Motor vehicle provided with a diesel propulsion engine

#This invention concerns an exhaust system for a motor vehicle equipped with a diesel propulsion engine, the exhaust system of which comprises a discontinuously regenerating exhaust gas purification system. Discontinuously regenerating exhaust gas purification systems include components such as diesel particulate filters and NOx-accumulating catalytic converters.

#To comply with environmental specifications, exhaust gases of motor vehicles propelled by combustion engines are subjected to a purification process. Specifically, appropriate particulate filters are utilized to reduce particulate emissions of exhaust gases of motor vehicles propelled by diesel engines. Such particulate filters must be periodically regenerated by burning off particles accumulated on a filter surface. Due to the relatively low exhaust gas temperatures of modern diesel engines, to initiate regeneration, the exhaust gas temperature must be raised by approximately 100° C., using appropriate procedures or devices. The exhaust gas temperature must be raised if filter regeneration is to be feasible in conditions other than full load operation, even if fuel additives are used that are capable of lowering particulate ignition temperature. Without such additives, depending on the soot composition, the particulate ignition temperature ranges between 470° C. and 600° C. However, the use of such additives, in the long run, can cause the particulate filter to clog, necessitating its cleaning.

#For this purpose various burners (refer, e.g., to DE 19504183 A1 and DE 19717544 A1) have been proposed for installation upstream of the particulate filter. Some disadvantages with such burners are the considerable structural and financial efforts associated with such burners, the considerable increase in space required due to the integration of a relatively large burner into the exhaust system, and the detrimental effect on the flow conditions within the exhaust pipe.

#In the following, this invention is explained using two preferred embodiments schematically represented in the drawing. Shown are:

#FIG. 1 shows a relevant section of an exhaust system for a motor vehicle, whose exhaust gas purification unit includes a NOx-accumulating catalytic converter to be regenerated periodically,

#FIG. 2 shows the incorporation of the section of an exhaust system illustrated in FIG. 1, in a vehicle,

#The section of an exhaust system 29 of a motor vehicle propelled by a diesel engine, represented in FIG. 1—listed sequentially in flow direction A—comprises: a pre-tube 1; an auxiliary oxidizing converter 2 with a catalytic converter body 4 installed in a housing 3; one intermediate tube 5 with a fuel evaporator 6 installed in the intermediate tube 5; and one NOx-accumulating catalytic converter 7 with a housing 8 and a catalytic converter body 9 installed in the NOx-accumulating catalytic converter 7. The NOx-accumulating catalytic converter 7 represents an exhaust gas purification system R to be periodically regenerated. The auxiliary oxidizing converter 2 and the fuel evaporator 6 jointly represent a fuel evaporator unit 10 in which fuel vapors 11 are fed into exhaust gases flowing through the intermediate tube 5.

#The fuel evaporator 6 is configured as a heat exchanger 12 in which diesel fuel fed to the heat exchanger 12 through a fuel supply line 13, is vaporized utilizing the heat contained in the exhaust gases and where the fuel vapors 11 are discharged from the heat exchanger 12 using the fuel vapor discharge opening 14.

#All of the fuel vapors generated in the heat exchanger 12 are added to the exhaust gases flowing through the intermediate tube 5.