JP4124027B2 - In-cylinder direct injection CNG engine fuel injection control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention directly injects a compressed natural gas (CNG) into a cylinder and switches between stratified combustion and homogeneous combustion in accordance with the operating conditions of the engine, and a fuel injection control thereof. More specifically, the present invention relates to a fuel injection control method for an in-cylinder direct injection CNG engine that can achieve both homogeneous combustion and stratified combustion.
[0002]
[Prior art]
In recent years, from the viewpoints of energy and environmental measures, compressed natural gas (CNG) has been used as a fuel for automobile internal combustion engines, and CNG fuel has been injected into the cylinder to improve fuel efficiency and output. In-cylinder direct injection CNG engines (hereinafter referred to as CNG engines as appropriate) having a lean burn operation region are being actively developed, and various techniques have been proposed. For example, an in-cylinder direct injection CNG engine having one injector in a combustion chamber is disclosed (see Patent Document 1).
[0003]
FIG. 5 is a cross-sectional view showing a schematic configuration of a conventional in-cylinder direct injection CNG engine provided with such one injector, and schematically shows the state of air-fuel mixture in the combustion chamber. As shown in FIG. 5, the combustion chamber 10 a of the CNG engine 10 includes a cylinder bore 11, a cylinder head 13, and a piston 12 that is disposed in the cylinder bore 11 so as to be reciprocally movable. A concave cavity 12a is formed in the intake side portion of the top surface of the piston 12 in order to establish stratified combustion.
[0004]
A spark plug 14 is disposed substantially at the center of the combustion chamber 10a. An intake valve 16 is disposed at the intake port 15 facing the combustion chamber 10a, and an exhaust valve 20 is disposed at the exhaust port 18 facing the combustion chamber 10a. An injector 30 that directly injects CNG fuel into the combustion chamber 10a is disposed near the intake valve 16 in the combustion chamber 10a.
[0005]
The injector 30 has a spray shape and a spray angle so that fuel spray is injected into the cavity 12a. The fuel spray injected from the injector 30 enters the cavity 12a, collides with the bottom wall of the cavity 12a, and then flows in the direction of the spark plug 14 along the bottom wall to form an air-fuel mixture.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-328997
[Problems to be solved by the invention]
However, it is difficult for the injector 30 for injecting gaseous CNG fuel to ensure an injection rate equivalent to that of liquid fuel in terms of calorific value, and the injection period is longer than that in the case of liquid fuel. In particular, in the homogeneous combustion region where the fuel injection amount is large (in the vicinity of WOT at the time of maximum load), since it is a gaseous fuel, a great amount of injection time is required.
[0008]
Therefore, as shown in FIG. 5, the fuel spray injected in the second half of the injection period remains in the vicinity of the cavity 12a and becomes a rich layer 27. On the other hand, the fuel spray injected in the first half of the injection period becomes an over-diffusion layer 28, and a homogeneous layer 29 is formed between these layers 27, 28, resulting in an inhomogeneous mixture as a whole and the combustion surface. In addition, there is a problem that the performance is inferior.
[0010]
This invention aims to provide a fuel injection control method for a cylinder direct injection CNG engine that can achieve both homogeneous combustion and stratified charge combustion.
[0011]
[Means for Solving the Problems]
Injection in order to achieve the above object, a fuel injection control method for a cylinder direct injection CNG engine according to the first invention, a spark plug disposed substantially at the center of the combustion chamber, the CNG fuel into the combustion chamber Stratified combustion injectors and homogeneous combustion injectors, and a stratified combustion cavity formed in a concave shape on the top surface of the piston, and the stratified combustion injector is configured to inject CNG fuel into the cavity. its spray shape and the spray angle is set, the homogeneous combustion injector, the disposed in the combustion chamber the fuel spray injected from the homogeneous combustion injector is set so as not enter directly into the cavity, the engine A fuel injection control method for an in-cylinder direct injection CNG engine that switches between stratified combustion and homogeneous combustion in accordance with the operating conditions of Normal stratified charge combustion control is performed using only the stratified charge injector, and during homogeneous combustion, if the current injection quantity is less than or equal to the predetermined injection quantity, normal homogeneous combustion control is performed using only the homogeneous combustion injector. If the current injection amount exceeds the predetermined injection amount, the injection is performed with a substantially maximum injection time that can ensure a sufficient time until the compression stroke and the injection end by the homogeneous combustion injector, and the insufficient injection amount is calculated. Then, the insufficient injection amount is injected at an early stage of the compression stroke by the stratified combustion injector .
