Propagation characteristics of detonation waves in a semi-confined straight channel with transverse concentration gradients

This study uses the OpenFOAM platform to simulate detonation wave propagation in semi-confined straight channels with transverse concentration gradients. The effects of gradient magnitude and gradient direction on lateral expansion, wave system evolution, cellular structure, and propagation distance are examined. The results show that a small concentration gradient favors stable propagation, because reflected waves can detach from the inert gas interface and regenerate transverse waves on the detonation front. As the gradient increases, incomplete reaction behind the wave becomes more severe, local decoupling is more likely to occur, and the detonation wave quenches over a shorter distance. The direction of the concentration gradient plays a decisive role. For a negative concentration gradient, reflected waves tend to move downward and interact with the wall or transverse waves, which helps recover the cellular structure and extend the propagation distance. For a positive concentration gradient, reflected wave development near the inert gas interface is weakened, and the propagation distance is generally shorter. However, when the positive gradient is large, the wavefront inclines strongly toward the bottom wall. This promotes local convergence of transverse waves and reflected waves, forming high-temperature and high-pressure regions that reinforce the detonation structure. As a result, the propagation distance under a large positive gradient can exceed that under the corresponding negative gradient. These findings clarify how transverse concentration gradient direction controls detonation lateral expansion and provide guidance for rotating detonation combustor design and explosion safety in non-uniform leakage environments.