Patent Application
20110131979
Embodiments described herein relate to a system and method for cleaning an exhaust gas recirculation (EGR) component. More specifically, embodiments described herein relate to a system and method for removing deposits in an EGR cooler.
Exhaust gas recirculation (EGR) is used to reduce nitrogen oxide (NOx) emissions in both gasoline and diesel engines. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures. EGR systems recirculate a portion of an engine's exhaust gas back to the engine cylinders. Intermixing fresh, incoming air with recirculated exhaust gas dilutes the mix, which lowers the flame temperature and reduces the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix, which lowers the peak combustion temperature. Since NOx is more readily formed at high temperatures, the EGR system limits the generation of NOx by keeping the temperatures low.
Many EGR systems include at least one EGR cooler connected in series or in parallel between an exhaust manifold and an intake manifold of an engine. Some engines, especially compression ignition or diesel engines, use the EGR coolers to cool the portion of exhaust gas being recirculated. The cooled exhaust gas has a lower latent heat content and can aid in lowering combustion temperatures even further. In general, engines using EGR to lower their NOx emissions can attain lower emissions by cooling the recirculated exhaust gas as much as possible.
Exhaust gas constituents in the exhaust gas being recirculated to the intake manifold may build-up on the EGR cooler. Further, various hydrocarbons may condense onto the EGR cooler. The build-up of deposits and condensation may cause a degradation of heat transfer efficiency and an increase in the pressure drop across the EGR cooler, which may eventually result in the overall loss of engine performance and efficiency.
The most common ways that deposit build-up are addressed include removing and cleaning the EGR cooler, and replacing the EGR cooler. Additionally, condensation of exhaust gas constituents has been addressed by delaying initiation of EGR under cold start conditions, limiting the amount of exhaust gas being recirculated, or limiting the amount of cooling applied to the recirculated exhaust gas in an effort to minimize the degree and amount of condensates. These measures, although effective in increasing the service life of engine components and decreasing the likelihood of failures, may be insufficient in addressing the impact that the EGR system has on the emissions generated by the engine.
A method for dislodging exhaust gas deposits from an exhaust gas recirculation (EGR) cooler associated with an engine includes the steps of providing at least one on-board gas source for providing a gas at a superatmospheric pressure, and placing the EGR cooler in fluid communication with the gas source with a supply conduit. The supply conduit includes a valve that is selectively operable to a closed condition closing the supply conduit and to an open position opening the supply conduit. The method also includes the step of operating the valve from the closed condition to the open condition to allow the superatmospheric gas to flow through the supply conduit to the EGR cooler.
Another method for dislodging exhaust gas deposits from an exhaust gas recirculation (EGR) cooler associated with an engine includes the steps of providing gas sources that are each capable of providing a gas having superatmospheric pressure. Each of the gas sources has a corresponding valve disposed in a parallel arrangement. The method also includes the step of placing the EGR cooler in fluid communication with the superatmospheric gas through a supply conduit. The valves are selectively operable to a closed condition closing the supply conduit and to an open position opening the supply conduit from the corresponding gas source. The method further includes the step of delivering the superatmospheric gas to the EGR cooler through a nozzle disposed at the end of the supply conduit.
An EGR cooler cleaning system for dislodging exhaust gas deposits from an exhaust gas recirculation (EGR) cooler associated with an engine a gas source configured to fluidly communicate a superatmospheric gas to the EGR cooler. The cooler cleaning system also has a gas pulse delivery system having a valve that is selectively operable to a closed condition closing the supply conduit, and to an open position opening the supply conduit. The opening and closing of the valve creates percussive pulses of the superatmospheric gas. A supply conduit is configured for delivering the percussive pulses of superatmospheric gas to at least one nozzle.
Referring to
The exhaust manifold 12 also routes exhaust gas EG to an exhaust gas recirculation (EGR) system 24 that includes an EGR cooler 26. The EGR system 24 may include other components, such as a diesel oxidation catalyst, a diesel particulate filter, valves, sensors, filters, among other components. The EGR system 24 receives a second portion of the exhaust gas EG from the engine 10. The EGR cooler 26 routes exhaust gas EG to an engine intake manifold 28.
Each of the cylinders of an engine (not shown) are connected to the exhaust system 10 through the engine exhaust manifold 12. The engine exhaust manifold 12 is in fluid communication with the turbine 18 of the turbocharger 16 with a first exhaust passage 30. The exhaust gas EG turns the turbine 18, which causes the turbo compressor 20 to pressurize a charge of air. The charge of air flows through a second air passage 32 to the CAC 22 where it is cooled. From the CAC 22, the cooled charge of air flows to a second turbostage or to the engine intake manifold 28 on a third air passage 34.
