Patent Publication Number: US-11045776-B2

Title: Methods and systems for a fuel injector

Description:
FIELD 
     The present description relates generally to a fuel injector comprising one or more features to decrease soot formation. 
     BACKGROUND/SUMMARY 
     In engines, air is drawn into a combustion chamber during an intake stroke by opening one or more intake valves. Then, during the subsequent compression stroke, the intake valves are closed, and a reciprocating piston of the combustion chamber compresses the gases admitted during the intake stroke, increasing the temperature of the gases in the combustion chamber. Fuel is then injected into the hot, compressed gas mixture in the combustion chamber. The mixture may be ignited via a spark or upon reaching a threshold pressure. The combusting air-fuel mixture pushes on the piston, driving motion of the piston, which is then converted into rotational energy of a crankshaft. 
     However, the inventors have recognized potential issues with such engines. As one example, fuel may not mix evenly with the air in the combustion chamber, leading to the formation of dense fuel pockets in the combustion chamber. These dense regions of fuel may produce soot as the fuel combusts. As such, engines may include particulate filters for decreasing an amount of soot and other particulate matter in their emissions. However, such particulate filters lead to increased manufacturing costs and increased fuel consumption during active regeneration of the filter. 
     Modern technologies for combating engine soot output and poor air/fuel mixing may include features for entraining air with the fuel prior to injection. This may include passages arranged in an injector body, as an insert into the engine head deck surface, or integrated in an engine head. Ambient air mixes with the fuel, cooling the injection temperature, prior to delivering the mixture to the compressed air in the cylinder. By entraining cooled air with the fuel prior to injection, a lift-off length is lengthened and start of combustion is retarded. This limits soot production through a range of engine operating conditions, reducing the need for a particulate filter. 
     However, the inventors herein have recognized potential issues with such injectors. As one example, the previously described fuel injectors may no longer sufficiently prevent soot production to a desired level in light of increasingly stringent emissions standards. Additionally, the previously described fuel injectors may only limit soot production in diesel engines, where air/fuel have a longer duration of time to mix before combustion than in spark-ignited engines. 
     In one example, the issues described above may be addressed by a system comprising an injector having a venturi-shaped nozzle, wherein the nozzle comprises a plurality of upstream twisted fins arranged in a venturi inlet of the nozzle, and where a leading edge of an upstream twisted fin of the plurality of upstream twisted fins is perpendicular to a trailing edge of the twisted fin. In this way, a swirl may be imparted onto a fuel mixture, which may improve mixing between the various fuel components and air and exhaust gases. 
     As one example, the injector may further comprise downstream twisted fins arranged in a venturi outlet. The downstream and upstream twisted fins may be similarly shaped, however, the fins may be offset to one another relative to a general direction of a fuel mixture flow. This may increase a likelihood of the fuel mixture contacting at least one of the upstream or downstream twisted fins. By doing this, soot production of the engine may be prevented and/or mitigated to an extent such that a particulate filter may be omitted from an exhaust system. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an engine of a hybrid vehicle. 
         FIG. 2  shows an example of a single injector nozzle. 
         FIGS. 3A and 3B  show a view of the upstream fins and the downstream fins, respectively. 
         FIG. 4  shows an example of a first embodiment of an air entrainment system being included with the injector nozzle. 
         FIG. 5  shows an example of a second embodiment of an air entrainment system being included with the injector nozzle. 
         FIGS. 6A and 6B  show an example of an injector tip comprising a curved shape to angle its nozzles, wherein the nozzles may include the nozzles of  FIGS. 2, 3A, 3B, 4, and 5 . 
         FIGS. 2-5  are shown approximately to scale, although other relative dimensions may be used, if desired. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to an injector nozzle having various features for promoting more complete combustion to decrease soot production from an engine. The engine may be arranged in a hybrid vehicle, such as the hybrid vehicle illustrated in  FIG. 1 . The injector may be a fuel injector in one example, however, it will be appreciated that the injector may inject other types and/or mixtures of liquids without departing from the scope of the present disclosure, wherein the liquids may include water, alcohol, reductants, bases, acids, catalysts, and the like. Additionally, the injector may be shaped to mix gases. The injector may comprise a venturi shape, wherein a venturi inlet and a venturi outlet may optionally comprise one or more features to promote a fuel mixture to swirl. More specifically, the venturi inlet may comprise one or more upstream fins, as shown in  FIGS. 2 and 3A . Additionally, the venturi outlet may comprise one or more downstream fins, as shown in  FIGS. 2 and 3B . The injector nozzle may further comprise a first embodiment of an air entrainment system, as shown in  FIG. 4 , or a second embodiment of an air entrainment system, as shown in  FIG. 5 , where the systems may direct combustion chamber gases to flow to a venturi throat of the nozzle to further increase mixing between the fuel mixture and the combustion chamber gases, which may adjust combustion conditions to conditions where soot may not be produced.  FIGS. 6A and 6B  show an example of an injector tip comprising a curved surface with a plurality of nozzle groups arranged circularly at different diameters. Due to the curvature of the injector tip, the nozzles of the various groups may be angled differently relative to a central axis of the injector.  FIGS. 2-5  are shown approximately to scale, although other relative dimensions may be used, if desired. 
       FIGS. 1-6B  show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. It will be appreciated that one or more components referred to as being “substantially similar and/or identical” differ from one another according to manufacturing tolerances (e.g., within 1-5% deviation). 
     Note that  FIGS. 3A, 3B, 4, and 5  show arrows indicating where there is space for gas to flow, and the solid lines of the device walls show where flow is blocked and communication is not possible due to the lack of fluidic communication created by the device walls spanning from one point to another. The walls create separation between regions, except for openings in the wall which allow for the described fluid communication. 
       FIG. 1  depicts an engine system  100  for a vehicle. The vehicle may be an on-road vehicle having drive wheels which contact a road surface. Engine system  100  includes engine  10  which comprises a plurality of cylinders.  FIG. 1  describes one such cylinder or combustion chamber in detail. The various components of engine  10  may be controlled by electronic engine controller  12 . 
     Engine  10  includes a cylinder block  14  including at least one cylinder bore  20 , and a cylinder head  16  including intake valves  152  and exhaust valves  154 . In other examples, the cylinder head  16  may include one or more intake ports and/or exhaust ports in examples where the engine  10  is configured as a two-stroke engine. The cylinder block  14  includes cylinder walls  32  with piston  36  positioned therein and connected to crankshaft  40 . The cylinder bore  20  may be defined as the volume enclosed by the cylinder walls  32 . The cylinder head  16  may be coupled to the cylinder block  14 , to enclose the cylinder bore  20 . Thus, when coupled together, the cylinder head  16  and cylinder block  14  may form one or more combustion chambers. In particular, combustion chamber  30  may be the volume included between a top surface  17  of the piston  36  and a fire deck  19  of the cylinder head  16 . As such, the combustion chamber  30  volume is adjusted based on an oscillation of the piston  36 . Combustion chamber  30  may also be referred to herein as cylinder  30 . The combustion chamber  30  is shown communicating with intake manifold  144  and exhaust manifold  148  via respective intake valves  152  and exhaust valves  154 . Each intake and exhaust valve may be operated by an intake cam  51  and an exhaust cam  53 . Alternatively, one or more of the intake and exhaust valves may be operated by an electromechanically controlled valve coil and armature assembly. The position of intake cam  51  may be determined by intake cam sensor  55 . The position of exhaust cam  53  may be determined by exhaust cam sensor  57 . Thus, when the valves  152  and  154  are closed, the combustion chamber  30  and cylinder bore  20  may be fluidly sealed, such that gases may not enter or leave the combustion chamber  30 . 
