood pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery occlusion pressure and mean transmitral gradient. Not only, at CPAP 14 cmH2O, deltaSV correlated inversely to indexed stroke volume and central venous saturation. Responders (group III) had superior pulmonary artery pressure (measured by echocardiography), systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery occlusion pressure and mean transmitral gradient. The comparison between groups I and II did not evidence any variable capable to distinguish them. Conclusion: CPAP improved stroke volume in those with mitral stenosis with greater clinical and hemodynamic impact, characterized by higher functional limitation, pulmonary hypertension and mean transmitral gradient and lower central venous saturation and indexed stroke volume.
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Štěpán, Tomáš. "Zařízení na zkoušení termoregulačních vlastností termostatických hlavic." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228088.
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This master's thesis is focused on the design of a device for testing the thermo-regulating properties of thermostatic heads. The engineering design, design of testing device has been composed according to the standard EN 215: Thermostatic radiator valves – Requirements and test methods. Based on these designs, sensors and regulation elements, which are suitable for testing, have been designed. Last part of the thesis deals with operating the device and measurement procedure.
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Rada, Jakub. "Návrh a optimalizace regulačního ventilu pro EHRS výměník." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232131.
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This diploma thesis deals with the design and optimization of the control valve for EHRS exchanger. The first part of the thesis contains a research describing the historical development of internal combustion engines, their impact on the environment and especially the possible ways of waste heat recovery. The second part focuses on the design of the control valve and experimental measurement to verify its functionality. The final part contains an analysis of pressure losses of the designed valve to improve its construction disadvantages.
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Castro, Roberto Chaves. ""Circulação periférica em pacientes com insuficiência aórtica crônica e indicação de troca valvar"." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-05092005-115223/.
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Introdução: O recente aperfeiçoamento da ultra-sonografia permitiu a análise estrutural e funcional do vaso. Casuística e Métodos: 36 pacientes com insuficiência aórtica e indicação de troca valvar, divididos em grupos com pressão arterial diastólica (PAD) superior e inferior a 50mmHg, avaliados antes e seis meses após a cirurgia. A função arterial compreendeu a complacência, distensibilidade e a função endotelial pela dilatação fluxo-mediada e nitrato-mediada. Conclusão: A complacência e a distensibilidade foram maiores no grupo com menor PAD e diminuíram após a cirurgia. A disfunção endotelial foi presente em insuficiência aórtica crônica independente do nível da pressão arterial diastólicaIntroduction: The recent improvement of ultrasonography made possible a functional and structural analysis of the vessel. Methods: 36 patients with aortic insufficiency and valve replacement need, divided in 2 groups with diastolic blood pressure (DBP) above and below 50mmHg. Checked twice: before and 6 months after surgery. The arterial function comprised compliance, distensibility and endothelial function through flow-mediated dilatation and nitrate-mediated dilatation. Conclusion: The compliance and distensibility were higher in the group with lower DBP and decreased after surgery. Endothelial dysfunction was present in chronic aortic insufficiency no matter the level of DBP