JP2008267155A - Fuel injector for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the fuel injector for diesel engine characterized in that NO<SB>X</SB>and smoke are reduced in the diesel engine of direct injection type having a reentrant type cavity at a piston top of each cylinders, in which cavity swirl is formed by enlarging penetration of an injected fuel posterior to the fuel spray having collided with a wall surface by virtue of GHN (Group Holes Nozzles) characteristics so as to intensify the longitudinal swirl of the fuel spray and burnt gas. <P>SOLUTION: The fuel injector is arranged such that the fuel injected from two holes 21 and 22 comprising the respective groups of holes 20 of a fuel injection nozzle 15 collides with the wall surface of the cavity 11 at two collision points A and B, and a line A-B interconnecting the collision points A and B tilts or runs crosswise with regard to a vertical line V, and the collision point A located to the front of the direction to which the swirl S flows with respect to a horizontal axis H is displaced by an angle (collision points twist angle θ) ranging from -15 degrees to 45 degrees from the other collision point B. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a direct injection diesel engine having a reentrant type cavity at the top of a piston, and more particularly to a fuel injection device for a direct injection diesel engine in which a swirl of intake air is formed in the reentrant type cavity.

  A fuel injection nozzle (a so-called group hole nozzle) configured to have a plurality of injection hole groups each including a plurality of injection holes, and in which fuel injected from the plurality of injection holes of each injection hole group forms one fuel spray. In a fuel injection device for a direct injection diesel engine equipped with GHN), the atomization of fuel is promoted by devising the distance and angle between the injection holes of the injection hole group, and smoke (black smoke) is generated. It has been conventionally proposed to reduce the above (see, for example, Patent Document 1). GHN is intended to increase the number of injection holes and secure the flow area of the injection holes as a whole while reducing the diameter of the injection holes and atomizing the fuel. Compared with a normal single hole nozzle (SHN for short) that forms a fuel spray, the distance between the plurality of injection holes of the injection hole group is short, so that when the fuel is injected, the sprays collide with each other. In some cases, the droplets become large, and the original purpose of reducing smoke by atomizing the fuel cannot be achieved. Therefore, the proposed technique is to promote atomization of fuel and reduce the generation of smoke (black smoke) by devising the distance and angle between the injection holes of the injection hole group.

  Also, it is a direct injection diesel engine with a reentrant type cavity at the top of the piston, the injection nozzle is SHN type, the spray penetration toward the cavity wall is increased, and fuel spray is applied to the lip of the cavity wall during the ignition delay period By forming the fuel vapor near the lip and promoting the generation of vertical vortices in the cavity by the expansion flow (combustion expansion flow) caused by the combustion immediately after ignition, heat spots are reduced and disappeared early. In addition, it has been conventionally known that the generation of NO is suppressed and the reburning of soot in the combustion gas is promoted by the vertical vortex to reduce the generation of smoke (for example, see Patent Document 2). .

JP 2001-165017 A JP 2002-364367 A

  In order to reduce smoke (black smoke) discharged from a direct injection diesel engine having a reentrant type cavity at the top of the piston, it is effective to promote fuel atomization by using GHN (group hole nozzle). However, in order to further enhance the effect of reducing smog and to sufficiently reduce nitrogen oxide (NOx) together with smoke, combustion atomization is promoted by promoting fuel atomization and strengthening vertical vortices in the cavity. It is important to promote reburning by mixing with excess air. In order to strengthen the vertical vortex in the cavity, in addition to increasing the spray penetration and strengthening the vertical vortex caused by the combustion expansion flow, the penetration after the wall collision of the fuel spray is increased and the downstream of the combustion region It is important to enhance the fuel spray and the vertical wraparound of the burned gas.

