Dissertations / Theses on the topic 'Reciprocating compressor'

The main objective of this research effort was the construction of a finger valve dynamics model using simplified theory based on steady flow conditions. The analytical valve positions were then compared to experimental measurements from an Ingersoll Rand model 242 two-stage air compressor. Proximity probes were used to measure the valve position at two points on the exhaust valve at two different exhaust valve stop heights and at two points on the intake valve at one intake valve stop height in the lower exhaust valve stop height configuration only. A data acquisition system was configured to signal average and digitize the analog data from the sensors using a digital oscilloscope. The data was then sent to and stored in data acquisition computer for future comparisons to analytical results. The comparisons of the analytical and experimental exhaust valve positions at both points and both valve stop heights were of good quality when the effects of oil stiction were taken into account. Also, the comparisons of the intake valve positions were of good quality after adjustments were made in the theoretical force on the valve calculation. The adjustments entailed accounting for flow-induced forces on the intake valve after piston reversal. Overall the simplified model predicted the valve positions with sufficient quality to warrant the model's use as a design tool.
Master of Science

Critical equipment plays an essential role in industry because of its lack of redundancy. Failure of critical equipment results in a major economic burden that will affect the profit of the enterprise. Lack of redundancy for critical equipment occurs because of the high cost of the equipment usually combined with its high reliability.

When we are analyzing the reliability of such equipment, as a result, there are few opportunities to crash a few pieces of equipment to actually verify component life.

Reliability is the probability that an item can perform its intended function for a specified interval of time under stated conditions and achieve low long-term cost of ownership for the system considering cost alternatives. From the economical standpoint, the overriding reliability issue is cost, particularly the cost of unreliability of existing equipment caused by failures.

Classical questions about reliability are:

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Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O presente trabalho trata da simulação de um compressor hermético alternativo operando em regime transiente. O modelo desenvolvido expande, para a simulação do regime transiente, de modelos de regime permanente existentes na literatura. No presente modelo o sistema é dividido em volumes de controle (motor, compressor, muflas, câmaras de sucção e de descarga, reservatório de óleo, linha de descarga, entre outros). Adota-se o modelo de parâmetros concentrados e aplicam-se as equações fundamentais de conservação, resultando em um sistema de equações diferenciais ordinárias. Especial atenção é dedicada à formação de espuma durante a partida. Sob tais condições, pode-se chegar à sucção de óleo por parte do compressor, com conseqüentes danos às partes móveis do conjunto mecânico. Em função da ausência de informação na literatura sobre formação de espumas em compressores herméticos, construiu-se um aparato experimental para reproduzir tais condições em laboratório. Utilizou-se uma combinação de refrigerante R134a e óleo poliol-ester, que foi submetida a condições controladas de despressurização, a partir de uma pressão inicial prescrita. O processo de formação de espuma (taxa, espessura e diâmetro de bolha) foi monitorado com o auxílio de uma câmara de vídeo digital. Uma série de corridas foi efetuada para diferentes concentrações de óleo e taxas de despressurização. Os dados experimentais permitiram estabelecer um modelo semiempírico de formação de espuma no interior de um compressor hermético. Simulou- se, também, o escoamento turbulento tridimensional de refrigerante no interior da carcaça.
The present work is related to the simulation of a reciprocating hermetic compressor operating in transient regime. Hermetic compressors consist of a motor-compressor assembly hermetically sealed in a welded steel shell. Main components are: electric motor, suction and discharge mufflers, discharge line and the compressor itself, formed by the suction and discharge chambers, the pistondriving mechanism assembly and the cylinder body. The model here presented extends existing thermodynamic steady-state models for the transient operational condition. The system is divided into a number of control volumes, for which homogeneously distributed properties is assumed and fundamental conservation equations are applied. Special attention is given for foam formation, during startup. In such conditions, liquid oil can be drawn into the cylinder, causing a deterioration in the performance. Information on the phenomenon is scarce, which led to an effort of reproducing it at laboratory conditions. A saturated mixture of R134a and polyolester oil, at a given pressure, was submitted to controlled depressurization. The foam formation process (rate, height and bubble size) was measured with the help of a digital video camera. A number of runs were carried out, for different pressure drop rates and initial refrigerant concentrations. The experimental data was employed to adapt an existing model of foam formation. A new function for the volume rate of coalescence of gas bubbles was empirically determined. Computational Fluid Dynamics techniques were also used to predict the turbulent three-dimensional flow of refrigerant in the shell side.

This research involves the study of a one- and two-cylinder convertible reciprocating Freon compressor for air conditioning or refrigeration purposes. The main concern is the reduction of the vibration (noise) caused during the operation of the compressor. Vibration is a main concern when the compressor is shifted from the one-cylinder operation to the two-cylinder operation mode and the reverse of this shift. The objectives for this research are (1) to investigate the shaking force due to the reciprocating mass at high frequencies, which are up to 4600 Hz (80w) in this research; (2) to determine the dominant force for compressor vibration among the three possible sources of shaking force due to reciprocating mass, impact forces due to clearance at the connecting rod - piston joint, and the z-axis force from the motor torque due to the rotor's conductor rods being skewed at an angle; (3) to minimize the difference in change of kinetic energies when switching between the one- and two-cylinder operating modes of the compressor. The properties of the vibration in one- and two-cylinder operation have been studied and results have been analyzed in terms of kinetic energies generated in different setting of operation of the compressor. Dynamic simulation for the impact force is computed using SIMULINK. The Z-axis force due to the motor is computed. Results indicated that shaking force due to the reciprocating mass is the dominant force for only the first two harmonics (w, 2w). An optimization routine based on Hooke and Jeeves pattern search method is developed and an optimized setting of angle, force, and torque for balancing of the crankshaft to achieve objective (3) is determined.
Master of Science

