Study On Electro-Mechanical Coupling Dynamics Of The Shaft System Of Engine-Generator

As the main power source in hybrid devices, engine-genetator system is widely used in hybrid vehicles and hybrid driven construction machineries. The shaft system of engine-genetator withstands the impacts of complex alternating shock loads and strong electromagnetic field at work, so the reliable stability and noise control of hybrid device are affected by vibration problems of the shaft system.In the actual running process of hybrid shaft system, the shaft system of engine-genetator is in the combined effects of gas explosion pressure, inertia incentive and electromagnetic incentive, and electromagnetic parameters, mechanical vibration parameters and gas pressure parameters are mutual coupling systematacially. The change of electromagnetic parameters of generator will affect the change of mechanical vibration parameters of shaft system, while the change of mechanical vibration parameters of system will also affect the change of electromagnetic parameters of system, which is a complex electromechanical coupling relation. In order to study comprehensively on the dynamic performances of shaft system in engine-genetator and analyze the electro-mechanical coupling vibration problem of shaft system, a unified model is needed to be built. The purpose of this study was to research the dynamic characteristics and vibration laws of engine-generator shaft system under the coupling effect of engine and electrical system, which was based on the structural characteristics of shaft system and from the point of view of electro-mechanical coupling, and also to provide a detailed theoretical basis for the design, fault diagnosis, vibration and noise control of shaft system. The main contents included:Using finite element method, the non-linear electro-mechanical coupling dynamic model of engine-generator shaft system was established. Firstly, the shaft system was simplified to the mechanical model of quality continuous distribution along the ladder axis according to the structural characteristics of engine crank shaft system, and the crank shaft unit was built based on the complex of motion differential equations of torsional vibration axis unit and transverse vibration beam unit of crank system. Secondly, according to the electro-mechanical coupling relation that vibration eccentricity exists in generator rotor in actual operation state, the generator air-gap magnetic field energy function was introduced and the generator unit was built. Finally, the dynamic equation of non-linear electro-mechanical coupling of engine-generator shaft system was built by applying finite element method based on the crank shaft unit and generator unit of engine-generator shaft system. The equation providing basis for further study of the intrinsic link between dynamics characteristics of engine-generator shaft system and structural parameters, electromagnetic parameters and gas pressure parameters.Using multiscale method, the coupling mechanism and occurrence resonance condition of the parametric vibration with the forced vibration of engine-generator shaft system were studied deeply. The results showed that, the nonlinear electromagnetic parametric incentive, inertia incentive and gas explosion pressure existed in engine-generator shaft system. The electromagnetic parametric incentive was generated by the change of magnetic field atmosphere when the generator rotor vibrated eccentricly, which was the main cause of parametric excitation vibration. And the coupling phenonmenon of both the parametric vibration and the forced vibration was generated in the combined effects of electromagnetic parametric incentive, inertia incentive and gas explosion pressure.Using multiscale method, the nonlinear dynamic equation of engine-generator shaft system was solved and the linear approximate solution was obtained. A simulation calculation was also performed in a specific instance and the corresponding simulation result was obtained too. Comparing the simulation result with experimental result, it was found that they were basically consistent, which showed that the electro-mechanical coupling dynamic model of shaft system built and the calculation were both accurate and reliable. Using multiscale method, the conditions of primary resonance, subharmonic resonance, superharmonic resonance, combination resonance and multiple resonance of engine-generator shaft system under the actions of electromagnetic incentive, self-inertial incentive and gas external incentive were studied. The subharmonic resonance and primary resonance subjected to the electromagnetic incentive, the superharmonic resonance under the action of inertia incentive, the combination resonance under the actions of inertia incentive with external force, and the multiple resonance under the actions of electromagnetic incentive, self-inertial incentive and gas external incentive and also their motion stability were all studied.In addition, a related experimental research was performed on a hybrid powertrain test bench in Guangxi Yuchai, to verify the correctness of theoretical studies.