     Combustion chamber  30  may be formed by the cylinder walls  32  of cylinder block  14 , piston  36 , and cylinder head  16 . Cylinder block  14  may include the cylinder walls  32 , piston  36 , crankshaft  40 , etc. Cylinder head  16  may include one or more fuel injectors such as fuel injector  66 , one or more intake valves  152 , and one or more exhaust valves such as exhaust valves  154 . The cylinder head  16  may be coupled to the cylinder block  14  via fasteners, such as bolts and/or screws. In particular, when coupled, the cylinder block  14  and cylinder head  16  may be in sealing contact with one another via a gasket, and as such may the cylinder block  14  and cylinder head  16  may seal the combustion chamber  30 , such that gases may only flow into and/or out of the combustion chamber  30  via intake manifold  144  when intake valves  152  are opened, and/or via exhaust manifold  148  when exhaust valves  154  are opened. In some examples, only one intake valve and one exhaust valve may be included for each combustion chamber  30 . However, in other examples, more than one intake valve and/or more than one exhaust valve may be included in each combustion chamber  30  of engine  10 . 
     The cylinder walls  32 , piston  36 , and cylinder head  16  may thus form the combustion chamber  30 , where a top surface  17  of the piston  36  serves as the bottom wall of the combustion chamber  30  while an opposed surface or fire deck  19  of the cylinder head  16  forms the top wall of the combustion chamber  30 . Thus, the combustion chamber  30  may be the volume included within the top surface  17  of the piston  36 , cylinder walls  32 , and fire deck  19  of the cylinder head  16 . 
     In some examples, each cylinder of engine  10  may include a spark plug  192  for initiating combustion. Ignition system  190  can provide an ignition spark to cylinder  14  via spark plug  192  in response to spark advance signal SA from controller  12 , under select operating modes. However, in some embodiments, spark plug  192  may be omitted, such as where engine  10  may initiate combustion by auto-ignition or by injection of fuel as may be the case with some diesel engines. 
     Fuel injector  66  may be positioned to inject fuel directly into combustion chamber  30 , which is known to those skilled in the art as direct injection  30 . Fuel injector  66  delivers liquid fuel in proportion to the pulse width of signal FPW from controller  12 . Fuel is delivered to fuel injector  66  by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail. Fuel injector  66  is supplied operating current from driver  68  which responds to controller  12 . In some examples, the engine  10  may be a gasoline engine, and the fuel tank may include gasoline, which may be injected by injector  66  into the combustion chamber  30 . However, in other examples, the engine  10  may be a diesel engine, and the fuel tank may include diesel fuel, which may be injected by injector  66  into the combustion chamber. Further, in such examples where the engine  10  is configured as a diesel engine, the engine  10  may include a glow plug to initiate combustion in the combustion chamber  30 . 
     In some examples, the injector  66  may comprise one or more features to reduce the temperature of air that is entrained by the fuel injected from the injector  66 . Specifically, when fuel exits the injector  66  during fuel injection, it may travel a distance while mixing with air in a nozzle before combusting. In the description herein, the distance the fuel spray travels before combusting may be referred to as the “lift-off length.” In particular, the lift-off length may refer to the distance the injected fuel travels before the combustion process begins. Thus, the lift-off length may be a distance between an orifice of the injector  66  from which the fuel exits the injector  66 , to a point in the combustion chamber  30  at which combustion of the fuel occurs. 
     The injector  66  may decrease the temperature of the gases that mix with the fuel prior to combustion in the combustion chamber  30 . Furthermore, the injector  66  may enable a higher spray velocity, within and at a nozzle of the injector  66 , thereby increasing air entrainment with the fuel injection and fuel penetration into the combustion chamber  30 . In this way, the lift-off length of the fuel spray may be increased and/or an amount of air entrainment in the fuel spray may be increased. The nozzle may be in fluidic communication with combustion chamber  30 , such that gases in the combustion chamber  30  may enter the one or more flow-through passages of the nozzle and be recirculated back into the combustion chamber  30 . As one example, intake air, and/or exhaust gas, introduced into the combustion chamber  30  during an intake stroke, may be pushed into the nozzle during all or a portion of the compression stroke. 
     Intake manifold  144  is shown communicating with optional electronic throttle  62  which adjusts a position of throttle plate  64  to control airflow to engine cylinder  30 . This may include controlling airflow of boosted air from intake boost chamber  146 . In some embodiments, throttle  62  may be omitted and airflow to the engine may be controlled via a single air intake system throttle (AIS throttle)  82  coupled to air intake passage  42  and located upstream of the intake boost chamber  146 . In yet further examples, throttle  82  may be omitted and airflow to the engine may be controlled with the throttle  62 . 
     In some embodiments, engine  10  is configured to provide exhaust gas recirculation, or EGR. When included, EGR may be provided as high-pressure EGR and/or low-pressure EGR. In examples where the engine  10  includes low-pressure EGR, the low-pressure EGR may be provided via EGR passage  135  and EGR valve  138  to the engine air intake system at a position downstream of air intake system (AIS) throttle  82  and upstream of compressor  162  from a location in the exhaust system downstream of turbine  164 . EGR may be drawn from the exhaust system to the intake air system when there is a pressure differential to drive the flow. A pressure differential can be created by partially closing AIS throttle  82 . Throttle plate  84  controls pressure at the inlet to compressor  162 . The AIS may be electrically controlled and its position may be adjusted based on optional position sensor  88 . 
     Ambient air is drawn into combustion chamber  30  via intake passage  42 , which includes air filter  156 . Thus, air first enters the intake passage  42  through air filter  156 . Compressor  162  then draws air from air intake passage  42  to supply boost chamber  146  with compressed air via a compressor outlet tube (not shown in  FIG. 1 ). In some examples, air intake passage  42  may include an air box (not shown) with a filter. In one example, compressor  162  may be a turbocharger, where power to the compressor  162  is drawn from the flow of exhaust gases through turbine  164 . Specifically, exhaust gases may spin turbine  164  which is coupled to compressor  162  via shaft  161 . A wastegate  72  allows exhaust gases to bypass turbine  164  so that boost pressure can be controlled under varying operating conditions. Wastegate  72  may be closed (or an opening of the wastegate may be decreased) in response to increased boost demand, such as during an operator pedal tip-in. By closing the wastegate, exhaust pressures upstream of the turbine can be increased, raising turbine speed and peak power output. This allows boost pressure to be raised. Additionally, the wastegate can be moved toward the closed position to maintain desired boost pressure when the compressor recirculation valve is partially open. In another example, wastegate  72  may be opened (or an opening of the wastegate may be increased) in response to decreased boost demand, such as during an operator pedal tip-out. By opening the wastegate, exhaust pressures can be reduced, reducing turbine speed and turbine power. This allows boost pressure to be lowered. 
     However, in alternate embodiments, the compressor  162  may be a supercharger, where power to the compressor  162  is drawn from the crankshaft  40 . Thus, the compressor  162  may be coupled to the crankshaft  40  via a mechanical linkage such as a belt. As such, a portion of the rotational energy output by the crankshaft  40 , may be transferred to the compressor  162  for powering the compressor  162 . 