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O presente trabalho trata da caracterização e simulação de compressores alternativos dos tipos automotivo, hermético e semi-hermético, motivado pela necessidade de estudo de novos refrigerantes, com menor impacto ambiental, isto é, sem potencial de destruição da camada de ozônio e baixo potencial de efeito estufa. O estudo apresenta uma metodologia para a modelagem, mediante a qual, dependendo do tipo de compressor, este é dividido nos seguintes volumes de controle: mufla de sucção, câmara de sucção, cilindro de compressão, câmara de descarga, linha de descarga, motor elétrico, carcaça do compressor, massa metálica interna e gás escoando no interior da carcaça. Equações fundamentais de conservação, de troca de calor, de queda de pressão e de propriedades termofísicas do refrigerante são aplicadas a cada volume de controle. Buscando o desenvolvimento de modelos simples, porem, ainda capazes de identificar o desempenho do compressor operando com diferentes refrigerantes, optou-se pelo desenvolvimento de modelos semi-empíricos, determinando-se coeficientes empíricos, característicos do compressor e independentes do refrigerante ou das condições de operação. Foram efetuados ensaios calorimétricos normalizados em duas instalações laboratoriais existentes para os compressores hermético e semihermético. Para o compressor hermético foi utilizado o HFC-134a como referência e foram testados os refrigerantes HFO-1234yf e HFO-1234ze(E) e a mistura HDR-17. Para o compressor semi-hermético foi utilizada uma instalação de refrigeração comercial instrumentada do tipo ar-ar, operando com a mistura R404A (referência), tendo sido testados oito novos fluidos. Para o compressor automotivo foram utilizados dados experimentais do refrigerante HFO-1234yf, existentes na literatura. A caracterização dos compressores alternativos foi bem sucedida na medida em que os parâmetros empíricos determinados a partir de diferentes refrigerantes mostraram-se com valores suficientemente próximos. Nos testes experimentais foram identificados fluidos refrigerantes com desempenho maior e baixo potencial de aquecimento global. Atingiu-se, com a modelagem, o desenvolvimento de uma ferramenta computacional capaz de predizer as condições de operação de compressores alternativos operando com novos refrigerantes, a partir do modelo baseado em parâmetros empíricos obtidos de testes experimentais com refrigerantes convencionais, de fácil obtenção. O método de gradiente reduzido generalizado (GRG) foi utilizado na solução do sistema de equações não lineares, para a caracterização dos compressores alternativos. O modelo de simulação foi desenvolvido na linguagem Fortran. As propriedades termodinâmicas dos fluidos refrigerantes foram obtidas pelo pacote computacional REFPROP (NIST Standard Reference Database 23, Version 8.0). Os valores previstos pela simulação apresentaram boa concordância com os resultados experimentais.
This work shows a methodology for calculating the characteristic parameters of an open, a hermetic and a semi-hermetic reciprocating compressor. This study was motivated by the need to study new refrigerants with lower environmental impact with reduced global warming potential and zero ozone depletion potential. The compressor is divided in control volumes: suction muffler, suction chamber, compressor cylinder, discharge chamber, discharge line, electric motor, flowing gas through the compressor, compressor shell and inner metallic mass. Fundamental equations of conservation, heat exchange, pressure drop and thermophysical properties of the refrigerant are applied to each control volume. A semi-empirical model and standard calorimetric tests are used to obtain empirical parameters independents of refrigerant and operating conditions. For the hermetic compressor was used as reference the refrigerant HFC-134a and tested refrigerants HFO-1234yf, HFO-1234ze(E) and a mixture HDR-17. For the semihermetic compressor, an instrumented commercial refrigeration system operating with the mixture R404A was used as reference. In this system eight new fluids have been tested. For the automotive compressor experimental data from refrigerant HFO-1234yf obtained from literature were used. The characterization of the reciprocating compressors has been successful because the empirical parameters determined from different refrigerants proved to have sufficiently close values. A computational tool, able to predict the operating conditions of reciprocating compressors (open automotive, hermetic and semihermetic), working with new and untested refrigerants, was developed from the simulation models. The generalized reduced gradient (GRG) method was implemented in order to obtain a numerical solution for the characteristic parameters and the simulation computer program was developed in FORTRAN. Refrigerant properties were calculated using the software REFPROP version 8.0, developed by NIST, U.S.A.

The objectives of this research are the prediction of the thermodynamic behavior of a multi-stage intercooled reciprocating compressor and its progressive loss of performance due to leakage. A theoretical model is developed to simulate the thermodynamics of the compressor system and the lubricating condition and wear of the piston ring pack for a multi-stage intercooled reciprocating compressor. A first law of thermodynamics approach is used to determine the thermodynamic properties of the gas inside the cylinders, the intercoolers and the inlet and discharge manifold. The compressor valves are modeled as single degree-of-freedom, spring-mass=damper systems. The flows through the valves are calculated based on the steady flow equations for equivalent orifices. The lubricating condition of the piston ring pack are determined on the basis of hydrodynamic lubrication theory. The wear of the piston rings is assumed to occur when the hydrodynamic oil film between the piston ring and cylinder bore breaks down. Based on the theoretical model, a computer program is developed. This program is tested on an IngersoH-Rand Model 242, two stage aircooled reciprocating air compressor. The comparison of the experimental values of the pressure variations in the first cylinder with the value predicted by the computer program shows a reasonable match. The computer program predicts the pressure, temperature and mass flow rates for each cylinder and the intercooler. Also predicted is the wear rate of each piston ring. The progressive loss in the compressor mass discharge, and hence the loss in its performance, is determined by calculating the leakage losses several times, updating the leakage area each time based on the wear rate of the piston rings. The result shows a drop of about 15 percent in the discharge rate of the Model 242 compressor after 8000 hours of running time.
Master of Science

Oil feed grooves are implemented in reciprocating compressor piston applications to assure a constant supply of lubricating oil on bearing surfaces and decrease friction loss. In a hermetically sealed compressor, due to small clearances encountered, oil supply becomes critical in order not to operate in boundary lubrication regime. Due to the small size of the piston and small piston &ndash
cylinder clearance, a partial lubrication regime is present. In the current study, a model that solves Reynolds&rsquo
equation for piston-cylinder lubrication and the average Reynolds&rsquo
equation that considers the effect of roughness on partially lubricated bearing for a compressor piston with oil feed grooves is developed. A parametric study is carried out to investigate the effects of piston design parameters and then arrive at an improved piston performance by using alternative designs for oil feed groove and the other design parameters.

