Abstract:
A method for dislodging exhaust gas deposits from an exhaust gas recirculation (EGR) cooler ( 26 ) associated with an engine includes the steps of providing at least one on-board gas source (S) for providing a gas (G) at a superatmospheric pressure, and placing the EGR cooler in fluid communication with the gas source through a supply conduit ( 44, 144 ). The supply conduit ( 44, 144 ) includes at least one valve (V) 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 at least one valve (V) from the closed condition to the open condition to allow the superatmospheric gas (G) to flow through the supply conduit ( 44, 144 ) to the EGR cooler ( 26 ).

Description:
BACKGROUND 
       [0001]    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. 
         [0002]    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&#39;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. 
         [0003]    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. 
         [0004]    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. 
         [0005]    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. 
       SUMMARY 
       [0006]    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. 
         [0007]    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. 
         [0008]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic of an exhaust gas system having an EGR cooler cleaning system in fluid communication with an EGR cooler. 
           [0010]      FIG. 2  is a schematic indicating the pulsing of superatmospheric gas to the EGR cooler. 
           [0011]      FIG. 3  is a schematic of the exhaust gas system having an alternative EGR cooler cleaning system in fluid communication with the EGR cooler. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1 and 3 , a schematic diagram of an exhaust system, generally shown at  10 , includes an engine exhaust manifold  12  that routes exhaust gas EG to a turbocharger system  14 . The turbocharger system  14  includes a turbocharger  16  having a turbine  18  and a turbo compressor  20 . The turbocharger system  14  receives a first portion of the exhaust gas EG from the engine exhaust manifold  12 . Downstream of the turbocharger  16  is a charge air cooler (CAC)  22 . 
         [0013]    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 . 
         [0014]    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 . 
         [0015]    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. 
         [0016]    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. 
         [0017]    Referring now to  FIGS. 1 and 2 , an EGR cooler cleaning system  40  supplies superatmospheric gas G to the EGR cooler  26 . 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. At least one on-board gas source S 1 , such as a tank, is in fluid communication with the EGR cooler  26 . The at least one gas source S 1  is charged with a gas, such as air, to a superatmospheric pressure. A gas pulse delivery system  42  includes at least one control valve V 1  that is selectively operable for fluidly communicating percussive pulses of superatmospheric gas that are capable of dislodging deposits on the EGR cooler  26 . 
         [0018]    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 V 1 -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 S 1 -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 . 
         [0019]    The EGR cooler cleaning system  40  of  FIG. 1  has multiple gas sources, S 1 , S 2 , S 3  . . . SN with multiple control valves V 1 , V 2 , V 3  . . . VN. Each of the plurality of gas sources S 1 -SN has a corresponding valve V 1 -VN from the plurality of valves disposed in a parallel arrangement. It is also possible that gas sources S 1 -SN may be fluidly connected to control valves V 1 -VN in a series arrangement, or some combination of parallel and series arrangement. 
         [0020]    As seen in  FIG. 2 , the control valves V 1 -VN may open asynchronously and with a time delay to provide multiple pulses of superatmospheric gas G. It is also possible that the control valves V 1 -VN may open asynchronously without a time delay between pulses. The control valves V 1 -VN may also open synchronously in multiple or single pulses, or in any other arrangement. 
         [0021]    The gas sources S 1 -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 S 1 -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 S 1 -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 S 1 -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 S 1 -SN. 
         [0022]    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 S 1  to the EGR cooler  26  are also possible. 
         [0023]    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. 
         [0024]    Referring now to  FIG. 3 , an alternate embodiment of an EGR cleaning system is indicated generally at  140 , the cleaning system being used on the exhaust gas system  100 . The EGR cleaning system  140  includes the turbo compressor  20  as the superatmospheric gas source S 100 , which is in fluid communication with the EGR cooler  26 . The superatmospheric gas G is charge air that is diverted by at least one control valve V 100  on the second passage  32 . The gas source S 1  provides charge air in a suitable volume and at a suitable pressure to dislodge and free deposits from the EGR cooler. 
         [0025]    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 V 100  for creating percussive pulses of superatmospheric gas that are capable of dislodging deposits on the EGR cooler  26 . 
         [0026]    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. 
         [0027]    The EGR cooler cleaning system  140  of  FIG. 3  may also have multiple gas sources S 1  with multiple control valves V 1 , such as multiple turbo compressors  20  or the addition of tanks. In a multiple gas source S 1 -SN embodiment, the gas sources may open synchronously or asynchronously. In both the single gas source or the multiple gas source S 1 -SN embodiments, the pulses of superatmospheric gas G may be delivered to the nozzle  146  with a time delay or without a time delay, to provide a single or multiple pulses of superatmospheric gas G to the EGR cooler  26 . 
         [0028]    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.