Abstract:
An apparatus and a method for enhancing diesel engine performance is provided. At low engine load and cold ambient temperatures, an intake air heater increases the engine load via an engine alternator, which in turn, enables the engine to burn more fuel by the process of combustion. The combusted fuel elevates exhaust gas temperatures, which thereby accommodates cold start, controls white smoke, and aids DPF regeneration.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/956,447, filed Aug. 17, 2007, and which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to an intake air heater designed to aid engine ignition during cold weather conditions, prevent white smoke, and support DPF regeneration. 
       BACKGROUND OF THE INVENTION 
       [0003]    Diesel powered engines are typically ignited by a mixture of injected fuel and hot compressed air. While external ignition devices (e.g., spark plugs) are not required, cold weather conditions pose substantial difficulties with respect to starting diesel engines. That is, as ambient temperatures decrease, the temperature of the internal combustion chamber may not be high enough to effectuate proper ignition of the injected fuel. Accordingly, various starting aids are commonly incorporated within diesel powered vehicles in order generate a sufficient amount of heat to initiate ignition. 
         [0004]    One preferred method for facilitating ignition within diesel engines involves the employment of glow plugs. Generally, glow plugs are disposed within each combustion chamber of the diesel engine, and in operation, they effectively heat the combustion chamber. 
         [0005]    An additional issue attributed to diesel engines running at low ambient temperature conditions concerns undesirable exhaust emissions, such as “white smoke.” White smoke can be attributed to the release of unburned hydrocarbons as a result of misfire or incomplete combustion within the engine. Low temperature ambient air and low engine loads operate to reduce the temperature of the charge mixture within the engine to a degree that the combustion event becomes unstable. 
         [0006]    Diesel engines must also be designed to combat unburned soot particles resulting from incomplete combustion. As such, most diesel engines feature a diesel particulate filter (DPF), i.e., a device designed to collect the particulate matter. However, as the quantity of particulate matter increases in the DPF, the DPF must be cleaned to restore its operability. The process of removing accumulated particulate matter from the DPF is most commonly referred to as regeneration. Regeneration involves the process of increasing the temperature of the DPF to about 550 degrees Celsius, such that the particulate matter combusts or burns. Typically, however, such a temperature is only achieved during high load and high engine speed conditions. As a result, when diesel engines operate at low loads, fuel may be injected in small amounts, and the temperature of the exhaust gas falls below regeneration levels. 
         [0007]    Manufacturers have proposed various technologies for elevating exhaust gas temperatures to a level suitable for carrying out regeneration. For instance, it is known in the art to include catalysts for oxidizing the unburned components in the exhaust gas in order to elevate the exhaust gas temperature. Additionally, the exhaust gas temperature can be increased by a process known as post-injection. Post-injection refers to the method of providing additional fuel in the combustion chamber or exhaust gas system. The additional fuel does not burn in the engine cylinder, but rather, oxidizes with catalysts disposed in the exhaust pipe in order to increase exhaust gas temperature. Nevertheless, following a cold start, the engine may have to operate for over 100 seconds before a sufficient amount of heat energy is generated in order to initiate catalytic activity. To reduce this time, heating devices may be provided to introduce additional heat in the exhaust path. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with the present invention, a closed loop heating system designed to enhance diesel engine performance is provided. The closed loop heating system comprises an intake air heater adapted to accelerate the heating of exhaust gas in order to aid DPF regeneration. In response to a predetermined set of parameters pertaining to DPF regeneration, an engine control module (ECM) sends a representative signal to a high current control module (HCCM), thereby activating the intake air heater. As such, the intake air heater increases the engine load via an engine alternator, which in turn, enables the engine to burn more fuel by the process of combustion. The heat generated from the combustion event helps promote increased exhaust gas temperatures in order to support DPF regeneration. 
         [0009]    Once the exhaust gas attains a predetermined temperature, the intake air heater is deactivated. However, in response to various factors necessitating DPF regeneration, the ECM activates additional exhaust gas temperature increasing means integrally adapted within the closed loop heating system. 
