Dissertations / Theses on the topic 'Jet ejector'

The ability to produce potable water economically is the primary focus of seawater desalination research. There are numerous methods to desalinate water, including reverse osmosis, multi-stage flash distillation, and multi-effect evaporation. These methods cost more than potable water produced from natural resources; hence an attempt is made in this research project to produce potable water using a modified high-efficiency jet ejector in vapor-compression distillation. The greater efficiency of the jet ejector is achieved by properly mixing propelled and motive streams. From experiments conducted using air, the pressure rise across the jet ejector is better in case of one or two mixing vanes and the highest back pressure (pinch valve closed 83.33%). At other pinch valve closings, the air velocity through the jet ejector was high, so the extra surface area from the mixing vanes caused excessive friction and lowered the efficiency.

A CFD model to simulate two-phase flow in refrigerant ejectors is described. This work is part of an effort to develop the ejector expansion refrigeration cycle, a device which increases performance of a standard vapor compression cycle by replacing the throttling valve with a work-producing ejector. Experimental results have confirmed the performance benefit of the ejector cycle, but significant improvement can be obtained by optimally designing the ejector. The poorly understood two-phase, non-equilibrium flow occuring in the ejector complicates this task. The CFD code is based on a parabolic two-fluid model. The applicable two-phase flow conservation equations are presented. Also described are the interfacial interaction terms, important in modelling non-equilibrium effects. Other features of the code, such as a mixing length turbulence model and wall function approximation, are discussed. Discretization of the equations by the control volume method and organization of the computer program is described. Code results are shown and compared to experimental data. It is shown that experimental pressure rise through the mixing section matches well against code results. Variable parameters in the code, such as droplet diameter and turbulence constants, are shown to have a large influence on the results. Results are shown in which an unexpected problem, separation in the mixing section, occurs. Also described is the distribution of liquid across the mixing section, which matches qualitative experimental observations. From these results, conclusions regarding ejector design and two-phase CFD modelling are drawn.
Ph. D.

Research was performed to optimize high-efficiency jet ejector geometry (Holtzapple, 2001) by varying nozzle diameter ratios from 0.03 to 0.21, and motive velocities from Mach 0.39 to 1.97. The high-efficiency jet ejector was simulated by Fluent Computational Fluid Dynamics (CFD) software. A conventional finite-volume scheme was utilized to solve two-dimensional transport equations with the standard k-?? turbulence model (Kim et. al., 1999). In this study of a constant-area jet ejector, all parameters were expressed in dimensionless terms. The objective of this study was to investigate the optimum length, throat diameter, nozzle position, and inlet curvature of the convergence section. Also, the optimum compression ratio and efficiency were determined. By comparing simulation results to an experiment, CFD modeling has shown high-quality results. The overall deviation was 8.19%, thus confirming the model accuracy. Dimensionless analysis was performed to make the research results applicable to any fluid, operating pressure, and geometric scale. A multi-stage jet ejector system with a total 1.2 compression ratio was analyzed to present how the research results may be used to solve an actual design problem. The results from the optimization study indicate that the jet ejector efficiency improves significantly compared to a conventional jet-ejector design. In cases with a subsonic motive velocity, the efficiency of the jet ejector is greater than 90%. A high compression ratio can be achieved with a large nozzle diameter ratio. Dimensionless group analysis reveals that the research results are valid for any fluid, operating pressure, and geometric scale for a given motive-stream Mach number and Reynolds ratio between the motive and propelled streams. For a given Reynolds ratio and motivestream Mach number, the dimensionless outlet pressure and throat pressure are expressed as Cp and Cpm, respectively. A multi-stage jet ejector system with a total 1.2 compression ratio was analyzed based on the optimization results. The result indicates that the system requires a lot of high-pressure motive steam, which is uneconomic. A high-efficiency jet ejector with mixing vanes is proposed to reduce the motive-steam consumption and is recommended for further study.

