Simulation On The Performance Of Hydraulic Retarder Fully Filled With Oil Based On SPH Method

Hydraulic retarder is more widely used in high power vehicles as a kind of auxiliary braking device.Fully grasping its internal flow field characteristics and braking torque performance is the key to dsdign and optimize the hydraulic retarder.Compared with the time-consuming and laborious theoretical calculation and experimental methods,numerical simulation technology has unique advantages.By means of the study on the smoothed particle hydrodynamics(Smoothed Particle Hydrodynamics: SPH),a meshless algorithm,and with the advantages in the simulation of liquid flow and explicit solution,the motion and performance simulation of the hydraulic retarder are carried out,which provides a new method for mastering and improving the performance of hydraulic retarder.The main contents are as follows:Based on the characteristics of the flow field of the hydraulic retarder,a mathematical model is established.The Lagrange form of the Navier-Stokes control equation is derived and discretized by the SPH approximation theory.Taking HR355 d dual torus hydraulic retarder as the research object and with the help of the explicit finite element analysis software,the SPH model of the hydraulic retarder fully filled with oil is established.In this model,the driving wheel and the fixed wheels are represented by the rigid body,the working fluid is described by the SPH particles and the interaction between oil and impeller is controlled by the contact collision algorithm based on SPH.The processing method of the whole passageway and the complete modeling procedure are summarized.Considering the characteristics of the hydraulic retarder,such as closed-form wheel cavity,complex boundary and the great difference of the properties between the impeller and the oil,the important data needed during the simulation is confirmed to ensure the reality and validity of the model.The density of the oil,the state equation of the material and the rotary inertia of the driving wheel are included.In order to improve the computational efficiency,the tree-like searching method is used to search the interacting SPH particles in each time step.The contact force between the SPH particles and impeller is controlled by symmetric penalty function and in this way,the penetration of SPH particles is reduced.The value of keyword such as SLSFAC,SFS,SFM,FS and FD are demonstrated.After the validation simulation under n=1000r/ min,it is concluded that the simulation results of the braking moment under steady state is reliable and the braking ability under dynamic state can be theoretically simulated.The simulation results of SPH method under the condition of several rotation speed are compared with the results obtained by CFD method and experiment.In conclusion,the SPH method can well simulate the flow of oil in the hydraulic retarder.At the same time,the braking moment under steady state is relatively accurate and the error under is less than 10%.What is more,the braking moment under dynamic state has the same trend as the experiment results.