Abstract:
An internal combustion engine system has an internal combustion engine with an intake for air and an exhaust for products of combustion. The engine has a turbocharger for pressurizing intake air in response to passage of the products of combustion. An exhaust aftertreatment device receives the exhaust from the engine to filter diesel particulates. A device for regenerating the exhaust aftertreatment device has a feed line and nozzle for injecting duel upstream of the exhaust aftertreatment device on a periodic basis. A system and method for purging the fuel line and the nozzle utilizes pressurized air from the engine turbocharger via an air tank when the regenerating device is not injecting fuel.

Description:
FIELD OF THE INVENTION 
     The present invention relates to internal combustion engine systems and more particularly systems for regenerating diesel particulate traps. 
     BACKGROUND OF THE INVENTION 
     The diesel engine has been used for commercial, industrial, agricultural and other heavy duty applications for well over 100 years. The fundamental diesel engine cycle promotes high part-power fuel efficiency and has therefore become the engine type of choice for commercial and agricultural purposes. Although the diesel engine has outstanding efficiency and long term durability, environmental issues have increased in significance with substantial increases in urban populations throughout the world. Nowhere is this force more evident than in the United States, beginning with the Environmental Protection Agency (EPA) established over 30 years ago. During the ensuing years, the EPA has proposed and adopted ever increasing emissions limits for on-highway vehicles. The application of these standards has now been applied to off-road vehicles such as tractors, combines and other vehicles not normally driven on public highways including power generation systems. The EPA has adopted successive tiers of emissions requirements and the most recent is Tier IV. This requirement necessitates a diesel particulate filter (DPF) along with a requirement for regeneration of the filter to remove particulate matter accumulated on the filter. 
     A number of systems have been proposed to regenerate filters, relying on the fact that diesel particulate matter combusts when local temperatures are above 600° C. These systems may include engine management, resistive heating coils, microwave generation, and a fuel burner to increase the exhaust temperature. Another system is hydrocarbon injection in the form of atomized fuel upstream of a catalytic oxidizer to increase the exhaust temperature around the filter. One of the problems with such a system is that the fuel nozzle and lines leading to the nozzle are subjected to high ambient temperatures reaching into the region where the hydrocarbon fuel tends to coke and form deposits in the fuel nozzle and associated supply passages. 
     The solution to this problem for heavy duty on-highway vehicles is to blow out the line with compressed air from the standard air brake system supply tank, usually at around 100 pounds per square inch (psi). While the system is feasible for highway diesel propulsion systems it is not available for off-highway agricultural equipment which typically does not use compressed air as a power source for an air brake system. 
     Thus, there exists a need in the art for a regeneration system that employs a purging process with compressed air from a source other than a dedicated pump and reservoir for compressed air. 
     SUMMARY OF THE INVENTION 
     In one form, the above objects are met by an internal combustion engine system including an internal combustion engine having an intake for air and an exhaust for products of combustion. A device pressurizes air for delivery to the engine intake for combustion. An exhaust aftertreatment device receives the exhaust from the engine. A regeneration device for the exhaust aftertreatment device has a feed line and nozzle for injecting fuel upstream of the exhaust aftertreatment device on a periodic basis. A system for purging the fuel line and the nozzle utilizes air from the intake air pressurizing device when the generating device is not injecting fuel. 
     In another form, the above objects are met a method for purging fuel lines and nozzle in a fuel driven regeneration device for an internal combustion engine having a device for pressurizing air for delivery to the engine. The method includes the steps of:
         extracting air from said air pressurization device,   storing said extracted pressurized air in a storage tank, and   releasing said air to said fuel lines when the fuel lines are not receiving fuel for said regeneration.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic representation of an internal combustion engine system embodying the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an internal combustion engine system including an engine  10 , herein illustrated as being of the diesel type, in which the heat of compression ignites a fuel charge to produce a propulsive force that is translated through connecting rods and crankshaft to a rotary output. The internal combustion engine has a fuel system (not shown) that provides timing and quantity control of the fuel charge to produce appropriate power, fuel efficiency, and emissions levels. The internal combustion engine is coupled with a turbocharger  12  by means of an exhaust connection  14 . The turbocharger  12  has a turbine section  16  that receives products of combustion from engine  10  via line  14  to produce a rotary output which is used to drive a compressor section  18  to pressurize inlet air from line  20  and air filter  22 . The pressurized air is discharged from compressor  18  via line  24  to an intercooler  26 . Intercooler  26  receives the air that has been heated by the compressor  18  and cools it to increase the charge density. Intercooler  26  may be of the air-to-air or air-to-coolant type as appropriate for the particular application. The cooled output from intercooler  26  is fed by line  28  to the intake of engine  10  where it is consumed by the engine in standard fashion. 
