Patent Publication Number: US-2011068188-A1

Title: Fuel injector for permitting efficient combustion

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims a priority to and claims the benefit of U.S. Provisional Application No. 61/275,812. U.S. Provisional Application No. 61/275,812 is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Fuel injectors are commonly used to supply fuel to the combustion chamber of an engine. The combustion occurs as soon as the injected fuel spray (fuel plume) has mixed with the air within combustible limits. The following are involved in aiding the bursting of the fuel droplets in the fuel plume in order to start the combustion process: air entrainment (which mixes air with fuel droplets), vaporization, homogenization, pressure, and heat. In a diesel engine, combustion already begins before homogenization begins. 
     The fuel droplet size typically has a Santer Mean Diameter (SDM) of, for example, approximately 10 micron-meters or less. SDM is measured as a 3 rd  power of volume and 2 nd  power of surface. The fuel plume has a high kinetic energy, with typical speed within the range of, for example, approximately 500 meters-per-second to approximately 700 meters-per second. The fuel plume will typically have an opening angle of approximately 3 degrees to approximately 4 degrees. 
     Two current examples of common types of fuel injector tips that are used are the MicroSac Tip and the VCR tip. Referring initially to  FIG. 1A , a partial cross-sectional view of a conventional injector  115  with the MicroSac tip  120  is shown. Fuel  122  is delivered toward the tip  120 , will exit through the opening A 3  in the tip  120 , and will travel along the fuel injection passage  124  prior to combustion. Typically, multiple fuel injection passages  124  are connected via openings (e.g., holes A 1  through A 4 ) to the tip  120 . In a standard engine, the multiple fuel passages  124  form an umbrella-like arrangement. 
       FIG. 1B  is a partial cross-sectional view of a conventional injector  150  with the VCR tip  155 . As known to those skilled in the art, the VCR tip has a conical design for the injector needle and reduces soot formation by reducing the drip of fuel droplets from the injector tip. Also, the small conical configuration of a VCR tip is advantageous in reducing the cavitation bubbles that form due to the high pressure flow of the fuel. Multiple fuel injection passages  160  are connected to the VCR tip  155 . 
     In a standard engine, the multiple fuel injection passages  160  form an umbrella-like arrangement. As will be discussed below, embodiments of the invention can be used with a fuel injector that has the MicroSac tip or the VCR tip. 
     It would be advantageous to improve the process of mixing of fuel and air, in order to achieve more efficient combustion. Therefore, improvements in the current technology would be desirable in order to overcome current constraints and deficiencies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1A  is a partial cross-sectional view of a conventional fuel injector with the MicroSac tip. 
         FIG. 1B  is a partial cross-sectional view of a conventional fuel injector with the VCR tip. 
         FIG. 2  is a cross-sectional view of a fuel injector, in accordance with an embodiment of the invention. 
         FIG. 3  is a partial cross-sectional view of an apparatus including a cylindrical air passage that is connected substantially perpendicular to a cylindrical fuel injection passage, in accordance with an embodiment of the invention. 
         FIG. 4  is a partial cross-sectional view of an apparatus including an air passage and a fuel injection passage that are non-perpendicular, in accordance with an embodiment of the invention. 
         FIG. 5  is a partial cross-sectional view of an apparatus including a fuel injection passage with a conical inlet and conical outlet and an air passage with a conical inlet, in accordance with another embodiment of the invention. 
         FIG. 6  is a partial cross-sectional view of an apparatus including a fuel injection passage with a bottleneck inlet and conical outlet, in accordance with another embodiment of the invention. 
         FIG. 7  is a partial cross-sectional view of an apparatus including a fuel injection passage with a conical inlet and bottleneck outlet, in accordance with another embodiment of the invention. 
         FIG. 8A  is a partial cross-sectional view of an apparatus including a fuel injection passage and air passages that provide a swirl (rotation) movement to fuel in the fuel injection passage, in accordance with another embodiment of the invention. 
         FIG. 8B  is a partial cross-sectional magnified view of the fuel injection passage and air passages of  FIG. 8A  wherein the air passages are connected tangentially to the fuel injection passage, in accordance with an embodiment of the invention. 
         FIG. 9  is a partial cross-sectional view of an apparatus including a fuel passage and non-parallel air passages that provide a swirl (rotation) movement to fuel in the fuel injection passage, in accordance with another embodiment of the invention. 
         FIG. 10A  is a partial cross-sectional view of an apparatus including a fuel injection passage and tangentially offset air passages that provide a swirl (rotation) movement to fuel in the fuel passage, in accordance with another embodiment of the invention. 
         FIG. 10B  is a partial front cross-sectional view of the fuel injection passage and air passages of  FIG. 10A , in accordance with an embodiment of the invention. 
         FIG. 11  is a partial cross-sectional view of an apparatus including a fuel injection passage with a conical jet and a conical diffusor and tangentially offset air passages, in accordance with another embodiment of the invention. 
         FIG. 12  is a partial cross-sectional view of an apparatus including a laval nozzle connected to a conical jet and conical diffusor, in accordance with another embodiment of the invention. 
         FIG. 13  is a partial cross-sectional view of an apparatus including a plurality of laval nozzles, in accordance with another embodiment of the invention. 
         FIG. 14A  is a diagram of an approximation of a fuel plume that can be generated by an embodiment of the invention, where the fuel injection passages are in the same plane; 
         FIG. 14B  is a partial front view of an apparatus including a plurality of fuel injection passages that are not in the same plane, in accordance with an embodiment of the invention. 
         FIG. 15  is a partial cross-sectional view of an apparatus including a plurality of twisted (non-parallel) fuel inlets, in accordance with another embodiment of the invention. 
