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Dissertations / Theses on the topic 'Heat-engines'
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1
Barr, William Gerald. "Low heat rejection diesel engines." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254429.
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Bardaweel, Hamzeh Khalid. "Dynamic characterization of a micro heat engine." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/H_Bardaweel_110107.pdf.
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Baird, A. J. "Heat Transfer from Air Cooled Engines." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517206.
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Lee, Victoria D. Lee (Victoria Dawn). "Waste heat reclamation in aircraft engines." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/97318.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 94-96).
Introduction: Rotorcraft engines can lose up to 70% of the potential chemical energy of their fuel as waste heat. Harvesting this waste heat and converting it to useful work would improve the efficiency and power output of the engine. Figure 1 shows two possible engine systems in which a secondary engine could be used to harvest waste heat. For the gas turbine engine in Figure 1A, the main source of waste heat is the enthalpy of the engine's exhaust gases. In the case of the spark ignition engine in Figure 1B, there are three sources of waste heat: the enthalpy available in the exhaust gases, the heat rejected by the coolant loop, and the heat rejected by the oil loop. For each engine system, the heat from waste heat engine is rejected to the ambient air. Possible candidate systems for waste heat recovery include closed cycle systems such as the Rankine and Brayton engines. Rankine engines typical use water as a working fluid. The performance of water-based Rankine engines suffer from low pressures in the working fluid at the temperatures of the ambient and, therefore, require large low pressure expanders and condensers to operate efficiently. Organic working fluids have higher vapor pressures and can be used in Rankine engines instead of water. The higher vapor pressures of these fluids allow the use of smaller expanders. However, organic working fluids are limited to temperatures below 250 C, which is substantially lower than the typical temperatures available in the waste streams. Brayton engines can operate at higher temperatures using inert gases such as helium and argon as working fluids. In either of these engines, the turbomachinery and heat exchangers must remain leak tight as the working fluid is cycled through at high temperatures and high pressures. As a consequence of this requirement, these cycles will not be considered further in this work. Thermoelectric devices, on the other hand, do not require leak tight passages or turbomachinery. These are compacted and are expected to have a higher reliability since they have no moving parts. These advantages have motivated this study on thermoelectrically-based waste heat engine. For a thermoelectrically-based waste heat engine to be feasible, it must be capable of absorbing and rejecting large amounts of heat in part to compensate for the low efficiencies of thermoelectric materials. It must also be light weight and compact to address concerns of power to weight ratios and space constraints in rotorcraft. Therefore, the waste heat engine must be designed to minimize thermal resistance while also minimizing the mass and volume of the heat exchangers.
by Victoria D. Lee.
S.M.
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Clarke, Ralph Henry. "Heat losses in internal combustion engines." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/8290.
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Bibliography: leaves 119-121.This thesis deals with the effects of cooling and heat losses in internal combustion engines. The object of this work was to examine and research various cooling concepts and methods to reduce heat loss to engine coolant, improve thermal efficiency and to predict heat transfer values for these alternatives. The optimum system to be considered for possible application to small rural stationary engines. A literature survey was undertaken, covering work performed in the field of internal combustion engine cooling. Besides the conventional cooling system, two concepts emerged for consideration. These were the precision cooling system and the new heat pipe concept, the latter being relatively unknown for internal combustion cooling application. The precision cooling system, consists of a series of small bore tubes conducting coolant only to the critical areas of an engine. The theory being that in the conventional systems many regions are overcooled, resulting in excessive heat loss. The heat pipe is a device of very high thermal conductance and normally consists of a sealed tube containing a small quantity of fluid. Under operating conditions the tubular container becomes an evaporator region in the heat input area and a condenser region in the heat-out area. It is therefore basically a thermal flux transformer,attached to the object to be cooled. The heat pipe performance is also capable of being modulated by varying its system pressure. This is a positive feature for internal combustion engine application in controlling detonation and NOx emissions. Various facts were obtained from the literature survey and considered in the theoretical review. These facts were extended into models, predicting the heat transfer performance of each concept in terms of coolant heat outflow and heat transfer coefficients. The experimental apparatus was based on an automotive cylinder head with heated oil passing through the combustion chamber and exhaust port to simulate combustion gases. Experiments were conducted on this apparatus to validate the predicted theoretical performance of the three concepts. Tests were also made to observe the effect of heat pipe modulation and nucleate boiling in the precision system. Concept theory was validated as shown by the experimental and test results. The performance for each system approximated the predicted heat transfer and heat loss values. By comparison of the heat input, coolant heat outflow values and heat transfer coefficients it was found that the precision system was the most efficient, followed by the heat pipe and the conventional system being the least efficient. It was concluded that the heat loss tests provided a valuable insight into the heat transfer phenomenon as applied to the three systems investigated. This work also illustrated the effects of the variation of coolant flow, velocity and influence of nucleate boiling. This thesis has shown the potential of the systems tested, for controlling heat losses in internal combustion engines. The research work has created a data base for further in-depth evaluation and development of the heat pipe and the precision cooling system. Based on the findings of the experimental work done on this project, several commercial applications exist for the heat pipe and precision cooling systems. Further in-depth research is recommended to extend their potential in the automotive industry.
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Finger, Erik J. "Two-stage heat engine for converting waste heat to useful work." online access from Digital Dissertation Consortium, 2005. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3186905.
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Gidugu, Praveen. "Effect of adding a regenerator to Kornhauser's MIT "two-space" test rig." Cleveland, Ohio : Cleveland State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1212595450.
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Thesis (M.S.)--Cleveland State University, 2008.Abstract. Title from PDF t.p. (viewed on July 9, 2008). Includes bibliographical references (p. 100-103). Available online via the OhioLINK ETD Center. Also available in print.
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Lemaire, Lacey-Lynne. "Miniaturized stirling engines for waste heat recovery." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107690.
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Portable electronic devices have made a profound impact on our society and economy due to their widespread use for computation, communications, and entertainment. The performance and autonomy of these devices can be greatly improved if their operation can be powered using energy that is harvested from the ambient environment. As a step towards that goal, this thesis explored the feasibility of developing miniaturized Stirling engines for harvesting waste heat. A mesoscale (palmtop-size) gamma-type Stirling engine, with a total volume of about 165 cubic centimeters, was manufactured using conventional machining techniques. The engine was able to sustain steady-state operation at relatively low temperature differentials (between 20 degrees Celsius and 100 degrees Celsius) and generated a few millijoules of mechanical energy at frequencies ranging from 200 to 500 revolutions per minute. Subsequently, the gamma-type engine was transformed into a Ringbom engine; and its operation was compared with the predictions of an analytical model available in the literature. The experience gained from these studies provides some guidelines for further miniaturization of Stirling engines using microfabrication technologies.Les appareils électroniques portatifs ont définitivement laissé un impact sur notre société et économie par leur utilisation fréquente pour le calcul, les communications et le divertissement. La performance et l'autonomie de ces appareils peuvent s'améliorer grandement si leur exploitation fonctionne en utilisant l'énergie récoltée de l'environnement. Pour s'orienter vers ce but, cette thèse a exploré si le développement d'un moteur Stirling fonctionnant sur l'énergie résiduelle était faisable. Un moteur Stirling de configuration 'gamma', de la grandeur d'une paume de main, avec un volume d'environ 165 centimètres cubes, a été fabriqué en utilisant des techniques conventionnelles d'usinage. Ce moteur a été capable de soutenir l'opération constante et stable à des différences en température relativement basses (entre 20 degrés Celsius et 100 degrés Celsius). De plus, il a produit quelques milli-Joules d'énergie mécanique à des fréquences entre 200 et 500 révolutions par minute. Par la suite, le moteur Stirling de configuration 'gamma' a été transformé en un moteur Ringbom. Par après, l'opération de ce moteur a été comparée à des prédictions basées sur un modèle analytique disponible dans la littérature. Les informations recueillies durant cette étude ont fourni certaines directives pour la miniaturisation éventuelle d'un moteur Stirling en utilisant des techniques de microfabrication.
