Theoretical, numerical, and experimental investigation of paraffin-HTPB blended fuels for hybrid rocket applications

This paper presents a comprehensive theoretical, experimental, and numerical investigation of hybrid rocket propellants based on paraffin, hydroxyl-terminated polybutadiene (HTPB), and HTPB–paraffin blends of varying compositions, using gaseous oxygen as the oxidizer. Theoretical performance analyses were conducted with NASA’s CEA code to predict specific impulse, thrust coefficient, and combustion chamber temperature across a range of chamber pressures and fuel formulations. Laboratory-scale experiments were performed on the SIA ASPL hybrid propulsion test bench to evaluate the performance of these propellants and to assess the accuracy of the theoretical predictions. Numerical simulations were carried out using axisymmetric Reynolds-averaged Navier-Stokes (RANS) to interpret the experimental results and to examine the underlying combustion mechanisms in hybrid rocket systems. These simulations were further used to validate the reaction mechanisms and enhance modeling f idelity. Overall, the combined approach demonstrates the utility of experiments and numerical modeling in predicting hybrid rocket performance and supporting improved propellant and motor design.