Abstract
The rotor and stator blade lean angle of a hydraulic retarder is one of its main geometrical design parameters. The objective of this study is to clarify the effects of blade lean angle on hydraulic retarder performance. In this article, we employ a computational fluid dynamic approach to numerically investigate the fluid flow of a hydraulic retarder for rotor blade lean angles of 35°, 40°, 43°, and 45° in the direction of rotation, where the stator employs an equivalent angle, and all other geometries are held constant. The numerical results of the braking torque were validated against available experimental results. Analyses of torque performance, flow field, and energy loss are conducted in this study. Additionally, the outer loop oil flow rate is used as another indicator of hydraulic retarder heat exchange performance. The results indicate that with increasing blade lean angle, both the braking torque and oil volume flow rate first increase and then decrease, reflecting an optimal value. The lean angle affects secondary vortex flows and separate flows. Relatively large lean angles may enhance the occurrence of separate flow, whereas relatively small lean angles may cause in the oil inlet region. An optimal blade lean angle achieves a smooth oriented inner flow and a maximum braking torque.
Highlights
Hydraulic retarders are widely used in commercial vehicles and buses as auxiliary brake systems
Because the rotor is directly connected to driveshaft, we calculate the torque generated on the rotor as representative of the hydraulic retarder braking torque
This work presented the results of computational fluid dynamics (CFD) research regarding the performance of a hydraulic retarder with different blade lean angles b of 35°, 40°, 43°, and 45°
Summary
Hydraulic retarders are widely used in commercial vehicles and buses as auxiliary brake systems. Hydraulic retarders used in the automotive power transmission systems employ a rotor and stator as the main working components and lubricant oil as the working medium, and the unit is typically mounted on the driveshaft between the transmission and drive axle. The retarder is activated by a pressure control valve that receives signals from electronic control unit (ECU) controller and outputs compressed air of various pressures to control the retarder oil charge and discharge processes. A hydraulic retarder employs a total of five torque shifting positions depending upon the output pressure of the pressure control valve, which includes four fixed torque positions and a speed cruise position. When the retarder is charged with oil, the rotor, which is directly connected to the driveshaft, drives the oil and transfers the kinetic energy of vehicle motion into the kinetic energy of the oil.
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