Abstract:
A fuel injection system for an internal combustion engine is disclosed, the fuel injection system including a plurality of injectors, wherein each of the injectors is adapted to inject at least one of an alternative fuel and a fossil fuel over a full range of operating conditions of the engine.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an internal combustion engine, and more particularly to a multi-fuel multi-injection system for an internal combustion engine which is capable of injecting a fossil fuel and an alternative fuel over a full range of operating conditions of the engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    The automotive industry is continually researching the combustion process of an internal combustion engine to improve a fuel economy and emissions thereof. To optimize performance of the engine, it is important to be able to control the engine on a cycle-to-cycle basis. For engines operating without a conventional spark ignition, commonly known as the homogenous charge compression ignition (HCCI) mode, the main challenge is to maintain a stable start of combustion (SOC) when the engine is operated at steady state and transient conditions. The instability of the SOC is mainly due to difficulties in the control of in-cylinder air-to-fuel mixture temperature on a cycle-to-cycle basis. 
         [0003]    Presently, prior art engines utilize an intake heater to control intake air temperature and/or an amount of residual exhaust gas (REG) to regulate engine in-cylinder air-to-fuel mixture temperature. However, a disadvantage of using the intake heater is its slow response time caused by a large time constant of the heater and a transportation delay from the heater to the cylinder. The slow response time results in inaccurate temperature regulation during the transient operation of the engine. On the other hand, using REG provides expeditious regulation for in-cylinder air-to-fuel mixture temperature control. However, a rate of in-cylinder residual exhaust gas is uncontrollable, leading to SOC and indicated mean effective pressure (IMEP) variation. 
         [0004]    Furthermore, advancements have been made in the various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder of the engine. Such advancements include the introduction of multi-injection fuel systems. One multi-injection fuel system is the dual-injection single-fuel system. The dual-injection single-fuel system includes two fuel injectors for each cylinder. One is a direct injector and the other is a port fuel injector. The dual-injection single-fuel system is designed to improve full load performance of the engine at high engine speed operating conditions. 
         [0005]    Another multi-injection fuel system is the dual-injection dual-fuel system. The dual-injection dual-fuel system utilizes two different, but comparable fuels. Typically, due to its high octane quality, ethanol has been used in conjunction with gasoline in a dual-injection dual-fuel system. The benefit of the dual-injection dual-fuel system is the capability to increase the combustion efficiency, while suppressing engine knock. The benefit is derived from directly injecting higher octane ethanol fuel into a combustion chamber of the engine. The ethanol has substantial air charge cooling, resulting from its high heat of vaporization. However, the prior art dual-injection dual-fuel system is limited to injecting gasoline into an intake port of the engine. 
         [0006]    It is desirable to produce an internal combustion engine including a plurality of fuel injectors adapted to inject a fossil fuel and an alternative fuel, wherein an efficiency thereof is maximized, and emissions and knock thereof are minimized. 
       SUMMARY OF THE INVENTION 
       [0007]    In concordance and agreement with the present invention, an internal combustion engine including a plurality of fuel injectors adapted to inject a fossil fuel and an alternative fuel, wherein an efficiency thereof is maximized, and emissions and knock thereof are minimized, has surprisingly been discovered. 
         [0008]    In one embodiment, the fuel injection system comprises a first injector adapted to receive at least one of a first stream of a first fuel from a source of the first fuel and a first stream of a second fuel from a source of the second fuel, wherein the first injector injects at least one of the first stream of the first fuel and the first stream of the second fuel into an intake path of a cylinder; a second injector adapted to receive at least one of a second stream of a first fuel from the source of the first fuel and a second stream of the second fuel from the source of the second fuel, wherein the second injector injects at least one of the second stream of the first fuel and the second stream of the second fuel into the cylinder; and a control system adapted to control a combustion in the cylinder over a full range of operating conditions of an engine, wherein an amount of at least one of the first fuel and the second fuel is provided to the cylinder over the full range of operating conditions of the engine. 
         [0009]    In another embodiment, the fuel injection system comprises a first injector adapted to receive a first stream of a first fuel from a source of the first fuel and a first stream of a second fuel from a source of the second fuel, wherein the first injector injects at least one of the first stream of the first fuel and the first stream of the second fuel into an intake path of a cylinder; and a second injector adapted to receive a second stream of the first fuel and a second stream of the second fuel, wherein the second injector injects the at least one of the second stream of the first fuel and the second stream of the second fuel into the cylinder. 
         [0010]    In another embodiment, the fuel injection system comprises a first injector adapted to receive a first stream of a first fuel from a source of the first fuel, wherein the first injector injects the first stream of the first fuel into an intake path of a cylinder; a second injector adapted to receive a first stream of a second fuel from a source of the second fuel, wherein the second injector injects the first stream of the second fuel into the intake path of the cylinder; a third injector adapted to receive a second stream of the first fuel, wherein the third injector injects the second stream of the first fuel into the cylinder; and a fourth injector adapted to receive a second stream of the second fuel, wherein the fourth injector injects the second stream of the second fuel into the cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above, as well as other objects and advantages of the invention, will become readily apparent to those skilled in the art from reading the following detailed description of various embodiments of the invention when considered in the light of the accompanying drawings in which: 
           [0012]      FIG. 1  is a schematic diagram of a cylinder of an internal combustion engine including a direct injector and a port fuel injector according to an embodiment of the invention; 
           [0013]      FIG. 2  is a schematic diagram of a cylinder according to another embodiment of the invention; 
           [0014]      FIG. 3  is a schematic diagram of a cylinder according to another embodiment of the invention; 
           [0015]      FIG. 4  is a schematic diagram of a cylinder according to another embodiment of the invention; and 
           [0016]      FIG. 5  is a schematic diagram of a cylinder according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. 
