Effect of Stator Surface Area on Braking Torque and Wall Heat Dissipation of Magnetorheological Fluid Retarder 2020-01-0937

Magnetorheological fluid (MRF) is used as the transmission medium of the hydraulic retarder. The rheological properties are regulated by changing the magnetic field to achieve accurate control of the retarder's braking torque. Under the action of the external magnetic field, the flow structure and performance of the MRF retarder will be changed in a short time. The apparent viscosity coefficient increases by several orders of magnitude, the fluidity deteriorates and the heat generated by the brake cannot be transferred through the liquid circulation, which will affect the braking torque of the retarder. Changing the surface area of the stator also has an influence on the braking torque of the retarder and the wall heat dissipation. In this study, the relationship between the braking torque of the MRF retarder and the stator surface area of the retarder was analyzed. In addition, phase change materials were used to directly dissipate heat on the retarder surface to improve the heat dissipation rate of retarder and improve the stability of the retarder's braking torque. In order to study the effect of stator radius on braking torque of MRF retarder under an external magnetic field, a braking torque model was established based on MRF with Bingham model properties, and a heat transfer model of wall phase change material was established to analyze the relationship between heat transfer and braking torque of MRF retarder. The results show that the braking torque of the MRF retarder increases rapidly with the increase of the radius outside the effective working area of MRF, which increases faster at high speed and increases the stator wall surface heat dissipation, but the rate of heat dissipation increases relatively slowly. The wall surface with a heat pipe can take away the heat generated by the retarder and cool the retarder. Under the appropriate stator surface conditions, phase change materials are used on the wall surface of the retarder to dissipate heat, which improves the stability of the braking torque of the retarder and promotes the development of MRF retarder to high power.