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Journal ArticleDOI

Supersonic flow in the second-throat ejector-diffuser system

01 Jan 1994-Journal of Spacecraft and Rockets (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 31, Iss: 1, pp 123-129
TL;DR: In this paper, a second-order high-resolution scheme for solving the new Lagrangian Euler equations is employed to accurately resolve the complicated shock patterns and associated slip lines and their interactions.
Abstract: A computational analysis of the two-dimensional supersonic inviscid flowfield in a second-throat ejector-diffuser (STED) system is presented. A second-order high-resolution scheme for solving the new Lagrangian Euler equations is employed to accurately resolve the complicated shock patterns and associated slip lines and their interactions. A parametric study covering a variety of Xst and Ost is implemented to investigate their effects on the flow structure in STED as well as its performance. Results suggest that the averaged Mach number along the entrance plane of the second throat is a suitable criterion for the justification of the performance of STED. With this criterion, an optimal design insuring the largest pressure recovery can be achieved.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the performance of six well-known turbulence models for the study of supersonic ejectors was evaluated and the results showed that the k-omega-sst model agrees best with experiments.

323 citations

Journal ArticleDOI
TL;DR: In this article, numerical results of a supersonic ejector for refrigeration applications are presented, which is based on the NIST-this articlePROP database for refrigerants properties calculations.

163 citations

Journal ArticleDOI
01 Jun 2010-Energy
TL;DR: In this paper, the authors conducted a computational fluid dynamics (CFD) investigation into the flow structure inside a steam ejector and found that the ejector with a converging duct angle of 1° has the best performance.

83 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach, where the fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed.
Abstract: Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated. The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed. The CFD code is constructed using the open-source OpenFOAM library. Using carbon dioxide as the working fluid, the results of the simulations show a pressure rise that is comparable to experimental data. It is also observed that the flow is near thermodynamic equilibrium in the diffuser, suggesting that turbulence effects present the greatest challenge in modeling these ejectors.

81 citations


Cites background from "Supersonic flow in the second-throa..."

  • ...Other authors in the past have used k-epsilon models in their work, but there was no justification to the use of a particular model and no experimental validations [33] [34] [35]....

    [...]

Journal ArticleDOI
06 Mar 2019
TL;DR: A review of the main developments in ejectors over the last few years can be found in this article, where the main findings and trends in the area of heat-driven ejectors and ejector-based machines using low boiling point working fluids are summarized.
Abstract: Ejectors used in refrigeration systems as entrainment and compression components or expanders, alone or in combination with other equipment devices, have gained renewed interest from the scientific community as a means of low temperature heat recovery and more efficient energy use. This paper summarizes the main findings and trends, in the area of heat-driven ejectors and ejector-based machines, using low boiling point working fluids, which were reported in the literature for a number of promising applications. An overall view of such systems is provided by discussing the ejector physics principles, as well as a review of the main developments in ejectors over the last few years. Recent achievements on thermally activated ejectors for single-phase compressible fluids are the main focus in this part of the review. Aspects related to their design, operation, theoretical and experimental approaches employed, analysis of the complex interacting phenomena taking place within the device, and performance are highlighted. Conventional and improved ejector refrigeration cycles are discussed. Some cycles of interest employing ejectors alone or boosted combinations are presented and their potential applications are indicated.

70 citations

References
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Ami Harten1
24 Aug 2011
TL;DR: In this article, a class of new explicit second order accurate finite difference schemes for the computation of weak solutions of hyperbolic conservation laws is presented, which are obtained by applying a nonoscillatory first order accurate scheme to an appropriately modified flux function.
Abstract: A class of new explicit second order accurate finite difference schemes for the computation of weak solutions of hyperbolic conservation laws is presented. These highly nonlinear schemes are obtained by applying a nonoscillatory first order accurate scheme to an appropriately modified flux function. The so-derived second order accurate schemes achieve high resolution while preserving the robustness of the original nonoscillatory first order accurate scheme. Numerical experiments are presented to demonstrate the performance of these new schemes.

3,095 citations

Journal ArticleDOI
TL;DR: A uniformly second-order approximation of hyperbolic conservation laws is constructed, which is nonoscillatory in the sense that the number of extrema of the discrete solution is not increasing in time.
Abstract: We begin the construction and the analysis of nonoscillatory shock capturing methods for the approximation of hyperbolic conservation laws. These schemes share many desirable properties with total variation diminishing schemes, but TVD schemes have at most first-order accuracy, in the sense of truncation error, at extrema of the solution. In this paper we construct a uniformly second-order approximation, which is nonoscillatory in the sense that the number of extrema of the discrete solution is not increasing in time. This is achieved via a nonoscillatory piecewise-linear reconstruction of the solution from its cell averages, time evolution through an approximate solution of the resulting initial value problem and an average of this approximate solution over each cell.

1,031 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented an analysis of the performance of ejector configurations under the first solution where the flow after mixing is subsonic and the second solution for mixing is supersonic, respectively, and provided a basis for selecting an optimal and a limiting ejector configuration for any given set of flight and injected gas characteristics.
Abstract: The solution of the equations representing the flow of a compressible fluid through an ejector has been shown to possess two distinctly different results after complete mixing. Part I of this study reported the analysis and described the performance of ejectors configured under the first solution where the flow after mixing is subsonic. The second solution to the ejector flow equations where the flow after mixing is supersonic provides a basis for selection of an optimal and a limiting ejector configuration for any given set of flight and injected gas characteristics. These special ejector configurations provide very high ideal thrust augmentations while translating from zero to supersonic velocities. Maps showing this ideal performance over large ranges of flight and injected gas characteristics are presented. Consideration is given to the influence of realistic, nonisentropic outlets as required for starting the supersonic flow (swallowing the starting shock wave) and for return of the supersonic mixed flow to ambient pressure. The data presented are limited to ejectors having a constant area mixing duct whose cross section is equal to 25 times that of the minimal area of the exhaust flow from the gas generator.

85 citations

Journal ArticleDOI
TL;DR: In this article, a discussion of the development of the compact jet-diffuser ejectors utilized for hovering and low speed flight propulsion has been presented, 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.
Abstract: : 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

52 citations

Journal ArticleDOI
TL;DR: In this article, a shock capturing method is developed by applying the first-order Godunov scheme to the conservation form equations of the Lagrangian formulation, which is fast and robust.

51 citations