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

Os ejetores são dispositivos largamente utilizados nos mais diversos ramos da engenharia. Este trabalho foi desenvolvido no Laboratório de Hidráulica da Escola de Engenharia de São Carlos - USP, com o propósito de avaliar experimental e teoricamente o desempenho de ejetores de baixo custo, projetados e construídos em conexões do tipo \"tê\" de PVC, onde água foi utilizada tanto como fluido prmário como secundário. Os ensaios foram realizados com ejetores de diâmetros nominais de 25 mm e de 32 mm com relações de áreas de 0,25; 0,35 e 0,53. Foi utilizado também, para cada diâmetro, um ejetor mais compacto e sem câmara de mistura, com a relação de áreas de valor intermediário. Os ejetores comuns apresentaram rendimentos mais elevados do que os compactos, sendo o máximo de 30,52% alcançado com o ejetor de 25 mm e relação de áreas de 0,35. Os coeficientes de perda de carga em cada componente dos ejetores foram ajustados através de um modelo unidimensional. O fenômeno da cavitação também foi analisado. Os resultados mostraram que os ejetores de baixo custo apresentam funcionamento similar ao dos ejetores convencionais.
The ejectors are devices widely used in the most several branches of the engineering. This work was developed at the Laboratory of Hydraulics of the School of Engineering of São Carlos - SP, with the purpose of evaluating experimentally and theoretically the acting of low cost ejectors, projected and built in connections of the type \"tee\" of PVC, where water was used as much primary fluid as secondary. The experiments were accomplished with ejectors of nominal diameters of 25 mm and of 32 mm with area ratio of 0,25; 0,35 and 0,53. It was also used, for each diameter, a more compact ejector and without mixing chamber, with the area ratio of intermediate value. The common ejectors presented higher efficiencies than the compact ones, being the maximum of 30,52% reached with the ejector of 25 mm and area ratio of 0,35. The coefficients of head loss in each component of the ejectors were adjusted through one-dimensional model. The phenomenon of the cavitation was also analyzed. The results showed that the low cost ejectors present similar operation to the conventional ejectors.

This diploma thesis deals with the area of ejectors. In the intoduction, an ejector is classed as an hydraulic machine. There is also an introduction of the principle and application of this machine there. The next part describes two different ways of calculation and there is a suggestion how to get characteristics, that were achieved by calculation in MS Excel, projected. The purpose of this diploma thesis is to confront this mathematical model with the experiment done in school laboratory at Kaplan department of hydraulic machines. The description of this experiment and the evaluation procedure of measured values is described in the final part of this diploma thesis.

This thesis presents the results of steady, Reynolds-averaged Navier-Stokes (RANS) computations for jet flow emanating from a generic turbofan engine exhaust. All computations were performed with commercial solver FLUENT v6.2.16. Different turbulence models were evaluated. In addition to turbulence modeling issues, a parametric study was considered. Different modeling approaches for turbulent jet flows were explained in brief, with specific attention given to the Reynolds-averaged Navier-Stokes (RANS) method used for the calculations. First, a 2D ejector problem was solved to find out the most appropriate turbulence model and solver settings for the jet flow problem under consideration. Results of one equation Spalart-Allmaras, two-equation standart k-&
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, realizable k-&
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and SST k-&
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turbulence models were compared with the experimental data provided and also with the results of Yoder [21]. The results of SST k-&
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and Spalart-Allmaras turbulence models show the best agreement with the experimental data. Discrepancy with the experimental data was observed at the initial growth region of the jet, but further downstream calculated results were closer to the measurements. Comparing the flow fields for these different turbulence models, it is seen that close to the onset of mixing section, turbulence dissipation was high for models other than SST k-&
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and Spalart-Allmaras turbulence models. Higher levels of turbulent kinetic energy were present in the SST k-&
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and Spalart-Allmaras turbulence models which yield better results compared to other turbulence models. The results of 2D ejector problem showed that turbulence model plays an important role to define the real physics of the problem. In the second study, analyses for a generic, subsonic, axisymmetric turbofan engine exhaust were performed. A grid sensitivity study with three different grid levels was done to determine grid dimensions of which solution does not change for the parametric study. Another turbulence model sensitivity study was performed for turbofan engine exhaust analysis to have a better understanding. In order to evaluate the results of different turbulence models, both turbulent and mean flow variables were compared. Even though turbulence models produced much different results for turbulent quantities, their effects on the mean flow field were not that much significant. For the parametric study, SST k-&
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turbulence model was used. It is seen that boundary layer thickness effect becomes important in the jet flow close to the lips of the nozzles. At far downstream regions, it does not affect the flow field. For different turbulent intensities, no significant change occurred in both mean and turbulent flow fields.

