Since the ability of changing flow Mach number in high speed wind tunnels is limited, the boundary of the inlet starting Mach number cannot be obtained easily. Studies are conducted in the present paper to help the wind tunnel experiments to obtain the boundary of the inlet starting ability and to verify that the cases of different freestream Mach numbers can be simulated by changing the attack angle of the inlet model. The correlations between changing the attack angle at a specific freestream Mach number and changing the freestream Mach number at a specific attack angle which affect the starting performance of the 2-D hypersonic inlet are investigated. The results show that the critical attack angle of unstarting and self-starting of the inlet at Ma∞=5.9 flow are in the range of 12°~13° and 0°~1°,respectively. It is found that the effective flow Mach numbers at the entrance of the inner contraction of the 2-D inlet are reasonably consistent at the unstarting limit and the self-starting limit,either by changing attack angles or by changing freestream Mach numbers. Moreover,for the same effective flow Mach number at the entrance of the inner contraction,when the variation range of the attack angle is less than 4o,the inner flow field and the wall pressure distribution obtained by the two methods are similar,otherwise the differences are very apparent. This indicates that for 2-D hypersonic inlets,when the Mach number of a conventional wind tunnel is near the boundary of the inlet starting ability,one can try to simulate the cases of different freestream Mach numbers by changing the attack angle within a certain range in wind tunnels to obtain the inlet starting behaviors.
Journal of Propulsion Technology
Angle of attack