         [0018]      FIG. 1  shows an injection system  8  for a cylinder  10  of an internal combustion engine according to an embodiment of the invention. It is understood that the internal combustion engine can have additional cylinders as desired. The cylinder  10  has a hollow interior with a piston  12  slideably disposed therein. The piston  12  and a wall of the cylinder  10  cooperate to define a combustion chamber  14  therebetween. The cylinder  10  includes an intake path  16  and an exhaust path  18 . It is understood that the cylinder can include additional intake paths and exhaust paths if desired. 
         [0019]    In the embodiment shown, the intake path  16  of the cylinder  10  includes a first injector  20 . The first injector  20  is a so-called port fuel injector (PFI) adapted to inject a first stream of a first fuel  21  into the intake path  16 . As shown, the first injector  20  includes a fluid inlet  22  and a spaced apart fluid outlet nozzle  23 . The fluid inlet  22  is in fluid communication with a source of the first fuel  25 . The fluid outlet  23  is in fluid communication with the intake path  16  of the cylinder  10 . It is understood that the first fuel  21  can be any fuel such as an alternative fuel and a fossil fuel, for example. As used herein, the term alternative fuel refers to an alcohol-based fuel in a liquid state such as an ethanol, a methanol, a butanol, any blend thereof, and the like, for example, and a non-alcohol based fuel in a liquid state such as a liquefied petroleum gas, a liquefied hydrogen, a compressed hydrogen, a compressed natural gas, a liquefied natural gas, a biodiesel, and the like, for example. It is also understood that the term fossil fuel, as used herein, refers to a fuel in a liquid state such as a gasoline, a gasoline blend, a diesel, a diesel blend, and the like, for example. The first injector  20  delivers injected fuel in proportion to a pulse width of a signal received from a control system  26  via at least one electronic driver. The intake path  16  permits a flow of air from a throttle body (not shown) and a flow of the first fuel  25  therethrough. A valve  28  is disposed in the intake path  16  of the cylinder  10  to selectively open and close the intake path  16 . The exhaust path  18  permits a flow of a gaseous exhaust therethrough. A valve  29  is disposed in the exhaust path  18  of the cylinder  10  to selectively open and close the exhaust path  18 . 
         [0020]    The cylinder  10  includes a second injector  30 . The second injector  30  is a so-called direct injector (DI) adapted to inject a first stream of a second fuel  31  into the combustion chamber  14 . Although the second injector  30  illustrated is disposed in a side wall of the cylinder  10 , it is understood that the second injector  30  can be disposed elsewhere in the cylinder  10  such as overhead of the piston  12  and near the intake path  16 , for example. As shown, the second injector  30  includes a fluid inlet  32  and a spaced apart fluid outlet nozzle  34 . The fluid inlet  32  is in fluid communication with a source of the second fuel  37 . Although the source of the first fuel  25  and the source of the second fuel  37  shown are separate, it is understood that the first fuel  21  and the second fuel  31  can be stored in a single tank and separated by reforming a first fuel/second fuel blend using a fuel separator. The fluid outlet  34  is in fluid communication with the combustion chamber  14 . It is understood that the second fuel  31  can be any fuel such as an alternative fuel and a fossil fuel, for example. The second injector  30  delivers injected fuel in proportion to a pulse width of a signal received from the control system  26  via at least one electronic driver. 
         [0021]    The control system  26  is adapted to monitor engine operating parameters via various sensors (not shown) to control an injection timing, an injection duration, and an injection rate of the injectors  20 ,  30 , and a fuel ratio of the first fuel  21  to the second fuel  31 . Accordingly, the instantaneous demand of the ratio of each fuel and injection type and any combinations thereof can be controlled in real time by the control system  26 . An ignition coil  38  may be disposed in the combustion chamber  14  of the cylinder  10 . The ignition coil  38  enhances an ignition timing control of the engine at certain conditions such as during cold start and low load operation, for example. 
         [0022]      FIG. 2  shows another embodiment of the invention which includes a fuel injection system similar to that shown in  FIG. 1 . Reference numerals for similar structure in respect of the description of  FIG. 1  are repeated in  FIG. 2  with a prime (′) symbol. 
         [0023]      FIG. 2  shows an injection system  8 ′ for a cylinder  10 ′ of an internal combustion engine according to an embodiment of the invention. It is understood that the internal combustion engine can have additional cylinders as desired. The cylinder  10 ′ has a hollow interior with a piston  12 ′ slideably disposed therein. The piston  12 ′ and a wall of the cylinder  10 ′ cooperate to define a combustion chamber  14 ′ therebetween. The cylinder  10 ′ includes an intake path  16 ′ and an exhaust path  18 ′. It is understood that the cylinder  10 ′ can include additional intake paths and exhaust paths if desired. 
