Abstract:
A fuel injection apparatus for use in a compression ignition engine comprises a first injector tip defining a first set of outlet orifices therethrough and a second injector tip defining a second set of outlet orifices therethrough. The first set of outlet orifices has a first conicity and the second set of outlet orifices has a second conicity. The first conicity is different from the second conicity.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to internal combustion engines, and relates more particularly to a direct injection compression ignition engine with a dual tip fuel injector and associated methods of fuel injection. 
       BACKGROUND 
       [0002]    Internal combustion engines burn a hydrocarbon-based fuel or another combustible fuel to convert the potential or chemical energy therein to mechanical power that can be used to perform work. Exhaust emissions from internal combustion engines may include constituents subject to government regulations. Design parameters of fuel injectors may impact these emissions by affecting fuel spray quality. 
         [0003]    U.S. Pat. No. 6,422,199 (“the &#39;199 patent”), entitled “Fuel Injector,” purports to address the problem of particulate emissions. The &#39;199 patent describes a fuel injector having first and second valve needles and corresponding first and second outlet openings. The design of the fuel injector disclosed in the &#39;199 patent, however, may produce particulate emissions that are still greater than optimum. Accordingly, there is a need for an improved fuel injector. 
       SUMMARY 
       [0004]    In one aspect of the disclosure, a fuel injection apparatus for use in a compression ignition engine includes a first injector tip defining a first set of outlet orifices therethrough and a second injector tip defining a second set of outlet orifices therethrough. The first set of outlet orifices has a first conicity and the second set of outlet orifices has a second conicity. The first conicity is different from the second conicity. 
         [0005]    In another aspect of the disclosure, the disclosure describes an engine includes an engine housing having at least one combustion chamber therein, a piston movable within the at least one combustion chamber and configured to compress air therein to a compression ignition condition, and a fuel injection apparatus. The fuel injection apparatus defines at least a portion of the at least one combustion chamber. The fuel injection apparatus has a first injector tip defining a first set of outlet orifices therethrough and a second injector tip defining a second set of outlet orifices therethrough. The fuel injection apparatus is configured to selectively inject fuel into the combustion chamber via at least one of the first injector tip and the second injector tip. The first set of outlet orifices has a first conicity and the second set of outlet orifices has a second conicity that is different from the first conicity. 
         [0006]    In yet another aspect of the disclosure, a method of operating an internal combustion engine includes a step of injecting a first quantity of fuel into a combustion chamber of the engine via a first set of outlet orifices having a first conicity. The method further includes injecting a second quantity of fuel into the combustion chamber via a second set of outlet orifices having a second conicity. The method also includes igniting and burning the first quantity of fuel and the second quantity of fuel. The first conicity is different from the second conicity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic illustration of a system including an engine, a fuel injector, and an exhaust system, according to an aspect of the disclosure; 
           [0008]      FIG. 2  is a schematic illustration of a fuel injection system, according to an aspect of the disclosure; 
           [0009]      FIG. 3A  is a schematic cross-sectional view of a fuel injector, according to an aspect of the disclosure; 
           [0010]      FIG. 3B  is a schematic bottom view of the fuel injector shown in  FIG. 3A ; 
           [0011]      FIG. 4A  is a schematic cross-sectional view of a fuel injector, according to an aspect of the disclosure; 
           [0012]      FIG. 4B  is a schematic bottom view of the fuel injector shown in  FIG. 4A ; 
           [0013]      FIG. 5A  is a schematic cross-sectional view of a fuel injector, according to an aspect of the disclosure; 
           [0014]      FIG. 5B  is a schematic bottom view of the fuel injector shown in  FIG. 5A ; 
           [0015]      FIG. 6A  is a schematic cross-sectional view of a fuel injector, according to an aspect of the disclosure; and 
           [0016]      FIG. 6B  is a schematic bottom view of the fuel injector shown in  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Referring to  FIG. 1 , an engine system  10  includes an engine  12  which is connected to a fuel injector apparatus  16  and an exhaust system  18 . After fuel is injected into engine  12  by fuel injector apparatus  16  and burned, the combustion products are then exhausted from the engine  12  along an exhaust path  17  of exhaust system  18  that leads outside the engine  12  to an ambient environment of the engine  12 . Exhaust path  17  may include a diesel particulate filter  19  that removes particulates from the exhaust gas. 
