| The hydraulic retarder is an important auxiliary brake system for vehicle,which widely applied in heavy commercial vehicle.And the hydraulic retarder,which plays a significant role in driving safety,has advantages of huge power density for braking,well performance for high-speed braking and heat radiating.However,whether the retarder is installed in parallel or serial connection with the transmission system,the air-frcition which forms for the air stirring in the retarder will reduce the transmission efficiency of transmission system when the vehicle drives in non-brake condition.In a certain extent,the air-friction loss will increase the fuel consumption and exhaust emissions of the engine.This thesis starts from the realistic significance of “Energy Conservation and Emission Reduction”.As the study clue of the air-friction of hydraulic retarder,analysis of characteristics and the air-friction system design are determined as the foundation and technology realization of this thesis.The feasibility of principle for this system is verified by the prototype test.The main contributions of this thesis are as follows:The reasons for the air-friction are described form the aspects of engineering and theory.As the view of fluid loss analysis,the one dimensional calculation model for the air-friction is built.The computational fluid dynamics method is taken to calculate the internal flowing of the retarder,the 3D flow model is established,and the appropriate solution is determined.The comprehensive analysis of this research method combined with the external and internal characteristics of air-friction is adopted,and relationships between the medium density and air-friction are verified through this one dimensional model.The characteristics of internal flow distributions are revealed in different conditions.The influence of the medium density to the demonstration the external performance of fluid is manifested.Based on the characteristics of air-friction,the friction reduction scheme is confirmed,and the air-friction reduction system of hydraulic retarder is designed.From two aspects of braking and non-braking state,the performance of braking and friction reduction of this hydraulic retarder with low air-friction is explained.And the feasibility of principle for this system is demonstrated by the prototype test.A vehicle model equipped with this retarder which has low air-friction is established,and the specific driving cycle is designed to evaluate the economy performance.The results show,this friction reduction system of hydraulic retarder make the performance of fuel economy with a upgrade to 1.90%.The innovations of this thesis are as follow:The schemes for air-friction reduction of hydraulic retarder which are carried out by vacuum pumping and the replacement of light gas is proposed,and the air-friction reduction system is designed,which reduce the air-friction with good performace of braking.The vehicle model equipped with hydraulic retarder which considers the gas control and mechanical transmission by co-simulation AMESim/Simulink,the performance of “Energy Conservation and Emission Reduction” can be evaluated by this comprehensive model. |
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