Influence of Flight Conditions on the Combustion Characteristics of Solid-Fuel Ramjet

The dynamic mixing and combustion characteristics of an Al-Mg-hydroxyl-terminated-polybutadiene-based solid-fuel ramjet (SFRJ) system were investigated via a newly developed pyrolysis and combustion model. Fire tests were conducted to validate the developed model, with thrust errors within 3%, and deviations in regression rate and specific impulse within 1%. The results showed that the model developed in the present work can accurately predict the regression rate and thrust of an SFRJ system. On the basis of this model, simulations of the combustion process were performed under wide-range flight conditions (the total pressure range from 0.5 to 1.5 MPa and the total temperature range from 500 to 900 K). The results showed that the flame surface has an initial near-wall point in both the cavity region and the flat-plate region. Owing to the influence of nonuniform regression, the combustion stage transitions, accompanied by substantial variations in the oxygen–fuel ratio and thrust loss. In the first stage, the total pressure and temperature of the inflow can accelerate the transition process and lead to more obvious variations in the regression rate and thrust loss. Compared with the total pressure, the total temperature has a smaller effect. In the second stage, the average regression rate and thrust are positively correlated with the total pressure. There is a tendency of initial increase followed by a decrease in the variation in the total temperature, with a peak value at 700 K.