JPH0637851B2 - Combustion device for a diesel engine - Google Patents

Description

The present invention relates to side-injection (as opposed to central-injection) diesel engines.

FIG. 1 is a sectional view showing a main part of this type of engine. Reference numeral 01 is a combustion chamber, 02 is a piston, 03 is an exhaust valve, 04 is a fuel valve, and 05 is a fuel spray. FIG. 2 is a sectional view taken along the line II-II in FIG. 1, in which 04 is a fuel valve and 06, 07 and 08 are fuel sprays. FIG. 3 is a front view of the fuel valve 04 shown in FIG.
Reference numerals 9, 10, and 11 are nozzles (equal nozzle diameters, equal intervals).

In the above structure, the combustion chamber 0
The air in 1 is compressed into high temperature and high pressure, and the fuel is injected from the fuel valve 04 in the vicinity of the top dead center to form fuel sprays 06 to 08 as shown in FIG. These sprays are formed so that the air in the entire area of the combustion chamber can be used as much as possible, and the relatively strong air vortex promotes the mixing of fuel and air, resulting in combustion with high air utilization rate and combustion efficiency. Has the following drawbacks.

As shown in FIG. 2, the atomized fuel develops as a flame while being bent by the air vortex S _W. At this time, due to the difference in relative velocity between the fuel spray and the air vortex and the difference in the upstream and downstream positions of the vortex, the effect of the air vortex is strong on the spray on the central side of the combustion chamber and weak on the spray on the outer peripheral side. However, since the penetration force of the spray is the same as that of each spray, the spray on the center side is greatly bent, and the spray on the outer peripheral side is bent less. Therefore, the whole spray develops in a lump,
In this region, spray or flames interfere with each other and combustion is hindered. Furthermore, since the spray in the central part is greatly bent,
Since there is an unused area of air in the center of the combustion chamber, the air utilization rate decreases. Further, since all the fuel spray reaches the wall of the combustion chamber on the opposite side at the same time, the air shortage occurs in this portion and combustion is hindered.

As a result, in the conventional system, the spatial and temporal fuel distribution to the combustion chamber is not appropriate, and the air utilization rate and combustion efficiency become insufficient.

The object of the present invention is to pay attention to the above points, and in a side-injection type (for central injection) diesel engine, improves spatial and temporal fuel dispersion in the combustion chamber, improves air utilization rate, combustion efficiency. To provide a combustion device capable of performing high-combustion, which is characterized by having a plurality of fuel valves each having a plurality of nozzles in the periphery of the combustion chamber of the cylinder head. In a combustion device for a diesel engine in which an air vortex is formed in the interior of the combustion chamber, which is the central part of the combustion chamber In each of the nozzle groups such as the plurality of nozzle groups that form the spray and the plurality of nozzle groups that form the spray on the outer periphery of the combustion chamber, the ratio of the nozzle diameter d of the adjacent nozzles to the nozzle spacing S is S / d <5,
Angle α formed by the axial center line of each nozzle on the horizontal plane and angle β formed by the axial center line of each nozzle on the vertical plane
However, with the axis approaching as the distance from the nozzle increases, the nozzles are formed so that -9 ° <α11 ° and -9 ° <β <11 °, respectively. The spray groups are combined into one, and the combined spray group develops as one spray, and when the number of nozzles is a positive integer and the number of spray nozzles is 2n, n sprays are formed as a whole. In the case of 2n + 1, n + as a whole
To form one spray.

Embodiments according to the present invention will be described below with reference to the drawings.

