Effects of swirling oxidizer flow on the performance of a HTPB/N 2 O Hybrid rocket motor were studied. A hybrid propulsion laboratory has been developed, to characterize internal ballistics characteristics of swirl flow hybrid motors and to define the operating parameters, like fuel regression rate, specific impulse, and characteristics velocity and combustion efficiency. Primitive variables, like pressure, thrust, temperature, and the oxidizer mass flow rate, were logged. A modular motor with 70 mm outer diameter and variable chamber length is designed for experimental analysis. The injector module has four tangential injectors and one axial injector. Liquid nitrous oxide (N 2 O) as an oxidizer is injected at the head of combustion chamber into the motor. The feed system uses pressurized air as the pressurant. Two sets of tests have been performed. Some tests with axial and tangential oxidizer injection and a test with axial oxidizer injection were done. The test results show that the fuel grain regression rate has been improved by applying tangential oxidizer injection at the head of the motor. Besides, it was seen that combustion efficiency of motors with the swirl flow was about 10 percent more than motors with axial flow.

Heat transfer and hydrodynamics of air ow in a constricted microchannel are numerically investigated by considering the e ect of geometry, stagnation pressure and temperature at the inlet, and applied heat ux at the walls. Kurganov-Tudmor method is used to solve the governing equation; Maxwell and Smoluchowski approaches are used to model the rarefaction e ects of compressible micro ow. This study shows that using slip model is necessary in both high-speed and low-speed ows, especially at the downstream of the constricted portion. Also, throat height reduction results in more rarefaction and compressibility at the constricted region.