         [0024]    In the embodiment shown, the intake path  16 ′ includes a first injector  50 . The first injector  50  is a so-called port fuel injector (PFI) adapted to inject a first stream of a first fuel  21 ′ and a first stream of a second fuel  31 ′ into the intake path  16 ′. As shown, the first injector  50  includes a first fluid inlet  52  and a spaced apart first fluid outlet nozzle  54 . The first fluid inlet  52  is in fluid communication with a source of the first fuel  25 ′. The first fluid outlet  54  is in fluid communication with the intake path  16 ′ of the cylinder  10 ′. It is understood that the first fuel  21 ′ can be any fuel such as an alternative fuel and a fossil fuel, for example. The first injector  50  further includes a second fluid inlet  56  and a spaced apart second fluid outlet nozzle  58 . The second fluid inlet  56  is in fluid communication with a source of the second fuel  37 ′. Although the source of the first fuel  25 ′ and the source of the second fuel  37 ′ shown are separate, it is understood that the first fuel  21 ′ and the second fuel  31 ′ can be stored in a single tank and separated by reforming a first fuel/second fuel blend using a fuel separator. The second fluid outlet  58  is in fluid communication with the intake path  16 ′ of the cylinder  10 ′. It is understood that the second fuel  31 ′ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0025]    The first injector  50  delivers injected fuel in proportion to a pulse width of a signal received from a control system  26 ′ via at least one electronic driver. The intake path  16 ′ permits a flow of air from a throttle body (not shown) and a flow of the first fuel  21 ′ and a flow of the second fuel  31 ′ therethrough. A valve  28 ′ is disposed in the intake path  16 ′ of the cylinder  10 ′ to selectively open and close the intake path  16 ′. The exhaust path  18 ′ permits a flow of a gaseous exhaust therethrough. A valve  29 ′ is disposed in the exhaust path  18 ′ of the combustion chamber  14 ′ to selectively open and close the exhaust path  18 ′. 
         [0026]    The cylinder  10 ′ includes a second injector  60 . The second injector  60  is a so-called direct injector (DI) adapted to inject a second stream of the first fuel  21 ′ and a second stream of the second fuel  31 ′ into the combustion chamber  14 ′. Although the second injector  60  illustrated is disposed in a side wall of the cylinder  10 ′, it is understood that the second injector  60  can be disposed elsewhere in the cylinder  10 ′ such as overhead of the piston  12 ′ and near the intake path  16 ′, for example. As shown, the second injector  60  includes a first fluid inlet  62  and a spaced apart first fluid outlet nozzle  64 . The first fluid inlet  62  is in fluid communication with the source of the first fuel  25 ′. The first fluid outlet  64  is in fluid communication with the combustion chamber  14 ′. The second injector  60  further includes a second fluid inlet  66  and a spaced apart second fluid outlet nozzle  68 . The second fluid inlet  66  is in fluid communication with the source of the second fuel  37 ′. The second fluid outlet  68  is in fluid communication with the combustion chamber  14 ′. The second injector  60  delivers injected fuel in proportion to a pulse width of a signal received from the control system  26 ′ via at least one electronic driver. 
         [0027]    The control system  26 ′ is adapted to monitor engine operating parameters via various sensors (not shown) to control an injection timing, an injection duration, and an injection rate of the injectors  50 ,  60 , and a fuel ratio of the first fuel  21 ′ to the second fuel  31 ′. Accordingly, the instantaneous demand of the ratio of each fuel and injection type and any combinations thereof can be controlled in real time by the control system  26 ′. An ignition coil  38 ′ may be disposed in the combustion chamber  14 ′ of the cylinder  10 ′. The ignition coil  38 ′ enhances an ignition timing control of the engine at certain conditions such as during cold start and low load operation, for example. 
         [0028]      FIG. 3  shows another embodiment of the invention which includes a fuel injection system similar to that shown in  FIGS. 1 and 2 . Reference numerals for similar structure in respect of the description of  FIGS. 1 and 2  are repeated in  FIG. 3  with a prime (″) symbol. 
         [0029]      FIG. 3  shows an injection system  8 ″ for a cylinder  10 ″ of an internal combustion engine according to an embodiment of the invention. It is understood that the internal combustion engine can have additional cylinders as desired. The cylinder  10 ″ has a hollow interior with a piston  12 ″ slideably disposed therein. The piston  12 ″ and a wall of the cylinder  10 ″ cooperate to define a combustion chamber  14 ″ therebetween. The cylinder  10 ″ includes an intake path  16 ″ and an exhaust path  18 ″. It is understood that the cylinder  10 ″ can include additional intake paths and exhaust paths if desired. 
