Leakage rate and opening force are two important indicators for evaluating the performance of non-contact mechanical seals. The current research on structural optimization of non-contact mechanical seals is limited to seal rings with fixed inner diameters, and the optimization results lack generality. Taking the new type of diffuser type self-pumping fluid dynamic mechanical seal as the research object, numerical simulation method is used to analyze the interaction effect of two pairs of end-face structural parameters, namely, sealing dam length and spiral groove groove length, as well as spiral groove groove length and diffuser ring groove width, on the sealing performance; based on the homogeneous experimental design and multivariate regression analysis method, the prediction model for the opening force and leakage rate of the diffuser type self-pumping fluid dynamic mechanical seal is established; and NSGA2 genetic algorithm is used to predict the opening force and leakage rate of the diffuser type self-pumping fluid dynamic mechanical seal. NSGA2 genetic algorithm is used for dual-objective optimization to obtain the Pareto optimal solution set, and then the optimal structural parameters with different weights are screened out from the solution set by combining with the TOPSIS method.

The research results showed that for small and medium-sized shaft diameter of the diffuser type self-pumping fluid dynamic mechanical seal, the spiral groove root diameter becomes larger, so that the spiral groove becomes shorter at the same time, the sealing dam becomes longer, the opening force and leakage are reduced, the opening force becomes smaller slowly and then faster, the leakage is faster and then slower; the root diameter of the spiral groove outer diameter becomes larger, so that the spiral groove becomes longer at the same time the diffuser ring groove becomes narrower, the opening force of the end face shows a tendency to rise and then decline, the leakage rate is an overall upward trend. The overall leakage rate was on the rise. The ratio of the dynamic ring end seal dam length to the spreading ring groove width was between 1.46 and 2.01, and the ratio of the spiral groove groove length to the spreading ring groove width was between 1.32 and 1.86, which optimized the sealing performance. The research results provided a theoretical basis for the design of the dynamic ring end face of diffuser type self-pumping fluid dynamic mechanical seal.