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Boswell, Michael John. "Gas engines for domestic engine-driven heat pumps." Thesis, Oxford Brookes University, 1992. http://radar.brookes.ac.uk/radar/items/37f7ed18-4b86-6ab3-8ba6-1c27947fb1ce/1.
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An experimental and theoretical investigation has been undertaken into the performance of a small prototype, water-cooled, gas-fuelled engine designed for use as a domestic heat pump prime mover. In light of the application, fuel type and capacity, both experimental and theoretical study of similar engines is at best poorly documented in the literature. A comprehensive engine test facility has been set up, incorporating extensive calorimetry, a separate lubrication system, emissions monitoring and high speed data acquisition for in-cylinder pressure measurement and analysis. Two new experimental cylinder heads have been designed together with new induction and exhaust systems, both to improve performance and to enable further investigation of the combustion process. A preliminary parametric study of the combustion process established that the thermal efficiency and emission levels are strongly dependent on operational and design variables and that a lean, fast-burning combustion process in a slow speed engine coupled with careful control of other operating variables had the potential for improving efficiency, reducing emissions, and lowering frictional losses and noise levels with enhanced durability. Accordingly, new information has been obtained relating to rates of heat release, energy flows and emission levels over a wide range of design and operating conditions with utility for and consistent with an envelope of conditions appropriate to such a lean burn strategy. Modelling techniques have been developed and used as diagnostic tools in conjunction with the experimental data to investigate the influence of operating and design variables on rates of heat release and energy flows. The models have been validated using the experimental data over a wide range of operating conditions and incorporated into a thermodynamic engine model for use as a sub-model in an overall heat pump model. The experimental and theoretical programme has provided a valuable insight into the lean burn strategy and realised a considerable improvement in the performance of the prototype engine. The theoretical study benefits from a new approach to small gas engine design and development.
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Villalta, Lara David. "RADIATION HEAT TRANSFER IN DIRECT-INJECTION DIESEL ENGINES." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/114793.
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En las últimas décadas, la investigación en motores de combustión ha estado enfocada fundamentalmente en la reducción de las emisiones contaminantes y la eficiencia de los mismos. Estos hechos junto con un aumento de la concienciación sobre el cambio climático han llevado a un aumento en la importancia de la eficiencia térmica respecto a otros criterios en el diseño de motores de combustión interna (MCIA). Para alcanzar este objetivo, existen diferentes estrategias a aplicar. En concreto, la transferencia de calor a las paredes de la cámara de combustión puede ser considerada como una de las principales fuentes de disminución de la eficiencia indicada. En particular, en los modernos motores diésel de inyección directa, la emisión de radiación de las partículas de hollín puede constituir un componente importante de las pérdidas de eficiencia. En este contexto se enmarca el objetivo principal de la tesis: contribuir a la comprensión de la transferencia de calor por radiación en la combustión diésel de inyección directa junto con la mejora del conocimiento en el proceso de formación-oxidación de hollín. El trabajo se ha basado tanto en resultados experimentales mediante la aplicación de técnicas ópticas en diversas tipologías de motor como en resultados simulados a partir de modelos unidimensionales validados.
En la primera parte de resultados experimentales, se ha evaluado la cantidad de energía por radiación respecto a la energía química del combustible mediante la aplicación de una sonda optoelectrónica (basada en la técnica del 2-Colores) tanto en un motor óptico DI como en motor poli-cilíndrico DI de producción. En este estudio se han obtenido valores de intensidad espectral emitida por el hollín y posteriormente, la radiación total emitida por las partículas de hollín en todo el espectro.
Como se ha citado anteriormente, las partículas de hollín son las principales responsables de la transferencia de calor por radiación, además de uno de los principales agentes contaminantes emitidos por los motores diésel. Las emisiones de hollín son el resultado de dos procesos antagonistas: la formación y oxidación del hollín. Los mecanismos de formación de hollín se discuten extensamente en la literatura. Sin embargo, existen deficiencias en cuanto al conocimiento de la oxidación de hollín. Por lo tanto, el objetivo de esta sección ha sido evaluar el impacto del proceso de mezcla y la temperatura del gas sobre el proceso de oxidación de hollín durante la última parte de la combustión bajo condiciones reales de operación.
Finalmente, y en base a los resultados y conocimientos adquiridos hasta el momento, se ha desarrollado un modelo capaz de predecir las pérdidas de calor por radiación para un chorro diésel. El modelo está basado en tres sub-modelos: modelo de chorro, el cual analiza y caracteriza la estructura interna del chorro en términos de mezcla y combustión en un proceso de inyección con resolución temporal y espacial. Un modelo de hollín, en el que los resultados se justifican en función de procesos de formación y oxidación del hollín. La cohesión de estos dos sub-modelos se utiliza para obtener los valores de entrada al modelo de radiación, con el que se obtiene los valores de transferencia de calor por radiación para una llama diésel.En els últims anys, la recerca en motors de combustió ha estat focalitzada principalment en la reducció de les emissions contaminants i la millora de la eficiència. Aquests fets afegits al fet del augment de la conscienciació del canvi climàtic han impulsat el interés per incrementar la eficiència tèrmica per damunt de altres criteris en el disseny de motors de combustió interna alternatius (MCIA). Per aconseguir aquest objectiu, existixen diferents estratègies a aplicar. Concretament, la transferència de calor a les parets de la càmera de combustió pot ser considerada un dels principals focs de reducció de eficiència indicada. En particular, en els moderns motors dièsel de injecció directa, la emissió de radiació de les partícules de sutja pot constituir un component important de les pèrdues de eficiència. En aquest context s'emmarca el objectiu principal de la tesis: contribuir a la comprensió de la transferència de calor per radiació en la combustió dièsel de injecció directa i la millora del coneixement del procés de formació-oxidació de la sutja. El treball esta basat tant en resultats experimentals mediant l'aplicació de tècniques òptiques en diverses tipologies de motor com en resultants simulats a partir de models unidimensionals validats. En la primera part dels resultats experimentals, s'ha avaluat la quantitat de energia per radiació respecte a la energia química del combustible mediant la aplicació de una sonda optoelectrònica (basada en la tècnica del 2-Colors) tant en un motor òptic DI com en un motor poli-cilíndric DI de producció en serie. En aquest estudi s'han obtingut valors de intensitat espectral emesa per la sutja i posteriorment, la radiació total emesa per les partícules de sutja en tot el espectre. Com s'ha citat amb anterioritat, les partícules de sutja son les principals responsables de la transferència de calor per radiació, a més de un del principals agents contaminants emès per els motors dièsel. Les emissions de sutja son el resultat de dos processos antagonistes: la formació i la oxidació de sutja. Els mecanismes de formació de sutja es discuteixen àmpliament en la literatura. No obstant això, existeixen deficiències pel que fa al coneixement de l'oxidació de sutja. Per tant, l'objectiu d'aquesta secció ha sigut avaluar l'impacte del procés de mescla i la temperatura del gas sobre el procés d'oxidació de sutja durant l'última part de la combustió sota condicions reals d'operació. Finalment, i en base als resultats i coneixements adquirits fins aquest moment, s'ha desenvolupat un model que permet predir les perdudes de calor però radiació per a un raig dièsel. El model esta basat en tres sub-models: model de raig, el qual analitza i caracteritza la estructura interna del raig en termes de mescla i combustió en un procés de injecció amb resolució temporal i espacial. Un model de sutja, en el qual els resultats es justifiquen en funció del procés de formació i oxidació de la sutja. La cohesió d'aquests dos sub-models s'utilitza per obtindre els valors d'entrada al model de radiació, amb el que s'obté els valors de transferència de calor per radiació per a una flama dièsel.