         [0010]    The present invention further provides a method for enhancing diesel engine performance. More particularly, this invention presents a novel method of employing a heating device in order to load an alternator to support the regeneration of particulate matter accumulated in a diesel particulate filter. The method generally comprises the following steps: 1) sensing the temperature of exhaust gas emitted from the diesel engine; and 2) heating engine intake air via the heating device when the exhaust gas temperature is below a predetermined temperature. In accordance with the preferred embodiments, the heating device is operable to increase engine load via the alternator, wherein the increased engine load increases exhaust gas temperature. Accordingly, the increased exhaust gas temperature operates to support the regeneration of particulate matter trapped in the diesel particulate filter. 
         [0011]    In an exemplary embodiment, the method can further include elevating exhaust gas temperatures by way of introducing additional unburned fuel in an exhaust pipe of the diesel engine. In one aspect, the additional unburned fuel can be introduced when the exhaust gas temperature is within a predetermined range. Alternatively, the additional unburned fuel can be introduced when the diesel particulate filter accumulates a predetermined quantity of particulate matter therein. 
         [0012]    One advantage of the present invention is that the intake air heater is modified to support longer durations of 100 percent duty cycle in order to assist loading the alternator during DPF regeneration. 
         [0013]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic block diagram illustrating a closed loop heating system according to a preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Referring generally to  FIG. 1 , a closed loop heating system  10  in accordance with the invention is illustrated as including an intake air heater  12  mounted to an intake manifold (not shown) of a diesel engine E. The diesel engine E comprises a combustion chamber (not shown) having fuel injection nozzles (not shown) for injecting fuel therein, wherein the injected fuel mixes with hot compressed air. In this manner, the air/fuel mixture burns within the combustion chamber, and the resulting exhaust gasses are discharged into an exhaust pipe  20 . 
         [0016]    The exhaust pipe  20  is adapted to transport the exhaust gas to an exhaust gas aftertreatment device  22  comprising a diesel oxidation catalyst (DOC)  24  disposed upstream of a diesel particulate filter (DPF)  26 . The DOC  24  can include one of many structures known in the art, wherein a heat-resistant ceramic member such as, but not limited to, a cordierite honeycomb shaped body supports an oxidation catalyst on its surface. Analogously, the DPF  26  is a ceramic filter comprising one of many structures known in the art, such as, but not limited to, a cordierite honeycomb shaped body having a plurality of passages, the inlets and outlets of the adjoining passages being alternately closed. 
         [0017]    As gas passes through the exhaust gas aftertreatment device  22 , the DOC  24  oxidizes the hydrocarbons in the exhaust gases via a catalytic reaction, thereby increasing the temperature of the exhaust gas. Advantageously, the elevated exhaust gas temperature assists regeneration by increasing the temperature of the DPF  26 , and as a result, the particulate matter trapped therein is removed. 
         [0018]    Nevertheless, at light engine loads and/or low ambient temperatures, regeneration cannot occur if the temperature of the exhaust gas is insufficiently high to activate the catalytic reaction. Therefore, in order to prevent consequences attributed to considerable particulate matter buildup in the DPF  26 , such as increased back pressure leading to reduced performance of the engine E, the exhaust gas temperature must be elevated. Numerous means known in the art can be employed for raising exhaust gas temperatures. However, the manner in which the temperature of the exhaust gas is elevated is directly dependent on the current exhaust gas temperature. 
         [0019]    In order to monitor the temperature of the exhaust gas, one or more exhaust gas temperature sensors  28  can be disposed in the exhaust pipe  20 . For instance, the exhaust gas temperature sensors  28 A and  28 B can be disposed upstream and/or downstream with respect to the DPF  26 . Alternatively, only one exhaust gas temperature sensor  28 A or  28 B may be provided upstream or downstream of the DPF  26 , wherein the temperature of the DPF  26  may be estimated from the output of the exhaust gas temperature sensor  28 . The exhaust gas temperature sensors are operatively connected to an electronic control module (ECM)  16 , wherein the exhaust gas temperature sensors are operatively configured to detect the temperatures of the inlet and outlet gas of the DPF  26 , and output the respective temperatures to the ECM  16 . Depending on a predetermined set of parameters, the ECM  16  may prompt the activation of one or more components integrally connected to the diesel engine E in order to carry out DPF regeneration. 