     Compressor recirculation valve  158  (CRV) may be provided in a compressor recirculation path  159  around compressor  162  so that air may move from the compressor outlet to the compressor inlet so as to reduce a pressure that may develop across compressor  162 . A charge air cooler  157  may be positioned in boost chamber  146 , downstream of compressor  162 , for cooling the boosted aircharge delivered to the engine intake. However, in other examples as shown in  FIG. 1 , the charge air cooler  157  may be positioned downstream of the electronic throttle  62  in an intake manifold  144 . In some examples, the charge air cooler  157  may be an air to air charge air cooler. However, in other examples, the charge air cooler  157  may be a liquid to air cooler. 
     In the depicted example, compressor recirculation path  159  is configured to recirculate cooled compressed air from downstream of charge air cooler  157  to the compressor inlet. In alternate examples, compressor recirculation path  159  may be configured to recirculate compressed air from downstream of the compressor and upstream of charge air cooler  157  to the compressor inlet. CRV  158  may be opened and closed via an electric signal from controller  12 . CRV  158  may be configured as a three-state valve having a default semi-open position from which it can be moved to a fully-open position or a fully-closed position. 
     Universal Exhaust Gas Oxygen (UEGO) sensor  126  is shown coupled to exhaust manifold  148  upstream of emission control device  70 . Emission control device may be a catalytic converter and as such may also be referred to herein as catalytic converter  70 . Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor  126 . Converter  70  may include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Converter  70  can be a three-way type catalyst in one example. While the depicted example shows UEGO sensor  126  upstream of turbine  164 , it will be appreciated that in alternate embodiments, UEGO sensor may be positioned in the exhaust manifold downstream of turbine  164  and upstream of convertor  70 . Additionally or alternatively, the converter  70  may comprise a diesel oxidation catalyst (DOC) and/or a diesel cold-start catalyst. 
     In some examples, a particulate filter (PF)  74  may be coupled downstream of the emission control device  70  to trap soot in a direction of exhaust gas flow. In some examples, there may exist a selective catalytic reduction device and/or a lean NO x  trap between the converter  70  and the PF  74 . The PF  74  may be manufactured from a variety of materials including cordierite, silicon carbide, and other high temperature oxide ceramics. The PF  74  may be periodically regenerated in order to reduce soot deposits in the filter that resist exhaust gas flow. Filter regeneration may be accomplished by heating the filter to a temperature that will burn soot particles at a faster rate than the deposition of new soot particles, for example, 400-600° C. 
     However, in other examples, due to the inclusion of mixing and air entrainment features in at least one nozzle of the fuel injector  66 , PF  74  may not be included in the engine  10 . As such soot production during the combustion cycle may be reduced. In some examples, soot levels may be reduced to approximately zero due to the increased commingling of fuel and air prior to combustion/ignition of the mixture in the combustion chamber  30 . As such, approximately no soot (e.g., zero soot) may be produced by engine  10  during the combustion cycle in some examples. In other examples, due to the features of the injector, soot production may be reduced and as such, the PF  74  may be regenerated less frequently, reducing fuel consumption. 
     During the combustion cycle, each cylinder within engine  10  may undergo a four stroke cycle including: an intake stroke, compression stroke, power stroke, and exhaust stroke. During the intake stroke and power stroke, the piston  36  moves away from the cylinder head  16  towards a bottom of the cylinder increasing the volume between the top of the piston  36  and the fire deck  19 . The position at which piston  36  is near the bottom of the cylinder and at the end of its intake and/or power strokes (e.g., when combustion chamber  30  is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). Conversely, during the compression and exhaust strokes, the piston  36  moves away from BDC towards a top of the cylinder (e.g., fire deck  19 ), thus decreasing the volume between the top of the piston  36  and the fire deck  19 . The position at which piston  36  is near the top of the cylinder and at the end of its compression and/or exhaust strokes (e.g., when combustion chamber  30  is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). Thus, during the intake and power strokes, the piston  36  moves from TDC to BDC, and during the compression and exhaust strokes, the piston  36  moves from BDC to TDC. 
     Further, during the intake stroke, generally, the exhaust valves  154  close and the intake valves  152  open to admit intake air into the combustion chamber  30 . During the compression stroke, both valves  152  and  154  may remain closed, as the piston  36  compresses the gas mixture admitted during the intake stroke. During the compression stroke, gases in the combustion chamber  30  may be pushed into the fuel injector  66  due to the positive pressure created by the piston  36  as it travels towards the injector  66 . The gases from the combustion chamber  30  may dissipate heat through one or more of the cylinder head  16  and ambient air via conduction and/or convection. As such, the temperature of the gases in the injector  66  may be reduced relative to the temperature of the gases in the combustion chamber  30 . 
     When the piston  36  is near or at TDC during the compression and/or power stroke, fuel is injected into the combustion chamber  30  by injector  66 . During the ensuing power stroke, the valves  152  and  154  remain closed, as the expanding and combusting fuel and air mixture pushes the piston  36  towards BDC. In some examples, fuel may be injected prior to the piston  36  reaching TDC, during the compression stroke. However, in other examples, fuel may be injected when the piston  36  reaches TDC. In yet further examples, fuel may be injected after the piston  36  reaches TDC and begins to translate back towards BDC during the power stroke. In yet further examples, fuel may be injected during both the compression and power strokes. 
     Fuel may be injected over a duration. An amount of fuel injected and/or the duration over which fuel is injected may be varied via pulse width modulation (PWM) according to one or more linear or non-linear equations. Further, the injector  66  may include a plurality of injection orifices, and an amount of fuel injected out of each orifice may be varied as desired. 
     The injected fuel travels through a volume of the nozzle of the injector  66  before entering the combustion chamber  30 . Said another way, the nozzle may include air passages and fuel passages for entraining air and fuel, wherein the passages are located inside the combustion chamber  30 . However, the passages are defined by surfaces of the nozzle and fuel injector body and fuel and air flow through these passages before flowing outside of the nozzle and into the combustion chamber  30  to mix with unmixed combustion chamber gases. The flow of air and fuel through the nozzle will be described in greater detail below. 
     During the exhaust stroke, the exhaust valves  154  may open to release the combusted air-fuel mixture to exhaust manifold  148  and the piston  36  returns to TDC. Exhaust gases may continue to flow from the exhaust manifold  148 , to the turbine  164  via exhaust passage  180 . 
     Both the exhaust valves  154  and the intake valves  152  may be adjusted between respective closed first positions and open second positions. Further, the position of the valves  154  and  152  may be adjusted to any position between their respective first and second positions. In the closed first position of the intake valves  152 , air and/or an air/fuel mixture does not flow between the intake manifold  144  and the combustion chamber  30 . In the open second position of the intake valves  152 , air and/or an air/fuel mixture flows between the intake manifold  144  and the combustion chamber  30 . In the closed second position of the exhaust valves  154 , air and/or an air fuel mixture does not flow between the combustion chamber  30  and the exhaust manifold  148 . However, when the exhaust valves  154  is in the open second position, air and/or an air fuel mixture may flow between the combustion chamber  30  and the exhaust manifold  148 . 
     Note that the above valve opening and closing schedule is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. 
