THREE-DIMENSIONAL NUMERICAL SIMULATION OF THE FLOW FIELD IN HYBRID ROCKET MOTOR WITH WAGON-WHEEL FUEL GRAIN

摘要

This paper presents the three dimensional numerical simulations of hybrid rocket motor with wagon wheel grain and investigates the flow field distribution characteristics and motor performances. The numerical model is established based on the Navier-Stokes equations with turbulence, chemical combustions, fuel pyrolysis and solidgas boundary interactions. A two-step combustion model is selected for the gaseous phase combustions, and the solid-gas interface boundary formulation is developed based on the energy conservation equation. The flow fields and motor performances are then presented and discussed based on the 98% hydrogen peroxide (HP) and hydroxyl terminated polybutadiene (HTPB) propellant combination. The results show that the flow fields present apparent three dimensional characteristics. The flame layer forms in the interface of the oxidizer flow and the fuel pyrolysis products, and the profile of it is similar with the fuel port. With the axial location increasing, the fuel regression rate decreases sharply at first and then increases to a steady level. At a certain cross section, regression rates are higher in the points near the flame layer for larger temperature gradients and convective heat fluxes. The performances of the characteristics velocity and vacuum specific impulse, which may be mainly affected by the fuel configurations and structural features, are slightly affected by the oxidizer to fuel ratio working condition, and the efficiencies of the characteristic velocity and specific impulse reach minimum values near the optimal oxidizer to fuel ratio.