Investigation On Local Profile Correction Of Oil-free Scroll Compressor Under Multi-field Coupling

In recent years,the oil-free scroll compressor has been widely used due to its unique advantages,and many experts and scholars have explored and researched it in many aspects.However,all the current studies o n this aspect have used the method of changing the parameters of the scroll profile,which tends to lead to change of the whole profile defined by the parameters and does not have the property of local modification.To solve the problem above,this paper firstly established geometric model of the oil-free scroll compressor and analyzed the forces on the orbiting scroll,then obtained the deformation of the scroll teeth by using the finite element method and defined the local correction interval,after that,a kind of design method for the scroll profile based on B-spline was proposed,which can be both locally modified and overall adjusted,and based on this method,finally,the local correction of the scroll profile based on B-spline was realized and the best assembly clearances before and after correction were compared.The main research contents of this paper are as follows:(1)The geometry theory of scroll profile of oil-free scroll compressor was described,the equation of scroll profile was given and the geometric model was established,the working chamber was divided,the overall and single working chamber volume and their change rates were calculated by using software programming;Then,this paper analyzed the forces on the orbiting scroll,using software programming,the gas forces and moments acting on the orbiting scroll were calculated with respect to the orbiting angle.(2)Based on the established geometric model,force analysis and the temperature and pressure of each chamber measured under actual working conditions,finite element analysis of the scrolls and their assemblies under single load and multi-field coupling were carried out respectively,the parts with larger deformation of inner and outer wall surfaces of the scroll tooth were defined as the local correction intervals,finally,the best assembly clearance was obtained by using the control variable method.(3)Taking cubic uniform B-spline and cubic quasi-uniform B-spline as the objects of investigation,the scroll profiles of the prototype described by two kind of B-splines described above were obtained by using the inverse control method,then the two scroll profiles were discretized and their error distances compared with the prototype were evaluated,the results showed that with the same control points,scroll profile described by cubic quasi-uniform B-spline is more accurate,finally,formulas about the working chamber of the compressor based on B-spline were given and the working chamber volumes before and after correction were calculated and compared.(4)Based on the new scroll profile expressed by cubic quasi-uniform B-spline and the known deformation of the inner and outer wall surfaces of the scroll tooth and local correction intervals described above,adjustments were made to the positions of the control points in the corresponding local correction intervals on the new profile,then the scroll profile after local correction was obtained,3D models of the orbiting scroll and the fixed scroll and their assembly after local correction were established.(5)Finite element analysis of the assemblies after local correction were carried out,its best assembly clearance was obtained and then campared with the result before correction,the result showed that after local correction,the axial clearance is basically unchanged,while the best radial clearance of the assembly is reduced,which proves the feasibility and correctness of the profile design method proposed in this paper.