     Controller  12  is shown in  FIG. 1  as a microcomputer including: microprocessor unit  102 , input/output ports  104 , read-only memory  106 , random access memory  108 , keep alive memory  110 , and a conventional data bus. Controller  12  is shown receiving various signals from sensors coupled to engine  10 , in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor  112  coupled to cooling sleeve  114 ; a position sensor  134  coupled to an input device  130  for sensing input device pedal position (PP) adjusted by a vehicle operator  132 ; a knock sensor for determining ignition of end gases (not shown); a measurement of engine manifold pressure (MAP) from pressure sensor  121  coupled to intake manifold  144 ; a measurement of boost pressure from pressure sensor  122  coupled to boost chamber  146 ; an engine position sensor from a Hall effect sensor  118  sensing crankshaft  40  position; a measurement of air mass entering the engine from sensor  120  (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor  58 . Barometric pressure may also be sensed (sensor not shown) for processing by controller  12 . In a preferred aspect of the present description, Hall effect sensor  118  produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined. The input device  130  may comprise an accelerator pedal and/or a brake pedal. As such, output from the position sensor  134  may be used to determine the position of the accelerator pedal and/or brake pedal of the input device  130 , and therefore determine a desired engine torque. Thus, a desired engine torque as requested by the vehicle operator  132  may be estimated based on the pedal position of the input device  130 . 
     In some examples, vehicle  5  may be a hybrid vehicle with multiple sources of torque available to one or more vehicle wheels  59 . In other examples, vehicle  5  is a conventional vehicle with only an engine, or an electric vehicle with only electric machine(s). In the example shown, vehicle  5  includes engine  10  and an electric machine  61 . Electric machine  61  may be a motor or a motor/generator. Crankshaft  40  of engine  10  and electric machine  61  are connected via a transmission  54  to vehicle wheels  59  when one or more clutches  56  are engaged. In the depicted example, a first clutch  56  is provided between crankshaft  40  and electric machine  61 , and a second clutch  56  is provided between electric machine  61  and transmission  54 . Controller  12  may send a signal to an actuator of each clutch  56  to engage or disengage the clutch, so as to connect or disconnect crankshaft  40  from electric machine  61  and the components connected thereto, and/or connect or disconnect electric machine  61  from transmission  54  and the components connected thereto. Transmission  54  may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various manners including as a parallel, a series, or a series-parallel hybrid vehicle. 
     Electric machine  61  receives electrical power from a traction battery  58  to provide torque to vehicle wheels  59 . Electric machine  61  may also be operated as a generator to provide electrical power to charge battery  58 , for example during a braking operation. 
     The controller  12  receives signals from the various sensors of  FIG. 1  and employs the various actuators of  FIG. 1  to adjust engine operation based on the received signals and instructions stored on a memory of the controller. For example, adjusting a fuel injection may include adjusting an actuator of the injector  66  to move to or away from a nozzle of the injector  66  so that fuel may flow to the combustion chamber  30 . 
     Turning now to  FIG. 2 , it shows an embodiment  200  of a fuel injector nozzle  210  which may be arranged in a fuel injector, such as fuel injector  66  of  FIG. 1 . Additionally or alternatively, the fuel injector nozzle  210  may be arranged in a fuel injector positioned to inject from a fire deck (e.g., fire deck  19  of  FIG. 1 ) and/or from a side wall of a combustion chamber (e.g., combustion chamber  30  of  FIG. 1 ). The fuel injector nozzle  210  may be the only nozzle of a fuel injector or may be one of a plurality of similarly shaped nozzles of the fuel injector. Additionally or alternatively, if the fuel injector comprises a plurality of nozzles, the other nozzles may be shaped differently than the fuel injector nozzle  210 . 
     Herein, the fuel injector nozzle  210  may be defined as a passage and/or opening of an injector shaped to expel a fluid out of the injector to a different component. For example, if the injector is a fuel injector, then the fuel injector nozzle  210  may function as an outlet of the fuel injector, wherein fuel flows through the fuel injector nozzle  210  and out of the fuel injector. In one example, the fuel injector nozzle  210  may define a nozzle opening of a fuel injector tip. 
     An axis system  280  is shown comprising three axes, namely an x-axis parallel to a horizontal direction, a y-axis parallel to a vertical direction, and a z-axis perpendicular to each of the x- and y-axes. A general direction of fuel mixture flow  292  may be substantially parallel to the y-axis. A central axis  299  of the fuel injector nozzle  210  may be parallel to each of the general direction of fuel mixture flow  292  and the y-axis. 
     The fuel injector nozzle  210  comprises a body  212  having an hourglass and/or venturi-shape. More specifically, the body  212  comprises a venturi inlet  220 , a venturi outlet  230 , and a venturi throat  240 . Diameter  290  may be equal to a largest diameter of the venturi inlet  220  and the venturi outlet  230 . 
     The venturi inlet  220  may comprise an inlet opening  222 , which may correspond to the largest diameter of the venturi inlet. The inlet opening  222  may be shaped to receive a fuel mixture from a fuel sac or similar portion of a fuel injector. The venturi inlet  220  may constrict in a downstream direction, parallel to the general direction of fuel flow  292 . Thus, the diameter of the venturi inlet  220  decreases as it approaches the venturi throat  240 . 
     A fin  250  may be arranged in the venturi inlet  220 . The fin  250  may extend from the inlet opening  222  to a beginning of the venturi throat  240  (e.g., dashed line  294 ). The fin  250  may twist relative to the central axis  299  of the body  212 . A twist of the fin  250  may result in a leading edge  252  being offset with a trailing edge  254  by an angle, wherein the angle may be substantially equal to 90°. Thus, the leading edge  252  may be perpendicular to the trailing edge  254  due to a curvature of the fin  250 . 
     The fin  250  may be physically coupled to a surface of the venturi inlet  220  for its entire length. As such, a first longitudinal side  256  may be in face-sharing contact with the surface of the venturi inlet  220 , wherein the first longitudinal side  256  may be physically coupled to the surface of the venturi inlet  220  via one or more of welds, fusions, adhesives, and fasteners. A second longitudinal side  258  may be free from the surface of the venturi inlet  220  such that fuel may contact and travel along the second longitudinal side. A width  251  of the fin  250  may be measured from the first longitudinal side  256  to the second longitudinal side  258 . In some examples, the width  251  may decrease in the downstream direction parallel to the general direction of fuel flow  292 . In one example, the width  251  is substantially equal to a percentage of the diameter of the venturi inlet  220 . The width  251  may be between 5 to 50% of the diameter of the venturi inlet. In some examples, additionally or alternatively, the width  251  may be between 20 to 45% of the diameter of the venturi inlet  220 . In one example, the width  251  is 40% of the diameter of the venturi inlet. 
     Additionally or alternatively, the width  251  of the fin  250  may be substantially constant from the leading edge  252  to the trailing edge  254 . As such, even though the venturi inlet  220  narrows toward the venturi throat  240 , the fin  250  does not. In this way, a distance between the fin  250  and the central axis  299  may decrease in the general direction of fuel flow  292 . By doing this, a likelihood of fuel contacting the fin  250  may increase as the fuel in the venturi inlet  220  approaches the venturi throat  220 . 
     The venturi outlet  230  may be shaped similarly to the venturi inlet  220 , except that the venturi outlet  230  increases in diameter in the downstream direction parallel to the general direction of fuel flow  292 . In some examples, additionally or alternatively, a length, measured along the central axis  299 , of the venturi outlet  230  may be equal to or different than a length of the venturi inlet  220 . In one example, the length of the venturi outlet  230  is greater than the length of the venturi inlet  220 . By elongating the venturi outlet  230  relative to the venturi inlet  220 , combustion chamber gases and the fuel mixture may have a greater distance to mix. That is to say, if the fuel injector nozzle  210  comprises air entrainment features that direct air from a combustion chamber or other air source to the venturi throat  240 , then the air and fuel may have a greater area to mix in before being injected into the combustion chamber, a fuel injector duct, or the like if the venturi outlet  230  is elongated relative to the venturi inlet  220 . 