         FIG. 16  is a partial top view of the plurality of twisted fuel inlets in  FIG. 15 , in accordance with an embodiment of the invention. 
         FIG. 17A  is a partial cross-sectional view of an apparatus with a combination of various features, in accordance with another embodiment of the invention. 
         FIG. 17B  is a partial top cross-sectional view of the apparatus of  FIG. 17A , in accordance with an embodiment of the invention. 
         FIG. 17C  is another partial top cross-sectional view of the apparatus of  FIG. 17A , in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of embodiments of the invention. 
       FIG. 2  is a cross-sectional view of a fuel injector (apparatus)  200 , in accordance with an embodiment of the invention. In this embodiment, the fuel injector  200  is shown with a MicroSac Tip. However, another embodiment of the invention can also be implemented with other injector tip types such as, for example, a VCR tip or other injector tip types that are currently available or that may be developed as the state of the art improves. The injector  200  includes an injector body  205  and injector needle  210 . The details of the injector tip section  215  will be discussed below. 
       FIG. 3  is a partial cross-sectional view of an apparatus  300  including a fuel injection passage  305  and an air passage  315  that is connected substantially perpendicular to the fuel injection passage  305 , in accordance with an embodiment of the invention. In an embodiment of the invention, the apparatus  300  is a fuel injector  300 . The fuel injection passage  305  is connected to an injector tip  301  (injector needle  301 ) of the fuel injector  300 . 
     In an embodiment of the invention as shown in  FIG. 3 , the fuel injection passage  305  has a constant diameter D 1  (i.e., a constant fuel injection passage diameter D 1  or constant fuel injection passage radius). Therefore, the fuel injection passage  305  is, for example, a cylindrical passage when the diameter D 1  is a constant value. 
     In an embodiment of the invention as shown in  FIG. 3 , the air passage  315  also has a constant diameter D 2  (i.e., a constant air passage diameter D 2  or constant air passage radius). Therefore, the air passage  315  is, for example, a cylindrical passage when the diameter D 2  is a constant value. 
     As a non-limiting example, the fuel injection passage  305  has a diameter D 1  of approximately 0.15 mm while the air passage  315  has a diameter D 2  of approximately 0.08 mm. However, D 1  and D 2  can be at other values. Also, as will be discussed below, each of the diameters D 1  and D 2  are not required to be constant. 
     In a preferred embodiment of the invention, the air passage diameter D 2  (i.e., second diameter D 2 ) of the air passage  325  is less than the fuel injection passage diameter D 1  (i.e., first diameter D 1 ) of the fuel passage  305 . 
     In an embodiment of the invention as shown in  FIG. 3 , the air passage  315  is connected substantially perpendicular (90 degrees or substantially 90 degrees) to the fuel injection passage  305 . Therefore, the angle B 1  between the passages  305  and  315  is approximately 90 degrees (or substantially 90 degrees) in value. In other embodiments to be discussed below, the angle B 1  is an acute angle. 
     In an embodiment of the invention as shown in  FIG. 3 , the fuel injection passage inlet (A 3 )  335  and fuel injection passage outlet  336  (of the injection passage  305 ) are each a round hole or a substantially round-shaped opening. The diameters of the inlet  335  and outlet  336  are also at the constant D 1  diameter value which is also the diameter of the fuel injector passage  305 . Variations in the shape of the inlet  335  and outlet  336  will be discussed below in other embodiments of the invention. 
     In an embodiment of the invention as shown in  FIG. 3 , the air passage inlet  338  of the air passage  315  is a round hole or a substantially round-shaped opening. The diameter of the inlet  338  is at the constant D 2  diameter value which is also the diameter of the air passage  315 . Variations in the shape of the inlet  338  will be discussed below in other embodiments of the invention. 
     The features of various embodiments of the invention can be used with a fuel injector that has a MicroSac tip, a VCR tip, or other injector tip types that are currently available or that may be developed as the state of the art improves. 
     The air passage outlet  339  of air passage  315  is connected at a location  340  which is between the fuel injection passage inlet  335  and fuel injection passage outlet  336  of the fuel injection passage  305 . The location  340  in the fuel injection passage  305  will contain an opening  341  for receiving the air flow  345  that is flowing along the air passage  315 . The opening  341  will also permit the air flow  345  to mix with fuel  350  that is flowing along the fuel injection passage  305 . The fuel  350  will first flow along the inner cylinder wall  355  and then will flow along the fuel injection passage  305 . The fuel  350  will then exit from the outlet  336  as a fuel plume  360 . The fuel plume  360  will contain fuel droplets and air  345  that is entrained with the fuel droplets. 
     The injection pressure for the fuel  350  is, for example, approximately 2,000 bar or other suitable values. This large amount of pressure can lead to the compressibility of the fuel liquid at up to, for example, approximately 5% to approximately 6%. Additionally, the injector tip  301  can have, for example, approximately 280 degrees to approximately 300 degrees of heat. 
     The fuel  350  can be, for example, diesel, gasoline, ethanol, ammonia, or other types of fuel such as other hydrocarbons, alcohols, or other diesel. It is also noted that embodiments of the invention can be used for direct injection or other types of fuel injections such as, for example, manifold injection. 
     The location  340  is between the fuel injection passage inlet  335  and fuel injection passage outlet  336 . In one preferred embodiment, the location  340  is at an approximate midpoint in the passage  305  between the ends  335  and  336 . 
     The fuel plume  360  exits the fuel passage  305  via outlet  336  into a combustion chamber which is shown symbolically as chamber  362  in  FIG. 3  for purpose of clarity in the drawings. 
     The air flow  345  (which flows along the air passage  315 ) is generated, for example, from the natural engine suction or pressurized flow from a turbocharger or supercharger, from air in the chamber  362  or from other suitable air generation sources. Standard air flow driving devices (not shown in  FIG. 3 ) may be used to control the air flow  345  through the air passage  315 . 