         [0030]    In the embodiment shown, the intake path  16 ″ includes a first injector  80  and a second injector  82 . The first injector  80  and the second injector  82  are so-called port fuel injectors (PFI) adapted to inject a first stream of a first fuel  21 ″ and a first stream of a second fuel  31 ″, respectively, into the intake path  16 ′. As shown, the first injector  80  includes a fluid inlet  84  and a spaced apart fluid outlet nozzle  86 . The fluid inlet  84  is in fluid communication with a source of the first fuel  25 ″. The fluid outlet  86  is in fluid communication with the intake path  16 ″ of the cylinder  10 ″. It is understood that the first fuel  21 ″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0031]    The second injector  82  includes a fluid inlet  90  and a spaced apart fluid outlet nozzle  92 . The fluid inlet  90  is in fluid communication with a source of the second fuel  37 ″. Although the source of the first fuel  25 ″ and the source of the second fuel  37 ″ shown are separate, it is understood that the first fuel  21 ″ and the second fuel  31 ″ can be stored in a single tank and separated by reforming a first fuel/second fuel blend using a fuel separator. The fluid outlet  92  is in fluid communication with the intake path  16 ″ of the cylinder  10 ″. It is understood that the second fuel  31 ″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0032]    The first injector  80  and the second injector  82  deliver injected fuel in proportion to a pulse width of a signal received from a control system  26 ″ via at least one electronic driver. The intake path  16 ″ permits a flow of air from a throttle body (not shown) and a flow of the first fuel  21 ″ and a flow of the second fuel  31 ″ therethrough. A valve  28 ″ is disposed in the intake path  16 ″ of the cylinder  10 ″ to selectively open and close the intake path  16 ′. The exhaust path  18 ″ permits a flow of a gaseous exhaust therethrough. A valve  29 ″ is disposed in the exhaust path  18 ″ of the cylinder  10 ″ to selectively open and close the exhaust path  18 ″. 
         [0033]    The cylinder  10 ″ includes a third injector  100  and a fourth injector  102 . The third injector  100  and the fourth injector  102  are so-called direct injectors (DI) adapted to inject a second stream of the first fuel  21 ″ and a second stream of the second fuel  31 ″, respectively, into the combustion chamber  14 ″. Although the third injector  100  and the fourth injector  102  illustrated are disposed overhead of the piston  12 ″ near the intake path  16 ″ and in a side wall of the cylinder  10 ″, respectively, it is understood that the third injector  100  and the fourth injector  102  can be disposed elsewhere in the cylinder  10 ″ as desired. As shown, the third injector  100  includes a fluid inlet  104  and a spaced apart fluid outlet nozzle  106 . The fluid inlet  104  is in fluid communication with the source of the first fuel  25 ″. The fluid outlet  106  is in fluid communication with the combustion chamber  14 ″. 
         [0034]    The fourth injector  102  includes a fluid inlet  110  and a spaced apart fluid outlet nozzle  112 . The fluid inlet  110  is in fluid communication with the source of the second fuel  37 ″. The fluid outlet  112  is in fluid communication with the combustion chamber  14 ″. The third injector  100  and the fourth injector  102  deliver injected fuel in proportion to a pulse width of a signal received from the control system  26 ″ via at least one electronic driver. 
         [0035]    The control system  26 ″ is adapted to monitor engine operating parameters via various sensors (not shown) to control an injection timing, an injection duration, and an injection rate of the injectors  80 ,  82 ,  100 ,  102 , and a fuel ratio of the first fuel  21 ″ to the second fuel  31 ″. Accordingly, the instantaneous demand of the ratio of each fuel and injection type and any combinations thereof up to all four injectors  80 ,  82 ,  100 ,  102  can be controlled in real time by the control system  26 ″. An ignition coil  38 ″ may be disposed in the combustion chamber  14 ″ of the cylinder  10 ′. The ignition coil  38 ″ enhances an ignition timing control of the engine at certain conditions such as during cold start and low load operation, for example. 
         [0036]      FIG. 4  shows another embodiment of the invention which includes a fuel injection system similar to that shown in  FIGS. 1 ,  2 , and  3 . Reference numerals for similar structure in respect of the description of  FIGS. 1 ,  2 , and  3  are repeated in  FIG. 4  with a prime (′″) symbol. 
         [0037]      FIG. 4  shows an injection system  8 ′″ for a cylinder  10 ′″ of an internal combustion engine according to an embodiment of the invention. It is understood that the internal combustion engine can have additional cylinders  10 ′″ as desired. The cylinder  10 ′″ has a hollow interior with a piston  12 ′″ slideably disposed therein. The piston  12 ′″ and a wall of the cylinder  10 ′″ cooperate to define a combustion chamber  14 ′″ therebetween. The cylinder  10 ′″ includes an intake path  16 ′″ and an exhaust path  18 ′″. It is understood that the cylinder  10 ′″ can include additional intake paths and exhaust paths if desired. The intake path  16 ′″ is in fluid communication with a throttle body  116  of the engine. Accordingly, the throttle body  116  is in fluid communication with all cylinders  10 ′″ of the engine. The throttle body  116  is adapted to selectively permit a flow of air therethrough. 