The flow field around a low pressure turbine (LPT) blade cascade model with and without flow control is examined using ejector nozzle (EN) and vortex generator jet (VGJ) geometries for separation control. The cascade model consists of 6 Pak-B Pratt andamp; Whitney low pressure turbine blades with Re = 30,000-50,000 at a free-stream turbulence intensity of 0.6%. The EN geometry consists of combined suction and blowing slots near the point of separation. The VGJs consist of a row of holes placed at an angle to the free-stream, and are tested at two locations of 69% and 10.5% of the suction surface length (SSL). Results are compared between flow control on and flow control off states, as well as between the EN, VGJs, and a baseline cascade with no flow control geometry for steady and pulsatile blowing. The EN geometry is shown to control separation with both steady and pulsatile blowing. The VGJs at 69% SSL are shown to be much more aggressive than the EN geometry, achieving the same level of separation control with lower energy input. Pulsed VGJs (PVGJ) have been shown to be just as effective as steady VGJs, and results show that a 10% duty cycle is almost as effective as a 50% duty cycle. The VGJs at 10.5% SSL are shown to be inefficient at controlling separation. No combination of duty cycle and pulsing frequency tested can eliminate the separation region, with only higher steady blowing rates achieving separation control. Thus, the VGJs at 69% SSL are shown to be the most effective in controlling separation.

En framtida alternativ framdrivningsmetod av fartyg skulle kunna vara en ångjetstråle som expanderas via en ejektor. Syftet med studien var att utföra ett experiment med två olika typer av utloppsmunstycken på ejektorns diffusor, för att därigenom ta reda på vilken design som lämpar sig för denna framdrivningsmetod samt vilken tryckkraft som är möjlig att uppnå. Studiens resultat är tänkt att användas som underlag för fortsatta studier om fartygsframdrift med ångjetstråle via en ejektor, för att eventuellt kunna öka energieffektiviteten i jämförelse med dagens framdrivningsmetoder. Resultatet visar att en cirkulär strålbild ger högst tryckkraft trots ett lägre inloppstryck vid en vattentemperatur på 70 °C i jämförelse med en platt strålbild vid ett högre inloppstryck och samma temperatur. Experimentet gav ingen mätbar tryckkraft vid expansion av fuktig ånga med ett tryck på 3 MPa och en temperatur på 150 °C.
A future alternative propulsion method of ships could be a steam jet that is expanded via an ejector. The purpose of the study was to conduct an experiment on two different types of outlet nozzles on the diffuser of the ejector. This was carried out to find which design that is suitable for this propulsion method and what propulsion force that was possible to achieve. The result of the study was then thought to be used as a basis for further studies of steam jet propulsion through an ejector, to possibly increase the energy efficiency in comparison with today's propulsion methods. The result shows that a circular jet provides maximum propulsion force despite a lower inlet pressure and a water temperature at 70 °C in comparison with a flat jet at higher inlet pressures and equal temperature. The experiment gave no measurable propulsion force when expanding wet steam at a pressure of 3 MPa and a temperature at 150 °C.

A jet ejector may be used as a compressor or to enhance thrust of watercraft or aircraft. Optimization of jet ejectors as compressors and thrust augmenters was conducted using the software GAMBIT (Computer Aided Engineering (CAE) tool for geometry and mesh generation) and FLUENT (Computational Fluid Dynamics (CFD) solver kit). Scripting languages PYTHON and SCHEME were used to automate this process. The CFD model employed 2D axis symmetric, steady-state flow using the ε−k method (including wall functions) to model turbulence. Initially, non-dimensionalization of the jet ejector as a gas compressor was performed with respect to scale, fluid, and operating pressure. Surprisingly, rather than the conventional parameters like Mach or Re number, the results showed a completely new parameter (christenedGM- Gauge Mach) that when kept constant will result in non-dimensionalization. Non-dimensionalization of a jet ejector for watercraft propulsion was conducted using 2D axis symmetric, steady-state flow modeling using the ε−kmethod (including wall functions). It showed consistent results for the same velocity ratio (r) of nozzle velocity to free-stream velocity for different scales, fluids, and ambient pressures.