         [0018]    With reference to  FIG. 2 , engine  12  further includes at least one cylinder  14  with a piston  21 , disposed at least partially therein. Cylinder  14  and the piston  21  at least partially define a combustion chamber  13 . Piston  21  may be coupled with a crankshaft via a connecting rod or other connecting structure known in the art. Engine  12  may be a compression ignition engine, for example a diesel engine. Alternatively, engine  12  may be a spark ignition engine, or any other type of reciprocating engine known in the art. Engine  12  may include at least one sensor  9  configured to sense values indicative of engine speed, engine load, combinations thereof, or any other engine operating parameter known in the art, and output corresponding signals indicative of an engine operating parameter to a controller  15 . 
         [0019]    Engine  12  might be constructed having only a single cylinder and single piston. Alternatively, engine  12  may include a plurality of cylinders and pistons, such as four, eight, 10, 12, or 16 or more cylinders depending upon the application. The arrangement of cylinders in engine  12  may include any known configuration, such as a V-pattern, in-line, radial, opposed, etc. In many aspects, size and space will be at a premium and thus a V-pattern engine, for example, may be a practical design. 
         [0020]    Fuel injection apparatus  16  works in conjunction with a fuel delivery system  34  to deliver fuel to each combustion chamber  13  using first and second injector bodies  31   a,    31   b . Injector bodies  31   a,    31   b  each include an injector tip  20   a,    20   b,  respectively, at a proximate end, proximate to the cylinder  14 , and a fuel chamber  35   a,    35   b  at a distal end, distal to the cylinder  14 . Injector tips  20   a,    20   b  are each in selective fluid communication with fuel chambers  35   a ,  35   b,  respectively. Fuel flow to first fuel injector tip  20   a  and second fuel injector tip  20   b  is controlled by a valve  36   a,    36   b,  respectively, such as a needle valve. Valves  36   a,    36   b  are actuated between an open position, when the valve is lifted and injector tips  20   a,    20   b  are in fluid communication with fuel chambers  35   a,    35   b,  and a closed position, when the valve is lowered and injector tips  20   a,    20   b  are blocked from fluid communication with fuel chambers  35   a,    35   b,  by action of springs  37   a,    37   b  and pistons  39   a,    39   b,  for example. In the closed position, valves  36   a ,  36   b  press against a sealing surface  33   a,    33   b  of the injector bodies  31   a,    31   b  so as to block communication between the fuel chambers  35   a,    35   b  and the injector tips  20   a,    20   b.  Sealing surfaces  33   a,    33   b,  in combination with the distal ends of injector bodies  31   a,    3  lb define first and second fuel chambers  35   a,    35   b  which each have a first volume, respectively. Sealing surfaces  33   a,    33   b,  in combination with the proximal ends of injector bodies  31   a,    31   b  define first and second injector tips  20   a,    20   b  which each have a second volume, respectively. Valves  36   a,    36   b  may alternatively be actuated by a solenoid or other valve actuation structure known in the art. Additionally, a fuel injection apparatus with more than two fuel injector tips  20   a,    20   b  is also contemplated. 
         [0021]    Fuel injector tips  20   a,    20   b  further define a portion of the combustion chamber  13 . Fuel injector tips  20   a,    20   b  may be flush with a cylinder head  11  of the cylinder  14  or fuel injector tips  20   a,    20   b  may extend through the cylinder head  11  and project at least partially into the combustion chamber  13 . Each fuel injector tip  20   a,    20   b  has a plurality of outlet orifices  22   a ,  22   b  through which fuel is injected into a corresponding combustion chamber  13 . 
         [0022]    Fuel chambers  35   a,    35   b  are each in fluid communication with fuel delivery system  34 , which includes high pressure pumps  38 ,  40 , reservoir  50 , and low pressure pump  60 . Flow of fuel between the reservoir  50  and the engine  12  is controlled by controller  15  that actuates valves that are disposed throughout the fuel delivery system  34 , and may further actuate the low pressure pump  60  and one or more of the high pressure pumps  38 ,  40 . 