In the last two decades engine research has been mainly focused on reducing pollutant emissions and increasing efficiency. These facts together with growing awareness about the impacts of climate change are leading to an increase in the importance of thermal efficiency over other criteria in the design of internal combustion engines (ICE). To achieve the objective, there are different strategies to apply. The heat transfer to the combustion chamber walls can be considered as one of the main sources of indicated efficiency diminution. In particular, in modern direct-injection diesel engines, the radiation emission from soot particles can constitute a significant component of the efficiency losses. In this context, the main objective of the thesis is framed: to contribute to the understanding of the radiation heat transfer in DI diesel combustion together with the improvement of the knowledge in the soot formation-oxidation processes. The work has been based on experimental results through the optical technique application in different types of engine and on simulated results from validated one-dimensional models. In the first part of experimental results, the amount of energy lost to soot radiation relative to the input fuel chemical energy has been evaluated by means of the optoelectronic probe application (based on the 2-Color technique) in both an optical engine DI and a production 4-cylinder DI engine. In this study, the values of soot spectral intensity emitted have been obtained and later, the total radiation emitted by the soot particles in the whole spectrum. As mentioned above, soot particles are the main responsible for the radiation heat transfer, in addition to one of the important concern in meeting emissions regulations. Soot emissions are the result of two competing processes: soot formation and soot oxidation. Mechanisms of soot formation are discussed extensively in the literature. However, there are deficiencies in the knowledge of soot oxidation. Therefore, the objective of this section has been to evaluate the impact of mixing process and bulk gas temperature on late-cycle soot oxidation process under real operating conditions. Finally, based on the results and knowledge acquired, a model able to predict heat losses by radiation for a spray diesel has been developed. The model is based on three sub-models: spray model, which analyzes and characterizes the internal spray structure in terms of mixing and combustion process with temporal and spatial resolution. A soot model, in which the results have been justified according to soot formation and oxidation processes. The link of these two sub-models has been used to obtain the input values to the radiation model, which the radiation heat transfer values for a diesel flame are obtained.
Villalta Lara, D. (2018). RADIATION HEAT TRANSFER IN DIRECT-INJECTION DIESEL ENGINES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114793
TESIS
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Koll, Daniel D. B., and Thaddeus D. Komacek. "Atmospheric Circulations of Hot Jupiters as Planetary Heat Engines." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627038.
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Because of their intense incident stellar irradiation and likely tidally locked spin states, hot Jupiters are expected to have wind speeds that approach or exceed the speed of sound. In this work, we develop a theory to explain the magnitude of these winds. We model hot Jupiters as planetary heat engines and show that hot Jupiters are always less efficient than an ideal Carnot engine. Next, we demonstrate that our predicted wind speeds match those from three-dimensional numerical simulations over a broad range of parameters. Finally, we use our theory to evaluate how well different drag mechanisms can match the wind speeds observed with Doppler spectroscopy for HD 189733b and HD 209458b. We find that magnetic drag is potentially too weak to match the observations for HD 189733b, but is compatible with the observations for HD 209458b. In contrast, shear instabilities and/or shocks are compatible with both observations. Furthermore, the two mechanisms predict different wind speed trends for hotter and colder planets than currently observed. As a result, we propose that a wider range of Doppler observations could reveal multiple drag mechanisms at play across different hot Jupiters.
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Clark, David Anthony. "High performance heat engines for solar and biomass applications." Thesis, Queensland University of Technology, 1993. https://eprints.qut.edu.au/226903/1/T%28BE%26E%29%20375_Clark_1993.pdf.
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Generation systems which are fuelled by renewable energy sources, such as solar
and biomass, are the environmentally-preferred option for the production
of electricity and heat. This study examines the technical and economic feasibility
of small-scale (less than 1 MW) renewable generation systems based on
a steam-driven engine. Specifically, the study investigates the thermodynamic
and mechanical design of the engine.
The theory of engine operation is presented in Chapter 3 of this thesis. A
computor model of the engine was used to predict the performance of different
engine configurations. The model, although thermodynamically correct, did not
consider the effect of valve dynamics on engine performance.
Appendix 1 contains sample engine analyses based on the theory of engine
operation. From the calculations, it can be seen that valve dynamics has a
significant effect on engine throughput, efficiency and operating pressure. For a
given engine configuration with set mass flow and thermal input, valve dynamics
alters inlet valve timing and delays closure. This causes a reduction in efficiency
and peak operating pressure.
The suitability of ceramics or hardened-tool steels as steam inlet valves is discussed
in Chapter 4. A magnesia partially-stabilised zirconia ball was tested
for several hours in a single-cylinder engine.
A purpose-built engine test facility was used to obtain data on the variation
in the cylinder pressure throughout an engine cycle. The experimental work
highlighted several areas associated with the design of the inlet valve and steam
supply system where improvements could be made. During tests, the engine
was able to achieve conversion efficiencies greater than 20% heat-in to shaft-out.
A solar or biomass-fired generation facility can be operated and maintained by
persons with basic technical skills and requires less maintenance and attention
than diesel generators. Based on the cunent engine efficiency and the eff ectiveness
of other system c_omponents, the expected overall economics of engine-based power generation compares favourably with the traditional diesel-based
systems currently used in remote areas of Australia and overseas.
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Reid, Robert Stowers. "Open cyclic thermoacoustics." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15850.
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Savur, Mehmet Koray. "A numerical study of combined convective and radiative heat transfer in a rocket engine combustion chamber." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FSavur.pdf.
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Leathard, Matthew James. "Computational modelling of coolant heat transfer in internal combustion engines." Thesis, University of Bath, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248102.
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Ruiz, Joaquin G. 1981. "Waste heat recovery in automobile engines : potential solutions and benefits." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32832.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 32-33).
Less than 30% of the energy in a gallon of gasoline reaches the wheels of a typical car; most of the remaining energy is lost as heat. Since most of the energy consumed by an internal combustion engine is wasted, capturing much of that wasted energy can provide a large increase in energy efficiency. For example, a typical engine producing 100 kilowatts of driveshaft power expels 68 kilowatts of heat energy through the radiator and 136 kilowatts through the exhaust. The possibilities of where and how to capture this lost energy are examined in this paper. The solution of recovering heat energy from the exhaust through the catalytic converter with a Stirling engine was examined due to its practicality. A novel approach for combining a Stirling engine and a catalytic converter that would be effective was designed. The power output and efficiency of the Stirling Engine were analyzed and it was found that the average overall car efficiency could be raised 7% with the new design.
by Joaquin G. Ruiz.
S.B.
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Ragozin, Konstantin. "Thrust Performance and Heat Load Modelling of Pulse Detonation Engines." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-82438.
