Analysis of Self-Cooling Characteristics for Diffuser Self-Pumping Mechanical Seal

As an important shaft seal device, themechanical seal is widely used in rotating equipment in petrochemical, electric power, aviation and other important fields because of its simple structure and good sealing. The existing mechanical seal structure has the problem that the fluid viscous shear heat and friction heat can not be lost in time, which will not only vaporize the liquid film on the seal face, resulting in the imbalance between the dynamic and static rings, but also cause the end face deformation and hot crack, resulting in seal failure. With the improvement of seal working parameters, both contact mechanical seal (CMS) and traditional spiral groove mechanical seal (TSGMS) are incompetent. Therefore, a new mechanical seal structure with excellent cooling performance was urgently needed. The diffuser self-pumping mechanical seal (DSPMS) was a kind of fluid-pumping dynamic mechanical seal designed based on the working principle of a centrifugal pump. Taking DSPMS as the research object, the fluid-thermal-solid coupling model was solved and analyzed by using Fluent software, and the heat transfer process and end temperature distribution in DSPMS structure were discussed. Under the condition of the same face width and dam width, the self-cooling characteristics of DSPMS were revealed by comparing and analyzing the temperature rise and flow field distribution of contact mechanical seal (CMS), traditional spiral groove mechanical seal (TSGMS), and DSPMS. The influence of different structural parameters on the cooling performance of DSPMS was discussed by single-factor analysis. The results showed that the self-circulation of the fluid in DSPMS could effectively remove the viscous shear heat between the seal faces and reduce the temperature rise of the seal faces. Compared with TSGMS and CMS with the same face width and dam area width, the end face temperature rise of DSPMS was reduced by 58% and 83%, respectively. The temperature of the stationary ring of each seal structure was higher than that of the rotary ring, and the highest temperature of the end face appeared on the inner diameter side of the end face, and its value increased rapidly with the increase of the spindle speed. With the increase of diffuser ring groove depth h_k and spiral groove depth h_g, the average liquid film thickness increased and the fluid viscous shear heat decreased. However, when the diffuser ring groove was too deep, the opening force decreased with the increase of rotational speed. With the increase of groove width ratio γ, the cross-section of the spiral groove expanded and the pumping effect was enhanced. The increase of helix angle α and slot number N had little effect on the temperature. In the range of solving parameters, the increase of diffuser ring groove depth h_k, spiral groove depth h_g, and groove width ratio γ could not only improve the cooling effect of DSPMS, but also have a certain influence on the leakage rate between seal faces. The research results could provide an idea for designing a new sealing structure with excellent cooling performance.