A 2-D Air Augmented Rocket, the Cal Poly Air Augmented Rocket (CPAAR) Test Apparatus operating as a mixer-ejector was tested to investigate high stagnation pressure ratio and transient flow fields of an ejector. The primary rocket ejector was supplied with high pressure nitrogen at a maximum chamber pressure of 1758 psia and a maximum mass flow rate of 1.4 lb/s. The secondary flow air was entrained from a fixed volume plenum chamber producing pressures as low as 3.3 psia. The maximum total pressure ratio achieved was 221. The original CPAAR apparatus was rebuilt re-instrumented and capability expanded. A fixed volume plenum was attached to the secondary ducts through a constant area square section to mimic the cross section of the secondary ducts with a bell mouth inlet. The mixing duct length was increased from 8 in. to 18 in. An investigation of the mixing duct flow-field was done with data from pressure and temperature instrumentation. A study of the transient operation of the rocket was compared with results from former research to qualify the quasi-steady assumption of the flow-field. The CPAAR produced Fabri-choked operation, the startup transient observed caused the secondary flow to become established during Fabri-choke mode operation. The supersonic saturated mode was not observed during quasi-steady operation. The quasi-steady operation was defined based on characteristics from previous quasi-steady models of transient operation of supersonic ejectors. The measurement of the data during testing resulted in a 2.96% experimental uncertainty in the entrainment ratio calculation. The smallest entrainment ratio observed was 0.05 at a total pressure ratio of 220. The location of the Fabri-choke point was shown through the interpretation of the primary and secondary flow as a result of the pressure and temperature measurements. The experimental evidence showed the location of the secondary choke point has a logarithmic relationship with the total pressure ratio. At a total pressure ratio of 220, the area of the aerodynamic throat of the secondary flow is 0.26 in2 and the location occurs 6 inches downstream from the nozzle exit. The secondary flow un-choke is related to the breakdown of the shock structure of the primary flow and produces a flow-field asymmetry which blocks the right duct flow. The CPSE simulation was unable to accurately predict AAR performance when the inputs are changed from the original CPAAR configuration. At high pressure ratios (PR=220), the error in the prediction is 90%.

The ejector expansion refrigeration cycle is a modified vapor compression cycle in which a two phase ejector is used to recover a portion of the work otherwise lost in the expansion valve. The ejector improves cycle performance by increasing compressor inlet pressure and by lowering the quality of the fluid entering the evaporator. Theoretically, a cooling COP improvement of approximately 21 % is achievable for a typical refrigerating cycle and an ideal ejector. If the ejector performed as well as typical single-phase ejectors, an improvement of 12% could be achieved. Previous tests have demonstrated a smaller 3.7% improvement; the difference is in the poor performance of the two-phase ejector. The purpose of this research is to understand the operating characteristics of the two phase ejector and to improve design. A two-phase ejector test rig has been constructed and tested. Preliminary data show performance superior to previously tested two-phase ejectors, but still inferior to single phase ejectors. Ejector performance corresponds to refrigeration cycle COP improvements ranging from 3.9010 to 7.6%. This performance was obtained with an ejector designed from single-phase ejector and wet steam ejector design methods. The poor performance indicates the design methods must be improved for two-phase ejectors. This research has begun the development of design methods for the two-phase ejectors and this research has developed models to describe the fluid dynamics and thermodynamics of the ejector. / Ph. D.

Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2018-04-25T13:35:45Z No. of bitstreams: 1 Henrique Schardosin Ferreira_.pdf: 4214270 bytes, checksum: b40eaaf06dd9b49a976b944788dce2f1 (MD5) / Made available in DSpace on 2018-04-25T13:35:45Z (GMT). No. of bitstreams: 1 Henrique Schardosin Ferreira_.pdf: 4214270 bytes, checksum: b40eaaf06dd9b49a976b944788dce2f1 (MD5) Previous issue date: 2017-09-29 / Nenhuma / Nessa dissertação foi apresentado um estudo do uso do ejetor bifásico em um sistema de refrigeração para condicionamento de ar automotivo, para recuperação das perdas de energia durante o processo de expansão. Um modelo numérico foi utilizado para a predição do ganho energético com a aplicação do ejetor com base no ciclo padrão de ejetor proposto por Gay (1931). Posteriormente, foi proposto um modelo numérico para a determinação das dimensões básicas necessárias para a fabricação do ejetor. Uma bancada de simulação construída para o ciclo de refrigeração padrão para condicionamento de ar automotivo foi modificada para a instalação do ejetor e passou a operar de acordo com o ciclo COS de Oshitani et al. (2005). Dos diversos modelos matemáticos existentes na literatura, foi escolhido um modelo de simulação de ciclo de ejetor para operação em regime subcrítico da análise unidimensional proposta por Kornhauser (1990) e para a solução do modelo foram desenvolvidos programas computacionais no software EES - Engineering Equation Solver, no qual as rotinas de cálculos foram construídas para solução numérica iterativa visando à determinação do ponto ótimo de operação do ciclo. Para comprovação do modelo e dos resultados obtidos pelos programas, foi repetida a análise apresentada por Kornhauser (1990) e os resultados comparados com os seus. Os resultados gerados pelos programas mostraram boa aderência aos publicados por autores que estudaram aplicação semelhante, sendo assim considerados confiáveis na aplicação para predição de desempenho de ciclos com ejetor em operação com fluidos em regime subcrítico. A bancada de testes instalada no Laboratório de Estudos Térmicos e Fluido Dinâmicos da Unisinos (LETEF), construída por Souza (2011) e posteriormente utilizada por Noetzold (2016) na simulação do ciclo padrão de refrigeração de um sistema de condicionamento de ar automotivo foi alterada para instalação do ejetor em operação sob configuração do ciclo COS. A adoção do ciclo COS se deu em função da incerteza do retorno de óleo e do controle da separação das fases do refrigerante no acumulador de sucção do ciclo padrão. O sistema foi submetido as condições de operação previstas na norma SAE J2765 OCT2008 (2008) e operou com R-134a. Os resultados foram comparados com os do ciclo padrão de Noetzold (2016) apresentando aumento médio do COP do ciclo de 25% para a faixa de baixa rotação e de 46% para a faixa de alta rotação e comparados também aos resultados de Lawrence (2012). / In this work was presented a study of the use of the ejector in a cooling system for automotive air conditioning, to recover energy losses during the expansion process. A numerical model was used to predict the energetic gain with ejector application based on the ejector standard cycle proposed by Gay (1931). Subsequently, a numerical model was proposed to determine the basic dimensions necessary for the ejector manufacturing. A simulation system for the standard refrigeration cycle for automotive air conditioning was modified for the ejector installation and started to operate according to the COS cycle by Oshitani et al. (2005). From the several mathematical models in the literature, a model of the ejector cycle simulation for subcritical fluids of the one-dimensional analysis proposed by Kornhauser (1990) was chosen, and for the solution of the model computational programs were developed in the EES - Engineering Equation Solver software in which the calculation routines were constructed for iterative numerical solution in order to determine the optimum operating point of the cycle. To prove the model and the results obtained by the programs, the analysis presented by Kornhauser (1990) and the results compared were repeated. The results generated by the programs showed good results, being thus considered reliable in the application to predict performance of ejector cycles in operation with sub-critical fluids. The simulation system installed in the Laboratory of Thermal and Dynamic Fluid Studies of Unisinos (LETEF), built by Souza (2011) and later used by Noetzold (2016) in the simulation of the standard refrigeration cycle of an automotive air conditioning system, was changed for installation of the ejector in operation under COS cycle configuration. The choice of the COS cycle was due to the uncertainty of the oil return to compressor and the control of the separation of the phases of the refrigerant in the suction accumulator of the standard cycle. The system was subjected to the operating conditions set forth in the standard SAE J2765 OCT2008 (2008) and operated with R-134a. The results were compared with those of standard cycle by Noetzold (2016), showing a mean increase of the cycle COP of 25% for the low rotation range and 46% for the high rotation range and also compared to Lawrence (2012).

Rocket-Based Combined Cycle (RBCC) engines combine the best performance characteristics of air-breathing systems such as ramjets and scramjets with rockets with the goal of increasing payload/structure and propellant performance and thus making LEO more readily accessible. The idea of using RBCC engines for Single-Stage-To-Orbit (SSTO) trans-atmospheric acceleration is not new, but has been known for decades. Unfortunately, the availability of detailed models of RBCC engines is scarce. This thesis addresses the issue through the construction of an analytical performance model of an ejector rocket in a dual combustion propulsion system (ERIDANUS) RBCC engine. This performance model along with an atmospheric model, created using MATLAB was designed to be a preliminary `proof-of-concept' which provides details on the performance and behavior of an RBCC engine in the context of use during trans-atmospheric acceleration, and also to investigate the possibility of improving propellant performance above that of conventional rocket powered systems. ERIDANUS behaves as a thrust augmented rocket in low speed flight, as a ramjet in supersonic flight, a scramjet in hypersonic flight, and as a pure rocket near orbital speeds and altitudes. A simulation of the ERIDANUS RBCC engine's flight through the atmosphere in the presence of changing atmospheric conditions was performed. The performance code solves one-dimensional compressible flow equations while using the stream thrust control volume method at each station component (e.g. diffuser, burner, and nozzle) in all modes of operation to analyze the performance of the ERIDANUS RBCC engine. Plots of the performance metrics of interest including specific impulse, specific thrust, thrust specific fuel consumption, and overall efficiency were produced. These plots are used as a gage to measure the behavior of the ERIDANUS propulsion system as it accelerates towards LEO. A mission averaged specific impulse of 1080 seconds was calculated from the ERIDANUS code, reducing the required propellant mass to 65% of the gross lift off weight (GLOW), thus increasing the mass available for the payload and structure to 35% of the GLOW. Validation of the ERIDANUS RBCC concept was performed by comparing it with other known RBCC propulsion models. Good correlation exists between the ERIDANUS model and the other models. This indicates that the ERIDANUS RBCC is a viable candidate propulsion system for a one-stage trans-atmospheric accelerator.

