Abstract:
A high flow EGR system for an internal combustion engine having a pair of series connected EGR coolers and a water droplet condensation collector and reservoir connected to the gas flow. The reservoir feeds a pump which is actuated to inject the liquid to the engine adjacent each cylinder for uniform distribution of the water to the engine cylinders. The pump is controlled to inject the water at appropriate conditions during the engine operating cycle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to exhaust gas recirculation (EGR) systems in which significant quantities of exhaust gas are recirculated to the intake of an internal combustion engine. 
     2. Description of the Related Art 
     In the continuing quest to meet lower emissions levels for internal combustion engines, the use of ever increasing quantities of EGR has been proposed. In order to reduce the combustion temperatures and, therefore, the generation of oxides of nitrogen, percentages of up to 50% and higher have been implemented. In order to minimize the effect of the large quantities of exhaust gas recirculation, it has become necessary to significantly cool the exhaust gasses to a point that greatly increases their density and minimizes the effect on power and fuel consumption when combined with the combustion air for the engine. 
     One of the problems with a system of this type is that the moisture in the products of combustion reaches a point where the water condenses into droplets that can accumulate or puddle at random locations within the system. Depending upon the engine operating conditions, the random collection of droplets may be swept into the intake of one or more cylinders in an uneven manner. While the engine can function with this occurrence, it can cause excess oxides of nitrogen in some cylinders and increased smoke and hydrocarbons in other cylinders. 
     What is needed in the art, therefore, is an EGR system that recirculates high percentages of exhaust gas but avoids the uncontrolled ingestion of water droplets into the engine. 
     SUMMARY OF THE INVENTION 
     In one form, the invention is an EGR system for introducing significant percentages of exhaust gas into the intake of an air-breathing, fuel-consuming, multi-cylinder internal combustion engine having an exhaust for products of combustion and an intake for combustion air. This system includes a passage connecting the exhaust of the internal combustion engine to its intake and a valve for controlling flow of exhaust gasses through the passage. At least one heat exchanger is positioned in the passage for significant cooling of the gasses therein, thereby promoting condensation of moisture. A collector is positioned downstream of the heat exchanger for collection of condensed water from the gas stream. A liquid pump is fluidly connected to the collector and is, in turn, connected to a plurality of injectors adjacent the air intakes for the cylinders of the engine to permit uniform flow of liquid to the cylinders of the engine. 
     In another form, the invention involves a power system comprising an air-breathing, fuel-consuming, multi-cylinder internal combustion engine having an exhaust for products of combustion and an intake for combustion air. A passage connects the exhaust of the IC engine to its intake and a valve is positioned in the passage for controlling flow of exhaust gas to the intake. At least one heat exchanger is positioned in the passage for cooling exhaust gasses to a significant extent and promoting condensation of moisture. A collector is positioned downstream of the heat exchanger for collecting the condensed water in the gas. A pump is fluidly connected to the collector and feeds a plurality of injectors to provide a uniform distribution of condensate to the intake of the IC engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a power system embodying the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is shown in schematic fashion an internal combustion engine  10  providing a rotary power output through crankshaft  12 . Engine  10  is a fuel-consuming, air-breathing, multi-cylinder internal combustion engine having a plurality of cylinders  14  in which individual pistons reciprocate and are connected to respective connecting rods providing a rotary power output through crankshaft  12 . The cylinders  14 , in the present instance, receive fuel through individual fuel injectors  16  for each cylinder from a fuel system  18  via a feed line  19 . The fluid interconnections between the injectors  16  and the fuel system  18  are not shown in detail to simplify the description of the present invention. The system may be a high pressure common-rail in which high pressure in maintained in line  19  or a system in which high pressure is generated at the fuel injectors  16 . Other fuel system types may be employed. When internal combustion engine  10  is of the compression ignition, or diesel type, air within each cylinder is compressed sufficiently to increase its temperature so that fuel injected through fuel nozzles  16  adjacent the top of the compression stroke is ignited and provides the combustion force driving the pistons downward. Appropriate exhaust valves cause the products of combustion to be discharged into an exhaust manifold  20  and then to a turbine  22  of a high pressure turbocharger  24 . From there, the exhaust gases pass by line  26  to a low pressure turbine  28  of a low pressure turbocharger  30  and, finally, to exhaust  32 . The exhaust flow at this point is usually directed through exhaust aftertreatment devices such as particulate filters and catalytic converters to further reduce exhaust products emissions. 