[ES] Esta tesis doctoral presenta un estudio de compresores scroll con inyección de vapor (SCVI) para bombas de calor que operan en climas fríos o para aplicaciones de calentamiento de agua a alta temperatura. Para ello, se comparó experimentalmente un SCVI con un compresor de dos etapas de pistones (TSRC) trabajando con R-407C en condiciones extremas. La comparación se realizó en términos de eficiencias del compresor, capacidad, COP y rendimientos estacionales tanto para el modo calefacción como para el modo refrigeración. Los resultados proporcionan una idea general sobre el rango de aplicación de los compresores estudiados y sobre las diferencias en los rendimientos de los compresores. Sin embargo, se identificaron varias limitaciones en la caracterización de los compresores y en el análisis del ciclo. Esto motivó a profundizar en el estudio del ciclo de compresión de dos etapas y sus componentes. El siguiente paso fue realizar un análisis teórico de los ciclos de compresión de dos etapas para aplicaciones de calefacción, en donde se identificó a la presión intermedia y a la relación de inyección como los parámetros del sistema más influyentes sobre el COP. La presión intermedia se optimizó para dos configuraciones de inyección (tanque de separación y economizador) utilizando varios refrigerantes. Basándose en los resultados de la optimización, se propuso una correlación que permite obtener la presión intermedia óptima del ciclo, considerando la influencia del subenfriamiento a la salida del condensador. Además, se analizó la influencia del diseño de los componentes del sistema sobre el COP del ciclo. Posteriormente, el estudio se profundizó a nivel de componentes. El factor más crítico en el sistema es el rendimiento del compresor. Por lo tanto, el siguiente paso fue evaluar la influencia de varios sistemas de compresión con inyección de vapor sobre el COP. Se tomaron en cuenta tres tecnologías de compresores, un SCVI, un TSRC y un compresor scroll de dos etapas (TSSC). Estas tecnologías de compresores fueron caracterizadas y modeladas para estudiar su rendimiento. Para ello, se propuso una nueva metodología para caracterizar compresores scroll con inyección de vapor. Esta metodología permite evaluar el rendimiento del compresor independientemente del mecanismo de inyección que se utiliza en el ciclo. Se identificó una correlación lineal entre la relación de inyección de refrigerante y la relación de compresión intermedia. Esta correlación se utiliza para determinar el flujo másico de inyección en función de la presión intermedia. Posteriormente, se propuso un modelo semi-empírico de compresores scroll y una metodología para extender dicho modelo para compresores scroll con inyección de vapor. Los modelos fueron ajustados y validados usando datos experimentales de cuatro compresores scroll trabajando con R-290 y un SCVI trabajando con R-407C. Finalmente, se comparó un SCVI con dos compresores de dos etapas, un TSSC y un TSRC, trabajando en condiciones extremas. Se optimizó la relación de volúmenes de los compresores de dos etapas. Los resultados muestran que, en las condiciones nominales de funcionamiento (Te=-15 °C, Tc=50 °C), la relación de volúmenes óptima del TSSC es 0.58, y del TSRC es 0.57. El TSSC consigue un COP 6% mayor que el SCVI y un COP 11.7% mayor que el TSRC. Bajo un amplio rango de condiciones de operación, el SCVI presenta una mejor eficiencia y COP para relaciones de presión inferiores a 5. Para relaciones de presión más altas, el TSSC presenta mejor rendimiento y consigue una temperatura de descarga más baja. Se concluye que el SCVI es una solución fácil de implementar, desde el punto de vista del mecanizado, y que permite extender el mapa de trabajo de los compresores de una etapa. Sin embargo, los resultados muestran que la compresión en dos etapas consigue mejorar en mayor medida el COP del ciclo y la capacidad, con una mayor redu
[CA] Aquesta tesi doctoral presenta un estudi de compressors scroll amb injecció de vapor (SCVI) per a bombes de calor que operen en climes freds o per a aplicacions d'escalfament d'aigua a alta temperatura. Per a això, es va comparar experimentalment un SCVI amb un compressor de dues etapes de pistons (TSRC) treballant amb R-407C en condicions extremes. La comparació es va realitzar en termes d'eficiències del compressor, capacitat, COP i rendiments estacionals tant per al mode calefacció com per al mode refrigeració. Els resultats proporcionen una idea general sobre el rang d'aplicació dels compressors estudiats i sobre les diferències en els rendiments dels compressors. No obstant això, es van identificar diverses limitacions en la caracterització dels compressors i en l'anàlisi del cicle. Això va motivar a aprofundir en l'estudi del cicle de compressió de dues etapes i els seus components. El següent pas va ser realitzar una anàlisi teòrica dels cicles de compressió de dues etapes per a aplicacions de calefacció, on es va identificar la pressió intermèdia i la relació d'injecció com els paràmetres del sistema més influents sobre el COP. La pressió intermèdia es va optimitzar per a dues configuracions d'injecció (tanc de separació i economitzador) utilitzant diversos refrigerants. Basant-se en els resultats de l'optimització, es va proposar una correlació que permet obtindre la pressió intermèdia òptima del cicle, considerant la influència del subrefredament a l'eixida del condensador. A més, es va analitzar la influència del disseny dels components del sistema sobre el COP del cicle. Posteriorment, l'estudi es va aprofundir a nivell de components. El factor més crític en el sistema és el rendiment del compressor. Per tant, el següent pas va ser avaluar la influència de diversos sistemes de compressió amb injecció de vapor sobre el COP. Es van prendre en compte tres tecnologies de compressors, un SCVI, un TSRC i un compressor scroll de dues etapes (TSSC). Aquestes tecnologies de compressors van ser caracteritzades i modelades per a estudiar el seu rendiment. Per a això, es va proposar una nova metodologia per a caracteritzar compressors scroll amb injecció de vapor. Aquesta metodologia permet avaluar el rendiment del compressor independentment del mecanisme d'injecció que s'utilitza en el cicle. Es va identificar una correlació lineal entre la relació d'injecció de refrigerant i la relació de compressió intermèdia. Aquesta correlació s'utilitza per a determinar el flux màssic d'injecció en funció de la pressió intermèdia. Posteriorment, es va proposar un model semi-empíric de compressors scroll i una metodologia per a estendre aquest model per a compressors scroll amb injecció de vapor. Els models van ser ajustats i validats utilitzant dades experimentals de quatre compressors scroll treballant amb R-290 i un SCVI treballant amb R-407C. Finalment, es va comparar un SCVI amb dos compressors de dues etapes, un TSSC i un TSRC, treballant en condicions extremes. Es va optimitzar la relació de volums dels compressors de dues etapes. Els resultats mostren que, en les condicions nominals de funcionament (Te=-15 °C, Tc=50 °C), la relació de volums òptima del TSSC és 0.58, i del TSRC és 0.57. El TSSC aconsegueix un COP 6% major que el SCVI i un COP 11.7% major que el TSRC. Sota un ampli rang de condicions d'operació, el SCVI presenta una millor eficiència i COP per a relacions de pressió inferiors a 5. Per a relacions de pressió més altes, el TSSC presenta millor rendiment i aconsegueix una temperatura de descàrrega més baixa. Es conclou que el SCVI és una solució fàcil d'implementar, des del punt de vista del mecanitzat, i que permet estendre el mapa de treball dels compressors d'una etapa. No obstant això, els resultats mostren que la compressió en dues etapes aconsegueix millorar en major mesura el COP del cicle i la capacitat, amb una major reducció de la
[EN] This Ph.D. thesis presents a study of scroll compressors with vapor-injection (SCVI) for heat pumps operating in cold climates or in high-temperature water heating applications. To do so, firstly, an SCVI was experimentally compared with a two-stage reciprocating compressor (TSRC) working with R-407C under extreme conditions. The comparison was made in terms of compressor efficiencies, capacity, COP, and seasonal COP, both for heating and cooling modes. The results give a general idea about the application range of the studied compressors and the differences in the compressors' performance. Nevertheless, several restrictions in the compressors' characterization and the cycle analysis were identified. This motivated us to deepen in the study of the two-stage compression cycle and its components. The next step was performing a theoretical analysis of two-stage compression cycles for heating applications, where the intermediate pressure and the injection ratio were identified as the most influential system parameters on the COP. The intermediate pressure was optimized for two vapor-injection configurations (flash tank and economizer) using several refrigerants. Based on the optimization results, a correlation was proposed that allows obtaining the optimal intermediate pressure of the cycle, considering the influence of the subcooling at the condenser outlet. In addition, a theoretical analysis of the influence of the design of the system components on the COP of the cycle was performed. Once the thermodynamic analysis of the two-stage cycle was carried out, the study was deepened at the component level. The most critical factor in the system is the compressor performance. Hence, the next step was evaluating the influence of several compression systems with vapor-injection on the COP. Three compressor technologies were taken into account, an SCVI, a TSRC and a two-stage scroll compressor (TSSC). These compressor technologies were characterized and modeled in order to study their performance. To do so, a new methodology to characterize SCVI was proposed. This methodology allows evaluating the compressor performance independently of the injection mechanism used in the cycle. A linear correlation was identified between the refrigerant injection ratio and the intermediate compression ratio. This correlation is used to determine the injection mass flow as a function of the intermediate pressure. Then, a semi-empirical model of scroll compressors and a methodology to extend the model for scroll compressors with vapor-injection was proposed. The models were adjusted and validated using experimental data from four scroll compressors working with R-290 and an SCVI compressor working with R-407C. Finally, an SCVI was compared with two two-stage compressors, a TSSC, and a TSRC, working in extreme conditions. The displacement ratio of the two-stage compressors was optimized. Results show that, at the nominal operating conditions (Te=-15 °C, Tc=50 °C), the optimal displacement ratio of the TSSC is 0.58, and of the TSRC is 0.57. The TSSC achieves 6% larger COP than the SCVI and 11.7% larger COP than the TSRC. Under a wide range of operating conditions, the SCVI presents a better efficiency and COP for pressure ratios below 5. For higher-pressure ratios, the TSSC presents better performance and achieves lower discharge temperature. It is concluded that the SCVI is an easy solution to implement from the point of view of machining, which allows extending the working map of the single-stage compressors. However, the results show that the two-stage compression technology gets further improve the COP of the cycle and the capacity, with a greater reduction of the discharge temperature operating under extreme conditions.
I thank the financial support provided by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT) of Ecuador, through the international scholarship program for postgraduate studies “Convocatoria Abierta 2013 Segunda Fase, Grant No 2015-AR37665”.
Tello Oquendo, FM. (2019). Study of scroll compressors with vapor-injection for heat pumps operating in cold climates or in high-temperature water heating applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120473
TESIS