  The fuel spray injected into the combustion chamber of the diesel engine collides with the cavity wall surface during the ignition delay period and spreads along the wall surface by setting the appropriate spray penetration. The fuel spray burns best near the wall surface, and the combustion gas (burned gas) rides on the flow of the vertical vortex by the combustion expansion flow together with the fuel spray, and goes around the cavity wall surface in the vertical direction. When the entrained fuel spray and burned gas quickly reach the center of the cavity, there is low temperature surplus air that contains a large amount of oxygen that is not used for combustion. The burning gas is rapidly cooled by mixing with low-temperature surplus air, reducing the generation of NOx, and the soot contained in the burning gas comes into contact with oxygen and reburns, reducing smoke. The

  Therefore, by reinforcing the fuel spray and the wraparound of the burned gas in the vertical direction, the burned gas can be quickly mixed with surplus air, thereby reducing NOx and re-burning the soot for smoke. It is possible to reduce.

  In order to strengthen the fuel spray and burned gas in the vertical direction, in addition to the appropriate spray penetration, the fuel spray penetration after the wall collision is increased in a direction that contributes to the vertical direction This is very important. And the penetration after the wall surface collision can be strengthened by utilizing the characteristics of the spray shape after the wall surface collision of the GHN. In other words, if the injection nozzle of the fuel injection valve is set to GHN and the number of injection holes in each injection hole group is two, for example, the spread of the fuel spray after the wall surface collision becomes elliptical, and the penetration in one direction (long axis direction) is growing. Utilizing this characteristic, it is possible to enhance the fuel spray and the wraparound of the burned gas in the vertical direction.

  However, in GHN, depending on how the injection holes of each injection hole group are arranged, the penetration enhancement after the fuel spray wall surface collision may not necessarily contribute to the vertical wraparound. In particular, in the case of a diesel engine in which a swirl of intake air is formed in the combustion chamber (cavity), there is an influence of swirl, and depending on the arrangement of the injection holes and the injection direction, the penetration characteristics after wall collision may be Not only does it contribute to wraparound, it can also negatively affect it.

  The conventional technology does not consider that the penetration characteristics of the fuel spray after collision with the wall surface act in the direction that contributes to the vertical wraparound enhancement of the fuel spray and burned gas, and in particular, has a reentrant type cavity. However, in the diesel engine in which the swirl of the intake air is formed in the combustion chamber, the influence of the swirl on the penetration characteristics of the fuel spray after the GHN wall collision is not taken into consideration.

  The present invention relates to a direct injection diesel engine having a reentrant type cavity at the top of a piston, and a swirl of intake air formed in the cavity, and a fuel injection valve having injection hole groups each consisting of a plurality of injection holes The atomization of the fuel and the swirl flow in the cavity are taken into consideration, and the penetration after the collision of the fuel spray wall surface is increased so that the fuel spray and burned gas wrap around the bottom bottom of the cavity. The aim is to strengthen and reduce the exhausted NOx and smoke.

  The fuel injection device for a diesel engine according to the present invention has a reentrant type cavity that is recessed at the top of the piston in each cylinder with the piston operating direction as the axial direction and has a smaller diameter on the opening end side. A fuel injection device for a diesel engine comprising a fuel injection valve that directly injects fuel from above in a cavity axial direction toward the wall surface of the cavity into a combustion chamber of the diesel engine where a swirl of intake air is formed, The fuel injection valve has a plurality of injection hole groups each consisting of two injection holes, and each of the two injection holes of the injection hole group has a fuel spray injected from the two injection holes. The injection directions of the fuel injected from these two injection holes are adjacent to the wall surface of the cavity as viewed from the cavity axial direction. The two points that are substantially orthogonal to each other and that are adjacent to each other are arranged at an interval when viewed from the direction orthogonal to the cavity axis direction, and the line connecting the two points is inclined or orthogonal to the cavity axis direction, One point which is the front side of the swirl flow direction with respect to the direction orthogonal to the axial direction is arranged in a predetermined angular range centering on a position shifted by a predetermined angle above the other axial point in the cavity axial direction. It is formed.