         [0020]    The ECM  16  is operatively connected to the intake air heater  12  via a high current control module (HCCM)  18 . Accordingly, when the ECM  16  detects that the exhaust gas temperature is below a predetermined temperature (e.g., but not limited to, 250 degrees Celsius), the ECM  16  commands the HCCM  18  to activate the intake air heater  12 . However, it should be noted that since the HCCM  18  draws a considerable amount of current, an upper limit is imposed. In this manner, the HCCM  18  is designed such that if it exceeds a predetermined temperature (e.g., but not limited to, 90 degrees Celsius), its circuit board automatically shuts off. As a result, any request received by the HCCM  18  from the ECM  16  to activate the intake air heater  12  will be denied. 
         [0021]    As illustrated in  FIG. 1 , the intake air heater  12  is directly linked to an alternator  30 . The alternator  30  is mechanically linked with the diesel engine E. Upon activation, the intake air heater  12  draws a considerable amount of current, and applies an electrical load to the alternator  30 . Yet due to the additional current dissipated from the engine&#39;s E battery  32 , the alternator  30  increases engine load demand in order to recharge the battery  32 . As the power level of the engine increases, additional fuel is combusted, thereby generating additional heat. Accordingly, this additional heat helps elevate the temperature of the exhaust gas, which in turn, aids DPF regeneration. 
         [0022]    Once the exhaust gas has attained a predetermined elevated temperature (e.g., 250 degrees Celsius or greater), the ECM  16  triggers a command to the HCCM  18  to deactivate the intake air heater  12 . As such, the intake air heater  12  is only operable when the exhaust gas is below a predetermined temperature (e.g., but not limited to, 250 degrees Celsius), which generally occurs at low ambient temperatures (e.g., but not limited to, 10 degrees Celsius and below). While the length of time in which the intake air heater  12  is engaged is relatively short, the overall time period is dependent, in part, on certain factors. For example, at increased engine loads and ambient temperatures, the duration of intake air heater activity is reduced. 
         [0023]    In addition to utilizing the intake air heater  12 , the ECM  16  enables alternative means for assisting in DPF regeneration. That is, since the engine has various operating states, the ECM  16  is functionally adapted to increase exhaust gas temperatures via additional means in response to certain factors pertaining to DPF regeneration. For instance, when the ECM  16  detects an exhaust gas temperature falling within a predetermined temperature range (e.g., but not limited to, 250 to 600 degrees Celsius), the ECM  16  triggers exhaust gas temperature increasing means such as, but not limited to, post-injection. In post-injection operation, unburned fuel that is injected into the exhaust pipe  20  is oxidized by the DOC  24 , thereby elevating exhaust gas temperatures. Alternatively, the ECM  16  can be configured to activate post-injection (or other suitable exhaust gas temperature increasing means) upon detection of a predetermined quantity of particulate matter trapped in the DPF  26 . Furthermore, electrical heating devices such as, but not limited to, glow plugs, may be employed for increasing exhaust gas temperatures. 
         [0024]    The present invention further provides a method for enhancing performance of a diesel engine E. The method comprises: sensing exhaust gas temperature via means such as the sensors  28 A,  28 B discussed above; and activating a heating device, such as, but not limited to, the intake air heater  12  discussed above, to increase intake air when the exhaust gas temperature is below a predetermined temperature. The intake air heater  12  is operatively connected to the alternator  30  discussed above, wherein the alternator  30  is mechanically linked to the diesel engine E. When activated, the intake air heater  12  draws electrical energy from a power source such as the battery  32  discussed above, and as a result, increases alternator load demand for recharging the battery  32 . The increased alternator load demand increases engine load, which increases the exhaust gas temperature. The increased exhaust gas temperature is operative to assist in regeneration of particulate matter accumulated in a mechanism for collecting particulate matter such as, but not limited to, the diesel particulate filter (DPF)  26  discussed above. 
         [0025]    Preferably, the method further comprises deactivating the intake air heater  12  when the exhaust gas temperature attains a temperature equal to, or greater than, the predetermined temperature. In an exemplary embodiment, the method can include introducing fuel to the exhaust gas when the exhaust gas temperature is within a predetermined temperature range, wherein the fuel is operative to elevate the exhaust gas temperature. Additionally, the method can include introducing the fuel when the DPF  26  accumulates a predetermined quantity of particulate matter. 
         [0026]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.