The unlike-doublet impinging jets atomization behaviors in hypergolic liquid rocket engines are crucial for reliable ignition and combustion efficiency, while their flow mechanisms under different jets inertia disparity are not well understood. Through high-fidelity volume of fluid (VoF) simulations with intraliquid species transport, this study comprehensively quantifies the inertia disparity (characterized by diameter and momentum ratios) influence on atomization characteristics. Results show that the elevated inertia disparity reduces the spray angle and shortens the impinging liquid sheet breakup length. The primary breakup induced Sauter mean diameter distribution becomes uniform and the mixing efficiency is reduced with higher impinging jest inertia disparity. Phenomena in terms of deflection angle collapse near the central axis and mutual penetration of jets are observed at high inertia disparity conditions, causing a special trimodal flow rate distribution. The pair vortices and rotated bubbles are found after unlike jets impingement. To interpret the numerical results, further flow topology and structure analysis are conducted and it reveals that inertia disparity initiates Kelvin-Helmholtz type shear instabilities at the impingement point of jets. These shear effects then evolve into vortex structures that propagate radially from the central axis, entraining liquid sheets and generating collapse.

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• Atomization
• Drops & bubbles
• Kelvin-Helmholtz instability