# Analysis on Flow and Temperature Field of High-Power Magnetorheological Fluid Transmission Device
## 1 Introduction  
Magnorheological (MR) fluid is a novel type of intelligent material [1; 2; 3]. MR fluid is composed of soft magnetic particles, carrier fluid and additives [4; 5; 6; 7]. The rheological effect of MR fluid is that it can flow freely without a magnetic field. Under the action of a magnetic field, MR fluid is solidified and can transfer a certain shear force [8; 9; 10; 11]. MR fluid is characterized by a fast response, simple control and strong anti-interference ability [12; 13; 14; 15]. MR transmission technology with MR fluid as a working medium has broad application prospects in the soft start, soft brake and step-less speed regulation of mechanical equipment [16; 17; 18; 19]. An MR transmission device will generate a lot of heat due to wall slip during operation, resulting in the fact that its maximum transmission power is usually restricted by heat dissipating performance. Scholars have carried out a lot of research to investigate the effect of temperature on the transmission characteristics of MR devices and improve the heat dissipation performance of the MR transmission devices. [PERSON] et al. [20] found that when the temperature increases from \(-40\)\({}^{\circ}\)C to \(150\)\({}^{\circ}\)C, the dynamic yield stress and viscosity resistance of MR fluids decrease by 10% and 95%, respectively. [PERSON] et al. [21] established a thermal analysis model of MR Damper, and tested the relationship between temperature and damping force. Results show that the damping force decreases sharply with the increase in temperature. Through experimental studies, [PERSON] et al. [22] found that the increase in temperature had a negative impact on the durability of MR fluids, which would lead to significant attenuation of transmission torque. [PERSON] et al. [23] proposed a multidisk MR fluid actuator. Simulation and experiment results show that the temperature of MR fluid increases linearly with the time in the slip and loaded states, and the greater the slip power is, the faster the temperature rises. [PERSON] et al. [24] studied the influence of temperature on the properties of MR fluid, and the experiment showed that shear yield stress decreased with the increase in temperature. [PERSON] et al. [25] investigated the effect of temperature on the torque transmission characteristics of an MR experimentally. Results show that compared to 20 \({}^{\circ}\)C, the transmitted torque was reduced by about 20% at 80 \({}^{\circ}\)C. [PERSON] et al. [26] investigated the influence of temperature on the stability of torque transmission by MR fluid. [PERSON] et al. [27] formulated a theoretical model for slip differential heat between two neighboring particles of MRFs in shear and squeeze modes. The proposed model can satisfactorily describe the main micro-characteristics of the slip differential heat of MRFs in shear and squeeze modes. [PERSON] et al. [28] investigated the temperature effect of MR fluid on performance while the damper is working. Results show that the saturation magnetization of the particles was reduced by 57% at higher temperatures (127 \({}^{\circ}\)C). [PERSON] et al. [29] analyzed the heating and cooling mechanism of an MR clutch and proposed an auxiliary clutch cooling liquid cooling method. The results show that the increase in temperature leads to the decrease in viscous torque and total output torque. [PERSON] et al. [30] put forward the method of internal circulation cooling. The coolant can rotate with the rotating sleeve, and the coolant can further flow into the brake near the MR fluid, thereby achieving an improved cooling effect. [PERSON] et al. [31] chose to add an aluminum foil bubble insulation material with a low thermal conductivity in the cavity between the electromagnetic coil and the MRF to avoid rapid temperature rise. Results show that the rate of increase in the MRF temperature in the working area of the damper with the insulation material could be reduced by 57.4%.