У роботі виконано розрахунок параметрів у вузлових точках циклу одноступеневої холодильної машини, в результаті чого визначено необхідну продуктивність компресора. Потім виконано порівняльний аналіз поршневого, гвинтового та спірального компресорів за загальноприйнятою методикою та за допомогою програмного забезпечення компанії Bitzer. За результатами розрахунку і аналізу виконано підбір компресора, який найбільше задовольняє вимогам. У розділі охорони праці виконано аналіз шкідливих та небезпечних факторів при експлуатації холодильного обладнання та виконано розрахунок природного та штучного освітлення ділянки цеху, де експлуатується холодильна машина.
В работе выполнен расчет параметров в узловых точках цикла одноступенчатой холодильной машины, в результате чего определена необходимая производительность компрессора. Затем выполнен сравнительный анализ поршневого, винтового и спирального компрессоров по общепринятой методике и с помощью программного обеспечения компании Bitzer. По результатам расчета и анализа выполнен подбор компрессора, наиболее удовлетворяющий требованиям. В разделе охраны труда выполнен анализ вредных и опасных факторов при эксплуатации холодильного оборудования и расчет природного и искусственного освещения участка цеха, где эксплуатируется холодильная машина.
In the work, the parameters are calculated at the nodal points of the cycle of a single-stage refrigeration machine, as a result of which the required compressor performance has been determined. Then a comparative analysis of reciprocating, screw and scroll compressors was carried out according to the generally accepted method and using the Bitzer software. Based on the results of the calculation and analysis, the selection of the compressor that most satisfies the requirements was made. In the labor protection section, the analysis of harmful and hazardous factors during the operation of refrigeration equipment and the calculation of natural and artificial lighting of the section of the workshop where the refrigeration machine is operated are carried out.

The numerical simulation model presented is based on the integration of the fluid conservation equations (continuity, momentum and energy) in the whole compressor domain (compression chamber, valves, manifolds, mufflers, connecting tubes, parallel paths, etc.) using instantaneous local mean values for the different variables. It is interesting to remark how momentum equation has been taken into account in all compressor parts and the possibility to solve parallel paths, resonators, etc. Effective flow areas are evaluated considering multidimensional models based on modal analysis of fluid interaction in the valve. Then, second and third order vibration models of valve are also considered. The possibility to use compound bound has been also implemented.

The force balances in the crankshaft connecting rod mechanical system are simultaneously solved at each time-step considered in the thermal and fluid dynamic compressor model. It allows to evaluate the instantaneous compression chamber volume and the different forces in the crankshaft connecting rod mechanical system. Mechanical system forces allows to know important information to predict possible
over-stresses in piston, piston pin, crankshaft, connecting rod, etc.

The thermal analysis of the solid elements is based on global energy balances at each macro volume considered (shell, muffler, tubes, cylinder head, crankcase, motor, etc.). Some improvements can be implemented (shell conduction, heat transfer coefficient evaluation, etc.).

The resulting governing equations (fluid flow, valve dynamics, conduction heat transfer in solids, etc.) are discretized by means of a fully implicit control volume formulation. The complete set of algebraic equations are coupled using the segregated he complete set of algebraic equations are coupled using the segregated pressure based algorithm Semi-Implicit Method for Pressure-Linked Equations(SIMPLEC) extended to compressible flow. Second and third time order schemes have been implemented for the transient terms.

An extensive hermetic reciprocating compressor experimental validation has been presented and the experimental know-how acquired has been highlighted. Furthermore, two commercial hermetic reciprocating compressor have been instrumented in detail to obtain the thermal temperatures map and the pressure fluid evolutions along compressor for different working conditions. It is interesting to remark as a novelty, the use of very small absolute pressure transducers, instead of the standard relative transducers. They allow to know instantaneous absolute pressure inside compressor chamber, without the necessity of measurement an absolute pressure outside the compression chamber (as is usual in this kind of experimental works).

The global comparative results have allowed to check the possibilities of the numerical simulation presented above and its accuracy compared with experimental data. After that, this work show the capabilities offered by the simulation presented and its final objective, a better understanding of the thermal and fluid dynamic compressor behaviour to improve the design of these equipments.

Then, the objective has been to review and present different physically meaningful parameters that characterize the reciprocating compressor behaviour (volumetric efficiency, isentropic efficiency, heat transfer efficiency, mechanical, electrical and heat losses, Coefficient of Performance, etc.), their influence detachment and evolution under different working conditions, with the idea to predict the performance of hermetic reciprocating compressors under different working conditions using the above mentioned non-dimensional parameters.

Finally, a parametric study of hermetic reciprocating compressors behaviour has been carried out. Results presented show the influence of different aspects (geometry, valves, motor, working conditions, etc.) in the compressor behaviour.

The parametric studies and compressor characterization detachment allows also a better implementation of simplest models of the compressors in the thermal and fluid dynamic numerical simulation of vapour compressor cycles together with the rest of elements.

This dissertation deals with design of self adjustable discharge valve used in Emerson reciprocating compressors. This work contains research of current state of knowledge, technical analysis of the valve and calculations of basis parameters. Constructional proposal is then presented. Part of the dissertation is manufacturing of prototype and its test. Finally, conclusions for further development are made.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 128-130).
This thesis presents a set of techniques for non-intrusive sensing and fault detection in reciprocating compressors driven by induction motors. The procedures developed here are "non-intrusive" because they rely only on electrical measurements to reconstruct the mechanical signals internal to the compressor. This allows for easy and non-intrusive determination of many fault sensitive signals that usually require complicated, expensive, and time consuming operations to measure. A sample of the signals produced by the procedures of this thesis are estimates of the cylinder suction and discharge pressures and a composite torque signal containing the effects of the mechanical loads within the compressor. This load torque signal is especially sensitive to faults, and a demonstration of the effect on and detection of compressor valve faults from the load torque signal is given. One of the key steps in the algorithm presented here is a procedure to "invert" the induction motor dynamic model equations to allow direct calculation of motor shaft speed and torque from stator current and voltage measurements. For this procedure a non-intrusive method to estimate motor model parameters from an in-situ induction motor driving a periodic load was developed.
by Christopher James Schantz.
S.M.

The study of fluid film lubrication in mechanical components is fundamental to the analysis of their dynamic behaviour as well as determining friction losses between moving parts. In several cases, gases present in the system can interact with the oil changing lubrication characteristics - by their dissolution and release from the oil, forming bubbles or even producing foam. Additionally, in low pressure regions the lubricant loses the capacity to flow as a continuous film, and cavitation occurs. Generally cavitation is treated in numerical models via boundary conditions for the pressure equation, which is then used to solve the pr<;>blem only in the full film region instead of the whole solution domain. Several criteria are available, and the results are often sensitive to the chosen conditions. The present work proposes the study of cavitation considering the changes suffered by the lubricant as it flows through the lubricated component, considering the release of gas from the liquid and the existence of a two-phase flow. The numerical model treats the liquid-gas mixture as a homogeneous fluid, whose properties are calculated as weighted averages of the properties from the constituent phases. The model then solves the lubrication equation numerically using the finite volume methodology, considering variable fluid properties and without using any intermediate boundary conditions. The lubricant is considered a mixture of oil and refrigerant, widely studied due to its importance in lubrication and heat transfer problems in refrigeration systems. To advance in the understanding of the two-phase flow model, it was initially applied to simplified geometries, such as that of a partial journal bearing, and gradually the geometrical assumptions were relaxed, applying the model to a full journal bearing, where a . discussion against experimental results was possible. Finally, the problem of the reciprocating motion of the piston in a refrigeration compressor was considered. From the results, it is shown that the model can automatically predict three regions for the lubricated component,the positive pressure region, cavitation and pressure recovery. When the model is compared to solutions considering Reynolds boundary conditions, good agreement is observed for moderate and heavy loads. Studying the main operational parameters and the mixture behaviour, the discussion focuses on the fluid properties, which affect particularly density and as a result the cavitation region - or even the full bearing if bubbles are considered in all the bearing extent. Finally, in the light of the two-phase solution for piston lubrication, existing cavitation criteria for the problem seem inappropriate.