     The air for combustion passes by way of intake line  34  to a compressor  36  of the low pressure turbocharger  30  and is driven by shaft  38  connected with the turbine  28 . From there, the air passes from compressor  36  via line  40  to an interstage heat exchanger or cooler  42  to increase the density of the charge. As illustrated, the cooler  42  utilizes engine coolant through lines  44  and  46 . It should be apparent, however, that other types of coolers may also be employed. The air that has been cooled by cooler  42  passes through line  48  to a high pressure compressor  50 , which is driven by high pressure turbine  22  through shaft  52 . The air thus pressurized, and partially cooled, passes through line  54  to a charge air cooler  56 . Charge air cooler  56  is typically an air-to-air cooler which utilizes ambient air as the heat sink to provide a significant reduction in temperature and appropriate increase in charge density. From the charge air cooler  56 , a line  58  extends to an intake manifold  60  for internal combustion engine  10 . The air thus passed to the intake manifold  60 , is available for delivery to the engine cylinders  14  using valves (not shown to simplify the understanding of the invention) and to be compressed and combined with fuel to ignite and provide the power output. 
     The engine  10  incorporates exhaust gas recirculation (EGR) by means of a passage  62  connected to the exhaust manifold  20 . It should be apparent to those skilled in the art that the conduit  62  may be connected at any point in the exhaust flow as appropriate for extracting the desired percentage of exhaust gas. The exhaust gas directed through conduit  62  passes through a high temperature EGR cooler  64 , which utilizes engine coolant through lines  66  and  68  to take heat out of the exhaust gasses passing therethrough. The exhaust gasses then are connected to a valve  70  by line  72 . Valve  70  is controlled to alter the flow passage for exhaust gas in order to control the flow of exhaust gas into a line  74  to a low temperature EGR cooler  76  in which the EGR is introduced into the intake air conduit  58  and mixed with the fresh air adjacent the outlet side  78  of both the charge air cooler  56  and low temperature EGR cooler  76 . As illustrated, the charge air cooler  56  and low temperature EGR cooler  76  are incorporated into a single housing. It should be apparent, however, to those skilled in the art that the two components may be employed as separate units so long as the fresh air and recirculated exhaust gas combine downstream of the coolers. 
     Because the gasses passing through the cooler are cooled to such an extent, moisture in the gas condenses out as droplets and, for this purpose, a condensation reservoir  80  is employed and connected to the gas flow path by conduit  82 , which reaches a low or drain point within the combined coolers  56  and  76 . Although  FIG. 1  is shown as schematic, it should be apparent to those skilled in the art that the physical geometry of the elements may be altered so as to provide a low point adjacent the line  82  receiving the combined flow and collecting the moisture droplets that have been condensed. The condensation reservoir  80  is connected by a line  84  to the inlet of a pump  86  that, in turn, connects to a line  88  leading to a plurality of water injectors  88  that inject water into the intake manifold  60  adjacent the individual cylinders  14 . Pump  86  may be mechanically or electrically driven as appropriate for the overall system. 
     The engine  10  employs electronic control in the form of an electronic control unit (ECU)  92  that receives inputs from sensors  94  via line  96  to provide control of fuel system  18  via line  98 . It should be apparent to those skilled in the art that a multiplicity of sensors  94  may be provided to generate signals reflecting appropriate engine parameters which are fed to the ECU  92  and, thus, provide signal inputs to fuel system  18  to control the quantity of fuel and timing of injection for the particular engine operating condition so as to provide adequate power while minimizing fuel consumption and emissions. 
     ECU  92  also provides control inputs to EGR valve  70  via a line, which has been omitted to simplify the drawing, to coordinate the EGR flow with the desired conditions of the engine. ECU  92  also may provide a signal to control pump  86  via line  100  to withdraw liquid from reservoir  80  and pressurize it for delivery to the water injectors adjacent the cylinders for uniform consumption by the engine. ECU  92  also provides an input to pump  86  that prevents injection of water during light load operating conditions below approximately 20% of maximum power. In addition, injection may be controlled when engine  10  experiences rapid increases in required power output to act in lieu of EGR to minimize emissions during this operating condition. 
     In order to ensure that the appropriate levels of liquid in the condensation reservoir  80  are maintained, a level sensor  102  senses the level and provides a signal input to ECU  92  via line  104  to ensure that the reservoir  80  does not overflow or water injection is overused. The pump  86  is controlled to inject a desired water flow rate which can be a function of engine rpm, load, and ambient temperature and other operating parameters of engine  10 . 
     The system described above utilizes a controlled collection of moisture droplets in the engine intake air to collect and controllably inject in a uniform manner to multiple cylinders of the engine. Such a system uniformly distributes the moisture in a way that has a minimum impact on the engine and which avoids issues of uncontrolled ingestion of liquid or the need for discharging directly overboard liquid that may have contaminants within it. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.