FIG. 4 is an explanatory view showing a tip portion of a fuel valve of one embodiment according to the present invention, and FIG. 5 is an explanatory view showing a combination of two adjacent sprays when the fuel valve according to the present invention is used. Spout N ₃
And N ₄ and the nozzles N ₁ and N ₂ are the same. FIG. 6 is a projection view of the nozzle and the center line of the nozzle on the horizontal plane, that is, VI of FIG.
FIG. 7 is a projection view of the nozzle and the center line of the nozzle on a vertical plane, that is, a VII arrow view of FIG. FIG. 8 shows α = β =
In the diagram showing the effect of S / d on the increase in the reaching distance of coalescence in the case of ₀ , x ₀ is the reaching distance of one spray, and x is the reaching distance at the time of coalescence. FIG. 9 is a diagram showing the effect of α and β on the reaching distance of coalescence. FIG. 10 is an explanatory view showing a fuel dispersion state in the combustion chamber when the fuel valve of the embodiment according to the present invention is used. The case where two sprays in the vicinity of the center of the combustion chamber and two sprays in the outer peripheral portion of the combustion chamber are combined into four spray nozzles to form two sprays as a whole is shown.

Generally, when the number of nozzles is 2n (n is a positive integer), n sprays are formed as a whole by coalescence. In addition, when the number of nozzles is 2n + 1, n + 1 sprays are formed as a whole by uniting.

_N 1 to N ₄ of FIG. 4 shows the injection port of the fuel valve according to the invention (4 For injection port).

2θ in FIG. 5 indicates the spread angle of the injection port.

In FIG. 6, α represents the angle formed by the axial center lines of the adjacent nozzles in the projection of the fuel valve shown in FIG. 4 on the horizontal plane (the case where the distance from the nozzle approaches the nozzle is positive).

Similarly, β in FIG. 7 indicates the angle formed by the axial center lines of the adjacent nozzles when projected onto the vertical plane (the case where the nozzles approach each other as they move away from the nozzle is positive).

In FIG. 10, 12 is a combustion chamber, 13 is a fuel valve, and 14
To 17 the fuel spray formed when using a fuel valve of the present invention, S _W denotes a combustion chamber air vortex.

The operation of the above configuration will be described.

When the fuel valve according to the present invention is used, when the number of all the orifices is made uniform and the number of orifices is increased (for example, from 3 holes to 4 holes), the orifice area per nozzle is narrowed and each spray is finely divided. The formation of a spray with good air introduction is promoted.

Further, since the plurality of sprays on the center side of the combustion chamber and the sprays on the outer side are combined, the penetration force of each spray is higher than that of a single spray.

When the fuel valve according to the present invention is used as described above,
As shown in the example of four holes in the figure, two fuel sprays are formed as a whole with good air introduction characteristics, strong penetration force, and long reach.

In the above case, there are the following effects.

In the conventional device using a fuel valve, since the penetration force of each spray is equal, the inner spray is largely bent by the air vortex, the interference between sprays increases, and combustion is hindered. The space remains and the air utilization rate decreases. Furthermore, in order to increase the amount of air introduced into the entire mist, increasing the number of mist inevitably reduces the nozzle diameter of each nozzle, reducing the penetrating force of the mist and the effect of air vortex flow being relatively large. As a result, the above combustion inhibition and the decrease in the air utilization rate become larger.

In the case of the present invention, the outer spray group and the inner spray group are combined as shown in FIG. 5, so that the penetration force of each spray increases and the center of the combustion chamber strongly affected by the air vortex S _W. It is possible to prevent the side spray from being greatly bent and interfering with the outside spray. Further, the straightness of the spray is increased, and the fuel can be dispersed in the space near the center of the combustion chamber.

Here, the spread angle of the spray is 2θ shown in FIG.
= 2 tan ^-1 {0.427 (ρ _a / ρ _f ) ^0.35 }, ρ _a = air density,
ρ _f : Since it is the fuel density, it is usually around 2θ = 15 °. Further, as shown in FIG. 6, in the projection of two adjacent sprays on the horizontal plane, the angle formed by the axis of each spray is α, and similarly, the axis of each spray in the projection on the vertical plane is Let β be the angle formed by (both α and β are positive when the spray approaches as it moves away from the nozzle). When two adjacent sprays are parallel (that is, when α = β = 0), the injection port diameter d
The ratio S / d of the space S between the injection port and the nozzle outlet determines the state of coalescence, and as shown in the experimental results in Fig. 8, when S / d <5, the effect of increasing the penetrating force due to coalescence is large, and It is desirable that d be 5 or less (x is the total reach of two adjacent sprays, x ₀ is the reach of a single spray).