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Pulse Detonation Engines (PDEs) are propulsion systems that use repeated detonations to generate thrust. Currently in early stages of development, PDEs have been theorised to have advantages over current deflagration based engines. Air-breathing PDEs could attain higher specific impulse values and operate at higher Mach numbers than today's air-breathing engines, while Pulse Detonation Rocket Engines (PDREs) could become a lighter, cheaper, and more reliable alternative to traditional rocket engines. There are still however, many technological hurdles to overcome before PDEs can be developed into practical propulsion systems, one major barrier being management of their immense heat loads. This thesis outlines the development of a numerical model for determining thrust performance and heat load characteristics of PDEs. The model is based on a set of analytical equations which characterise the gas dynamics inside the engine throughout it's cyclic process. Being numerically light -when compared to CFD analysis- the model allows for fast turnaround of results and the ability to sweep through parameters to determine optimum operating conditions to maximise engine performance and reduce heat load. In this study, the working principles of the model are described and it's outputs are validated against data from published experimental and numerical studies. The model is then used to conduct a comprehensive parametric study on the effects of various reactant combinations, operating conditions, and engine geometries on engine thrust, specific impulse and heat load. Lastly, a brief study is conducted on the feasibility of regenerative cooling for PDEs, using model outputs to determine if a heat balance can be achieved and the performance losses and complications that would result.
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Kwan, Pok Wang. "Flow management in heat exchanger installations for intercooled turbofan engines." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711622.
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Melia, Thomas. "Heat transfer characteristics of pulse combustors for gas turbine engines." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10278.
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Conventional gas turbine combustors operate with a designed drop in pressure over the length of the device. This is desired in order to encourage mixing within the combustor. Compared to this, pulse pressure gain combustors are an alternative to the conventional combustor that produces an increase in static pressure between the inlet and exhaust of the device. The removal of the combustor pressure loss increases the efficiency of the combustion process by increasing the amount of work produced. Many types of pulsed pressure gain combustors exist. Of these, the valveless pulse combustor is the simplest featuring no moving parts. Whilst some research has been conducted into investigating the performance and workings of a pulse combustor, little has been conducted with the view of cooling the combustor. This has been the focus for the research contained herein. The research has focussed on establishing an understanding of the heat transfer characteristics within a pulse combustor tailpipe. This has involved experimental, analytical and computational research on a pulse combustor as well as on a cold-flow model of a pulse combustor tailpipe. This has enabled a study into the feasibility of cooling a pulse combustor to be conducted. The research has found that for conditions where the unsteady velocity amplitude within the cold-flow model of the pulse combustor tailpipe exceeds the mean velocity, an enhancement to the heat transfer coefficient is measured compared to the value expected in a similar non-oscillating flow. When there is no enhancement to the heat transfer coefficient, the cyclic variation of the unsteady heat flux follows the variation of the unsteady pressure within the device. However, at times of enhancement, the instantaneous heat flux structure shows a large deviation from the structure of the pressure field driving the oscillations. This change is shown to be caused by the reversal in the near-wall velocity and may indicate a mechanism for the enhancement in the mean heat flux. The cooling feasibility study showed that with further investigation, it may be possible to cool a pulse combustor within a gas turbine engine.
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Trujillo, Alba Marcela Herrera. "Quantum heat engines and energy fluctuations in many-body systems." reponame:Repositório Institucional da UFABC, 2017.
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Stowe, Robert Alan. "Heat transfer from a circular cylinder subject to an oscillating crossflow as in a stirling engine regenerator." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26741.
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An experiment was designed and carried out on the fundamental, but poorly understood problem of oscillating flow past a single, transverse, circular cylinder. This is an approximation of the flow about a single element in a matrix-type regenerator used in Stirling-cycle engines. The experimental rig was designed and built to allow tests to be carried out for the wide range of fluid flow parameters characteristic of various Stirling engines. The influence of these parameters on convective heat transfer rates was measured so the approximate effects of these same parameters on a Stirling engine regenerator could be determined. The main conclusion from the experiment was that average Nusselt numbers, based on test-cylinder diameter and subject to flow conditions similar to those found in Stirling engine regenerators, were 40 to 80% higher than those predicted by a steady flow correlation, for a given Reynolds number. This may be due to the high levels of turbulence generated near the test-cylinder. A secondary conclusion is that the compression and expansion of the working fluid due to a 90 degree phase angle difference between the motion of the pistons raises convective heat transfer rates from the test-cylinder substantially over the 180 degree phase angle, or "sloshing" motion case.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Weiss, Leland W. "A novel MEMS-based micro heat engine and operating cycle." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Dissertations/Spring2008/L_Weiss_041708.pdf.
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Hoegel, Benedikt. "Thermodynamics-based design of stirling engines for low-temperature heat sources." Thesis, University of Canterbury. Mechanical Engineering, 2014. http://hdl.handle.net/10092/9344.
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Large amounts of energy from heat sources such as waste-eat and geothermal energy are available worldwide but their potential for useful power-generation is largely untapped. This is because they are relatively low temperature difference (LTD) sources, in the range from 100 to 200 °C, and it is thermodynamically diffcult, for theoretical and practical reasons, to extract useful work at these temperatures. This work explores the suitability of a Stirling engine (SE) to exploit these heat sources. Elsewhere much work has been done to optimise Stirling engines for high temperature heat sources, but little is known about suitable engine layouts, and their optimal design and operational aspects at lower temperature differences. With the reduced temperature difference, changes from conventional engine designs become necessary and robust solutions for this novel application have to be identified.
This has been achieved in four major steps: identification of a suitable engine type; thermodynamic optimisation of operating and engine parameters; optimisation of mechanical efficiency; and the development of conceptual designs for the engine and its components informed by the preceding analysis. For the optimisation of engine and operating parameters a model was set up in the commercial Stirling software package, Sage, which also has been validated in this thesis; suitable parameter combinations have been identified.
This work makes key contributions in several areas. This first is the identification of methods for better simulating the thermodynamic behaviour of these engines. At low temperature differences the performance of Stirling engines is very sensitive to losses by fluid friction (and thus frequency), adiabatic temperature rise during compression, and the heat transfer from and to the surroundings. Consequently the usual isothermal analytical approaches produce results that can be misleading. It is necessary to use a non-isothermal approach, and the work shows how this may be achieved.
A second contribution is the identification of the important design variables and their causal effects on system performance. The primary design variable is engine layout. For an engine having inherently low efficiency due to the low temperature difference it is important to choose the engine layout that provides the highest power density possible in order to minimise engine size and to save costs. From this analysis the double-acting alpha-type configuration has been identified as being the most suitable, as opposed to the beta or gamma configurations. An-other key design variable is working fluid, and the results identify helium and hydrogen as suitable, and air and nitrogen as unsuitable. Frequency and phase angle are other design variables, and the work identifies favourable values. A sensitivity analysis identifies the phase angle, regenerator porosity, and temperature levels as the most sensitive parameters for power and efficiency. It has also been shown that the compression work in low-temperature difference Stirling engines is of similar magnitude as the expansion work. By compounding suitable working spaces on one piston the net forces on the piston rod can be reduced significantly. In double-acting alpha-engines this can be achieved by choosing the Siemens as opposed to the Franchot arrangement. As a result friction and piston seal leakage which are two important loss mechanisms are reduced significantly and longevity and mechanical efficiency is enhanced. Design implications are identified for various components, including pistons, seals, heat exchangers, regenerator, power extraction, and crankcase. The peculiarities of the heat source are also taken into account in these design recommendations.
A third key contribution is the extraction of novel insights from the modelling process. For the heat exchangers it has been shown that the hot and cold heat exchangers can be identical in their design without any negative impact on performance for the low-temperature difference situation. In comparison the high temperature applications invariably require different materials and designs for the two heat exchangers. Also, frequency and phase angle are found to be quite different (lower frequency and higher phase angle) from the optimum parameters found in high temperature engines. Contrary to common belief the role of dead volume has been found to play a crucial and not necessary detrimental role at low temperature differentials.
