径向变深雁形槽干气密封开启性能研究

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In order to improve the opening performance of the goose groove under low velocity and low pressure condition, four kinds of bottom types of goose groove, namely convergent tapered bottom groove, convergent ladder-like bottom groove, divergent tapered bottom groove, divergent ladder-like bottom groove, was introduced by optimizing the equal deep goose groove. Based on the theory of gas mixed lubrication, a dynamic opening model for the goose groove dry gas seal was developed by considering the effects of gaseous slip flow and surface roughness. The gas film pressure distributions between the two faces of the five different bottom types of goose groove were numerically analyzed. A series of simulations were carried out to study the influences of relative depth-variation slope, the depth of annular neck, and sealed medium pressure on the critical opening rotational speed and gas film stiffness. The results show that the load capability and stability of the gas film are enhanced by the optimized bottom structure compared with the equal depth groove. The critical opening rotational speed of the depth-variation bottom structure is the lowest when the relative depth-variation slope is between 3/8 and 4/8, and the divergent bottom structures have slightly advantages than the convergent bottom structures. The critical opening rotational speed of the divergent bottom structures have 10.2% reduction compared with the equal deep goose groove when relative depth-variation slope is the best value.为进一步提高雁型槽端面干气密封在低速、低压工况下的开启性能，在等深雁型槽的基础上对槽底结构进行变深优化，提出了收敛型锥度、收敛型阶梯、发散型锥度和发散性阶梯4种槽底变深结构。基于气体混合润滑理论，考虑密封端面粗糙度效应和端面间气体滑移流效应，建立了雁型槽端面干气密封动压开启分析模型，数值分析了槽底变深结构干气密封的气膜压力分布，研究了相对变深坡度、环颈深度和密封压力对变深雁型槽端面干气密封的临界开启转速和气膜刚度的影响。结果表明：与等深槽相比，槽底变深结构可提高密封端面间气膜承载能力和稳定性；在相对变深坡度λ=3／8．4／8时，变深结构干气密封的临界开启转速nc取得最小值，且发散型变深结构略优于收敛型变深结构；相对变深坡度取最优值时，发散型结构干气密封的临界开启转速nc与等深槽相比降低了10．2％。