JP2013092104A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine configured to reduce the amount of NOx and soot contained in exhaust gas, by preventing dispersion of injected fuel.SOLUTION: This internal combustion engine 1 has a fuel injection nozzle 2 for injecting fuel along at least one fuel injection shaft L, and a piston 3 with a cavity 4 formed on a crown surface 6. The internal combustion engine 1 has a straightening passage 10 arranged along the fuel injection shaft L, near the fuel injection nozzle 2. The straightening passage 10 is fixed to the cavity, and atomization fuel injected from the fuel injection nozzle 2 passes through the straightening passage 10.

Description

  The present invention relates to an internal combustion engine that directly injects fuel into a combustion chamber.

  In recent years, development of a direct injection type internal combustion engine that directly injects fuel into a combustion chamber has been promoted in order to improve combustion efficiency and reduce fuel consumption. Specifically, this direct injection internal combustion engine has a configuration in which fuel is sprayed into a space formed by a piston and a cylinder head (hereinafter referred to as a combustion chamber) (see, for example, Patent Document 1). Examples of the internal combustion engine include a diesel engine and a gasoline direct injection engine. Hereinafter, a diesel engine will be described as an example.

  FIG. 5 shows a cross section around the piston 3 of the diesel engine 1X. The diesel engine 1 </ b> X includes a cylindrical piston 3, a fuel injection nozzle 2 </ b> X that injects fuel in the form of a mist, and a cylinder liner 8. The piston 3 has a cavity 4 (for example, a reentrant type) formed through the crown surface (upper surface) 6 of the piston 3 and a piston ring 9.

  Note that the alternate long and short dash line C indicates the center axis C of the piston 3, and the broken line L indicates the center direction of fuel injected from the fuel injection nozzle 2X (hereinafter referred to as the fuel injection axis L). A region 7 surrounded by a dotted line indicates a squish area 7 above the crown surface 6 of the piston 3. The space combining the squish area 7 and the cavity 4 is called a combustion chamber. Further, the x-axis and the z-axis indicate a part of the three-dimensional coordinates in the drawing.

  Next, fuel injection in the diesel engine 1X will be described. The diesel engine 1X directly injects fuel into the cylinder (inside the cavity 4) from the fuel injection nozzle 2X when the piston 3 approaches or separates from the top dead center. The injected fuel becomes split droplets, evaporates while introducing ambient air, and becomes fuel vapor. This fuel vapor burns while being mixed with air. In the diesel engine 1X, promoting the mixing of fuel and air leads to an increase in fuel combustion efficiency, an improvement in fuel efficiency, and a purification of exhaust gas (improvement of exhaust gas performance).

  However, the internal combustion engine that directly injects the fuel has several problems. First, when the internal combustion engine is burned in a state where the mixture of the evaporated fuel and the surrounding air is poor, that is, in a state where the mixing is not uniform, the amount of emissions such as NOx and soot will increase. Have a problem.

  Secondly, there is a problem that the fuel efficiency is lowered. This is because unburned fuel (HC) is generated where the injected fuel is concentrated.

  Hereinafter, the relationship between the fuel mixture state and the exhaust gas (NOx, soot, etc.) will be described. 6 and 7 show the numerical analysis results representing the relationship between the fuel mixture state and the amount of NOx or soot. 6 and 7 show the relationship between the variance from the average value of the local gas mixture concentration and the emission amount (mass) of NOx or soot, and the local average equivalent ratio (φ = 1.5 to 3.0). ) Shown separately. 6 and 7, it can be seen that NOx and soot in the exhaust gas tend to increase when the dispersion is large, that is, the nonuniformity of the fuel concentration is large (the right side of FIGS. 6 and 7). That is, the combustion temperature becomes high in the portion where the fuel becomes lean, and NOx is likely to be generated. Further, in the portion where the fuel is rich, the amount of PM (Particulate Matter) such as soot increases due to the incomplete combustion state.

  FIG. 8 and FIG. 9 show the results of numerical analysis of the distribution of fuel concentration dispersion in the cavity 4. FIG. 8 shows a state immediately after the fuel injection nozzle completes fuel injection. The dark-colored portion in the figure indicates a place where the dispersion of the fuel concentration is high. In particular, in the vicinity of the fuel injection nozzle (right side in FIG. 8) and the tip side of the injected fuel (left side in FIG. 8) It can be seen that the concentration dispersion is high. FIG. 9 shows a state 0.5 seconds after the completion of fuel injection. As in the case immediately after fuel injection (FIG. 8), it can be seen that the dispersion of the fuel concentration is high on the tip side of the injected fuel (left side in FIG. 9).