Water and energy crises have forced researchers to seek alternative water and energy sources. Seawater desalination can contribute towards meeting the increasing demand for fresh water using alternative energy sources like low-grade heat. Industrial waste heat, geothermal, solar thermal, could help to ease the energy crisis. Unfortunately, the efficiency of the conventional power cycle becomes uneconomically low with low-grade heat sources, while, at the same time, seawater desalination requires more energy than a conventional water treatment process. However, heat discarded from low-grade heat power cycles could be used as part of desalination energy sources with seawater being used as coolant for the power cycles. Therefore a study of desalination using low-grade heat is of great significance. This research has comprehensively reviewed the current literature and proposes two systems that use low-grade heat for desalination applications or even desalination/power cogeneration. The proposed two cogeneration systems are a supercritical Rankine cycle-type coupled with a reverse osmosis (RO) membrane desalination process, and a power cycle with an ejector coupled with a multi-effect distillation desalination system. The first configuration provides the advantages of making full use of heat sources and is suitable for hybrid systems. The second system has several advantages, such as handling highly concentrated brine without external electricity input as well as the potential of water/power cogeneration when it is not used to treat concentrated brine. Compared to different stand-alone power cycles, the proposed systems could use seawater as coolant to reject low-grade heat from the power cycle to reduce thermal pollution.

Dans le contexte des recherches de réductions de l’impact environnemental des machines frigorifiques, l’utilisation du gaz carbonique comme fluide frigorigène est aujourd’hui une réalité. Toutefois, les propriétés thermodynamiques du CO2 impliquent un cycle frigorifique transcritique à basses performances énergétiques pour une température de source chaude proche de l’ambiante. Pour étendre le champ d’application de ce fluide, il est nécessaire d’augmenter l’efficacité des machines transcritiques. L’analyse exergétique du cycle montre que les principales pertes de performances proviennent essentiellement de la détente isenthalpique et de la compression. Afin de réduire ces pertes, l’utilisation d’un éjecteur comme organe principale de détente se présente comme une solution prometteuse. Ce travail apporte une contribution à l’étude des machines frigorifiques aux CO2 transcritique équipées d’éjecteur à la fois expérimentale et numérique pour développer la compréhension des phénomènes qui se produisent à l’intérieure de l’éjecteur afin d’améliorer les outils de dimensionnement de cet organe. L’étude numérique comporte un modèle unidimensionnel de l’écoulement du dioxyde de carbone à travers l’éjecteur. Ce modèle constitue un bon outil de prédiction des points de fonctionnement de l’éjecteur et des caractéristiques globales de l’écoulement : débit, vitesse, enthalpie... Le modèle reste une approche perfectible d'un milieu complexe. Il constitue néanmoins un bon outil pour l'optimisation de la géométrie de l’éjecteur. Après le dimensionnement et la fabrication de l’éjecteur, des essais comparatifs ont été menés sur la machine frigorifique au CO2 en fonctionnement avec et sans éjecteur. L’étude expérimentale a montré que l’éjecteur améliore jusqu’à 12,5 % la puissance frigorifique produite et 17 % le coefficient de performance de la machine. Les résultats expérimentaux réalisés ont été utilisés pour valider le modèle unidimensionnel développé, un accord satisfaisant a été trouvé entre les résultats issus du modèle et ceux expérimentaux, particulièrement en terme de débits avec un écart de l’ordre de 9 %. / Carbon dioxide is being advocated to reduce the environmental impact of the refrigeration systems. However, the thermodynamic properties of CO2 imply supercritical refrigerating cycle with low energy performance when the hot source temperature is near that of the environment. The expansion losses of an isenthalpic throttling process have been identified as one of the largest irreversibilities of transcritical refrigeration cycles, which contribute to the low efficiency of such cycles. In order to recover the expansion losses and increase the cycle efficiency, it has been proposed to replace the expansion valve with an ejector expansion device. This work is devoted to the numerical and experimental study of the ejector expansion devices used in a transcritical vapor compression system using carbon dioxide as the refrigerant. The numerical study includes a one-dimensional model of the CO2 two-phase ejector. The developed model is a good tool for predicting the operation conditions of the ejector and the overall characteristics of the flow (mass flow, velocity, enthalpy.. The model is a good tool to optimizing the geometry of the ejector, although it can be improved. The ejector was manufactured and incorporated into an instrumented test bench. Experimental study showed that the transcritical CO2 refrigeration system using an ejector as the expansion device outperformed a conventional expansion-valve transcritical CO2 system in COP and cooling capacity by approximately 17 % and 12,5 %, respectively. The experimental results were used to validate the one-dimensional model, a satisfactory agreement was found between the numerical and experimental results, especially in terms of mass flow with a difference of 9 %.