Taken together, the work is positioned at the intersection of thermodynamic analysis and engineering design, for the challenging area of Stirling engines at low temperature differences. The work extracts thermodynamic insights and extends these into design implications. Together these help create a robust theoretical and design foundation for further research and development in the important area of energy recovery.
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Mukherjee, Smarajit. "Time- and Space-resolved Heat Transfer Model for Spark-Ignition Engines." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1517440404339384.
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Wekin, Andrew Brian Evans. "Characterization and comparison of piezoelectric materials for transducing power from a thermoacoustic engine." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Summer2008/A_wekin_051908.pdf.
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Mzolo, Noluthando Precious Duduzile. "Modelling the performance of a calorifier installed at a university residence intended to be retrofited by an air source heat pump." Thesis, University of Fort Hare, 2017. http://hdl.handle.net/10353/4660.
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Sanitary hot water production contributes significantly to the electrical energy consumption in the university campus. An in-depth understanding of the current hot water technology, number of students, capacity of water used per student, time of use of hot water, total volume of hot water consumed and the total energy used on an average weekday in a university residence are very crucial in opting for energy efficient technology like an air source heat pump (ASHP) water heater. The study focused on quantitative and qualitative analysis of data collected for the hot water profiles in one of the university residences (Elitheini 1) from the conduction of experiment and questionnaires. The results revealed that 94% of the 75 students used hot water during the Eskom morning peak and 61% during the Eskom evening peak. In addition, the average daily energy consumption of the 12 kW Calorifier was 139.49 kWh, while the measured volume of hot water usage was 1950 L which is in strong agreement with the total volume (1945 L) of hot water consumption from the questionnaires. The p-value of the average volume of hot water usage measured by experiment and questionnaires was 0.7 and is of no mean significant difference. The monthly energy consumption for the week days was projected to be 2929.31 kWh. By retrofitting of calorifier with an ASHP unit, the energy consumption could reduce to 976.43 kWh based on its consecutive coefficient of performance of 3. Finally, from the energy consumption reduction analysis and the current Eskom tariffs, it can be alluded that the payback period of the proposedASHP unit as a retrofit to the calorifier is going to be less than 2 years and is worthy to invest into such technology under this study due to its favourable payback period and the reliability and lifespan of the ASHP unit.
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Jung, Sungmin. "Advancement of small-scale thermoacoustic engine." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/s_jung_042109.pdf.
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Thesis (M. in mechanical engineering )--Washington State University, May 2009.Title from PDF title page (viewed on Apr. 12, 2010). "School of Mechanical and Material Engineering." Includes bibliographical references (p. 48-49).
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Crowther, Shamal Mena. "The development of a fast response measurement system for use in turbomachinery applications." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51044/.
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Improvements in the efficiency of power generation via turbomachinery are essential in order to reduce greenhouse gas emissions throughout the world. Advancements in measurement techniques are therefore crucial to understanding the main areas of energy loss in turbines and compressors. This thesis presents a novel system which allows that loss to be characterised using fast response, 3-D measurements of the pressure field within industrial scale rigs. Turbulent energy dissipation rates give an insight into where useable energy is lost from. To gain an insight into such rates, measurement techniques must be able to take data in all three dimensions simultaneously at high sampling rates, usually over 50 kHz. Traditional methods of flow characterisation such as optical techniques and pneumatic pressure probes are unable to capture the rapid fluctuations in pressure and velocity which lead to energy loss from the turbomachine. A new system was therefore designed and implemented into a 6-stage compressor rig to take fast response measurements at sampling frequencies up to 100 kHz behind the last stage stator. A fast-response 5-sensor pressure head, acquired from Kulite Semiconductor Products Inc, has been embedded into a bespoke stem to allow turbulence measurements in a range of turbomachinery applications. The five-sensor (5S) probe was calibrated for pressure sensitivity as well as aerodynamically to give total and static pressure along with velocity magnitude and direction. Individual sensors were calibrated and characterised at temperatures within a range of 200C and 500C, which corresponds to the conditions found within the final application. The probe was also used in a vortex shedding experiment where alternative eddies were detected from the 5S probe measurements in both the time and frequency domain. The aerodynamic calibration of the 5S probe consists of exposing the probe sensors to a range of flow angles in order to map their response between ±200 in both the yaw and pitch directions. This results in four non-dimensional coefficients, two to represent pressure and two to signify the flow angles. A linear interpolation method was written and implemented to deduce pressure and flow angles from experimental query points and the calibration data. The linear interpolation was used as an alternative to the standard surface fit method, where the calibration data is expressed as system of polynomial equations. It was found that the linear method was applicable to the interpolation of flow angles and gave a reduction in computation time of the order of 104. The total and static pressure values do however require the more tried and tested polynomial interpolation method due to the need for higher order interaction terms in the surface fit equation describing the terms. The fully calibrated 5S probe was then implemented into a 6-stage industrial scale rig where it acquired fast response pressure data from the flow field at the exit of the last stage vane. The data was processed to give time resolved, 3-D measurements of total and static pressure, flow angle and velocity. Due to the simultaneous capture of data from all 5 sensors, the resulting velocity vectors can be decomposed into their mean and periodic components to obtain values of energy loss from the turbomachine. The acquisition of such data from an industrial rig marks a novel advancement in the area of turbomachinery flow characterisation and the use of the 5S probe in a range of applications will begin to fulfil the need for a database of fast response data from chaotic and turbulent flow fields.
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Crain, Kevin Richard. "Mechanical characterization and thermal modeling of a MEMS thermal switch." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/k%5Fcrain%5F120905.pdf.
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McNeil, Kirsten Elizabeth. "Energy loss characterization of the P3 MEMS heat engine." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Summer2006/k%5Fmcneil%5F062906.pdf.
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Finkbeiner, David L. "Calculation of gas-wall heat transfer from pressure and volume data for spaces with inflow and outflow." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12042009-020320/.
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Humphrey, Tammy Ellen Physics Faculty of Science UNSW. "Mesoscopic quantum ratchets and the thermodynamics of energy selective electron heat engines." Awarded by:University of New South Wales. Physics, 2003. http://handle.unsw.edu.au/1959.4/19186.
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A ratchet is an asymmetric, non-equilibrated system that can produce a directed current of particles without the need for macroscopic potential gradients. In rocked quantum electron ratchets, tunnelling and wave-reflection can induce reversals in the direction of the net current as a function of system parameters. An asymmetric quantum point contact in a GaAs/GaAlAs heterostructure has been studied experimentally as a realisation of a quantum electron ratchet. A Landauer model predicts reversals in the direction of the net current as a function of temperature, amplitude of the rocking voltage, and Fermi energy. Artifacts such as circuit-induced asymmetry, also known as self-gating, were carefully removed from the experimental data, which showed net current and net differential conductance reversals, as predicted by the model. The model also predicts the existence of a heat current where the net electron current changes sign, as equal numbers of high and low energy electrons are pumped in opposite directions. An idealised quantum electron ratchet is studied analytically as an energy selective electron heat engine and refrigerator. The hypothetical device considered consists of two electron reservoirs with different temperatures and Fermi energies. The reservoirs are linked via a resonant state in a quantum dot, which functions as an idealised energy filter for electrons. The efficiency of the device approaches the Carnot value when the energy transmitted by the filter is tuned to that where the Fermi distributions in the reservoirs are equal. The maximum power regime, where the filter transmits all electrons that contribute positively to the power, is also examined. Analytic expressions are obtained for the power and efficiency of the idealised device as both a heat engine and as a refrigerator in this regime of operation. The expressions depend on the ratio of the voltage to the difference in temperature of the reservoirs, and on the ratio of the reservoir temperatures. The energy selective electron heat engine is shown to be non-endoreversible, and to operate in an analogous manner to the three-level amplifier, a laser based quantum heat engine. Implications for improving the efficiency of thermionic refrigerators and power generators are discussed.