     The passages  305  and  315  can be metal pipes, or metal alloys, iron, or other suitable materials that form the cylinders of passages  305 / 315 . The passages  305 / 315  can be connected to each other by use of standard methods such as welding, molding, or other suitable known techniques for connecting metal materials, metal alloys, iron, or other suitable passages to each other. 
     Note that additional fuel passages  305  (for permitting fuel flow) can be connected to the injector tip  301 . For example, an additional fuel passage (not shown in  FIG. 3 ) can be connected, via injection hole Al, to the tip  301 . This additional fuel passage (which is connected via hole A 1 ) will also be connected to an additional air passage for permitting air flow. As one example, up to ten (10) fuel passages (with each fuel passage connected to an associated air passage) can be connected to the tip  301 , and these fuel passages can, for example, form an umbrella-shaped configuration around the tip  301 . 
     The fuel plume  360  will be an air-fuel mixture that is exiting from the fuel injection passage outlet  336  and will reach a certain depth penetration (i.e., length) into the combustion chamber  362 , and will also roll up adjacent to the injector tip  301  due to the back pressure in the surrounding air in the combustion chamber  362 . The core of the air-fuel mixture (in the plume  360 ) is liquid formed by the fuel droplets that travel together. The fuel droplets in the air-fuel mixture will burst up during the conversion of the kinetic energy of the flow of the air-fuel mixture and vaporize partly, which delays the combustion due to the removal of the vaporization heat. For combustion to occur, the correct amount of fuel and correct amount of air are needed to be present within the combustion limits. 
     By connecting the air passage  315  to the fuel injection passage  305  at location  340 , an enhanced mixing of fuel  350  and air  345  in the fuel injection passage  305  is achieved, prior to fuel combustion in the combustion chamber  362  and to take advantage of the Venturi principle during the mixing of fuel and air prior to combustion. The air flow  345  will enter via the air passage inlet  338 , will flow along the air passage  315 , and will then mix with the fuel  350  in the fuel injection passage  305 . The air-fuel mixture (which is formed due to mixing of air flow  345  with the fuel  350  and due to the air entrainment in the fuel  350 ) will exit from the fuel injection passage outlet  336  as a fuel plume  360  which is formed by an air-fuel mixture. 
     Since there is more air content in the air-fuel mixture of the plume  360  that exits the outlet  336  (due to the increased air entrainment provided by the air passage  315  to the fuel  350  in the fuel passage  305 ), the plume angle  365  of the fuel plume  360  will be wider, as compared to the plume angle that is achieved by previous approaches. The larger surface area of the plume  360  (due to the wider plume angle  365 ) results in the surrounding air in chamber  362  in breaking down the fuel droplets (in the plume  360 ) at a faster rate. The wider plume angle  365  can also result in a shorter length of the plume  360 . Since the plume  360  will have a wider plume angle  365 , the fuel droplets (in the plume  360 ) will be smaller in size and will disintegrate more quickly, resulting in an improved and efficient fuel combustion process. 
     In contrast, in current technology, there is a longer ignition delay due to the rich fuel mixture that is received by the combustion chamber and due to the vaporization heat that is extracted during vaporization. Soot and particulates are formed due to the rich fuel mixture and insufficient air, because the meeting of air and fuel does not happen in a desirable way or time. 
     On the other hand, an embodiment of the invention provides more air  345  to the fuel stream  350  at an earlier time as compared to conventional technology, and consequently, provides a wider plume angle  365 , as discussed above. As a result, the fuel droplets will disintegrate at a faster rate in the combustion chamber  362  and the soot formation problems of previous approaches are advantageously avoided or reduced. 
       FIG. 4  is a partial cross-sectional view of an apparatus  400  including an air passage  415  that is connected in an acute angle B 2  relative to the fuel injection passage  405 , in accordance with an embodiment of the invention. In this embodiment, the angle B 2  formed between passages  405  and  415  is substantially at an acute angle value (i.e., less than 90 degrees). Therefore, passages  405  and  415  are non-perpendicular to each other. Therefore, the direction of the air flow  345  is pointed substantially toward the direction (from inlet A 3  to outlet  406 ) of the flow of the fuel  350  in the passage  405 . As one non-limiting example, the angle B 2  is at value of approximately 75 degrees or other acute angle values. 
       FIG. 5  is a partial cross-sectional view of an apparatus  500  including a fuel injection passage  505  with a conical inlet  535  and conical outlet  536  and an air passage  515  with a conical inlet  538 , in accordance with another embodiment of the invention. Because of the conical shapes of the fuel injection passage  505  and air passage  515 , the diameters of the passages  505  and  515  are not constant. The conical shapes, bottleneck shapes, and/or bell-mouth (funnel) shapes for the inlets and outlets of the various fuel injection passages and air passages, as discussed herein, provide a decreased flow resistance in the passages. 
     The passages  505  and  515  are non-perpendicular to each other, and, therefore, the angle B 3  between the passages  505  and  515  is acute. For example, the angle B 3  is 80 degrees or another acute angle value. In another embodiment of the invention, the angle B 4  is 90 degrees, and, therefore, the passages  505  and  515  are perpendicular to each other. 
     The fuel injection passage  505  is connected via injection hole A 13  to the injection tip  301 , and the air passage  515  that is connected to the fuel injection passage  505  at location  540 . Since the inlet  535  and the outlet  536  are conical, a Venturi is formed at the location  540 . 
