| Hydraulic retarder is an auxiliary braking system for vehicles. Vehicles with Hydraulic retarder system can keep safe when driving on the mountain highway or in complex road conditions.In abroad, many countries have established relevant laws and regulations to make sure that the commercial vehicles must be equipped with auxiliary braking system. In recently years, with the development of laws and regulations in China, relevant regulations have been issued and brought into effect by government. Such as PRC transport industry standards, JTJ/1235-2002"Classification and grading of bus operators". This standard required that high grade 2 of medium passenger cars; high grade1, 2, and 3 of large passenger cars must be installed auxiliary braking system. PRC Ministry of Construction also legislate relevant regulations, such as CJ/T162-2002"Graded Technical Requirements and Configuration", it has been brought into effect in October 1st 2002.Compared with other auxiliary braking systems, Hydraulic retarder owns a lot of advantages:1. Most of hydraulic retarder installed with cooling system and it is applicable to high-speed high-power vehicles.2. It is applicable to long-playing and progression breaking3. The vehicles equipped with hydraulic retarder system can improve the speed of downhill greatly.4. Hydraulic retarder system with great adaptability to roads In China, research and design on hydraulic retarder system has been in the ascendant. Nevertheless we just begun to research on it and it is a new field for us .On the one hand we have not grasp the relevant theory and design methods, So it will lead to a long development cycle, high cost and bad performance. On the other hand, the production of hydraulic retarder is limited and lead to narrow scope of application so it is weak in application and can not put into series production. Based on the development situation of hydraulic retarder system in China, Professor Cheng xiusheng of JLU applied for the high-tech project"Research on Key Technologies for Electronically Controlled Hydraulic Retarder of Vehicle". And this project cooperates with Shanxi Faster Gear Group; the goal is to fill the blanks in this field.Based on the project, the paper made a comprehensive and detailed introduction about basic definition of auxiliary braking system, development course, type classification etc.And this paper introduced the hydraulic ratarder about basic theory, general situation of development, structure, and working process etc.This paper also made some research on modern design strategy for hydraulic retarder. In order to solve the problem of analysis the characteristic of internal flow field. This paper introduced CFD(Computational Fluid Dynamic)simulation methods ,And mainly focus on"Research on Simulation Method for Analysis on 3-Dimension Flow Field of Automotive Hydraulic Retarder",The internal flow field of hydraulic retarder is very complex, in order to analysis the character of flow field in working chamber, This paper introduced serious of simplification and made some assumptions, Using FLUENT software as numerical simulation platform, adopting Three-dimensional flow field theory. For this paper introduced SIMPLE strategy for coupling the pressure between continuity equation and momentum equation, second upwind is induced to accomplish the space discretion, RNG k ?εfor turbulent equations. This paper adopted integrated flow field for numerical simulation and introduced sliding grid theory to simulate unsteady working conditions.After numerical simulation, this paper described the characteristic of flow field by two aspects, Micro perspective(characteristic of internal flow field)and Macro perspective(characteristic of breaking torque).Several conclusions are educed after analysis the internal flow field in different working conditions.1. There two high pressure regions on the pressure surface of the rotor when the rotate speed increased. The one is caused by the impact of flow and another is caused by increased centrifugal force in high rotate speed.2. There are several reasons for the proportional distribution of static pressure on the suction surface: the change of centrifugal force, the change of relative velocity and the effect of viscosity.3. The main impact area located in the cross section between pressure surface of blade and the wing surface .so It is suggested that the round should be added in this area to make sure the flow smoothly .And in order to avoid the off flow and circulation this area should not be designed too straitness.4. The main reason for effecting the flow direction of wing surface is the tilt angle of blade5. The analysis for whole internal flow field show that it is relative regular in a flow cell between rotor and stator, and the hydraulic retarder without inner loop can effectively use the impact of flow field. But compared with the other area, the flow of the inner of the flow cell is much too irregular, there is low pressure region in this area and it is affected by flow field around, this will leads to off flow and decrease in velocity.In the 5th chapter of this paper made a comparison between the simulation results and the test results. Through analysis, it is show that they are in good consistency in characteristic curve of braking torque. So it is proved that the numerical simulation is effective and the simulation results are reliable.After all, there are inevitably remaining some shortcomings in this paper: the model need to refine, the choice of working conditions is not broad and the analysis of internal flow is not enough. In the future more research should be carried out. The work of the dissertation is basics for the future development of the hydraulic retarder system.
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