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Wang, Xiaowei. "Instantaneous in-cylinder heat transfer and combustion analysis in spark ignition engines." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497138.
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Bauer, Wolf-Dietrich. "Heat transfer and mixture vaporization in intake systems of spark ignition engines." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10421.
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Denzler, Tobias [Verfasser], and Eric [Akademischer Betreuer] Lutz. "Fluctuations and correlations of quantum heat engines / Tobias Denzler ; Betreuer: Eric Lutz." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1227304072/34.
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Panesar, Angad Singh. "Waste heat recovery using fluid bottoming cycles for heavy duty diesel engines." Thesis, University of Brighton, 2015. https://research.brighton.ac.uk/en/studentTheses/2e7faf1c-93fc-47b7-90f7-a6704ea95230.
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A typical long-haul heavy duty Diesel engine currently rejects up to 50% of the total fuel energy in the form of heat. Due to increasing CO2 emissions and fuel costs, there is a growing interest in techniques that can even partially utilise this wasted resource to improve the overall system efficiency. Fluid Bottoming Cycles (FBC) including Rankine and organic Rankine cycles offer one means towards converting waste heat into usable power. This thesis investigates the potential of FBCs to improve the net power of two computationally modelled (Ricardo WAVE V8.1) 10 litre engine platforms operating at Euro 6 emission levels.
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Alexander, W. D. "The design and evaluation of components for low heat loss diesel engines." Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236717.
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Chagnon-Lessard, Noémie. "Maximizing power output of heat engines through design optimization : Geothermal power plants and novel exhaust heat recovery systems." Doctoral thesis, Université Laval, 2020. http://hdl.handle.net/20.500.11794/38297.
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Le design de machines thermiques menant à une puissance maximale dépend souvent des températures de la source chaude et de la source froide. C’est pourquoi dégager des lignes directrices à partir des designs optimaux de ces machines selon diverses températures d’opération peut faciliter leur conception. Une telle étude est proposée par cette thèse pour deux types de systèmes thermiques. En premier lieu, le cycle de Rankine organique (ORC) est un cycle thermodynamique de puissance utilisé entre autres dans les centrales géothermiques exploitant des réservoirs à basse température. Depuis quelques années, ce type de centrales suscite un vif intérêt à travers le monde, étant un des modes de production de puissance parmi les plus respectueux de l’environnement. Il s’agit de pomper un géofluide du sol pour transférer sa chaleur à un fluide de travail qui opère en cycle fermé, et de le réinjecter ensuite dans le bassin géologique. Les chercheurs tentent actuellement de mieux caractériser le potentiel géothermique de divers environnements géologiques. Le sous-sol du Québec est relativement froid, alors des études essaient de déterminer s’il serait possible d’y exploiter de manière rentable des centrales géothermiques. Une autre question de recherche importante est de savoir, pour un contexte donné, quel est le design optimal d’une centrale géothermique et quelle est la puissance que l’on peut espérer produire. Pour répondre à cette question, les cycles de Rankine organiques de base (de type souscritique ou transcritique) sont dans un premier temps simulés et optimisés pour des températures du géofluide de 80 à 180°C et pour des températures de condensation du fluide de travail de 0.1 à 50°C. Trente-six (36) fluides pures sont investigués pour toutes les combinaisons de températures. Par la suite, des cycles de Rankine organiques plus avancés sont aussi investigués (ajout d’une tour de refroidissement, d’un système de récupération, et d’une contrainte sur la température de réinjection du géofluide). Les ORCs avec deux pressions de chauffage souscritique et transcritique sont aussi simulés et optimisés. Les optimisations sont faites pour 20 fluides de travail selon la même plage de température du géofluide et selon des températures du thermomètre mouillé de l’air ambient de 10 à 32°C. En second lieu, le cycle de Brayton inversé (IBC) est un cycle thermodynamique qui pourrait être utilisé comme système de récupération de la chaleur perdue dans les gaz d’échappement de moteurs. Il s’agit d’un cycle ouvert comprenant dans sa configuration de base une turbine à gaz, un échangeur de chaleur et un compresseur. Il existe une configuration où l’eau qui se condense lors du refroidissement des gaz est évacuée avant le compresseur pour réduire le débit massique et améliorer le rendement global du système. Le Powertrain and Vehicle Research Centre (PVRC) de l’University of Bath s’est intéressé à savoir si certaines variantes de l’IBC découlant de cette configuration seraient des options viables. Ces variantes ont mené à la création de trois nouveaux cycles thermodynamiques couplant l’IBC avec (i) une turbine à vapeur, (ii) un cycle de réfrigération, et (iii) ces deux ajouts. En comptant les deux cycles déjà existants décrits au paragraphe précédent, cinq configurations de l’IBC sont simulées et optimisées pour des températures de gaz d’échappement de 600 à 1200 K et températures de la source froide de 280 à 340 K. La finalité de cette thèse est d’offrir un outil aidant les ingénieurs à concevoir les systèmes introduits précédemment (ORC et IBC) de sorte qu’ils aient un travail spécifique net maximisé. Sous forme d’un ensemble de diagrammes, cet outil peut ainsi être utilisé pour une large plage de température de la source chaude (géofluide ou gaz d’échappement) et de température de la source froide.Heat engines design leading to maximum power output often depends on the hot source temperature and the cold source temperature. This is why drawing guidelines from optimal designs of these machines according to diverse operating temperatures may facilitate their conception. Such a study is proposed by this thesis for two types of heat engines. In the first instance, the Organic Rankine Cycle (ORC) is a power thermodynamic cycle used among others in geothermal power plants exploiting low-temperature reservoirs. This type of power plants raises keen interest around the world for being one the most environmentally friendly power production modes. In these power plants, a geofluid is pumped from the ground to transfer its heat to a working fluid operating in a closed cycle. The geofluid is then reinjected in the geological basin. Researchers are currently attempting to characterize in a better way the geothermal potential of diverse geological environments. Considering the province of Québec’s relatively cold underground, studies try to determinate whether it is possible to profitably operate geothermal power plants. Another important research question is to determine, for a given context, the optimal geothermal power plant design, and the amount of power that could be generated. To answer this question, Organic Rankine Cycles (subcritical and transcritical) are first simulated and optimized for geofluid temperatures from 80 to 180°C and for condensing temperatures of the working fluid from 0.1 to 50°C. Thirty-six (36) pure fluids are investigated for each temperature combination. Next, cycles models are improved by adding a cooling tower, a recuperative system and a constraint on the minimum reinjection temperature. ORCs with dual-pressure heater are simulated and optimized as well. Optimization runs are performed considering 20 working fluids for the same range of geofluid temperature and for ambient air wet bulb temperature from 10 to 32°C. In the second instance, the Inverted Brayton Cycle (IBC) is a thermodynamic cycle that could be used as a waste heat recovery system for engines exhaust gases. This is an open cycle which includes a gas turbine, a heat exchanger and a compressor as a basic layout. There is a configuration where the water condensed during the cooling of the gases is evacuated upstream of the compressor in order to reduce the mass flow rate and improve the system global efficiency. The Powertrain and Vehicle Research Centre (PVRC) of the University of Bath is interested in finding out whether particular IBC variants arising from this configuration could be viable options. These variants led to the creation of three novel thermodynamic cycles that couple the IBC with (i) a steam turbine, (ii) a refrigeration cycle, and (iii) both additions. Including both already existing cycles described in the preceding paragraph, five IBC layouts are simulated and optimized for exhaust gases temperatures from 600 to 1200 K and for heat sink temperatures from 280 to 340 K. The purpose of this thesis is to offer a tool that help engineers designing the systems previously introduced (ORC and IBC), so that they produced a maximized specific work output. As a set of charts, this tool can be used for a large range of hot source temperature (geofluid or exhaust gases) and of heat sink temperature.
