Pseudo-Two-Dimensional Modeling and Validation of a Hybrid Rocket Combustion Chamber

A pseudo-two-dimensional (pseudo-2-D) model for the cylindrical combustion chamber of a hybrid rocket is developed in this paper with the purpose of its integration in a system design tool used for engine predesign phases. A compromise of simplicity and accuracy is thus required. Integral transient boundary-layer equations are included and coupled with the mass and energy balances at the fuel surface, where fuel pyrolysis is described by an Arrhenius law. Studies assessing the model in the nonreactive case provide satisfactory results regarding the description of the boundary layer. Concerning the hybrid case, the computed steady-state fuel regression rates are found to be in the low region of the reference values coming from semiempirical laws for several oxidizer/fuel couples and oxidizer mass fluxes, producing errors up to 50% for certain sources. The effect of mass flux and motor size is correctly simulated. Eventually, the whole engine operation is assessed through the comparison of the computed results with three experimental tests realized at our laboratory and using an 87.5% hydrogen-peroxide/high-density-polyethylene couple. Corresponding results lead to regression rate errors varying in a wide range (from 10 to 40%). Such differences, although high, remain acceptable for our engine predesign phase application.