Curvature-induced asymmetry governs obstacle–flame coupling and detonation initiation in spiral microchannels

This study investigates the effects and mechanisms of wall obstacle arrangements on flame acceleration and deflagration-to-detonation transition in spiral curved channels using quasi-direct numerical simulations. The results reveal that obstacle performance is strongly influenced by the curvature-induced asymmetric flow field, which fundamentally differs from that of straight tubes. Inner-wall obstacles couple effectively with the primary acceleration region, significantly enhancing flame wrinkling, vortex–flame interactions, and shock focusing, thus achieving the shortest initiation distance and earliest detonation onset among the uniform arrangements. In contrast, outer-wall obstacles interact weakly with the flame during the early stages and mainly contribute through delayed shock reflection, while symmetric double-wall obstacles provide intermediate performance due to dispersed disturbances. Mechanistic analysis shows that inner-wall obstacles trigger multi-point localized explosions through shock convergence, whereas outer-wall obstacles initiate detonation via reflection-induced hotspots. These findings highlight the necessity of adapting obstacle strategies to asymmetric flow fields. Furthermore, a novel segmented obstacle strategy is proposed and verified, demonstrating that placing inner-wall obstacles upstream and outer-wall obstacles downstream significantly enhances initiation performance. This work provides new insights into detonation control in curved micro-scale channels and offers guidance for the design of compact high-performance pulsed detonation devices.