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Huang, Shan. "Numerical and experimental study on pin-fin based cooling structure for gas turbine application." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32471/.
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This project aims to provide an in-depth understanding on pin-fin based cooling structure for gas turbine heat transfer applications, particularly for turbine hot-path airfoil blade trailing edge cooling. Based on past researches, new cooling structures are then proposed and investigated. This thesis is comprised by four primary studies including three experimental studies and one numerical study. Transient thermochromic liquid crystal method was used to measure endwall heat transfer coefficient of the channel while lumped capacitance method was used to measure the average heat transfer coefficient of cooling structure surface in corresponding studies. The Reynolds number was evaluated and pressure drop of flow across test channel was measured by the pressure taps. Parameters, such as Nusselt number, friction factor and thermal performance index, were evaluated based on experimental results. A scaled realistic NGV (Nozzle Guide Vane) hub platform model was tested. The local heat transfer distribution of its endwall was measured by liquid crystal method. The test has been carried out at Reynolds number range from 10,000 to 40,000. Two impinging nozzle plate with nozzle diameter of 5.5mm and 11.0mm were used. General findings include low heat transfer at acute angle corner and imbalance heat transfer distribution between upstream jet impingement region and downstream pin-fin region. The heat transfer rate at pin-fin region is only 44% of that at jet impingement region. Additionally, the existence of film hole (extraction hole) upstream of pin-fin region has insignificant influence on downstream pin-fin heat transfer in this test. It is also found that the heat transfer has been enhanced by 40% when the impinging nozzle diameter was doubled. Furthermore, the buoyancy effect at inlet flow has certain impact on magnitude and distribution of heat transfer at jet impinging target surface. The new elongated pedestal structure was proposed and investigated experimentally and numerically. Four elongated pedestal test sections with D/d=5.0 and 8.0, X/d=0.8 to 1.2, S/d=1.175 to 1.5 were designed and have been tested at Reynolds number range from 6,000 to 25,000. The average heat transfer coefficient at pedestal surface has been measured by lumped capacitance method. Revealed by the results, the heat transfer coefficient of pedestal surface could be at most 70% higher than that of endwall. Meanwhile, the pedestal surface could account for 50% of overall heat transfer at specific cases. The elongated pedestal structure enhanced the endwall heat transfer up to 9 times compare to reference data. Moreover, the elongated pedestal structure achieved similar heat transfer level comparing with perforated blockage structure but obtained 3 times higher heat transfer enhancement comparing to circular pin-fin structure. Generally, the tightly spaced structure obtained higher overall heat transfer than that of widely spaced structure which is same as circular pin-fin array. Via the numerical study, the flow behavior of elongated pedestal array is more like the turning flow inside the bending duct instead of flow around pin-fin structure. An extra structure, known as split elongated pedestal, has been studied numerically. However, the split elongated pedestal did not show significant improvement as expected in heat transfer enhancement as well as overall thermal performance. Currently split opening did not lead to significant flow interaction between two split parts. But it is recommended to further investigate this structure with much smaller split opening. Furthermore, three test sections with multiply cooling structure implemented were studied at Reynolds number range from 9,000 to 30,000. In addition, the test sections were modified in order to generate non-uniform inlet flow. One key finding is that the non-uniform inlet flow generated in this study leads to 25%-30% reduction in endwall heat transfer. Compare to circular pin-fin structure, cooling structure with high duct cross-section area block ratio, such as elongated pedestal and perforated blockage, provided more desired heat transfer distribution and higher heat transfer rate. Benefited from turbulence promotion by upstream pin-fin array, the heat transfer of downstream cooling configurations have been improved by 51%, 42% and 73% for pin-fin array, elongated pedestal array and perforated blockage array, respectively.
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Shafiei-Tehrany, Najmeddin. "Development of small-scale thermoacoustic engine and thermoacoustic cooling demonstrator." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Spring2008/N_Shafiei-Tehrany_042308.pdf.
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Jacob, David. "Analytical analysis of absorption cycles." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/16094.
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Lawrence, N. "The prediction of temperature distribution in air cooled diesel engine cylinder heads." Thesis, University of Brighton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233062.
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Goh, Sing Huat. "Numerical study of the effect of the fuel film on heat transfer in a rocket engine combustion chamber." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FGoh.pdf.
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Thesis (M.S. in Engineering Science (Mechanical Engineering))--Naval Postgraduate School, December 2003.Thesis advisor(s): Ashok Gopinath, Christopher Brophy. Includes bibliographical references (p. 71-72). Also available online.
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Gewald, Daniela [Verfasser]. "Waste heat recovery of stationary internal combustion engines for power generation / Daniela Gewald." München : Verlag Dr. Hut, 2013. http://d-nb.info/1045987735/34.
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Henson, Jonathan Charles. "Numerical simulation of spark ignition engines with special emphasis on radiative heat transfer." Thesis, Loughborough University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297589.
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Bagheri, Amirhossein. "Characterization, Analysis, and Optimization of Rotary Displacer Stirling Engines." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609074/.
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This work focuses on an innovative Rotary Displacer SE (RDSE) configuration for Stirling engines (SEs). RDSE features rotary displacers instead of reciprocating displacers (found in conventional SE configurations), as well as combined compression and expansion spaces. Guided by the research question "can RDSE as a novel configuration achieve a higher efficiency compared to conventional SE configurations at comparable operating conditions?", the goal of this study is to characterize, analyze, and optimize RDSE which is pursued in three technical stages. It is observed the RDSE prototype has an optimum phase angle of > 90° and thermal efficiency of 15.5% corresponding to 75.2% of the ideal (Carnot) efficiency at the source and sink temperatures of 98.6° C and 22.1° C, respectively. Initial results indicate that 125° phase angle provides more power than that of the theoretically optimum 90° phase angle. The results also show comparable B_n and significantly higher W_n values (0.047 and 0.465, respectively) compared to earlier studies, and suggest the RDSE could potentially be a competitive alternative to other SE configurations. Furthermore, due to lack of a regenerator, the non-ideal effects calculated in the analytical approach have insignificant impact (less than 0.03 kPa in 100 kPa). The clearance volume in the shuttled volume has a dramatic negative effect and reduces the performance up to 40%. Ultimately, utilizing CFD, it is proved that the existing geometry is relatively optimized where the optimum phase angle is 121° and geometric ratio D\/L for the displacer is 0.49.
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Klein, Markus. "Single-Zone Cylinder Pressure Modeling and Estimation for Heat Release Analysis of SI Engines." Doctoral thesis, Linköping : Department of Electrical Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-9863.
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Friedenberger, Alexander [Verfasser], Eric [Akademischer Betreuer] Lutz, and Eric [Gutachter] Lutz. "Detecting quantum signatures in heat engines / Alexander Friedenberger ; Gutachter: Eric Lutz ; Betreuer: Eric Lutz." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2019. http://d-nb.info/1180724135/34.
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Espinosa, Nicolas. "Contribution to the study of waste heat recovery systems on commercial truck diesel engines." Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL064N.
