Study On Waste Heat Recovery System For Hydraulic Retarder Based On Organic Rankine Cycle

The hydraulic retarder is an auxiliary braking device used in heavy duty vehicle.It generates braking force by liquid damping effect and makes inertial energy into thermal energy of the transmission medium when the vehicle is in the downhill.The traditional cooling system of the hydraulic retarder dissipates the heat of transmission medium out of the vehicle directly,which causes a big waste of energy,meanwhile the thermal management system components need to consume engine power.This thesis applies organic Rankine cycle(ORC)waste heat recovery system to replace the hydraulic retarder cooling system,which could meet the high power cooling requirements of the hydraulic retarder and recover waste heat energy from the transmission medium at the same time and then supply energy to the thermal management system,which could save the parasitic power of the engine and reduce vehicle energy consumption.This study mainly research on the design of the waste heat recovery system,the selecting of the Rankine medium,the temperature control of hydraulic retarder by waste heat recovery system and the energy analysis of the waste heat recovery system.The prototype test bench is built to verify the feasibility of the temperature control of the waste heat recovery system and the validity of the simulation model.Aiming at the temperature control of hydraulic retarder,this thesis puts forward two kinds of temperature control scheme.In scheme one,the evaporation pressure remains constant and the evaporation pressure change in scheme two.Firstly,the hydraulic retarder heat generation model,the ORC thermodynamic model and the evaporator heat transfer model are established.Then,by matching calculation the heat transfer area of the evaporator is 18m~2 and the oil temperature in the entrance of the retarder is 85℃.When choose the scheme one,the temperature range of the hydraulic retarder transmission oil is 72.68~119.05℃.When choose the scheme two,the transmission oil inlet temperature in retarder is controlled at 85℃and the outlet temperature of the transmission oil is below 120℃.Based on the ORC energy recovery model and the system energy consumption model,the waste heat recovery and energy consumption characteristics of two kinds of temperature control schemes are obtained.Compared the output power and the consumed power,it can be found that the system could meet the energy self-sufficiency in all conditions of the hydraulic retarder.Two kinds of temperature control schemes are comprehensively evaluated from the following aspects:temperature control effect,waste heat energy recovery and parameter adjustment,and finally the scheme two is chosen as the system temperature control scheme.The hydraulic retarder waste heat recovery system prototype test bench is built,and the preliminary experiment is carried out.The results show that the outlet temperature of the transmission oil can be controlled at about 85℃by the scheme two,which could demonstrated the feasibility of the scheme two.Comparing the test results with the simulation results,the reasons for the deviation between the two results are analyzed,and the validity of the simulation model is verified.