A fourth exhaust passage 36 is located on the EGR system 24 and permits the fluid communication of the exhaust manifold 12 with the EGR cooler 26. From the EGR cooler 26, the cooled exhaust gas flows to the engine intake manifold 28 on a fifth exhaust passage 38. The engine intake manifold 28 is fluidly connected to the cylinders to provide the engine with a mixture of cooled exhaust gas EG from the EGR system 24 and charge air from the turbocharger system 14. While in the engine cylinders, the mixture (exhaust gas and fresh air) is additionally mixed with fuel, yielding useful work to the engine, heat and exhaust gas EG.
Exhaust gas deposits build-up on the EGR cooler 26, which may cause a degradation of heat transfer efficiency and an increase in the pressure drop across the EGR cooler. The build-up of exhaust gas deposits may eventually result in the overall loss of engine performance and efficiency.
Referring now to
The air pulse delivery system 42 includes at least one supply conduit 44 for delivering the superatmospheric gas G to at least one nozzle 46 disposed at the end of the supply conduit. The nozzle 46 delivers the percussive pulses of superatmospheric gas G to the EGR cooler 26. The at least one control valve V1-VN is selectively operable from a closed condition closing the supply conduit 44 that forms the flow path of the superatmospheric gas G and to an open condition opening the supply conduit for the flow of the superatmospheric gas G from the at least one gas source S1-SN to the nozzle 46. At the downstream or outlet side of the EGR cooler 26, the at least one nozzle 46 may be placed directly against the EGR cooler or may be spaced a distance from the EGR cooler. It is also possible that the nozzle 46 can be placed at locations other than the outlet side of the EGR cooler 26.
The EGR cooler cleaning system 40 of
As seen in
The gas sources S1-SN store charges of gas in a suitable volume and at a suitable pressure to enable suitable percussive pulses to be delivered to the EGR cooler 26 to dislodge and free deposits from the EGR cooler. The gas sources S1-SN may be capable of holding gas at a pressure in excess of 125 psi, however lower pressures are possible. Any suitable gas source can be used to charge the onboard gas sources S1-SN. Any air compressor device, such as the air compressor devices on commercial vehicles, could be used as an on-board source to charge the tanks S1-SN. Alternatively, shop air is a gas that is readily available at sufficiently high pressure at automotive and trucking service facilities, and can be delivered and stored in the gas sources S1-SN.
Valves capable of delivering percussive pulses are described in U.S. Pat. No. 5,520,366 “Rapid Pulse Delivery Diaphragm Valve”, which is incorporated by reference herein. This valve includes a solenoid that is actuated by electricity to open the valve. The valve has a diaphragm that is held seated on a valve seat closing when the solenoid is not actuated. When the solenoid is actuated, the hold on the seat is released. Rapid opening of the valve is accomplished by using the pressure of air present at the valve inlet to lift the diaphragm off the seat. Any other valve or other devices that deliver a pulse of superatmospheric gas G from at least one gas source S1 to the EGR cooler 26 are also possible.
The combination of force of superatmospheric gas G with the percussive pulses of superatmospheric gas dislodges and frees deposits from the surface and pathways of the EGR cooler 26. The cleaning system 40 may be actively operated to deliver superatmospheric gas G during engine use, during start-up conditions, or after shutdown. Normal exhaust gas EG flow is then able to sweep away the dislodged deposits.
Referring now to
The superatmospheric gas G may be delivered to the EGR cooler 26 in percussive pulses, in varying amounts of pressure over time, or in a constant amount of pressure over time. A gas pulse delivery system 142 includes the at least one control valve V100 for creating percussive pulses of superatmospheric gas that are capable of dislodging deposits on the EGR cooler 26.
The air pulse delivery system 142 also includes at least one supply conduit 144 for delivering the superatmospheric gas G to at least one nozzle 146. The at least one nozzle 146 delivers the percussive pulses of superatmospheric gas G to the EGR cooler 26. Similar to the nozzle 46, the nozzle 146 may be placed directly against the EGR cooler 26 or may be spaced a distance from the EGR cooler.
The EGR cooler cleaning system 140 of
It is possible that a collection device 48 could be used in conjunction with the EGR cooler cleaning system 40, 140 to collect large particles. The collection device 48 may include a cavity having a valve 50 to dispense the collected particles or may have a burner to incinerate the collected particles. It is also possible that the EGR cooler cleaning system 40, 140 can be incorporated on any exhaust gas system 10, 100 having an EGR cooler 26 and a source of compressed gas on the vehicle, such as an air compressor, a turbocharger, a supercharger, among other sources of compressed gas.
