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.

An Experimental Investigation of Two-Dimensional Thrust Augmenting Ejectors

An Experimental Investigation of Two-Dimensional Thrust Augmenting Ejectors
Author: L. Bernal
Publisher:
Total Pages: 104
Release: 1984
Genre:
ISBN:

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.

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.

Experimental Investigation of Thrust Augmenting Ejector Flows

Experimental Investigation of Thrust Augmenting Ejector Flows
Author: L. Bernal
Publisher:
Total Pages: 19
Release: 1982
Genre:
ISBN:

The results of two investigations, one recently completed on pulsatile ejector flows and the second currently in progress on a two-dimensional ejector configuration are presented. The objective of these investigations is to determine the role of entrained fluid and its mixing with the primary jet on ejector performance. Results will also be presented on the effects of entrance geometry on ejector entrainment and thrust augmentation.

Proceedings

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

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.

Study of Three-Dimensional Thrust-Augmenting Ejectors

Study of Three-Dimensional Thrust-Augmenting Ejectors
Author: Ramesh K. Agarwal
Publisher:
Total Pages: 18
Release: 1982
Genre:
ISBN:

A theory is presented for the prediction of thrust augmentation characteristics of a three-dimensional ejector configuration in which a series of rectangular-hypermixing nozzles pumps the secondary air in a constant-area or slowly diverging channel. Based on the theory, a computer program is developed which requires the ejector design parameters, the empirical constants in the eddy viscosity model, and the nozzle pressure ratio as input and calculates the entrained secondary mass flow, the secondary and exit velocities, the net thrust and the thrust augmentation ratio. Good agreement is found between the theoretical prediction and the experimental data.