  The predetermined angle range is defined by taking an angle in a direction in which one point, which is the front side of the swirl flow direction with respect to the direction perpendicular to the cavity axis direction, is shifted to the upper side in the cavity axis direction from the other point, − It should be 15 to 45 degrees.

  By configuring the fuel injection device in this way, fuel atomization can be promoted, and penetration after the fuel spray wall collision can be strengthened along the swirl flow direction, thereby fuel spray downstream of the combustion region. In addition, the wraparound of burnt gas can be enhanced. As a result, burned gas can be quickly mixed with surplus air, burned gas can be rapidly cooled to suppress NOx generation, and reburning of soot in burned gas is promoted NOx and smoke exhausted can be reduced.

  The fuel spray and the wraparound of the burned gas proceed obliquely downward (obliquely downward in the cavity axis direction) while being swirled by the swirl. As in the present invention, the injection directions of the fuel injected from the two injection holes are substantially orthogonal to each other at two points adjacent to each other on the wall surface of the cavity as viewed from the cavity axial direction, and the two adjacent points. Are arranged at an interval when viewed from a direction perpendicular to the cavity axis direction, and the line connecting the two points is inclined or perpendicular to the cavity axis direction and the swirl flow direction relative to the direction perpendicular to the cavity axis direction The fuel injection valve is configured so that one point which is the front side of the fuel cell has a predetermined angle range centering on an angle shifted upward in the cavity axial direction from the other point, thereby penetrating the fuel spray after the wall collision The direction of strengthening will be along the above-mentioned diagonally downward direction as it is swept by the swirl, thereby enhancing the vertical wrapping of fuel spray and burned gas. . The effect of strengthening the wraparound is that the above angle is an angle in a direction in which one point which is the front side of the swirl flow direction with respect to the direction perpendicular to the cavity axis direction is shifted to the upper side in the cavity axis direction from the other point. When the angle is -15 degrees to 45 degrees, with a positive side.

  Thus, according to the present invention, fuel atomization is promoted and penetration after fuel spray wall collision is strengthened along the flow direction of the swirl so that the fuel spray downstream of the combustion region and the longitudinal direction of the burned gas Can be strengthened to reduce exhausted NOx and smoke.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an embodiment of the present invention. FIG. 1 is a cross-sectional view of the vicinity of a combustion chamber of a diesel engine according to the embodiment. FIG. 2 is a view for explaining the flow direction of a swirl in the combustion chamber and the behavior of fuel spray and combustion gas by simulation. Explanatory view shown in a perspective view from above, (b) is an explanatory view showing a longitudinal section parallel to the fuel injection direction including the piston axis, and FIG. 3 shows the flow direction of swirl in the combustion chamber and the fuel spray and combustion gas by the simulation. In order to explain the behavior, (a) is an explanatory view showing a longitudinal section perpendicular to the fuel injection direction including the piston axis, (b) is an explanatory view shown in plan view, and FIG. 4 is a wall surface in the combustion chamber. FIG. 5 is a diagram for explaining the penetration after the collision, and FIG. 5 shows the relationship between the angle related to the arrangement of the injection holes in the fuel injection device and the penetration after the wall collision. It is a graph comparing with other examples.

  The diesel engine of this embodiment is an in-line multi-cylinder engine. As shown in FIG. 1, a cylinder head 2 is disposed on the upper part of the cylinder block 1, and the cylinder bore 3 of each cylinder formed in the cylinder block 1 is vertically moved. A piston 4 is operably disposed, and a combustion chamber 5 is defined by the cylinder head 2, the cylinder bore 3, and the piston 4. The cylinder head 2 is provided with a swirl-type intake port (helical port) 6 and an exhaust boat 7 for each cylinder, and an intake valve 8 and an exhaust valve are respectively opened and closed to open and close the intake port 6 and the exhaust port 7. 9 is disposed. A fuel injection valve 10 is attached to the cylinder head 2 at a position facing substantially the center of the combustion chamber 5 of each cylinder. The cylinder head 2 is a flat type, and the intake valve 8 and the exhaust valve 9 are upright.