JP-A-11-190217

  The present invention has been made in view of the above problems, and an object thereof is to suppress dispersion of the concentration of injected fuel in an internal combustion engine such as a diesel engine and a gasoline direct injection engine, and to be included in exhaust gas. An internal combustion engine capable of reducing the amount of NOx and soot produced.

  In order to achieve the above object, an internal combustion engine according to the present invention comprises: a fuel injection nozzle that injects fuel along at least one fuel injection axis; and an internal combustion engine having a piston having a cavity formed on a crown surface. The engine has a rectification passage disposed in the vicinity of the fuel injection nozzle and along the fuel injection axis, and the rectification passage is fixed to the cavity, and the sprayed fuel injected from the fuel injection nozzle is It is configured to pass through the rectifying passage.

  With this configuration, dispersion of the concentration of the sprayed fuel sprayed in the cavity can be suppressed. This is because the generation of turbulent vortices induced by fuel spray can be suppressed, and the time during which the turbulent vortices are maintained can be shortened. In particular, an air flow (for example, a swirl flow or a tumble flow) generated in the cavity can be estimated in advance by a configuration in which the rectifying passage is fixed to the cavity. Therefore, the internal combustion engine can generate an efficient air flow in the cavity, and can further suppress the dispersion of the concentration of the sprayed fuel.

  In the above-described internal combustion engine, the rectifying passage has two rectifying members arranged so as to sandwich the fuel injection shaft from at least both sides. With this configuration, it is possible to suppress the dispersion of the concentration of the sprayed fuel without disturbing the movement of the sprayed fuel. Further, the rectifying passage can be easily installed in the cavity at a low cost.

  In the internal combustion engine described above, the rectifying members of the rectifying passage are arranged at an interval that does not hinder the movement of the sprayed fuel. With this configuration, the rectifying passage can prevent or suppress the occurrence of turbulent flow accompanying the movement of the sprayed fuel without hindering the movement and diffusion of the sprayed fuel.

  According to the internal combustion engine of the present invention, in an internal combustion engine such as a diesel engine and a gasoline direct injection engine, it is possible to suppress the dispersion of the concentration of injected fuel and to reduce the amount of NOx and soot contained in the exhaust gas. An internal combustion engine can be provided.

It is the figure which showed the outline of the fuel injection nozzle periphery of the internal combustion engine of embodiment which concerns on this invention. It is the figure which showed the outline of the fuel injection nozzle periphery of the internal combustion engine of embodiment which concerns on this invention. It is the figure which showed the distribution condition of dispersion | distribution of the fuel concentration of the internal combustion engine of embodiment which concerns on this invention. It is the figure which showed the distribution condition of dispersion | distribution of the fuel concentration of the internal combustion engine of embodiment which concerns on this invention. It is the figure which showed the cross section of the piston of the conventional internal combustion engine. It is the figure which showed the relationship between the dispersion | distribution of the fuel concentration of the conventional internal combustion engine, and the amount of soot. It is the figure which showed the relationship between the dispersion | distribution of the fuel concentration of the conventional internal combustion engine, and the quantity of NOx. It is the figure which showed the distribution condition of dispersion | distribution of the fuel concentration of the conventional internal combustion engine. It is the figure which showed the distribution condition of dispersion | distribution of the fuel concentration of the conventional internal combustion engine.

  Hereinafter, an internal combustion engine according to an embodiment of the present invention will be described. FIG. 1 shows an outline around the fuel injection nozzle 2 in the internal combustion engine 1. The internal combustion engine 1 includes a fuel injection nozzle 2 for injecting fuel along at least one fuel injection axis L, a rectifying passage 10 disposed in the vicinity of the fuel injection nozzle and along the fuel injection axis L, and a crown surface. It has a piston 3 in which a cavity 4 is formed. The rectifying passage 10 is installed on the bottom surface of the cavity 4 and is configured such that the sprayed fuel injected from the fuel injection nozzle 2 passes through the rectifying passage 10. The rectifying passage 10 can be constituted by, for example, two flat rectifying members 11 arranged so as to sandwich the fuel injection shaft L from both sides.

