KR101264814B1 - A fuel injection nozzle - Google Patents

Abstract

The fuel injection nozzle for an internal combustion engine comprises a nozzle body (2), nozzle head (3), and a nozzle needle (7) inside the body and interacting with a valve seat (8) by its end. The nozzle body has a longitudinal bore (32) extending from the valve seat through the nozzle head. The ratio of the length (L) of the longitudinal bore and its flow diameter comes to at least 17, preferably at least 20, and especially more than 22. An independent claim is included for a diesel engine, especially a two-stroke large diesel engine, equipped with the proposed fuel injection nozzle.

Description

Fuel injection nozzle {A FUEL INJECTION NOZZLE}

1 is a diagram of an essential part of an embodiment of a fuel injection nozzle with a nozzle head in accordance with one embodiment of the present invention.

2 is a view of the lower portion of the nozzle head.

3 is a view of a nozzle head of the second embodiment.

4 is an enlarged view of a lower region of the nozzle head shown in FIG. 3.

5 is a view of a nozzle head of the third embodiment.

The present invention relates to fuel injection nozzles for combustion engines, in particular large diesel engines, according to the preamble of the claims.

Large diesel engines, for example large diesel engines operating according to the two-stroke method, are used as drive aggregates in ships or stationary installations. Fuel injection nozzles with a nozzle body and a nozzle head are generally used for this kind of diesel engine. Generally, the nozzle head is provided with a plurality of nozzle holes, by which fuel is injected into the combustion chamber. In order to start or end the injection process, a movable nozzle needle is provided which cooperates with the valve seat to open and close a passage through the nozzle hole to the fuel injection nozzle.

In general, nozzle heads are parts that are prone to wear because they are collectively subjected to high thermal, mechanical and chemical loads. The mechanical load relates to high injection pressures, which can in particular be 1000 bar or more. Thermal loads are caused by the high temperatures in the combustion chamber and by the enormous temperature difference between the combustion temperature and the newly supplied scavenging air temperature, while chemical loads are mainly due to high temperature corrosion or thermal corrosion.

For this reason, in particular because of the heat load, the valve seats are usually arranged at a suitable distance from the nozzle holes so that they do not receive excessive combustion heat.

If the valve seat and the nozzle hole are spaced apart from each other, there are the following problems. At the end of fuel injection, the nozzle needle is squeezed into the valve seat so that fuel located downstream of the valve seat, ie between the valve seat and the nozzle hole, is not loaded at the supply pressure. After the end of the injection, the fuel remaining in the nozzle head is injected into the combustion chamber in a spray state through the nozzle hole, and only slightly burned or not burned in the combustion chamber at all. This generates additional exhaust gas pollution, in particular smoke, and in some cases unburned fuel is deposited on all parts of the combustion chamber and the components carrying the exhaust gas.

In view of the above problems, it is an object of the present invention to provide a fuel injection nozzle having a nozzle head capable of keeping a small amount of harmful exhaust gas discharged without impairing operability and reliability.

The subject matter of the present invention meeting the above object is characterized by the features of the claims.

Therefore, in the present invention, the nozzle body includes a nozzle body and a nozzle head connected to the nozzle body, and a nozzle needle is disposed inside the nozzle body, and the end of the nozzle needle cooperates with the valve seat, in the open position, the nozzle needle Open the fuel passage of the valve seat, and in the closed position, close the passage having a longitudinal bore passing through the nozzle head from the valve seat and having a flow diameter, the nozzle needle being at least one starting from the longitudinal bore; There is provided a fuel injection nozzle for a combustion engine, in particular a large diesel engine, having a nozzle hole, through which the fuel can be injected into the combustion chamber of the combustion engine. The ratio between the length of the longitudinal bores to the flow diameter of the longitudinal bores is at least 17, preferably at least 20, particularly preferably at least 22.

Due to the fuel injection nozzle and nozzle head having such a structure, the volume between the valve seat and the nozzle hole-the blind hole-can be significantly reduced in comparison with the conventional nozzle head. The volume can be reduced by 50% or more by significantly reducing the ratio of length to flow diameter of the longitudinal bore of the nozzle head. Thus, after the injection process, only a very small amount of fuel remains in the nozzle head, so that the negative consequences of this fuel-particularly harmful emissions, are significantly reduced.

