Under the supersonic inflow conditions of a Mach number of 2.52, an experimental investigation was conducted to study the impact of introducing a rough segment in the isolator on the performance of the scramjet combustor. From three aspects including autoignition, flame stabilization, and combustion characteristics, the mechanism and characteristics of two solutions (namely, extending the isolator and the introducing rough segment) were systematically analyzed based on the turbulent boundary-layer thickness compensation theory. The results indicated that both extending the isolator and introducing the rough segment led to an increase in the turbulent boundary-layer thickness within the combustor, thereby significantly affecting the near-wall flow characteristics. In terms of effects, both the extended isolator and rough segment configurations expanded the autoignition and flame stabilization ranges as compared to the baseline configuration, and they exhibited consistent trends in combustion characteristics, demonstrating that the introduction of the rough segment is an effective boundary-layer thickness compensation solution. Meanwhile, in terms of broadening the lower boundary of stable combustion capability at low equivalence ratios in the combustor, the introduction of the rough segment exhibited additional advantages as compared to extending the isolator. Furthermore, the effectiveness of the rough segment could be influenced to some extent by the combustion heat release intensity.
Zhao et al. (2026) studied this question.