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...

Experimental Investigation of a Thrust Augmenting Ejector

Experimental Investigation of a Thrust Augmenting Ejector
Author: Hidayat Wiradimadja
Publisher:
Total Pages: 0
Release: 1985
Genre:
ISBN:

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.

Thrust Augmentation Study of High Performance Ejectors

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.

Entrainment and Mixing in Thrust Augmenting Ejectors

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.

Steady Flow Ejector Research Program

Steady Flow Ejector Research Program
Author: Lockheed-Georgia Company
Publisher:
Total Pages: 230
Release: 1961
Genre: Ejector pumps
ISBN:

An investigation was conducted to determine the jet thrust augmentation under static conditions for rectangular parallel-divergent wall ejector configurations with multiple primary nozzles. The effect of various geometrical and flow parameters were investigated in order to provide design information. Parameters investigated included the ratio of the ejector exit area to the primary nozzle area, the diffuser angle, the mixing section length, the primary nozzle position, the entrance radius, the number of primary nozzle rows, and the primary nozzle pressure ratio and temperature ratio. The test results are generalized to obtain curves relating the augmentation factor to ejector geometry and flow parameters over a wide range of ejector exit to primary nozzle area ratios. (Author).

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.