Includes bibliographical references.
Industry often requires the sorting of one material from another. Although the detection of desired (or undesired) elements is well advanced, the mechanical ejection or removal of particles is fairly underdeveloped. Agriculture and mining applications have used air jets and water jets to eject particles ranging in weight from a few grams to several hundred. With the current trends in mechanization leading towards higher processing speeds, these traditional methods have been found to be unsuitable: they have slow turn-on and turn-off response times, leading to a high volume of material being ejected with the target. Higher processing speeds will lead to even greater amounts of waste material being ejected thus producing even lower yield concentrations. Thus the need for a quick response time, repetitive, impulse ejection mechanism in the sorting industry is apparent. A kinematic analysis of the required ejection mechanism blast strength shows that the required force depends on the target mass, the required deflection angle the force application angle and the force duration. Acoustical techniques in air are unsuitable as ejection force mechanisms. A water jet is proposed to meets these requirements. This water jet is caused by an electrical discharge in a liquid cavity. This produces a weak shock wave which is focused by the cavity to a nozzle where a slug of water is emitted. The cavity is an elliptical cavity of height h, with the electrodes mounted end on at the first focus and a reflecting cone and nozzle at the second focus. The propagation of weak shock waves in the elliptical cavity is studied theoretically and numerically - using a finite difference simulation program. The reflected converging wave is shown to depend on the cavity eccentricity and the wall admittance. The resulting converging shock wave has an asymmetrical pressure distribution. This analysis is used in the design of a prototype water jet generator. The electrical discharge circuit used for the production of shock waves in the cavity is analysed and the physical discharge process of electrical to shock energy conversion reviewed. Conditions for the maximisation of this transfer correspond to large water gap resistances, high voltages and low circuit inductances. Experiments on the prototype generator show that the transient water jet slug energy is relatively low. High speed photographic techniques reveal that the jet velocity is of the order of 30 m/s. Published results show much higher jets speeds are possible. The operation of the electrical discharge circuit is found to critically influence the water jet performance - electrical measurements show that the circuit is a sub-optimum, underdamped RLC circuit. The cone / nozzle operation is also shown to have a marked effect on performance. The nozzle in particular requires optimisation. The prototype in its present form is not suitable for use in an ejection system. Although the pulse length, rise time and channel spread of the device are suitable, the blast strength is not sufficient for deflection of the heaviest range of particles. Optimisation of the electrical circuit and increased energies will increase the blast strength.

Les jets relativistes, bien qu'omniprésents dans l'Univers, n'ont pas fini de livrer tous leurs secrets. Au contraire, certaines des questions les plus fondamentales du domaine restent sans réponses. C'est le cas notamment du mécanisme à l'origine de leur éjection dont la compréhension lèverait le voile sur la nature de ce lien si profond qu'ils entretiennent avec l'accrétion de matière. Je décris dans ce manuscrit une étude visant à reproduire le spectre multi-longueurs d'onde du microquasar MAXI J1836-194, du domaine radio aux rayons X, à l'aide d'un modèle numérique basé sur le principe des chocs internes. Ce modèle, baptisé ishem, est un pionnier du genre puisqu'il se base sur l'hypothèse inédite selon laquelle les fluctuations de vitesse du jet sont directement gouvernées par la variabilité du disque d'accrétion. Je propose un scénario qui reproduit fidèlement l'éruption de la source en 2011 et explore des voies d'améliorations en vue de perfectionner le modèle
Relativistic jets, although ubiquitous in the Universe, have not yet delivered all their secrets. On the contrary, some of the most fundamental questions of the field remain unanswered. The ejection mechanism at the origin of the emission is still unknown, characterising it precisely would lift the veil on the nature of the intimate link between ejection and accretion of matter. I describe in this manuscript a study aiming to reproduce five radio-X spectra of a microquasar, MAXI J1836-194, using an internal shocks model. This model, named ishem, is a pioneer in the domain since it is based on the groundbreaking hypothesis that the jet velocity fluctuations are directly driven by the accretion flow variability. I propose here a scenario recreating the 2011 outburst of the source and propose some reflections with the aim of upgrading the model

