An overview of ejector theory

Porter, J. R.; Squyers, R A; Nagaraja, K. S.

doi:10.2514/6.1981-1678

Cited by 15 publications

(8 citation statements)

References 4 publications

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“…Several studies, both experimental and theoretical, have been carried out during the past two decades on thrust augmenting ejectors. A review of these works can be found in recent papers by Quinn 4 and Porter et al 5 Most previous studies indicate that the overall performance of the ejector with a fixed geometry depends mainly on the degree of mixing attained between the primary and secondary streams. With this in mind, attempts have been made by several investigators to improve the mixing through various types of nozzle designs, for example, the hyper mixing nozzle.…”

Section: Introductionmentioning

confidence: 98%

Mixing of an underexpanded rectangular jet ejector

Hsia

Krothapalli

Baganoff

1988

Journal of Propulsion and Power

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An experimental investigation was carried out on a rectangular ejector (constant area mixing duct) with an underexpanded rectangular jet as the primary flow. From the wall static pressure measurements, the ejector performance was found to show irregular variations with the primary jet pressure. Hot-wire measurements, together with schlieren photographs, showed that better performance was obtained when the flow was well mixed. The well-mixed flow was found when the screech tone Strouhal number was in the 0.11-0.14 range, which agrees with the most unstable Strouhal number of the free underexpanded rectangular jet. By incorporating a phase-locked technique with shlieren flow visualization, we were able to photograph standing waves excited by the screech tones inside the ejector mixing duct. The interactions between the jet flow and the screech tones were studied using this flow visualization technique. Nomenclature= cross-sectional area of primary nozzle = cross-sectional area of mixing duct = (p-P a )/Pa> pressure coefficient = C p at the entrance of the mixing duct = average of six C^ measured = 5.0 mm, nozzle width (short dimension) = discrete tone frequency = 70.0 mm, height of mixing duct = 50.0 mm, nozzle length (long dimension) = surface static pressure = jet total pressure = ambient pressure =Po / Pa> J et pressure ratio =f*D/U e , Strouhal number = mean velocity = jet exit velocity = mixing duct width = Cartesian coordinates

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Section: Introductionmentioning

confidence: 98%

Mixing of an underexpanded rectangular jet ejector

Hsia

Krothapalli

Baganoff

1988

Journal of Propulsion and Power

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“…12 American Institute of Aeronautics and Astronautics Approved for public release; distribution is unlimited The ideal gas nozzle [7] subroutine is a simple routine that uses the following equations: It is worth noting that other effects which could be as large as real gas effects, such as viscous boundary layer effects, were not included. These could be improvements worth adding to the model in the future.…”

Section: Figure 8 Nozzle Station Nomenclaturementioning

confidence: 99%

A General Simulation of an Air Ejector Diffuser System

Daniel

2012

28th Aerodynamic Measurement Technology, Ground Testing, and Flight Testing Conference

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A computer model of a blow-down free-jet hypersonic propulsion test facility exists to validate facility control systems as well as predict problems with facility operation. One weakness in this computer model is the modeling of an air ejector diffuser system. Two examples of facilities that could use this ejector diffuser model are NASA Langley Research Center's 8-ft High Temp. Tunnel (HTT) and the Aero-Propulsion Test Unit (APTU) located at Arnold Engineering Development Center. Modeling an air ejector diffuser system for a hypersonic propulsion test facility includes modeling three coupled systems. These are the ejector system, the primary free-jet nozzle that entrains secondary airflow from the test cell, and the test article. Both of these facilities are capable of testing scramjets/ramjets at high Mach numbers. Compared with computer simulation data, experimental test cell pressure data do not agree due to the current modeling technique used. An improved computer model was derived that incorporates new techniques for modeling the ejector diffuser. This includes real gas effects at the ejector nozzles, flow constriction due to free-jet nozzle and ejector plumes, test article effects, and a correction factor of the normal shock pressure ratio in a supersonic diffuser. A method was developed to account for the drag and thrust terms of the test article by assuming a blockage factor and using a drag coefficient*Area term for both the test article and thrust stand derived from experimental data. An ideal ramjet model was also incorporated to account for the gross thrust of the test article on the system. The new ejector diffuser model developed improved the accuracy and fidelity of the facility model as compared with experimental test data while only negligibly affecting computational speed. Comparisons of the model data with experimental test data showed a close match for test cell pressure (within 1 percent for final test cell pressure). The model accurately simulated both the unstarted and started modes of ejector flow, in which test cell pressure increases with nozzle total pressure once in started mode.

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“…In particular, one-dimensional analysis has been conducted in order to improve rocket engine thrust as well as to predict the pressure-recovery ratio. [10][11][12][13] In these research papers, the pressure-recovery ratio is evaluated as a function of the mass-flow ratio or the total pressure ratio between the primary and secondary flows. Dutton et al 12) conducted parametric studies on the pressure-recovery ratio using an ejector system with a constant-area mixing section, attempting to correlate the obtained results with the mass-flow ratio.…”

Section: Introductionmentioning

confidence: 99%

Supersonic Ejector-Driving System under Low Pressure: A Performance Evaluation

Anyoji

Numata

Nagai

et al. 2021

Trans. Japan Soc. Aero. S Sci.

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We have developed a low-density wind tunnel that simulates Martian atmospheric flight on the ground. This wind tunnel employs a supersonic ejector-drive system to realize high-speed flow under low-density conditions. This study presents a general evaluation method for the ejector driver of the wind tunnel under low-pressure conditions. As an evaluation parameter for the pressure-recovery ratio, which is a representative value of the driving performance, the ejectordrive parameter (EDP) determined from the design and operating conditions is applied, verifying its effectiveness under atmospheric conditions. Accordingly, we investigate the effectiveness of the EDP at low pressures and its scalability to complex multiple supersonic nozzles. Our results suggest that the pressure-recovery ratio is correlated with the EDP even when the ambient pressure, system configuration, and operational conditions change. The EDP allows us to predict the Mach number, and can provide us with an appropriate framework for ejector design optimization.

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An overview of ejector theory

Cited by 15 publications

References 4 publications

Mixing of an underexpanded rectangular jet ejector

Mixing of an underexpanded rectangular jet ejector

A General Simulation of an Air Ejector Diffuser System

Supersonic Ejector-Driving System under Low Pressure: A Performance Evaluation

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