Study on Thermal Management System for SCR on Hybrid Electric Buses

According to the problems that the dropping of SCR catalyst temperature lead to increasing the NOx emissions on the conditions of DFCO (deceleration fuel cut off) and autostop while hybrid electric buses in operation, this paper developed the thermal management system for SCR. The system consists chiefly of cylindrical electric blinds, two-position and three-port solenoid valve, electronic control unit, drive mechanism and other components. The thin layer heat-resistant insulating coating was applied to improve the thermal insulation effect of the blinds. The electronic control unit of the system collects the data from exhaust temperature transducers, and then estimates SCR catalyst temperature. When the temperature drops or rises to a certain value, the drive mechanism is controlled to achieve the opening and closing of blinds to attain the purpose of heat insulation or heat transfer. This paper set up a tube on the original exhaust pipe in front of the exhaust aftertreatment devices. In order to overcome the effect of DFCO on the hybrid electric buses emissions, the two-position and three-port solenoid valve is controlled to change the path of the gas emission.