The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
A M Birk - One of the best experts on this subject based on the ideXlab platform.
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Experimental Investigation of the Effects of Nozzle Length on the Performance of Low Mach Number Air-Air Ejector With Entraining Diffuser
Volume 2: Aircraft Engine; Coal Biomass and Alternative Fuels; Cycle Innovations, 2013Co-Authors: A. Namet-allah, A M BirkAbstract:The core flow separation in Air-Air Ejectors is significantly affected by the length of the exhaust nozzle. This length was changed by moving the annulus’ center body end 4, 7, and 12 cm upstream and 1 cm downstream of the nozzle inlet. The velocity profiles at the nozzle exit were measured at different mass flow rates and at 10, 20 and 30 degree swirl angles. These measurements were also conducted at two annulus’ center body end positions with elliptical and square shapes, 12 and 7 cm upstream of the nozzle inlet, using two nozzle exit diameters. At 4, 7, and 12 cm upstream and 1 cm downstream of the nozzle inlet, the ejector performance was also measured at ambient temperature and at different flow swirl angles. It was found that the square shape of the annulus’ center body decreased the size of the core flow separation behind the annulus center body compared with the elliptical shape by improving the flatness of the flow velocity at the nozzle exit under different mass flow rates, swirl angles, positions of the annulus’ center body, and nozzle exit diameters. It was seen that moving the end of the annular center body upstream has considerable effects on the size and nature of the core separation behind the annulus’ center body and consequently on the ejector performance.At a zero swirl angle, the ejector pumping ratio slightly increased, decreased, and then increased again by moving the annulus’ center body from 12 cm to 7 cm upstream, from 7 cm to 4 cm upstream, and from 4 cm upstream to 1 cm downstream of the nozzle inlet respectively. These changes in the annulus’ center body position caused the back pressure coefficient to decrease, increase, and then increase again. The same trend in pumping ratio and back pressure was observed for both 10 and 20 degree flow swirl angle conditions when the annulus’ center body was moved as described.Copyright © 2013 by ASME
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Numerical Investigation of an Air-Air Ejector with Diffuser for use in Gas Turbine Exhaust Systems
49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011Co-Authors: David J. Cerantola, Ames Crawford, A M BirkAbstract:An ejector is a simple device used to drive a secondary Air flow of cool ambient Air using the momentum of a primary Air flow. Gas turbineejector exhaust systems are commonly used to pumpengine enclosure ventilation Air or provide exhaust cooling. Reduction in plume temperature is particularly desirable for military Aircraft to avoid detection from infra-red guided missiles. This review evaluates the capability of Reynolds-averaged Navier-Stokes computational fluid dynamics on short cylindrical Air-Air Ejectors whose primary jet flow has Reynolds number ReD1 = 2.0·10 6 and Mach number M1 = 0.23. Three numerical studies were performed using the realizable k-e turbulence model: (1) rounded secondary inlets, (2) ejector length, and (3) diffuser divergence angle. Results for the area ratio two mixing tubes show that increasing the radius of the rounded inlet, lengthening the ejector to at least seven mixing tube diameters, and specifying a divergence angle of 10 ◦ on an area ratio two diffuser give an exhaust system with the best pumping, pressure recovery, and mixing. Diffuser pressure coefficient was compared against experimental results and was over-predicted in excess of 22% due to the implementation of an isotropic turbulence model.
