A 1.5-D model for the cylindrical combustion chamber of a hybrid rocket is developed in this article with the purpose of its integration in a design system tool allowing to estimate the rocket performances. A compromise of simplicity and accuracy is then required in the formulation of the model. Transient boundary layer equations are included through an integral approach and are coupled with the mass and energy balances performed at the fuel surface. Fuel pyrolysis is described by way of an Arrhenius law. Several studies to assess the impact of the geometry of the fuel port, the oxidizer mass flux, and the motor size on the computed fuel regression rate are accomplished. A final validation phase of this model is executed by the comparison with experimental tests realized at ONERA's HYCAT test bench with a Hydrogen Peroxide / High-Density Polyethylene couple.

A pseudo 2-D model for the cylindrical combustion chamber of a hybrid rocket is developed in this article 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 non-reactive 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 a 87.5% Hydrogen Peroxide/High-Density Polyethylene couple. Corresponding results lead to regression rate errors varying in a wide range (from 10