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Harrison, Adrian M. "Reduction of axial piston pump pressure ripple." Thesis, University of Bath, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760701.
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Davaanyam, Zorigtkhuu. "Piston press test procedures for predicting energy-size reduction of high pressure grinding rolls." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54154.
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High Pressure Grinding Rolls (HPGR) have been used for over 20 years, however the technology has not received wide industry acceptance despite reports of substantial energy advantages. One barrier is that full and fair consideration cannot be given to HPGR-based comminution circuits for early-stage mining projects, because industry standard tests require large sample sizes for evaluation of the technology.
The main objective of the research was to develop methodologies, requiring small sample quantities, to predict the energy–size reduction performance of HPGRs. A key outcome is the development of three piston press testing procedures that require significantly less sample than standard HPGR evaluation methods.
One method, referred to as the direct calibration methodology, involves calibrating results of piston press tests against pilot-scale HPGR tests. This methodology was developed primarily for situations where HPGR test data is only available for a composite sample and the energy requirements of individual geometallurgical units within a deposit are to be determined.
To address the case where HPGR test results are not available, a second method was developed which relies only on piston press testing and empirical equations that were determined from a database of pilot-scale HPGR results.
The simulation-based methodology was also developed to be able to assess the impact of changes in HPGR operation or circuit configuration on comminution performance. An existing energy–breakage model was adopted and modified for application to particle-bed comminution. The three methodologies were compared by applying them to samples from a copper-gold deposit in central British Columbia.
Through utilization of these methodologies, the energy–size reduction performance of the HPGR technology can be predicted with small sample requirements which can be applied to a broad range of ore types and provide a stronger statistical basis for the process design.
During development of the methodologies, significant research outcomes resulted. Controlled piston press and HPGR pilot tests on the same samples confirmed that normalized product PSDs of the respective equipment can be regarded as equivalent. Furthermore, data from particle-bed comminution tests was used to determine master curves describing breakage appearance functions for the compression mode of breakage.<br>Applied Science, Faculty of<br>Mining Engineering, Keevil Institute of<br>Graduate
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Giriat, Gaetan. "Instrumentation development for magnetic and structural studies under extremes of pressure and temperature." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/7931.
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The study of the magnetic and structural properties of matter under extreme conditions is a fast developing field. With the emergence of new techniques and innovative instruments for measuring physical properties, the need for compatible pressure generating devices is constantly growing. The work described in this thesis is focused on development, construction and testing of several high pressure (HP) cells of novel design. One of the cells is intended for single crystal X-ray diffraction (SXD) studies at low temperature (LT) and the other three HP devices are designed for a Magnetic Property Measurement System (MPMS), two of which are suitable for dc susceptibility studies and the other one is aimed at high frequency ac susceptibility measurements. HP crystallographic studies are routinely carried out in diamond anvil cells (DAC) at room temperature while ambient pressure SXD studies are often conducted at LT to reduce atomic vibrations and obtain more precise structural data as well as to study LT phases. Combining HP with LT gives access to a whole new area on the phase diagrams but due to the size of the existing DACs this is generally achieved by cooling down the cells inside a cryostat and it is mainly possible at synchrotrons where dedicated facilities exist. A miniature DAC which can be used with commercially available laboratory cry-flow cooling systems and achieves pressures in excess of 10 GPa has been developed. The design of the pressure cell is based on the turnbuckle principle and therefore it was called TX-DAC. Its dimensions have been minimised using Finite Element Analysis (FEA) and the final version of the cell weighs only 2.4 g. The cell is built around a pair of 600 μm culet Boehler-Almax anvils which have large conical openings for the diffracted beam. The TX-DAC is made of beryllium copper (BeCu) alloy which has good thermal conductivity and allows quick thermal equilibration of the cell. The MPMS from Quantum Design is the most popular instrument for studies of magnetic properties of materials. It is designed to measure ac and dc magnetic susceptibility of sample with detectable signals as low as 10-8 emu. The MPMS has a sample chamber bore of 9 mm in diameter and this puts a constraint on the dimensions of the pressure cells. However, several types of clamp piston-cylinder cells and DACs have been designed for the MPMS. The former are used for measurements at pressure up to 2 GPa and the later can be used for studies at higher pressure. Taking advantage of the turnbuckle principle, a DAC (TM-DAC) and a piston-cylinder cell (TM-PCC) for dc magnetic studies were built. They allow HP measurements to be performed at the full sensitivity of MPMS. Both pressure cells are made of BeCu and their small dimensions combined with symmetrical design is the key to an ideal background signal correction. The TM-DAC is 7 mm long and 7 mm in diameter, it weighs 1.5 g and with 800 μm culet anvils it can generate a sample pressure of 10 GPa. Inherently the sample volume is limited to approximately 10-3 mm3 and the signal corresponding to this volume of some weakly magnetic material remains below the sensitivity of the MPMS. This constraint led us to the development of the TM-PCC – a piston-cylinder variant of the turnbuckle design. With a 4 mm3 sample volume it allows the study of weakly magnetic samples in the range 0-1.9 GPa. The TM-PCC uses two zirconia pistons of 2.5 mm in diameter; it is 10 mm long, 7 mm in diameter and weights 2.7 g. Conventional metallic pressure cells perform well in dc mode however in ac susceptibility measurements, the Eddy currents set in the cells’ body lead to a screening effect which can significantly obscure the signal from the sample. This problem was solved by designing a composite piston-cylinder cell made with Zylon fibre and epoxy resin. The sample is located in the middle of the cell in the 2.5 mm bore and the pressure is transmitted through zirconia pistons. Keeping the metallic parts away from the sample resolves any interference issue. The composite cell performs well in a pressure range of 0-1 GPa. The performance of the pressure cells developed within this project is illustrated by studies of various systems at high pressure.
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Huang, Xiaochen, Bing Xu, and Junhui Zhang. "The influence of the swash plate oscillation on pressure ripple in variable displacement axial piston pump." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71101.
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The displacement of the variable displacement pumps can be adjusted by changing the swivel angle of the swash plate. In fact, the swivel angle oscillates because of the oscillating torque on the swash plate, which caused by the pressure fluctuation of the piston chamber. The swivel angle is most often considered as a constant value in previous studies. However, the oscillation of the swash plate leads to an additional movement of the piston, which has an impact on the pressure fluctuation and the flow ripple. In this study, an improved model of a self-supplied variable displacement pump is established. The swash plate oscillation under different operating conditions is presented. In order to investigate the effect of the swash plate oscillation on the pressure ripple, a comparison between the case of the fixed swash plate and the oscillated swash plate is conducted. Results show the pressure ripple with an oscillated swash plate shows a smaller pressure ripple. It also shows that the nine pistons and the control mechanism both affect the pressure ripple and flow fluctuation.
