Measurement And Simulation Of Screw Air Compressor Rotor Profile

Rotors are critical components in screw air compressor.The quality of the rotors is a decisive factor of the quality of screw air compressor.Rotor profile is an important geometric parameter of the rotors.Rotor design mainly means the design of rotor profile.There is a gap between the domestic design level of the rotor and international advanced design level.So it is very important to make measurement of high-performance rotors and reverse design to improve our national rotor design level. In the manufacturing and design field,the measurement of rotor profile is usually done with the coordinate measuring machine (CMM) currently.As rotor surface is a complex three-dimensional surface,how to get high measuring accuracy is always an important issue in the studyTo avoid the contact measurement probe radius compensation problem, non-contact measurement can be used in the three-dimensional curved surface measurement.But the current non-contact measurement accuracy is still not high enough to meet the rotor measurement requirements.The key of contact high-precision 3D coordinate measuring technology is the probe radius compensation technology, which involves the parameters selection, probe compensation algorithm and so on in the measurement.For this problem,the paper described rotor profile coordinate measurement process,discussed the basic principles of the four radius compensation method and made simulations on the influence of the measurement results caused by probe Radius, curve sampling interval and the cross section sampling density.Mainly includes the following:(1)To acquire rotors outline coordinate data, we used contact trigger action and scanning measurements for the actual sampling of the rotor profile; used the filtering method to preprocess the sampled data; used the commercial radius compensation software to do the probe radius compensation and roughly got the discretization profile coordinates of rotors. The actual measured profile will serve as a reference profile for follow-up study to optimize the measurement parameters, and to make precision evaluation of the designed radius compensation algorithm.(2)To get the NURBS curve fitting of rotors profile coordinates, we described the basic principles and methods of the NURBS curve fitting, made some NURBS curve fitting programs, acquired the NURBS curves of the reference profile and the simulated profile and calculated normal vector of the curve.(3)To make simulated measurement and evaluation, we made simulated calculation of center coordinates of the probe head when it is in measurement with the profile coordinates of the reference profile, made the probe radius compensation based on four-point ball method, got the coordinates of the simulated measurement profile and made the NURBS curve fitting of profile coordinates. We made the best match of the simulated measurement NURBS curves and the reference NURBS curves and made the evaluation of rationality of the selected parameters in measurement process and the feasibility of the compensation algorithm.The idea and method of evaluation of measurement accuracy by simulated measuring and data processing provide a valuable reference for the accuracy analysis of the rotors high-precision measurement.