         [0023]    High pressure pump  38  delivers fuel to injector tip  20   a  via a first fuel chamber  35   a . Delivery of fuel to injector tip  20   a  is controlled by a valve  42 , which is opened and closed by an actuator  44 . Similarly, delivery of fuel to injector tip  20   b  from high pressure pump  40  via a second fuel chamber  35   b  is controlled by a valve  48 , which is opened and closed by actuator  46 . First fuel chamber  35   a  may be in selective fluid communication with second fuel chamber  35   b  via a valve  62  which is opened and closed by actuator  64 . 
         [0024]    Fuel chambers  35   a,    35   b  are each also in fluid communication with a fuel reservoir  50 . Fuel may flow from fuel chamber  35   a  to fuel reservoir  50  via valve  52 , which is opened and closed by actuator  54 . Similarly, fuel may flow from fuel chamber  35   b  to fuel reservoir  50  via valve  56 , which is opened and closed by actuator  58 . Valves  52 ,  56  may be referred to as low pressure return valves. One or more low pressure pumps  60  may deliver fuel from the reservoir  50  to one or more of the high pressure pumps  38 ,  40 . 
         [0025]    Any of the actuators  44 ,  48 ,  54 ,  58 ,  64  may be connected to and controlled by controller  15 . Actuators  44 ,  48 ,  54 ,  58 ,  64  may be solenoid actuators, pneumatic actuators, hydraulic actuators, or other actuator known in the art. 
         [0026]    With reference now to  FIGS. 3A-6B , orifices  22   a,    22   b  of injection tips  20   a,    20   b  may have various different geometries. Specifically, orifices  22   a  and  22   b  may have different conicities. Conicity for each orifice may be quantified based on a difference between inlet diameter  70   a,    70   b  and outlet diameter  72   a,    72   b  over a length of the orifice ((inlet diameter  70 −outlet diameter  72 )/length). The length of the orifice may extend from the inlet of the orifice to the exit of the orifice, which may coincide with a thickness of the corresponding injector body local to the orifice. 
         [0027]    For example, with reference to tip  20   a  shown in  FIG. 3A , orifices  22   a  have a straight conicity such that the inlet diameter  70   a  minus the outlet diameter  72   a  divided by the length is zero. In contrast, with reference to tip  20   b  shown in  FIG. 3A , orifices  22   b  have a converging conicity, such that the inlet diameter  70   b  minus the outlet diameter  72   b  divided by the length is greater than zero. With reference now to  FIG. 4A , orifices  22   a  may also have a diverging conicity, such that the inlet diameter  70   a  minus the outlet diameter  72   a  divided by the length is less than 0. Accordingly, fuel injector apparatus  16  may have one tip  20   a  with orifices  22   a  having a straight conicity and one tip  20   b  with orifices  22   b  having a converging conicity (as shown in  FIGS. 3A and 3B ), one tip  20   a,    20   b  with orifices  22   a,    22   b  having a diverging conicity and one tip  20   a,    20   b  with orifices  22   a,    22   b  having a converging conicity (as shown in  FIGS. 4A and 4B ), or one tip  20   a,    20   b  with orifices  22   a,    22   b  having a straight conicity and one tip  20   a,    20   b  with orifices  22   a,    22   b  having a diverging conicity (as shown in  FIGS. 5A and 5B ). For example, one tip  20   a,    20   b  may have orifices with a conicity in the range of −0.5 to +0.5 and one tip with orifices with a conicity in the range of 1.0 to 2.0. 
         [0028]    Geometry of orifices  22   a,    22   b  may further vary in terms of whether the walls of the orifices are concave, convex, or straight. While  FIGS. 3A ,  4 A, and  5 A show straight orifice walls, orifices  22   a  in  FIG. 6A  have concave walls and orifices  22   b  have convex walls. 
         [0029]    While each tip  20   a,    20   b  may have orifices  22   a,    22   b  that are identical to each other in terms of conicity and orifice wall geometry, each tip  20   a,    20   b  may also have orifices  22   a,    22   b  that are different from one another. For example, a tip  20   a,    20   b  may have some orifices with a conicity of zero and straight walls and other orifices with a converging conicity and convex walls. 
