Patent Publication Number: US-6209500-B1

Title: Cold start fuel preheat system for internal combustion engine

Description:
BACKGROUND OF THE INVENTION 
     1. Field Of the Invention 
     The present invention relates generally to internal combustion engines and, more specifically, to a cold start fuel preheat system for improved atomization of fuel in an internal combustion engine. 
     2. Description of the Related Art 
     It is known to provide a fuel-air mixture for an internal combustion engine, which needs good preparation of liquid fuel such as gasoline and air to burn efficiently. This is accomplished by a fuel injection system comprising a carburetor or fuel injector. The ideal fuel-air mixture delivered to the intake manifold should be a homogeneous mixture of minute fuel particles in air to facilitate subsequent vaporization of the liquid fuel. The mixture should have composition or strength to develop maximum economy for each condition of engine operation. When an engine is burning such an ideal fuel-air mixture, maximum combustion of the fuel is achieved while smoke and unburned fuel in the exhaust are held to a minimum. 
     Cold fuel temperatures are known to result in severe degradation of atomization quality and fuel vaporization rate. These effects result in the need to utilize enrichment strategies to guarantee stable operation of the cold engine. Enrichment strategies require that fuel in excess of that required for normal engine operation be injected to ensure that enough fuel vapor is available in the combustion chamber. 
     The need for improving the fuel-air mixture in the combustion chamber has been recognized for many years. One attempted solution to this need has been to install electrically heated fuel injectors in the internal combustion engine to preheat and improve atomization of the fuel. However, there is still a need in the art, during cold start, to improve fuel atomization and vaporization, reduce hydrocarbon (HC) emissions, and reduce fuel consumption. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is cold start fuel preheat system for an internal combustion engine including a housing and a fuel rail extending through the housing to deliver fuel to the internal combustion engine. The cold start fuel preheat system also includes a phase transform material disposed in the housing and about the fuel rail. The cold start fuel preheat system further includes a mechanism for heating the phase transform material such that the phase transform material stores the heat and transfers the stored heat to the fuel during cold start of the internal combustion engine. 
     One feature of the present invention is that a cold start fuel preheat system is provided for improved atomization of fuel in an internal combustion engine. Another feature of the present invention is that the cold start fuel preheat system improves vaporization of incoming fuel spray and enhances mixing of the charge. Yet another feature of the present invention is that the cold start fuel preheat system reduces, during “cold start”, enrichment requirements by preheating the fuel to a temperature that ensures good atomization quality and promotes fuel vaporization. A further feature of the present invention is that the cold start fuel preheat system heats fuel sufficiently to overcome cold start fuel atomization issues without excessive heating and an energy storage solution is utilized to recover energy from the engine coolant to heat the fuel during subsequent cold start operations. 
     Other features and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description when considered in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a cold start fuel preheat system, according to the present invention, illustrated in operational relationship with an internal combustion engine. 
     FIG. 2 is a fragmentary elevational view of the cold start fuel preheat system of FIG.  1 . 
     FIG. 3 is an exploded perspective view of another embodiment, according to the present invention, of the cold start fuel preheat system of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Referring to the drawings and in particular FIG. 1, one embodiment of an apparatus or cold start fuel preheat system  10 , according to the present invention, is illustrated in operational relationship with an internal combustion engine, generally indicated at  12 . The internal combustion engine  12  includes an engine block  14  having a plurality of combustion chambers (not shown) for combusting a fuel and air mixture. The internal combustion engine  12  includes a fuel rail  16  extending longitudinally and fluidly communicating with fuel injectors (not shown) for the combustion chambers. The fuel rail  16  may include a plurality of fins  17  attached to an exterior surface thereof to conduct heat transfer during cold start in a manner to be described. The internal combustion engine  12  also includes an exhaust manifold  18  operatively connected to the engine block  14  for receiving exhaust gases therefrom. The exhaust manifold  16  has a plurality of pipes  19  operatively connected to the individual combustion chambers. The cold start fuel preheat system  10  is disposed about the fuel rail  16  and mounted to the internal combustion engine  12  over the pipes  19  of the exhaust manifold  18 . The cold start fuel preheat system  10  heats the fuel during cold start of the internal combustion engine  12  in a manner to be described in which a fuel injector (not shown) sprays fuel into a primary flow or inlet runner (not shown). This fuel mixes with the air flowing through the primary inlet runner and the fuel-air mixture then passes through an inlet valve (not shown) and into a combustion chamber where the mixture is ignited by a spark igniter (not shown). 
     As illustrated in FIGS. 1 and 2, the cold start fuel preheat system  10  includes an insulated or thermal housing  20  placed across the pipes  19  of the exhaust manifold  18 . The housing  20  is generally rectangular in shape, but may have any suitable shape. The housing  20  may include a first or lower half shell  22  and a second or upper half shell  24 . The lower half shell  22  includes at least one, preferably a plurality of pockets  26  therein. The pockets  26  are spaced longitudinally to accommodate the pipes  18  therebetween. The upper half shell  24  is secured to the lower half shell  22  by suitable means such as welding. It should be appreciated that the fuel rail  16  extends longitudinally through the housing  20  and that the fins  17  are disposed in the pockets  26  of the housing  20 . It should also be appreciated that the housing  20  is placed on or near the engine  12  and, as illustrated in FIG. 2, receives heat from the exhaust manifold  18 . 