In a preferred embodiment, the sum of the nozzle holes forms the total flow diameter for the fuel, and the flow diameter of the longitudinal bores is preferably no more than two times, at least 0.5-1.5 times the flow diameter of all the nozzle holes.

The longitudinal bore preferably has an extension in the nozzle hole area. The local extension has two advantages. If there is a certain number of nozzle holes, the distance between the individual openings of the nozzle holes into the longitudinal bore can be chosen to be larger, thereby reducing the peak mechanical pressure of the workpiece of the nozzle head due to internal pressure. In addition, the local extension easily deflects the fuel flow flowing from the longitudinal bore into the nozzle hole, thereby reducing fluid friction losses when flowing into the nozzle hole.

It may be desirable to form the extension asymmetrically with respect to the longitudinal axis of the longitudinal bore. This is simpler to understand in terms of manufacturing technology. In addition, the wall thickness of the nozzle head can make the area without the nozzle hole thinner than the area where the nozzle hole is provided. This has the advantage that the nozzle holes do not become too long and thus prevent the fuel injection from being concentrated very strongly.

It may also be desirable to form the longitudinal bores asymmetrically extending obliquely with respect to the longitudinal axis of the nozzle head.

Each nozzle hole is preferably engaged with the longitudinal bore at an angle of at least 90 degrees, which means that the nozzle hole extends obliquely from the longitudinal bore downwardly in the built-in state. The method simplifies the return of fuel flow and thus reduces fluid friction losses.

A more preferred method of reducing frictional losses is in each case circular the transition region between the longitudinal bore and the nozzle hole.

In terms of flow technology, it has been found that the passage of the valve seat in the open position of the nozzle needle preferably has an area at least as large as the size of the flow cross section of the longitudinal bore.

Since the nozzle head is generally a wearable part, the fuel injection nozzle preferably has a structure in which the nozzle head is removably connected to the nozzle body.

The fuel injection nozzles according to the invention are particularly suitable for diesel motors, in particular two-stroke large diesel engines.

Other preferred methods and embodiments of the invention are disclosed in the dependent claims.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

For the understanding of the present invention, FIG. 1 is a longitudinal sectional view showing the main part of the embodiment of the fuel injection nozzle according to the present invention with reference numeral 1. Essential members of known types of fuel injection nozzles have been omitted for clarity. 1 shows a fuel injection nozzle embedded in a cylinder head 10 of a two-stroke large diesel engine, for example a motor of a ship. According to the figure, the lower end of the fuel injection nozzle extends embedded in the combustion chamber 20 of the cylinder of the diesel engine.

Relative positional relationships such as "upper, lower, up, down ..." always refer to the positions illustrated in the drawings and should be understood as examples only, and not as restrictive terms.

The fuel injection nozzle 1 comprises a nozzle body 2 and a nozzle head 3 connected to the nozzle body 2. In the above-described embodiment, its lower end is connected by a tapered holding sleeve 4 towards the longitudinal axis A of the fuel injection nozzle 1. The longitudinal axis A is identical to the longitudinal axis A of the nozzle head 3. The holding sleeve 4 is attached to the nozzle body 2 by means of a sleeve nut 5 and a flexible member 45, for example a circlip. The nozzle head 3 is supported in the tapered portion of the holding sleeve 4.

The nozzle head 3 has a longitudinal bore 32 and at least one nozzle hole in the lower end region of the nozzle head, starting from the longitudinal bore 32 and through which fuel can flow into the combustion chamber 20 ( 31) generally have five nozzle holes, for example.

2 is a view of the lower end of the nozzle head 3 in which five nozzle holes 31 are arranged. The nozzle holes 31 extend downward from the longitudinal bore 32 in the direction of the combustion chamber 20, that is, each nozzle hole 31 has an angle α of 90 ° or more (see FIG. 1). Furnace into the longitudinal bore 32.

