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At least 127 records · Page 7

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DOE OSTI2023

Searching for eco-friendly working fluids for an ejector-driven heat pump for domestic water heating

This study searches for refrigerants with low global warming potential (GWP) and zero ozone depletion potential (ODP) for an ejector heat pump water heater (EHPWH). Several criteria are set, and R1336mzz(Z), R601a, R1233zd(E), R1224yd(Z), R1234ze(Z), and R600a are shortlisted. A theoretical model is built to study the performance of EHPWH and the corresponding ejector design at different operating conditions. For the same ejector design, a refrigerant with a high specific heat ratio produces a high entrainment ratio and heating COP. This is because the expansion wave angle in the ejector is small for refrigerants with a high specific heat ratio, allowing more mass flow rate to be entrained. A higher entrainment ratio does not necessarily correlate to a high COP because the saturation curve of the tested refrigerants is not the same. Results show that the heating COP of R601a is the highest, but it is extremely flammable. R1224yd(Z) and R1234ze(Z) are the most candidates for EHPWH when the trade-off between the COP and safety criteria is considered. The results presented in this work could help building an EHPWH using eco-friendly refrigerants.

Mohammed, Ramy H.↗

NASA NTRS2015

Parametric Study of Pulse-Combustor-Driven Ejectors at High-Pressure

Pulse-combustor configurations developed in recent studies have demonstrated performance levels at high-pressure operating conditions comparable to those observed at atmospheric conditions. However, problems related to the way fuel was being distributed within the pulse combustor were still limiting performance. In the first part of this study, new configurations are investigated computationally aimed at improving the fuel distribution and performance of the pulse-combustor. Subsequent sections investigate the performance of various pulse-combustor driven ejector configurations operating at highpressure conditions, focusing on the effects of fuel equivalence ratio and ejector throat area. The goal is to design pulse-combustor-ejector configurations that maximize pressure gain while achieving a thermal environment acceptable to a turbine, and at the same time maintain acceptable levels of NOx emissions and flow non-uniformities. The computations presented here have demonstrated pressure gains of up to 2.8%.

pulsejet↗

NASA NTRS2018

Computational Study of Compact Ejector-Enhanced Resonant Pulse Combustors

Previous studies of Ejector-Enhanced Resonant Pulse Combustors considered configurations that were relatively long, making them difficult to incorporate in practical gas turbine engines. In the present study, more compact configurations are analyzed, focusing on the system pressure gain. The study shows that it is possible to reduce the length of both the pulse combustor and ejector components without compromising the device's performance. In fact, it is found that in several of the compact configurations analyzed, the system pressure gain actually increased, reaching pressure gain levels above 5%, significantly higher than those obtained in previous studies. The Rayleigh efficiency, which has been used in the past to characterize the performance of pulse combustors, is computed for several of the Ejector-Enhanced Resonant Pulse Combustor configurations. The Rayleigh efficiency is seen to correlate with both average combustor pressure and system pressure gain for a given configuration, however, it could not be used to compare different configurations.

Compact↗

NASA NTRS1972

Factors which influence the analysis and design of ejector nozzles

A theoretical analysis of the viscous interaction between the primary and secondary streams of ejector nozzles was developed. The analysis accounts for real sonic line effects and the streamwise variation in stream mixing and boundary layer within the ejector. The aspects of the analysis are explained and illustrated by applying the theory to a variety of ejector configurations including cylindrical shroud, contoured flap and plug nozzles. Extensive comparisons are made between theory and data to show the importance of various analytical assumptions and such design variables as diameter ratio, spacing ratio, total temperature ratio, and primary nozzle geometry.

Anderson, B. H.↗

NASA NTRS1972

Flight investigation of an underwing nacelle installation of three variable-flap ejector nozzles

A modified F-106B aircraft with underwing engine nacelles was flight tested to investigate airframe installation effects on ejector nozzles. Nozzle thrust coefficients, boattail drag coefficients, and boundary layer characteristics were obtained for the three nozzles. All the nozzles were geometrically similar and had 15 deg conical boattails with juncture radii of curvature equal to 0.5 maximum nozzle diameter. The effects of boattail location relative to the wing trailing edge and the ejector to primary nozzle exit diameter ratio were investigated. Shortening the length by 0.48 nozzle diameter lowered the transonic boattail drag rise Mach number from 0.97 to 0.95. Decreasing the nozzle exit diameter, which reduced the ejector to primary nozzle exit diameter ratio from 1.30 to 1.18, increased the gross thrust coefficient 4.8 percent.