     The venturi outlet  240  may further comprise a fin  260 . Herein, fin  250  may be referred to as upstream fin  250  and fin  260  may be referred to as downstream fin  260 . The downstream fin  260  may be shaped identically to the upstream fin  250 . As such, the downstream fin  260  may comprise a leading edge  262  arranged at an upstream extreme end of the venturi outlet  230  and a trailing edge  264  arranged at a downstream extreme end of the venturi outlet  230 , wherein the downstream extreme end of the venturi outlet  230  comprises an opening  232  for expelling a fuel injection mixture into the combustion chamber or the like. The leading edge  262  may be perpendicular to the trailing edge  264 . Additionally, the downstream fin  260  comprises a first longitudinal side  266  physically coupled to a surface of the venturi outlet  230 . A second longitudinal side  268  opposite the first longitudinal side may come into contact with a fuel injection mixture. 
     A width  261  of the downstream fin  260  may be proportional to the diameter of the venturi outlet  230 . That is to say, the width  261  may decrease as the diameter of the venturi outlet  230  decreases toward the venturi throat  240 . Said another way, the width  261  of the downstream fin  260  increases in the general direction of fuel flow  292 . In some examples, the width  261  is substantially equal to the width  251 . 
     A difference between the upstream fin  250  and the downstream fin  260  may include their orientations. The downstream fin  260  may be arranged at an angle relative to the upstream fin  250 . Said another way, the upstream fin  250  and the downstream fin  260  may be arranged at different radial positions such that leading edges and trailing edges of the fins do not align about the y-axis. In some examples, the angle may be between 1 to 90 degrees. In some examples, additionally or alternatively, the angle may be between 10 to 70 degrees. In some examples, additionally or alternatively, the angle may be between 30 to 60 degrees. In one example, the angle is exactly 45 degrees. In this way, the leading edge  262  of the downstream fin  260  may be offset by an angle of 45° relative to the leading edge  252  of the upstream fin  250 . Similarly, the trailing edge  264  of the downstream fin  260  may be offset by an angle of 45° relative to the trailing edge  254  of the upstream fin  250 . 
     Each of the upstream fin  250  and the downstream fin  260  may be oriented to direct a fuel mixture to swirl in a common direction. In the example of the  FIG. 2 , the upstream fin  250  and the downstream fin  260  are oriented to direct a fuel mixture to swirl in a counterclockwise direction. However, it will be appreciated by those of ordinary skill in the art that each of the upstream fin  250  and downstream fin  260  may be arranged to swirl the fuel mixture in a clockwise direction. In some examples, additionally or alternatively, the upstream fin  250  and the downstream fin  260  may be oriented to direct the fuel mixture to swirl in opposite directions. Thus, the upstream fin  250  may be oriented to direct the fuel mixture in a counterclockwise direction and the downstream fin  260  may be oriented to direct the fuel mixture in a clockwise direction or vice-versa. 
     The venturi throat  240  may be arranged between the trailing edge  254  of the upstream fin  250  and the leading edge  262  of the downstream fin  260 . The venturi throat  240  may correspond to a smallest diameter of the body  212  of the fuel injector nozzle  210 . The venturi throat  240  may be free of features and/or openings which may affect a fuel air mixture flow. In some embodiments, as shown in  FIGS. 4 and 5 , the venturi throat  240  may be fitted with one or more openings for flowing air from a combustion chamber thereto, such that air may at least partially mix with a fuel mixture before flowing to the venturi outlet  230 . 
     In some examples, a diameter at the dashed line  294  (e.g., beginning of venturi throat  240 ) may be slightly less than a diameter at a dashed line  296  (e.g., ending of venturi throat  240 ). By doing this, mixing may improve, as will be described in greater detail below. 
     Turning now to  FIG. 3A , it shows a top-down view  300  of the venturi inlet  220  with a fuel mixture, shown by arrows  302 , flowing therethrough. The venturi inlet  220  is shown comprising a plurality of upstream fins  350 , wherein each fin of the plurality of upstream fins  350  may be used similarly to the upstream fin  250 . As such, components previously introduced may be similarly numbered in subsequent figures. 
     A number of the plurality of upstream fins  350  may be greater than two. In the example of  FIG. 3A , the number of the plurality of upstream fins  350  is equal to four, however, it will be appreciated that the number may be equal to three, five, six, or more. Additionally, the plurality of upstream fins  350  may be arranged according to the number of fins arranged in the venturi inlet  220 . For example, if eight fins are included in the venturi inlet  220 , then the fins may comprise a twist of 45°, such that the leading and trailing edges are angled 45° to one another. 
     The leading edge  252  comprises a width greater than a width of a trailing edge  254  of the upstream fin  250 . The width of the upstream fin  250  may decrease in the downstream direction to prevent constriction of the fuel injector nozzle and to prevent a collision between each of the upstream fins  350 . First longitudinal side  256  may be curved as illustrated to provide the 90° twist to the upstream fin  250 . The first longitudinal side  256  is physically coupled to the surface of the venturi inlet  220  and curves as it traverses down the venturi inlet  220  in a direction generally parallel to the general direction of fuel flow. 
     As the arrows  302  indicate, a fuel mixture may contact at least one of the upstream fins  350  adjacent the leading edge  252 , wherein the fuel mixture may follow a curvature of the at least one upstream fin toward the venturi throat (e.g., venturi throat  240 ). The fuel mixture  302  may be directed to flow in a counterclockwise direction when contacting the upstream fins  350 . In some examples, a fuel mixture may not contact the upstream fins  350 . This may occur if the fuel mixture flows proximally to the central axis of the fuel injector nozzle, between the upstream fins  350 . However, due to the swirl imparted onto the fuel mixture by the fins  350 , it may be unlikely that a portion of the fuel mixture maintains a flow path substantially along the central axis without contacting the upstream fins  350  or downstream fin  260  of a plurality of downstream fins  360  shown in  FIG. 3B . 
     Turning now to  FIG. 3B , it shows a top-down view  301  of the venturi outlet  230  with a fuel mixture, shown by arrows  304 , flowing therethrough. The venturi outlet  230  is shown comprising a plurality of downstream fins  360 , wherein each fin of the plurality of downstream fins  360  may be used similarly to the downstream fin  260 . 
     The leading edge  262  of the downstream fin  260  may comprise a width less than a width of the trailing edge  264 . In one example, the leading edge  262  of the downstream fin  260  and the trailing edge  354  of the upstream fin  250  are substantially equal to each other. The width of the downstream fin  260  may increase in the downstream direction to increase an amount of fuel mixture it may contact without overly constricting a cross-section of the venturi outlet  230 . The first longitudinal side  266  may be curved to provide the twist of the downstream fin  260  such that the leading edge  262  and the trailing edge  264  are 90° relative to one another. 
     As the arrows  304  indicate, the fuel mixture may contact at least one of the downstream fins  360  adjacent the leading edge  262 , wherein the fuel mixture may follow a curvature of the at least one downstream fin toward an extreme end of the venturi outlet  230  where the fuel mixture may exit the venturi nozzle. 
