Abstract:
A countercurrent spray nozzle injects fuel into the intake manifold of an internal combustion engine to give better mixing of fuel and air. Better mixing results in less NOx and less incomplete combustion of carbon.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to mixing fuel and combustion air in preparation for burning the mixture in an internal combustion engine. 
     Most modern four cycle engines in automobiles use an individual injector to meter fuel into combustion air for each cylinder. Each injector is placed to one side of its air duct and tilted to aim its spray at the intake valve for its cylinder. A fine spray of fuel from the injector starts at a point on the wall of a combustion air duct, mixes with combustion air and then moves through an intake valve and into the cylinder during the intake stroke for the cylinder. Refer to  FIG. 1 . During this period and while passing through the intake valve, the fuel must vaporize and mix with the air so that a combustible mixture is ready for ignition. Although the fuel is highly volatile, achieving a perfect stoichiometric mixture throughout the cylinder is difficult because of the short time allowed. A six-cylinder engine at 3000 rpm has approximately 0.03 seconds to accomplish mixing, vaporization, move the air-fuel mixture into the cylinder and compress the mixture before ignition. Some engines inject fuel only during the intake cycle (sequential injection). Other engines inject fuel each revolution, on the intake stroke and also when the intake valve is closed (simultaneous port injection). 
     Perfect mixing of fuel and combustion air is approached, but never achieved, on the macroscopic level. There are small “pockets” of gas in the cylinder where fuel concentration is above (rich) or below (lean) the ideal concentration for stoichiometric combustion. Rich pockets with a shortage of oxygen burn cool and result in incompletely burned carbon and uneconomical loss of energy. Lean pockets with an excess of oxygen burn at high temperature. At high temperatures inert N2 molecules dissociate into highly reactive N atoms which then combine with oxygen to form a range of several oxygen-nitrogen compounds commonly referred to as NOx. NOx is an undesirable air pollutant, and thought to take part in smog formation. While burned exhaust gas is often re-injected into the engine to complete combustion; this method can result in lower efficiency for the engine. Also, a catalytic converter is used to further combustion. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to more uniformly mix fuel and air before the combustible mixture is ignited in the cylinder. With better mixing, a given air-fuel mixture will burn at a more uniform temperature with less NOx in smaller fuel-lean hot pockets and more complete combustion in smaller fuel-rich cool pockets. 
     Benefits from better mixing can be realized in any of several ways. A leaner mixture can be used to reduce fuel consumption and improve fuel economy at a constant level of NOx and wasted carbon levels, or the level of NOx and carbon pollutants can be reduced at constant fuel consumption. A less volatile fuel may be used with constant NOx and wasted carbon levels. Also, the load on the engine&#39;s catalytic converter is reduced. 
     The forgoing objective of better mixing can be achieved by introducing the atomized spray of fuel into the combustion air duct in a direction countercurrent to the direction of airflow during the cylinder&#39;s intake stroke. In its preferred embodiment, fuel  12  in  FIG. 2  is injected at a point of the combustion air  3 &#39;s highest velocity  32  which is usually near the duct&#39;s center, but may vary with configuration of the upstream duct. Refer to  FIG. 2  as a typical but not limiting reversed jet (countercurrent) installation. 
     In traditional fuel injection,  FIG. 1 , fuel-air mixing results from turbulence as fuel  10  is injected in to manifold  4  and also from turbulence as fuel-air mixture  8  passes by an intake valve  5  and its seat  9 . This invention uses these same traditional mixing mechanisms plus four additional distinct and different mechanisms to achieve improved mixing. 
     1. With this invention, atomized fuel spray  12  and the direction of air flow  32  are countercurrent,  FIG. 2 , and their individual velocities add to give a higher relative velocity between fuel spray  12  and peak velocity combustion air  32 . This high relative velocity shatters droplets to smaller sizes (“PERRY&#39;S CHEMICAL ENGINEER&#39;S HANDBOOK” 6th ed., p. 18-53) giving them more surface area for heat transfer from combustion air and thus faster evaporation to a vapor. This high relative velocity compares to the traditional concurrent method  FIG. 1  for fuel injection in which spray  10  enters stationary air or is concurrent with airflow  3  during the engine&#39;s intake stroke. During concurrent injection, relative velocity between droplets and air is the difference of the two velocities. Lower relative velocity allows larger drops and less surface for heat and mass transfer between the two phases.
 
2. Besides an increase of surface area, greater relative velocity between droplets and combustion air also increases the heat transfer coefficient between droplets and combustion air (Mc Adams “HEAT TRANSMISSION” 2nd ed., p. 251) compared to a lower relative velocity and lower heat transfer coefficient found with traditional concurrent fuel injection.
