Relation between injection conditions and flowfield in scramjet combusters

Abstract

The pre-ignition phase flow-field in a supersonic combustor with perpendicular injectors behind a backward-facing step was simulated with cold airflow and inert gas injection. The effects of injector configuration on pressure and injectant concentration in the recirculation region between the step and the injectors were investigated. The diameter and spacing of injectors were changed, while distance between the step and the injectors was fixed. The pressure in the recirculation region was found to be almost uniform and its values with different configurations were well correlated with the momentum ratio of the injectant to the mainstream. This ratio took the dynamic pressure ratio, the diameter, and the spacing into account. However, the injectant concentration in the recirculation region was not as uniform as the pressure, and did not show a correlation with the momentum ratio. Nomenclature d = injector orifice diameter h = height of backward-facing step, 6 mm p static pressure pb = step-base pressure Pc = mainstream pressure at stagnant condition ps mainstream static pressure upstream of step Rm = momentum ratio of the injectant to mainstream Rq = dynamic pressure ratio of the injectant to mainstream 5 = injector spacing T= temperature 7= injectant volume concentration x = streamwise distance from step y = spanwise distance from combustor centerline 9 = momentum thickness of boundary layer Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. All right reserved. * Graduate Student, Department of Aeronautics and Space Engineering. t Professor, Department of Aeronautics and Space Engineering, Member AIAA. ± Researcher, Ramjet Combustion Laboratory, Ramjet Propulsion Research Division, Member AIAA. § Senior Researcher, Ramjet Combustion Laboratory, Ramjet Propulsion Research Division. Subscripts R recovery w = wall