Modeling and analysis of triggering pulse to thermoacoustic instability in an end-burning-grain model solid rocket motor

Abstract

Occurrences of pulse-triggered instabilities in combustion chambers always trouble solid rocket motors (SRMs) in application. This paper performs numerical simulation of the pulse-triggered nonlinear instabilities in the end-burning-grain SRM, in use of the pressure-coupled response function to describe the spatiotemporal burning rate of AP-HTPB composite propellant grains. A high-order numerical solver realizes the cooperation of the burning rate model into the axisymmetric internal ballistic simulation of SRMs via the source terms in gas-phase governing equations. The analysis of high-amplitude pressure oscillations, which are the primary symptom of nonlinear thermoacoustic instabilities, provides the insight into the nature of the longitudinal instability growth process after the pulse triggering. The change rate of pressure fluctuation over the pressure fluctuation in the chamber is independent of the pulse intensity and triggering position. The growth characteristics of pressure oscillations for the present combustor system is neither affected by the pressure pulse intensity nor by the imposed regions in the flow field, while the higher pressure-coupled response function of the propellant promotes the growth process evidently. The present study is expected for the guidance of grain design in SRMs.