Regression rate and combustion performance investigation on hybrid rocket motor with head-end swirl injection under high geometric swirl number

It is well known that head-end swirl injection can overcome the key problem of low regression rate and combustion inefficiency in hybrid rocket motor effectively. In this paper, the effect of head-end swirl injection under high geometric swirl number (above 10) has been investigated by numerical method. Three-dimensional structured mesh technology has been used. The numerical model coupled of turbulence, combustion, solid fuel pyrolysis and solid-gas coupling model was proposed in this paper. A series of cases which indicate the head-end swirl injection under high geometric swirl number can extremely improve the fuel regression rate and combustion efficiency of hybrid rocket motor are conducted. Compared to conventional axial injection, when the geometric swirl injection is 44.9, the improvement of average fuel regression rate reaches 3.23-4.93 times, and the combustion efficiency increases to 93.9-95.8% under different oxidizer mass flux. Besides, the parameters, including oxidizer mass flux, geometric swirl number and injection velocity component ratio, exert great influences on the hybrid rocket motor with head-end swirl injection in different ways. Through integrated design of the injector, the oxidizer to fuel ratio (O/F ratio) could equal to the optimal O/F ratio 1.93 approximately and be stable during the rocket motor operation, so the rocket motor performance will be in high and stable status.