У роботі виконано розрахунок холодильного циклу та компресора, а також визначено вплив температур гарячого і холодного джерела оберненого циклу одноступеневої парокомпресійної холодильної машини на коефіцієнт перетворення циклу, а також на витратні і енергетичні характеристики компресора, що працює у його складі. У розділі охорони праці розглянуто шкідливі та небезпечні фактори, які виникають при експлуатації поршневих компресорів у холодильному виробництві
В работе выполнен расчет холодильного цикла и компрессора, а также определено влияние температур горячего и холодного источника обратного цикла одноступенчатой парокомпрессионные холодильной машины на коэффициент преобразования цикла, а также на расходные и энергетические характеристики компрессора, работающего в составе. В разделе охраны труда рассмотрены вредные и опасные факторы, возникающие при эксплуатации поршневых компрессоров в холодильном производстве
The work performed the calculation of the refrigeration cycle and the compressor, and also determined the influence of the temperatures of the hot and cold source of the reverse cycle of a single-stage vapor compression refrigeration machine on the cycle conversion factor, as well as on the consumption and energy characteristics of the compressor operating in the composition. In the section on labor protection, harmful and hazardous factors that arise during the operation of reciprocating compressors in refrigeration production are considered

The prefailure detection of faults in operating plant can effect major rewards in both safety and economy. A successful on-condition maintenance philosophy would pay great dividends particularly in the offshore oil industry where -until recently, only token methods have been employed. Many techniques are available for monitoring mechanical plant and several of these are considered in general terms. Industrial methods are subsequently evaluated on reciprocating compressor and rolling element bearing faults. Bearing fault analysis is considered in two stages. Initially, a series of vibration based techniques are evaluated on a large relatively noise free rotating machine. The techniques of greatest worth carrier spectra, autospectra, time signature analysis and statistical assessments - are then applied to bearings in the hostile environment of a reciprocating machine. It is shown that while discrete faults often produce predictable periodic vibrational patterns, a monitoring system aimed solely at such vibrational phenomena cannot be relied upon. To this end, a diagnostic system must encompass a series of techniques, including carrier spectrum, time signature and statistical analyses. A series of valve and piston faults in reciprocating machines are also studied. By using a number of monitoring techniques, a catalogue of fault characteristics is constructed, and the methods of greatest worth are high-lighted. It is noted that due to the complexities of a reciprocating machine, fault characteristics vary with load, and this must be borne in mind when interpreting the various parameter displays. No single technique can provide a complete cover for all compressor faults, and it is shown that those of greatest worth are acoustic emission, combined pressure and vibration plots, temperature and performance analysis. An indication of compressor temperature and internal cylinder pressure can greatly ease the detection and diagnostic process, and for the latter, bolt load determinations may be a valuable aid.

V posledních několika desetiletích se objevuje snaha o snížení firemních nákladů, stejně tak jako nákladů, které je nucen vynaložit zákazník, čímž se společnosti snaží získat výhodu vůči svým konkurentům na trhu. Spolu s tímto trendem jde i neustálá snaha snížit dopady na životní prostředí. Vývoj stávajících produktů se proto zdá být klíčovým prvkem. Tento dokument se zabývá vývojem pístového kompresoru na CO2 chladivo, který vyrábí společnost Emerson Climate Technologies. Cíl práce je zvýšit COP kompresoru při zachování stávající životnosti kompresoru. Diplomová práce je rozčleněna do několika kapitol, které se zabývají analýzou originálního designu kompresoru, návrhem a vyhodnocením designů nových. Nezbytné teoretické základy mohou být také shlédnuty v počátečních kapitolách. V poslední části dokumentu jsou sdělena možná další vylepšení a případné jiné konstrukce. Vývoj byl zaměřen na sestavu ventilové desky. Na základě několika předpokladů a výsledků analýzy původního designu kompresoru byly navrženy nové konstrukce, které byly dále testovány statickou strukturální analýzou. Pomoci modální analýzy byly také vypočteny vlastní frekvence a vlastní tvary sacího jazýčku. Mimo modální a statické strukturální analýzy byla provedena také CFD analýza. V posledním kroku byly testovány navržené prototypy a jejich výsledky byly porovnány s původním kompresorem. K správnému návrhu bylo zapotřebí programové podpory a to především v podobě MATLABu, ANSYSu WB a Microsoft Excelu. V práci jsou velmi často prezentovány obzvláště výsledky získané v programu ANSYS WB.

Orientador: Paulo Roberto Gabriel Kurka
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho tem como objetivo propor um modelo de dinâmica flexível dos componentes de um compressor alternativo monocilíndrico de refrigeração. Tal modelo representa um aperfeiçoamento da modelagem dinâmica utilizada, que supõe mancais rotativos fixos ou pinados. A modelagem dinâmica flexível do compressor é útil na analise dos esforços de natureza elástica e dissipativa que ocorrem nos mancais de sustentação do conjunto. Esses resultados podem também ser utilizados numa correta medição da energia dissipada pelos mancais. O modelo dinâmico utiliza um mecanismo biela-manivela, pistão e eixo, sujeitos ao carregamento da pressão que o fluido refrigerante exerce sobre o pistão no interior do cilindro. A modelagem incorpora efeitos giroscópicos e utiliza mancais flexíveis nos acoplamentos dos componentes, o que proporciona maior mobilidade ao modelo. O Método de Newton Euler é utilizado na analise das forças e momentos atuantes no sistema para a obtenção das equações diferenciais que representam o seu movimento. As equações dinâmicas, por sua vez, são resolvidas numericamente através do método de Runge-Kutta. Observou-se que a modelagem da oscilaãoo dos componentes rotativos no conjunto eixo-biela-manivela é capaz de produzir esforços diferenciados nos mancais do compressor quando comparado aos esforços de mancal presentes num modelo pinado
Abstract: The work consists in fiding a flexible dynamics model of a single cylinder, reciprocating refrigeration gas compressor. The model represents an improval to the current dynamic model of compressors, that use fixed or pinned rotation journal bearings. An efficient dynamic model of the compressor is useful in the analysis of elastic and dissipative loads that occur in the system¿s internal bearings. The results produced by the model can also be employed in the correct measurement of the energy dissipated at the bearings. The dynamic model consists of a rotor, cranckshaft, connecting rod and piston, all subject to the load from compression of the refrigerant fluid. The model incorporates gyroscopic effects and utilizes flexible bearing couplings, which yield greater mobilty to the moving mechanisms. The Newton-Euler method is used in the analysis of acting forces and torques, establishing the necessary differential equations that describe the movement of the system. A numerical solution of the dynamic equations is obtained through use of the Runge-Kutta method. Application of the model shows that oscillations of the rotating internal components of the compressor yield increased loads to the bearings, as compared to a pinned rotation model
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Doutor em Engenharia Mecânica