  At the top of the piston 4 is formed a reentrant cavity 11 which is recessed with the piston operating direction (vertical direction in FIG. 1) as the axial direction and having a smaller diameter on the opening end side.

  The cavity 11 constitutes the combustion chamber 5 and forms an annular lip portion 12 whose opening edge near the top surface of the piston 4 protrudes inward in the piston radial direction. An annular recess 13 that is recessed outward in the direction is formed, and a bottom central portion of the cavity 11 located at the center in the piston radial direction has a raised portion 14 that protrudes toward the opening end side of the cavity 11. Forming.

  In the combustion chamber 5, a swirl of intake air is generated in the intake stroke, whereby a swirl S is formed in the cavity 11 near the compression top dead center.

  The tip of the fuel injection valve 10 constitutes an injection nozzle 15, and the injection nozzle 15 slightly protrudes into the combustion chamber 5 so as to inject fuel directly into the cavity 11 at the top of the piston 4.

  The fuel injection nozzle 15 is provided with a plurality of injection hole groups 20 (see FIG. 3) each having two injection holes 21 and 22 arranged in the circumferential direction at substantially equal intervals. The number of the nozzle hole groups 20 is 5 to 12.

  From the injection holes 21 and 22 of each injection group 20, fuel is injected obliquely downward from above in the cavity axial direction (piston axial direction) toward the wall surface of the lip 12 of the cavity 11 at the top of the piston 4. Each injection group 20 forms a fuel spray 31 of one (a lump) of fuel injected from the two injection holes 21 and 22. The angle formed by the center lines of the fuel sprays 31 is usually 145 to 160 degrees.

  Each of the two injection holes 21 and 22 of each injection hole group 20 has an injection direction of fuel injected from the two injection holes 21 and 22 from the cavity axis direction, as shown in FIG. The two points (collision point A and collision point B) that are adjacent to each other on the wall surface of the cavity 11 as viewed are substantially orthogonal to each other, and these two adjacent points (collision point A and collision point B) are in the cavity axial direction. The line AB connecting the two points (collision point A and collision point B) is inclined or orthogonal to the cavity axis direction (the direction of the vertical line V). (Inclined in the example shown), one point (collision point A) that is the front side of the flow direction (arrow direction) of the swirl S with respect to the direction orthogonal to the cavity axis direction (the direction of the horizontal axis H), Cavity axis direction than other point (collision point B) Predetermined angle on the upper side of (or in some cases theta = 0) which is formed (about 15 degrees) at an angle deviating (collision point twist angle theta) disposed in a predetermined angular range around the position shifted as.

  The predetermined angle range is a direction in which the collision point A which is the front side in the flow direction of the swirl S with respect to the direction orthogonal to the cavity axis direction (the direction of the horizontal axis H) is shifted to the upper side in the cavity axis direction from the collision point B. The angle is preferably in the range of θ = −15 degrees to 45 degrees with the plus side as the plus side. In particular, the vicinity of θ = 15 degrees is the best.

  When the collision point twist angle θ is a positive angle, the two injection holes 21 and 22 forming one injection hole group 20 are shifted vertically and the lower injection hole 22 with respect to the upper injection hole 21. Is shifted to the rear side in the swirl flow direction.

  2 and 3, the flow direction of the swirl S in the combustion chamber 5 (cavity 11) is clockwise when viewed from above the cavity axial direction (the direction of the vertical line V) to form one injection hole group 20. The two injection holes 21 and 22 are displaced from each other up and down, and the lower injection hole 22 is displaced from the upper injection hole 21 to the rear side in the swirl flow direction and is injected from the two injection holes 21 and 22. A straight line AB connecting the collision points A and B when the fuel collides with the wall surface of the cavity 11 forms an angle θ (collision point twist angle) with respect to an axis (horizontal axis H) orthogonal to the cavity axis. The collision point twist angle θ is 30 degrees, with the angle in the direction in which the collision point A, which is the front side in the swirl flow direction, deviating from the collision point B, which is the rear side, to the upper side in the cavity axis direction is the plus side. Shows the case.