     The conical inlet  535  reduces the flow restriction on the fuel that is entering into the fuel injection passage  505 . A conical inlet  535  (or a substantially rounded inlet) reduces cavitation in the fuel injection passage  505 . Cavitation is caused by burbling on the passage inner wall near the intake opening that receives the fuel flow because the fuel flow would not immediately contact that passage inner wall. When the flow pressure at that passage inner wall falls below the vapor pressure, cavitation occurs and this can lead to the tearing of parts of the passage material. Therefore, a conical inlet  535  (or a substantially rounded inlet) advantageously reduces the occurrences of cavitation. 
     Since the inlet  535  and outlet  536  of the fuel injection passage  505  are conical, the passage  505  will not have a constant diameter D 1 . Instead, the fuel injection passage  505  will have a diameter D 1  that varies in value, depending on the particular location along the fuel injection passage  505 . For example, at location  540  where the air passage  515  connects to the fuel injection passage  505 , the diameter D M  of the fuel injection passage  505  is at a minimum value (e.g., approximately 0.08 mm). The diameter D inlet  (e.g., approximately 0.12 mm) at inlet  535  of fuel injection passage  505  and the diameter D outlet  (e.g., approximately 0.12 mm) at outlet  536  of fuel injection passage  505  are each greater than the diameter D M  at location  540 , in order to have the Venturi in the fuel injection passage  505 . In other words, D inlet &gt;D M  and D outlet &gt;D M . 
     Therefore, the fuel injection passage  505  will not be cylindrical in shape, but will instead be a conical shape from the inlet  535  and from the outlet  536 , with each of the inlet  535  and outlet  536  having a larger diameter than the diameter D M  at location  540 . Since D inlet &gt;D M  and D outlet &gt;D M , a Venturi is present in the fuel passage  505 . As a result, a depression occurs in the fuel flow  350  in the fuel injection passage  505  and air can be efficiently entrained in the fuel flow in fuel injection passage  505 . 
     As known to those skilled in the art, the Venturi effect is described by Bernoulli&#39;s Equation: 
         P   1 +(1/2)( d   1 )( v   1 ) 2   =P   2 +(1/2)( d   2 )( v   2 ) 2    (1)
 
     where, 
     P 1 =pressure at the inlet of the Venturi; 
     P 2 =pressure at the throat of the Venturi; 
     d 1 =air density at the inlet of the Venturi; 
     d 2 =air density at the throat of the Venturi; 
     v 1 =air velocity at the inlet of the Venturi; and 
     v 2 =air velocity at the throat of the Venturi. 
     Based on the law of conservation of impulse (Newton/second), mass can neither be created nor destroyed in a closed system, and as such, the volumetric flow rate at a first area A must equal the volumetric flow rate at a second area A″. When area A″ is smaller than area A, the flow traveling through A″ must travel faster in order to maintain the same volumetric flow rate. The increased velocity of the flow results in a decrease in pressure according to the Bernoulli equation. 
     Therefore, there is less pressure at location  540  where the air flow  345  meets that fuel  350 . Therefore, air entrainment in the flow of fuel  350  is efficiently achieved at location  540  because of the lesser pressure at this location. 
       FIG. 6  is a partial cross-sectional view of an apparatus  600  including a fuel injection passage  605  with a substantially bottleneck inlet  635  and substantially conical outlet  636 , in accordance with another embodiment of the invention. The bottleneck inlet  635  does not have the sharp edge at the passage opening that receives the fuel flow. Therefore, the bottleneck inlet  635  reduces the flow restriction on the fuel that is entering into the fuel injection passage  605 , and therefore, reduces cavitation on the passage  605 . 
     An air passage  615  is connected to the fuel passage  605  at location  640 . The air passage  615  can be perpendicular to the fuel passage  605  or can be at an acute angle B 1  (e.g., approximately 80 degrees) with respect to fuel passage  605 . 
     The fuel passage  605  will not have a constant diameter D 1 . Instead, the fuel passage  605  will have a diameter D 1  that varies in value, depending on the particular location along the fuel passage  605 . For example, at location  640  where the air passage  615  connects to the air passage  605 , the diameter D M  of the fuel passage  605  is at a minimum value (e.g., 0.08 mm). The diameter D inlet  at inlet  635  of fuel passage  605  and the diameter D outlet  at outlet  636  of fuel passage  605  are each greater than the diameter D M  at location  630 . In other words, D inlet &gt;D M  and D outlet &gt;D M . 
     In an embodiment of the invention, the inlet  635  will have a substantially bottleneck shape or other geometric shape. The outlet  636  can also have a substantially bottleneck shape (as shown in  FIG. 7 ) or a substantially conical shape as shown in  FIG. 6 . Note that embodiments of the invention are not limited to having the geometric shapes of a cone or a bottleneck at inlet  635  or outlet  636 . Other suitable geometric shapes may be used at inlet  635  or/and outlet  636  in order to reduce the flow restriction on fuel that flows along the passage  605 . Standard manufacturing or machining methods may be used to form the geometric shapes of the fuel passage  605 . 
     Note also that the conical air passage inlet  538  of  FIG. 5  may be incorporated in the apparatus  600  of FIG.  6  and in other embodiments of the invention as discussed herein. 
       FIG. 7  is a partial cross-sectional view of an apparatus  700  including a fuel injection passage  705  with a conical inlet  735  and bottleneck outlet  736 , in accordance with another embodiment of the invention. The bottleneck outlet  736  reduces the flow restriction on the fuel that is exiting from the fuel injection passage  705 . The fuel injection passage  705  is connected to the injector tip  301 , and an air passage  715  is connected to the fuel injection passage  705  at location  740 . 
     The inlet  735  can also have a bottleneck shape (as shown in  FIG. 6 ) or a conical shape as shown in  FIG. 7 . As in the embodiment of  FIG. 6 , other suitable geometric shapes may be used at inlet  735  or/and outlet  736  for reducing the flow restriction on fuel that flows along the passage  705 . 