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Wongthep, Padipat. "Etude du régime d'écoulement du fluide dans le jeu d'un ensemble piston-cylindre en vue de l'optimisation du calcul du coefficient de déformation." Phd thesis, Paris, ENSAM, 2013. http://pastel.archives-ouvertes.fr/pastel-00918486.
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Les balances manométriques sont utilisées en métrologie des pressions statiques.Des projets européens tel qu'Euromet 463 ont mis en évidence des écarts systématiques entreles mesures expérimentales et les calculs des paramètres nécessaires à la caractérisation desbalances de référence. La vitesse de chute du piston est l'un d'eux pourtant essentiel dans laprocédure d'étalonnage. L'objectif des travaux de thèse est l'ajustement des méthodesd'estimation de cette vitesse de chute. Cela permettra d'améliorer la caractérisation du jeuinterne de la balance, de déterminer plus précisément la section effective de ce jeu et parconséquent d'améliorer l'incertitude portant sur le coefficient de déformation, paramètre clé del'étalonnage par comparaison. Jusqu'à présent le modèle de calcul de l'écoulement du fluidedans la balance était quasi unidimensionnel. Il assimilait le jeu entre le piston et le cylindre àdeux parois parallèles. Dans cette étude, les équations de l'écoulement du flu ide sont modifiéespour évaluer l'influence du modèle dans un jeu annulaire. Les corrections dues à la vitesse dechute du piston sont également prises en compte. Les calculs des déformations des structuressont réalisés en utilisant la méthode des éléments finis. Les travaux expérimentaux portent surdes ensembles piston-cylindre 50, 200 et 1000 MPa du Laboratoire National de Métrologie etd'Essais (LNE). Une confrontation calcul-expérience est réalisée en prenant en compte lesparamètres de variabilités tels que la géométrie ou les propriétés du fluide.
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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.<br>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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Elfridsson, Jon. "3D parameterized FEM modelling of a piston ring in a marine diesel engine : a simulation approch using FEM." Thesis, Umeå universitet, Institutionen för fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-38315.
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The piston ring in a marine two-stroke diesel engine operates in demanding conditions, involving high temperatures and pressures. Its main purposes are to seal the combustion chamber of the engine, minimize the frictional contact against the cylinder liner and transfer heat from the piston. The development of new piston ring designs for marine diesel engines is mainly based on engineering knowledge and expertise but is somewhat unstructured. A new method which may be used to overcome this lack of structure is to simulate the working conditions for the piston ring. This is the main objective of this thesis work, to invent a simulation method which allows accurate and distinct results to be obtained and thereby knowledge about piston ring performance. The simulation method is based on a three-dimensional geometric model of the piston ring, where the radial geometry should be described by the lathe curve from industry. It should also be implemented and function automatically as a simulation tool. In short terms, the calculated stresses and strains in the material, the contact pressure against the cylinder liner and the piston ring twist should be evaluated. The simulation tool should be able to model two different types of piston ring designs, namely straight cut design and CPR design, and both with optional dimensions. Validation of the results are performed with a simulation model which uses fewer dimensions, but also utilizes engineering knowledge from the marine industry. In addition to this, some more advanced investigations have been performed in order to demonstrate the capacity and power of the simulation tool. The simulation method appears to perform well and according to the simple model, but it also shows good prediction in more advanced investigations. For example, piston rings in overheated engines tend to twist more than usual, which could be seen in real investigations, and the behavior is easily recreated with the simulation tool. Also investigations with reduced cross sections, which is well known within high-speed engines, are performed. The method is executed automatically with the developed simulation tool which is based on ANSYS, a commercial simulation software. This software, that is commonly used in development work, uses a finite element method to solve the problem. The simulation tool is used as an external input which configures the geometry, finite element formulation and the result rendering.<br>Kolvringen i en marin tvåtaktsmotor arbetar under krävande förhållanden i form av hög temperatur och högt tryck. Dess huvudsyften är att täta motorns förbränningskammare, minimera friktion mot cylindern och transportera värme från kolven. Utvecklingen av nya kolvringsmodeller för marint bruk är huvudsakligen baserat på ingenjörskunskap och expertkunnande vilket dock lett till en viss osäkerhet. En modern metod för att bemästra denna osäkerhet är att simulera kolvringen och dess förhållanden i motorn. Det huvudsakliga målet är att skapa en simuleringsmetod som ger noggranna och tydliga resultat och därav kunskap om kolvringens påfrestningar och egenskaper under drift av motorn. Simuleringsmetoden är skapad för en tredimensionell geometri som är beskriven av bl.a. den svarvkurva som används inom industrin. Metoden skall även vara implementerad och fungera automatiskt som ett beräkningsverktyg vilket inom en rimlig tidsrymd skall beräkna intresseområden såsom spänningar, kontakttryck och twist. Det skall även vara konstruerat så att två olika kolvringmodeller skall kunna simuleras, nämligen rakskuren ring och gastät ring, och båda med valbara dimensioner. Simuleringsmetoden är bekräftad genom att jämföra med en enklare simuleringsmodell samt teknisk kunskap och resonemang. Utöver att bekräfta modellen genomförs även en del mer avancerade undersökningar för att kunna återge simuleringsverktygets verkliga effektivitet. Resultaten återger rätt karaktär och i rätt storleksordning i jämförelse med den enklare modellen men visar även på sanningenliga resultat vid mer avancerade tester. Exempelvis har överhettade motorer ofta en förstärkt twist, vilket är uppmärksammat vid mätningar, och sådana effekter kan återges med simuleringsverktyget. Även tester med förändrade tvärsnittsprofiler, vilka ofta används inom fordonsindustrin, och vilken effekt dessa profiler får på twistningen har genomförts. Metoden och det automatiska simuleringsverktyget är implementerat i den kommersiella programvaran ANSYS. Programmet använder sig av finita elementmetoden för att lösa problem och är ett vanligt program inom flera olika utvecklingsområden. Verktyget används som en extern inläsning till programmet vilket konfigurerar geometrin, finita elementformuleringen och resultatrenderingen.
