Controlling detonation waves in supersonic conductors

Scramjets are important parts of future hypersonic air-breathing propulsion systems because of their excellent thrust performance. However, the existing scramjet technologies are based on the isobaric combustion cycle, which hinders the significant improvement in the engine thrust performance.

Cai et al. explore the mechanisms that can help to effectively control the detonation wave in a supersonic combustor, which is vital for developing efficient combustion organization technology. An in-depth understanding of these mechanisms will help guide the practical application of detonation engines to explore the mechanisms of detonation propagation, and stabilization in expanding combustors with nonuniform supersonic flow.

“In this work, we aim to gain deep insight into the self-sustaining mechanism of detonation wave in expanding channels with nonuniform incoming flow,” said author Xiaodong Cai.

Using high-precision numerical simulation, the researchers monitored the dynamic process of detonation wave propagation in the expanding channel. They observed that under non-uniform velocity, more unburned gases are generated behind the detonation wave, which interacts with turbulence resulting in the forward propagation of detonation rather than decay.

“For the first time, we explore the role of fine turbulent flow features and their interaction with the unstable shear layers and unburned jets in expanding channels with nonuniform incoming flow,” said Cai. “This will directly or indirectly affect the structure and propagation mode of the detonation wave.”

The researchers found in the same expanding combustor model, the detonation front under the uniform flow condition gradually attenuates, whereas under the non-uniform flow condition, the detonation wave continues to propagate forward. Moreover, two unburned jets are generated and consumed periodically behind the detonation wave.

Source: “Effects of velocity shear layer on detonation propagation in a supersonic expanding combustor,” by Jian Dai, Fei Xu, Xiaodong Cai, and Yasser Mahmoudi, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0065348 .