基于剪切-挤压模式的磁流变制动器流动与传动性能分析

Analysis of the Flow and Transmission Performance of Magnetorheological Brakes Based on Shear-Squeeze Mode

针对现有加压式磁流变制动器结构复杂的问题,提出一种利用楔形间隙自挤压强化的盘式磁流变液制动器。此制动器通过在转子壁面上布置4个矩形槽的结构,利用矩形槽与圆盘面之间的间隙产生的挤压力对磁流变液进行挤压,使它在提高工作性能的同时,结构更加紧凑。基于有限单元法对磁场进行分析,得出不同电流下磁流变液的磁学与力学性能;基于计算流体动力学对磁流变液进行流场分析,得到挤压应力沿周向分布的云图;基于Navier-Stokes方程和挤压强化模型,推导出磁流变液的流动方程,并得到制动器产生的转矩与电流、液体挤压应力的关系。结果表明:楔形间隙使得液体挤压应力产生周期性的变化,磁流变液在挤压强化后,剪切屈服应力显著增加,当输入电流为2.0 A时,磁流变液剪切屈服应力最大值为67.7 kPa,制动转矩为24.8 N·m,相较于未挤压状态,制动转矩提升了约46.2%。

Aiming at the complex structure of the existing squeezed magnetorheological brakes,a disc-type magnetorheological brake strengthened by self-squeezing using wedge gaps was proposed.Four rectangular slots were evenly distributed on the rotor wall surface of this brake,and the squeezed pressure generated by the gap variation between rectangular slots and disc surface squeezed the magnetorheological fluid,which made the brake more compact while improving its working performance.The magnetic field was analyzed based on the finite element method,the magnetic and mechanical properties of the magnetorheological fluid under different currents were obtained.Then,on the basis of computational fluid dynamics,the flow field analysis of the magnetorheological fluid was carried out,and the cloud maps of squeezing stress distribution along the circumferential direction were obtained.Finally,the flow equation of magnetorheological fluid was derived based on the Navier-Stokes equation and the squeeze strengthening model,and the relationship between the torque,current and squeezing stress was established.The results show that the wedge gap causes the periodic change of fluid squeezing stress,and the shear yield stress of magnetorheological fluid increases significantly after squeeze strengthening.When the input current is 2.0 A,the maximum shear yield stress is 67.7 kPa and the torque is 24.8 N·m,which is about 46.2%higher compared with the un-squeezed state.