Further, a fuel injection control method for a direct injection CNG engine according to a second aspect of the present invention includes a spark plug disposed substantially at the center of a combustion chamber, a stratified combustion injector for injecting CNG fuel into the combustion chamber, and a homogeneous A stratified combustion cavity formed in a concave shape on the piston top surface, and the stratified combustion injector has a spray shape and a spray angle such that CNG fuel is injected into the cavity. The homogeneous combustion injector is disposed in the combustion chamber so that the fuel spray injected from the homogeneous combustion injector does not directly enter the cavity, and the stratified combustion injector and the homogeneous injector Both combustion injectors ensure a minimum injection quantity, and switch between stratified combustion and homogeneous combustion according to engine operating conditions. In-cylinder direct injection CNG engine fuel injection control method for determining whether or not the stratified combustion injector and the homogeneous combustion injector have failed, and if any one of the injectors has failed, The fuel injection control is performed only with the non-injected injector, and when both of the injectors are not malfunctioning, it is determined whether or not the stratified combustion region, and if it is the stratified combustion region, only the stratified combustion injector Stratified combustion injection control is performed, and if the region is in a homogeneous combustion region, it is further determined whether or not the current injection amount is less than or equal to a predetermined injection amount, and if it is less than or equal to the predetermined injection amount, the homogeneous combustion The homogeneous combustion injection control is performed only by the injector, and when the predetermined injection amount is exceeded, the homogeneous combustion injection control is performed by both the injectors. It is characterized in that to perform.
[0012]
The control operation of the present invention is as follows. That is, when the operation region is the stratified combustion region, fuel is injected only by the stratified combustion injector, and normal stratified combustion control is performed. In the homogeneous combustion region, it is determined whether or not the current fuel injection amount is equal to or less than a predetermined injection amount. The predetermined injection amount is an injection amount that allows the compression stroke injection independently from the injection rate of the homogeneous combustion injector, and is obtained experimentally in advance.
[0013]
When the current fuel injection amount is less than or equal to the predetermined injection amount, optimal fuel injection and optimal ignition are performed using only the homogeneous combustion injector. The fuel injection by the homogeneous combustion injector is completed within the compression stroke, and sufficient time from the completion of injection to ignition can be ensured to improve the homogeneity of the air-fuel mixture.
[0014]
Further, since the fuel spray injected from the homogeneous combustion injector does not directly enter the cavity, it is not affected by the cavity, and there is no concentration of rich air-fuel mixture near the spark plug. Therefore, the period from the end of injection to ignition can be made shorter than in the case of single injection of the stratified charge injector, and the homogeneity is improved.
[0015]
On the other hand, when the current fuel injection amount exceeds the predetermined injection amount, optimal fuel injection is performed by both the stratified combustion injector and the homogeneous combustion injector, and optimal ignition is performed. In the period in which both injectors inject fuel at the same time, simultaneous injection of CNG fuel, which is a gaseous fuel, has a higher injection speed than liquid fuel such as gasoline, so it can cause large turbulence due to the jet flow in the combustion chamber, Furthermore, the homogeneity can be improved.
[0016]
In this way, the optimal injection control by the stratified combustion injector and the homogeneous combustion injector can form a homogeneous air-fuel mixture in the combustion chamber, and it is possible to obtain good homogeneous combustion by optimally igniting this. it can.
[0017]
Each control described above is executed until the engine is stopped (ignition switch is turned off).
[0018]
Therefore, according to the 1st and 2nd invention, homogeneous combustion and stratified combustion can be made compatible by the optimal injection control by the both injectors according to the operating condition of the engine.
Further, according to the first aspect of the present invention, it is possible to make up for the dynamic range shortage of the homogeneous combustion injector at the time of homogeneous combustion, and to perform fuel injection so as not to prevent air inflow. Moreover, the early injection of the compression stroke can also suppress the deterioration of the homogeneity of the air-fuel mixture due to the bad influence of the cavity (rich air-fuel mixture concentration near the spark plug).