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Schoemacker, Florian, Felix Fischer, and Katharina Schmitz. "Damping strategies for energy efficient pressure controllers of variable displacement pumps." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71108.
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In hydraulic-mechanically controlled variable displacement pumps, the actual pump controller produces additional power losses. Due to the low damping coefficients of all pump controller’s components, hydraulic-mechanically pressure controlled pumps use to oscillate while adjusting the pressure level in the hydraulic system. In several state-of-the-art variable pump controllers, a damping orifice connects the control actuator’s displacement chamber with the reservoir. This bypass dampens the movement of the control actuator but also leads to bypass losses during steady-state operation of the pump. A new concept for damping via feedback loops avoiding bypass losses is presented in t his paper.
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Naik, Pratin J., Ganesh K. Seeniraj, and Ram S. Chandran. "A study into forces and moments acting on the swash plate of an axial piston pump using a novel approach to reduce pressure and flow pulsations." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71105.
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In hydraulic pumps, typically in axial piston pumps, reduction of pressure and flow ripples was attempted by providing relief grooves and pre-compression for noise reduction. Pre-compression is normally achieved by using the dead space between pump ports in the valve plate. Also valve plate profile modification is required, if system operating conditions such as pump output pressure and flowrate change, to maintain optimum operating conditions for reduced pressure/flow ripple. An earlier simulation study confirmed effectiveness of varying dead centre position to reduce pressure and flow ripples. A specifically designed mechanism, outlined in the earlier work, achieves this goal by varying the dead centre position of the pump swash plate. This study reports on the findings of the effect of varying dead centre position and groove configurations on forces and moments acting on the swash plate for various operating conditions. The simulation model cited in the earlier work was used in this study. This information is vital for the design of an actuating mechanism to vary dead centre position of a pump valve plate. These simulations were run using MATLAB/Simulink and S-functions. Results of this study are promising.
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Semeniuk, Konstantin. "Correlated low temperature states of YFe2Ge2 and pressure metallised NiS2." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274346.
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While the free electron model can often be surprisingly successful in describing properties of solids, there are plenty of materials in which interactions between electrons are too significant to be neglected. These strongly correlated systems sometimes exhibit rather unexpected, unusual and useful phenomena, understanding of which is one of the aims of condensed matter physics. Heat capacity measurements of paramagnetic YFe$_{2}$Ge$_{2}$ give a Sommerfeld coefficient of about 100 mJ mol$^{−1}$ K$^{−2}$, which is about an order of magnitude higher than the value predicted by band structure calculations. This suggests the existence of strong electronic correlations in the compound, potentially due to proximity to an antiferromagnetic quantum critical point (QCP). Existence of the latter is also indicated by the non-Fermi liquid T$^{3/2}$ behaviour of the low temperature resistivity. Below 1.8 K a superconducting phase develops in the material, making it a rare case of a non-pnictide and non-chalcogenide iron based superconductor with the 1-2-2 structure. This thesis describes growth and study of a new generation of high quality YFe$_{2}$Ge$_{2}$ samples with residual resistance ratios reaching 200. Measurements of resistivity, heat capacity and magnetic susceptibility confirm the intrinsic and bulk character of the superconductivity, which is also argued to be of an unconventional nature. In order to test the hypothesis of the nearby QCP, resistance measurements under high pressure of up to 35 kbar have been conducted. Pressure dependence of the critical temperature of the superconductivity has been found to be rather weak. μSR measurements have been performed, but provided limited information due to sample inhomogeneity resulting in a broad distribution of the critical temperature. While the superconductivity is the result of an effective attraction between electrons, under different circumstances the electronic properties of a system can instead be dictated by the Coulomb repulsion. This is the case for another transition metal based compound NiS$_{2}$, which is a Mott insulator. Applying hydrostatic pressure of about 30 kbar brings the material across the Mott metal-insulator transition (MIT) into the metallic phase. We have used the tunnel diode oscillator (TDO) technique to measure quantum oscillations in the metallised state of NiS$_{2}$, making it possible to track the evolution of the principal Fermi surface and the associated effective mass as a function of pressure. New results are presented which access a wider pressure range than previous studies and provide strong evidence that the effective carrier mass diverges close to the Mott MIT, as expected within the Brinkman-Rice scenario and predicted in dynamical mean field theory calculations. Quantum oscillations have been measured at pressures as close to the insulating phase as 33 kbar and as high as 97 kbar. In addition to providing a valuable insight into the mechanism of the Mott MIT, this study has also demonstrated the potential of the TDO technique for studying materials at high pressures.
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Avon, Michael A. "Fluid Flow Through Carbon Nanotubes: A New Modeling and Simulation Approach." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1248615375.
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Bou, leba bassil Marianne. "Étude des mécanismes aérodynamiques à l'origine du bruit de contact pneumatique/chaussée." Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0019.
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Cette thèse traite des mécanismes de pompage d'air à l'origine du bruit de roulement dans le cas d'un pneumatique lisse roulant sur une cavité cylindrique intégrée à la chaussée. Un modèle CFD est utilisé pour calculer la variation de la pression d'air dynamique au fond de la cavité dont le volume varie durant le contact avec le pneu. Une méthode de piston a été validée pour modéliser cette variation de volume par un déplacement vertical du fond de la cavité, équivalent à la variation de son volume causée par la pénétration de la bande de roulement durant le contact. La variation de volume utilisée dans le modèle de piston est déterminée tout d'abord numériquement par un modèle de contact puis expérimentalement par la mesure de la pénétration de la gomme sur un banc d'essai. Ce dernier a également servi pour la mesure de la pression d'air dynamique au fond de la cavité, montrant que le pompage d'air dépend peu de la charge appliquée mais augmente avec la vitesse et diminue avec la profondeur de la cavité. Ces résultats sont ensuite comparés aux résultats numériques prenant en compte les différentes configurations expérimentales. La surpression interne calculée au fond de la cavité augmente avec la variation de volume et l'accord avec la mesure est satisfaisant. Le calcul de la pression d'air dynamique aux bords d'attaque et de fuite montre que le pompage d'air interne lors de l'ouverture de la cavité génère une onde qui se propage à l'extérieur principalement vers l'arrière du pneu. Le niveau d'énergie des ondes émises augmente avec la vitesse de roulement suivant un exposant de vitesse dont la valeur dépend du pourcentage de variation de volume de la cavité<br>This thesis deals with air-pumping mechanisms leading to tyre/road noise in the case of a slick tyre rolling on a cylindrical road cavity. A CFD model was used to calculate the dynamic air pressure variation at the cavity bottom, assuming a volume variation of this cavity during contact with the tyre. A piston method was validated in order to model this volume variation by a vertical displacement of the cavity bottom, equivalent to the volume variation caused by the tyre tread penetration during contact. The volume variation used in the piston model was determined first numerically by a contact model and then experimentally by measuring the penetration of the rubber on a test rig. The latter was also used for the measurement of dynamic air pressure at the cavity bottom, showing that air-pumping fewly depends on the applied load but increases with speed and decreases with the cavity depth. These results were then compared with the numerical results modeling the experimental set-up, considering the different testing configurations. The internal overpressure calculated at the cavity bottom increases with the change in volume and the agreement with measurements was satisfactory. The calculation of the dynamic air pressure at the leading and trailing edges showed that the internal air-pumping during the cavity opening generates an external wave which propagates mainly towards the rear of the tyre. The energy level of the emitted waves increases with the rolling speed according to a speed exponent which value depends on the percentage of the cavity volume variation
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Biggs, Timothy James. "Studies of crystalline organic molecular materials under extreme conditions." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:51dae806-2954-4ea7-a3cb-1980ecb53e98.
