Research And Development Of Screw Rotor Reverse Design System

Screw compressor is widely used in various fields because of its advantages of high efficiency,energy saving,high reliability,convenient operation and maintenance and strong adaptability.The screw rotor,the core component of screw compressor,is created with the method of arraying and spiraling based on the rotor end profile.The performance of the compressor is determined by the performance of the rotor end profile.At present,the design methods of rotor end profile mainly include multisegment tooth curve method,forward design method and reverse design method.Although these design methods have been widely used in China,the performance of domestic profile is still inferior to that designed by foreign advanced enterprises.In this background,in order to quickly and effectively solve the problem of large performance gap between domestic and foreign screw compressors,based on the studying of the rotor performance analysis and the calculation method of grinding wheel profile necessary for rotor development,the profile pretreatment method for rotor reverse development and the rotor variable volume design method for realizing the design of compressors with different volume flow based on a certain profile are further studied in this thesis.Therefore,a set of screw rotor reverse design system has been developed.The main work is as follows:(1)The Simpson numerical differentiation method is used to determine the boundary conditions,and the cumulative chord length parameter cubic spline method and Newton iteration method are used to solve the rotor space contact line;Then,the complete contact line is obtained by means of interception,splicing and reassembly,and the problem of poor solution accuracy at the first and end points of the contact line is completely eliminated;Then,a method of calculating the average total length of the contact line between meshing rotors by using the transient averaging model is proposed,which provides a favorable basis for judging the internal gas leakage of the compressor;Finally,the area between the teeth of the rotor is calculated using the cubic B-spline theory,and the mathematical model of the pressure between the teeth varying with the volume between the teeth is established based on the projection area method of the volume between the teeth,and the calculation of the pressure distribution between the teeth of the rotor is completed,and the foundation for the design of the compressor and its suction and exhaust ports is laid.(2)Based on the projection area method,the influence of the gas pressure on the rotor in the meshing motion of the rotor is analyzed deeply,and the mechanical properties of the rotor in the actual working process are calculated,which provides an important basis for the selection of bearings at both ends of the rotor.(3)To the problem that the curvature smoothness of the reverse measured profile is poor than that of the designed profile during the reverse development of the screw compressor rotor,and this will result in the unsatisfactory solution effect of the profile derivative vector,increase the error of calculating the profile of the grinding wheel,on the basis of calculating the profile derivative vector using the cumulative chord length parameter spline method,the two-pole point filling method is proposed to solve the problem of the poor calculation effect of the derivative vector at the head and end point of the profile.The SG convolution smoothing filtering method is used to filter and optimize the derivative vector,so as to reduce the interference of the unsmooth curvature of the profile,repair the noise derivative vector and restore the accuracy of the derivative vector,thus improving the accuracy of calculating the grinding wheel profile of the reverse measured profile with mathematical method by using the analytics;Then,the virtual machining simulation is carried out with Vericut software,and a grinding wheel made according to the design data is used to grind a rotor.The simulation results and the grinding results prove that the designing method of the grinding wheel profile is feasible in the actual engineering application.(4)The preprocessing methods of the rotor profile in rotor reverse development are studied,such as the treatment of redundant sections of reverse measured profile,the adjustment of the number of profile points and the adjustment of local density of profile points.At the same time,a rotor variable volume design method based on the equal proportion scaling method of rotor profile coordinates is proposed,the design of compressors with different volume flow is realized with the above methods.(5)The performances of the common system development methods in MATLAB software are analyzed,and the pure code development method with the best stability is selected for the development of the screw rotor reverse design system.This system consists of four modules,namely,the rotor performance analysis module,the grinding wheel profile calculation module for rotor grinding,the rotor profile preprocessing module and the rotor variable volume design module.When the system is developed completely,all the programs in the system are encapsulated with the "Application Compiler" function in MATLAB software,so that this system could run independently in the Windows environment.