Research On The Analysis Method And Structure Improvement Of Piston Rod And Cap Seal Of Stirling Engine

From the perspectives of energy utilization efficiency,environmental protection,and cost,disc solar thermal power generation has great development prospects.Stirling engine is a key component in the dish solar thermal power generation system,and its sealing performance directly affects the working efficiency of the solar power generation system.To solve the problem of medium pollution and leakage at the piston rod of the Stirling machine,researchers have designed a cap type seal.In the study of cap seals,the finite element method is a common analysis tool.Therefore,improving its computational efficiency,ensuring the accuracy of its analysis results,and guiding engineering applications to reduce the risk of leakage and pollution of Stirling machine working fluids have become important issues to be solved.This article conducts a series of comparative analysis from the perspectives of finite element modeling,installation methods,and structure for the Stirling machine cap seal.The simplification of this three-dimensional problem into a two-dimensional axisymmetric model and the influence of different pre compression methods on finite element analysis were obtained,thus determining the optimal modeling and installation method of the cap seal and applying it in subsequent analysis.Based on the analysis results and research status of the cap seal,an improved structural finite element model was established and compared with the existing structure.Finally,the scientific feasibility of the optimization and improvement was verified through bolt disc friction and wear tests.After the above research,the following conclusions are drawn:1.Comparing the simplified two-dimensional axisymmetric and three-dimensional models of cap seals,the stress and deformation size distributions of the two methods are similar,but the corresponding calculation time of the three-dimensional model is more than 6 times that of the two-dimensional model.When it comes to the installation of sealing ring interference,the contact stress of the two methods shows an opposite trend with the change of interference amount.From this,it can be seen that when the research process does not require changing the tensile rate,and the main analysis objective is to compare multiple models under deformation and stress distribution or equal conditions,the two-dimensional axisymmetric model can obtain ideal results faster;If simulation needs to consider the impact of different stretching rates on the results,a two-dimensional axisymmetric model can cause significant errors.2.Due to the different forces acting on the O-ring,there are significant differences in the distribution and magnitude of stress and deformation between the radial compression method model and the axial propulsion method model,with a deviation of up to 40%.However,the axial propulsion method has less stress concentration and greater sealing force on the sealing surface.From this,it can be concluded that for cap seals,the axial compression method is more suitable.Although the radial compression method can simplify calculation and improve speed in the analysis,its accuracy is not as good as the axial compression method.3.After optimization and improvement,the stress concentration phenomenon on the original structure O-ring was almost eliminated,and the maximum equivalent stress was reduced by nearly 50%.The average contact stress of the sealing ring increased by 11.3%,and the effective sealing area increased by nearly 40%.Among the three key parameters of medium pressure,friction coefficient,and piston motion speed,medium pressure has the greatest impact on sealing performance.The sealing performance of the final selected structure is the best when its value is 6～8.5MPa.From the experimental results,it can be seen that the wear rate and friction coefficient of the bolt specimen are both non-linear related to the load and have a significant change.The increase in wear rate occurs when the load increases to 160N(≈8.5MPa).Therefore,it can be seen that reasonable planning and quantitative design of the contact pressure of the sealing surface is the key to solving the problem of reducing wear and prolonging life of the cap seal structure,which reversely proves the scientific nature of structural optimization and improvement.In summary,through finite element analysis and comparison,this article has identified the most suitable modeling and installation methods for cap seals in the simulation process,obtained the performance characteristics of improved structures,and supplemented them with experimental verification,providing analysis methods and design guidance for the research and application of cap seals.