         [0038]    In the embodiment shown, the throttle body  116  includes a first injector  120  and a second injector  122  disposed therein. The first injector  120  and the second injector  122  are so-called throttle body injectors (TBI) adapted to inject a first stream of a first fuel  21 ′″ and a first stream of a second fuel  31 ′″, respectively, into the throttle body  116  or upstream of the throttle body  116 . As shown, the first injector  120  includes a fluid inlet  124  and a spaced apart fluid outlet nozzle  126 . The fluid inlet  124  is in fluid communication with a source of the first fuel  25 ′″. The fluid outlet  126  is in fluid communication with the throttle body  116 . It is understood that the first fuel  21 ′″can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0039]    The second injector  122  includes a fluid inlet  130  and a spaced apart fluid outlet nozzle  132 . The fluid inlet  130  is in fluid communication with a source of the second fuel  37 ′″. Although the source of the first fuel  25 ′″ and the source of the second fuel  37 ′″ shown are separate, it is understood that the first fuel  21 ′″ and the second fuel  31 ′″ can be stored in a single tank and separated by reforming a first fuel/second fuel blend using a fuel separator. The fluid outlet  132  is in fluid communication with the throttle body  116 . It is understood that the second fuel  31 ′″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0040]    The first injector  120  and the second injector  122  deliver injected fuel in proportion to a pulse width of a signal received from a control system  26 ′″ via at least one electronic driver. The intake path  16 ′″ permits the flow of air and a flow of the first fuel  21 ′″ and a flow of the second fuel  31 ′″ from the throttle body  116  to the cylinder  10 ′″. A valve  28 ′″ is disposed in the intake path  16 ′″ of the cylinder  10 ′″ to selectively open and close the intake path  16 ′″. The exhaust path  18 ′″ permits a flow of a gaseous exhaust therethrough. A valve  29 ′″ is disposed in the exhaust path  18 ′″ of the cylinder  10 ′″ to selectively open and close the exhaust path  18 ′″. 
         [0041]    The cylinder  10 ′″ includes a third injector  100 ′″ and a fourth injector  102 ′″. The third injector  100 ′″ and the fourth injector  102 ′″ are so-called direct injectors (DI) adapted to inject a second stream of the first fuel  21 ′″ and a second stream of the second fuel  31 ′″, respectively, into the combustion chamber  14 ′″. Although the third injector  100 ′″ and the fourth injector  102 ′″ illustrated are disposed overhead of the piston  12 ′″ near the intake path  16 ′″ and in a side wall of the cylinder  10 ′″, respectively, it is understood that the third injector  100 ′″ and the fourth injector  102 ′″ can be disposed elsewhere in the cylinder  10 ′″ as desired. As shown, the third injector  100 ′″ includes a fluid inlet  104 ′″ and a spaced apart fluid outlet nozzle  106 ′″. The fluid inlet  104 ′″ is in fluid communication with the source of the first fuel  25 ′″. The fluid outlet  106 ′″ is in fluid communication with the combustion chamber  14 ′″. 
         [0042]    The fourth injector  102 ′″ includes a fluid inlet  110 ′″ and a spaced apart fluid outlet nozzle  112 ′″. The fluid inlet  110 ′″ is in fluid communication with the source of the second fuel  37 ′″. The fluid outlet  112 ′″ is in fluid communication with the combustion chamber  14 ′″. The third injector  100 ′″ and the fourth injector  102 ′″ deliver injected fuel in proportion to a pulse width of a signal received from the control system  26 ′″ via at least one electronic driver. 
         [0043]    The control system  26 ′″ is adapted to monitor engine operating parameters via various sensors (not shown) to control an injection timing, an injection duration, and an injection rate of the injectors  100 ′″,  102 ′″,  120 ,  122 , and a fuel ratio of the first fuel  21 ′″ to the second fuel  31 ′″. Accordingly, the instantaneous demand of the ratio of each fuel and injection type and any combinations thereof up to all four injectors  100 ′″,  102 ′″,  120 ,  122  can be controlled in real time by the control system  26 ′″. An ignition coil  38 ′″ may be disposed in the combustion chamber  14 ′″ of the cylinder  10 ′″. The ignition coil  38 ′″ enhances an ignition timing control of the engine at certain conditions such as during cold start and low load operation, for example. 
         [0044]      FIG. 5  shows another embodiment of the invention which includes a fuel injection system similar to that shown in  FIGS. 1 ,  2 ,  3 , and  4 . Reference numerals for similar structure in respect of the description of  FIGS. 1 ,  2 ,  3 , and  4  are repeated in  FIG. 5  with a prime (″″) symbol. 
         [0045]      FIG. 5  shows an injection system  8 ″″ for a cylinder  10 ″″ of an internal combustion engine according to an embodiment of the invention. It is understood that the internal combustion engine can have additional cylinders  10 ″″ as desired. The cylinder  10 ″″ has a hollow interior with a piston  12 ″″ slideably disposed therein. The piston  12 ″″ and a wall of the cylinder  10 ″″ cooperate to define a combustion chamber  14 ″″ therebetween. The cylinder  10 ″″ includes an intake path  16 ″″ and an exhaust path  18 ″″. It is understood that the cylinder  10 ″″ can include additional intake paths and exhaust paths if desired. The intake path  16 ″″ is in fluid communication with a throttle body  116 ″″ of the engine. Accordingly, the throttle body  116 ″″ is in fluid communication with all cylinders  10 ″″ of the engine. The throttle body  116 ″″ is adapted to selectively permit a flow of air therethrough. 
