| Scroll compressor is a fluid machinery based on the regular change of volume to achieve medium compression.Because of its high efficiency,light weight,small volume,small vibration,low noise and high reliability,it is widely used in air conditioning,refrigeration,vacuum pump and other industries.With the continuous progress of industry technology,the application of scroll compressor is gradually expanding to the fields of medicine,food preservation,heating,etc.And it is more and more recognized by the compressor industry.Compared with the constant cross-section scroll compressor,variable cross-section scroll compressor has attracted much attention because of its superior performance.However,there are still some key problems in the design of scroll compressor with variable cross-section:1)The traditional design method based on variable cross-section can only meet the requirements of single control variable;2)The existing research on the optimization design of scroll is limited to improve its geometric performance and ignore the mechanical property.Therefore,in order to solve these key problems,this paper studies the parametric modeling theory of the variable cross-section scroll,the influence of different design parameters on the performance of the variable cross-section scroll,the multi-objective optimization design method of the variable cross-section scroll,the construction theory of the strength failure model of the variable cross-section scroll and the reliability analysis method.In order to expand and improve the existing design theory and method of variable cross-section scroll,provide theoretical basis and information support for the design and development of new and efficient variable cross-section scroll compressor.The main research contents and innovative achievements of this paper include the following aspects:(1)Research on parametric model and performance of variable cross-section scroll.Firstly,the coordinate transformation relationship between conjugate scroll profiles is derived based on the theory of differential geometry curve and coordinate transformation theory.Then,the mathematical model of the variable cross-section scroll composed of the base circle involute and the higher-order curve is derived by using the normal equidistant line method,compared and analyzed with the constant-section scroll,the superiority of the performance of the variable-section scroll and the importance of research are proved.Finally,considering that different design parameters have different effects on the performance of variable cross-section scrolls,the sensitivity model for each performance index of the variable-section scroll is constructed,and the comprehensive performance of the variable-section scroll is studied based on the sensitivity model,the control variable method,and combine the sensitivity model and the control variable method.The corresponding relations between the performance indexes and design parameters of the variable cross-section scrolls were established respectively,and the parameter optimization scheme of the variable cross-section scroll that meets the geometric or mechanical performance requirements is given,which greatly improves the flexibility of the parameterized design of the variable cross-section scroll.(2)Based on the adaptive NSGA-Ⅱ algorithm,the multi-objective optimization design of the variable cross-section scroll is carried out.In fact,the design variables affect the geometric and mechanical properties of the variable cross-section scroll through interaction,but it is difficult to get the best geometric and mechanical properties of the variable cross-section scroll by traditional design methods.And the design of scroll compressor is mostly aimed at the best geometric performance,but its mechanical performance is poor at present.In order to overcome this shortcoming,a multi-objective optimization design method based on adaptive NSGA-Ⅱalgorithm and considering the mechanical and geometric properties of the variable cross-section scroll is proposed,and the pareto optimal solution set is obtained.The results show that the maximum axial gas force is reduced by 3.20%,1.08%and 1.90%respectively,and the compression ratio is increased by 5.37%,6.64%and 3.35%respectively.(3)The strength failure model of variable cross-section scroll is established,and the reliability optimization are carried out.Since the stress of the variable cross-section scroll has no analytical formula,it can only rely on the finite element analysis software to analyze its strength,which not only did not consider the influence of errors caused by processing,but also difficult to directly optimize the design of geometric performance under the premise of meeting its strength requirements,resulting in relatively low efficiency in the design process.To solve this problem,a method based on the combination of finite element analysis and box Behnken response surface is proposed in this paper firstly.Then the polynomial regression equation of tooth stress is obtained,and the strength failure model is established based on the polynomial regression equation.Finally,the strength reliability of the variable cross-section scroll is analyzed by AFOSM method,and the reliability Pr=0.98726 is obtained.In order to meet the requirement that the strength reliability of key products is greater than 0.999 without reducing its geometric performance,the multi-objective optimization design of the variable cross-section scroll was carried out by constructing the adaptive SAGA algorithm.The results show that the optimized variable cross-section scroll not only has good geometric performance,but also improves the reliability,in which the stroke volume is increased by 31.75%,the failure probability is reduced from 0.01274 to 7.52e-20,and the reliability is much higher than 0.999.It not only obtains the variable cross-section scroll with high reliability and excellent geometric performance,but also enriches the parametric design method of variable cross-section scroll. |
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