This research introduces a new method of diagnosing the internal condition of a reciprocating air compressor. Using only measured load torques and shaft dynamics, pressures, temperatures, flow rates, leakages, and heat transfer conditions are quantified to within 5%. The load torque acting on the rotor of the machine is shown to be a function of the dynamics (instantaneous position, velocity, and acceleration) of the driving shaft, the kinematic construction, and the internal condition of the machine. If the load torque, the kinematic construction of the machine, and the dynamics of the rotor are known, then the condition of the machine can be assessed. A theoretical model is developed to describe the physical behavior of the slider-crank mechanism and the shaft system. Solution techniques, which are based on the machine construction, crankshaft dynamics, and load torque measurements, are presented to determine the machine parameters. A personal computer based system used to measure the quantities necessary to solve for the machine parameters and the quantities used to compare with calculations is also documented. The solution algorithm for multi-stage compressors is verified by decoupling the load torque contributed by each cylinder. Pressure data for a four-stage two-cylinder high pressure air compressor (HPAC) is used. Also, the mathematical model is proven feasible by using measured angular velocity of the crankshaft and direct measurements of the load torque of a single stage, single cylinder air compressor to solve for the machine parameters. With this unintrusive and nondestructive method of quantifying the operating parameters, the cylinder pressures, operating temperatures, heat transfer conditions, leakage, and power consumption of a reciprocating air compressor can be evaluated.
Ph. D.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
Compressores de gás de grande porte são componentes fundamentais em plantas industriais de refino de petróleo, atuando principalmente como agentes fornecedores de energia mecânica aos processos químicos. Dentre os tipos de compressores, destacam-se os alternativos. Devido a exigências de processo químico e arranjo industrial, é comum a instalação desses equipamentos em estruturas aporticadas, fato que, associado às características do movimento de suas partes mecânicas, não raramente as cargas dinâmicas geradas provocam vibrações inadmissíveis. Neste trabalho é avaliado o comportamento dinâmico de um sistema formado por uma estrutura aporticada, por compressor alternativo, pela fundação em estacas e finalmente pelo próprio solo. O estudo paramétrico realizado se desenvolve a partir de uma análise de modelos simplificados massa-mola, de um modelo em elementos finitos e de medições de campo visando a estabelecer intervalos de valores dos parâmetros do solo local dentro dos quais se identifique as características da resposta dinâmica do sistema. São avaliados os parâmetros coeficiente de mola (km) e a constante do coeficiente de reação horizontal (nh) do solo natural típico da área abrangida pela refinaria REPAR, localizada no município de Araucária, no estado do Paraná, solo esse pertencente à formação geológica denominada Guabirotuba. A avaliação do comportamento dinâmico do sistema através dos modelos desenvolvidos é balizada por valores de medição na estrutura real de velocidades de vibração efetivas, obtidas por instrumentação. Os parâmetros do solo são obtidos por retroanálise de resultados de ensaio de campo, utilizando-se dois modelos amplamente utilizados nos escritórios de projeto: modelo proposto por Miche (1932) e modelo proposto por Hetenyi (1946). O primeiro considera que os parâmetros do solo variam com a profundidade, e o segundo os considera constante com a profundidade. Busca-se avaliar também a influência de parâmetros do solo obtidos através de ensaios de carregamento estático (ABNT NBR 12131, 2006) e obtidos através de ensaios de carregamento estático cíclico, este último se propondo a simular o efeito dinâmico sobre o solo. Finalmente, compara-se os resultados fornecidos pelos modelos simplificados e pelo modelo em elementos finitos em termos das freqüências naturais de vibração.
Gas compressors are key components of industrial plants in oil refining, mainly acting as mechanical energy suppliers to chemical processes. Among the types of compressors, the reciprocating ones is highlighted. Due to mandatory demands of chemical process and industrial arrangement, it is common to install such equipment in framed structures. This condition and the typical movement of mechanical parts of the compressors generate dynamic loads which frequently causes unacceptable vibrations. The aim of the present work is to evaluate the dynamic behavior of a system consisting of a framed structure, a reciprocating compressor, foundation in piles and the soil itself. For this purpose, parametric study is developed from simplified spring-mass models, a finite element model and field measurements. The parametric study is aimed at establish ranges of local soil parameters within which the dynamic behavior of a system can be understood and measured. The parameters so-called spring stiffness (km) and the constant coefficient of horizontal reaction (nh) of natural soil which typically occurs in the area covered by the REPAR refinery, located in Araucaria, Paraná, are then evaluated. This type of natural soils belongs to the geological formation called Guabirotuba. The evaluation of the dynamic behavior of the system through the developed models is benchmarked by field measurements of effective velocity of vibration in the actual structure, obtained by instrumentation. The soil parameters are obtained by back analysis of tests results by using two models widely used in design offices: model proposed by Miche (1932) and model proposed by Hetenyi (1946). The first one takes in account the variation of the soil parameters with depth, and the second one considers soil parameters constant with depth. The aim is also to evaluate the influence of the soil parameters obtained by static and cyclic horizontal loading tests, the latter being proposed to simulate the dynamic effect on the soil. Finally, it is done comparisons of the results provided by simplified models and the finite element model in terms of natural frequencies of vibration.

This thesis introduces the application of computer-aided engineering techniques to the dynamic analysis of reciprocating compressor designs. The analysis process is detailed in three steps. The first step, an interactive pre-processor, develops the shaking forces and torques acting on the machine. The second step is a batch processed program that performs a dynamic simulation of the compressor in operation. The compressor and mounting are simulated as a rigid body with six degrees-of-freedom (X, Y, and Z translations and roll, pitch, and yaw) mounted to the ground with up to 25 arbitrarily oriented springs and dampers. Additionally, an eigenanalysis is performed that returns the natural frequencies and modes for the machine. The final step is an interactive postprocessor where the user may examine the results of the eigenanalysis as well as the operating orbit of the machine. A series of programs that implement the analysis process was developed. The specialized formulations for the six coupled, non-linear equations of motion are presented. Color computer graphics and animation are used for visual output displays. The dynamic simulation program is designed to function on many computer systems, from low-cost personal computers to large mainframes, while the pre- and post-processing programs are designed for the personal computer. The programs were tested by comparing the predicted results with those of an Ingersoll-Rand model 242 two piston, two stage, 3 hp compressor. The correlation between the experimental and predicted results show that the programs can accurately simulate the dynamics of a reciprocating compressor operating at steady-state. Typically, the acceleration results agree for the six degrees-of-freedom in both the time and frequency domain to within 8%.
Master of Science

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A necessidade de novas metodologias para análise e monitoramento de compressores alternativos motivou o desenvolvimento de um sistema digital multicanal com capacidade de medir diferentes grandezas simultaneamente. Como base para este trabalho escolheu-se medir pressão dinâmica, vibração e deslocamento do pistão. O desenvolvimento deste trabalho dentro de um curso de Mecatrônica produziu um sistema simples e eficiente cujos resultados experimentais, apresentados sob a forma de gráficos e dados de desempenho, confirmaram os defeitos introduzidos artificialmente. Isto permitiu validar o Sistema de Diagnóstico de Compressores Alternativos (SDCA) e demonstrou o quanto este recurso é poderoso para o diagnóstico de defeitos, tanto nos componentes da parte de compressão (fluid end) quanto nos de acionamento (power end). Estas informações, transformadas em recomendações de reparo, serão a base para uma atuação preditiva dos setores de Planejamento de Manutenção.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
FAPEG - Fundação de Amparo à Pesquisa do Estado de Goiás
FAPEMIG - Fundação de Amparo a Pesquisa do Estado de Minas Gerais
Compressores herméticos alternativos são objetos de estudos de vários pesquisadores na busca do entendimento e redução do ruído. A análise de componentes independentes apresenta-se como uma atrativa ferramenta na identificação das fontes, com pouca ou nenhuma informação sobre as fontes e como são misturadas. Inicia-se o estudo e compreensão da ferramenta, e utilizam-se sinais conhecidos para reconhecer o processo e suas características. Dentre as técnicas analisadas observa-se que sinais de característica impulsiva são melhores recuperados com técnicas no domínio do tempo, enquanto sinais com característica harmônica apresentam melhor identificação no domínio da frequência, ainda alguns algoritmos destacam-se frente a outros e a adição da fonte de ruído melhora o índice de performance. Ao aplicar a técnica nos compressores verifica-se limitação às baixas frequências, região onde a diferença de fase entre os sinais é mínima e há correlação na sincronização dos sinais. Constatam-se duas componentes identificadas: desbalanceamento na frequência de 60 Hz e pulsação do gás nas regiões próximas a 500 Hz, para as três pressões de alimentação analisadas, vazio, 20 e 60 psi, relata-se que a pulsação do gás é melhor identifica para a pressão mais alta, enquanto na menor pressão há dificuldades em relacionar as componentes recuperadas com a fonte. Por fim, aliado ao método de elementos finitos estimam-se as contribuições das fontes recuperadas no nível de potência sonora do compressor.
Reciprocating hermetic compressors have been studied in several research programs aiming to noise reduction and understanding. The analysis of independent components is an important tool to allow identification of noise sources even without better information about their origin or how they had been mixed. The first stage of the present study is the tool understanding using known signal in order to figure out how the process is performed and its characteristics. Among the analyzed techniques, it was possible to observe that impulsive signals had been better recovered by time-domain techniques, while the harmonic signals had been better recovered by frequency-domain techniques. In addition, some algorithm stood out than other ones and extra noise source have improved performance results. When applying those mentioned techniques on the compressors, a limitation has been noticed in lower frequencies, because there is no phase difference between the analyzed signals and there is some correlation in signals syncing. Two components can be clearly identified, which are unbalanced forces at 60 Hz and gas pulsation for frequencies close to 500 Hz. The system has been tested on three different pressure levels: without any charge, 20 psi, and 60 psi. It has been found out that the gas pulsation can be better identified for the highest pressure level , while there is less correlation between the component and the signal for the lowest pressure level. Finally, the power pressure level contributions of recovered sources are estimated by a finite element method.
Tese (Doutorado)