         [0046]    In the embodiment shown, the throttle body  116 ″″ includes a first injector  140  and a second injector  142  disposed therein. The first injector  140  and the second injector  142  are so-called throttle body injectors (TBI) adapted to inject a first stream of a first fuel  21 ″″ and a first stream of a second fuel  31 ″″, respectively, into the throttle body  116 ″″ or upstream of the throttle body  116 ″″. As shown, the first injector  140  includes a fluid inlet  144  and a spaced apart fluid outlet nozzle  146 . The fluid inlet  144  is in fluid communication with a source of the first fuel  25 ″″. The fluid outlet  146  is in fluid communication with the throttle body  116 ″″. It is understood that the first fuel  21 ″″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0047]    The second injector  142  includes a fluid inlet  150  and a spaced apart fluid outlet nozzle  152 . The fluid inlet  150  is in fluid communication with a source of the second fuel  37 ″″. Although the source of the first fuel  25 ″″ and the source of the second fuel  37 ″″ shown are separate, it is understood that the first fuel  21 ″″ and the second fuel  31 ″″ can be stored in a single tank and separated by reforming a first fuel/second fuel blend using a fuel separator. The fluid outlet  152  is in fluid communication with the throttle body  116 ″″. It is understood that the second fuel  31 ″″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0048]    The first injector  140  and the second injector  142  deliver injected fuel in proportion to a pulse width of a signal received from a control system  26 ″″ via at least one electronic driver. The intake path  16 ″″ permits the flow of air and a flow of the first fuel  21 ″″ and a flow of the second fuel  31 ″″ from the throttle body  116 ″″ to the cylinder  10 ″″. A valve  28 ″″ is disposed in the intake path  16 ″″ of the cylinder  10 ″″ to selectively open and close the intake path  16 ″″. The exhaust path  18 ″″ permits a flow of a gaseous exhaust therethrough. A valve  29 ″″ is disposed in the exhaust path  18 ″″ of the cylinder  10 ″″ to selectively open and close the exhaust path  18 ″″. 
         [0049]    In the embodiment shown, the intake path  16 ″″ further includes a third injector  160  and a fourth injector  162 . The third injector  160  and the fourth injector  162  are so-called port fuel injectors (PFI) adapted to inject a second stream of the first fuel  21 ″″ and a second stream of the second fuel  31 ″″, respectively, into the intake path  16 ″″. As shown, the third injector  160  includes a fluid inlet  164  and a spaced apart fluid outlet nozzle  166 . The fluid inlet  164  is in fluid communication with a source of the first fuel  25 ″″. The fluid outlet  166  is in fluid communication with the intake path  16 ″″ of the cylinder  10 ″″. It is understood that the first fuel  21 ″″ can be any fuel such as an alternative fuel and a fossil fuel, for example. 
         [0050]    The fourth injector  162  includes a fluid inlet  170  and a spaced apart fluid outlet nozzle  172 . The fluid inlet  170  is in fluid communication with a source of the second fuel  37 ″″. The fluid outlet  172  is in fluid communication with the intake path  16 ″″ of the cylinder  10 ″″. It is understood that the second fuel  31 ″″ can be any fuel such as an alternative fuel and a fossil fuel, for example. The third injector  160  and the fourth injector  162  deliver injected fuel in proportion to a pulse width of a signal received from the control system  26 ″″ via at least one electronic driver. 
         [0051]    The cylinder  10 ″″ includes a fifth injector  180  and a sixth injector  182 . The fifth injector  180  and the sixth injector  182  are so-called direct injectors (DI) adapted to inject a third stream of the first fuel  21 ″″ and a third stream of the second fuel  31 ″″, respectively, into the combustion chamber  14 ″″. Although the fifth injector  180  and the sixth injector  182  illustrated are disposed overhead of the piston  12 ″″ near the intake path  16 ″″ and in a side wall of the cylinder  10 ″″, respectively, it is understood that the fifth injector  180  and the sixth injector  182  can be disposed elsewhere in the cylinder  10 ″″ as desired. As shown, the fifth injector  180  includes a fluid inlet  184  and a spaced apart fluid outlet nozzle  186 . The fluid inlet  184  is in fluid communication with the source of the first fuel  25 ″″. The fluid outlet  186  is in fluid communication with the combustion chamber  14 ″″. 
         [0052]    The sixth injector  182  includes a fluid inlet  190  and a spaced apart fluid outlet nozzle  192 . The fluid inlet  190  is in fluid communication with the source of the second fuel  37 ″″. The fluid outlet  192  is in fluid communication with the combustion chamber  14 ″″. The fifth injector  180  and the sixth injector  182  deliver injected fuel in proportion to a pulse width of a signal received from the control system  26 ″″ via at least one electronic driver. 
