Emission control system e.g. for motor vehicle diesel internal combustion engine, comprises a butterfly on-off valve and an exhaust gas recirculating system

摘要

The system of emission control comprises a butterfly on-off valve to control the airflow, control of the valve by sensors, an exhaust valve for recirculation of exhaust gases to the inlet, a nitrogen oxides (NOx) storage-reduction catalyst in the exhaust line, and a supply line for reducing agent to the catalyst (fuel supply). The system is also controlled by a programmed control unit. The emission control system comprises: (1) a sensor (11) for detection of quantity of air admitted; (2) a stop-valve (13) to control the flow rate of admitted air in the induction manifold (8); (3) a passage for recirculation of part of the exhaust gases to the inlet manifold, together with a control valve (26) to adjust the flow rate, linked to the control unit (30); (4) a storage-reduction NOx-type catalyst situated in the exhaust line of the engine; (5) a supply line for reducing agent (60) to deliver the agent to the catalyst; and (6) a control system (30) to determine the need for delivery of the reducing agent dependent on the functioning status of the engine. The system also comprises a pressure sensor in the inlet manifold and a second control system for the on-off valve which operates when the quantity of admission is less than a predetermined level. An Independent claim is also included for an emission control process involving the stages of: (1) detection of a quantity of air admission; (2) control of admission by operation of a butterfly stop-valve; (3) effecting recirculation of part of the exhaust gases via a recirculation route (25); (4) adjustment of the flow rate of recirculating exhaust gas by means of a valve (26) on the basis of the functional state of the engine; (5) determination of the need to deliver a reducing agent on the basis of the functional state of the engine; and (6) delivery of a reducing agent to the NOx catalyst.