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This thesis describes investigations into the properties of -phase BEDT-TTF charge transfer salts. Charge transfer salts are mainly studied as they are very useful test beds for fundamental physics due to the tuneability of their proper- ties and ground states. The effects of temperature and pressure on such systems have been studied, as these allow access to a wide range of different states and properties. Transport properties of these systems have been studied to obtain information about the Fermi surface and effective mass, and the effect of deuter- ation and also change of pressure media will be discussed. The interaction of infrared radiation with these systems has also been investigated and simultaneous pressure and temperature measurements will be presented, something not greatly studied due to the large technical challenges. The techniques and approaches for overcoming these are also discussed. Chapter 1 provides an introduction to the organic materials themselves with particular emphasis on the actual compounds studied. Chapter 2 provides the necessary theoretical background for studying organic charge transfer salts using magnetic quantum oscillations and their infrared re- ectivity. Chapter 3 covers the experimental techniques and also discusses some of the challenges encountered and their solutions to aid others working in this area. Chapter 4 describes an investigation into the transport properties of - (ET)2Cu(SCN)2 by studying Shubnikov-de Haas oscillations using both deuter- ated and normal samples and using two different pressure media, and comparing it to work done using a third. Chapter 5 presents an investigation into the pressure dependence of selected phonon modes in -(ET)2Cu(SCN)2 using infrared radiation on a deuterated sam- ple. Chapter 6 presents what is believed to be the first pressure and temperature dependent infrared study of an organic molecular material. In this case the or- ganic molecular material is d8--(ET)2Cu[N(CN)2]Br, but the techniques should be readily transferable to other materials.
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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.<br><p>QC 20131204</p>
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Holík, Petr. "Úcpávky turbodmychadel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230162.
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This master’s thesis deals with theme of turbocharger seals. The aims of a thesis are to compare a turbocharger seals used in PBS Turbo turbochargers and to describe a testing of a seals. Principle of turbocharging and types of turbocharger are described in fist part. Next point of the thesis is describing of a face seals and non-contacting seals. The main part of the thesis describes kinds and reasons of seals testing; also contains comparison between labyrinth seals and piston ring, comparison of seals of PBS Turbo’s turbochargers and assesses the impact of turbocharger angle on the tightness of the seal.
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Noordzij, L. Bouke. "Measurement and analysis of piston inter-ring pressures and oil film thickness and their effects on engine oil consumption." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10925.
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Rydén, Gustav, and Fredrik Anarp. "Beräkningsmodell för slagtider av pneumatiska manöverdon : En experimentell och teoretisk studie av beteendet för pneumatiska cylindrar samt manöverdon." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166356.
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Denna rapport redogör framtagningen av en beräkningsmodell för slagtider av pneumatiska cylindrar och manöverdon. Slagtiderna för ett manöverdon kan bestämmas genom experimentella tester. För att underlätta och minska tiden som krävs i samband med testerna skapas en beräkningsmodell som presenterar teoretiska värden för slagtiderna. Denna beräkningsmodell stämmer kvalitativt överens med de experimentella tester som också genomförs i detta arbete. Testerna genomförs först på en enkel pneumatisk cylinder vilket bidrar till kunskaper om slagkarakteristik och slagtider. Denna kunskap är till hjälp för utveckling av beräkningsmodellen. Under testerna mäts bland annat slagtid, kammartryck och kolvens förflyttning vid en mängd olika driftförhållanden. Testerna visar att en av de mest kritiska parametrarna för beräkningsmodellen är C-värdet, en parameter som beskriver flödeskarakteristiken för pneumatiska komponenter. För att få beräkningsmodellen att fungera väl behöver ett så korrekt C-värde som möjligt användas. Beräkningsmetodiken består i stora drag av samband för fyllning och tömning av pneumatiska volymer samt tryckförändringar i cylinderkamrarna vid kompression och expansion. Med en kombination av dessa ekvationer är det möjligt att beräkna slagtiden. Eftersom beräkningsmodellen vill hållas relativt enkel görs ett antal antaganden om systemets parametrar. Dessa antaganden utvärderas efter deras påverkan på slagtiden. Validering mot experimentella resultat visar att beräkningsmodellen generellt fungerar bättre vid höga matningstryck och kritiska flöden. När matningstrycket är lågt och underkritiska flöden erhålls påverkas slagtiden av många fler parametrar, vilket gör att beräkningsmodellen får något sämre precision. Detta resultat är inte helt oväntat eftersom sambandet för kritiskt flöde är relativt enkelt.<br>This thesis work describes the development of a calculation model for stroke times of pneumatic cylinders and actuators. The stroke time of an actuator can be determined by experimental tests. To facilitate and reduce the time required in connection with the tests, a calculation model is created which presents theoretical values of the stroke time. This calculation model is qualitatively consistent with the experimental tests carried out in this work. The tests are first carried out on a simple pneumatic cylinder, which contributes to knowledge of stroke characteristics and stroke times. This knowledge is helpful for the development of the calculation model. During the tests the stroke time, chamber pressure and piston movement are measured in a variety of operating conditions. The tests show that one of the most critical parameters for the calculation model is the C value, a parameter that describes the flow characteristics of pneumatic components. To make the calculation model reliable, a reasonable C value need to be used. The calculation method consists largely of equations for filling and emptying of pneumatic volumes as well as pressure changes in the cylinder chambers during compression and expansion. With a combination of these equations it is possible to calculate the stroke time. Since the calculation model wants to be kept relatively simple, several assumptions are made about parameters in the system. These assumptions are evaluated according to their potential and impact on the stroke time. Validation experiments show that the calculation model generally works better at high supply pressures and critical flows. When the supply pressure is low and subcritical flow are obtained, the stroke time is affected by many more parameters, which lower the precision of the calculation model. This result is not entirely unexpected since the critical flow equations are relatively simple.
