Whole-flow-passage numerical simulation and experimental validation on idling loss of hydrodynamic retarder

Abstract: A hydraulic retarder is a damper system which inputs mechanical energy, transforms it, and outputs heat. Due to its advantages of brake torque, smooth braking, low noise, long life and compact structure, a hydraulic retarder has been widely applied in heavy vehicles. The research and application on the hydraulic retarder abroad has been carried out earlier, and its technique is more developed. However, since the hydraulic retarder belongs to high-tech products, its high price and the technology blockade of related foreign research institutions makes it only applied to top-grade imported cars in China. At present, the hydrodynamic retarder research of related national enterprises and scientific establishments has just been started, and the level of independent research and development is still low. Therefore, to actively develop hydrodynamic retarder products with proprietary intellectual property rights, and to steadily improve its function has practical meaning for the improvement of the competiveness of the national retarder industry. When a hydraulic retarder is in braking condition, its control system will fill the working chambers of the stator and rotor with a certain amount of oil, which driven by the rotor, will generate a scroll loss effect, thereby producing braking effects on moving vehicles; in its non-braking condition, which is also called idling, the working chambers of the stator and rotor are filled with air, and similar to the braking condition, the air driven by the rotor will also generate a scroll loss effect, which is referred to as an idling loss. As shown in Figure 1, the idling loss rate directly determines the economy of a hydraulic retarder. In order to form a reliable idling loss analysis and calculation method, this paper was based on a certain type of self-developed hydrodynamic retarder prototype. This paper carried out system analysis and drew the technology schematic of idling loss, and then established the calculation model of whole-flow-passage idling loss, carried out whole-flow-passage simulation on an idling loss under 16 rotor speed conditions with the application of CFD technology, and finally proceeded with idling loss measurements with the combined bench test method which can eliminate mechanical friction loss. With the results compared and analyzed, the result of the whole-flow-passage simulation is found to be in agreement with that of the bench test, and the relative error is within 11.8%, a relatively high accuracy. Therefore, this paper proves the reliability of the whole-flow-passage simulation calculation method, and provides a reliable calculation method for the further study of the hydraulic retarder idling loss reduction.