Further, according to the second aspect of the invention, it is possible to prevent the injection amount from becoming excessive at the time of the minimum fuel injection required at the time of idling or the like, and to realize optimal fuel injection.
Further, according to the second invention, when any one of the injectors fails, the minimum operation as the engine system can be ensured by injecting fuel with the other injector that does not fail. At the same time, when both injectors are not out of order, optimal injection control can be performed by properly using the injectors according to the operating conditions of the engine, and both homogeneous combustion and stratified combustion can be achieved.
[0019]
An in-cylinder direct injection CNG engine according to a third aspect of the present invention is the in-cylinder direct injection CNG engine according to the first or second aspect of the present invention, wherein the stratified combustion injector and the cavity are arranged on the intake side in the combustion chamber. On the other hand, the homogeneous combustion injector is arranged on the exhaust side or the center side in the combustion chamber.
[0020]
Therefore, according to the present invention, the combination of the arrangements of the two injectors can be arbitrarily selected according to the combustion performance and output required of the engine, and the degree of freedom in design can be increased.
[0021]
Further, the in-cylinder direct injection CNG engine according to the fourth invention is the in-cylinder direct injection CNG engine according to any one of the first to third inventions, wherein the stratified combustion injector is stratified combustion alone. While the injection rate is set as possible, the homogeneous combustion injector has its spray angle and injection hole orientation set so that its fuel spray does not enter the cavity directly regardless of the position of the piston, Further, both the injectors are characterized in that the injection rate is set so that the fuel can be injected within the compression stroke even at the maximum injection and maximum rotation.
[0022]
Therefore, according to the present invention, the stratified combustion injector alone can cope with stratified combustion, while the homogeneous combustion injector can perform stable fuel injection without being affected by the position of the piston. Even during rotation, reliable fuel injection can be performed in the compression stroke.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a fuel injection control method for an in-cylinder direct injection CNG engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
[0030]
FIG. 1 is a cross-sectional view showing a schematic configuration of a CNG engine according to an embodiment of the present invention, schematically showing a state in which fuel is injected by both a stratified combustion injector and a homogeneous combustion injector. is there. In the following description, members that are the same as or correspond to those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.
[0031]
As shown in FIG. 1, the CNG engine 10 is a direct injection type in which CNG fuel is directly injected into a combustion chamber 10a by a stratified combustion injector 23 and a homogeneous combustion injector 25, which will be described later, and a configuration of a normal direct injection type gasoline engine. And is configured to be able to switch between stratified combustion and homogeneous combustion in accordance with engine operating conditions.
[0032]
Further, a stratified combustion injector 23 for directly injecting CNG fuel into the combustion chamber 10a is disposed near the intake valve 16 of the combustion chamber 10a. A homogeneous combustion injector 25 for directly injecting CNG fuel into the combustion chamber 10a is disposed in the vicinity of the exhaust valve 20 of the combustion chamber 10a.
[0033]
The spray shape and spray angle of the stratified combustion injector 23 are set so that the fuel spray 23a is injected into the cavity 12a. In addition, the injection rate is set so that the stratified combustion injector 23 can perform stratified combustion alone.
[0034]
In FIG. 1, the fuel spray 23a injected from the stratified combustion injector 23 enters the cavity 12a, collides with the bottom wall of the cavity 12a, and then flows in the direction of the spark plug 14 along the bottom wall. The process by which the air-fuel mixture 24 is formed is shown.
[0035]
The homogeneous combustion injector 25 is provided to improve the homogeneity of the air-fuel mixture during homogeneous combustion, so that the fuel spray 25a injected from the homogeneous combustion injector 25 does not directly enter the cavity 12a. Is set to
[0036]
Further, the homogeneous combustion injector 25 has a spray angle and an injection hole direction (with respect to a plane perpendicular to the axis of the cylinder bore 11) so that the fuel spray 25 a does not directly enter the cavity 12 a regardless of the position of the piston 12. An angle θ) is set.
[0037]
The stratified charge injector 23 and the homogeneous combustion injector 25 have injection rates set so that fuel can be injected within the compression stroke even at the maximum injection and maximum rotation. Further, the stratified combustion injector 23 and the homogeneous combustion injector 25 each have a minimum injection amount.
