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Abstract: The hydraulic spool valve is a critical control component in aerospace hydraulic systems. However, complex working environments can cause the valve core to become stuck, thus severely restricting the performance of such valves. This in turn can hinder precise control of hydraulic oil, reduce the stability of the hydraulic system, and lead to serious accidents in aerospace systems. The unbalanced radial force and solid particle intrusion into the fit clearance are the main factors behind this sticking. To better understand these issues, in this study we simulated the fluid dynamics and particle behavior within the clearance of the valve core, and analyzed the effects of inclination angle, clearance size, particle diameter, and pressure equalization groove (PEG) properties. The mechanism behind valve core sticking was revealed, and it was found that the PEG has an inhibitory effect on the unbalanced radial force and the particle intrusion. Furthermore, we propose an optimized structure for a triangular pressure equalization groove with an arc-shaped bottom (Tri-PEG). The structural parameters were determined through multi-objective optimization, with the objectives of minimizing the leakage at the clearance and maximizing the particle volume fraction at the bottom of the Tri-PEG. The optimal parameters were an arc-shaped radius of 0.2 mm, a groove depth of 0.392 mm, and a groove width of 0.215 mm. Comparing the Tri-PEG with a rectangular PEG, the leakage was reduced by 12%, and the particle concentration was increased by 6%. Overall, these findings serve as an important reference for alleviating spool valve sticking.