Research on partially filled characteristics of vehicular hydrodynamic retarders

Hydrodynamic retarders are widely used on heavy vehicles as auxiliary braking components. Figuring out the partially filled characteristics is of practical significance for the design and control of retarders. In this paper, torque characteristics under variable filling rate of a dual-torus hydrodynamic retarder is studied and verified with experimental data. 1D flow theory was implemented to calculate the circulating flow rate and brake torque. 3D CFD simulation was conducted and VOF model was adopted to simulate air-oil two phase flow when the chamber is partially filled. The results showed that unlike common assumption that brake torque is in direct proportion with filling ratio of the chamber, the torque presents a non-linear relationship vs. filling ratio. In the bench test, filling ratio is derived by monitoring the flow rate into and out from the chamber and the experimental results validated the non-linear relationship between brake torque and filling ratio.