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Non-axisymmetric ejector-based combined cycle propulsion systems have received renewed attention due to their potential applicability to next generation space transportation. However, fundamental fluid mechanical mechanisms in even a simple asymmetric ejector system are not well understood. The University of Alabama in Huntsville Propulsion Research Center has an ongoing research program to investigate the induced flow and mixing in rocket driven, non-axisymmetric ejectors. The facility consists of a high-pressure air feed system connected to supersonic nozzles embedded in struts. The struts are installed in a rectangular cross section duct with a contoured inlet. The chamber pressure inside the strut nozzle is varied, and the flow behavior in the duct is examined. This paper summarizes the UAH PRC cold flow ejector research. The paper presents significant results from recent tests on a single nozzle strut. The data from this research provides valuable insight into flow behavior in a non-axisymmetric ejector system. The data will also be valuable for computational fluid dynamic simulations of complex ejector systems. Nomenclature UAH University of Alabama in Huntsville PRC Propulsion Research Center CCP Combined Cycle Propulsion M Mach Number m& Mass Flow P Static Pressure Po Stagnation Pressure T Temperature To Stagnation Temperature A Area γ Ratio of Specific Heats R Specific gas constant ω Suction Ratio Subscripts s secondary flow p primary flow Introduction Combined Cycle Propulsion (CCP) technology shows promise for next generation launch vehicles. Since a combined cycle engine incorporates several modes of engine operation into the same flow path, the optimum performance mode can be utilized in each flight regime. A typical Rocket Based Combined Cycle (RBCC) engine would operate in a rocket or ducted rocket mode for takeoff and initial acceleration to about Mach 2-3, transition to ramjet mode until Mach 4-6, and then transition to scramjet operation. Above Mach 6-8, scramjet operation is unrealistic, and the engine would operate as a pure rocket to accelerate into orbit. The Strutjet is one of the RBCC systems under consideration. This engine consists of a variable geometry duct with vertical engine struts mounted internally. Each strut has several rocket nozzles embedded within it. The engine operates in the four modes discussed earlier: ducted rocket, ramjet, scramjet, and pure rocket. In the airbreathing modes, atmospheric air is ingested into the inlet and flows between the struts into the mixing section. The air oxidizer is mixed with the fuel rich rocket exhaust and combusted. The combustion products are accelerated through an exit nozzle to provide the thrust. Graduate Research Assistant. Student Member AIAA. Graduate Research Assistant, Currently Graduate Student at the University of Maryland. Student Member AIAA. Associate Professor, Mechanical and Aerospace Engineering Dept. Senior Member AIAA Director and Professor of Mechanical and Aerospace Engineering. Fellow AIAA. Copyright 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. A fundamental understanding of ejector physics is an enabling technology to realize an operational RBCC propulsion system. Past theoretical and experimental ejector studies have considered one-dimensional, axisymmetric, or at best two-dimensional geometries. Concepts such as the Strutjet use a complex asymmetric, three-dimensional flow path. The University of Alabama in Huntsville (UAH) Propulsion Research Center (PRC) has an ongoing research program to characterize asymmetric ejector performance in terms of mass flow entrainment and American Institute of Aeronautics and Astronautics 1 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama AIAA 2003-5231 Copyright © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. |
