Combined Effect of Diaphragm and Oxidizer Swirl on Regression Rate in Hybrid Rocket Motors

The present numerical work investigates the effect of a combination of two known regression rate enhancement techniques, namely diaphragm located in the port and swirling oxidizer flow at the inlet. Diaphragm enhances regression rate by heat transfer enhancement due to recirculation zone whereas swirling flow enhances regression rate by enhancement in radial diffusive transport. The use of diaphragm in combination with swirl was found to be more effective in enhancing regression rate compared with the individual enhancements by the two techniques. However, the net enhancement in regression rate using combined techniques was less than the arithmetic sum of enhancement from two individual techniques. Interestingly, the characteristic exhaust velocity C* is enhanced only if diaphragms are sufficiently tall.