Model Reduction And Prediction Of The Flow Field In Dual Torus Hydrodynamic Retarder

High cost of numerical simulation and insufficient data mining of flow field are the problems restricting the design of the hydrodynamic retarder which is a kind of auxiliary braking component widely used in high power vehicles.This paper aims to fully exploit the characteristics of the internal flow field,pick out the law of the fluid motion and build the models between the input parameters and the output parameters which include both the internal flow field and the braking performance.The paper lays the foundation of the braking performance promotion and design efficiency improvement of the retarder's control system.The main contents of this paper are as follows:Firstly,the numerical model of the dual torus hydraulic retarder based on its structure features was constructed.The full-filled conditions at different rotating speeds were simulated and verified by the experiment results.And then,the steady flow features of the dual torus hydraulic retarder were summarized.At last,the inclining and azimuth balde angles of the retarder were optimized based on the features of the dual torus retarder.It can be concluded that the inner circulation velocity of the oil is higher,the vortex intensity near the suction surface is increased and the braking torque is promoted by more than 58%.Secondly,the transient simulations where the sliding mesh technology was applied were performed at different speeds of hydrodynamic retarder based on CFD technique.And the snapshot technique and the Proper Orthogonal Decomposition(POD)method were applied to internal fluid domain transient simulation results to obtain the flow modes containing different energies.The flow modes got under different sampling frequencies of snapshots and different speeds of the rotor were compared and it can be concluded that the sampling frequency has great influence on the energy of the flow modes which are immune to the rotation speeds of the rotor.The flow fields were reconstructed by different number of flow modes while the coefficients characterisctics of different flow modes were analyzed with Fast Fourier Transform.The results showed that the coefficients of the energetic flow structures were sinusoidal variation with time and the adjacent coefficients had almost the same amplitude and frequency while the phases difference of them were 90 degrees.The error between the original flow field and the reconstructed flow field was affected both by the number of used basic flow structures and the target of reconstruction.Thirdly,a kind of method combining surrogate model and the proper orthogonal decomposition technique was proposed to predict both the flow field and the braking performance.The pressure on both the suction surface and the pressure surface of the rotor balde was extracted based on the CFD-Post and the method of POD was applied to the extracted results to capture the energetic flow structures.The surrogate model between the rotor speeds and the coeffients of the basic flow structures were builded based on the methods of both Kriging and RBF.Both the flow field and the torque of the hydrodynamic retarder at different speeds were predicted to verify the accuracy of the model and the results showed that the model was reasonable in the prediction of the flow field.