[0038]
As described above, both of the injectors 23 and 25 have a wide dynamic range, and even if one of the injectors 23 and 25 fails, the fuel is injected by the other injector that has not failed. Thus, the minimum operation as an engine system can be guaranteed.
[0039]
The CNG engine 10, spark plug 14, intake valve 16, exhaust valve 20, stratified combustion injector 23, homogeneous combustion injector 25, etc. are controlled by an electronic control unit (ECU) (not shown) based on various sensor information. It is controlled.
[0040]
Next, the fuel injection control method will be described with reference to FIG. FIG. 3 is a flowchart showing a fuel injection control method. For convenience of explanation, FIG. 1 showing the state in which fuel is injected from both the stratified combustion injector 23 and the homogeneous combustion injector 25 will be appropriately referred to.
[0041]
As shown in FIG. 3, first, when the CNG engine 10 is started (step S10), it is determined whether either the stratified combustion injector 23 or the homogeneous combustion injector 25 has failed (step S11). In this failure determination, for example, the in-cylinder pressure is monitored, and when the in-cylinder pressure that should be originally obtained cannot be obtained, it can be determined that there is a failure.
[0042]
If either the stratified combustion injector 23 or the homogeneous combustion injector 25 is out of order (Yes in step S11), only the non-failed injector is operated to perform the required fuel injection control (step S12). . In addition, a warning is given to the vehicle driver or the like by voice or display that either one of the injectors 23 or 25 has failed.
[0043]
If both the stratified combustion injector 23 and the homogeneous combustion injector 25 are normal (No at Step S11), it is determined whether or not the operation region is a stratified combustion region (Step S13). If it is the stratified charge combustion region (Yes at Step S13), fuel is injected only by the stratified charge injector 23 and normal stratified charge combustion control is performed (Step S14).
[0044]
On the other hand, when it is not the stratified combustion region, that is, when it is the homogeneous combustion region (No at Step S13), it is determined whether or not the current fuel injection amount is a predetermined value (predetermined injection amount) or less (Step S15). The predetermined value is an injection amount that allows the compression stroke injection independently from the injection rate of the homogeneous combustion injector 25, and is obtained experimentally in advance.
[0045]
If the current fuel injection amount is equal to or less than the predetermined value (Yes at Step S15), optimum fuel injection and optimum ignition are performed only by the homogeneous combustion injector 25 (Step S16). The fuel injection by the homogeneous combustion injector 25 is completed within the compression stroke, and sufficient time from the completion of injection to ignition can be ensured to improve the homogeneity of the air-fuel mixture.
[0046]
Further, the spray angle and the direction of the injection hole (angle θ) are set so that the fuel spray 25a injected from the homogeneous combustion injector 25 does not directly enter the cavity 12a (see FIG. 1). Since there is no influence, there is no concentration of the rich air-fuel mixture in the vicinity of the spark plug 14, the period from the end of injection to ignition can be made shorter than in the case of single injection of the stratified charge injector 23, and the homogeneity of the air-fuel mixture Will improve.
[0047]
In the case of liquid fuel such as gasoline, when the homogeneous combustion injector 25 is set in such a direction of the injection hole (angle θ), the fuel spray directly hits the cylinder bore 11 to cause oil dilution and the like so that the homogeneity of the air-fuel mixture is increased. Although not established, in the case of CNG fuel, since it is always a gas, problems such as oil dilution do not occur, and the homogeneity of the air-fuel mixture is established without any problem.
[0048]
On the other hand, if the current fuel injection amount exceeds the predetermined value (No at step S15), optimum fuel injection is performed by both the stratified combustion injector 23 and the homogeneous combustion injector 25 as shown in FIG. Is performed (step S17).
[0049]
The injectors 23 and 25 each have a wide dynamic range, the injection rate is set so that the fuel can be injected within the compression stroke even at the maximum injection and the maximum rotation, and the minimum injection amount. However, when such a wide dynamic range is not used but a narrow dynamic range is used, the following control is performed in step S17. Thus, the shortage of the dynamic range can be compensated.
[0050]
In other words, the homogeneous combustion injector 25 injects with a substantially maximum injection time that can ensure a sufficient compression stroke and a period until the end of the injection, calculates an insufficient injection amount, and compresses the insufficient injection amount by the stratified combustion injector 23. Inject early in the process. That is, in consideration of the closing timing of the intake valve 16, pulsation, and the like, the fuel injection is performed at a time when the air inflow is not hindered.