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REJOWSKI, EDNEY D. "Caracterização e desempenho de um filme de carbono amorfo hidrogenado tipo diamante (a-C-H) dopado com silício, aplicado em camisa de cilindro de motor à combustão interna." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10143.
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Made available in DSpace on 2014-10-09T12:35:14Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T13:58:01Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Turunen, H. (Helka). "CO₂-balance in the athmosphere and CO₂-utilisation:an engineering approach." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514294877.
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Abstract The subject of the thesis was to analyze by an engineering approach the global CO₂ balance and CO₂ utilisation. The aim was to apply methods and knowledge used in engineering sciences to describe the global CO₂ balance and the role of CO₂ in anthropogenic utilisation applications. Moreover barriers restricting commercialisation of new applications are discussed. These subjects were studied by literature reviews and calculations based on thermodynamics models. Engineering methods have shown to be applicable to describe the global balance of CO₂ and to define by a numerical way the Earth’s system carrying capacity. Direct and indirect actions, which mitigate the overload situation, were derived from the results. To screen out the attractive CO₂ properties in utilisation applications a mapping analysis was carried out. Properties, which enhance mass and heat transfer, are one of the most meaningful characteristics from the chemical engineering point of view. Attractive properties are often achieved at the supercritical state. Engineering thermodynamic methods were used in fluid phase determination of the case studies. Even simple methods are sufficient to advice experimental research work. The thermodynamic knowledge is the basement in creation of industrial scale chemical processes. If detailed information on system properties is needed, a model development due to the special requirements of high pressure systems and CO₂ features is required. This knowledge covers property information from all the components involved in chemical reactions. In addition to engineering knowledge successful technology transfer requires positive social structure as well. Finally, if the humankind is willing to mimic Nature and use light of the Sun as an energy source in engineering systems, development of thermodynamic methods is required also in this area. Especially the work terms, originally defined in classical mechanical thermodynamics and afterwards formulised also in other parts of the engineering fields, play a key role. If this development work is successful, we may see the shift from thermodynamics approach to ‘photodynamics’. Mitigation of global warming is a problem, which needs several kinds of activities. As a result of this study, there are listed a few engineering actions, which have a possibility to contribute to the work towards the carbon neutral society<br>Tiivistelmä Väitöskirjatyössä sovelletaan insinööritieteissä käytettyjä metodeja ja tietämystä määriteltäessä ilmakehän CO₂-tase sekä antropogeenisten hyötykäyttökohteiden merkitys teollisissa prosesseissa ja globaaleissa CO₂-virroissa. Lisäksi pohditaan uusien CO₂-hyötykäyttösovellusten kaupallistamiseen liittyviä rajoitteita. Näitä aiheita on tutkittu käymällä läpi tieteellistä kirjallisuutta ja tekemällä laskelmia. Insinööritieteistä tutun taselaskennan avulla tarkastellaan ilmakehän CO₂-virtoja. Sen pohjalta määritetään numeerisesti maapallon CO₂-kantokyky. Tuloksista johdetaan suoria ja epäsuoria toimenpide-ehdotuksia, joiden avulla voidaan lieventää ilmakehän CO₂-ylikuormaa. Kartoitusmenetelmän avulla selvitetään hyötykäytön kannalta edulliset CO₂:n aineominaisuudet. Kemiantekniikan näkökulmasta ominaisuudet, jotka parantavat aineen- ja lämmönsiirtoa, ovat kiinnostavimpia. Nämä ominaisuudet tulevat esille silloin, kun fluidi on ylikriittisessä olomuodossa. Termodynaamisia laskentamenetelmiä sovelletaan esimerkkiseosten olomuodon eli faasin määrityksessä. Tulokset osoittavat, että jopa verraten yksinkertaiset menetelmät antavat tietoja, jotka auttavat ymmärtämään laboratoriokokeiden faasikäyttäytymistä. Teollisen mittakaavan kemiallisten prosessien kehityksessä ja suunnittelussa termodynamiikan hallitseminen on keskeinen edellytys. Jos CO₂:n kiinnostavia ominaisuuksia toivotaan hyödynnettävän teollisesti, korkeapaineisten systeemien termodynaamisen teorian hallinta sekä aineominaisuuksien määrittäminen kaikille systeemiin osallistuville komponenteille ja niiden seoksille nousee merkittävään asemaan. Läpikotainen teorian ja teknisten perusteiden hallitseminen ei vielä takaa menestyksellistä teknologiansiirtoa pienestä suureen mittakaavaan. Lisäksi tarvitaan myönteinen ja kannustava yhteiskuntajärjestelmä. Mikäli tavoitellaan vielä rohkeampaa kehitysnäkymää, tilannetta, jossa luonnon tavoin CO₂-prosessien energianlähteenä käytettäisiin auringonvaloa, havaitaan, että tämäkin askel edellyttäisi termodynaamista menetelmäkehitystä. Keskeinen termodynaaminen konsepti on työ. Työ siirtää energiaa ympäristön ja systeemin välillä. Tämä on määritelty jo klassisessa mekaniikassa; kappaleen siirto tietystä paikasta toiseen. Kemiantekniikassa työlle on kehitetty käyttökelpoisia kaavoja paine–tilavuus–lämpötila-systeemeihin. Mikäli työn elementit kyettäisiin määrittelemään auringonvalon fotoenergialle, avaisi se uusia näkymiä reaktiokemiaan. Silloin termodynamiikan sijaan voitaisiin ehkä mieluummin puhua 'photodynamiikasta'. Ilmaston lämpeneminen on ongelma, jonka lieventämiseen tarvitaan useanlaisia toimia. Etsittäessä tietä kohti hiilineutraalia yhteiskuntaa, insinöörit voivat avustaa suunnan löytämisessä hyödyntämällä tieteenalallaan käytettyjä metodeja ja teorioita sekä tarpeen vaatiessa kehittää niitä edelleen uusille alueille
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陳明飛. "Performance analysis of pressure-compensated axial piston pumps." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/08431663178914481397.
