Investigation on current excitation of magnetorheological-fluid-based microbrake for microturbine generator

The microturbine generator performs highly efficiently and reliably in energy conversion. It has been widely used as a physical power source for microminiature flying objects. However, the rotational speed of the microturbine generator may exceed its rated speed when it movesat high speeds. A magnetorheological-fluid-based rotary brake is proposed to reduce the rotational speed of the microturbine generator. The microbrake demonstrates a favorable speed-reduction effect as a series of currents is applied to the coil. Moreover, the current excitation of the magnetorheological-fluid-based microbrake under the wind speed of 28.5-43 m/s is experimentally investigated. The decreasing rate of rotational speed ranges from 27.9 to 38.2%. A hybrid model for the magnetorheological-fluid-based microbrake was developed to explain the speed-reduction mechanism. The current-induced magnetic field distribution in the microbrake is calculated with a COMOSOL Multiphysics-based simulation method. The comparison between calculated curves and experimental results shows that the speed-reduction effect can be explained well by the developed model. The authors believe the proposed model is significant for designing the magnetorheological-fluid-based microbrake, expanding the scope of wind speed for the microturbine generator and promoting the use of magnetorheological fluid in aerospace and energy.