REGRESSION RATE AND HEAT TRANSFER CORRELATIONS FOR HTPB/GOX COMBUSTION IN A HYBRID ROCKET MOTOR

A data analysis program was developed to correlate the experimental solid-fuel regression-rate and thermal-pyrolysis data obtained in a lab-scale hybrid motor, a thermal-pyroly sis test apparatus, and a GC/MS system. The code employs an interfacial energy flux balance, various methods to determine the component heat fluxes due to radiation and convection, transient mass and energy conservation equations for the local gas properties, and chemical equilibrium computations for the flame properties. Separate dimensionless correlations were developed to accurately predict the regression rates in the upstream developing-flow region of the motor and the downstream developed-flow region. Radiation, variable fluid properties across the boundary layer, and axial variations in the gas temperature and velocity gradients had significant effects on the regression rate behavior in both regions. The radiant heat flux from soot contributed significantly to the overall surface heat flux under relatively low mass flux and low O/F ratio conditions. Correlations were also developed for the deduced Stanton and Nusselt numbers. The regression rate correlations predicted independent data from a tube burner to within ±5% error.