碩士
國立彰化師範大學
電機工程學系
97
The main purpose of this research is to establish an automated compressor remote vibration monitoring system in order to monitor the main motor for the reciprocating compressor to do the bearing vibration monitoring. Our system uses the measurements of vibration displacement, velocity and acceleration to monitor equipment start-stop, alarm records, and records of numerical changes (trends) and display these data in the website page. The system can be the first time to send this message on the computer to tell operators the apparatus state. That is, the operator does not need to arrive at the scene, the problem can be solved, and then to achieve the best efficiency.

碩士
國立交通大學
機械工程系
89
The main purpose of this thesis is to develop a simulation code to describe the performance of a reciprocating compressor, whose working fluid is refrigerant. The mass conservation and energy conservation equations are applied to solve pressure, mass, and temperature of refrigerant in the compressor. To solve mass and energy conservation equations, a set of equations is needed. They are equations of state, orifice flow, cylinder volume, heat transfer, valve motion equations. some semi-empirical relations, such as orifice coefficient, convection heat transfer coefficient, geometric size of the compressor, material properties of the compressor, working fluid and operating conditions, are required as well. From the simulation, it can obtain the pressure, temperature and mass of the refrigerant as a function of crank angle for each control volume. From these data, many situations affecting reciprocating compressor performance can be identified. Those include the over-pressure in discharge period, under-pressure in suction period, motion of valve, refrigerant back-flow through orifice, and pre-heat of refrigerant before flowing into cylinder. A set of parametric study is carried out to see their influence on the compressor performance. Those varying parameters are the number of control volumes, the ratio of refrigerant directly flowing into suction muffle, the applications of real- and ideal-gas equation of state, inlet and outlet conditions, rotational speed of motor, spring coefficient of valve, and gap between piston and cylinder wall.

碩士
國立交通大學
機械工程系所
93
The goal of this study is to add an optimization module into one simulation software used in predicting the performance of the reciprocating compressor. This simulation software integrates the analysis of thermal and mechanism modules and simulates by using the computer numerical method. Based on the software program, the study incorporates the optimization module, including user interface and optimization solvers. The user interface can help defining, formulating and setting the optimization problem quickly. With this interface, the user can select design variables, cost function, and constraints freely and conveniently to reduce difficulties in linking between analysis and optimization software. The analysis module in the study is the comprehensive simulation software of the reciprocating compressor. The optimization solvers can contain certain ways providing the user to select. The valve optimization is a main theme for discussion in the study. The optimization module constructed in the simulation software as a useful tool help to aid optimum design of the reciprocating compressor.

碩士
國立交通大學
機械工程系
90
The goal of this study is to develop simulation software to describe the performance inside reciprocating compressor. Under the given compressor geometric size, material properties, motor characteristic, working fluid and operating conditions, the properties of the thermal and mechanism of the reciprocating compressor can be predicted by using the computer numerical analysis while the compressor operates actuality. The thermal analysis includes the solution of the pressure, temperature, and mass or other respective effect on compressor capacity and cylinder, while the mechanism analysis involves the dynamic forces analysis of the suction and discharge valves, the slider-crank mechanism, and the crankshaft part. The vibration analysis of the crankcase will also be discussed. It can vary each of the mechanism parameters and the refrigerant oil to know how the compressor efficiency changed form the results by using this software. Therefore, it can transfer the minute and complicated manual-analysis to rapidly computerizing analysis and treat the software as a computed aided analysis tool.

Metodologia avanzata per lo studio dell'interazione tra il compressore alternativo e la pipeline. Strumento per la stima delle prestazioni del compressore durante la fase iniziale di progettazione della macchina.

The quantification of pressure losses generated during the suction and discharge phases is essential to predict the working cycle of a reciprocating compressor. Beyond automatic valves, which are the main sources of fluid-dynamic losses, a relevant contribution is provided by all of the other components along the cylinder suction and discharge paths. Low-order numerical models for the simulation of the working cycle account for pressure losses through the imposition of global flow coefficients, which must be known from either experiments or three-dimensional CFD simulations. Therefore, the accuracy of the prediction of the absorbed power is strongly related to the methodology for the evaluation of the flow coefficients for all of the components. The geometrical features of the gas path have a great impact on the flow coefficient, which also depends on the piston motion during the cycle: indeed, the compression chamber shape, the pocket section and the flow pattern vary as a function of the piston position. Moreover, the valve and the working fluid used, as well as the operating conditions have a strong influence on the flow coefficient evaluation. For this reason, the number of configurations that should be simulated is extremely high and the evaluation of the pressure losses in the suction and discharge gas path with a 3D CFD steady state simulation is impossible without a substantial reduction of the set-up times and of the number of simulations. Within this scenario, the aim of this thesis is the introduction of a new methodology for the evaluation of the pressure losses occurring along the overall gas path in order to obtain a strong reduction of both the set-up and computational times for the realization of steady state CFD simulations. In more detail, the proposed approach starts by the idea to obtain the computational domain by means of parametric CAD models of the fluid domain directly without the need of starting from the more complex 3D drawings of the solid metal components and assemblies. This solution requires a greater initial effort for the realization of a parametric CAD model but allows an important reduction of the set-up times when simulating more cylinders starting from the same parametric model. The idea of the CFD routine described in this thesis is then to use parametric CAD models for the simulations of a large number of cylinders in order to reduce the global computational times. Indeed, the parameterization comprises also the mesh definition and the simulation setup phases, thus leading to a fully automatable approach. Nevertheless, even in case of exploiting the use of parametric models, the number of simulation cases that should be analyzed for each machine is still too high. For this reason, a detailed analysis was carried out to define the minimum number of simulations needed to obtain accurate results with the minimal computational times. Different solutions are then proposed in order to reduce the number of configurations to simulate; the evaluation of all the possible operating conditions of the large size reciprocating compressors analyzed in this thesis was obtained by means of 48 simulations for each machine. Moreover, the results obtained by the application of the defined approach to an industrial case are shown. In the second part, the utility of the simplified parametric routine to enhance the predictability in reciprocating compressors is highlighted by applying the results achieved to different numerical approaches. In particular, the effect of the approximations introduced in the flow coefficient evaluation on the performance prediction of large size reciprocating compressors is investigated. The numerical model used for the analysis is an in-house one-dimensional model based on the finite volume method (FVM). The study is carried out for three different compressor sizes and three different working gases, showing that the requirements in terms of flow coefficient accuracy depend on the specific case. The comparison between the numerical results using different flow coefficients and the measurements collected on a dedicated test bench allowed highlighting the importance to accurately predict the flow coefficient along the overall suction and discharge gas path. Moreover, a methodology to perform a 2D CFD simulation of the working cycle of a reciprocating compressor is developed in order to provide more accurate results than low-order models and, at the same time, to guarantee the reduction of the computational effort with respect to unsteady 3D CFD simulations. In more detail, the analysis presented in this work is carried out for a double-acting large bore cast iron cylinder. The simplifications required to allow the reduction of the three-dimensional fluid domain to an equivalent two-dimensional configuration are shown. In particular, the importance to use the flow coefficients obtained by means of the simplified CFD parametric routine for the pressure losses evaluation in the suction and discharge gas-path is highlighted. Finally, the possibility to use the parametric CFD routine to increase the predictability of the heat transfer process in a reciprocating compressor is shown. A brief description of a conjugate heat transfer (CHT) approach is given and the suitability to use the parametric routine for the forced convection modeling inside suction and discharge gas ducts is underlined. Furthermore, the utility of the parametric routine as well as the accuracy of both 2D and CHT models is highlighted by means of the comparison between the numerical results and the measurements collected during experimental campaigns.