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邱清鳳. "Efficiency optimization of pressure-compensated axial piston pumps." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/06737658732707404356.
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(10135868), Meike H. Ernst. "Enabling High-Pressure Operation with Water for the Piston-Cylinder Interface In Axial Piston Machines." Thesis, 2021.
Find full textAbstract:
<div><p>Water is inflammable, non-toxic, environmentally friendly---
desirable traits, for a hydraulic fluid. However, its extremely low viscosity
diminishes the load-bearing and sealing capacity of lubricating interfaces.
Case in point: axial piston machines of swash plate design are compact, highly
efficient positive displacement machines at the heart of hydraulic systems in
forestry, construction, aerospace, and agricultural equipment, as well as
industrial applications (presses, etc.); however, the three main lubricating
interfaces decisive to the performance of such units in terms of both component
life and efficiency are challenged by the use of water as working fluid.
Especially during high-pressure operation, this low-viscosity lubricant can
cause the these interfaces to fail in carrying the imposed load, resulting in
severe wear, or even pump failure. The piston-cylinder interface is
particularly challenging to design for water because it stands under obligation
to carry the heavy side load that acts on the pistons of these machines, which
increases with operating pressure. Furthermore, the architecture of axial
piston machines of swash plate design does not allow this interface to be
hydrostatically balanced.</p>
<p> </p>
<p>Through the development of a methodology that separates the
fluid pressure fields of the three main lubricating interfaces of axial piston
machines into their hydrostatic and hydrodynamic components, the present work
enables a direct comparison of these interfaces in terms of how they support
load. A case study of a 75 cc unit running on hydraulic oil conducted via this
methodology at three different operating conditions (low pressure/low speed,
low pressure/high speed, and high pressure/low speed) demonstrates that in the
piston-cylinder interface, the force from hydrostatic pressure reaches such
high magnitudes over the high-pressure stroke that less than half of it is
needed to counter the load. The excess force from hydrostatic pressure then
becomes the load. Consequentially, hydrodynamic pressure must counter a force
from hydrostatic pressure that exceeds the original load. In the other two
interfaces, by contrast, over half the load is being carried by hydrostatic pressure,
thus significantly diminishing the amount of hydrodynamic pressure the
interfaces are required to generate in order to achieve full load support.
Moreover, nearly all of the moment on the piston is countered by hydrodynamic
pressure, while less than half of the moment on the block is countered by
hydrodynamic pressure, and the moment on the slipper is negligible by
comparison.</p>
<p> </p>
<p>While this case study only investigates one pump, it shows
how critical hydrodynamic pressure can be to load support in the
piston-cylinder interface. The use of a low-viscosity fluid, e.g. water,
reduces the hydrodynamic pressure that is generated in this interface, which,
at challenging operating conditions, can lead to metal-to-metal contact. However,
the performance of the interface can be improved via micro surface shaping,
i.e. by giving the surface of the piston, or the bore that it moves through, a
shape on the order of microns in height. The aim of present work is to pursue
design trends leading to surface shapes that will enable this interface to
function at higher pressures than currently achievable. </p>
<p> </p>
<p>This pursuit takes the form of systematic virtual design
studies, an optimization procedure, and an algorithm developed specifically for
tailoring the bore surfaces through which the pistons travel to piston tilt and
deformation. From this emerges not only a set of design trends corresponding to
the dimensions of two particularly powerful types of micro surface shaping, but
also a profound insight into the behavior of the water-lubricated
piston-cylinder interface fluid film, and how that behavior can be manipulated
by changing the component surfaces that constitute its borders. Furthermore, in
collaboration with Danfoss High Pressure Pumps, a physical prototype of a 444
cc axial piston pump with surface shaping generated via the aforementioned
algorithm has been constructed and tested, achieving a total pump efficiency
roughly 3% higher than that achievable by the commercial unit that the geometry
of the prototype is based on.</p><br></div>
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HAO-CHENG, LI, and 李豪政. "The Effect of Insert with Bio-Piston Design for Foot Pressure Reduction." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/95594546016496063869.
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碩士<br>國立陽明大學<br>醫學工程研究所<br>88<br>An adequate shoe insole releases the abnormal foot pressure but also controls the heel motion, absorbs the ground reaction force and minimizes the energy consumption during motion. The goal of this study is, therefore, to experimentally evaluate the existing materials, which are suitable for making a comfortable shoe insert, to evaluate numerically the effect of pressure reduction and energy return of the new design “ Bio-piston “ shoe insert.
The results of experiment showed that there was no clear relationship for the tested material properties in resilience, hardness, and density. A desirable insert material should have its hardness between 30 to 40 Shore C, rebound coefficients of 0.49 to 0.54, Young’s modulus less than 0.4Mpa, and Shear modulus less than 0.2 Mpa. In the foot arch study, it showed that the dynamic arch index of normal subjects was ranged 0.21 to 0.26 and the static arch index was ranged from 0.07 to 0.19. The height of arch measured from the lower edge of navicular to ground was 1.76+0.26 cm.
The finite element model consists of Bio-piston shoe insert and foot complex with total of 21988 nodes and 13176 elements. An ideal piston has the plug of 7mm in diameter and 2.5 mm high, matched with the cylinder of 8mm inner diameter, 2mm wall thickness and 4mm long. The pistons with pitch of 16mm showed an optimal capacity of load bearing. The Bio-piston design with insert material property of 1Mpa and 2 Mpa in metatarsal region showed the best plantar pressure relief. The plantar pressure was below 17.5 N/cm2-, which was similar to that of experimental measurement. This study also concludes that the soft form material has the character of energy absorption, therefore, it is good for rearfoot shock absorption and the hard material combines with piston design is good for forefoot energy return.
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Lin, Feng-Ren, and 林峰任. "Analysis and Design of Pressure Control in the Variable- Displacement Piston Pump." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/93859952220111971813.