     The top-down views  300  and  301  of  FIGS. 3A and 3B  are taken from a shared perspective down the central axis of the fuel injector nozzle to illustrate misalignment of the upstream fins  350  and the downstream fins  360 . As shown, the downstream fin  360  may be angularly offset to the upstream fins  350 , which may allow a greater amount of swirl to be imparted onto the fuel mixture. In one example, the angle is 45°, where the angle is measured between corresponding portions of the upstream and downstream fins. For example, the leading edge  252  of the upstream fin  250  is 45° offset to the leading edge  262  of the downstream fin  260 . A halfway point of the upstream fin  250  is 45° offset to a halfway point of the downstream fin  260 . The trailing edge  254  of the upstream fin  250  is 45° offset to the trailing edge  264  of the downstream fin  260 . By doing this, a fuel mixture turbulence before entering a combustion chamber may be increased, which may decrease and/or prevent soot forming. 
     Turning now to  FIG. 4 , it shows an embodiment  400  of the fuel injector nozzle  210  comprising the venturi inlet  220  having the upstream fin  250 , the venturi outlet  230  comprising the downstream fin  260 , and the venturi throat  240  between the venturi inlet  220  and outlet  230 . More specifically, boundaries of the venturi throat  240  are marked by dashed lines  402  and  404 . Dashed line  402  indicates an upstream extreme end of the venturi throat  240  adjacent the venturi inlet  220 . A fuel mixture may enter the venturi throat  240  at the upstream extreme end. Dashed line  404  indicates a downstream extreme end of the venturi throat  240  adjacent the venturi outlet  230 . A fuel mixture may exit the venturi throat  240  at the downstream extreme  404  end and flow to the venturi outlet  230 . 
     The embodiment  400  further comprises an air entrainment system  410  comprising an air entrainment passage  412  comprising an inlet  414  and an outlet  416 . The air entrainment passage  412  may extend from the opening  232  of the venturi outlet  230  to the venturi inlet  240 . As such, the air entrainment passage  412  may be coupled between the venturi inlet  220  and the venturi outlet  230 . The air entrainment passage  412  may be arranged completely outside of the fuel injector nozzle  210  such that a fuel mixture does not come into contact with surface of the air entrainment passage  412 . 
     As shown, the air entrainment system  410  comprises a plurality of the air entrainment passage  412  arranged around the fuel injector nozzle  210 . In the example of  FIG. 4 , there are exactly two air entrainment passages. However, it will be appreciated that other numbers of the air entrainment passage  412  may be present, including only one or three or more without departing from the scope of the present disclosure. 
     Combustion chamber gases adjacent to the opening  232  of the venturi outlet  230  may enter the air entrainment passage  412  via the inlet  414 . This may occur due to low static pressure at the venturi throat  440  due to a fuel mixture flowing therethrough being accelerated due to the venturi shape of the fuel injector nozzle  210 . As such, combustion chamber gases may be promoted to flow through the air entrainment passage  412 , out the outlet  416 , and to the venturi throat  440  due to the venturi shape of the fuel injector nozzle  210 . The combustion chamber gases (dashed arrows  494 ) may mix with a fuel mixture (arrows  492 ) in the venturi throat  440  and/or the venturi outlet  230 . Due to the turbulence imparted by the upstream  250  and downstream  260  fins, mixing between the combustion chamber gases and the fuel mixture may increase relative to other injector nozzles in the art. 
     In some examples, the air entrainment system  410  may be additionally used as a fuel injection heating system. Gases from the combustion chamber may enter the air entrainment passage  412 , wherein heat from the gases may transfer to fuel in the fuel injector nozzle  210 . The heat may transfer while the gases are in the air entrainment passage  412  before the gases enter the fuel injector nozzle  210 . In this way, the air entrainment system  410  may comprise two functions, heat the injection and to increase gas/injection mixing. 
     Turning now to  FIG. 5 , it shows an embodiment  500  of the fuel injector nozzle  210  comprising the venturi inlet  220  having the upstream fin  250 , the venturi outlet  230  comprising the downstream fin  260 , and the venturi throat  240  between the venturi inlet  220  and outlet  230 . More specifically, boundaries of the venturi throat  240  are marked by dashed lines  502  and  504 . Dashed line  502  indicates an upstream extreme end of the venturi throat  240  adjacent the venturi inlet  220 . A fuel mixture may enter the venturi throat  240  at the upstream extreme end. Dashed line  504  indicates a downstream extreme end of the venturi throat  240  adjacent the venturi outlet  230 . A fuel mixture may exit the venturi throat  240  at the downstream extreme end and flow to the venturi outlet  230 . 
     The embodiment  500  further comprises an air entrainment system  510 , wherein the air entrainment system comprises at least one air entrainment passage  512 , an inlet  514 , a chamber  516 , and an annular outlet  518 . The air entrainment passage  512  and the inlet  514  may be substantially similar to the air entrainment passage  412  and inlet  414  of  FIG. 4 . However, the air entrainment passage  512  may direction the combustion chamber gases (dashed arrows  594 ) to the chamber  516 . The chamber  516  may extend around an entire circumference of the venturi throat  240 . In this way, the chamber  516  may be an annular chamber. The chamber  516  may be hollow and may allow combustion chamber gases to flow therethrough before flowing out one or more outlets  518  and entering the venturi throat  240 . 
     In some examples, the chamber  516  may be completely open to the venturi throat  240  such that combustion chamber gases may flow into the venturi throat  240  at any portion of its circumference via a single, continuous opening. Additionally or alternatively, the chamber  516  may comprise a plurality of openings fluidly coupling it to the venturi throat  240 . The plurality of openings may be evenly spaced along the circumference of the venturi throat  240 . In one example, the plurality of openings may include two openings separated by 180°. At any rate, the plurality of openings and/or the single, continuous opening may be shaped to flow combustion chamber gases into the venturi throat  240  in a radially inward direction perpendicular to the central axis  299 . 
     The chamber  516  may comprise a trapezoidal cross-section. This may allow a diameter of the fuel injector nozzle at the dashed line  502  to be slightly smaller than a diameter of the fuel injector nozzle at the dashed line  504 . Said another way, a portion of the venturi throat  240  directly upstream of the chamber  516  may comprise an upstream diameter smaller than a downstream diameter of a portion of the venturi throat  240  directly downstream of the chamber  516 . In some examples, upstream diameter may be between 1 and 20% smaller than the downstream diameter. Additionally or alternatively, the upstream diameter may be between 5 and 15% smaller. In one example, the upstream diameter may be exactly 10% smaller than the downstream diameter. By doing this, combustion chamber gases mixing with the fuel mixture may increase. 
     Turning now to  FIG. 6A , it shows a cross-sectional view an embodiment  600  of a fuel injector tip  610  comprising a plurality of nozzle holes  612 . In one example, a nozzle hole of the plurality of nozzle holes  612  may be similar to the fuel injector nozzle  210  of  FIGS. 2, 4, and 5 . Additionally or alternatively, the nozzle hole of the plurality of nozzle holes  612  may be different than the fuel injector nozzle  210 . 
     The plurality of nozzle holes  612  may include a central nozzle  620 , a plurality of inner ring nozzles  630 , a plurality of middle ring nozzles  640 , and a plurality of outer ring nozzles  650 . The central nozzle  620  may be arranged along a central axis  699  of the fuel injector tip. In some examples, the central axis  699  of the fuel injector tip  610  may align with a central axis of a fuel injector. In this way, the central nozzle  620  may be positioned to inject directly along an axis along which a piston oscillates. 