     Note also that the conical air passage inlet  538  of  FIG. 5  may be incorporated in the apparatus  700  of  FIG. 7  and in other embodiments of the invention as discussed herein. 
       FIG. 8A  illustrates a partial cross-sectional view of a fuel injection passage  805  with a centerline  855  that does not intersect with the centerline  860 A (of air passage  815 A) and centerline  860 B (of air passage  815 B). Referring first to  FIG. 8A , a partial cross-sectional view of an apparatus  800  includes the fuel injection passage  805  and air passages  815 A and  815 B that provide air flows  345  that will cause a swirl (rotation) movement to fuel  350  in the fuel injection passage  805 , in accordance with an embodiment of the invention. The fuel injection passage  805  is connected to injection hole A 77  at the injector tip  301 . 
       FIG. 8B  is a partial cross-sectional magnified view of the fuel injection passage  805  and air passages  815 A and  815 B of  FIG. 8A , in accordance with an embodiment of the invention. The air passage  815 A is substantially tangential to the fuel passage  805  at the tangential junction  875 A, while the air passage  815 B is substantially tangential to the fuel passage  805  at the tangential junction  875 B. Therefore, a tangential junction in the fuel injection passage  805  is the outer wall or outer surface (of the fuel injection passage  805 ) that is in contact with an air passage. 
     The centerlines  860 A and  860 B (of air passages  815 A and  815 B, respectively) are substantially parallel or can have a slight angle difference. For example, the centerline  860 A and  860 B can have zero degrees of angle difference (i.e., are parallel) or can have an acute angle difference (e.g., approximately 10 degrees or less). 
     Since two air passages  815 A and  815 B are provided, more air  345  are provided for air entrainment in the fuel  350 . The air passages  815 A and  815 B also provide the swirl  870  that provides a twisting movements to the fuel  225 . The swirl  870  is an air flow direction that will aid in bursting the fuel droplets in the fuel plume that exits the fuel passage  805  because the swirl  870  (in a counter-clockwise direction in the example of  FIG. 8B ) introduces centrifugal force to the droplets in the fuel  350 . This centrifugal force will cause the fuel plume angle  365  ( FIG. 3 ) to become wider. As a result, the fuel droplets in the fuel plume  360  (as received by the combustion chamber) will burst more efficiently during combustion. 
       FIG. 9  is a partial cross-sectional view of an apparatus  900  that includes a fuel injection passage  905  and non-parallel air passages  915 A and  915 B that provide a swirl (rotation) movement  970  to fuel  350  in the fuel injection passage  905 , in accordance with an embodiment of the invention. The air passage  915 A is substantially tangential to the fuel injection passage  905  at the tangential junction  975 A, while the air passage  915 B is substantially tangential to the fuel injection passage  905  at the tangential junction  975 B. The air passages  915 A and  915 B are separated by angle C 1 , where C 1  is 90 degrees or greater and less than 180 degrees. Therefore, the air passages  915 A and  915 B are in an offset configuration and are not parallel. 
       FIG. 10  includes  FIGS. 10A and 10B .  FIG. 10A  is a partial cross-sectional view of an apparatus  1000  including a fuel passage  1005  and tangentially offset air passages  1015 A and  1015 B that provide a swirl (rotation) movement to fuel  350  in the fuel passage  1005 , in accordance with another embodiment of the invention.  FIG. 10B  is a partial front cross-sectional view of the fuel passage  1005  and air passages  1015 A and  1015 B of  FIG. 10A , in accordance with an embodiment of the invention. The fuel passage  1005  is at a radial downward direction  1020 . In another embodiment, the fuel passage outlet  1036  has a geometric shape as an option, such as, for example, conical shape, bell-mouth shape (funnel shape), bottleneck shape, or other suitable geometric shapes that will reduce flow resistance to fuel  350  that flows along the fuel injection passage  1005 . 
     The air passages  1015 A/ 1015 B are tangentially offset in configuration. For example, as best shown in  FIG. 10B , the air passage  1015 A is angled at angle value D 1  with respect to horizontal reference line  1070 . The angle D 1  can be from zero degrees to 90 degrees in value and is typically, for example, an acute angle value. The air passage  1015 B is angled at angle value D 2  with respect to horizontal reference line  1070 . The angle D 2  can be from zero degrees to 90 degrees in value and is typically, for example, an acute angle value. 
     As another option in an embodiment of the invention, the tangential offset to the air passages  1015 A and  1015 B is based on distance between the respective tangential junctions of the air passages  1015 A and  1015 B. For example, in  FIG. 10A , the air passage  1015 A is tangentially connected to the fuel injection passage  1005  at the tangential junction  1075 A, and the air passage  1015 B is tangentially connected to the fuel injection passage  1005  at tangential junction  1075 B. The location  1075 A and  1075 B are separated by an offset distance Y along the fuel injection passage  1005  (where Y=location  1075 A−location  1075 B). As a result, the air passage  1015 A is offset by the tangential offset distance Y from the air passage  1015 B, along the length of the fuel injection passage  1005 . This tangential offset distance Y permits the air passages  1015 A and  1015 B to provide air flow  345  with turbulence that introduces centrifugal force to the fuel droplets in the fuel passage  1005 . 
       FIG. 11  is a partial cross-sectional view of an apparatus  1100  including a fuel injection passage  1105  with a conical jet  1105 A and a conical diffuser  1105 B and tangentially offset air passages  1115 A and  1115 B, in accordance with another embodiment of the invention. The fuel injection passage  1105  has a central axis that has the same direction as the injector axis  1117  of the injector needle  210  ( FIG. 2 ), or is near in the same direction as the axis  1117  of the injector needle  210  with little deviation from the axis  1117 . Therefore, the fuel injection passage  1105  is not arranged in the umbrella configuration that has been described above. The spray of the fuel  350  will be in the orientation of the injector axis  1117  or will substantially be in the orientation of the injector axis  1117 . 
