Abstract:
Hybrid rocket propulsion is a rising propulsion system having features such as low cost, safety and environment friendliness. Despite of such features it has certain issues like mixture ratio shifting; low regression rates, mixing inefficiencies etc.which bound its use as a prime propulsion system. Amongst all these issues the present analysis represents an approach for rectification of one of the most important issue namely, low fuel regression rate. The fuel regression rate can be increased by increasing oxidizer flow speed over the burning fuel surfaces. This is because flow over the burning surface creates shear stress which facilitates fuel and oxidizer mixing. (By inducing an oxidizer vortex into the combustion chamber improving shear stress and thus regression rate.) The Cylindrical Stepped Cosine Shaped Fuel Grain is one of the mean to create vortex combustion field in a port. To generate this flow, oxidizer is injected axially in the fuel grain and vortex created inside the grain due to different size of cylindrical port size. To investigate the solid-fuel regression rate behaviour and operating characteristic of stepped solid fuel grain hybrid rocket motor a series of static rocket firing were conducted. Results from eight tests of laboratory scale hybrid rocket motor using polyvinyl chloride and gaseous oxygen have been presented here at different oxidizer injections pressures i.e. 16.872, 21.092, 28.122, 42.184, and 48.511 (kgf/cm2) respectively. Compared to cylindrical grain, a higher regression rate has been observed in the case of cylindrical stair fuel grain.
Keywords: Fuel Grain, Regression Rate, Web Thickness, Mass Flow Rate, Injection Pressure, Fuel Flow Rate