         [0030]    In addition to conicity and orifice wall geometry, the number of orifices  22   a,    22   b  in tips  20   a,    20   b,  respectively, may vary. For example, while each tip  20   a,    20   b  in  FIGS. 3A-6B  are shown with six orifices, fuel injector apparatus  16  may include one tip  20   a,    20   b  with five to seven orifices and another tip  20   a,    20   b  with six to eight orifices, for example. However, it will be appreciated that the number of the orifices in each tip  20   a,    20   b  may be selected from any number to suit a particular application. 
         [0031]    Orifices  22   a,    22   b  may be formed by laser drilling holes in injector tip  20   a,    20   b . Alternatively, other methods of forming orifices may be used. For instance, orifices  22   a,    22   b  may be formed via coating or plating larger holes down to the desired diameter, or casting ceramic injector nozzles with small wires therein, and burning the wires away during curing of the nozzles. 
       INDUSTRIAL APPLICABILITY 
       [0032]    Design parameters of a fuel injector, such as the geometry of fuel injector apparatus  16  and the configuration of fuel delivery system  34  may have significant impacts on exhaust emissions. These parameters can affect not only fuel spray quality, but also timing of main injection and post injection shots, which in turn may affect concentrations of particular constituents in the exhaust emissions. Certain configurations of the fuel injector apparatus  16  described herein can reduce particulate matter (PM) emissions by 20-30%. In-cylinder PM emission reduction at these levels may obviate the need for a diesel particulate filter  19  in order for the engine  12  to meet a particular PM emissions target. Additionally, such configurations may also improve brake specific fuel consumption through enhanced combustion performance, reduction of exhaust backpressure, or combinations thereof. 
         [0033]    With reference again to  FIG. 2 , during operation, actuator  44  is energized to open valve  42  so as to selectively admit a flow of fuel from the high pressure pump  38  into the fuel chamber  35   a.  Fuel pressure in chamber  35   a  acts on the piston  39   a  to compress the spring  37   a , thereby translating the valve  36   a  in the distal direction relative to combustion chamber  13  to an open position such that fuel passes through orifices  22   a  of injector tip  20   a.  High pressure pump  38  may be configured to deliver fuel to tip  20   a  at a pressure that is sufficient to atomize the fuel. 
         [0034]    When actuator  44  is energized, actuator  54  may be de-energized so as to close valve  52 . Actuator  64  may also be de-energized such that the only flow path for fuel from the fuel chamber  35   a  is through orifices  22   a.  Actuator  44  is then de-energized, which closes valve  42 . Flow of fuel from fuel chamber  35   a  continues until valve  36   a  seats and stops fuel from high pressure pump  38  from entering tip  20   a.  When actuator  44  is de-energized, actuator  54  may be energized, which opens valve  52  so that high pressure fuel in injector body  31   a  may pass into reservoir  50 . Actuator  64  may also be energized alternatively or in combination with actuator  54 , which opens valve  62  so that high pressure fuel in injector body  31   a  may flow into injector body  31   b.  Valve  36   a  also lowers to its closed position, with or without opening of valves  52 ,  62 . Reduction of pressure within injector body  31   a  when valves  52 ,  62  open augments movement of valve  36   a  to its closed position. When actuator  64  is de-energized and valve  62  is closed, pressure in chamber  35   b  is not affected by pressure changes in chamber  35   a.  With chamber  35   b  separated from chamber  35   a  by valve  62 , actuator  48  may be energized before, during, or after fuel injection through orifices  22   a  so as to cause fuel injection through orifices  22   b.    
         [0035]    Fuel may also be injected through injector tip  20   b  from high pressure pump  40 . Specifically, actuator  48  is energized to open valve  46  so as to selectively admit a flow of fuel from the high pressure pump  40  into the fuel chamber  35   b.  Fuel pressure in chamber  35   b  acts on the piston  39   b  to compress the spring  37   b,  thereby translating the valve  36   b  in the distal direction relative to combustion chamber  13  to an open position such that fuel passes through orifices  22   b  of injector tip  20   b.    