Head, V. L.↗

NASA NTRS1972

Factors which influence the analysis and design of ejector nozzles.

A theoretical analysis of the viscous interaction between the primary and secondary streams of ejector nozzles was developed. The analysis accounts for real sonic-line effects and the streamwise variation in stream mixing and boundary layer within the ejector. The aspects of the analysis are explained and illustrated by applying the theory to a variety of ejector configurations including cylindrical shroud, contoured flap and plug nozzles. Extensive comparisons are made between theory and data to show the importance of various analytical assumptions and such design variables as diameter ratio, spacing ratio, total temperature ratio, and primary nozzle geometry.

Anderson, B. H.↗

NASA NTRS1969

Thrust and pumping characteristics of cylindrical ejectors using afterburning turbojet gas generator

Static tests of cylindrical ejectors having ejector to primary diameter ratios from 1.1 to 1.6 and ejector length to primary nozzle diameter ratios from 0.9 to 2.1 are reported. Power setting of the J85-13 turbojet engine was varied from part power to maximum afterburning. Corrected secondary weight flow ratio was varied from 0.02 to 0.08 over a range of exhaust nozzle pressure ratios from 2.0 to 9.0. Secondary flow temperature rise and pressure drop characteristics through the nacelle secondary flow passage were also obtained.

Samanich, N. E.↗

NASA NTRS1974

Assessment of an analytical procedure for predicting supersonic ejector nozzle performance

The ability of analysis to predict ejector nozzle characteristics over a wide range of conditions and to study the relation between design parameters and performance is assessed. The analytical method investigated provided an accurate and economical method for predicting the performance of supersonic ejector nozzles. The factors which had the greatest influence over ejector nozzle behavior were those which influenced the initial expansion and recompression process.

Anderson, B. H.↗

NASA NTRS1974

Ejector-powered lift systems for V/STOL aircraft

The paper takes a brief look at powered lift from the point of view of the operator and the designer, considers application of an ejector-powered lift system to both STOL and VTOL aircraft, and describes some of the advantages of an ejector concept. Performance and noise characteristics of a simple ejector are described, and some comments are made regarding the Buffalo/Spey Augmentor-Wing proof-of-concept aircraft.

Whittley, D. C.↗

NASA NTRS1978

A three-dimensional turbulent compressible flow model for ejector and fluted mixers

A three dimensional finite element computer code was developed to analyze ejector and axisymmetric fluted mixer systems whose flow fields are not significantly influenced by streamwise diffusion effects. A two equation turbulence model was used to make comparisons between theory and data for various flow fields which are components of the ejector system, i.e., (1) turbulent boundary layer in a duct; (2) rectangular nozzle (free jet); (3) axisymmetric nozzle (free jet); (4) hypermixing nozzle (free jet); and (5) plane wall jet. Likewise, comparisons of the code with analytical results and/or other numerical solutions were made for components of the axisymmetric fluted mixer system. These included: (1) developing pipe flow; (2) developing flow in an annular pipe; (3) developing flow in an axisymmetric pipe with conical center body and no fluting and (4) developing fluted pipe flow. Finally, two demonstration cases are presented which show the code's ability to analyze both the ejector and axisymmetric fluted mixers.

Rushmore, W. L.↗

NASA NTRS1979

An overview of current Navy programs to develop thrust augmenting ejectors

The primary objective of Navy sponsored research in thrust augmentation is the development of an improved augmenter for V/STOL application. In support of this goal, a data base is being established to provide an accurate prediction capability for use in ejector design. A general technology development of ejectors and associated effects presently is split into the more specific areas of lift and control, since thrust augmenting ejectors may be suitable for both. Research areas examined include advanced diffuser and end wall design; advanced primary nozzles; analytic studies; augmenting reaction controls; and nozzle design.

Green, K. A.↗

NASA NTRS1979

Some tests on small-scale rectangular throat ejector

A small scale rectangular throat ejector with plane slot nozzles and a fixed throat area was tested to determine the effects of diffuser sidewall length, diffuser area ratio, and sidewall nozzle position on thrust and mass augmentation. The thrust augmentation ratio varied from approximately 0.9 to 1.1. Although the ejector did not have good thrust augmentation performance, the effects of the parameters studied are believed to indicate probable trends in thrust augmenting ejectors.

