Research Of Dynamic Characteristics On Rotor System Of Diesel Turbocharger

The turbocharger is a device which can increase engine power, reduce emissions andreduce the fuel consumption without changing the engine size and weight. The basicworking principle of the turbocharger is using the high temperature and high pressureexhaust gas discharged from the cylinder to drive the turbine, so as to drive the compressorimpeller connected to the turbine coaxial. The fresh air sent from the air filter is compressedby the compressor and then sent through the intercooler into the cylinder, thereby increasingthe engine’s intake charge coefficient, as well as air and fuel mixture ratio, thereforeenhancing the power of the internal combustion engine, increasing fuel economy and reduceharmful engine emissions.The turbocharger is one of the important subsystems of the engine, the reliability,stability and service life of its work has a significant impact on the engine. The rotor systemis the core component of the turbocharger, its performance and life expectancy has a directimpact on the operational performance of the turbocharger. The purpose of this paper isstudying the methods of rotor dynamics modeling and analysis on turbocharger, to prove thevalidity of our modeling scheme and the correctness of the analysis results by the method ofcombining simulation and experiment.The main content of this paper include:First, the modal analysis of turbocharger rotor and shells were carried out by using theLMS Test Lab Test System. The modal frequencies of compressor long blades and turbineblades were measured by the method of acoustic test.Second, the turbocharger was divided into shells and rotor system. The finite elementmodel of turbocharger was created by HyperMesh program. Hexahedral and tetrahedral wereused in the finite element model. The modal analysis of all parts of turbocharger was carried out by ANSYS program. The results of calculation were compared with experimental resultsto check the finite element models of turbocharger. The prestressed modal of rotor andconstraint modal of shells were calculated based on the correct finite element model.Third, the test bed of turbocharger was established and the experiments of rotordynamic characteristics were carried out. The orbits of rotor and the vibration of shells weremeasured. The critical speed of the rotor was got through analyzing the waterfall plot andorder1figure.Fourth, the bearings of the turbocharger rotor system were simplified into springs andthe dynamic model of rotor system was established. Campbell diagrams of the rotor fordifferent spring stiffness were calculated. From which we found that the critical speed ofrotor gain in the increase of the bearing stiffness, when the support stiffness increase to acertain extent, the critical speed tends to a value no longer increasing. A transient analysiswas calculated with a simplified model of rotor and the orbits and the curve of the springreaction force were measured.