Performance Of Thrust Augmenting Ejectors
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Experimental Investigation of High Performance, Short, Thrust Augmenting Ejectors
| Author | : |
| Publisher | : |
| Total Pages | : 69 |
| Release | : 1983 |
| Genre | : |
| ISBN | : |
Results of an experimental investigation concerning the design and testing of air-to-air thrust augmenting ejectors utilizing short curved-wall diffusers are presented. These ejectors were designed primarily according to the procedure established in an analytical research effort sponsored by DTNSRDC from 1980-1981. Two of the three ejectors tested have identical mixing chambers. The mixing chamber inlet area to the primary nozzle area ratio lambda was 40. The overall ejector length-to-mixing chamber diameter ratios L/D(overall) were 6.09 and 6.16; diffuser area ratios AR(diff) were 1.33 and 1.46, respectively. The third ejector had an L/D(overall) of 6.02, a lambda of 20 and an AR(diff) of 1. 26. The best observed thrust augmentation ratio phi and the modified thrust augmentation ratio phi sub 2 were 2.11 and 1.91 respectively for a sonic primary jet. The modified thrust augmentation ratio phi sub 2 accounts for the penalty of suction in preventing flow separation in the diffuser. These levels of thrust ratio were derived from velocity measurements at the ejector exit. Independent thrust measurements obtained with strain gages on the mixing chamber agree with the force calculated from the momentum data. The experimentally observed ejector performance data correlated well with the predicted values. (Author).
Thrust Augmentation Study of High Performance Ejectors
| Author | : John E. Minardi |
| Publisher | : |
| Total Pages | : 92 |
| Release | : 1983 |
| Genre | : Aerodynamics, Supersonic |
| ISBN | : |
A technique is developed for determining a representative value of the maximum efficiency that can be achieved with high performance ejectors when operating on the supersonic solution branch of an ejector. These efficiencies are used to calculate thrust augmentation for an ejector over a wide range of parameters including operation with a hypothetical engine. Reasonable values of thrust augmentation can be achieved at low subsonic flight mach numbers. However, at flight Mach numbers near one, little or not thrust augmentation was found. At supersonic flight Mach numbers, thrust augmentation was achieved. Basic studies indicated that the effects of temperature was opposite at subsonic and supersonic flight Mach numbers. Thrust augmentation decreased with increasing temperature at subsonic Mach number sand increased with increasing temperature at supersonic Mach numbers.
Thrust Augmenting Ejectors
| Author | : Morton Alperin |
| Publisher | : |
| Total Pages | : 49 |
| Release | : 1981 |
| Genre | : |
| ISBN | : |
A discussion of the development of the compact jet-diffuser ejectors utilized for hovering and low speed flight propulsion has been presented. This is followed by a description of ideal ejector performance as derived from a compressible flow theory, over the range of flight speeds from zero to supersonic speed. These analyses introduced the concepts of ejector configuration optimization and the validity of the so-called 'second solution' to the mixing problem, wherein the flow after complete mixing is supersonic. The ideal performance of thrust augmenting ejectors designed under this 'second solution' has been shown to be far superior to those designed by conventional methods. The ability of properly designed ejectors to utilize the thermal energy of injected gas for the production of useful energy has also been described. Finally, the influence of major losses has been discussed, including means for avoiding excessive performance degradation by proper optimization of the geometry of the ejector in view of these losses.
Prediction and Evaluation of Thrust Augmenting Ejector Performance at the Conceptual Design Stage
| Author | : |
| Publisher | : |
| Total Pages | : 58 |
| Release | : 1980 |
| Genre | : |
| ISBN | : |
The performance characteristics of thrust augmenting ejectors, based on a computerized one-dimensional analysis technique, are shown. Various loss mechanisms within the ejector are described and the sensitivity of the ejector performance to these loss mechanisms are illustrated. Performance estimates have been made for several ejector configurations for which experimental data are available. Despite the assumptions that have to be made, in order that the problem be tractable for the one dimensional analysis, good agreement between the predicted and experimental values have been obtained. Other more complex (2 D and 3 D) codes have also been examined but were found to be expensive to run and in some cases limited in application. (Author).
Entrainment and Mixing in Thrust Augmenting Ejectors
| Author | : L. Bernal |
| Publisher | : |
| Total Pages | : 102 |
| Release | : 1982 |
| Genre | : |
| ISBN | : |
Experiments have been performed with subsonic and underexpanded choked two-dimensional primary nozzle ejector flow system without diffusion to evaluate the role of entrainment and mixing in thrust augmentation. Two-component Laser Doppler velocity measurements (mean and fluctuating values), thrust measurements, ejector shroud surface pressure measurements and flow visualization were used to determine the evolution of the velocity profiles and their relationship to the ejector performance.
Analytical Investigation of High Performance, Short, Thrust Augmenting Ejectors
| Author | : Tah-Teh Yang |
| Publisher | : |
| Total Pages | : 60 |
| Release | : 1982 |
| Genre | : Ship propulsion |
| ISBN | : |
A procedure for analyzing thrust augmenting ejectors having a short, curved-wall diffuser is presented. In this type of diffuser a shear flow is admitted at the inlet and a set of auxiliary ejectors is used to provide the necessary boundary layer control. Several computer programs are used in the analytical procedure. These computer programs are either outlined or referenced in the open literature. A user's manual is provided in the Appendices of this report. A discussion of the geometries and performances, including thrust augmentation ratios, of two sample ejectors determined by use of this analytical procedure with mixing chamber contraction as an optimization parameter is presented. Use of the mixing chamber length as an optimization parameter is also discussed. (Author).
Inlet and Diffuser Effects on Thrust Augmenting Ejectors
| Author | : S. G. Reznick |
| Publisher | : |
| Total Pages | : 12 |
| Release | : 1982 |
| Genre | : |
| ISBN | : |
Effects of primary jet inlet nozzle configuration and diffuser geometry on the thrust augmentation of circular and rectangular ejectors are investigated in an experimental study. The rectangular ejector inlet nozzle configurations consist of either one, two, or three slot nozzles. The circular ejector inlet nozzles consist of slot nozzles placed either across the inlet or around the inlet periphery. Diffuser geometry is varied primarily by changing the diffuser area ratio. Effect on thrust performance of the primary flow injection angle relative to the inlet walls is investigated. Effects of side-wall, end-wall, and diffuser blowing on thrust performance and diffuser stall also are considered.
An Experimental Study of Rectangular and Circular Thrust Augmenting Ejectors
| Author | : |
| Publisher | : |
| Total Pages | : 78 |
| Release | : 1981 |
| Genre | : |
| ISBN | : |
A short rectangular ejector and two circular ejectors were tested to determine the effects of primary nozzle configuration and geometry on thrust augmentation. The primary nozzle configurations consisted primarily of slot nozzles which injected fluid parallel to the diffuser walls and achieved Coanda type flow at the throat. Results of the rectangular ejector tests indicate that thin plates installed in the mixing chamber or the diffuser, increase mixing but decrease thrust augmentation. A continuous slot nozzle, modified to create four discrete jets at the inlet, improved mixing and thrust augmentation compared to the original design. Thrust augmentation ratio increased from 1.4 to 1.58. The circular ejector primary nozzles consisted of a continuous slot 'torus' nozzle and individual slot nozzles which could be symmetrically placed around the inlet periphery. A nozzle configuration using 16 slot nozzles on the periphery of the inlet face gave the best performance. A thrust augmentation ratio of 2.0 was achieved.