     The output from the turbine  16  of turbocharger  12  is fed by exhaust line  30  to an exhaust aftertreatment device generally indicated by reference character  32 . The exhaust aftertreatment device  32  includes a diesel particulate filter  34  (DPF) that filters particles from the exhaust flowing through line  30 . One of the characteristics of the diesel particulate filter is that it continues to collect particles until a point where the pressure drop across the diesel particulate filter increases to necessitate regeneration of the particle filter. The particulates attached to the filter  34  will combust at around a temperature of 600° C. Various methods are used to achieve this temperature to cause the particles to combust or burn and remove the obstruction to the filter. 
     Although many other forms of regeneration may be employed, the system illustrated in  FIG. 1  utilizes a diesel oxidization catalyst  36  upstream of the diesel particulate filter. The diesel oxidization catalyst is used in combination with a nozzle  38  that sprays into the exhaust line  30  an appropriate quantity of fuel which interacts with the diesel oxidization catalyst to increase the temperature of the exhaust gases to the point where the particles will combust. Fuel nozzle  38  is supplied with the appropriate quantity of fuel from a fuel metering system generally indicated by reference character  40 . Fuel metering system  40  receives a supply of fuel from an appropriate source via line  42 . It should be noted that typically the source for fuel in line  42  would be the fuel control for the internal combustion engine  12 . A return line  44  returns fuel not passing through nozzle  38  to an appropriate fuel supply. A check valve  46  provides fuel flow only into a metering device  48  from supply line  42 . A pressure sensor  50  is used to control the flow to the fuel nozzle  38 . A T connection  52  is positioned downstream of the metering device  48 . The metering device  48  is actuated to supply the appropriate quantity of fuel through nozzle  38  at the appropriate time in the engine duty cycle to increase the exhaust temperature past the DOC to increase temperatures to the point where the particles combust. 
     The nozzle  38  and line  54  are exposed to temperatures prevailing within the exhaust line  30 . These temperatures, during operation, can reach levels at which any residual fuel in nozzle  38  and line  54  can coke and impair operation of the system. In order to prevent such an occurrence, an air supply line  56  is connected between the T connection  52  and sir tank  62 . A solenoid valve  58  in line  56  provides control and a check valve  60  permits air flow only towards T connection  52 . Line  56  extends to the tank  62  having a capacity suitable for normal operation of the purging process described below. 
     Air tank  62  is connected to the output of the compressor  18  in the turbocharger  12  by a line  64  extending to the intercooler  26  output line  28 . A check valve  66  in line  64  permits flow only into the air tank  62  and a metering orifice  68  limits the quantity and rate of air so entered into air tank  62 . As herein shown, the pressure input to air tank  62  is downstream of intercooler  26 . However, it may alternately be connected to an upstream section via a line  70  illustrated in dashed fashion. An additional solenoid valve  72  is provided in fuel return line  44  to complete the elements of the regeneration system. 
     During operation of engine  10 , particles passing through exhaust line  30  are collected on the diesel particulate filter  34 . Through appropriate pressure differential sensors (not shown), the system is triggered to regenerate the filter  34  by increasing exhaust temperature. At this point, fuel is delivered via line  42  through the fuel metering device  48  and the appropriate quantity of fuel is injected into the exhaust line  30  via nozzle  38 . The fuel interacts with the DOC to cause an elevation of the temperature within the aftertreatment device  32  to a level where the particulates combust. 
     When regeneration of the DOC is complete, the T connection  52  is connected to the air tank  62  by opening solenoid valve  58  and the return line solenoid  72  is closed to prevent air flow through fuel return line  44 . In this position, air is delivered from tank  62  through line  56  and  54  and nozzle  38  to effectively completely purge line  54  and nozzle  38 . At the same time, check valve  46  prevents air flow back into the fuel supply line  46 . This minimizes any fuel that is residing in the fuel line or nozzle to minimize coking. Although solenoid and check valves are illustrated to control the air and confine it substantially to the nozzle  38  and fuel line  54 , it should be apparent to those skilled in the art that other arrangements may be employed, such as a three way vale in place of the T connection  52 . 
     By utilizing bleed air from the engine intake pressurization system, the need for a dedicated air pressurizing pump is eliminated. The orifice  68  limits the quantity of air flow from the engine operating system to have a negligible affect on engine performance. It has been found that no more than 5% flow is needed to supply the air tank under normal operating conditions. It has also been found that an air pressure level significantly lower than heretofore proposed is adequate and appropriate for purging line  54  and nozzle  38 . Pressure levels as low as 30 psi may be employed for this purpose since pressures existing in the exhaust line are no greater than 5 psi, even under extreme conditions. 
     The use of simple check valves and solenoid valves enable the efficient purging of the fuel line and nozzle without the use of complex diversion valves. Check valves and solenoid valves are relatively inexpensive but extremely reliable in service. 
     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.