  Here, the configuration of the rectifying passage 10 of the present invention is not limited to the above. The rectifying passage 10 is configured to suppress the generation of turbulent vortices generated around the fuel injection shaft L as the atomized fuel moves, and promote the disappearance of the generated turbulent vortices, particularly in the vicinity of the fuel injection nozzle 2. As long as it has. For example, the rectifying passage 10 may be a cylindrical rectifying passage that covers the entire circumference of the fuel injection shaft L. Further, the shape may be appropriately changed in consideration of the influence on the airflow in the cavity (for example, swirl flow or tumble flow).

  FIG. 2 shows a cross-sectional view of the fuel injection nozzle 2 and a plan view of the cavity 4 having the rectifying passage 10. The cavity 4 has rectifying passages 10 corresponding to the four fuel injection shafts L of the fuel injection nozzle 2. It is desirable that the distance d between the two rectifying members 11 constituting the rectifying passage 10 be narrow as long as the movement of the sprayed fuel injected along the fuel injection axis L is not hindered. The length of the interval d varies depending on the displacement of the internal combustion engine.

  Although FIG. 2 shows the case where the fuel injection nozzle 2 has four injection holes (or fuel injection shafts L), the present invention is not limited to this configuration. The fuel injection nozzle 2 only needs to have at least one injection hole, and may have, for example, the number of injection holes 5 such as 2, 4, 5, 8, and the like.

  With the above configuration, the following operational effects can be obtained. First, dispersion of the concentration of the sprayed fuel sprayed into the cavity 4 can be suppressed. That is, the fuel can be sprayed more uniformly than in the past. This is because, due to the viscosity of the inner surface of the rectifying passage 10, the generation of turbulent vortices induced by fuel spray can be suppressed, and the time for maintaining the turbulent vortices can be shortened.

Second, dispersion of spray fuel concentration can be suppressed regardless of the fuel injection timing. This is because the relative position of the fuel injection nozzle 2 and the rectifying passage 10 is constant regardless of the position of the piston 3. In particular, in an internal combustion engine that performs multi-stage injection, dispersion of spray fuel concentration can be efficiently suppressed.

  Thirdly, by using the rectifying passage 10 as the rectifying member 11 installed on both side surfaces of the fuel injection shaft L, dispersion of the concentration of the sprayed fuel can be suppressed without disturbing the movement of the sprayed fuel.

  As shown in FIG. 2, the rectifying member 11 may be a triangle having a vertex on the fuel injection nozzle 2 side in the plan view. With this configuration, the influence of the rectifying member 11 on the air flow in the cavity 4 can be suppressed. That is, the dispersion of the concentration of the sprayed fuel can be suppressed. Further, the rectifying member 11 is not limited to the above-described shape, and can be configured in a rectangular shape, an elliptical shape, or the like in the plan view.

  3 and 4 show the distribution of the fuel concentration dispersion in the internal combustion engine 1. FIG. 3 shows a state immediately after the fuel injection nozzle has completed the fuel injection. FIG. 4 shows a state 0.5 seconds after the completion of fuel injection. In addition, the dark-colored part in a figure has shown the place where dispersion | distribution of fuel concentration is high.

  Comparing FIGS. 3 and 4 showing the state of the internal combustion engine 1 of the present invention with FIGS. 8 and 9 showing the state of the conventional internal combustion engine 1X, the internal combustion engine 1 of the present invention has a dispersion of spray fuel concentration. It can be seen that the above can be efficiently suppressed. That is, the internal combustion engine 1 of the present invention can spray the fuel more uniformly than before, can suppress the generation of NOx and soot, and improve the exhaust gas performance.

1 Internal combustion engine (diesel engine, gasoline direct injection engine)
2 Fuel injection nozzle 3 Piston 4 Cavity 6 Crown surface 10 Rectification passage 11 Rectification member L Fuel injection axis d Interval

Claims (2)

  An internal combustion engine having a fuel injection nozzle for injecting fuel along at least one fuel injection axis and a piston having a cavity formed on a crown surface, wherein the internal combustion engine is in the vicinity of the fuel injection nozzle and on the fuel injection axis. The rectifying passage is disposed along the rectifying passage, the rectifying passage is fixed to the cavity, and the sprayed fuel injected from the fuel injection nozzle passes through the rectifying passage. Internal combustion engine.   2. The internal combustion engine according to claim 1, wherein the rectifying passage has two rectifying members arranged so as to sandwich the fuel injection shaft from at least both sides.

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