Patent Application
20110252765
Embodiments described herein relate to a system and method for heating exhaust gas. More specifically, embodiments described herein relate to a system and method for heating exhaust gas to create a regeneration event at a diesel particulate filter.
Exhaust gas aftertreatment systems in diesel vehicles are located downstream of the engine for treating exhaust gases emitted from the engine. The aftertreatment systems typically include a diesel oxidation catalyst, a diesel particulate filter, among other components. Particulate matter from the exhaust gas accumulates on the diesel particulate filter, and if left unchecked, can create a back pressure in the aftertreatment system.
A regeneration event is the periodic oxidation of the collected particulate matter in the aftertreatment system during routine diesel engine operation. When the diesel particulate filter of the exhaust system experiences a build-up of particulate matter, the particulate matter is oxidized to “regenerate” the filter. Regeneration is typically initiated by increasing engine load and activating a post-injection of diesel fuel into the exhaust stream. This post-injection provides sufficient heat to oxidize the trapped particulate matter within the diesel particulate filter.
During idling or part load operating conditions, fuel injected into the combustion cycle is not enough to maintain exhaust gas temperature sufficient to start the DPF regeneration cycle. As such, the loading of the engine must be increased to provide a sufficiently heated exhaust gas to initiate the regeneration downstream at the diesel particulate filter. However many vehicles operate on a “stop and drive” or frequent idling basis, and the resulting exhaust gas may not have a sufficiently high temperature to initiate the regeneration.
An exhaust gas aftertreatment system for a vehicle having an engine includes a fluid passageway extending from the engine to an ambient for fluidly communicating exhaust gas. A diesel particulate filter is disposed on the fluid passageway downstream of the engine. At least one exhaust throttle valve is located downstream of the engine on the fluid passageway. When the exhaust throttle valve is actuated, the valve obstructs the flow of exhaust gas and increases the temperature of the exhaust gas. The heated exhaust gas causes regeneration at the diesel particulate filter.
A method of regenerating an exhaust aftertreatment system of an engine having a diesel particulate filter includes providing a fluid passageway from the engine to an ambient. The method also includes the step of providing an exhaust throttle valve downstream of the engine on the fluid passageway, and actuating the exhaust throttle valve to at least partially obstruct the flow of exhaust gas through the fluid passageway. Further, the method includes compressing and heating the exhaust gas upstream of the exhaust throttle valve, and delivering the heated exhaust gas to the diesel particulate filter to initiate regeneration.
An exhaust gas aftertreatment system for a vehicle having an engine includes an engine control module associated with the engine, a fluid passageway extending from the engine to an ambient for fluidly communicating exhaust gas, and a diesel particulate filter disposed on the fluid passageway downstream of the engine. The system also includes at least one exhaust throttle valve located downstream of the diesel particulate filter on the fluid passageway, and an actuator for actuating the at least one exhaust throttle valve. At least a temperature sensor for sensing the temperature at the aftertreatment system, or a back pressure sensor for sensing the pressure at the aftertreatment system, communicate the temperature or the back pressure, or both, to an engine control module on the engine.
Referring to
A first portion 22 of the exhaust pipe assembly 12 extends from the engine 14 to a diesel particulate filter (DPF) 24. The DPF 24 is a filter constructed from a very high temperature resistant material. The DPF 24 catches and holds particulate matter entrained within the exhaust gases discharged into the exhaust aftertreatment system 10. The DPF 24 is periodically regenerated to limit increases in exhaust aftertreatment system 10 back pressure and to maintain engine 14 efficiency. A second portion 26 of the exhaust pipe assembly 12 extends from the DPF 24 to the outlet 16. An exhaust manifold 28 may be located upstream of the first portion 22 of the exhaust pipe assembly 12. Other components may be disposed on the aftertreatment system 10, such as a diesel oxidation catalyst (not shown) which may be located upstream of the DPF 24.
Referring now to
The exhaust throttle valve 30A may be a butterfly valve 32A, however other types of valves are possible. The butterfly valve 32A regulates the flow F through the fluid passageway 20 with an actuator 34A, which rotates the butterfly valve 32A to be either parallel with the flow F, which is an open position, or perpendicular with the flow F, which is a closed position, or in any position therebetween. The butterfly valve 32A obstructs the flow of exhaust gas F through the exhaust passageway 20. In the parallel-open position, the orifice at the butterfly valve 32A has a maximum orifice area with the least flow obstruction, and in the perpendicular-closed position, the orifice at the butterfly valve has a minimum orifice area with the most flow obstruction. In the perpendicular-closed position, the exhaust throttle valve 30A may sealingly prevent the fluid communication through the second portion 26 of the exhaust pipe assembly 12.