     The plurality of inner ring nozzles  630  may be arranged along a ring spaced about the central axis  699 . A first diameter  632  of the ring of the plurality of inner ring nozzles  630  may be based on a second diameter  642  of the ring of the plurality of middle ring nozzles  640  and/or on a third diameter  652  of the ring of the outer ring nozzles  650 . The third diameter  652  may be a greatest diameter, wherein the second diameter  642  is less than the third diameter  652  and where the first diameter  632  is less than the second diameter. In some examples, the second diameter  642  may be equal to between 50 to 90% of the third diameter  652 . In some examples, additionally or alternatively, the second diameter  642  may be equal to 60 to 90% of the third diameter  652 . In some examples, additionally or alternatively, the second diameter  642  may be equal to 70 to 90% of the third diameter  652 . In some examples, additionally or alternatively, the second diameter  642  may be equal to 75 to 85% of the third diameter  652 . In one example, the second diameter  642  is equal to 80% of the third diameter  652 . 
     In some examples, the first diameter  632  may be equal to between 10 and 40% of the third diameter  652 . In some examples, additionally or alternatively, the first diameter  632  may be equal to between 10 and 30% of the third diameter  652 . In some examples, additionally or alternatively, the first diameter  632  may be equal to between 15 and 25% of the third diameter  652 . In one example, the first diameter  632  is equal to 20% of the third diameter  652 . In one exemplary embodiment, the third diameter  652  is 5 mm, the second diameter  642  is 4 mm, and the first diameter  632  is 2 mm. However, it will be appreciated that other dimensions may be used without departing from the scope of the present disclosure. 
     Nozzles of the inner  630 , middle  640 , and outer  650  ring nozzles may be angled differently relative to the central axis  699 . The nozzles may be angled due to a curvature of the injector tip  610 . For example, the injector tip  610  may be undulating and/or sinusoidal. By curving the injector tip  610 , its package size may decrease and an orientation of the nozzles may be optimized to decrease penetration and decrease impingement. 
     A first angle  634  measured from an inner nozzle injection axis  636  to the central axis  699  may be between 10 and 50 degrees. In some examples, additionally or alternatively, the first angle  634  may be between 20 and 40 degrees. In some examples, additionally or alternatively, the first angle  634  may be between 25 and 35 degrees. In some examples, additionally or alternatively, the first angle  634  may be between 27 and 33 degrees. In one example, the first angle  634  is equal to 30 degrees. 
     A second angle  644  measured from a middle nozzle injection axis  646  to the central axis  699  may be between 0 and 30 degrees. In some examples, additionally or alternatively, the second angle  644  may be between 5 and 25 degrees. In some examples, additionally or alternatively, the second angle  644  may be between 5 and 20 degrees. In some examples, additionally or alternatively, the second angle  644  may be between 5 and 15 degrees. In some examples, additionally or alternatively, the second angle  644  may be between 5 and 10 degrees. In one example, the second angle  644  is equal to 5 degrees. 
     A third angle  654  measured from an outer nozzle injection axis  656  to the central axis  699  may be between 30 and 70 degrees. In some examples, additionally or alternatively, the third angle  654  may be between 35 and 65 degrees. In some examples, additionally or alternatively, the third angle  654  may be between 40 and 60 degrees. In some examples, additionally or alternatively, the third angle  654  may be between 45 and 55 degrees. In some examples, additionally or alternatively, the third angle  654  may be between 47 and 53 degrees. In one example, the third angle  654  is equal to 50 degrees. 
     As shown, the injector tip  610  may be symmetric about the central axis  699 . In one example, the injector tip  610  is rotationally symmetric about the central axis  699 . Additionally or alternatively, the injector tip  610  may also comprise reflectional symmetry about the central axis  699 . 
     Turning now to  FIG. 6B , it shows a view  602  of the injector tip  610  from within a combustion chamber. The view  602  further illustrates an arrangement of the inner  630 , middle  640 , and outer  650  ring nozzles. In the example of  FIG. 6B , each of the inner  630 , middle  640 , and outer  650  ring nozzles may be radially aligned. In this way, the inner  630 , middle  640 , and outer  650  ring nozzles may be arranged such that they are concentric with one another relative to an injection axis of the central nozzle  620  (e.g., central axis  699  of  FIG. 6A ). In some examples, one or more of the inner  630 , middle  640 , and outer  650  ring nozzles may be radially misaligned with other nozzles without departing from the scope of the present disclosure. 
     The inner ring nozzles  630  may be arranged around a uniform circle sized according to the first diameter  632 . The inner ring nozzles  630  may be evenly spaced about the uniform circle. Additionally or alternatively, one or more of the nozzles of the inner ring nozzles  630  may be unevenly spaced such that the distribution of the inner ring nozzles  630  is asymmetric. A number of inner ring nozzles  630  may be greater than two. Additionally or alternatively, the number of inner ring nozzles  630  may be greater than 6. Additionally or alternatively, the number of inner ring nozzles  630  may be greater than 8. Additionally or alternatively, the number of inner ring nozzles  630  may be greater than 10. In one example, the number of inner ring nozzles  630  is equal to 10. 
     The middle ring nozzles  640  may be arranged around a uniform circle sized according to the second diameter  642 . The middle ring nozzles  640  may be evenly spaced about the uniform circle. Additionally or alternatively, one or more of the nozzles of the middle ring nozzles  640  may be unevenly spaced such that the distribution of the middle ring nozzles  640  is asymmetric. A number of middle ring nozzles  640  may be equal to a number of inner ring nozzles  630 . Additionally or alternatively, the number of middle ring nozzles  640  may be less than or greater than the number of inner ring nozzles  630  without departing from the scope of the present disclosure. 
     The outer ring nozzles  650  may be arranged around a uniform circle sized according to the third diameter  652 . The outer ring nozzles  650  may be evenly spaced about the uniform circle. Additionally or alternatively, one or more of the nozzles of the outer ring nozzles  650  may be unevenly spaced such that the distribution of the outer ring nozzles  650  may be asymmetric. A number of outer ring nozzles may be equal to a number of inner  630  and/or middle  640  ring nozzles. Additionally or alternatively, the number of outer ring nozzles  650  may be greater than the number of inner  630  and/or middle  640  ring nozzles. In one example, the number of outer ring nozzles  650  is exactly two times greater than the number of inner  630  and/or middle  640  ring nozzles. In one example of the injector tip  610 , the number of inner ring nozzles  630  is equal to 10, the number of middle ring nozzles  640  is equal to 10, and the number of outer ring nozzles is equal to 20, wherein a first half of the outer ring nozzles  650  are radially aligned with the inner  630  and middle  640  ring nozzles, and a second half are evenly distributed between the first half. 
     A sizing of each nozzle of the inner  630 , middle  640 , and outer  650  ring nozzles and central nozzle  620  may be proportional relative to one another. For example, the inner ring nozzles  630  may be equally sized according to a first size, the central ring nozzle may be greater than or equal to the first size, the middle ring nozzles  640  may be equally sized to one another and may be greater than or equal to the first size, and the outer ring nozzles  650  may be equally sized to one another and may be greater than or equal to the first size. In some examples, the first size of the inner ring nozzles  630  may be between 0.01 to 0.05 mm. Additionally or alternatively, the first size of the inner ring nozzles  630  may be between 0.02 and 0.04 mm. In one example, the first size of the inner ring nozzles  630  is between 0.03 to 0.04 mm. 
     In some examples, the size of central nozzle  620  may be between 0.01 to 0.05 mm. Additionally or alternatively, the size of central nozzle  620  may be between 0.02 and 0.04 mm. In one example, the size of central nozzle  620  is 0.04 mm. 