         [0036]    When actuator  48  is energized, actuator  58  may be de-energized so as to close valve  56 . Actuator  64  is also de-energized such that the only passages for fuel from high pressure pump  40  are through orifices  22   b.  Flow of fuel from fuel chamber  35   b  continues until valve  36   b  seats and stops fuel from high pressure pump  40  from entering tip  20   b.  When actuator  48  is de-energized, actuator  58  may be energized, which opens valve  56  so that high pressure fuel in injector body  31   b  may pass into reservoir  50 . Actuator  64  may also be energized alternatively or in combination with actuator  58 , which opens valve  62  so that high pressure fuel in injector body  31   b  may flow into injector body  31   a.  Valve  36   b  lowers to its closed position, with or without opening of valves  56 ,  62 . Reduction of pressure within injector body  31   b  when valves  56 ,  62  open augments movement of valve  36   b  to its closed position. 
         [0037]    Injection through tip  20   b  ends when actuator  48  is de-energized, which closes valve  46  and stops fuel from high pressure pump  40  from entering tip  20   b.  When actuator  48  is de-energized, actuator  58  is energized, which opens valve  56  so that high pressure fuel in injector body  31   b  passes into reservoir  50 . Actuator  64  may also be energized, which opens valve  62  so that high pressure fuel in injector body  31   b  passes into injector body  31   a.  Valve  36   b  also lowers to its closed position. Similar to the description above, reduction of pressure within injector body  31   b  when valves  56 ,  62  open augments movement of valve  36   b  to its closed position. When actuator  64  is de-energized and valve  62  is closed, pressure in chamber  35   a  is not affected by pressure changes in chamber  35   b.  With chamber  35   a  separated from chamber  35   b  by valve  62 , actuator  44  may be energized before, during, or after fuel injection through orifices  22   b  so as to cause fuel injection through orifices  22   a.    
         [0038]    Fuel may be injected through injector tip  20   a  before, during, or after fuel is injected through injector tip  20   b.  Fuel may be injected multiple times through one injector tip  20   a,    20   b  without intervening injection through the other injection tip during a compression and expansion cycle of the piston  21  within the cylinder  14 . Whether from tip  20   a  or tip  20   b,  the first injection may be the main injection and the second injection may be the post injection. It will be appreciated that a pre-injection of fuel may precede the main injection of fuel. A quantity of fuel in the main injection may be larger than a quantity of fuel in a pre-injection, a post injection, or both. 
         [0039]    The post injection may effectively reduce particular constituents of engine  12  emissions compared to systems that do not have a post injection. For example, controller  15  may open valve  46  shortly after opening valve  42  and before closing valve  42 , such that the time windows for injection through tips  20   a,    20   b  overlap. Alternatively, controller  15  may close valve  42  shortly before opening valve  46  such that the time windows for injection through tips  20   a,    20   b  do not overlap. Alternatively still, controller  15  may open valve  46  before opening valve  42  such that fuel is injected into combustion chamber  13  first through tip  20   b  and then through tip  20   a  such that the time windows do or do not overlap. During opening and closing of valves  42 ,  46 ,  52 , and  56 , valve  62  may also be opened and closed via actuator  64  so as to optimize pressures within injector bodies  31   a,    31   b.  By controlling separation of chamber  35   a  from chamber  35   b  using valve  62 , cavitation within cylinder  13  may be minimized 
         [0040]    Applicants discovered that a particular outlet orifice  22   a  conicity may be desirable at a particular engine speed or load, and that another outlet orifice  22   b  conicity may be desirable at another engine speed or load. Applicants also discovered that concentration of particular emissions constituents may be more sensitive to the conicity of the orifices delivering the main fuel injection than the conicity of the orifices delivering a pre-injection or a post-injection. Accordingly, engine  12  may be configured such that at one speed or load, tip  20   a  delivers the main injection and tip  20   b  delivers the post injection, and at another speed or load, tip  20   b  delivers the main injection and tip  20   a  delivers the post injection. 
         [0041]    Valves  52 ,  56  that control flow to reservoir  50  may serve both damping and regulating functions for injector bodies  31   a,    31   b  with or without active control of actuators  54 ,  58 . Specifically, valves  52  and  56  may have a pressure limit such that whenever fuel pressure in injector bodies  31   a,    31   b  is above a certain limit, valves  52 ,  56  open, respectively, without energizing actuators  54 ,  58 . By providing these damping and regulating functions, valves  52 ,  56  may prolong the life of fuel injector apparatus  16 . 
         [0042]    It will be appreciated that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. References to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to limit the scope of the disclosure more generally. Language of distinction with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure. 
         [0043]    Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.