[0051]
As described above, by minimizing the fuel injection amount at the time of homogeneous combustion in the stratified combustion injector 23 and making the injection start the earliest, the adverse effect of the cavity 12a (the rich air-fuel mixture to the vicinity of the spark plug 14). The reduction in homogeneity of the air-fuel mixture due to concentration) can be suppressed.
[0052]
By the way, in the above control, as shown in FIG. 1, there is basically a period during which both injectors 23 and 25 simultaneously inject. The simultaneous injection of CNG fuel, which is a gaseous fuel, has a higher injection speed than liquid fuel such as gasoline. Therefore, a large turbulence can be caused by the jet flow in the combustion chamber 10a, and the homogeneity can be improved. .
[0053]
Therefore, by the optimum injection control by both the injectors 23 and 25 as described above, a homogeneous air-fuel mixture 26 can be formed in the combustion chamber 10a as shown in FIG. Good homogeneous combustion can be obtained. Here, FIG. 2 is a cross-sectional view showing the state of the homogeneous air-fuel mixture obtained in the combustion chamber 10a by the optimal injection control by the stratified combustion injector 23 and the homogeneous combustion injector 25.
[0054]
Each control described above is executed until the CNG engine 10 is stopped (ignition switch is turned off).
[0055]
As described above, according to the in-cylinder direct injection CNG engine 10 and the fuel injection control method thereof according to this embodiment, the stratified combustion injector 23 and the homogeneous combustion injector 25 are disposed in the combustion chamber 10a. By optimal injection control by the injectors 23 and 25, homogeneous combustion and stratified combustion can be made compatible.
[0056]
In the above embodiment, the homogeneous combustion injector 25 is described as being disposed in the vicinity of the exhaust valve 20 of the combustion chamber 10a. However, the present invention is not limited to this. For example, as shown in FIG. It may be arranged in the vicinity of the center spark plug 14. Also in this case, the direction of the injection hole and the spray angle are set so that the fuel spray 25a of the homogeneous combustion injector 25 does not enter the cavity 12a, and the same effect as in the above embodiment can be expected. . Here, FIG. 4 is a cross-sectional view showing an example in which the homogeneous combustion injector 25 is disposed substantially at the center of the combustion chamber 10a.
[0057]
【The invention's effect】
As described above, according to the fuel injection control method for the in-cylinder direct injection CNG engine according to the first and second inventions, the optimum fuel by the stratified combustion injector and the homogeneous combustion injector according to the operating state of the engine Homogeneous combustion and stratified combustion can be made compatible by injection control.
Further, according to the first aspect of the present invention, it is possible to make up for the dynamic range shortage of the homogeneous combustion injector at the time of homogeneous combustion, and to perform fuel injection so as not to prevent air inflow. Moreover, the early injection of the compression stroke can also suppress the deterioration of the homogeneity of the air-fuel mixture due to the bad influence of the cavity (rich air-fuel mixture concentration near the spark plug).
Further, according to the second aspect of the invention, it is possible to prevent the injection amount from becoming excessive at the time of the minimum fuel injection required at the time of idling or the like, and to realize optimal fuel injection.
Further, according to the second aspect of the present invention, when one of the stratified combustion injector or the homogeneous combustion injector fails, fuel injection is performed with the other non-failed injector as an engine system. When both injectors are not malfunctioning, optimal fuel injection control can be performed by properly using the injectors according to the operating conditions of the engine. Combustion can be achieved.
[0058]
Further, according to the in-cylinder direct injection CNG engine according to the third invention, the combination of the arrangement of the stratified combustion injector and the homogeneous combustion injector can be arbitrarily selected according to the combustion performance and output required for the engine. , Can increase the degree of design freedom.
[0059]
According to the in-cylinder direct injection CNG engine according to the fourth aspect of the invention, the stratified combustion injector alone can cope with stratified combustion, while the homogeneous combustion injector can stably inject fuel without being affected by the position of the piston. Furthermore, both of these injectors can perform the fuel injection reliably in the compression stroke even at the maximum injection and maximum rotation.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a CNG engine according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state of a homogeneous air-fuel mixture obtained in a combustion chamber by optimal injection control by a stratified combustion injector and a homogeneous combustion injector.
