Numerical analysis of nozzle heating and erosion in hybrid rockets and comparison with experiments

The motor performance loss due to nozzle throat erosion in hybrid rocket engines is an important feature to be considered during the motor design. In fact, a peculiar characteristic of hybrid rockets operating conditions is a greater concentration of oxidizing species in the combustion products with respect to solid rockets, which emphasizes the throat erosion phenomenon. Hence, the need for an accurate physical understanding of this process is fundamental for technology advancement. The aim of this work is to investigate the graphite nozzle erosion in 2kN-class hybrid rockets burning high-density polyethylene (HDPE) and oxygen. The main focus of the work is the evaluation of nozzle throat erosion and wall temperature as a function of motor operating conditions by performing numerical simulations from a proven in-house CFD-solver. The results obtained from a detailed parametric analysis are discussed and then used to derive a regression law for nozzle throat erosion. The regression law here proposed is then validated through comparison with the experimental results obtained from lab-scale 2kN-thrust class rocket firing tests performed at Hokkaido University.