Une étude de 2 diagnostics de perte de masse dans les objets stellaires est faite et un programme qui calcule la formation des raies rotationnelles de CO en géometrie axiale est developpé. Les contraintes posées par les résultats sur la structure à grande échelle des jets sont discutées. Les raies interdites dans les étoiles jeunes de faible masse sont ensuite etudiées. Plusieurs modèles capables d'expliquer les profils observés sont discutés

Ce mémoire présente le développement d'un procédé de prototypage rapide de type impression pour la réalisation de structures céramiques massives à partir d'une poudre de formulation 0,9PbMg0,33Nb0,66O3-0,1PbTiO3. La mise au point de suspensions compatibles avec l'équipement a conduit à sélectionner les meilleurs auxiliaires organiques et à optimiser leur concentration au moyen d'un plan d'expérience. La forte incidence de la granulométrie des poudres utilisées sur le comportement rhéologique des suspensions a été mis en évidence. La généralisation de la loi de Krieger-Dougherty a montré que les taux de charge accessibles dépendent, entre autre, de la morphologie des particules. L'incidence des paramètres de pilotage de la machine, l'analyse des contraintes subies par la suspension et l'évaluation du rapport a permis l'étude du phénomène d'éjection. Des structures 2-2 ont été réalisées et frittées avec une densification correcte et une croissance granulaire limitée
This thesis deals with the development of a rapid prototyping process by printing for the forming of bulk ceramic structures from a powder of 0,9PbMg0,33Nb0,66O3-0,1PbTiO3 formulation. The development of suspensions compatible with the equipment has required the selection of the best organic compounds and the optimization of their concentration through an experimental design. The strong effect of the granulometry of the powders on the rheological behavior of suspensions was highlighted. The extension of the Krieger-Dougherty law has revealed that the maximum powder loading depends on the size distribution and the morphology of the particles. The effect of the driving parameters of the equipment and the evaluation of the stresses applied to the suspension in the machine and the ratio allowed the study of the phenomenon of ejection. Structures 2-2 were carried out and sintered with a correct density and a limited grain growth

Thesis (Ph. D.)--Florida State University, 2006.
Advisor: Anjaneyulu Krothapalli, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed June 5, 2007). Document formatted into pages; contains xxxviii, 658 pages. Includes bibliographical references.

Research was performed to optimize the high-efficiency jet ejector geometry by varying motive velocities from Mach 0.50 to 3.25, and mass flow ratio from 0.02 to 100.0. The high-efficiency jet ejector was simulated by Fluent Computational Fluid Dynamics (CFD) software. A conventional finite-volume scheme was utilized to solve two-dimensional transport equations with the standard k-ε turbulence model. In the optimization study of the constant-area jet ejectors, all parameters were expressed in dimensionless terms. The objective of the study was to investigate the optimal length, throat diameter, and optimal nozzle diameter at any operating conditions. Also, the optimum compression ratio and efficiency were calculated. By comparing simulation results to an experiment, CFD modeling has shown high-quality results. The overall deviation was 8.19%, thus confirming the reliability of the modeling results. The results from the optimization study indicate that the jet ejector efficiency improves significantly compared to a conventional jet-ejector design. In cases with a subsonic motive velocity, the efficiency of the jet ejector is greater than 90%. A high compression ratio can be achieved with greater motive velocity and mass flow ratio. The ejector performance between the optimal jet ejectors and conventional jet ejectors provided by Graham Corporation was compared. The results show that substituting a single optimal jet ejector for a single conventional ejector reduces the motive stream consumption by about 10% to 30%, which could decrease operating costs tremendously. Dimensionless group analysis reveals that the research results are valid for any fluid, operating pressure and geometric scale for a given motive-stream Mach number and momentum ratio. The explanation of how to implement the optimization results and selecting the best operating conditions to minimize the motive stream consumption was included at the end of the dissertation.

