Research On Rotor Assembly Method Based On Axial Compression

Aircraft engine is called "a crown jewel" in the high-end manufacturing industry.High-pressure compressor is a core part of aircraft engine,the assembly quality of high-pressure compressor rotor directly affectsthe working performance of the aircraft engine.The rotors of high-pressure compressor are assembled through moulds and fastened via bolts.Since there are a lot of bolt holes and the circular contact surface has a large diameter,the assembly quality of flange bolts is not stable.Therefore,it is urgent to develop a new method for aircraft engine bolt assembly to improve rotor assembly quality.This paper aims to improve the assembly quality of rotors of aircraft engine.An axial preloading-based rotor assembly method and an elastic interaction-based bolt tightening method are proposed.An axial load is applied to the upper end surface of the rotor through the assembly process.In this situation,the rotor bolts are fastened in accordance with the tightening sequence of cross parity,which helps to improve the uniformity of the rotor’s stiffness and reduces the deformation on the surface of the rotor.Later,an in-depth study is conducted on the contact surface,axial preloading assembly method and bolt tightening method of the rotors of flange bolts.And,the assembly process is empirically verified.The main research contents include:Firstly,the assembly of rotors of aircraft engine is explored on the basis of flange bolt connection structures.A rotor model is firstly constructed for flange bolt connection structure of aircraft engine,and the influence of rotor’s connection surface contact on the assembly quality of the rotor is analyzed.A microconvex contact model is established for fitting of geometric errors of rotor surface.ANSYS software is adopted to analyze the relations between the layout and quantity of the microconvex and its geometric errors.Secondly,the axial preloading assembly process of the rotor is investigated on the basis of microconvex contact model.According to the influence of connection surface contact on the assembly quality of rotors,an axial preloading assembly process is proposed,and a mechanical model is constructed for bolt fastening units to quantitatively study the relations between axial preloading and bolt pretightening force.On this basis,the mathematical relations between the pretightening force and axial preloading of bolts are explored.Based on the measured run-out tolerance data of rotor connection surface,a microconvex contact model is established;the axial preloading force required by the assembly of rotors is determined through simulation analyses.Thirdly,the tightening process of bolt groups is studied on the basis of elastic interaction.The influences of material property,tightening method and working status on the bolt’s pretightening force are investigated.According to the elastic interaction of bolts,the influences of step-by-step tightening and tightening sequence of bolts on the bolt pretightening uniformity and rotor deformation are dissected through theoretical derivation and simulation analyses.The simulation results show that,when the bolts are tightened in two steps,when 50% targeted pretightening force is applied during each step,the bolt’s pretightening loss will become smaller,and the rotor surface has a smaller deformation.When the bolts are tightened in accordance with the sequence of cross parity,the rotor surface has a smaller deformation.Lastly,the assembly process of flange bolt connection rotors is verified.An axial preloading assembly test stand is manufactured to build a rotor run-out tolerance measuring system and a rotor stiffness uniformity measuring system.The axial pretightening force and the bolt assembly sequence are controlled to test the rotors’ surface run-out tolerance and stiffness uniformity.The test results show that,when 30,000 N axial preloading assembly force is applied,the run-out tolerance of the rotor on the upper end surface reduces by 42.3%,and the run-out tolerance on the bolt connection surface reduces by 7.9%,with an average reduction of strain of 34.2%.When tightening the bolts in accordance with the sequence of cross parity,the run-out tolerance of the rotor on the upper end surface reduces by 32.1%,and the run-out tolerance on the bolt connection surface reduces by 43.6%,with an average reduction of strain of 18.8%.An axial preloading-based rotor assembly method effectively improves rotor assembly quality.