Download or read book Performance of Thrust Augmenting Ejectors written by Paul Allen Van and published by . This book was released on 1971 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation of High Performance Short Thrust Augmenting Ejectors written by and published by . This book was released on 1983 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Workshop on Thrust Augmenting Ejectors written by and published by . This book was released on 1979 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thrust Augmentation Study of High Performance Ejectors written by John E. Minardi and published by . This book was released on 1983 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Thrust Augmenting Ejectors written by Morton Alperin and published by . This book was released on 1981 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Prediction and Evaluation of Thrust Augmenting Ejector Performance at the Conceptual Design Stage written by and published by . This book was released on 1980 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Entrainment and Mixing in Thrust Augmenting Ejectors written by L. Bernal and published by . This book was released on 1982 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Analytical Investigation of High Performance Short Thrust Augmenting Ejectors written by Tah-Teh Yang and published by . This book was released on 1982 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Inlet and Diffuser Effects on Thrust Augmenting Ejectors written by S. G. Reznick and published by . This book was released on 1982 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book An Experimental Study of Rectangular and Circular Thrust Augmenting Ejectors written by and published by . This book was released on 1981 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Lifting Surface Theory for Thrust Augmenting Ejectors written by P. M. Bevilaqua and published by . This book was released on 1982 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: The circulation theory of airfoil lift has been applied to predict the static performance of thrust augmenting ejectors. The ejector shroud is considered to be 'flying' in the velocity field induced by the entrainment of the primary jets, so that the thrust augmenting force is viewed as analogous to the lift on a wing. Vortex lattice methods are used to compute the augmentation from the surface pressures on the shroud. The thrust augmentation is shown to depend on the length and shape of the shroud, as well as its position and orientation. Predictions of this new theory are compared with the results of classical momentum theories for calculating the augmentation from the stream thrust. (Author).
Download or read book Thrust Augmentation Study of High Performance Ejectors written by and published by . This book was released on 1983 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Experimental Investigation of a Thrust Augmenting Ejector written by Hidayat Wiradimadja and published by . This book was released on 1985 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An ejector is basically a jet pump in which the kinetic energy of the jet is made to impart motion to the fluid surrounding it. During this process, in a well design system, the ejector as a whole experiences a thrust much higher than that of the jet alone. In principle, an ejector is nothing but a jet surrounded by a shroud. This investigation concerns the performance of a two- dimensional ejector with its primary jet excited by a novel method. A constant area duct was used in this experiment. The velocity of the jet at the exit was subsonic. Maximum thrust was obtained when the ejector to jet exit area ratio was about 35. Under this condition a thrust augmentation ratio of 1.65 was achieved, with the jet excited at 20 Hz, whereas without excitation it was only 1.40. The mixing characteristics of the jet under excitation was examined using flow visualization techniques. Smoke filaments illuminated by a sheet of powerful light and schlieren optics with the jet heated were used. Excitation of the jet was found to generate large vortex-like flow structures which might be responsible for enhanced mixing. These vortices extended to considerable distances on both sides of the jet.
Download or read book An Experimental Investigation of Two Dimensional Thrust Augmenting Ejectors written by L. Bernal and published by . This book was released on 1984 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experiments were performed with subsonic and underexpanded choked two-dimensional primary nozzle ejector flow systems 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. Key findings include: (1) Primary jet growth is significantly altered by the ejector shroud. (2) Primary jet turbulent characteristics when normalized with the local mean centerline velocity are in agreement with those for the free-jet. (3) In the neighborhood of the ejector shroud the flow field can be classified into two regions--the potential flow region and the region close to the ejector exit which is dominated by the turbulent transport. (4) Pressure recovery is very sharp in the first region and is more gradual in the region close to the ejector exit. The investigation is continuing toward the near-term objectives of obtaining measurements within diffused flow and with heated primary air. This volume emphasizes the laser doppler velocimetry developed especially for this program. Part II (AD-A154 083) presents detailed cold flow measurements along with preliminary primary hot flow data.
Download or read book A Simple Model of Pulsed Ejector Thrust Augmentation written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-29 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple model of thrust augmentation from a pulsed source is described. In the model it is assumed that the flow into the ejector is quasi-steady, and can be calculated using potential flow techniques. The velocity of the flow is related to the speed of the starting vortex ring formed by the jet. The vortex ring properties are obtained from the slug model, knowing the jet diameter, speed and slug length. The model, when combined with experimental results, predicts an optimum ejector radius for thrust augmentation. Data on pulsed ejector performance for comparison with the model was obtained using a shrouded Hartmann-Sprenger tube as the pulsed jet source. A statistical experiment, in which ejector length, diameter, and nose radius were independent parameters, was performed at four different frequencies. These frequencies corresponded to four different slug length to diameter ratios, two below cut-off, and two above. Comparison of the model with the experimental data showed reasonable agreement. Maximum pulsed thrust augmentation is shown to occur for a pulsed source with slug length to diameter ratio equal to the cut-off value.Wilson, Jack and Deloof, Richard L. (Technical Monitor)Glenn Research CenterTHRUST AUGMENTATION; MATHEMATICAL MODELS; FLOW VELOCITY; HARTMANN-SPRENGER TUBES; VORTEX RINGS; PULSED JET ENGINES; EJECTORS...
Download or read book A Compact Thrust Augmenting Ejector Experiment written by Richard B. Fancher and published by . This book was released on 1970 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: The report briefly reviews the potential momentum thrust performance of ejectors. In addition to thrust performance, an ejector's utility to a V/STOL propulsion system is determined by several other factors including ejector size and airducting requirements. A survey of previous ejector experimental results are presented for ejectors with inlet area ratios in the neighborhood of 15 to 20. A compact two-dimensional ejector experiment with an inlet area ratio of 19 is described. This ejector with a 1.9 area ratio exit diffuser achieved a thrust augmentation ratio of 1.71 and 1.78 for an ejector length to minimum channel width ratio of 3.5 and 5.1 respectively. It is believed that improvements in primary injection techniques were responsible for this favorable thrust performance. (Author).
Download or read book An Experimental Investigation of Two Dimensional Thrust Augmenting Ejectors written by L. Bernal and published by . This book was released on 1984 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow-field within a two-dimensional thrust augmenting ejector has been documented experimentally. Results are presented on the mean velocity field and the turbulent correlations by laser doppler velocimeter, surface pressure distribution, surface temperature distribution, and thrust performance for two shroud geometries. The maximum primary nozzle pressure ratio tested was 3.0. The tests were conducted at primary nozzle temperature ratios of 1.0, 1.8, and 2.7. Two ejector characteristics lengths were identified based on the dynamics of the ejector flow field--a minimum length below which no significant mixing occurs, and a critical length associated with the development of U'V' correlation in the ejector. These characteristic lengths divide the ejector flow field into three distinctive regions: the entrance region where there is no direct interaction between the primary flow and the ejector shroud; the interaction region where there is an increased momentum of induced flow near the shroud surface; and a 'pipe' flow region characterized by an increased skin friction. The effect of the coflowing induced flow shown to produce inside the ejector a centerline velocity that increased over the free-jet data. The normalized turbulent correlations are found to be 25% lower than those in free jets. Effects of pressure ratio on the ejector flow field are small. Present measurements also show that the ejector performance was not influenced by the primary nozzle temperature ratio up to 2.7.
