Curved M–shaped runner-incorporated thermal design for magnetorheological micro-brake

The magnetorheological (MR) micro-actuator is a key component for improving the performance of miniature mechatronic systems. However, the high-speed long-term service of MR micro-actuator is impeded owing to the complex thermal coupling of heat sources in the microspace. Here, we propose a curved M–shaped cooling runner to increase the heat dissipation capability of MR micro-brake in a miniature turbine generator. The runner is integrated into the inner cylinder of a micro-brake to reduce the coupling effect between the viscous friction heat of MR fluid and Joule heat of the magnet-exciting coil. The cooling mechanism of MR micro-brake is revealed by constructing a heat dissipation model under Multiphysics coupling. Experimental results showed that the temperature of the MR fluid in the micro-brake is decreased from 113.8 to 33.9 °C with a cooling flow rate of 1.41 cm/s. The braking torque performance of the micro-brake is recovered to 92.2 % of its value at room temperature (25 °C). The torque recovery capability ratio Δ_TTR increases more than 400 %. Furthermore, we found that the torque response time of MR micro-brake can be even reduced by 27.3 %. We believe this work is significant for promoting the long-term applications of MR micro-actuator in miniature turbine generators used for long-range rocket projectiles.