     The tangentially offset air passages  1115 A/ 1115 B provide a swirl (rotation) movement to fuel in the fuel passage  1105 . The air passages  1115 A/ 1115 B are tangentially offset in configuration. For example, this tangential offset is achieved by connecting the air passage  1115 A to the front surface of the fuel passage  1105  and connecting the air passage  1115 B to the rear surface of the fuel passage  1105 . 
     To permit improved air flow  345  into the air passages  1115 A and  1115 B, each of the inlet  1138 A and inlet  1138 B has a geometric shape, such as, for example, conical shape, bell-mouth shape (funnel shape), bottleneck shape, or another suitable geometric shape that reduces the flow restriction on the air  345 . In the example of  FIG. 11 , the air passage inlets  1138 A and  1138 B are each rounded air passage inlets. 
     Additionally, the outlet  1152 A (of air passage  1115 A) and the outlet  1152 B (of air passage  1115 B) can be rounded (or expanded) in shape, as best illustrated in  FIG. 11 , so that the flow restriction on the air  345  is reduced. However, in other embodiments of the apparatus  1100 , the rounded (or expanded) shape of the outlets  1152 A/ 1152 B is omitted. As a result, in this alternative configuration, the outlets  1152 A and  1152 B will have the non-rounded shapes  1153 A and  1153 B, respectively. The air passages  1115 A and  1115 B each has a minimum diameter D 5  of, for example, approximately 0.16 mm. 
     The conical jet  1105 A reduces cavitation. The conical jet  1105 A can be a conical passage with a rounded inlet that receives the fuel flow  350  or can be conical inlet. The conical jet  1105 A can be at a minimum conical jet diameter D 3  of, for example, approximately 0.08 mm, at conical jet outlet  1160  and at a maximum conical jet diameter D 4  of, for example, approximately 0.15 mm at the conical jet inlet  1135 . The conical jet diameter decreases from the conical jet inlet  1135  to the conical jet outlet  1160 . The cone formed by the conical jet  1105 A can be at a cone angle of, for example, approximately 8 degrees. 
     The conical diffusor  1105 B has a larger increasing diameter toward the conical diffuser outlet  1136  and allows for more air  345  to be entrained with the fuel  350 . The conical diffusor  1105 B can be at a maximum conical diffusor diameter D 6  of, for example, approximately 0.24 mm, at conical diffusor outlet  1136 . The conical diffusor  1105 B can be at a minimum conical diffusor diameter D 7  at conical diffusor inlet  1136 , where D 7 &lt;D 6  and where the conical diffuser diameter increases from the conical diffuser inlet  1137  to the conical diffuser outlet  1136 . The cone formed by the conical diffusor  1105 B can be at a cone angle of, for example, approximately 25 degrees. 
     The conical shape of the conical diffuser  1105 B permits the laser machining to swivel via outlet  1136  in order to shape the conical diffusor  1105 B and conical jet  1105 A into the desired configurations. Other types of standard machining (such as, e.g., electrical discharge machining or EDM) may be used to shape the conical jet  1105 A and conical diffusor  1105 B. 
     Since the fuel  350  is traveling from the wider diameter D 4  at conical jet inlet  1135  to the narrower diameter D 3  at conical jet outlet  1160 , a high speed movement is applied to the flow of fuel  350  and the swirl, movement of the air  345  from air passages  1115 A and  1115 B will also entrain air into the fuel flow, leading to a wider plume angle  365  of the plume  360 . 
       FIG. 12  is a partial cross-sectional view of an apparatus  1200  including a fuel injection passage  1205  and a laval nozzle  1215  which function as an air passage for air  345 , in accordance with another embodiment of the invention. As similarly discussed above, the fuel injection passage  1205  is formed by a conical jet  1205 A with a cone angle B 4  of, for example, approximately 8 degrees, and a conical diffuser  1205 B with a cone angle B 3  of, for example, approximately 25 degrees. Other details of a conical jet and conical diffuser have also been described above. 
     The laval nozzle  1215  creates a high speed flow (or increased speed flow) for the air  345  that will be entrained with the fuel  350  that flows along the fuel injection passage  1205 . The laval nozzle  1215  includes an inlet opening  1220  of a wide geometric shape opening such as a round opening, rectangular opening, elliptical opening, or other geometric opening. The laval nozzle inlet  1225  can also have conical shape, bell-mouth shape (funnel shape), bottleneck shape, or another suitable geometric shape that reduces the flow restriction on the air  345 . In the example of  FIG. 12 , the inlet  1225  is a bell-mouth shape. The laval nozzle  1215  can be shaped by use of standard machining techniques such as, for example, laser machining or EDM. 
     A narrow passage  1230  is adjacent to the inlet  1225 . The narrow passage  1230  is the minimum laval nozzle diameter D 8  value for the laval nozzle  1215 . As an example, the diameter D 8  is approximately 0.08 mm. 
     A laval nozzle diffusor  1235  is adjacent to the narrow passage  1230 . The diffusor  1235  can have a conical shape or other increasing geometric shape that permits diffusion of the air flow  345  from the narrow passage  1230 . The diffused air flow  345  flows from the diffusor  1230  to a volume  1242 . The volume  1240  could have a suitable geometric shape such as, for example, a cylinder shape. The volume  1242  will have a widest section S 1 . As an example, the widest section S 1  is approximately 0.6 mm. 