A pressure space 6 is provided inside the nozzle body 2, and the fuel supply line 12 is opened into the pressure space. The pressure space 6 is bounded axially by the valve seat 8. Inside the nozzle body 2, a nozzle needle 7 is also arranged which naturally extends in the direction of the longitudinal axis A and cooperates with the valve seat 8. In the closed position shown in FIG. 1, the lower tip of the nozzle needle 7 enters the valve seat 8 such that the passage leading from the pressure space 6 into the adjacent longitudinal bore 32 is closed. Squeezed. The nozzle needle 7 is spring loaded in a known manner by a pressure spring, not illustrated, and is pressed against the valve seat 8. In the open position of the nozzle needle 7, the nozzle needle is lifted from the valve seat 8 so that the passage between the lower end of the nozzle needle 7 and the valve seat 8 is opened, through which fuel is forced into the pressure space ( From 6) into the longitudinal bore 32.

As illustrated in FIG. 1, the length L of the longitudinal bore 32 is the bottom end and the longitudinal bore illustrated by the surface of the valve seat 8 contacted by the nozzle needle 7 in the closed position. The distance between the bottom end of (L), that is, the end of the combustion chamber.

The volume between the valve seat 8 and the nozzle hole 31 is generally referred to as a blind hole.

The longitudinal bore 32 of the above-described embodiment has a structure which is a substantially cylindrical bore extending in the direction of the longitudinal axis A. FIG. The diameter D of the longitudinal bore 32 defines the flow diameter, ie the flow cross section, which means the cross section in the longitudinal bore 32 that can be used for fuel flow. In the case where the longitudinal bore is not a cylindrical structure but is a conical, for example, of varying diameter, the expression "flow cross section of the longitudinal bore, ie flow diameter" means a minimum flow cross section, ie flow diameter.

The individual nozzle holes 31 also have the structure of cylindrical bores in each case. The diameter b in each case (see FIG. 2) defines the flow cross section for the different nozzle holes 31. The diameter b of the individual nozzle holes 31 may vary from the nozzle hole to the nozzle hole, or the diameter b may be the same or part of the nozzle hole 31. The flow cross section defined in each case by the individual nozzle holes 31 is added to the entire flow cross section of the nozzle holes. Thus, all of the nozzle holes, here the sum of the five flow cross sections, means the total flow cross section of the nozzle hole 3, ie the total flow cross section through which fuel can flow from the longitudinal bore 32 into the combustion chamber 20. This applies similarly to the total flow diameter of the nozzle hole 31.

According to the invention the fuel injection nozzle 1 or the nozzle head 3 has a structure such that the ratio of the length L of the longitudinal bores 32 to the flow diameter of the longitudinal bores is equal to or greater than 17, and the ratio is at least 20 or more are preferable and 22 or more are especially preferable.

Through this method the volume of the blind hole, ie downstream of the valve seat 8 and upstream of the nozzle hole 31, is reduced, for example by 50% or more, compared with the known embodiment. By this reduction, when the nozzle needle 7 is sealed crimped back into the valve seat 8 after the injection process is finished, there is only a relatively small amount of fuel downstream of the valve seat since the blind hole is significantly smaller. . In addition, the emission of harmful substances by fuel from the blind holes is very significantly reduced after the end of the injection process in the combustion chamber and the exhaust component.

The ratio of the length L to the flow diameter of the longitudinal bore 32 above at least 17, preferably at least 20, particularly preferably at least 22, does not significantly degrade the hydrodynamic characteristics or the nozzle head 3 The volume of the blind hole is preferably reduced without excessively dropping the pressure across the).

In certain embodiments the length L of the longitudinal bores is, for example, about 48.1 mm for a diameter of about 2.1 mm or about 70.7 mm for a diameter of about 2.9 mm.

In the structure of the nozzle head 3, the flow diameter of the longitudinal bore 32 is preferably not more than twice the total flow diameter of the nozzle head 31. In practice, the flow diameter of the longitudinal bore 32 has been found to be preferably 0.5 to 1.5 times the total flow diameter of the nozzle head.

In the operating state, the fuel injection nozzle 1 acts as follows. Fuel enters the pressure space 6 through the supply line 12. In order to start the injection, the connection between the common rail store for fuel and the pressure space 6 is opened, for example by a valve, ie the fuel is transferred into the pressure chamber 6 by an injection pump. The nozzle needle 7 is fueled here and the passage to the nozzle head 3 is opened by lifting the needle from the valve seat 8 against the pre-stress of an unillustrated pressure spring. . Fuel passes through the longitudinal bore 32 and then is injected into the combustion chamber 20 through the nozzle head 31. To end the injection, the nozzle needle 7 is pushed back into the valve seat by means of a pressure spring to stop the fuel supply or by closing the connection with the common rail pressure store to reduce the pressure. The passage is closed. Since the volume of the blind holes is significantly reduced, the fuel dripping into the combustion chamber 20 after the passage of the valve seat is closed is significantly reduced.