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optimizing the performance of Air Air Ejectors with triangular tabbed driving nozzles
ASME Turbo Expo 2007: Power for Land Sea and Air, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an experimental investigation into optimizing the performance of Air-Air Ejectors with triangular tabbed driving nozzles. Mixing tabs have been shown to improve ejector performance, but at the cost of increased back-pressure. Ejector performance was evaluated on the basis of pumping, mixing, and back-pressure. It was discovered that mixing-tube inlet treatment influenced the ability of Ejectors to entrain ambient Air. It was also found that although mixing improved as a function of increased mixingtube length, maximum pumping occurred when the mixing-tube was approximately four nozzle diameters in length. Lastly, for a given overall ejector length, increased standoff was found to be more beneficial than increased mixing-tube length. Optimal ejector geometry was defined by the configuration that generated maximum mixing and maximum pumping for minimal increases in back-pressure.Copyright © 2007 by ASME
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cfd realizable k e and cold flow testing for the design of Air Air Ejectors with triangular tabbed driving nozzles
ASME Turbo Expo 2007: Power for Land Sea and Air, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an investigation in which a commercial CFD software package has been used to evaluate the performance of Air-Air Ejectors with triangular tabbed driving nozzles. The Realizable k-e turbulence model was employed and CFD predictions were evaluated against experimental results. Ejector performance was measured on the basis of pumping, mixing, and back-pressure. It was discovered that CFD models were generally capable of predicting trends in pumping and mixing, but were unable to account for appropriate magnitude. In addition, CFD did not accurately represent the strength of the streamwise vortices generated by the tabs. At increased tab angles, CFD predicted values of back-pressure very well. However, under the 90° tab configuration, back-pressure was severely under-predicted.Copyright © 2007 by ASME
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CFD (Realizable K-ε) and Cold-Flow Testing for the Design of Air-Air Ejectors With Triangular Tabbed Driving Nozzles
Volume 6: Turbo Expo 2007 Parts A and B, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an investigation in which a commercial CFD software package has been used to evaluate the performance of Air-Air Ejectors with triangular tabbed driving nozzles. The Realizable k-e turbulence model was employed and CFD predictions were evaluated against experimental results. Ejector performance was measured on the basis of pumping, mixing, and back-pressure. It was discovered that CFD models were generally capable of predicting trends in pumping and mixing, but were unable to account for appropriate magnitude. In addition, CFD did not accurately represent the strength of the streamwise vortices generated by the tabs. At increased tab angles, CFD predicted values of back-pressure very well. However, under the 90° tab configuration, back-pressure was severely under-predicted.Copyright © 2007 by ASME
S F Mcbean - One of the best experts on this subject based on the ideXlab platform.
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optimizing the performance of Air Air Ejectors with triangular tabbed driving nozzles
ASME Turbo Expo 2007: Power for Land Sea and Air, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an experimental investigation into optimizing the performance of Air-Air Ejectors with triangular tabbed driving nozzles. Mixing tabs have been shown to improve ejector performance, but at the cost of increased back-pressure. Ejector performance was evaluated on the basis of pumping, mixing, and back-pressure. It was discovered that mixing-tube inlet treatment influenced the ability of Ejectors to entrain ambient Air. It was also found that although mixing improved as a function of increased mixingtube length, maximum pumping occurred when the mixing-tube was approximately four nozzle diameters in length. Lastly, for a given overall ejector length, increased standoff was found to be more beneficial than increased mixing-tube length. Optimal ejector geometry was defined by the configuration that generated maximum mixing and maximum pumping for minimal increases in back-pressure.Copyright © 2007 by ASME
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cfd realizable k e and cold flow testing for the design of Air Air Ejectors with triangular tabbed driving nozzles
ASME Turbo Expo 2007: Power for Land Sea and Air, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an investigation in which a commercial CFD software package has been used to evaluate the performance of Air-Air Ejectors with triangular tabbed driving nozzles. The Realizable k-e turbulence model was employed and CFD predictions were evaluated against experimental results. Ejector performance was measured on the basis of pumping, mixing, and back-pressure. It was discovered that CFD models were generally capable of predicting trends in pumping and mixing, but were unable to account for appropriate magnitude. In addition, CFD did not accurately represent the strength of the streamwise vortices generated by the tabs. At increased tab angles, CFD predicted values of back-pressure very well. However, under the 90° tab configuration, back-pressure was severely under-predicted.Copyright © 2007 by ASME
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CFD (Realizable K-ε) and Cold-Flow Testing for the Design of Air-Air Ejectors With Triangular Tabbed Driving Nozzles
Volume 6: Turbo Expo 2007 Parts A and B, 2007Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an investigation in which a commercial CFD software package has been used to evaluate the performance of Air-Air Ejectors with triangular tabbed driving nozzles. The Realizable k-e turbulence model was employed and CFD predictions were evaluated against experimental results. Ejector performance was measured on the basis of pumping, mixing, and back-pressure. It was discovered that CFD models were generally capable of predicting trends in pumping and mixing, but were unable to account for appropriate magnitude. In addition, CFD did not accurately represent the strength of the streamwise vortices generated by the tabs. At increased tab angles, CFD predicted values of back-pressure very well. However, under the 90° tab configuration, back-pressure was severely under-predicted.Copyright © 2007 by ASME
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the performance of Air Air Ejectors with triangular tabbed driving nozzles
ASME Turbo Expo 2006: Power for Land Sea and Air, 2006Co-Authors: S F Mcbean, A M BirkAbstract:This paper describes an experimental investigation into the effects of geometrical variations on ejector system performance when the driving nozzle includes delta mixing tabs. Mixing tabs have been shown to provide good mixing performance with comparable back-pressure penalties to other types of enhanced mixing nozzles. The performance parameters of most interest are pumping, mixing, and back-pressure. Geometric parameters studied include standoff distance, mixing-tube diameter, and tab angle. Experimental testing showed significant performance improvements in mixing and pumping with a decrease in tab angle. Maximum mixing was found to occur with tab angles positioned at 120°. Exceptional mixing was also observed with increased standoff. Back-pressure was shown to increase with increasing standoff and decreasing tab angle, but was not affected by mixing-tube diameter. In addition, a zone of recirculation was identified at the entrance to the mixing-tube. This zone is thought to have an influence on ejector performance.Copyright © 2006 by ASME
D P Hollister - One of the best experts on this subject based on the ideXlab platform.
