Solid rocket motor pressure oscillations under lateral composite overloads

Solid rocket motors often experience complex overload conditions during flight, and sudden internal ballistic lift or oscillations occur occasionally. To study the pressure characteristics in the combustion chamber of solid rocket motors under dynamic overload conditions, the relationship curves between overload and mass flow rate of the propellant combustion surface are obtained using the Greatrix burning rate enhancement model and the zero-dimensional internal ballistic model considering the combustion surface recession. Based on the relationship, simulation of the internal flow field for a cylindrical cone bore charge is carried out under composite overload. The effects of lateral overload acceleration, lateral vibration and vibration frequency on the dynamic characteristics of the motor and vortex flow are investigated. The results show that with the increase of lateral overload acceleration and lateral vibration, the equilibrium pressure rises and pressure oscillation amplitude in the combustion chamber increases, and the lateral overload acceleration can increase the pressure amplitude and equilibrium pressure by 0.02% and 0.35%, respectively, with per 1g increase in acceleration at the working pressure of 10.54 MPa. As the lateral vibration frequency rises from 7 to 320 Hz, the amplitude of pressure oscillation decreases. But it is amplified by resonance near the intrinsic frequency of the combustion chamber acoustic cavity, and the first-order resonance（160 Hz）raises the amplitude of the pressure from 0.16% to 0.30%, which is twice the original amplitude. When the composite overload frequency resonates with the combustion chamber acoustic cavity, the energy transfer from the propellant surface into the combustion chamber is more orderly.