Study On Carbon Particle Deposition Characteristicsof Turbocharger Turbine Blades And Rotor Unbalance Vibration Response

Due to the operation requirements,the turbocharger is often under variable conditions such as idle speed and rapid acceleration during the running process,which can easily cause a phenomenon that the colloidal carbon particles produced because of incomplete combustion of fuel oil deposit on the surface of turbine blade.The complicatedness of the turbocharger rotor system’s operation conditions will make the deposited carbon particles fall off during the running process.The carbon particles that fall off will cause the rotor to be unbalanced and then cause strong vibration with the particles constantly accumulate and evolve.With a certain type of turbocharger rotor system being an example,the finite element model of the rotor system is established,and the correctness of the finite element model and modeling method is verified through the combination of finite element simulation and experiment.The mechanism of particle deposition on turbine blades under the dynamic behavior of gas-solid two-phase flow is analyzed.The positions of particle deposition under different rotor speeds and particle diameters are studied,and its rationality is verified through experiments.The carbon particle deposition amount is equivalent to the unbalance size and added to the turbine end of turbocharger to explore the influence law of the unbalance size on the vibration response of rotor system.The main content is as follows:(1)The structure of the turbocharger is analyzed and the turbocharger rotor system dynamics equation is derived.Besides,the finite element model of the turbocharger rotor system is established combined with actual relevant parameters and the critical speed and vibration mode in the experiment are compared with those in the simulation to verify the correctness of the finite element model and modeling method.(2)The formation mechanism of non-uniform carbon deposition on turbine blades under gas-solid two-phase flow is analyzed,and the finite element model of turbine blade deposition is constructed.Reynold average Navier-Stokes equations are adopted to solve the gas phase governing equation and Euler-Lagrange governing equation is used to figure out the particle motion.The distribution of deposited carbon particles on turbocharger blades is analyzed when the turbocharger rotates at different speeds,and the distribution law is verified by the experiment of particle deposition on turbocharger blades.The results show that the carbon particles are mainly deposited on the pressure surface of turbine blades,and the position of carbon deposition will change with the change of rotating speed.With the increase of rotating speed,particle deposition mainly occurs at the root of the blade.With the increase of particle size,particle deposition mainly occurs in the middle of turbine blade near the leading edge of blade.(3)Aiming at the complex problem of vibration response of unbalance fault of turbocharger rotor system under particle shedding,the influence law of unbalance size and phase difference combination on vibration response of rotating subsystem is explored.It is found that the larger the unbalance is,the smaller the vibration response is,and the more obvious the critical speed drift is.With the increase of the unbalanced phase combination angle,the vibration amplitude of the rotor increases first and then decreases before crossing the first critical speed point,and decreases gradually after crossing the critical speed,and the final amplitude tends to be about 0.001 mm.