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preliminary Air flow and thrust calibrations of several conical cooling Air Ejectors with a primary to secondary temperature ratio of 1 0
2013Co-Authors: W K Greathouse, D P HollisterAbstract:An investigation was made of the performance of nine conical cooling-Air Ejectors at primary jet pressure ratios from 1 to 10, secondary pressure ratios to 4.0, and a temperature ratio of unity. This phase of the investigation was limited to conical Ejectors having shroud exit to primary nozzle exit diameter ratios of 1.06 and 1.40, with several spacing ratios for each. The experimental results indicated that the pumping range and amount of cooling-Air flow obtained with a 1.06 diameter ratio ejector were relatively small for cooling purposes but that the maximum possible thrust loss, which occurred with no secondary flow, was only 7 percent of convergent nozzle thrust. The 1.40 diameter ratio ejector produced a large cooling Air flow and showed a possible thrust loss of 29.5 percent with no cooling Air flow. Thrust gains were attained with Ejectors of both diameter ratios at secondary pressure ratios greater than 1.0. The limiting primary pressure ratio below which an ejector can operate at a specific secondary pressure ratio (cut-off point) may be estimated for various flight conditions from data contained herein.
A M Eldesoukey - One of the best experts on this subject based on the ideXlab platform.
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study of the configuration and performance of Air Air Ejectors based on cfd simulation
Journal of Aeronautics and Aerospace Engineering, 2017Co-Authors: A M Elzahaby, Mofreh H Hamed, Z M Omara, A M EldesoukeyAbstract:This paper describes a numerical study of gas-gas ejector performance for different operating conditions and geometrical configurations. The performance of ejector obtained based on a simulation procedure of linearized and axisymmetric subsonic and supersonic flow using Fluent Package. A conventional finite-volume scheme utilized to solve two-dimensional transport equations with the standard k-ω SST turbulence model. The model is solved in three regions namely, the primary flow nozzle, the secondary flow channel, and the region of interaction between the supersonic nozzle jet and the secondary flow. The effect of gas motive pressure the mixing part and tail section (pipe or diffuser) geometry on the ejector performance are studied. The computational results are validated using published experimental data with acceptable agreements. The numerical results indicate that the ejector geometry has a pronounced effect on the flow parameters (i.e., pressure and gas velocity) and the ejector performance. In addition, predicted numerical results indicate that when the motive-stream velocity exceeds the speed of sound, shock waves are unavoidable inside Ejectors and that shock wave pattern in mixing part has a dominant effect on ejector performance. In addition, the results indicate that the shock location inside the nozzle and the separation point are affected by the motive pressure. The results show also that configuration with convergent-divergent mixing section is much better for mixing process than the other tested configurations.
W K Greathouse - One of the best experts on this subject based on the ideXlab platform.
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preliminary Air flow and thrust calibrations of several conical cooling Air Ejectors with a primary to secondary temperature ratio of 1 0
2013Co-Authors: W K Greathouse, D P HollisterAbstract:An investigation was made of the performance of nine conical cooling-Air Ejectors at primary jet pressure ratios from 1 to 10, secondary pressure ratios to 4.0, and a temperature ratio of unity. This phase of the investigation was limited to conical Ejectors having shroud exit to primary nozzle exit diameter ratios of 1.06 and 1.40, with several spacing ratios for each. The experimental results indicated that the pumping range and amount of cooling-Air flow obtained with a 1.06 diameter ratio ejector were relatively small for cooling purposes but that the maximum possible thrust loss, which occurred with no secondary flow, was only 7 percent of convergent nozzle thrust. The 1.40 diameter ratio ejector produced a large cooling Air flow and showed a possible thrust loss of 29.5 percent with no cooling Air flow. Thrust gains were attained with Ejectors of both diameter ratios at secondary pressure ratios greater than 1.0. The limiting primary pressure ratio below which an ejector can operate at a specific secondary pressure ratio (cut-off point) may be estimated for various flight conditions from data contained herein.
