| A double circular arc gear drive has the characteristics of higher carrying capacity and longer life than an involute gear drive, which is widely used in the petroleum, chemistry, mining, metallurgy industries. In a newly down-hole driven twin-screw pump, the double circular arc gears, which make the twin-screws run simultaneously and realize power split, are the key components in determining the working capacity of a pump. Meanwhile, better design requirements about higher working capacity of a double circular arc gear are needed under such abnormal working conditions as the setting depth of the pump beyond 1200m, the submergence depth over 500m that immersed a twin-screw pump in the crude oil, the temperature of the bottom of a well above 80℃, 30 months of uninterrupted work, full of lubricant in the synchronous gear box, a rapid power system at a speed of 3000r/min, 45 kW of transfer power, a body diameter of the pump less than 140mm, the lubricant unable to replace or renew, the space too small to disperse the heat, etc.This thesis lays emphasis on the following points:(1) The tooth profile equations of a double circular arc gear before the running-in are analyzed, and the contact computation models with finite elements under the static status and the dynamic status are set up. Moreover, the contact strength and the bending strength of the double circular arc gears are calculated, and the bending stress is tested to verify the contact model.(2) The fundamental about the running-in simulation of a double circular arc gear is studied, and its model is set up on the basis of ANSYS contact arithmetic. Furthermore, the running-in simulation of a pair of double circular arc gears has been realized to predict the effect of the running-in method, and the simulation results have been compared with the computation results before running-in.(3) By dividing different heat nodes and meshes, the heat net equation is determined. The computation models of power loss, heat resistance and heat convection with the lubrication are discussed, and heat convection coefficients of different parts are presented. Furthermore, the temperature of all nodes under the different lubricating conditions and the thermal deformation of the friction parts, such as bearings and gears, are calculated. (4) The computation models of power loss and heat convection of key parts, such as bearings and gears, without any lubrication, are established, and the transient computation model of the drive is determined. In addition, the distribution and changing rule of the temperature of the system are investigated, and the thermal deformations of a friction pair of parts are calculated.(5) Based on the thermo-elastic coupling theory and ANSYS, the coupling deformation and the stress of a double circular arc gear in the thermo-elastic coupling field, before and after the running-in, are computed. By the discrete interference inspection arithmetic, the moving interference inspection of the double circular arc gears after deformation is carried out, and the best backlash is presented.(6) To demonstrate the real working condition of the twin-screw pump, and on the basis of the computation results of thermo-elastic coupling, the full life history of loading spectrum is compiled, the prediction of the fatigue life of the double circular arc gear is implemented, and its life is compared with that of the involute gear drive at the same size.The major innovative points and results are as follows:1. Based on the theories of gear geometry, gear tooth contact analysis, tribology, heat transmission and fatigue life analysis, and combined with the methods of finite elements, heat net, collision interference inspection and rain flow counting, a new method on studying the working capacity of a double circular arc gear under abnormal working condition is put forward by taking contact strengths and deformations before and after running-in, and fatigue life after running-in, of a double circular arc gear under thermo-elastic coupling status as the evaluation parameters of working capacity.2. The factors of influenced modeling, boundary conditions and the method of load processing are analyzed, and the contact model of a flexible gear to analyze the dynamic contact stress of a double circular arc gear is established on the basis of the flexible rim and ANSYS/LS-DYNA.3. On the idea of a numerical tooth flank and utilized APDL of ANSYS, the running-in contact simulation model of a double circular arc gear is constructed, the contact stress distribution after running-in is obtained by the simulation of running-in course.4. Based on the thermo-elastic mechanics and the discrete collision interference arithmetic, the moving interference inspection model of a double circular arc gears under thermo-elastic coupling status is presented, and a moving interference inspection is carried out, which is served as a theoretical basis to the dynamic design of a gear.5. To change the rated condition of a submersible electric motor into the working condition of a twin-screw and utilize the rain flow counting method, the random load data of double circular arc gear are processed The full life history of loading spectrum is compiled, and the fatigue life of double circular arc gear drive under abnormal working condition has been predicted.
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