This experim ental project aims to describe the influencing factors in the vacuum boiling o f w ater in w ater vapour refrigeration system s Testing was conducted using a 2 kW three-stage steam je t ejector system, w ith barom etric condensers, as the com pression device. Three direct-contact evaporators were used to investigate the boiling phenom ena. T hese were : a through-flow evaporator w here heal and mass transfer rates were established for boiling m echanism s at various positions within the evaporator; a vertical cylinder where small quantities o f w ater were subjected to rapid decom pression and the effects m easured, and a sim ple channel for photographic studies o f the process. Boiling in direct-contact water vapour systems is described herein The vacuum boiling proo ss was found to be controlled by a com bination o f the w ater surface tem perature and the hydrostatic pressure gradient, these being governed by the w ater vapour flow geometry between the w ater surface and ejector suction and convective heat transfer below the boiling region. The contributions o f the various boiling regim es to the total heat transfer are discussed. Heat and mass transfer coefficients and their applicability to evaporator design are presented

Since the mid-1990s there has been an active effort to develop hydrocarbon-fueled power generation and propulsion systems on the scale of centimeters or smaller. This effort led to the creation and expansion of a field of research focused around the design and reduction to practice of Power MEMS (microelectromechanical systems) devices, beginning first with microscale jet engines and a generation later more broadly encompassing MEMS devices which generate power or pump heat. Due to small device scale and fabrication techniques, design constraints are highly coupled and conventional solutions for device requirements may not be practicable.

This thesis describes the experimental investigation, modeling and potential applications for two classes of microscale jet pumps: jet ejectors and jet injectors. These components pump fluids with no moving parts and can be integrated into Power MEMS devices to satisfy pumping requirements by supplementing or replacing existing solutions. This thesis presents models developed from first principles which predict losses experienced at small length scales and agree well with experimental results. The models further predict maximum achievable power densities at the onset of detrimental viscous losses.

Dissertation

碩士
國立臺灣大學
機械工程研究所
81
The objective of present study is to investigate the performance characteristics of ejectors in the jet refrigeration system experimentally. By changing the sizes of the ejectors, the effects of changes of sizes are understood, compared and applied in the future design. The comparison of pressure distribution in the ejectors between the results calculated from the literatures and the experimental data shows good agreement, and clearly demonstrates the relation- ships of the flow field, the shock positions and the back pressure in the ejectors. By analyzing the suction phenomena at different primary, secondary and mixed pressure, the mass flow rate ratios of choking and the critical pressure are determined. Therefore, the ejectors with different working fluid and sizes can be compared. The working fluid used are R114 and R113, the performance of ejectors is compared. The performance curves of R113 are compared with literatures in order to study the effects of different sizes of ejectors. The ejector size variables are defined as the throat area and position of the primary nozzle, and the lengthes of the throat region and the diffuser of the ejectors for the theoreti- cal analysis. By the effects and performance of changes of sizes, the best size of ejectors is approached. In the mean time, to upgrade the efficiency of the jet refrigeration system, the per- formance curves of the ejectors can be used to match in multi- stage and multi-effect systems.

碩士
國立臺灣大學
機械工程研究所
81
Using two-dimensional axisymmetric flow model and MacCormack TVD scheme, the flow fields of freon ejectors are obtained. The comparison of pressure distribution in the ejectors between experiment data and the results caculated by computer shows good agreement. Therefore, this analytic model is adaptable to evaluate ejector flow. The performance curves of ejectors with various geometry are constructed from the calculated results. Through these graphs the influence of main geometric parameter on ejector performance is shown, and the features of high performance ejector are summarized. Finally, further analysis is made to obtain the optimum geometry of an ejector with the best performance in order to improve the efficiency of the jet refrigeration system. In order to predict the performance of the ejectors more correctly, it's necessary to change the analytic model. Two new models are used in this paper, the first one is real gas model and the second one is viscous model. The real gas model can promit more exactly performance, but the viscous effect can't make a conculsion untill more computations are done.