FIG. 3 is a flowchart showing a fuel injection control method.
FIG. 4 is a cross-sectional view showing an example in which a homogeneous combustion injector is disposed in the approximate center of a combustion chamber.
FIG. 5 is a cross-sectional view showing a schematic configuration of a conventional in-cylinder direct injection CNG engine.
[Explanation of symbols]
θ angle 10 CNG engine 10a Combustion chamber 11 Cylinder bore 12 Piston 12a Cavity 13 Cylinder head 14 Spark plug 15 Intake port 16 Intake valve 18 Exhaust port 20 Exhaust valve 23 Stratified combustion injector 23a Fuel spray 24 Mixture 25a Fuel spray 25 For homogeneous combustion Injector 26 Mixture

Claims (4)

A spark plug disposed approximately in the center of the combustion chamber;
A stratified combustion injector and a homogeneous combustion injector for injecting CNG fuel into the combustion chamber;
A cavity for stratified combustion formed in a concave shape on the top surface of the piston;
With
The stratified combustion injector has its spray shape and spray angle set so that CNG fuel is injected into the cavity,
The homogeneous combustion injector is disposed in the combustion chamber so that the fuel spray injected from the homogeneous combustion injector does not directly enter the cavity .
A fuel injection control method for an in-cylinder direct injection CNG engine that switches between stratified combustion and homogeneous combustion according to engine operating conditions,
At the time of stratified charge combustion, normal stratified charge combustion control is carried out only with the stratified charge injector,
At the time of homogeneous combustion, if the current injection amount is less than or equal to the predetermined injection amount, normal homogeneous combustion control is performed only with the homogeneous combustion injector,
When the current injection amount exceeds the predetermined injection amount, the homogeneous combustion injector performs injection with a substantially maximum injection time that can sufficiently ensure a compression stroke and a period until the end of injection, and calculates an insufficient injection amount. A fuel injection control method for an in-cylinder direct injection CNG engine , wherein the short injection amount is injected at an early stage of a compression stroke by the stratified combustion injector . A spark plug disposed approximately in the center of the combustion chamber;
A stratified combustion injector and a homogeneous combustion injector for injecting CNG fuel into the combustion chamber;
A cavity for stratified combustion formed in a concave shape on the top surface of the piston;
With
The stratified combustion injector has its spray shape and spray angle set so that CNG fuel is injected into the cavity,
The homogeneous combustion injector is disposed in the combustion chamber so that the fuel spray injected from the homogeneous combustion injector does not directly enter the cavity.
The stratified combustion injector and the homogeneous combustion injector both have a minimum injection amount,
A fuel injection control method for an in-cylinder direct injection CNG engine that switches between stratified combustion and homogeneous combustion according to engine operating conditions,
Determining whether or not the stratified combustion injector and the homogeneous combustion injector have failed;
If either one of the injectors is faulty, perform fuel injection control only with the non-failing injector,
If both of the injectors are not faulty, determine whether or not it is a stratified combustion region,
When it is a stratified combustion region, stratified combustion injection control is performed only by the stratified combustion injector,
In the case of a homogeneous combustion region, it is further determined whether or not the current injection amount is a predetermined injection amount or less,
If it is equal to or less than the predetermined injection amount, homogeneous combustion injection control is performed only by the homogeneous combustion injector,
A fuel injection control method for an in-cylinder direct injection CNG engine , wherein when the predetermined injection amount is exceeded, homogeneous combustion injection control is performed by both of the injectors . While the stratified charge injector and the cavity are disposed on the intake side in the combustion chamber,
The fuel injection control method for a direct injection CNG engine according to claim 1 or 2 , wherein the homogeneous combustion injector is disposed on an exhaust side or a central side in the combustion chamber. While the stratified charge injector has an injection rate set so that stratified charge can be burned independently,
The homogeneous combustion injector has its spray angle and injection hole orientation set so that its fuel spray does not enter the cavity directly regardless of the position of the piston,
Further, the two injector according to any one of claims 1-3, characterized in that the maximum injection and maximum during rotation even possible fuel injection in the compression stroke of like injection rate is set A fuel injection control method for an in- cylinder direct injection CNG engine.

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