Study Of Exaust Gas Recirculation Electrical Control Cooling System On Diesel Engine

In order to reduce the NO_x's emission of the diesel engine and meet the strict emission regulations, an EGR electrical control cooling system was designed. The system can adjust EGR cooling temperature automatically under different operation conditions of diesel engine. At the optimum cooling temperature, the engine can have the better performance and the lower NO_x emission. The EGR electrical control cooling system as a branch of the engine cooling system, heat is taken out by cooling water which comes from cooling system of engine across EGR cooler, then dissipated by cooling fan of the engine. The cooling water is drived by electrical water pump. According to the signals taken from sensors, ECU can control the rotate speed of water pump to change the water circulation so that various EGR cooling temperatures are achieved automatically. EGR temperature is controlled accurately so that the quantity of NO_x in the exaust gas is reduced and the emission regulations is met.The main parts of EGR electrical control cooling system was designed. Based on the heat transfer theory, the EGR cooler was designed. Based on the principle of Hydromechanics, Venturi pipe was designed. The electrical water pump's type was selected and the EGR cooling control system were designed. In order to design the hardware and the software of the ECU, an experiment was done on a R4105T diesel engine test platform. When R4105T diesel engine operated under different operation conditions, the influence rule of EGR cooling temperature on NO_x, HC, CO, smoke emission and oil consumption were studied. The optimum EGR cooling temperature range was concluded under different operational conditions. Firstly, according to the signals taken from sensors, ECU obtain the operation condition's optimum EGR cooling temperature through searching the table. Then ECU compared the actual EGR temperature with the optimum temperature. If the actual value is not equal to the optimum value, ECU adjust the electrical water pump's average voltage to control water pump's rotate speed through changing PWM signals'duty cycle. Through changing cooling water's circulation EGR cooling temperature is controlled automatically and EGR optimum temperature is achieved.The result of the test showed that the EGR electrical control cooling system can control the diesel EGR cooling temperature automatically and make the EGR achieve the optimum temperatue range under different operation conditions. The automatic extent is improved and the emission of the NO_x is reduced.