     Within the volume  1242 , the air flow  345  mixes with and is entrained into the fuel  350  that flows from the conical jet  1205 A. The air/fuel mixture then flows through the conical diffuser  1205 B and exits through the conical diffusor outlet  1236 . The outlet  1236  will have a diameter of, for example, approximately 0.52 mm. 
     The conical jet  1205 A will have the smallest diameter value at location  1240  where the conical jet  1205 A connects to the volume  1242 . The use of the laval nozzle  1215 , volume  1242 , conical jet  1205 A, and conical diffusor  1205 B allow the improved entrainment of air  345  into the fuel  350 , resulting in a broad plume angle  365  for the plume  360  that exits the outlet  1236  or non-homogenous patterns of decreased fuel droplet sizes in the fuel plume  360 . 
       FIG. 13  is a partial cross-sectional view of an apparatus  1300  including a plurality of laval nozzles, in accordance with another embodiment of the invention. Each laval nozzle is connected to a conical jet and conical diffusor. For purposes of clarity, only 3 laval nozzles ( 1315 ( 1 ),  1315 ( 2 ), and  1315 ( 3 )) are shown as examples in  FIG. 13 . 
     The laval nozzle  1315 ( 1 ) is connected to the conical jet  1305 A( 1 ) and conical diffusor  1305 B( 1 ). The laval nozzle  1315 ( 2 ) is connected to the conical jet  1305 A( 2 ) and conical diffusor  1305 B( 2 ). The laval nozzle  1315 ( 3 ) is connected to the conical jet  1305 A( 3 ) and conical diffusor  1305 B( 3 ). The details of a laval nozzle has been previously described above. 
       FIG. 14A  is a diagram of an approximation of a fuel plume  1400  that can be generated by an embodiment of the invention. Air  345  is entrained with the example fuel droplets  1406 A- 1406 C. As an example, the fuel plume is received by a combustion chamber bore  1402  having the sized of, e.g., approximately 65 mm bore diameter. The fuel plume length L 1  depends on the compression pressure in the combustion chamber. Typically, in a diesel engine, the peak compression pressure in a diesel engine is, for example, approximately 80 bar to approximately 100 bar. The compression pressure will cause the fuel droplets to roll up, as shown by example boundaries  1410 A and  1410 B in the fuel droplets  1406 A and  1406 C. 
     The plume angle  365  would be wider due to air entrainment with the fuel droplets and the compression pressure against the fuel droplets. For example, the plume angel  365  is approximately 25 degrees. More entrainment of air  345  in the fuel results in a wider plume angel  365  for a plume  1406 C (and for the other plumes  1406 A- 1406 B). 
     The injector offset angle  1416  is the angle of a fuel injection passage with respect to an orientation of an injector axis  1420 . In  FIG. 14A , the fuel injection passages  1405 A- 1405 C are shown as examples. In this embodiment of the invention, the fuel injection passages  1405 A- 1405 C are in the same plane  1408 . 
     The fuel injection passage  1405 A is offset by an injector offset angle  1416  of, e.g., 30 degrees from the injector axis  1420 . As a result, the plume  1406 A travels in a direction that is substantially along the offset axis  1418 . 
     Similarly, the fuel injection passage  1405 C is offset by an injector offset angle from the injector axis  1420 . A 
     The fuel injection passage  1405 B has an orientation that is substantially along the injector axis  1420 . As a result, the plume  1406 B travels in a direction that is substantially along the injector axis  1420 . 
     Embodiments of the invention advantageously provide a broader fuel plume angle which will reduce large air pocket areas in the combustion chamber by filling these large air pocket areas with fuel droplets. In other words, an embodiment of the invention allows the improved entrainment of air into the fuel, resulting in a broad plume angle for the air-fuel mixture that is transmitted to the combustion chamber or/and non-homogenous patterns of decreased fuel droplet sizes for the air-fuel mixture. 
       FIG. 14B  is a partial front view of an apparatus  1450  including a plurality of fuel injection passages that are not in the same plane, in accordance with an embodiment of the invention. As discussed above, in an embodiment of the invention, a plurality of fuel injection passages (e.g., passages  1405 A- 1405 C that output the fuel flows  350 A- 350 C, respectively) are in the same first plane  1408 . In another embodiment of the invention, at least one fuel injection passage is in a second plane  1455 . In the example of  FIG. 14B , the fuel injection passages  1405 D- 1405 E (that output the fuel flows  350 D- 350 E, respectively) are in the second plane  1455 . Therefore, the first group of passages  1405 A- 1405 C is in a dispersed orientation (staggered orientation) from the second group of passages  1405 D- 1405 E. The first plane  1408  is oriented along the injector axis  1420  ( FIG. 14A ) and the second plane  1455  is offset by an offset angle  1460  from the first plane  1408  (and injector axis  1420 ). 
       FIG. 15  is a partial cross-sectional view of an apparatus including a plurality of twisted (non-parallel) fuel inlets  1505 A in the fuel injection passage  1505 . The fuel injection passage  1505  also includes a conical diffusor  1505 B with an outlet  1536  for releasing the fuel plume  360 . A laval nozzle  1515  also forms the air passage for transmitting air  345  that will be entrained with the fuel  350 . In other embodiments of the invention, the air passage  1515  is not a laval nozzle and is instead other embodiments of the air passage configurations as disclosed above. 
     The twisted fuel inlets  1505 A is formed by, for example, the fuel paths  1505 ( 1 )- 1505 ( 3 ) which are separate holes that are drilled through the material that forms the fuel injection passage  1505 . The fuel paths  1505 ( 1 )- 1505 ( 3 ) may be drilled by, for example, laser drilling or other suitable machining methods. The number of fuel paths may vary in number. 