Rapid mixing and spreading of supersonic jets are two important characteristics in supersonic ejectors, noise reduction in jets and fuel mixing in supersonic combustion. It helps in changing the acoustic and thermal signature in supersonic exhaust. The supersonic nozzles in most cases result in compressible mixing layers. The subsonic nozzles form incompressible mixing layers but at high Mach numbers even they form compressible mixing layers. Compressible mixing layers have been found to have much lower mixing and spreading rates than incompressible mixing layer Birch & Eggers (1972). In order to enhance the spreading and mixing of mixing layers from supersonic nozzles various active and passive methods have been deviced. Active methods include fluid injection, fluid lobes and plasma actuation. Passive methods are mostly based on modifying the nozzle geometry such that the fluid expansion is ideal or the shock cell is broken. Many nozzles with exotic shapes have been developed to obtain mixing enhancements in supersonic jets Gutmark et al. (1995). To achieve enhanced mixing an innovative nozzle named as the Elliptic Sharp Tipped Shallow (ESTS) lobed nozzle has been developed in L.H.S.R., I.I.Sc., India Rao & Jagadeesh (2014). This nozzle has a unique geometry involving elliptical lobes and sharp tips. These lobes are generated using a simple manufacturing process from the throat to the exit. This lobed and sharp tipped structure introduces stream wise vortices and azimuthal velocity components which must help in enhanced mixing and spreading. The ESTS lobed nozzle has shown mixing enhancement with 4 lobes. The spreading rate was found to be double of the reference conical nozzle. This thesis is motivated by the need to investigate the flow physics involved in the ESTS lobed nozzle. The effect of varying the number of lobes and the design Mach number of the nozzle on the mixing and spreading characteristics will be further discussed. Visualisation studies have been performed. The schlieren and planar LASER Mie scattering techniques have been used to probe the flow. Instantaneous images were taken at axial planes with the reference conical and ESTS nozzles with three, four, five and six lobes. The nozzles are for design Mach number 2.0 and 2.5. The stagnation chamber pressure was maintained to obtain over expanded, ideally expanded and under expanded flows. LASER scattering was obtained by seeding the flow with water to observe the behaviour of the primary flow. The condensation of moisture due to the cold primary flow mixing with the ambient air was exploited to scatter laser and observe the flow structures in the mixing layer. A comparison of the images of the reference conical nozzle and the ESTS lobed nozzles shows changes in the mixing layers due to the ESTS lobed nozzles. The image of the reference conical nozzle shows a distinct potential core and mixing layers all along the length of the image. For the ESTS lobed nozzles this distinction becomes unclear shortly after the nozzle exit. Thus mixing of the primary flow and ambient air is seen to be enhanced in the case of all the ESTS lobed nozzles. The flow in the case of the ESTS lobed nozzles if found to be highly non axis symmetric. The starting process of the nozzles has been visualised using time resolved schlieren. Image processing was performed on the nozzles to quantify the spread rate. The shock structure of the nozzles has been studied and found to be modified due to the lobed geometry. The level of convolution of the mixing layer due to the lobed structure has been studied using fractal analysis. The four lobed nozzle was found to have the highest spread rate and th most convoluted shear layer. Hence this nozzle was further studied using background oriented schlieren and particle image velocimetry to quantify the flow field. These experimental results have been compared with CFD simulations using the commercial software CFX5. The computations and experiments don’t match accurately but the trends match. This allows for simulations to be used as a good first approximation. The acoustic properties of a jet are dependent on the flow structure behaviour. The ESTS lobes have been found to change the flow structure. Hence the ESTS lobed nozzle was predicted to change the acoustic signature of the flow. The acoustic measurements of the flow were carried out at National Aerospace Laboratories, Bengaluru. The screech of the overexpanded flow was seen to be eliminated and the overall sound levels were found to have been reduced in all cases. Thus the lobed nozzle was found to have acoustic benefits over the reference conical nozzle. Thus the ESTS lobed nozzle has been studied and compared with the conical nozzle using several methods. The changes due to the lobed structure have been studied quantitatively. Future studies would focus on the change in thrust due to the lobed structure. Also new geometries have been proposed inspired by the current design but with possible thrust benefits or manufacturing benefits.