Regression rate characteristics of hybrid rocket motor with helical grain

This paper concentrates on the fuel regression rate characteristics of hybrid rocket motor with helical grain and attempts to overcome the low regression rate shortcoming of conventional hybrid rocket motor. Both three-dimensional numerical simulations and lab-scale firing tests are conducted to analyze the regression behavior of solid helical fuel grain. Gaseous oxygen and polyethylene are utilized as the propellants. Head axial injection method and Laval nozzle are adopted in the motor. A steady numerical model based on pure-gas-phase reaction assumption is established. Flow field characteristics of the hybrid rocket motor with helical grain are identified through three-dimensional numerical simulations. Simulation results show that the helical structure can both increase turbulence kinetic energy and swirl number in the flow field. These two factors both contribute to the increase of the fuel regression rate. Geometric factors influencing the fuel regression rate are thread pitch, groove depth and groove width. Experimental results reveal that the fuel regression rate increases with the increase of the groove depth and the groove width. The thread pitch can also obviously influence the regression behavior of the helical grain. Overall, the helical grain can effectively increase the fuel regression rate of hybrid rocket motor.