  The fuel spray (fuel spray 31) injected into the combustion chamber 5 collides with the wall surface of the cavity 11 during the ignition delay period and spreads along the wall surface of the cavity 11 together with the air-fuel mixture 32. The fuel spray 31 burns in the vicinity of the colliding wall surface, and the fuel spray 31A and the burned gas (combustion gas) 33 after the wall collision collide with the flow of the vertical vortex caused by the combustion expansion flow, And wrap around vertically along the bottom of the bottom. At that time, the fuel spray 31 </ b> A and the burned gas 33 circulate in the direction of the arrow T while being passed through the swirl S. When the wraparound is strong in the vertical direction, the fuel spray 31 </ b> A and the burned gas 33 quickly reach the center of the cavity 11.

  Near the center of the cavity 11, there is low-temperature surplus air 34 containing a large amount of oxygen that is not used for combustion. Then, as shown by the solid line in the graph of FIG. 5, when the collision point twist angle θ is −15 degrees to 45 degrees, the penetration of the fuel spray 31A and the burned gas 32 after the wall collision is in the swirl flow direction. It is strengthened in the direction along which the fuel spray 31A and the burned gas 32 downstream of the combustion region 35 can be strengthened in the vertical direction. As a result, the burned gas 32 can be quickly mixed with the surplus air 34, the burned gas 32 can be rapidly cooled to suppress generation of NOx, and soot in the burnt gas 32 is reburned. NOx and smoke emitted can be reduced.

  In the graph of FIG. 5, the horizontal axis is the collision point twist angle θ, the vertical axis is the penetration after wall collision, the solid line is GHN (group hole nozzle), and there is a swirl (positive swirl in the positive direction). The characteristics in the case of GHN without swirl are shown. As shown in this graph, when there is a swirl at GHN, if the collision twist angle θ is in the range of about −15 degrees to 45 degrees, two injections with SHN (single hole nozzle) and an injection hole area of GHN A large penetration exceeding the penetration when the hole area of the hole is equal is obtained, and the effect of strengthening the penetration is particularly large in the range of about 5 to 25 degrees with the collision twist angle θ around 15 degrees. . When the collision twist angle θ exceeds 45 degrees and becomes larger on the plus side, the penetration becomes worse than SHN. Further, when the collision twist angle θ exceeds −15 degrees and becomes larger on the negative side, the penetration becomes worse than SHN.

  When the flow direction of the swirl S in the combustion chamber 5 is counterclockwise, an appropriate positional relationship (the predetermined angle range) of the two injection holes 21 and 22 of the single injection hole group 20 is only the injection holes 21 and 22. The direction of the swirl S flow is reversed from that in the clockwise direction. However, in terms of the relationship with the flow direction of the swirl S, the predetermined angular range is still the direction perpendicular to the cavity axis direction (the horizontal axis H Θ = −15 degrees to 45 degrees is preferable, with an angle in a direction in which the collision point A on the front side in the flow direction of the swirl S is shifted to the upper side in the cavity axis direction from the collision point B with respect to the plus direction. In particular, when the vicinity of 15 degrees is the best, and the collision point twist angle θ is a plus angle, the two injection holes 21 and 22 forming one injection hole group 20 are shifted up and down and Lower injection hole with respect to the injection hole 21 22 becomes the arrangement | positioning shifted | deviated to the back side of the flow direction of a swirl.

