STUDY OF THE FLOW TURNING LOSS IN A SIMULATED SOLID ROCKET MOTOR

The flow turning loss, one of the processes that damp instabilities in solid rockets, is caused by the interaction of the axial acoustic fie ld in an unstable motor with the flow of combustion products from the propellant surface. While state-of-the-art stability models generally account for the flow turning loss, its characteristics have never been fully investigated. In order to study the contribution of the flow tu rning loss to acoustic stability, a one-dimensional acoustic stability equation that includes the flow turning loss term was derived, provid ing the theoretical background and expressions needed to guide an expe rimental study. Experiments were performed to determine the dependence of the flow turning loss up the injection and mean-flow Mach numbers and the location of the flow turning region relative to the standing a coustic wave. These studies showed that the flow turning loss strongly depends upon the magnitude of the gas velocity at the propellant surf ace and the location of the flow turning region relative to the standi ng pressure wave. A simple numerical simulation of the experimental se tup was developed and its predictions were found to agree well with th e measured data.