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L'augmentation du prix du pétrole ainsi qu'une possible future réglementation des émissions de CO2 encourage les fabricants de véhicules industriels à trouver de nouvelles solutions pour améliorer encore la performance de la chaine cinématique. Dans ce cadre, deux solutions de récupérations d'énergie prometteuses sont très souvent rapportées dans la littérature: le système de récupération d'énergie par cycle de Rankine et le générateur thermoélectrique. Après un rappel des conditions limites du fonctionnement d'un camion long routier, cette thèse démontre tout d’abord la modélisation 0-D et 1-D (logiciels commerciaux utilisés) de ces deux systèmes de récupération d’énergie. Pour le générateur thermoélectrique, des études paramétriques (hauteur de jambe thermoélectrique, prix, puissance électrique produite) sont effectuées se basant principalement sur l'utilisation de deux matériaux prometteurs. Une conception du système Rankine est présentée et modélisée avec le solveur 1-D. Des validations partielles sont réalisées sur les composants (turbine). Ce modèle a ensuite permis d'étudier les transitoires du système ainsi que la charge en réfrigérant et un système de contrôle possible. Cette étude montre que le générateur thermoélectrique n’est pas encore mature pour son utilisation dans un camion long routier. Le système Rankine doit quant à lui être testé sur un camion prototype pour pouvoir véritablement estimer son potentiel finalFuel price increase as well as future fuel consumption regulations lead truck manufacturers to further enhance the current powertrain. In such a context, two waste heat recovery technologies appear as promising: the Rankine system as well as the thermoelectric generator. After a reminding of truck boundary conditions, this thesis work defines 0-D and 1-D modeling (commercial tool used) for both systems.For the thermoelectric generator , parametric 1-D studies are done on the integration/design (number of thermoelements, price, electrical power) of a thermoelecric generator upstream the existing engine exhaust gas recirculation cooler. Main studies are done with thermoelectric materials but other materials are also considered. A Rankine system design is presented and modeled under a 1-D solver. Preliminary validations are presented. Transient aspects are evaluated to better understand the behavior of the system and its bottlenecks. The amount of refrigerant in the circuit and the control schematic are also addressed.From these studies, it appears that the thermoelectric generator technology is not yet mature for a long haul truck due to the low performance of thermoelectric materials. The Rankine system technology should handle a complete truck prototype testing to estimate its potential
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Potier, Luc. "Large Eddy Simulation of the combustion and heat transfer in sub-critical rocket engines." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0043/document.
Full textAbstract:
La combustion cryogénique dans les moteurs de fusée dits à propulsion liquide utilise généralement un couple d'ergols, le plus couramment composé d'hydrogène/oxygène (H2/O2). Privilégiée pour le fort pouvoir calorifique du dihydrogène, cette combustion à haute pression, induit des températures de fonctionnement très élevées et nécessite l'intégration d'un système de refroidissement. La prédiction des flux thermiques aux parois est donc un élément essentiel de la conception d'une chambre de combustion de moteur fusée. Ces flux sont le résultat d'écoulements fortement turbulents, compressibles, avec une cinétique chimique violente induisant de forts gradients d'espèces et de température. La simulation de ces phénomènes nécessite des approches spécifiques telles que la Simulation aux Grandes Echelles (SGE) qui réalise un très bon compromis entre précision et coût de calcul. Cette thèse a ainsi pour objectif la simulation par SGE des transferts de chaleur aux parois dans les chambres de combustion de moteurs fusée opérant en régime sous-critique. Le régime sous-critique implique un état liquide pour un des ergols, dont il faut traiter l'injection et l'atomisation. Dans un premier temps ce travail s'intéresse à plusieurs éléments de modélisation nécessaire pour réaliser les simulations visées. Le comportement des flammes H2/O2 est décrit par un schéma cinétique réduit et validé sur des configurations académiques. La prédictivité de ce schéma est évaluée sur une large gamme de fonctionnement dans des conditions représentatives des moteurs fusée. La simulation de l'injection de l'oxygène liquide (LOx) est un autre point critique qui nécessite de décrire l'atomisation et la phase dispersée ainsi que son couplage avec la phase gazeuse. La déstabilisation et l'atomisation primaire du jet liquide, trop complexe à simuler en SGE 3D, sont omises ici pour injecter directement un spray paramétré grâce à des corrélations empiriques. Enfin, la prédiction des flux thermiques utilise un modèle de loi de paroi spécifiquement dédiée aux écoulements à fort gradient de température. Cette loi de paroi est validée sur des configurations de canaux turbulents par comparaison avec des simulations avec résolution directe de la couche limite. La méthodologie basée sur les modèles développés est ensuite employée pour la simulation d'une chambre de combustion représentative du fonctionnement des moteurs cryogéniques. Il s'agit de la configuration CONFORTH testée sur le banc MASCOTTE (ONERA) et pour laquelle des mesures de température de paroi et de flux thermiques sont disponibles. Les résultats des SGE montrent un bon accord avec l'expérience et démontrent la capacité de la SGE à prédire les flux thermiques dans une chambre de combustion de moteur fusée. Enfin, dans un dernier chapitre ce travail s'intéresse à une méthode d'augmentation des transferts thermiques via une expérience de JAXA utilisant des parois rainurées dans la direction axiale. Par comparaison avec une chambre à parois lisses, les résultats démontrent la bonne prédiction par la SGE de l'augmentation du flux de chaleur grâce aux rainures et confirment la validité de la méthode développée pour des géométries de paroi complexesCombustion in cryogenic engines is a complex phenomenon, involving either liquid or supercritical fluids at high pressure, strong and fast oxidation chemistry, and high turbulence intensity. Due to extreme operating conditions, a particularly critical issue in rocket engine is wall heat transfer which requires efficient cooling of the combustor walls. The concern goes beyond material resistance: heat fluxes extracted through the chamber walls may be reused to reduce ergol mass or increase the power of the engine. In expander-type engine cycle, this is even more important since the heat extracted by the cooling system is used to drive the turbo-pumps that feed the chamber in fuel and oxidizer. The design of rocket combustors requires therefore an accurate prediction of wall heat flux. To understand and control the physics at play in such combustor, the Large Eddy Simulation (LES) approach is an efficient and reliable numerical tool. In this thesis work, the objective is to predict wall fluxes in a subcritical rocket engine configuration by means of LES. In such condition, ergols may be in their liquid state and it is necessary to model liquid jet atomization, dispersion and evaporation.The physics that have to be treated in such engine are: highly turbulent reactive flow, liquid jet atomization, fast and strong kinetic chemistry and finally important wall heat fluxes. This work first focuses on several modeling aspects that are needed to perform the target simulations. H2/O2 flames are driven by a very fast chemistry, modeled with a reduced mechanism validated on academic configurations for a large range of operating conditions in laminar pre- mixed and non-premixed flames. To form the spray issued from the atomization of liquid oxygen (LOx) an injection model is proposed based on empirical correlations. Finally, a wall law is employed to recover the wall fluxes without resolving directly the boundary layer. It has been specifically developed for important temperature gradients at the wall and validated on turbulent channel configurations by comparison with wall resolved LES. The above models are then applied first to the simulation of the CONFORTH sub-scale thrust chamber. This configuration studied on the MASCOTTE test facility (ONERA) has been measured in terms of wall temperature and heat flux. The LES shows a good agreement compared to experiment, which demonstrates the capability of LES to predict heat fluxes in rocket combustion chambers. Finally, the JAXA experiment conducted at JAXA/Kakuda space center to observe heat transfer enhancement brought by longitudinal ribs along the chamber inner walls is also simulated with the same methodology. Temperature and wall fluxes measured with smooth walls and ribbed walls are well recovered by LES. This confirms that the LES methodology proposed in this work is able to handle wall fluxes in complex geometries for rocket operating conditions