Performance estimation of hybrid rocket by varying the flow rate at multi-location swirl injector

This study attempts to evaluate the effect of varying the oxidizer mass flow rate through the secondary mid-location swirl injector on the performance of a hybrid rocket motor (HRM). The hybrid fuel used in this study was paraffin wax along with commercially available gaseous oxygen as oxidizer. Utilizing a swirl injector is crucial as it adds a tangential velocity component alongside the axial one. Introducing a secondary mid-location swirl injector heightens this effect, leading to noticeably improved performance in HRM. An increase in the oxidizer mass flow rate through the secondary mid-location swirl injector is associated with a reduction in the regression rate. This is attributed to the blowing away of wax melt layer and flame from the solid hybrid fuel grain. Furthermore, an overall increase in the oxidizer mass flow rate corresponds to a rise in combustion efficiency, closely linked to pressure development, which, in turn, correlates with the mass flowing out of the rocket nozzle. Peak thrust was observed and also maximum fuel was burnt in case where highest gaseous oxygen (GOX) rate of 50 g/s was utilized. The multi-location swirl injector assembly maintains swirling flow towards the nozzle end, presenting an optimal scenario for enhancing HRM performance.