     The fuel paths  1505 ( 1 ),  1505 ( 2 ), and  1505 ( 3 ) will have axis lines (center lines)  1510 ( 1 ),  1510 ( 2 ), and  1510 ( 3 ), respectively, as best shown in  FIG. 15 . The axis lines  1510 ( 1 ) to  1510 ( 3 ) are non-parallel (i.e., are skewed, offset, or twisted) as shown in  FIG. 15 . Therefore, the fuel flows  350 ( 1 ),  350 ( 2 ), and  350 ( 3 ) through the fuel paths  1505 ( 1 ),  1505 ( 2 ), and  1505 ( 3 ), respectively, will also be non-parallel as shown in  FIG. 15  and will substantially flow in the direction of the axis lines  1510 ( 1 ),  1510 ( 2 ), and  1510 ( 3 ), respectively. 
     The non-parallel fuel flows  225 ( 1 )- 225 ( 3 ) will introduce a swirl-like or twist-like (or other disturbance) to the fuel flow in the fuel passage  1505 . Therefore, the kinetic energy of the fuel flow through fuel passage  1505  will be higher than the air flow  345  through the air passage  1515 . If the fuel  350  through fuel passage  1505  has approximately 2000 bar of potential energy and approximately 700 meters/second of kinetic energy, then the impulse created by the meeting of the fuel flows  350 ( 1 )- 350 ( 3 ) and air  345  along the volume  1542  improves air entrainment in the fuel flow. As similarly discussed above, the air entrainment in the fuel flow permits a wider angle  365  in the fuel plume  360  that exits the outlet  1536  and aid in the bursting of fuel in the combustion chamber. 
       FIG. 16  is a top view of the plurality of twisted fuel paths  1505 ( 1 )- 1505 ( 3 ) in  FIG. 15 , in accordance with an embodiment of the invention. The fuel paths  1505 ( 1 )- 1505 ( 3 ) on the cylindrical material (e.g., pipe) that forms the fuel passage  1505  may vary in locations, configurations, and/or shape, and may vary in number. Therefore, the configuration of the fuel paths  1505 ( 1 )- 1505 ( 3 ) shown in  FIG. 16  is not necessarily a limiting example. 
       FIG. 17A  is a cross-sectional view of an apparatus  1700  with a combination of various features in accordance with an embodiment of the invention. The fuel injection passage  1705  includes the twisted fuel inlets (skewed twin nozzles)  1705 A and the conical diffusor  1705 B. The twisted fuel inlets  1705 A is formed by a plurality of non-parallel fuel paths such as, for example, the non-parallel fuel paths  1705 ( 1 )- 1705 ( 2 ). In an embodiment of the invention, the skewed twin nozzles are conical (k-Factor) and rounded at the entrance. The cone angle in the initial nozzle hole is called k-factor when ordering a nozzle. The cone angle can be, for example: (1) cylindrical, (2) conical opening outwardly, or (3) conical converging towards the mixing chamber which is in contact with the air passages  1715 A and  1715 B. A skewed nozzle entry from the sac can optionally have a rounding radii (called “HE” when ordering nozzles). The nozzle  1705 ( 1 ) has the entrance  1706 ( 1 ) and the nozzle  1705 ( 2 ) has the entrance  1706 ( 2 ). As an example, a skewed nozzle will have a diameter of 0.09 mm at its narrowest point. 
     The fuel paths  1705 ( 1 )- 1705 ( 2 ) will have the axis lines (center lines)  1710 ( 1 )- 1710 ( 2 ), respectively, that are non-parallel (i.e., are skewed, offset, or twisted). Therefore, the non-parallel fuel flows  350 ( 1 )- 350 ( 2 ), along the non-parallel fuel paths  1705 ( 1 )- 1705 ( 2 ), respectively, introduces a swirl or twist to the fuel flow  350  in order to improve the air entrainment in the fuel flow. 
     The twin tangential air passages  1715 A and  1715 B are connected to the fuel injection passage  1705  at a tangential junction, as similarly discussed above. The air passages  1715 A and  1715 B have inlets  1738 A and  1738 B, respectively. Each of the inlets  1738 A and  1738 B has a shape that decreases the flow resistance for the air  345 . For example, each of the inlets  1738 A and  1738 B has a bell-mouth shape as shown in the example of  FIG. 17A . In another embodiment, each of the inlets  1738 A and  1738 B has another shape for reducing air low resistance such as, for example, a conical shape, bottleneck shape, or another suitable shape for reducing flow resistance. The various features that are shown in  FIG. 17A  for the apparatus  1700  can be manufactured by use of, for example, laser machining, EDM, or other suitable manufacturing methods. 
       FIG. 17B  is a partial top cross-sectional view of the apparatus  1700  of  FIG. 17A , in accordance with an embodiment of the invention. The air passage  1715 A is substantially tangential to the fuel injection passage  1705  at the tangential junction  1775 A at the front surface of fuel injection passage  1705 . The air passage  1715 B is substantially tangential to the fuel injection passage  1705  at the tangential junction  1775 B at the rear surface of the fuel injection passage  1705 . 
     The air passages  1715 A/ 1715 B also provide the air swirl  1780  that provides a twisting movements to the fuel flows  350 ( 1 )- 350 ( 2 ). Therefore, the fuel  350  and air  345  will each have a swirl  1780  that improves air entrainment in the fuel  350  and the air entrainment will aid in bursting the fuel plume that exits the conical diffusor  1705 B ( FIG. 17A ). 
       FIG. 17C  is another partial top cross-sectional view of the apparatus  1700  of  FIG. 17A , in accordance with an embodiment of the invention. A top cross-sectional view of the skewed twin nozzles  1705 ( 1 ) and  1705 ( 2 ) are shown with respect to the tangential offset air passages  1715 A and  1715 B. 
     The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. 
     These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.