  6 relates to the penetration after wall collision of the fuel injection device of the diesel engine of the above embodiment, the spray after wall collision when the fuel is injected to the wall surface in the case of one injection hole and two injection holes. The results of measuring the shape are shown. (A) and (b) are explanatory diagrams of measurement results when there is one injection hole, and (c) and (d) are explanatory diagrams of measurement results when there are two injection holes. is there. From the measurement result shown in FIG. 6, when the fuel spray 31 normally injected from one injection hole 23 collides with the wall surface, the spray 31A after the collision spreads concentrically. The injection holes 21 and 22 are arranged adjacent to each other with an appropriate distance, and the fuel spray 31 injected from the two injection holes 21 and 22 becomes one spray 31 and collides with the wall surface of the cavity 11. It can be seen that the spread of the spray 31A after the collision is amplified in a direction orthogonal to the line connecting the two injection holes 21 and 22, and spreads in an elliptical shape. By utilizing this characteristic, the penetration after the wall collision can be strengthened in accordance with the flow direction of the swirl S, thereby enhancing the vertical wrapping of the fuel spray 31A and the burned gas 32 after the wall collision. can do.

  7 and 8 show the flow direction of the swirl and the behavior of the fuel spray and the combustion gas due to the simulation when there is one injection hole. The flow direction of the swirl in the combustion chamber 5 (cavity 11) is clockwise, and the fuel injected from one injection hole 23 collides with the wall surface of the cavity 11 around one point (collision point). In this case, the spread of the fuel spray 31A after the wall collision is concentric, the penetration along the flow direction of the swirl S is small, and the wraparound of the fuel spray 31A and the burned gas 32 after the wall collision is weak.

  9 and 10 show the case where the arrangement of the two injection holes with respect to the flow direction of the swirl is opposite to that of the above-described embodiment of the present invention, that is, the flow direction of the swirl S in the combustion chamber 5 (cavity 11) is clockwise. 2, the positional relationship between the two injection holes 21 and 22 is opposite to that shown in FIG. 2, and the lower injection hole 22 is shifted from the upper injection hole 21 to the front side in the flow direction of the swirl S, and the collision point twist angle. The swirl when θ is −30 degrees, where the angle of the direction in which the collision point A on the front side in the flow direction of the swirl S is shifted to the upper side in the cavity axis direction from the collision point B on the rear side is positive. The flow direction of fuel and the behavior of fuel spray and combustion gas by simulation are shown. In this case, the spread of the fuel spray 31A after the wall surface collision is such that the characteristics of the GHN are opposed to the flow of the swirl, and the penetration is reduced. Therefore, the wraparound in the vertical direction of the fuel spray 31A and the burned gas 32 after the wall collision is further weaker than in the case of SHN.

