Thrust Augmenting Ejectors

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.

A Control-Volume Method for Analysis of Unsteady Thrust Augmenting Ejector Flows

A Control-Volume Method for Analysis of Unsteady Thrust Augmenting Ejector Flows
Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
Total Pages: 170
Release: 2018-11-21
Genre: Science
ISBN: 9781731496843

A method for predicting transient thrust augmenting ejector characteristics is presented. The analysis blends classic self-similar turbulent jet descriptions with a control volume mixing region discretization to solicit transient effects in a new way. Division of the ejector into an inlet, diffuser, and mixing region corresponds with the assumption of viscous-dominated phenomenon in the latter. Inlet and diffuser analyses are simplified by a quasi-steady analysis, justified by the assumptions that pressure is the forcing function in those regions. Details of the theoretical foundation, the solution algorithm, and sample calculations are given. Drummond, Colin K. COMPUTATIONAL FLUID DYNAMICS; COMPUTERIZED SIMULATION; EJECTORS; FINITE VOLUME METHOD; MATHEMATICAL MODELS; THRUST AUGMENTATION; TURBULENT JETS; UNSTEADY FLOW; ALGORITHMS; INLET FLOW; PREDICTION ANALYSIS TECHNIQUES; REAL TIME OPERATION...

Proceedings

Proceedings
Author: R. P. Braden
Publisher:
Total Pages: 1094
Release: 1982
Genre: Short take-off and landing aircraft
ISBN:

An Experimental Study of Thrust Augmenting Ejectors

An Experimental Study of Thrust Augmenting Ejectors
Author:
Publisher:
Total Pages: 61
Release: 1983
Genre:
ISBN:

An automated thrust augmentation data acquisition facility was designed and constructed. The facility provides the capability of measuring thrust augmentation ratio and mass flow augmentation ratio. A three dimensional graphics plot of exit flow is provided for flow analysis. Tests were conducted on a 4.4 in. diameter circular ejector, with eight primary nozzles mounted symmetrically along the perimeter of the inlet. A fixed ejector geometry was used. The ratio of mixing chamber area to diffuser exit area was 1.88. The fluid injection angle, measured from a line perpendicular to the ejector centerline, was varied and the thrust augmentation and mass flow augmentation ratios calculated. Both thrust augmentation and mass flow augmentation increased with fluid injection angle to the stall point where both decreased. Axial flow symmetry of primary air was found to affect stall along diffuser walls.

Applicability of Thrust Augmenting Ejectors in a Supersonic Cruise Configuration

Applicability of Thrust Augmenting Ejectors in a Supersonic Cruise Configuration
Author: Wendell S. Hertzelle
Publisher:
Total Pages: 92
Release: 1997-04-01
Genre:
ISBN: 9781423568032

Thrust augmenting ejectors were analyzed by the author in an attempt to see if they could be used to provide a significant thrust increase over the baseline thrust of a primary core. This was done for the purpose of determining if leaving the ejectors open in the cruise configuration of the High Speed Civil Transport would lead to a thrust increase that would at least offset the weight of the ejectors themselves. If this was found to be true then the fuel economy of the HSCT might be improved by leaving them open and not closing them during cruise. In analyzing the ejectors, no assumptions were made regarding inlet nor outlet configurations, so an attempt was made to find the point of optimal thrust augmentation by varying secondary stream bypass Mach number and the amount of flow entrainment. Two solutions were found to each mixing scenario, one subsonic and the other supersonic. These two solutions were each analyzed and ones not satisfying the Second Law of Thermodynamics were eliminated. Analytic diffuser and bleed losses were also explored in the analysis of the ejector flow. Within the limitations of the assumptions discussed in this paper, appreciable thrust augmentations have been discovered over a large range of bypass Mach numbers and entrained mass flows. This lead the author to the conclusion that ejectors warrant further research beyond a first order analysis, and serious thought should be put into leaving them open in cruise.