     The cold start fuel preheat system  10  also includes a phase transform material disposed in the housing  20  between the lower half shell  22  and the upper half shell  24 . The phase transform material  28  is in the form of phase change energy storage pellets. The pellets are made of a suitable material such as a salt encapsulated in a polymer bead. The salt inside the polymer bead stores energy by converting from a solid phase to a liquid phase and heat can be removed by converting from the liquid phase to the solid phase. The phase transform material  28  stores thermal energy for use during cold start operation in a manner to be described. The phase transform material is commercially available as encapsulated PCM TH 89  from PCM Thermal Solutions, Naperville, Ill. It should be appreciated that the phase transform material  28  can deliver significant amounts of heat at nearly constant temperature. It should also be appreciated that the volume of phase transform material  28  inside the housing  20  is based on size and warm-up requirements of the engine  12 . 
     The cold start fuel preheat system  10  further includes an engine coolant line  30  having an inlet  32  extending into one end of the housing  20  and an outlet  34  extending into the other end of the housing  20 . The engine coolant line  30  is discontinuous between the inlet  32  and outlet  34  to allow engine coolant to circulate through the phase transform material  28  in the housing  20 . The inlet  32  is fluidly connected to a heater core (not shown) and the outlet  34  is fluidly connected to a radiator (not shown). It should be appreciated that the upper half shell  24  and lower half shell  22  are sealed together by suitable means to prevent leakage of the engine coolant from the housing  20 . It should also be appreciated that the housing  20  is of a sufficient size to accommodate the fuel rail  16 , phase transform material  28  and engine coolant line  30 . It should further be appreciated that the engine coolant line  30  may be continuous and include a plurality of coils between the inlet  32  and outlet  34  similar to that described in connection with FIG.  3 . 
     In operation of the cold start fuel preheat system  10 , under warmed-up operating conditions, the engine coolant such as water enters through the inlet  32  of the engine coolant line  30  and circulates through the housing  20 . The engine coolant provides the thermal energy necessary to heat the phase transform material  28  that stores thermal energy for use during later cold start operation. As the coolant circulates, it will transfer energy to the phase transform material  28 . Control valves (not shown) can be used to control the flow of coolant through the housing  20  both during cold start operation and normal operating temperatures to prevent unnecessary removal of heat from the phase transform material  28  by the cold engine coolant and during hot operation to prevent overheating of the phase transform material  28 . 
     During cold start operation of the engine  12 , fuel from the fuel tank (not shown) may be allowed to enter the cold start fuel preheat system  10  via a fuel pump (not shown) and be heated to the appropriate temperature by the phase transform material  28  as it flows through the fuel rail  16 . Heat is removed from the phase transform material  28  by heat transfer through the fins  17  and fuel rail  16  to the cold fuel flowing through the fuel rail  16 . The cold start fuel preheat system  10  delivers the warmed fuel to the fuel injectors at a sufficiently high temperature to ensure good atomization quality, thereby minimizing transient air-fuel ratio excursions during cold engine operation. It should be appreciated that improved air-fuel ratio control during cold start will reduce hydrocarbon emission and reduce or eliminate the need for cold start enrichment. It should also be appreciated that heat removed from the cold start fuel preheat system  10  during cold engine operation is replaced by circulation of engine coolant through the system  10  after the engine  12  reaches its normal operating condition. 
     Referring to FIG. 3, another embodiment  110 , according to the present invention, of the cold start fuel preheat system  10  is illustrated. Like parts of the cold start fuel preheat system  10  have like reference numerals increased by one hundred ( 100 ). In this embodiment, the cold start fuel preheat system  110  includes the housing  120  remotely located from the engine  12 . The cold start fuel preheat system  110  also includes the fuel rail  116  extending into the upper half shell  124  and having a plurality of coils  140  spaced longitudinally and exiting through the upper half shell  124 . The cold start fuel preheat system  110  includes the engine coolant line  130  extending into the lower half shell  122  and having a plurality of coils  142  between the inlet  132  and the outlet  134 . The operation of the cold start fuel preheat system  110  is similar to the cold start fuel preheat system  10 . It should be appreciated that the fuel line  116  has a sufficient number of coils  140  to ensure that adequate warm fuel is available during cold start and engine warm-up. It should also be appreciated that the housing  120  is of a sufficient size to accommodate the coils  140  of the fuel rail  116 , the coils  142  of the engine coolant line  130  and enough phase transform material  128  to ensure that adequate thermal energy is available to keep the fuel temperature at the correct level for cold engine operation. It should further be appreciated that the coils  142  of the engine coolant line  130  provide thermal energy from the engine during fully warmed-up operation. It should still further be appreciated that the housing  120  may be located as near the engine  12  as possible to minimize the volume of cold fuel delivered to the engine  12  during cold start operation. 
     Alternatively, the cold start fuel preheat system  110  may use exhaust gas from the engine  12  to supply the thermal energy to the system  110  instead of using engine coolant or replacing the coils  140  of the fuel rail  116  with a spherical or cylindrical vessel to contain the fuel. Also, a thermostatically controlled valve may be incorporated to bleed cold fuel from the fuel rail  116  and replace it with warm fuel from the housing to ensure that the fuel is available at the fuel injectors during cold start. 
     Accordingly, the cold start fuel preheat system  10 , 110  allows preheated fuel to be available to a cold engine at key-on (i.e., no time delay for heating the fuel or the system). The cold start fuel preheat system  10 , 110  does not require an additional energy source for operation. The cold start fuel preheat system  10 , 110  is a passive heat transfer mechanism and the only mechanical components are associated with coolant flow through the system, reducing complexity. 
     The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.