| Scroll compressors are widely used in fields such as energy,gas compression and so on due to its simple structure,high efficiency and good stability.At present,researches on the mathematical model and optimization design of circular involute scroll compressors are becoming increasingly perfect and mature.Scroll compressor based on involute of circle with variable radii(ICVR-STC)has many advantages such as large suction volume,high tooth head strength,compact structure and steady working process and so on compared with ordinary one.However,due to the complexity of its profile changes,the existing researches on the key technical issues of its mathematical model and optimization design are not deeply perfect.Therefore,the mathematical model of which will further be deduced and improved based on existing researches,the various geometric and force performance will be studied and a more comprehensive multi-objective optimization model will be established in this thesis.The main research contents of this study are as follows:(1)Based on the meshing theory of conjugate profile,the parametric expressions of involute of circle with variable radii(ICVR)are analyzed and derived using normal equidistant generation method,the calculation formulas of all profile parameters and geometric structure parameters are given,the generation differences of scroll teeth with different base circle radii variation coefficient and polytropic index are compared.the calculation formulas of tooth thickness and profile length are deduced and the changing trends of tooth thickness and leakage line length values are analyzed and verified.(2)Based on existing ICVR-STC tooth head modification principle,a complete tooth head modification geometric model is established,accurate calculation formulas of tooth head modification performances are deduced by using the area partition method.The difference between double-arc and double-arc plus straight line modification is compared.The influence of the base circle radii variation coefficient and polytropic index on the modification parameters and performances is studied quantitatively,the abnormal phenomenon that the modified area coefficient suddenly changes and the tooth area utilization rate is negative is also discussed.The discharge characteristics of different tooth head modification methods and discharge holes are analyzed and the optimization selection strategy of discharge holes is given.(3)The differences in calculating the working chamber volume of ICVR-STC using normal equidistant method,Green’s theorem method and graphical method are compared and the error sources are analyzed,the accurate geometric model of the whole working chamber volume of ICVR-STC is given and the differences of geometric model of four different types of scroll compressors are compared and analyzed.Based on the established geometric model,the changing trends of pressure,temperature,mass and leakage in the working chamber with orbiting angle of ICVRSTC under adiabatic compression are studied,at the same time,the gas force mathematical model of ICVR-STC is deduced and analyzed.(4)Based on the theory of multi-objective optimization,multi-objective optimization algorithms and sensitivity,the sensitivity analysis model of corresponding performance is established.Multi-objective optimization models with different performance combinations as objectives and considering nonlinear constraints are established,the difference of performance indexes between NSGA-II and MOPSO and the difference of results whether nonlinear constraints are considered are compared.A prototype used in automobile air conditioner is taken as an optimization object,three groups of multi-objective performance optimization are conducted,the suction volume and tooth area utilization rate are selected as a group of optimization example,the performance is improved by 6.5% and 4.27% respectively after optimization compared with original one.The characteristics of the multi-objective algorithm optimization results of existing scroll machines are summarized and analyzed,this research provides a further theoretical reference for the design and practical application of ICVR-STC. |