Dean, W. N., Jr.↗

NASA NTRS1980

Recent development of a jet-diffuser ejector

The paper considers thrust augmenting ejectors in which the processes of mixing and diffusion are partly carried out downstream of the ejector solid surfaces. A jet sheet surrounding the periphery of a widely diverging diffuser prevents separation and forms a gaseous, curved surface to provide effective diffuser ratio and additional length for mixing of primary and induced flows. Three-dimensional potential flow methods achieved a large reduction in the length of the associated solid surface; primary nozzle design further reduced the volume required by the jet-diffuser ejectors, resulting in thrust augmentation in excess of two, and an overall length of about 2 1/2 times the throat width.

Alperin, M.↗

NASA NTRS1981

Study of an engine flow diverter system for a large scale ejector powered aircraft model

Requirements were established for a conceptual design study to analyze and design an engine flow diverter system and to include accommodations for an ejector system in an existing 3/4 scale fighter model equipped with YJ-79 engines. Model constraints were identified and cost-effective limited modification was proposed to accept the ejectors, ducting and flow diverter valves. Complete system performance was calculated and a versatile computer program capable of analyzing any ejector system was developed.

Springer, R. J.↗

NASA NTRS1987

A viscous-inviscid interaction method for ejectors having two primary jets

A viscous-inviscid interaction methodology is developed for evaluating the performance of two-dimensional incompressible flow ejectors that utilize two primary jets. In this method, the inviscid portion of the flow field, which contains the ambient fluid drawn into the device, is modeled using a higher-order panel method. The viscous region, which contains the turbulent jets, is described by an integral method. The viscous and inviscid solutions are matched together in an iterative process that simulates the interaction between the jets and the ambient fluid. The model is applied to a variety of parametric and optimization studies that illustrate the connection between the details of the ejector geometry and the level of thrust augmentation. The advantages of a dual-jet configuration are assessed through comparison with similar calculations for an otherwise identical single-jet ejector.

Lund, T. S.↗

NASA NTRS1990

Mixer-ejector nozzle for jet noise suppression

An aero/acoustic model test of a mixer-ejector nozzle was conducted at the 9 x 15 foot low-speed acoustic wind tunnel at NASA Lewis Research Center. The objective of the test was to get a preliminary assessment of ejector pumping and noise reduction potential of this device for possible application in the exhaust system of an advanced supersonic civil transport. The results of the test showed that goal levels of pumping were achieved. Exit pressure/temperature traverse data showed that there was good mixing between the primary and secondary streams. Acoustics data were dominated by shock noise; jet mixing noise levels were low because of a facility limit on primary temperature. The mixer-ejector did significantly reduce shock noise relative to the baseline conic nozzle. Because the relative magnitudes of jet mixing noise and shock noise were not in the correct proportion to properly model engine noise, an Effective Perceived Noise Level (EPNL) assessment was precluded.

Lord, W. K.↗

NASA NTRS1992

Use of an approximate similarity principle for the thermal scaling of a full-scale thrust augmenting ejector

Full temperature ejector model simulations are expensive, and difficult to implement experimentally. If an approximate similarity principle could be established, properly chosen performance parameters should be similar for both hot and cold flow tests if the initial Mach number and total pressures of the flow field are held constant. Existing ejector data is used to explore the utility of one particular similarity principle; the Munk and Prim similarity principle for isentropic flows. Static performance test data for a full-scale thrust augmenting ejector are analyzed for primary flow temperatures up to 1560 R. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow parameter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments.

Barankiewicz, Wendy S.↗

NASA NTRS1992

Use of an approximate similarity principle for the thermal scaling of a full-scale thrust augmenting ejector

Full temperature ejector model simulations are expensive, and difficult to implement experimentally. If an approximate similarity principle could be established, properly chosen performance parameters should be similar for both hot and cold flow tests if the initial Mach number and total pressures of the flow field are held constant. Existing ejector data is used to explore the utility of one particular similarity principle; the Munk and Prim similarity principle for isentropic flows. Static performance test data for a full-scale thrust augmenting ejector are analyzed for primary flow temperatures up to 1560 R. At different primary temperatures, exit pressure contours are compared for similarity. A nondimensional flow paramenter is then used to eliminate primary nozzle temperature dependence and verify similarity between the hot and cold flow experiments.

Barankiewicz, Wendy↗