Dynamics of detonation propagation in a wedged variable-section channel

Presence of wedge surfaces and variable-section geometries in conventional combustion chambers can modify the structure and propagation characteristics of detonation waves, furtherly influences the operational stability and propulsion efficiency of detonation engines. In this study, trapezoidal obstacles were symmetrically arranged within a shock tube to create channels incorporating convergent wedge sections with different angles (30°, 60°) and subsequent narrow straight segments with various heights (5, 10, 20 mm). Experimental and numerical investigations were conducted to analyze the propagation characteristics of stoichiometric ethylene-oxygen detonation waves in the channel. The results indicate that the detonation wave reflected by the wedge surface enters the narrow segment is overdriven, with the overdriven degree gradually decreasing during its propagation. At the 30°wedge, Mach reflection occurs, and the detonation wave becomes overdriven upon reaching the contracted throat with an overdriven degree exceeds 1.5; whereas, at the 60°wedge, regular reflection occurs, and the detonation wave reaches the throat with a lower overdriven degree of 1.3. However, the overdriven degrees finally decay to 1.1 in both cases. The channel contraction effect attributes to the induction of overdriven initiation in the throat, though it operates via distinct mechanisms as the wedge angle varies. For the 30°wedge, channel contraction shortens the travel distance of triple points on the wavefronts of the incident detonation wave and Mach reflection-induced detonation wave, increasing their collision frequency, leading to significant energy accumulation in the throat region. For the 60°wedge, channel contraction prevents triple points from entering the following narrow segment along trajectories corresponding to their original cell widths, furtherly induces structural self-adjustment to sustain propagation. These findings enhance the understanding of detonation wave propagation under complex geometrical conditions and provide valuable insights for the optimal design of combustion chamber structures in detonation engines. Novelty and significance statement This study innovatively investigates the propagation process of detonation waves in a convergent channel that simultaneously incorporates a wedge surface and a variable-section structure, thereby being more relevant to practical engineering scenarios. Furthermore, it innovatively examines the coupled influence mechanism of wedge surface reflection and wall contraction effects on the propagation characteristics of detonation waves, filling the gap in related research. A detailed comparison and analysis of the propagation processes of detonation waves entering narrow straight segments after different reflections was conducted, revealing the overdriven propagation characteristics of detonation waves during this process and their induction mechanism (frequent collision of triple points). This study provides new insights and support for the propagation dynamics of detonation waves in complex channels.