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Chen, Ting-hao, and 成庭皓. "Measurements of the Inner Piston Motion and Cylinder Pressure of a Differential Stroke Internal Combustion Engine." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/12527928047554849795.
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碩士<br>國立中山大學<br>機械與機電工程學系研究所<br>97<br>The thermal efficiency of a differential stroke engine based on the Atkinson cycle is higher than that of engines with an Otto cycle or Diesel cycle. To fulfill the requirement of the expansion ratio that is greater than the compression ratio in the Atkinson cycle, a mechanism with an inner piston that can provide such a motion control in a differential stroke engine is needed. In order to measure both of the inner piston motion and the cylinder pressure of a differential stroke engine, this thesis is focused on building up a measurement system to inspect the design of a mechanism that achieves the motion needed in a differential stroke engine.
To obtain the inner piston motion in a differential stroke engine operated at a speed, the measurement system is equipped with a laser sensor and an angular encoder to identify the difference between the theoretical and experimental results. Also, to inspect the cylinder pressure, a pressure transducer is employed with the test bed so that both of the P-T diagram and P-V diagram can be calculated by using the measured result.
To demonstrate the effectiveness of the developed test bed, real experiments are performed. The developed measurement system has proved to be a useful tool during the developing processes of design and manufacture of differential stroke engines.
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(5930537), Abhimanyu Baruah. "VALVE PLATE DESIGN MODEL FOCUSING ON NOISE REDUCTION IN AXIAL PISTON MACHINES." Thesis, 2019.
Find full textAbstract:
<p>The advantages of high efficiency,
reliability, flexibility and high power to weight ratio make axial piston pumps
popular for use in a wide variety of applications like construction and
agricultural machinery, off road vehicles and aerospace applications. However,
a major drawback which limits their extensive use in other commercial
applications is noise. One of the important components in axial piston machines
is the valve plate, which influences the transition of the suction and delivery
flows into and out of the displacement chamber. Appropriate design of the valve
plate can play a significant role in influencing the rate of compression and
expansion in the displacement chamber, and hence contribute towards the
abatement of noise in axial piston machines. Furthermore, the relief grooves in
valve plates makes them relatively less sensitive to operating conditions for
the operation of the pump. The high sensitivity of the valve plate design
towards the pressure build up in the displacement chamber and towards the noise
sources are big motivation factors towards rigorously exploring the design
space to find suitable designs to meet the objective of noise reduction. This
motivates the development of an advanced computational tool, colloquially
called 'MiNoS', where a powerful optimization algorithm has been combined
together with a novel parametrization scheme for valve plate design and a 1D
simulation model of swash plate type axial piston machines to find optimized
designs which can contribute towards noise reduction in swash plate type axial
piston machines. Furthermore, incorporation of the appropriate constraint also
helps in avoiding designs susceptible to the onset of cavitation in the
displacement chamber. A case study performed using the developed computational
tool has been shown later in this work.</p>
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Weng, Ying-Che, and 翁英哲. "The influence of piston effect induced by MRT train to the passenger comfort and platform screen door wind pressure." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/67036626017727327421.
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博士<br>國立臺灣大學<br>機械工程學研究所<br>99<br>This article numerically investigates the flow field and presssure gradient which induces by piston effect when the train moving into tunnel. The underground mass rapid transit (MRT) includes tunnel entrance, pressure release shaft, bypass and main station. This paper studies the pressure change with number of MRT cases by using three-dimensional numerical simulation software, PHOENICS. There are three parts of MRT to be studied. The first part is to examine the human comfort of original design at tunnel entrance and simulate the tunnel entrance with different tilt angles and blackage ratios. The results show that the pressure change rate has the minimum value at tilt angle of 30o and blockage of 2.4. The second part is to simulate the station with pressure release shaft at different train speeds. The results indicate that the platform screen door (PSD) conforms to original design wind pressure of 3200 Pa and the pressure release shaft also has the shaftilation effect. The final part is to simulate and verify the train moving through different underground structures with normal speed of 65 km/hr. The results describe that the bypass device has decrease 7.9% PSD wind pressure than without. In the train pass by MRT structure sequence simulation, the train passes through bypass and then pressure release shaft has decreasement 4.2% PSD wind pressure. At the distance of 30 m from pressure release shaft to station, the PSD wind pressure has 5.3% decresement. In different pressure release vent area simulation tests, the PSD wind pressure has 4.5% decresement at 36 m2 pressure release vent area. In the pressure release shaft length simulation examination, the PSD wind pressure has decresement of 19.5% at the pressure release shaft length of 20 m.
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Hsieh, Kun Hung, and 謝坤宏. "Theory and Experimental Analysis of the Machining Profile of a Piston Ring with Non-uniform Pressure Distribution inside Cylinder." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/84785968298855020135.
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碩士<br>國立中正大學<br>機械系<br>87<br>A piston ring and piston assembly is commonly used in reciprocating engines and air compressors in order to prevent the high pressure gas in the cylinder chamber from leaking into the crankcase area. The design of the free shape of piston ring will effect the performance of the engines or air compressors. Insufficient design of the free shape of the piston ring will produce the high pressure air emissions, and effect the lubrication condition between piston ring and cylinder. It will produce the noise, vibration, the temperature rising, and the wear of piston rings. So the design of the free shape of the piston ring is the most important.
However, there are many different design requirements in different engines, for example, like the consideration of material choice and surface coatings, the section of piston ring, and the pressure distribution , etc. The most difficult aspect of these investigations is how to create a proper unloaded or free ring shape that will lead to different contact pressure distribution. This research focus on the design of the free ring shape which is load by different and non-uniform pressure distribution by using the Bernoulli-Euler theory and use the finite elements and experimental methods to prove this formulation.
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Kim, Joo Yeun. "Evaluation on the performance of three types of manure separators perforated pressure roller, screw press and reciprocating piston press /." 1988. http://catalog.hathitrust.org/api/volumes/oclc/20079704.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1988.<br>Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 117-118).
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Wu, Jia. "Experimental determination of F partitioning between fluid and hydrous minerals in subduction zones." Thesis, 2013. http://www.theses.fr/2013CLF22351/document.