     In some examples, the size of the middle ring nozzles  640  may be between 0.01 to 0.08 mm. Additionally or alternatively, the size of the middle ring nozzles  640  may be between 0.02 and 0.07 mm. Additionally or alternatively, the size of the middle ring nozzles  640  may be between 0.03 and 0.06 mm. Additionally or alternatively, the size of the middle ring nozzles  640  may be between 0.04 and 0.06 mm. In one example, the size of the middle ring nozzles  640  is between 0.05 to 0.06 mm. 
     In some examples, the size of the outer ring nozzles  650  may be between 0.01 to 0.07 mm. Additionally or alternatively, the size of the outer ring nozzles  650  may be between 0.02 and 0.07 mm. Additionally or alternatively, the size of the outer ring nozzles  650  may be between 0.03 and 0.06 mm. Additionally or alternatively, the size of the outer ring nozzles  650  may be between 0.04 and 0.06 mm. In one example, the size of the outer ring nozzles  650  is between 0.04 to 0.05 mm. 
     As such, the injector tip may be curved to angle its inner, middle, and outer ring nozzles relative to a single, central nozzle to decrease an amount of penetration of the fuel injection. Additionally, the shape of the injector tip  610  may increase its surface area, thereby decreasing injector packaging constraints. Furthermore, the sizing of the nozzles may be to decrease spray interactions and to decrease impingement of the fuel spray onto surfaces of the combustion chamber and/or piston. 
     In this way, a fuel injector nozzle may comprise one or more features to increase turbulence and mixing between a fuel injection mixture and combustion chamber gases. The fuel injector nozzle may comprise a venturi shaped with an upstream twisted fin arranged in a venturi inlet and a downstream twisted fin arranged in a venturi outlet. The upstream and downstream fins may impart a swirl onto the fuel mixture. The fuel injector nozzle may further comprise an air entrainment passage and/or chamber which may direct combustion chamber gases to a venturi throat of the venturi shaped nozzle hole. The combustion chamber gases may flow in a radially inward direction, which may further disrupt a flow direction of the fuel mixture, thereby increasing mixing and turbulence. The fuel injector nozzle may be one nozzle of a plurality of nozzles arranged along a curved injector tip. The technical effect of curving an injector tip is to decrease its packaging size, decrease interactions between sprays from separate nozzles, and to decrease impingement. 
     An embodiment of a system comprising an engine comprising an injector having a venturi-shaped nozzle, wherein the injector comprises a plurality of upstream twisted fins arranged in a venturi inlet, and where a leading edge of an upstream twisted fin of the plurality of upstream twisted fins is perpendicular to a trailing edge of the twisted fin. A first example of the system, further includes where the injector further comprises a plurality of downstream twisted fins arranged in a venturi outlet, and where the plurality of downstream twisted fins is identical to the plurality of upstream twisted fins in shape. A second example of the system, optionally including the first example, further includes where a leading edge of a downstream twisted fin of the plurality of downstream twisted fins is oriented at an angle relative to the leading edge of the upstream twisted fin of the upstream twisted fins. A third example of the system optionally including the first and/or second examples, further includes where the angle is equal to 45°. A fourth example of the system, optionally including one or more of the first through third examples, further includes where a width of each of the plurality of downstream twisted fins is equal to 40% of a diameter of the venturi outlet, and where the diameter of the venturi outlet increases in a downstream direction. A fifth example of the system, optionally including one or more of the first through fourth examples, further includes where a venturi throat is arranged between the venturi inlet and a venturi outlet, and where the upstream twisted fins do not extend into the venturi throat. A sixth example of the system, optionally including one or more of the first through fifth examples, further includes where a diameter of the venturi inlet decreases in a downstream direction, and where a width of each of the plurality of upstream twisted fins decreases in the downstream direction, and where the width is equal to 40% of the diameter of the venturi outlet. A seventh example of the system, optionally including one or more of the first through sixth examples, further includes where the plurality of upstream twisted fins is oriented to impart a counterclockwise or clockwise swirl onto a fuel mixture flow. An eighth example of the system, optionally including one or more of the first through seventh examples, further includes where the venturi-shaped nozzle is a single nozzle of a plurality of venturi-shaped nozzles evenly distributed along a surface of a tip of the injector, and where the surface is curved. 
     An embodiment of an injector comprising at least one injection nozzle comprising venturi throat arranged between a venturi inlet and a venturi outlet, and where the venturi inlet comprises at least one upstream twisted fin and the venturi outlet comprises at least one downstream twisted fin spaced away from the upstream twisted fin and an air entrainment system fluidly coupled to an extreme end of the venturi outlet and the venturi throat, and where the air entrainment system is arranged completely outside of the at least one injection nozzle. A first example of the injector further includes where the air entrainment system comprises two or more air entrainment passages directly fluidly coupled to the venturi throat. A second example of the injector, optionally including the first example, further includes where the air entrainment system comprises two or more air entrainment passages directly fluidly coupled to a chamber, where the chamber extends around an entire circumference of the venturi throat. A third example of the injector, optionally including the first and/or second examples, further includes where the chamber comprises two openings arranged 180° across from one another, the two openings fluidly coupling the chamber to the venturi throat. A fourth example of the injector, optionally including one or more of the first through third examples, further includes where the chamber comprises a trapezoidal cross-section, and where an upper diameter of the venturi outlet is larger than a lower diameter of the venturi inlet. A fifth example of the injector, optionally including one or more of the first through fourth examples, further includes where the at least one upstream twisted fin is one of four total upstream twisted fins, and where the at least one downstream twisted fin is one of four total downstream twisted fins, and where the downstream twisted fins and upstream twisted fins are angled and radially offset with one another. 
     A fuel injector comprising a curved tip comprising a central nozzle arranged along a central axis, a plurality of inner ring nozzles arranged around the central axis via a first diameter, a plurality of middle ring nozzles arranged around the central axis via a second diameter, and a plurality of outer ring nozzles arranged around the central axis via a third diameter, and where each of the pluralities of inner, middles, and outer ring nozzles are angled relative to the central axis. A first example of the fuel injector further includes where the first diameter is less than the second diameter, and where the second diameter is less than the third diameter, and where the inner ring nozzles are sized uniformly and evenly distributed, and where the middle ring nozzles are sized uniformly and evenly distributed, and where the outer ring nozzles are sized uniformly and evenly distributed. A second example of the fuel injector, optionally including the first example, further includes where the plurality of inner ring nozzles is smaller than the central nozzle, and where the central nozzle is smaller than each of the plurality of outer ring nozzles, and where the plurality of outer ring nozzles is smaller than each of the plurality of middle ring nozzles. A third example of the fuel injector, optionally including the first and/or second examples, further includes where a number of inner ring nozzles is equal to 10, and where a number of middle ring nozzles is equal to 10, and where a number of outer ring nozzles is equal to 10, and where the plurality of inner ring nozzles, the plurality of middle ring nozzles, and a first half of the plurality of outer ring nozzles are radially aligned, and where a second half of the plurality of outer ring nozzles are radially misaligned with the plurality of inner ring nozzles and the plurality of middle ring nozzles. A fourth example of the fuel injector, optionally including one or more of the first through third examples, further includes where one or more of the central nozzle and the pluralities of the inner, middle, and outer rings nozzles comprises a venturi throat arranged between a venturi inlet and a venturi outlet, and where the venturi inlet comprises at least one upstream twisted fin, and where the venturi outlet comprises at least one downstream twisted fin, and where the downstream twisted fin is misaligned with the upstream twisted fin relative to a general direction of fuel mixture flow. 
     Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller. 
     It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
     As used herein, the term “approximately” is construed to mean plus or minus five percent of the range unless otherwise specified. 
     The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.