Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. 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.

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 (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2003. / Thesis advisor(s): Knox T. Millsaps, Jr. Includes bibliographical references (p. 49-50). Also available online.

Tese de mestrado integrado. Engenharia Mecânica. Universidade do Porto. Faculdade de Engenharia. 2011

An experimental and numerical study of air-air bent exhaust ejectors was carried out. The objective of the study was to determine the effect of a bend on the performance of exhaust ejectors. The ejectors consisted of nozzles, mixing tubes and in some cases entraining diffusers. As part of this study the effect of swirl in the primary flow and the temperature ratio of the primary to the secondary flow were also investigated. The study included testing of round and oblong sectioned ejectors with and without entraining diffusers. The experimental testing was performed on two different wind tunnels capable of blowing air at a maximum mass flow rate of 2.2 kg/s at ambient and elevated temperatures. Flow measurements were made upstream of the nozzle, at the nozzle exit and at the exit of the ejector. Pumping, pressure rise and total efficiency of the ejector were studied with respect to the bend angle, swirl angle and the primary to secondary flow temperature ratio. A commercial CFD code was used to evaluate the effectiveness of commercial CFD using limited resources for designing of such devices. The pumping ratio and pressure rise decrease with the increase in the degree of bend. Swirl up to a certain angle has a useful effect on the performance of a bent ejector. The entraining diffuser enhances the performance of a bent ejector. The CFD models based on commercial solver were able to predict the flow structures and the variation of the performance parameters with the bend and swirl angle. However, generally the CFD models were not able to predict the exact values of the performance parameters. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2008-03-31 05:53:54.89 / NSERC DND WR Davis

No description available.

Cold-flow tests were performed using a simulated Air Augmented Rocket (AAR) operating as a mixer-ejector in order to investigate the effects of varied primary nozzle lip thickness on mixing and entrainment. The simulated primary rocket ejector was supplied with nitrogen at a maximum chamber stagnation pressure of 1712 psi, and maximum flow rate of 1.67 lbm/s. Secondary air was entrained from a plenum, producing pressures as low as 6.8 psi and yielding maximum stagnation pressure ratios as high as 160. The primary ejector nozzles each had an area ratio of approximately 20, yielding average primary exit Mach numbers between 4.34 and 4.57. The primary flow was ejected into an 18.75 inch-long mixing duct with a rectangular cross-sectional area of 2.10 in2. The secondary flow was entrained into the mixing duct through a total cross section of 0.94 in2. Two mixing duct configurations were used, one with plexiglass upper and lower surfaces for flow visualization and one with pressure ports along the lower surface for primary plume measurements. Shadowgraph images were used to characterize the mixing duct flow field, while pressure and temperature instrumentation allowed for calculation of various ejector performance characteristics. Experimentally-calculated performance characteristics were compared to inviscid theoretical predictions. Varying degrees of flow field asymmetry were observed with each nozzle. Test repeatability was found to be excellent for all nozzles. Several distinct phenomena were observed in both the primary plume and secondary streams. The duration of secondary flow choking was found to be inversely proportional to nozzle lip thickness, due to the primary plume being physically closer to the secondary flow with a thinner nozzle lip. This indicated that the ejector’s ability to choke the secondary flow is primarily an inviscid phenomenon. Secondary flow blockage was demonstrated in two consecutive tests using the thickest nozzle lip. Only the left secondary duct became blocked in each case. Blockage was only demonstrated in the centerline pressure configuration, so no visual evidence was able to support the blocked flow theory. At every pressure ratio, entrainment ratio was shown to increase with nozzle lip thickness. The original conical nozzle produced the largest level of entrainment, indicating that the angle of primary flow impingement was the largest contributing factor to secondary entrainment. The increase in efficiency resulting from a bell-mouth nozzle was less than the increase in entrainment efficiency of a conical nozzle, indicating that the conical design was more efficient overall for air augmented rocket applications.

No description available.

This diploma thesis deals with the flow modelling in the ejector using the FLUENT software. It develops a diploma thesis created in the past, where a mathematical flow model in the ejector was created and experimentally tested. The aim of this work is to analyze the ejector calculations and to model a flow in an ejector of the same shape as in the experiment and under the same conditions, too. Another objective was to assess the influence of the throat length and to examine if the pressure in the ejector mixing chamber remains constant. Finally, the disagreement between the experimental figures and the ones gained from the mathematical model of the ejector are discussed.