Theoretical And Experimental Study On Dynamic Characteristics Of Internal Combustion Generator Rotor With Faults

Internal combustion generator set,as the electric equipment for internal combustion locomotive,contains internal combustion engine,coupling,generator,expansion water tank,hydraulic pump set and other components,with complex structure.In the process of operation,the vibration fault occurs frequently because of the influence of periodic external excitation.It is very important to clarify the vibration characteristics of the complex rotor system of the internal combustion engine set,find and diagnose faults in time and take effective measures.The effect of misfire,coupling misalignment,rub faults on the dynamic characteristics of internal combustion engine set are studied.The paper includes the following contents:(1)The effects of misfire faults on torsional vibration characteristics of internal combustion generator set are studied.By using lumped parameter model,the6-cylinder internal combustion generator is discretized into a 10-DOF torsional dynamic system.According to the system matrix method,the dynamic equation of the crankshaft system of the internal combustion generator set is established.The angular displacement and angular velocity of torsional vibration are obtained directly by principal component elimination method.Considering different rotating speeds and loads,the torsional vibration angular displacements of the free end and the coupling output end with the normal operating condition,single-cylinder misfire condition and two-cylinder misfire condition are calculated respectively.The numerical analysis shows that the misfire condition has a large amplitude on the torsional vibration of the coupling.(2)The theory and experiment of torsional vibration of internal combustion generator set are studied under different degrees of misfire.Based on the actual operating conditions,test rig of diesel engine-coupling-dynamometer is built.The vibration signals of the free end and the coupling output end with different loads are recorded.The dynamic behaviors of the free end angular displacement and coupling output torque are analyzed.It is found that the calculated results are in good agreement with the experimental results.In addition,the validity of using speed sensor and torque sensor to diagnose the characteristics and location of misfire is compared.The experimental results show misfire characteristics are diagnosed by the both sensors,and speed sensor is better than torque sensor for positioning effect.(3)The dynamic equations of the acceleration vibration response of lateral and swing vibration of the flywheel-coupling system are established by the Lagrange equation,and the equations of force and moment caused by angular misalignment during acceleration are derived.The horizontal and swing vibration responses in time domain and frequency domain are adopted to reveal the important dynamical features of the system with angular misalignment or rub faults.The results show that the influence of misalignment and rub impact on the unsteady vibration of the system is obviously different.(4)The effects of the coupling misalignment on the dynamic characteristics of generator rotor system.The equations of motion of the system are deduced by the Lagrange equation.Numerical simulations are carried out using the Runge-Kutta method.The effects of the parallel and angular misalignment on the resonance and super-harmonic resonance of generator rotor system are studied.The parallel and angular misalignment can cause the super-harmonic resonance of the generator rotor system.In addition,the effect of equivalent stiffness on the dynamic response of generator rotor system is analyzed,and the effect of different electromagnetic logarithm on the dynamic response of generator rotor system is studied.(5)Experiment is carried out on the dynamics of the flywheel-coupling rotor system.Based on the actual structure of flywheel-coupling system in the internal combustion generator set,the rotor test bed of flywheel-coupling system is built.The vibration signals of misaligned rotor are recorded on flywheel end and the coupling end.The vibration influence of parallel and angular misalignment on the through critical speed of flywheel end and coupling end is analyzed to compare with numerical results.It is found that the experimental results basically verify the theoretical results,and a new phenomenon of flywheel and coupling vibration is found in the experiment.The effects of resonance and super-harmonic resonance on the system vibration are analyzed.In conclusion,in this paper,the complex rotor system of actual internal combustion generator set is considered.This paper carries out the influence of various fault conditions on the system dynamic characteristics,which is verified by experiments.It provides the theoretical basis and solution method for the follow-up research work of internal combustion generator set,and the results provide solid theoretical guidance for the engineering application.