Research on the mechanism of drag reduction and efficiency improvement of hydraulic retarders with bionic non-smooth surface spoilers

Idling power loss suppression techniques of hydraulic retarders in non-braking operating conditions are of great significance to improve vehicle driving efficiency. Most proposed idling power loss suppression devices require auxiliary operating parts, take up a lot of space and increase the load on the vehicle. In this study, the plunger spoiler was optimized with a non-smooth bionic surface for improved performance and compactness. Hydraulic retarders with traditional smooth spoilers and different bionic non-smooth surface spoilers were simulated and tested to investigate the effects of bionic non-smooth surfaces on idling performance. The numerical results indicated that the bionic spoilers could disturb the fluid flow, lower the blade pressure and increase the internal energy dissipation, leading to reduced rotor drag and lower idling power loss. The mechanism of drag reduction on rotor and efficiency improvement was discussed. The experimental data showed that bionic non-smooth surface spoilers reduced idling torque by 11.7% at a rotor speed of 3000 r/min, compared to the traditional smooth surface spoilers. In conclusion, the hydraulic retarder with an optimized bionic surface spoiler is able to reduce idling power loss and improve transmission efficiency effectively.