Aeroacoustic instability in rockets

Abstract

Current solid-propellant rocket instability calculations (e.g., Standard Stability Prediction Program) account only for the evolution of acoustic energy with time. However, the acoustic component represents only part of the total unsteady system energy; additional kinetic energy resides in the shear waves that naturally accompany the acoustic oscillations. Because most solid-rocket motor combustion chamber con gurations support gas oscillations parallel to the propellant grain, an acoustic representation of the ow does not satisfy physically correct boundary conditions. It is necessary to incorporate corrections to the acoustic wave structure arising from generation of vorticity at the chamber boundaries. Modi cations of the classical acoustic stability analysis have been proposed that partially correct this defect by incorporating energy source/sink terms arising from rotational ow effects. One of these is Culick's ow-turning stability integral; related terms that are not found in the acoustic stability algorithm appear. A more complete representation of the linearized motor aeroacoustics is utilized to determine the growth or decay of the system energy with rotational ow effects accounted for already. Signi cant changes in the motor energy gain/loss balance result; these help to explain experimental ndings that are not accounted for in the present acoustic stability assessment methodology.

Moderate‐to‐large injection and suction driven channel flows with expanding or contracting walls

“…For example, in modelling the gas dynamics produced by solid propellant combustion, previous studies have ignored both viscosity and propellant regression by relying on Taylor's inviscid profile. Recent studies by Apte and Yang [32], Lee and Beddini [33,34], Flandro and Majdalani [35], and others have indicated the importance of retaining viscous corrections due to their appreciable contribution to the damping of vorticity waves. Thus, not only does viscosity alter the mean flow character, but it also affects the assessment of motor stability that is strongly influenced by vortical energy.…”

Assessment of Slag Accumulation in Solid Rocket Boosters: Part II, Two-Phase Flow Experiments

“…These instabilities occurring in the motor during the launch have been investigated (using analytical, experimental and numerical tools) by several researchers, both in the USA [5][6][7][8][9] and in Europe, 4,[10][11][12][13][14][15][16][17] within the frameworks of the ASSM (Aerodynamics of Segmented Solid Motors) and POP (Pressure Oscillation Program for the Ariane 5 solid booster, MPS P230) programs (an overview of these studies can be found in Fabignon et al 10 ) of CNES (Centre National d'Etudes Spatiales). Two-dimensional (axisymmetric and planar) numerical simulations were carried out to investigate the periodic vortex shedding and its effect on acoustic instabilities in a SRM.…”

Flame response of solid propellant AP/Al/HTPB to a longitudinal acoustic wave

“…It is characterized by oscillation in the gasification rate of the solid phase. 16 The transient response of premixed flames to acoustic waves has been numerically addressed by Chu et al 17 and Cai et al 18 after they developed a comprehensive theoretical/numerical model for treating AP/HTPB composite propellant combustion in a rocket motor environment. 19 In contrast, the interaction between thermo-acoustic oscillations and liquid fuel sprays has been the subject of many theoretical and experimental studies.…”

“…In the last decade, there have been several studies into the interaction between the oscillations of the gas and the combustion zone in a SRM that have resulted in combustion oscillations, usually referred to as a “combustion response.” It is characterized by oscillation in the gasification rate of the solid phase. 16 The transient response of premixed flames to acoustic waves has been numerically addressed by Chu et al. 17 and Cai et al.…”