The Effect of Injector Geometry on Performance of a Lab-Scale Hybrid Rocket Motor

This study includes the investigation of the effect of injector geometry on the performance of a 200 Newton class laboratory hybrid rocket motor using a paraffin wax/gaseous oxygen propellant pair. The diameter, number, and geometrical placement of orifices on the injector plate are examined to define the best shower-head injector geometry. The mass flow rate and total orifice area are calculated analytically for the motor to reach the desired thrust value according to the design parameters. The final injector geometries are determined by Computational Fluid Dynamics analysis. As a result of numerical studies, three injectors configured with 8, 15 and 33 orifices are defined as the closest value. These injectors have been produced and also examined experimentally to validate the numerical results. According to the experimental studies, the thrust variation of each motor are obtained as a function of time. This study aims to study the effect of changes in injector geometry on the overall performance of the hybrid rocket motor.