碩士
國立彰化師範大學
機電工程學系
98
This research aims at the structure design on the dynamic characters of the air compressor. Because the size and shape of the structure materials of an air compressor will influence its whole strength, the bad structure will cause the vibration of an air compressor while it is working. This research tests the vibrations and noises of an air compressor first. Then the structure of compressor is analyzed by using the computer analyzing software. The data can provide the references of the compressor’s design of concerned manufacturers to improve its structure perfectly and shorten developing time and reducing wastage of cost. Keywords：Air Compressor, Vibrations, Noises, Structural Design

碩士
國立彰化師範大學
機電工程學系
96
Improving the vibration problem is the main goal of this study for finding the optimal crankshaft counterweight of the reciprocating compressor. Therefore this research mainly aims for designing the appropriate crankshaft counterweight with effective way to reduce the vibration for a commercial reciprocating compressor. As the counterweight reduces the kinetic orbit of crankshaft connecting rod, the decreasing unbalanced orbit corresponds to less vibration. First, we will establish an analytical model for computing the counterweight of the crank based on the dimension of air compressor and drive specifications. Design issue is created for a new crankshaft that fit the air compressor with vibration and noise requirements. Finite element software is used to simulate the modal and deformed situation under variant weight of the crank. Besides, spectrum analyzer for modal testing is introduced for analyzing signals from impulse hammer and accelerometer. Through analytical, simulation and experimentation, this research develops a complete process for crankshaft counterweight design. The designed crankshaft counterweight is implemented and verified through vibration reduction of 50.62%. Experimental result validates this research output.

碩士
國立交通大學
機械工程系所
95
The main purpose of this thesis is to develop a new refrigerant module into simulation software for reciprocating compressor. This window-based software, which integrates the thermal analysis modules, the mechanism modules, and optimization modules can be used to simulate the performance of the compressor numerically. Based on the original software from ITRI, the Fluid Thermodynamic and Transport Properties Database(REFPROP) developed by National Institute of Standards and Technology(NIST) is transferred into a refrigerant module with different refrigerants. Furthermore, the performance comparison between R134a, R600a and R600a&R290 were conducted with this software. Design parameters such as rotational speed, reed thickness, temperature of condenser and evaporator, and size of cylinder, were analyzed by this simulation software in order to establish bases for better designs of reciprocating compressors with different natural refrigerants.

碩士
國立彰化師範大學
機電工程學系
102
The purpose of this study is to suppress the problem of vibration which occurs in a running two-cylinder reciprocating compressor. Determining an optimal crankshaft counterweight and narrowing the trajectory orbit of the crankshaft connecting rod mechanism is achieved. First, we will select an analytical model for computing the counterweight of the crank based on the dimension of air compressor and drive specifications. Design issue is created for a new crankshaft that fit the air compressor with vibration requirements. Use of finite element software was used to simulate the modality of the two cylinders. In additions, the inertial force influenced to the crankshaft under different counterweight design was simulated. Simulation results by using Solid Works software show the new counterweight was able to reduce the crankshaft’s eccentric by 4mm and the orbit trajectory by 10mm. This study provides the procedures pertaining to the bettering performance and assessment for an existing reciprocating compressor.

碩士
國立高雄科技大學
環境與安全衛生工程系
107
Human industrial activities use fossil fuels, such as coal and oil, to produce a large amount of carbon dioxide emissions into the atmosphere, causing atmospheric greenhouse effects; in the atmosphere a thousand years before the industrial revolution, the atmosphere The carbon dioxide content is maintained at about 280 ppm (i.e., 280 unit volumes of carbon dioxide in one million units of gas). After the industrial revolution, after the 1950s, the rate of increase was faster. By 1995, the concentration had reached 358 ppm[1]. The petrochemical industry plays a pivotal role in Taiwan's economic contribution, but it also causes a lot of pollution to the air. Therefore, the government's requirements for environmental protection are also increasing year by year, to improve the existing equipment to reduce energy consumption in response to the trend of world environmental protection. The energy recycling and reuse equipment will be added, and the new process will be developed towards the goal of energy recycling and high energy consumption and low energy consumption. The hydrodesulfurization workshop in the petrochemical plant is a factory set up in response to environmental protection requirements. The purpose is to reduce the sulfur content of the oil and reduce the sulfur oxides of the air. A heavy oil hydrodesulfurization workshop introduced “no segment capacity” in 2016. The control system improves the capacity adjustment of the hydrogen reciprocating compressor in the hydrodesulfurization workshop, replaces the previous sectional capacity control with the stepless control method, improves the work efficiency of the reciprocating compressor, and achieves the purpose of energy-saving and carbon reduction This study evaluates the difference between pre-improvement and post-improvement through theoretical estimation and actual operation data collection and evaluates whether the investment equipment meets the legal carbon emission exchange method and benefits. The HOERBIGER company’s HydroCOM stepless capacity control system estimates the 75% load based on the relationship between the 0%~100% load of the reciprocating compressor and the indicated power, and the energy-saving evaluation performed in the case of 8,000 hours of operation per year. There is a big difference between the actual and recorded current and target current, which is very unreasonable.

Modellazione ibrida tempo-frequenza per analisi di compressori alternativi e rispettivi impianti. L'approccio consente di valutare l'interazione tra la macchina e l'impianto. Al fine di modellare in dettaglio le cavità complesse della macchina, è stata definita ed applicata una procedura di caratterizzazione basata su risultati di simulazioni realizzate con FEM acustico. La metodologia di modellazione è stata applicata ad un compressore per cicli frigoriferi a CO2 e verificata attraverso il confronto con dati sperimentali. An accurate and effective numerical modelling of the reciprocating compressors in the preliminary phase of design can assure reliability in the operating conditions and avoid failures. In most cases, the geometric complexity of some elements interacting with the compressor, such as plena and mufflers, makes both the fluid-dynamic 1D and acoustic lumped parameters modelling of the system unable to assure the required detail level necessary for the design process. For this reason, an acoustic numerical characterization is the most suitable way for the analysis of the response of geometrically complex elements. In order to analyze the thermodynamic and acoustic performance of a compressor for refrigerating application, a hybrid numerical model is developed that allows to carry out simultaneously the time-domain analysis of the compressor thermodynamic cycle and the frequency-domain acoustic analysis of the pipelines system. An acoustic characterization method based on acoustic FEM simulation results was also defined to model in detail the compressor cavities with complex geometries (i.e. compressor plena). The results of the compressor hybrid model with both acoustic FEM characterization and acoustic lumped elements were compared with experimental measurements. Moreover, a comparison between the developed hybrid model and the stand-alone compressor model with constant pressure boundary conditions was carried out. The advantages in using the acoustic FEM characterization of the complex geometry elements were highlighted.