 
3. Placing a countercurrent jet  30  in  FIG. 2  at a point of peak air velocity  32  puts the fuel closer to its final destination of being mixed with combustion air. By comparison, the traditional injection point on one side of duct  4  in  FIG. 1  makes it necessary for some fuel to migrate across the diameter of duct  4 .
 
4. An additional mechanism, which improves mixing when fuel is introduced by this invention, comes from the trajectory of droplets relative to counter flowing air. Even though countercurrent droplets  12  in  FIG. 2  leave nozzle  30  at high velocity, their small size prevents significant movement directly into peak velocity air stream  32 . Instead, droplets  12  are forced radially at high velocity in all directions toward the wall of duct  4 . This forced movement disperses the droplets throughout combustion air for better early mixing.
 
     All of these four mixing mechanisms take place before fuel  12  and air  3  in  FIG. 2  pass by intake valve  5  and its seat  9  which makes them in addition to traditional mixing. 
     Countercurrent fuel injection is most effective when intake air is flowing; and therefore, engines with sequential injection will benefit most from its use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a conventional installation of a fuel injector  6  at one side (top) of its combustion air duct (intake manifold)  4  and its position relative to the engine&#39;s intake valve  5 . 
         FIG. 2  shows a typical but not limiting countercurrent fuel injector assembly  21 A installed according to this invention. 
         FIG. 3  shows an exploded view of a typical fuel injector extension  33 .  FIG. 3  also shows the outlet end of injector valve  21 . When extension  33  in  FIG. 3  is assembled and joined to injector valve  21 , injector assembly  21 A in  FIG. 2  is formed. Injector assembly  21 A in  FIG. 2  implements this invention when installed in an engine with a matching intake manifold geometry. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Conventional fuel injector  6  in  FIG. 1  performs two functions. It acts as an on-off valve to meter fuel  2  as called for by a pulsating electrical signal  1  from the engine&#39;s controller. It also atomizes and sprays fuel  10  into combustion air  3 . 
     In this invention, injector valve  21  in  FIG. 2  performs only one function. It acts as an on-off valve to meter fuel  2  as called for by a pulsating electrical signal  1  from the engine&#39;s controller. An extension  33  in  FIG. 3  is attached to injector valve  21  to place nozzle  30  so that spray  12  in  FIG. 2  is countercurrent into peak velocity combustion air  32 . 
     Because injector valve  21  is in series with nozzle  30  in  FIG. 2 , its pressure drop at designed fuel flow rate should be the least that allows injector valve  21  to have its necessary operating speed. Injector valve  21  may be especially made, or from a larger engine such as a stock car application. In some cases injector valve  21 &#39;s pintel  23  in  FIG. 3  can be ground away to increase capacity. Because of pressure drop through injector valve  21  and extension  33 , fuel supply pressure  2  in  FIG. 2  should be increased as needed to maintain design pressure to nozzle  30 . An outlet glue surface  22  of injector valve  21  in  FIG. 3  should be prepared as needed for glue joining to glue surface  18  of extension  33 . 
       FIG. 3  shows an exploded view of extension  33 . All metal and plastic parts should resist corrosion in the atmosphere and temperatures encountered in the cylinder&#39;s intake manifold. All fuel flow inlet surfaces such as tube  29 , slots  16  and nozzle orifice  31  should be smooth and rounded. “O” rings are preferred for gaskets wherever temperature limitations for the rings are not exceeded. 
     Extension  33  in  FIG. 3  has an adaptor  26  which is welded to a connector  25  of a material suitable for a glue joint between injector valve  21 &#39;s glue surface  22  and connector  25 &#39;s glue surface  18 . Connector  25  also carries indexing tabs  20 . These tabs are spaced so that only the correct injector will fit into matching slots on its particular port. Adaptor  26  uses an “O” ring  7  as its seal in an injector port. A second “O” ring  28  seals adaptor  26  to surface  24  of injector valve  21  when they are joined. An extension tube  29  is welded to adaptor  26  and to a reversing block  11 . 
     Block  11  in  FIG. 3  is made at an angle G to direct fuel spray  12  directly counter-current into peak velocity of combustion air flow  32  in  FIG. 2 . Extension  29  may be bent and or extended as needed to inject fuel spray at a lateral point of maximum combustion air velocity. Fuel drainage from nozzle  30  may be a problem for some, especially large, engines. If such is the case, extension  29  may also be shaped as needed to create a spot at or near block  11  that is lower (a trap) than outlet  31  of nozzle  30 . 