Even if the sprays are not parallel and are not on the same plane (even if they are in a spatially twisted positional relationship), S in FIG.
As shown by the experimental results of the spray reach distance by α and β when / d = 3, (x is the reach distance of two adjacent sprays as a whole, and x ₀ is the reach distance of one spray. ), Especially when -9 ° <α <11 ° and -9 ° <β <11 °, the reaching distance becomes larger than that of a single spray, and the effect of increasing the penetration force by spray coalescence is greatly obtained.

This condition is determined by the formation characteristic (spreading characteristic) of the fuel spray in the diesel engine, that is, the spread characteristic of the fuel spray is determined by the ratio of the gas density and the fuel density in the fuel chamber. The conditions are almost the same, and the spread characteristics of the fuel spray are almost the same. Therefore, the above conditions of S / d <5 of -9 ° <α <11 ° and -9 ° <β <11 ° are absolute conditions for obtaining the effect of spray coalescence in the diesel engine.

As described above, the ratio between the nozzle diameter d and the nozzle outlet spacing S is S / d <
5, and in each of the outer spray group and the inner spray group, the angle α formed by the projection of the axis line of the adjacent spray on the horizontal plane and the angle β formed by the projection on the vertical plane are −9 ° <α <11
By forming the nozzles so that the angle becomes -9 ° and -9 ° <β <11 °, Fig. 10 shows the case where two outer sprays and two inner sprays are combined at four nozzles. In addition, the penetration force of each spray group is increased, mutual interference can be prevented, and the fuel can be dispersed in the space near the center of the combustion chamber, the fuel distribution in the combustion chamber is good, and the spray itself is also Since the nozzle diameter is narrowed, a spray with good air introduction is formed, and combustion with high air utilization and fuel efficiency is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a conventional side-injection diesel engine, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. 3 is a front end portion of the fuel valve of FIG. FIG. 4 is an explanatory view showing a tip portion of a fuel valve of one embodiment according to the present invention, and FIG. 5 is an illustration showing a combination of two adjacent sprays when the fuel valve according to the present invention is used. Figures and 6 are views taken in the direction of arrow VI in Fig. 4, Fig. 7 is a view taken in the direction of arrow VII of Fig. 4, and Fig. 8 is a diagram showing the effect of S / d on increasing the reach of coalescence. FIG. 9 is a diagram showing the effect of α and β on the reaching distance of coalescence, and FIG. 10 is an explanatory diagram showing the fuel dispersion state in the combustion chamber when the fuel valve of the embodiment according to the present invention is used. 12 ...... combustion chamber, 13 ...... fuel valve, 14-17 ...... fuel _spray, N 1 to N ₄ ...... injection port.

Claims (1)

[Claims] 1. A combustion apparatus for a diesel engine, comprising a plurality of fuel valves each having a plurality of nozzles in the periphery of a combustion chamber of a cylinder head, and forming an air vortex in the combustion chamber. Out of the individual nozzles, two adjacent nozzles are each set as a group of nozzles, and a plurality of nozzles forming a spray inside the center of the combustion chamber and a spray outside the periphery of the combustion chamber. In each of the nozzle groups such as a plurality of nozzle groups that form a nozzle, the nozzle diameter d and the nozzle spacing S of the adjacent nozzles are
And S / d <5, and the angle α formed by the axis of each nozzle in the projection of the adjacent nozzles on the horizontal plane and the angle β formed by the axis of each nozzle in the projection on the vertical plane are The nozzles are formed so that -9 ° <α11 ° and -9 ° <β <11 °, respectively, assuming that the axial center line approaches as they move away from the nozzle, and the formed inner spray group and outer spray are formed. The groups are respectively combined, and the combined spray group develops as one spray, and when the number of injection holes is a positive integer by the above combination, when the number is 2n, n sprays are formed as a whole and 2n + 1. A combustion device for a diesel engine, characterized in that, in the case of one piece, n + 1 sprays are formed as a whole.