The actuator 34A may be either hydraulically or electrically driven. An engine control module (ECM) 36 controls the exhaust throttle valve 30A through the actuator 34A depending on pressure and temperature conditions in the aftertreatment system 10. A pressure sensor communicates the pressure in the aftertreatment system 10, such as at the exhaust manifold 28 or the DPF 24, and communicates the back pressure to the ECM 36. It is possible that the back pressure can be a change in pressure between two locations on the aftertreatment system 10, such as upstream and downstream of the DPF 24.
A temperature sensor 38 senses the temperature at the DPF 24, the exhaust manifold 28, or anywhere between cylinders 44 and the outlet 16, and communicates the temperature to the ECM 36. It is possible that the temperature can be a change in temperature between two locations on the aftertreatment system 10, such as upstream and downstream of the DPF 24. The ECM 36 also monitors fuel delivery and engine speed to maintain an optimized engine speed/loading and exhaust gas temperature.
Below the predetermined temperature of exhaust manifold 28 or DPF 24, or above the predetermined amount of back pressure in the aftertreatment system 10, the DPF may be clogged with particulate matter. When a predetermined amount of exhaust back pressure is sensed by an exhaust pressure sensor 40, or when a predetermined temperature is sensed at the DPF 24, at the exhaust manifold 28, or anywhere else on the aftertreatment system 10, it is communicated to the ECM 36, which actuates the exhaust throttle valve 30A. The pressure and temperature values are communicated to the ECM 36, and the ECM commands the actuation of the exhaust throttle valve 30A to partially or completely close. In one embodiment, the butterfly valve 32A closes about 80-96% of the orifice in the fluid passageway 20.
The exhaust throttle valve 30A is open until it is actuated by the actuator 34A. When the exhaust throttle valve 30A closes, partially or completely, the exhaust gas F in the aftertreatment system 10 upstream of the exhaust throttle valve 30A is compressed, resulting in an increase in temperature of the exhaust gas F. Also, the resistance to pistons 42 requires a greater amount of fuel injection in the cylinders 44 to meet the engine 14 set point. The additional fuel injection creates additional heat energy in the exhaust gas F. The increased temperature of exhaust gas F upstream of the exhaust throttle valve 30A is transferred to the DPF 24 as the exhaust gas flows downstream to the DPF. The heated exhaust gas F provides sufficient heat to initiate regeneration (soot oxidation) at the DPF 24.
Referring now to
When the exhaust throttle valve 30B is actuated, the temperature of the exhaust gas F is higher on the upstream side of the butterfly valve 32B than on the downstream side. In the aftertreatment system of
Referring now to
The first exhaust throttle valve 30C is disposed in upstream fluid communication from the DPF 24, and in downstream fluid communication from the engine 14 and exhaust manifold 28 on the fluid passageway 20. The second exhaust throttle valve 30D is disposed in downstream fluid communication from the DPF 24 on the fluid passageway 20. Similar to exhaust throttle valves 30A and 30B, the exhaust throttle valves 30C and 30D may be butterfly valves 32C, 32D, however other types of valves are possible.
It is possible that the exhaust throttle valves 30C, 30D can be actuated at the same time, or at different times, and with the same amount of passageway 20 obstruction, or with differing amounts of passageway obstruction. The exhaust throttle valves 30C, 30D are actuated with actuators 34C, 34D to optimize the pressure and the temperature between the valves and at the DPF 24 to effect regeneration of the DPF 24.
The actuation of the exhaust throttle valve 30A-30D, resulting in the regulation of the amount of exhaust gas flow F through the exhaust throttle valve, can be optimized for desired temperatures, pressures and engine loading. Additionally, the ECM 36 can monitor fuel delivery to the cylinders 44 and the engine speed/loading so that the engine speed/loading and exhaust gas temperature can be optimized for desired temperatures at the DPF 24 or anywhere on the aftertreatment system 10. It is possible that the exhaust aftertreatment system 10 may include a variable geometry turbocharger (not shown) to restrict exhaust gas flow F. It is also possible that the aftertreatment system 10 having exhaust throttle valves 30A-30D can be used on a vehicle having an exhaust brake (not shown) on the engine 14.
The aftertreatment system 10 having at least one exhaust throttle valve 30A-30D downstream of the exhaust manifold 28 allows the regeneration of the DPF 24 without significantly increasing the engine speed or loading. With the aftertreatment system 10 having the exhaust throttle valve 30A-30D downstream of the exhaust manifold 28, the vehicle can run on a “stop and drive” basis, where the engine 14 can be run at a lower speed and lower loading, while at the same time, providing exhaust gas flow F with a sufficiently high temperature to initiate the regeneration at the DPF 24.