         [0053]    The control system  26 ″″ is adapted to monitor engine operating parameters via various sensors (not shown) to control an injection timing, an injection duration, and an injection rate of the injectors  140 ,  142 ,  160 ,  162 ,  180 ,  182 , and a fuel ratio of the first fuel  21 ″″ to the second fuel  31 ″″. Accordingly, the instantaneous demand of the ratio of each fuel and injection type and any combinations thereof up to all six injectors  140 ,  142 ,  160 ,  162 ,  180 ,  182  can be controlled in real time by the control system  26 ″″. An ignition coil  38 ″″ may be disposed in the combustion chamber  14 ″″ of the cylinder  10 ″″. The ignition coil  38 ″″ enhances an ignition timing control of the engine at certain conditions such as during cold start and low load operation, for example. 
         [0054]    Since operation of the fuel injection  8  for a cylinder  10  of an internal combustion engine illustrated in  FIG. 1  is substantially similar to the fuel injection system  8 ′,  8 ″,  8 ′″,  8 ″″ illustrated in  FIGS. 2  thru  5 , for simplicity, only the operation of the fuel injection system  8  will be described hereinafter. 
         [0055]    An operation is discussed herein below for a four-stroke internal combustion engine. It is understood that the above described invention can be used with other types of internal combustion engines as desired. The four-strokes involved in the combustion cycle of the engine are: the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. 
         [0056]    On the intake stroke, the piston  12  is caused to recede within the cylinder  10  and the valve  28  is caused to open. The fuel injection system  8  delivers a mixture of the first fuel  21 , the second fuel  31 , and air to the cylinder  10 . Accordingly, the air/fuel mixture is urged by atmospheric pressure into the cylinder  10 . After the piston  12  reaches a lower limit of travel or bottom dead center, the valve  28  is caused to close and the piston  12  is caused to return to an initial position. The valve  29  disposed in the exhaust path  18  also remains closed, so the cylinder  10  is sealed. As the piston returns, the air/fuel mixture is compressed. Thus, a pressure in the cylinder  10  is also increased. The compression process also causes the air/fuel mixture to increase in temperature. As the piston  12  reaches an upper limit of travel or top dead center on the compression stroke, an electric spark is produced by the ignition coil  38  to ignite the air/fuel mixture. The mixture burns rapidly and the pressure in the cylinder  10  increases. Accordingly, the pressure causes the piston  12  to recede within the cylinder  10 . A power impulse is then transmitted down through the piston  12  to the rest of the engine. Thereafter, as the piston  12  reaches the lower limit of travel, the valve  19  opens. As the piston  12  is caused to return to the initial position upon the exhaust stroke, the burned gases are forced out of the cylinder  10  into the exhaust path  18 . When the piston  12  reaches the upper limit of travel, the valve  19  closes, and the valve  28  opens. The cycle then repeats again with the intake stroke. The four strokes are continuously repeated during the operation of the engine. 
         [0057]    During the operation of the internal combustion engine, relative proportions of the first fuel  21  to the second fuel  31  and fuel injection type may be widely varied. The variations in the fuel ratio and injection type ratio may be based on an operating condition of the engine such as temperature, load, speed, throttle position, fuel quality, and the like, for example. 
         [0058]    In certain operating conditions of the engine, a proportionate amount of the first fuel  21  provided to the cylinder  10  may be miniscule such as about 0.0% of the total fuel to be combusted, while a proportionate amount of the second fuel  31  provided to the cylinder  10  may be significant such as about 100% of the total fuel to be combusted. On the other hand in other operating conditions of the engine, the proportionate amount of the first fuel  21  provided to the cylinder  10  may be significant such as about 100%, whereas the proportionate amount of the second fuel  31  provided to the cylinder  10  may be miniscule such as about 0.0%. The above describes two extreme scenarios to generally illustrate the range of the proportionate amounts of the first fuel  21  and the second fuel  31 , it is understood that the engine can be operated at a condition in which the proportionate amounts are between the extreme scenarios. 
         [0059]    Furthermore, in certain operating conditions of the engine, an amount of the first fuel  21  and the second fuel  31  provided to the cylinder  10  by direct injection may be miniscule such as about 0.0% of the total fuel to be combusted while an amount of the first fuel  21  and the second fuel  31  provided to the cylinder  10  by other means such as port fuel injection and throttle body injection may be significant such as about 100% of the total fuel to be combusted. On the other hand in other operating conditions of the engine, the amount of first fuel  21  and the second fuel  31  provided to the cylinder  10  by direct injection may be significant such as about 100%, whereas the amount of the first fuel  21  and the second fuel  31  provided to the cylinder  10  by other injection means may be miniscule such as about 0.0%. The above describes two extreme scenarios to generally illustrate the range of the amount of first fuel  21  and the second fuel  31  injected by each injector type, it is understood that the engine can be operated at a condition in which the amount of first fuel  21  and the second fuel  31  injected is between the extreme scenarios. 