It is sectional drawing of the combustion chamber vicinity of the diesel engine which concerns on embodiment of this invention. The flow direction of the swirl in the combustion chamber of the diesel engine of the embodiment of the present invention and the behavior of the fuel spray and combustion gas due to the simulation are explained, (a) is an explanatory view shown by a perspective view obliquely from the top of the piston top, b) is an explanatory view showing a longitudinal section parallel to the fuel injection direction including the piston axis. The flow direction of the swirl in the combustion chamber of the diesel engine of the embodiment of the present invention and the behavior of fuel spray and combustion gas by the simulation will be described. (A) includes the piston axis and is orthogonal to the fuel injection direction in plan view. Explanatory drawing shown by a longitudinal section, (b) is explanatory drawing shown by a top view. It is explanatory drawing explaining the penetration after the wall surface collision in the combustion chamber of the diesel engine of embodiment of this invention. It is a graph which shows the relationship between the angle regarding the arrangement | positioning of the injection hole in the fuel-injection apparatus of the diesel engine of embodiment of this invention, and the penetration after a wall surface collision, and compares with another example. In relation to the penetration after wall collision of the fuel injection device of the diesel engine of the embodiment of the present invention, the spray shape after wall collision when fuel is injected to the wall surface in the case of one injection hole and two cases (A) and (b) are measurement result explanatory diagrams when there is one injection hole, and (c) and (d) are measurement result explanatory diagrams when there are two injection holes. . In relation to the flow direction of swirl and the behavior of fuel spray and combustion gas in the combustion chamber of the diesel engine according to the embodiment of the present invention, the flow direction of swirl and the fuel spray and combustion gas due to simulation in the case of one injection hole (A) is an explanatory view shown by a perspective view obliquely from the top of the piston top, and (b) is an explanatory view showing a longitudinal section including the piston axis and parallel to the fuel injection direction. In relation to the flow direction of swirl and the behavior of fuel spray and combustion gas in the combustion chamber of the diesel engine according to the embodiment of the present invention, the flow direction of swirl and the fuel spray and combustion gas due to simulation in the case of one injection hole (A) is an explanatory view showing a longitudinal section including the piston axis and orthogonal to the fuel injection direction in a plan view, and (b) is an explanatory view showing the plan view. In relation to the flow direction of the swirl in the combustion chamber of the diesel engine of the embodiment of the present invention and the behavior of the fuel spray and combustion gas by the simulation, the arrangement of the two injection holes with respect to the flow direction of the swirl is opposite to the present invention The flow direction of the swirl and the behavior of the fuel spray and the combustion gas by the simulation are explained. (A) is an explanatory view shown by a perspective view obliquely from the top of the piston top part, and (b) includes the piston axis in the fuel injection direction. It is explanatory drawing shown with a parallel longitudinal cross-section. In relation to the flow direction of the swirl in the combustion chamber of the diesel engine of the embodiment of the present invention and the behavior of the fuel spray and combustion gas by the simulation, the arrangement of the two injection holes with respect to the flow direction of the swirl is opposite to the present invention The flow direction of the swirl and the behavior of the fuel spray and the combustion gas by the simulation are illustrated. (A) is an explanatory view showing a longitudinal section including the piston axis and orthogonal to the fuel injection direction in plan view, (b) It is explanatory drawing shown with a top view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 3 Cylinder bore 4 Piston 5 Combustion chamber 10 Fuel injection valve 11 Cavity 15 Injection nozzle 20 Injection hole group 21, 22 Injection hole 31, 31A Fuel spray 32 Mixture 33 Burned gas (combustion gas)
34 Excess air 35 Combustion zone A, B Collision point θ Collision point twist angle S Swirl

Claims (2)

A diesel engine that has a reentrant cavity that is recessed at the top of the piston in each cylinder with the piston operating direction as the axial direction and has a reduced diameter on the open end side, and a swirl of intake air is formed in the cavity. A fuel injection device for a diesel engine comprising a fuel injection valve that directly injects fuel from above in the cavity axial direction toward the wall surface of the cavity in the combustion chamber,
The fuel injection valve has a plurality of injection hole groups each consisting of two injection holes,
In each of the two injection holes of the injection hole group, the fuel injected from the two injection holes forms one fuel spray, and the injection direction of the fuel injected from the two injection holes is the cavity axis direction. Viewed from above, the two points adjacent to each other on the wall surface of the cavity are approximately orthogonal to each other, and these two adjacent points are arranged at an interval when viewed from the direction orthogonal to the cavity axis direction. The connecting line is inclined or orthogonal to the cavity axis direction, and one point which is the front side of the swirl flow direction with respect to the direction orthogonal to the cavity axis direction is a predetermined angle above the other point in the cavity axis direction. A fuel injection device for a diesel engine, wherein the fuel injection device is formed so as to have an arrangement in a predetermined angle range centered on a shifted position. The predetermined angle range is defined by taking an angle in a direction in which one point, which is the front side of the swirl flow direction with respect to the direction perpendicular to the cavity axis direction, is shifted to the upper side in the cavity axis direction from the other point, − The fuel injection device for a diesel engine according to claim 1, which is 15 to 45 degrees.

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