Research on power loss’s principle and reduction optimization of auxiliary braking device—hydraulic retarder

Hydraulic retarder is an auxiliary braking device for heavy commercial vehicles. Although there is no oil in the oil chamber when it is not working, the high-speed rotating rotor still drives and stirs the internal air. This will result in a certain amount of extra power loss. Aerodynamic power loss is related to cavity volume, residual oil and impeller’s structural parameters. The existing methods to suppress power loss need to improve the cavity’s internal structure or add auxiliary mechanisms, which are costly and difficult to implement, and it will affect the normal braking performance. In order to effectively suppress the power loss of hydraulic retarder, we propose a suppression method by applying large stiffness’ spring between stator and rotor, which can suppress the power loss by rapidly expanding the cavity volume. This method has the least modification and does not affect the normal braking performance of working chamber. The calculation model of flow channel has been established with different cavity volumes. The analysis method about three-dimensional flow field is used to research the internal physical field in working chamber’s gas phase at different rotating speeds. We have obtained the internal flow field characteristics, external loss torque and power characteristics of hydraulic retarder. The results based on the comparison of dynamic performance experimental equipment has shown that the spring with large stiffness can rapidly increase the cavity volume and effectively reduce the circular gas flow in working chamber. When the spring stiffness is large enough and the gap is 12 mm, the maximum power loss is 3.79 kW. The maximum loss power is reduced by 65 %. When it is compared with 7.12 kW at low stiffness. So that, the experiments show that the method by applying large stiffness spring in working chamber can significantly suppress power loss. This measure is applied to the structural design of hydraulic retarder, which can reduce the cost of design and manufacturing. Meanwhile, it improves the power utilization rate of vehicle, and does not affect the normal braking characteristics of hydraulic retarder.