Application of Throat Compensation Based on Scale Effects of the Scramjet Combustor

This paper investigates a throat compensation design method applied to the large-scale scramjet combustor based on the scale effect of supersonic combustion under a Mach 2.52 inflow. The variation in the relative thickness of the boundary layer at the throat of different-scale combustors would lead to the difference in the actual effective flow area. To compensate for the changes in the effective flow area caused by the scale effect in combustors, the throat compensation theory was derived, and the compensation design method was established. By designing three combustors with different geometric structures, the small-scale, large-scale, and large-scale combustors with throat compensation were tested and compared. The results indicate that the throat geometry setting has a significant impact on the scale effect of the scramjet combustor, and this impact is closely related to the combustion modes. In the Scram and Dual modes, the throat compensation can rectify the out-of-design proportional scale-up of the effective flow area through effective geometric configuration, which ensures the combustion characteristic does not deviate due to scale variation. However, in the Ram mode, the throat compensation presents an overcompensating effect because the nonproportional variation of boundary-layer thickness with the combustor scale has little effect on combustion.