The influence of thermal inhibitor position on pressure oscillations in solid rocket motors: Numerical study

Vortex-acoustic coupling is one of the most important potential sources of combustion instability. Based on the VKI experimental motor, the influence of the inhibitor position on pressure oscillation characteristics is numerically studied via the LES method. The results demonstrated that vortex shedding is a periodic process and its accurate frequency can be numerically obtained. Acoustic modes would be easily excitated by vortex shedding. Meanwhile, the vortex shedding frequency and second acoustic frequency dominate the pressure oscillation characteristics in the chamber. Thermal inhibitor position has little effect on vortex shedding frequency, but has great impact on pressure oscillation amplitude. Pressure amplitude is much severe when the thermal inhibitor locates at the acoustic velocity antinodes. The further the thermal inhibitor to nozzle head, the more the vortex energy will be dissipated by the turbulence. Therefore, the vortex shedding amplitude at the second acoustic velocity anti-node near 3/4L is larger than that of others.