Research On Multi-objective And Multi-condition Optimization Of Dynamic Pressure Mechanical Seals

The hydrodynamic pressure type mechanical seals have broad application prospects due to their full fluid lubrication,frictional power consumption,low temperature rise and long service life.Because the application environments and conditions faced by the dynamic pressure type mechanical seal are various and complex,how to determine the end face shape parameters according to the actual requirements to obtain excellent seal lubrication performance is a matter of great concern in the research and development and application of the product,especially when the application conditions and design conditions of seals do not match or changes in working conditions occur in sealed use,how to keep the seals in good operating condition under changing conditions requires scientific optimization.This article will be funded by the National Natural Science Foundation of China(No.51279067)and take the spiral groove upstream pumping mechanical seal as an example,for the first time considering the optimization of the working conditions change,to optimize the multi-objective and multi-operating conditions of the upstream pumping mechanical seal.The main research job and conclusions are as following:1.On the basis of Cavitation model and dynamic mesh technology,the numerical calculation of the flow field in the micro-gap pumping mechanical seal upstream of the spiral groove was carried out.The influence law of the working condition change on the seal lubrication performance was analyzed,and the working conditions of the optimization study were determined range.2.Set up a process of multi-objective and multi-condition optimization design based on CFD flow field calculation,optimize the mathematical model,analyze and determine the optimization variables and optimization objectives;use the uniform test design method to construct the design matrix;use the fuzzy set theory to determine the weight factors of the liquid film stiffness and leakage under different working conditions;weighted under three conditions The average leakage and weighted average stiffness are objective functions,and the performance constraints are determined.The effects of different prediction models such as response surface model,Kriging model and artificial neural network model on the optimization result are compared;the Kriging approximation model is used to obtain the liquid film stiffness of the optimized target.K,the relationship between the leakage Q and the optimized variable groove depth h,the helix angle?,the groove diameter ratio?,the groove width ratio?,and the influence of the optimization variables on the optimization objectives are analyzed.3.Based on the analytic hierarchy process,exhaustive search method and multi-objective optimization algorithm,the optimal design of the seal was performed.Two different optimization methods and optimization results were compared and analyzed.The results show that the two optimization methods have significantly improved the sealing performance.The optimized sealing film stiffness after exhaustive search and genetic algorithm optimization is 11.76%and 14.44%higher than the original seal at 0.1 MPa,respectively,and the working pressure is 0.3MPa.It increased by 10.5%and 12.2%,respectively,and increased by 4.8%and 5.8%under1MPa conditions,while the leakage amount decreased by 11.69%and 14.26%under0.1MPa,and decreased by 13.64 under 0.3MPa.%and 16.15%,respectively,decreased by 5.24%and 6.45%at 1 MPa.4.The BVF diagnostic method was used to analyze the flow field in the seal before and after optimization.The results showed that the BVF of the spiral groove surface was smaller than the original seal,and the uniformity index?_a was closer to 1,whether it was the peak value or the mean value.In terms of genetic algorithm optimization results,the BVF peak and BVF mean are smaller and the uniformity index?_a is higher.At the same time,a comparison of the seals before and after optimization was conducted to further verify the correctness of the optimization results and the rationality of the optimization method.This study will provide a theoretical basis and practical reference for the optimal design of non-contact mechanical seals.