Investigation of Combined Groove Design for Turbopump Mechanical Seals in Liquid Rocket Engines and Their Effects on Sealing Performance

To address the insufficient liquid film load capacity, high leakage rate, and severe friction and wear under low-speed operating conditions of mechanical seals in high-speed and large-pressure-difference pump turbines, a stepped-groove face seal for liquid rocket engine turbopumps is proposed in this study. Different from conventional linear and spiral grooves, this novel structure exhibits favorable friction and wear performance under low-speed steady-state conditions and exhibits favorable friction and wear performance under low-speed steady-state conditions. Fluent numerical simulations and friction-wear tests are conducted to compare the flow field characteristics and sealing performance of the three groove types, and the optimal structural parameter range of the stepped groove is determined. The results demonstrate that the stepped groove outperforms spiral and linear grooves in overall sealing performance. Within a groove depth of 6–14 μm, its opening force is 2.25% and 59.27% higher, while the leakage rate is 3.35% and 10.95% lower, respectively. Within the investigated helix-angle range of 13–17°, the stepped groove consistently exhibits better sealing performance than the spiral groove. The maximum opening force of 256.867 N is obtained at a helix angle of 15°, which is 2.95% higher than that of the spiral groove, whereas the minimum leakage rate of 0.52071 g/s occurs at 13°, approximately 3.95% lower than that of the spiral groove. Particularly under high-speed conditions, the stepped groove exhibits further enhanced advantages, with opening force increased by 18.23% and 62.43% and leakage rate reduced by 6.40% and 17.58% compared with spiral and linear grooves. The stepped-groove structure exhibits favorable sealing and tribological performance under the tested conditions, providing a useful design reference for high-performance mechanical seal optimization.