     Reversing block  11  in  FIG. 3  is limited in size to a dimension  19  which must pass through its cylinder&#39;s injector port. Block  11 &#39;s inlet is drilled to receive the outlet of extension  29 . The outlet of block  11  is drilled to receive a spinner  15 , an “O” ring  14  and nozzle  30 . Evenly spaced angular grooves  16  in spinner  15  spin the fuel which causes it to spread into a cone as it leaves orifice  31 . 
     Spray nozzle  30  in  FIG. 3  includes a spinner  15  as a means to produce an included spray cone angle of approximately 20 to 40 degrees as fuel leaves orifice  31 . However, a less or greater spray angle may be needed depending upon air velocity, injection timing relative to intake valve timing, manifold pressure and the use of sequential or simultaneous port injection. The desired final result is for fuel to move quickly in all lateral directions from the outlet of orifice  31  toward the wall of intake manifold  4 . Spinner  15  which is shaped like a barbell has multiple angled cuts  16  and  17  in each end. Cuts  16  at its outlet are angled F at approximately 60 degrees. Total cross sectional area for cuts  16  should be approximately 4 times the cross sectional area of nozzle outlet  31 . The combined cross section area of cuts  16  can be changed to vary the included spray cone angle  12  in  FIG. 2 . Reduce the combined area of cuts  16  to increase the angle of spray  12 . Also, throat length of orifice  31  in  FIG. 3  will effect spray cone angle. A common throat length is 1 orifice diameter. A longer throat length reduces the angle of spray cone  12 . Cuts  17  at spinner  15 &#39;s inlet align spinner  15  coaxially in nozzle  30 , and their total open area is six or more times the area of outlet  31  to avoid any significant flow restriction. An angle H for cuts  17  is not critical, since the main function of end  17  is to align cuts  16  and offer no obstruction to flow. The end of spinner  15  at cuts  17  also serves as a location to “stake”, for example, spinner  15  to nozzle  30  so that spinner  15  will not rotate in response to fuel flow. 
     If supply pressure  2  in  FIG. 1  is 42 psi. and pressure drop across injector valve  21  and extension  33  up to nozzle  30  is 6 psi. then pressure  2  in  FIG. 2  should be increased to 48 psi. This results in the same atomizing pressure for nozzle  30  in  FIG. 2  as for injector  6  in  FIG. 1 . 
     An “O” ring  14  in  FIG. 3  seals nozzle  30  at reversing block  11 . During assembly, an axial force between nozzle  30  and block  11  is used to compress “O” ring  14  to avoid fuel leakage. For example, if fuel pressure at  2  in  FIG. 2  is 48 psi. and the area of “O” ring  14  is 0.1 sqin. then minimum axial force is 4.8 pounds. Actual force should be greater. While this compressive force is being applied to nozzle  30  and block  11  in  FIG. 3  against “O” ring  14 , a notch  13  in nozzle  30  is drilled using “pin” hole  27  as a guide. A pin installed through hole  27  and notch  13  secures nozzle  30  to block  11  while “O” ring  14  is in compression. A pin in hole  27  should be staked only after all final tests on injector assembly  21 A are satisfactory. 
     The use of “O” ring  14  in  FIG. 3  as a gasket to seal nozzle  30  at reversing block  11  may not be satisfactory for applications where excessive temperatures are encountered. In such cases, a welded or silver solder joint between nozzle  30  and reversing block  11  is more suitable. However, cleaning nozzle  30  or altering spray pattern  12  becomes much more difficult. 
     If injector assembly  21 A in  FIG. 2  is to replace injector  6  in  FIG. 1 , it should have comparable fuel flow capacity, spray droplet characterization and operating speed. Extension  33  should be made into a sub-assembly from all parts in  FIG. 3  except valve  21 . After injector valve  21  and extension sub-assembly  33  have been tested separately for capacity, operating speed, leaks, tight shut-off and spray pattern, injector valve  21  is joined to completed extension  33 . Glue surface  22  on injector valve  21  is glued to glue surface  18  of coupling ring  25 . An “O” ring  28  seals against injector surface  24  The glue joint between  18  and  22  must be make with a longitudinal compressive force greater than the longitudinal force that will result from maximum fuel pressure. 
     Assembled injector  21 A should be re-tested for capacity, tight shut-off, leakage, operating speed and spray pattern before installing in an engine. 
     The effectiveness of countercurrent fuel injection can be monitored by measuring temperature rise across a vehicle&#39;s catalytic converter and comparing to conventional fuel injection in the same vehicle under the same simulated or real road conditions.