Passive Suppression of the Gradual Opening Effect in a Wave Rotor Combustor via Flow-Field Reconstruction Induced by an Unpartitioned Inlet Duct

Abstract The wave rotor combustor (WRC) represents a promising technology for pressure-gain combustion. However, its combustion stability remains constrained by inadequate fuel–air mixing, resulting from interface distortion and vortex formation induced by the gradual opening of the channels. This study numerically investigates the flow-field characteristics in inlet ducts with three different lengths (25, 50, and 75 mm), comparing partitioned and unpartitioned designs. Results demonstrated that the unpartitioned design significantly improves mixture distribution, reducing the axial length of the fuel distribution by 24.5%–38.2% and enhancing mixture uniformity by 28.5%–40.4%, while concurrently reducing the overall system pressure loss. These advantages are most pronounced at inlet duct lengths of 50 and 75 mm. Notably, within the unpartitioned inlet duct, the Euler number decreases dramatically from 11.71 to 0.06 as the inlet duct length increases from 25 to 75 mm, signaling a fundamental transition from pressure gradient–dominated to inertia-dominated flow. This flow shift effectively suppresses the interface distortion caused by gradual opening, promoting a more uniform mixture and shortening the flame propagation path. Consequently, our findings propose a passive, geometry-only strategy to enhance WRC performance and extend its operational envelope without requiring additional actuators or control hardware. This work provides a valuable foundation for advancing the engineering application of WRCs.