Research On Vibration Of Engine Cool Fan Based On Air-Structure Coupling

Engine cooling fan, due to the air-coupling and high-speed rotation, will bring aboutthe effect of air pressure and rotating pre-stress. In order to get the dynamic characteristicsof fan accurately, the two factors above must be considered at the same time. Because it isdifficult to experiment, in this paper we choose the simulation method to research.FSI (Fluid-Structure Interaction) includes CSD (Computational Structure Dynamics),CFD (Computational Fluid Dynamics) and the coupling analysis. By experiment andsimulation methods, on the base of a commercial vehicle cooling fan, we create thestructural model of the fan and the air-flow field model. Then combine both the numericalsimulation after test verification; finally, this paper analyzes the dynamic characteristicsunder coupling condition.In CSD stage, we have done modal analysis of the fan. In the modal Experiments,establish wireframe model of the fan using local coordinate system methods.and obtain thefree modal with Polymax identification method. In the modal Simulation, this papercompares the fan-modal simulation results from LMS Virtual.lab with the experimentalresults. And verify the CSD simulated model.In CFD stage, use Fluent established CFD model. According to the actual case of theaerodynamic performance test, the middle of the fan model needs to be trimmed. Finally,through the fan aerodynamic performance test, the air-field CFD model has been verified.In FSI stage, first import the air-pressure of fan blade into structural model in LMSVirtual.lab, and load the rotating load condition. Then use numerical simulation to get thestress, deformation, fan modal dynamic characteristics, etc. The simulation results showthat it causes the phenomenon of stiffness hardening, due to the coupling air-force and therotating pre-stress. There is a certain degree of increase in each modal frequency. the3rdorder modal, which deformation is axial movement, has changed into the1st order afterFSI coupling, meanwhile, the frequency increased from108.8Hz to112.6Hz; At the sametime, the1st and2nd order modal frequency, which deformation is bending, were up by23Hz and2Hz. moreover, The maximum deformation position and vibrate direction of eachmodal order are not changed.