Internal combustion engine system
View Patent ↗A compression-ignition internal combustion engine system having an exhaust passage and an exhaust gas treatment arrangement, wherein the exhaust gas treatment arrangement comprises a three-way catalytic converter.
1. A compression-ignition internal combustion engine system comprising:
a compression-ignition engine,
an exhaust passage and
an exhaust gas treatment arrangement, wherein the exhaust gas treatment arrangement comprises a single catalyzing device being a three-way catalytic converter and a diesel particulate filter located downstream of the three-way catalytic converter in a direction of exhaust gas flow;
further comprising an electronic control unit including instructions for:
operating the engine so as to control the flow rate of gases into one or more combustion chambers of the engine and/or to control the injection of fuel into said one or more combustion chambers to provide stoichiometric combustion over a predetermined range of engine load;
in a first mode, at low engine loads, operating the engine at high EGR rates under normal diesel combustion to reduce NOx emissions, in a second mode, at medium to high engine loads, operating the engine under stoichiometric conditions where NOx emissions can be reduced by way of the three-way catalytic converter and, in a third mode, under very high engine loads and/or engine speeds, operating the engine under normal diesel combustion conditions and low EGR rates to obtain maximum torque;
operating the engine in an air-lead mode whereby the intake air flow rate is controlled to achieve a demanded torque and an amount of fuel injected is controlled to obtain a target air/fuel ratio based upon the intake air flow rate;
operating the engine in an air-lead mode during quasi steady state engine conditions and under a fuel-lead mode during conditions of rapid changes in torque demand.
2. The compression-ignition internal combustion engine system according to claim 1 , wherein the engine is operated in a substantially stoichiometric combustion mode.
3. The compression-ignition internal combustion engine system according to claim 1 , wherein the three-way catalytic converter and the diesel particulate filter are combined into a single unit.
4. The compression-ignition internal combustion engine system according to claim 1 , wherein the exhaust gas treatment arrangement includes a first oxygen sensor disposed in the exhaust passage downstream of the engine and upstream of the three-way catalytic converter in order to monitor the constituent exhaust gases and so enable the accurate control of the air/fuel ratio supplied to the engine such that optimum performance of the three-way catalytic converter can be maintained.
5. The compression-ignition internal combustion engine system according to claim 4 , wherein the exhaust gas treatment system includes a second oxygen sensor disposed downstream of the three-way catalytic converter and upstream of the diesel particular filter.
6. The compression-ignition internal combustion engine system according to claim 4 , further including a fuel injector disposed upstream of the three-way catalytic converter to inject fuel into the exhaust passage.