         [0060]    It is understood that engine IMEP and engine combustion duration varies as a function of both the fuel ratio and the injection type ratio. The control of the engine combustion duration results in a more controllable combustion process in the cylinder  10 . Since combustion duration is closely related to in-cylinder air-to-fuel mixture temperature, it is also understood the in-cylinder air-to-fuel mixture temperature can also be regulated by varying both the fuel ratio and the injection type ratio. Further, the dual ratio control permits the adjustment of one of the IMEP and the in-cylinder air-to-fuel mixture temperature while the other can be maintained as desired. Additionally, the regulation of the IMEP and the in-cylinder air-to-fuel mixture temperature permits the start of combustion for an HCCI engine operated at either steady state or in transient operation to be controlled cycle-to-cycle. 
         [0061]    As illustrated in  FIG. 1 , the first injector  20  injects the first fuel  21  into the intake path  16 . The second injector  30  injects the second fuel  31  into the combustion chamber  14  of the cylinder  10 . In the embodiment shown, the first fuel  21  is alternative fuel and the second fuel  31  is one of alternative fuel and fossil fuel. Although the first injector  20  and the second injector  30  shown simultaneously inject the fuels  21 ,  31 , it is understood that the injectors  20 ,  30  can inject the fuels  21 ,  31  at separate times. It is also understood that any combination of the injectors  20 ,  30 , can be utilized throughout the operation of the engine. 
         [0062]    As illustrated in  FIG. 2 , the first injector  50  injects the first fuel  21 ′ and the second fuel  31 ′ into the intake path  16 ′. The second injector  60  injects the first fuel  21 ′ and the second fuel  31 ′ into the combustion chamber  14 ′ of the cylinder  10 ′. In the embodiment shown, the first fuel  21 ′ is alternative fuel and the second fuel  31 ′ is fossil fuel. Although the first injector  50  and the second injector  60  shown simultaneously inject the fuels  21 ′,  31 ′, it is understood that the injectors  50 ,  60  can inject the fuels  21 ′,  31 ′ at separate times. It is also understood that each of the injectors  50 ,  60  can separately inject each of the fuels  21 ′,  31 ′ and that any combination of the injectors  50 ,  60  can be utilized throughout the operation of the engine. 
         [0063]    As illustrated in  FIG. 3 , the first injector  80  injects the first fuel  21 ″ into the intake path  16 ″. The second injector  82  injects the second fuel  31 ″ into the intake path  16 ″. The third injector  100  injects the first fuel  21 ″ into the combustion chamber  14 ″ of the cylinder  10 ″. The fourth injector  102  injects the second fuel  31 ″ into the combustion chamber  14 ″ of the cylinder  10 ″. In the embodiment shown, the first fuel  21 ″ is alternative fuel and the second fuel  31 ″ is fossil fuel. Although the injectors  80 ,  82 ,  100 ,  102  shown simultaneously inject the fuels  21 ″,  31 ″, it is understood that the injectors  80 ,  82 ,  100 ,  102  can inject the fuels  21 ″,  31 ″ at separate times. It is also understood that any combination of the injectors  80 ,  82 ,  100 ,  102  can be utilized throughout the operation of the engine. 
         [0064]    As illustrated in  FIG. 4 , the first injector  120  injects the first fuel  21 ′″ into the throttle body  116 . The second injector  122  injects the second fuel  31 ′″ into the throttle body  116 . The third injector  100 ′″ injects the first fuel  21 ′″ into the combustion chamber  14 ′″ of the cylinder  10 ′″. The fourth injector  102 ′″ injects the second fuel  31 ′″ into the combustion chamber  14 ′″ of the cylinder  10 ′″. In the embodiment shown, the first fuel  21 ′″ is alternative fuel and the second fuel  31 ′″ is fossil fuel. Although the injectors  100 ′″,  102 ′″,  120 ,  122  shown simultaneously inject the fuels  21 ′″,  31 ′″, it is understood that the injectors  100 ′″,  102 ′″,  120 ,  122  can inject the fuels  21 ′″,  31 ′″ at separate times. It is also understood that any combination of the injectors  100 ′″,  102 ′″,  120 ,  122  can be utilized throughout the operation of the engine. 
         [0065]    As illustrated in  FIG. 5 , the first injector  140  injects the first fuel  21 ″″ into the throttle body  116 ″″. The second injector  142  injects the second fuel  31 ″″ into the throttle body  116 ″″. The third injector  160  injects the first fuel  21 ″″ into the intake path  16 ″″. The fourth injector  162  injects the second fuel  31 ″″ into the intake path  16 ″″. The fifth injector  180  injects the first fuel  21 ″″ into the combustion chamber  14 ″″ of the cylinder  10 ″″. The sixth injector  182  injects the second fuel  31 ″″ into the combustion chamber  14 ″″ of the cylinder  10 ″″. In the embodiment shown, the first fuel  21 ″″ is alternative fuel and the second fuel  31 ″″ is fossil fuel. Although the injectors  140 ,  142 ,  160 ,  162 ,  180 ,  182  shown simultaneously inject the fuels  21 ″″,  31 ″″, it is understood that the injectors  140 ,  142 ,  160 ,  162 ,  180 ,  182  can inject the fuels  21 ″″,  31 ″″ at separate times. It is also understood that any combination of the injectors  140 ,  142 ,  160 ,  162 ,  180 ,  182  can be utilized throughout the operation of the engine. 
         [0066]    From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.