Utility of Multiprotrusion as the Performance Enhancer in Hybrid Rocket Motor

摘要

This paper examines the effect of single protrusion and multiprotrusion on the performance of hybrid rocket with the length/initial port diameter (L/D) ratio of 12.5. The fuel used was wax, and the oxidizer was gaseous oxygen. The protrusion used was made of nylon and it regresses during the combustion. The result indicates that the use of single protrusion placed downstream locations (0.5 to 0.8 X/L) is prominent in enhancing the regression rate as well as the combustion efficiency. Among the various protrusion combinations, the highest improvement in regression rate is obtained with the three protrusion (0.2-0.5-0.8 X/L) combination. Use of protrusions beyond three was found to be ineffective for the given L/D ratio of the hybrid rocket. Overall, the highest improvement in combustion efficiency was obtained for the double-protrusion case at 0.2-0.8 X/L and it was around 73%. The mass flux exponent for all the protrusion combinations was close to 0.5, which is the essential requirement for the hybrid rocket motor. Apart from these studies, the effect of protrusion height with graphite protrusion has also been carried out with single protrusion. It has been observed that the protrusion height of 7 mm gives relatively highest improvement in regression rate as well as the combustion efficiency.