Le travail mené dans le cadre de cette thèse porte sur l’étude expérimentale et numérique de l’écoulement au sein d’un éjecteur supersonique. Le régime d’écoulement qui s’installe dans ces appareils est très complexe du fait des phénomènes physiques qui les caractérisent comme la turbulence et les ondes de choc. Les méthodes expérimentales utilisées sont la mesure de la pression le long de l’axe de l’éjecteur `a l’aide d’une sonde développée à cet effet, la visualisation de l’écoulement par tomographie laser et la mesure de vitesse par PIV. Les simulations numériques sont réalisées à l’aide du code Ansys-Fluent en 2D axisymétrique et en 3D. Dans un premier temps, une étude de sensibilité du modèle numérique portant sur les paramètres de simulations et les modèles de turbulence est menée sur l’éjecteur fonctionnant sans flux induit. La validation des simulations repose sur une comparaison des résultats numériques avec des mesures de vitesse par PIV. Un modèle 3D s’est avéré incontournable pour l’étude de l’écoulement dans l’éjecteur avec flux induit à cause de sa géométrie complexe. Les outils expérimentaux et numériques développés permettent d’analyser finement l’interaction des flux moteur et induit, en particulier les processus de recompression par chocs obliques et de mélange. Une tentative de modélisation par LES des instabilités de l’écoulement détectées expérimentalement est également abordée. / The work reported in this thesis relates to the experimental and numerical studies of the flow within a supersonic ejector. The flow pattern which occurs in these apparatuses is very complex because of the flow phenomena encountered like flow turbulence and shock waves. The experimental methods used are the measurement of the pressure along the axis of the ejector using a specific probe developed for this purpose, the flow visualization by laser tomography and the velocity measurement by PIV. The numerical simulations are carried out using the Ansys-Fluent code with 2D axisymmetric and 3D models. First, a study of sensitivity to the numerical parameters of simulation and to the turbulence models is carried out on the ejector operating without induced flow. The validation of the simulations is achieved by a comparison between the numerical results and velocity measurements by PIV. A 3D model is necessary for the simulation of the flow in the ejector operating with induced flow because of the complex ejector geometry. The experimental techniques and the numericalmodels developed make it possible to analyze the interaction of the primary and secondary flows, in particular the process of recompression by oblique shocks and the mixing process. An attempt at modeling by LES simulation the flow instabilities detected during experiments is also approached.

The main Target of this diploma is to find some reconciliation with cooperation of turbine and ejector. This work is containing informations about this mechanisms and also its historical development. The merits of this diploma thesis is thermodynamics calculation and proposal of main parameters and proportions of the turbine and the ejector. After this it is follow by the calculation of whole system of the turbine and ejector in consequence with calculation of turbine with by-pass regulation and also comparison of power output with ejector and with by-pass technology.

This diploma thesis deals with reducing the time of sucking water into the rotating impeller of the centrifugal pump as used in firesport. The suction is carried out by the ejector, which is powered by combustion engine exhaust gases. A mathematical model was created, which shows the flow in the ejector. It was also used as a basis for the creation of a new ejector, which has an increased airflow when getting closer to atmospheric pressure.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006. / A small scale steam jet ejector experimental setup was designed and manufactured. This ejector setup is of an open loop configuration and the boiler can operate in the temperature range of Tb = 85 °C to 140 °C. The typical evaporator liquid temperatures range from Te = 5 °C t o 10 °C while the typical water cooled condenser presure ranges from Pc = 1 . 70 kPa t o 5. 63 kPa (Tc = 15 °C to 35 °C). The boiler is powered by by two 4kW electric elements, while a 3kW electric element simulates the cooling load in the evaporator. The electric elements are controlled by means of variacs. The function ... / Centre for Renewable and Sustainable Energy Studies