| The screw rotor is the core part of screw machinery such as pump,screw compressor,screw vacuum pump,screw expander and its design and processing precision determine the comprehensive performance of the screw mechanical system.In particular,the screw pump,as a positive displacement pump,is widely used in petroleum,chemical industry,ships,ocean drilling platform,aerospace,machine tool equipment,engineering machinery,environmental protection,energy,food,pharmaceutical,and many other fields due to its simple structure,high volumetric efficiency,small flow pulsation,low noise,easy maintenance and excellent performance in single-phase or multiphase operation.With the development of modern industrial technology,the application range and field of screw pumps have become more and more extensive,and have become the key basic and core components of many high-end equipment.However,as the working conditions of screw pump become more and more complicated,the demands of design and manufacturing in the accuracy of screw pump are increasingly higher.In the past 30 years,domestic and foreign scholars have conducted continuous and in-depth research on the optimization design of screw pump rotor profile,machining technology and pump cavity flow field characteristics from all over the world.However,due to the complexity of the screw rotor profile of the core components of the screw pump,its design and manufacturing accuracy has always been a bottleneck that limits the performance of the screw pump system.At present,the research on screw rotor mainly focuses on the optimization design of rotor profile and the design method of forming tool.Therefore,screw rotor processing quality is not high,which restricts the large-scale application and popularization of high performance screw pump.In this paper,the optimization design and precision forming technology of the cycloidal screw pump rotor are taken as research objects.Numerical analysis,space meshing principle and envelope theory,forming grinding principle etc.are used as research tools.Screw rotor meshing clearance design method,forming tool optimization design method,forming grinding error compensation,screw profile roughness control and detection technology are being studied in depth.The main work of this paper is as follows:(1)On the basis of the study of the generation principle of cycloid,the author designs the tooth profile of two-screw pump and three-screw pump with cycloid.Since modern computer technology is commonly used in the design and manufacturing of screw rotors,a curvature adaptive encryption/sparse picking method is proposed for tooth profile data optimization design in order to improve the accuracy and efficiency of computer calculation.The spatial analytic geometry knowledge is used to compare and analyze the different meshing clearance design methods of the screw rotor.The influence of different clearance values on the volumetric efficiency of the cycloidal two-screw pump is compared by computer CFD numerical simulation.The screw pump is meshed designed according to the actual working conditions.A set of screw rotor tooth profile optimization design methods for manufacturability and adaptability is formed.(2)The transformation relationship between the screw profile coordinate system and the forming tool coordinate system in the screw rotor forming process is studied.Based on the theory of space meshing and envelopment theory,the tool profile of screw rotor forming tool based on discrete point data is solved by cubic spline interpolation method.A method for evaluating screw profile error is proposed,and the range of mounting parameters of screw rotor forming tools is obtained under the condition of noninterference and non-cutting according to the spatial contact characteristics of the screw rotor and the forming tools.The profile characteristics and machining characteristics of forming tools under different installation parameters were systematically compared,and the secondary optimization design of forming tool installation parameters was realized.In view of the characteristics of complex screw rotor profile and high difficulty in design and processing,based on the above research,a set of visualization software was developed based on MATLAB GUI,which can be used for screw rotor profile data preprocessing,meshing clearance design,forming tool design,forming simulation processing and error evaluation.(3)The wear mechanism of the forming grinding wheel is studied.The influence of the installation center distance,the installation angle and the wear of the grinding wheel on the screw profile error is revealed by the screw rotor forming simulation processing.A parameter adjustment method was proposed innovatively.The method realizes the compensation of the profile error caused by the wear of the grinding wheel,and verifies the feasibility and correctness of the proposed error compensation method through simulation processing.Aiming at the complexity of the grinding mechanism of the screw rotor,the removal mechanism of the grinding surface of the screw surface was studied by establishing the abrasive grain distribution model of the forming wheel surface,and the predictive modeling of maximum undeformed chip thicknesss of the screw profile grinding was established.It provided a basis for the study of grinding force,grinding temperature and grinding power.The mechanism of screw rotor forming grinding is studied in depth,and the screw profile grinding roughness prediction model of the finishing grinding stage was established for the first time.It overcomes the technical difficulty that the traditional grinding roughness prediction model is unable to predict the grinding roughness in the plowing grinding stage and provides theoretical guidance for improving the surface roughness of screw rotor forming grinding.(4)The precision forming of the screw rotor is inseparable from the high-precision detection technology,and the detection accuracy largely determines the improvement of the precision of the screw rotor.In practice,the screw rotor profile is complicated,the measurement standard is not clear,and the precision detection is hard.On the basis of studying the working characteristics of the screw pump and the geometry of the screw rotor profile,the error term of the screw profile detection is proposed.A new method for three-dimensional characterization of screw profile by two-dimensional section measurement of gear measurement center was proposed.It overcomes the technical problem that the universal testing equipment can not realize the accurate detection of the screw rotor.It is of great significance for improving the screw rotor detection efficiency,reducing the testing cost and improving the screw rotor machining accuracy.Finally,a series of experiments were designed to verify the research in this paper.The experimental results are in good agreement with the theoretical research. |
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