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Résumé en français indisponible<br>Mechanisms of volatile transfer from subducting slab to the melting region beneath arc volcanoes are probably the least understood process of arc magma genesis. Fluorine, which suffers minimum degassing in arc primitive melt inclusions, retains the information about the role of volatiles during magma genesis at depth. Experimentally determined solubility of F in aqueous fluid, and partition coefficients of F between fluid and minerals provide first order geochemical constraints about the volatile-transporting agent.My thesis experimentally determined F solubility in fluid and its partition coefficients among several phases. The systems are in equilibrium with hornblende and a humite group mineral (some contain melt or pyroxene) at 1 – 2 GPa, from 770 to 1047 °C, or equilibrium with hydrogrossular, pyroxene and norbergite or chondrodite at 2.5 – 3 GPa and 877 °C. The experiments were conducted with piston cylinder and cold sealing technique. The oxygen fugacity conditions were controlled by NNO buffer, while some were unbuffered. The fluids were extracted into volumetric flasks, and their compositions were determined by mass balance calculations. Moreover, the consistency was verified by HPLC for fluorine ion, and ICP-MS or ICP-AES for major cations of the quenched fluids.In 1 GPa experiments, the quench phases are so rare that the majority of the fluid compositions from direct analyses are consistent with mass balance results in their uncertainties. Moreover, my mass balance procedure takes into account all the measurements errors, which leads to large uncertainties on fluid compositions. The consistency demonstrates that most of fluorine aflter annealing in the capsule is present as fluorine ion. Futhermore, increases of the masses of starting materials, fluid proportions and analytical precisions will improve the uncertainties performances. ������������ can be represented by a single value 0.135 ± 0.036, which is independent of temperature, bulk composition and buffer conditions at 1 GPa. Df between fluid and humite group minerals is much less. Xf of hornblende and norbergite decrease from 1 to 2 GPa, while F partitionig between them doesn't change much. It indicates that F partitioning between fluid and minerals increases. Moreover, F concentrations in norbergite between NNO buffered and unbuffered experiments are significantly different. Meanwhile, Fe concentration variations of norbergite indicate that unbeffered experiments have higher oxygen fugacity than the NNO buffered ones. According to high temperature improves the free radical exchange reactions, H2O + 0.5O2 ⇄ 2OH. It indicates that both water fugacity and oxygen fugacity contribute to OH fugacity in fluid. I developed a simple model in which XF in humite group minerals are correlated to the ratio between F and OH. It is sucessfully applied to estimate the F concentration in the fluid, which co-exists with clinohumite, using Xf value.With the knowledge of my study, a new constraint can be framed on slab flux. The average F concentration in the fluid is 2700 ppm for F-rich experiments and it constrains the maximum amount of F carried by fluid in the presence of amphibole. Using partition coefficient of F to estimate F abundance in subducting slab, one can conclude that the increase of F concentration in the subarc mantle by fluid, in equilibrium with hornblende, to be less tan 5 ppm. Significant F enrichments found in arc lavas cannot be derived from aqueous fluid of subductiong slab in the presence of amphibole. Therefore, this result highlights the role either 1) slab melt, 2) fluid in equilibrium with eclogite, or perhaps 3) supercritical fluid for the element transfer from slab to mantle wedge
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Wales, Nadine Jenifer. "The effect of prewetting on the residence time distribution and hydrodynamic parameters in trickle bed reactors." Diss., 2008. http://hdl.handle.net/2263/27723.
Full textAbstract:
Residence time distributions have become an important analytical tool in the analysis of many types of flow systems. Residence time distributions have proven to be effective for analysing trickle bed reactors, as it allows determination of parameters under operating conditions allowing no interference of these conditions. By studying the residence time distribution a great amount of information can be obtained and therefore used to determine a number of hydrodynamic parameters. Due to recent findings that prewetting has a tremendous effect on a number of hydrodynamic parameters such as holdup, wetting efficiency and pressure drop, it is therefore the aim of this study to investigate the effect of trickle flow morphology or prewetting on a trickle bed reactor. The residence time distribution is obtained whereby hydrodynamic parameters are determined and therefore the effect the flow morphology has on various hydrodynamic parameters is highlighted. A number of methods were used to determine these parameters, namely that of the best-fit method, whereby the PDE model was used, and the method of moments. Operating conditions included varying gas and liquid flow rates for porous and non-porous catalyst particles at atmospheric pressure. The different prewetting procedures used during this work included the following: <ul><li>Non-wetted </li> <li>Levec-wetted </li> <li>Super-wetted</li></ul> From this investigation the following conclusions were made: <li>Prewetting has a great effect on the hydrodynamic parameters of trickle bed reactors</li> <li>The differences in prewetting can be attributed to differing flow morphologies for the different prewetted beds i.e. the dominant flow morphology for a non-wetted bed is that of rivulets and for prewetted beds that of film flow</li> <li>It was also found that at low liquid flow rates the flow morphology in prewetted beds changes from film flow to a combination of rivulet and film flow</li> <li>The different flow morphologies for prewetted and non prewetted beds was confirmed by the residence time distributions and various parameters obtained there from</li> <li>At low liquid flow rates the flow morphology becomes a more predominant factor in creating the tailing effect present in residence time distribution for prewetted beds</li> <li>The tailing effect in residence time distributions is a result of both internal diffusion and liquid flow morphology, where the liquid flow morphology is the more dominant factor</li> <li>The use of residence time distributions to determine a number of hydrodynamic parameters proved to be very useful and accurate by means of different methods, i.e. method of moments and best-fit method</li> <li>Differences in the liquid holdup determined from the method of moments and the weighing method confirmed that different flow morphologies exist for different prewetted beds</li> <li>An increase in the dispersion coefficient with prewetting was observed indicating that the amount of micro mixing is different for the different prewetted beds</li> <li>Differences in residence times and high values for the dynamic holdup, for the porous packing, confirmed that the PDE model does not model well the porous packing response curves due to the lack of internal diffusion and internal holdup in this model</li> <li>The dynamic-static mass transfer showed that film flow, as in prewetted beds, results in slower mass transfer as opposed to rivulet flow and therefore it is concluded that prewetting results in different flow morphologies.</li></ul> Following this study it is recommended that a residence time distribution model be used or developed that incorporates the effects of internal diffusion and internal holdup as present in porous catalyst particles. In addition, it was found that very few correlations could accurately predict hydrodynamic parameters due to the absence of the effect of prewetting and therefore it is recommended that correlations be developed that incorporate the effect of prewetting.<br>Dissertation (MEng)--University of Pretoria, 2008.<br>Chemical Engineering<br>unrestricted