Numerical analysis of scramjet isolator configurations of three different cross-sectional transition functions

The isolator is a key component of the scramjet engine integrated with the airframe. It can either accommodate high backpressure from intensive combustion at the supersonic combustion mode, or provide subsonic flow for effective combustion at subsonic combustion mode. The earlier studies on the isolators mainly focused on the constant-area cross-section configuration, while other configurations such as linear divergent and step isolators are rarely investigated. In this work, all of the three configurations with regard to the Mach number, the backpressure, the inflow angle, the divergent angle, and the step height and quantity are numerically investigated in this paper. The conclusions from the investigation show that the constant-area isolator has worse performance than the linear divergent and the step isolators in terms of start Mach number, backpressure tolerance and operating Mach number range. Moreover, the results suggest that it is prior to select a linear divergent isolator with the divergent angle of about 0.75° over the constant-area isoaltor. The step isolator with the small step height and a few steps has the best performance.