The friction between the walls of the bore and the fuel is increased by significantly reducing the flow cross section of the longitudinal bore 32 of the nozzle head, which is realized by making the diameter D of the longitudinal bore 32 small, i.e. by reducing the volume of the blind hole. . This corresponds to a greater pressure drop or pressure loss caused by the nozzle head 3. The pressure drop due to friction in the nozzle head according to the invention can reach 50-100 bar sufficiently. In today's large diesel engines operating on the common rail principle, this pressure drop due to friction can be compensated in a simple manner by correspondingly increasing the fuel pressure in the common rail pressure store. Thus, in the lower rotational speed range, sufficient pressure, for example 500-700 bar, is still present in the actual injection of fuel through the nozzle head 31 to ensure trouble free injection into the combustion chamber 20. Is guaranteed.

Alternatively, or in addition, other methods may also be used to compensate at least in part for the increased flow resistance due to the reduced flow cross section, ie the reduced blind hole volume.

Therefore, for example, the cross section of the nozzle hole 31 can be enlarged. It is also desirable for the transition region between the longitudinal bore 32 and the nozzle hole 31 to have a rounded structure in each case, so that fuel can easily flow from the longitudinal bore 32 into the nozzle hole 31. That is, the flow resistance can be reduced due to the rounded shape.

Another highly preferred method is shown for the second embodiment of the nozzle head according to the invention illustrated in FIGS. 3 and 4. In the drawings, the same or equivalent parts in the functional aspects are indicated by the same reference numerals, respectively.

3 is a cross-sectional view of the second embodiment, and FIG. 4 is an enlarged view of the lower region of the nozzle head 3. As shown in FIGS. 3 and 4, the longitudinal bore 32 of the second embodiment has an extension 321 in the region of the nozzle hole 31. In the second embodiment, as illustrated in FIG. 2, five nozzle holes 31 are also provided.

Because of the extension 321, fuel can easily flow from the longitudinal bore 32 into the nozzle hole 31, ie it is simple to deflect the fuel flow from the larger cross section of the extension 321 into the nozzle hole. Therefore, the flow resistance can be minimized. This reduces fluid friction when flowing into the nozzle hole 31.

In addition, the extension has additional advantages. For a predetermined number of nozzle holes 31 having a predetermined diameter and having an open area of a predetermined round shape, the distance between the individual openings of the nozzle holes 31 opening into the longitudinal bore 32 can be made larger. Can be. This greater distance has the advantage of reducing the mechanical stress peaks of the nozzle head material.

Another preferred method is to form the extensions 321 asymmetrically with respect to the longitudinal axis 32, in particular as can be seen in FIG. 4. The longitudinal axis of the longitudinal bore 31 is the same as the longitudinal axis A of the nozzle 3, that is, the longitudinal axis of the fuel injection nozzle 1 in this embodiment. Since the longitudinal axis C of the extension 321 extends parallel to the longitudinal axis A but is offset, the extension 321 is disposed asymmetrically or eccentrically with respect to the longitudinal bore 32.

The method is provided in which the larger wall thickness of the nozzle head 3, defined by the relatively small diameter D of the longitudinal bores 32, faces the combustion chamber 20, ie the nozzle hole 31. It can be reduced by the expansion portion 321 of the side. The fact that the wall thickness is large is desirable in terms of mechanical load, but this also has to make the nozzle hole 31 longer in each case. If the length of the nozzle hole is too long, it may be undesirable because the fuel injection passing through may be strongly concentrated, which may adversely affect the injection process. This strong concentration can be prevented by the extension 321 because the wall thickness of the nozzle head 3 on the side facing the combustion chamber 20 becomes smaller, that is, the nozzle hole 31 becomes smaller. In addition, it is simpler to manufacture the asymmetric structure of the extension 321.

Similar effects can also be achieved using a third embodiment of the nozzle head according to the invention illustrated in FIG. 5. In this embodiment the longitudinal bores 32 extend obliquely with respect to the longitudinal axis of the nozzle head. As shown in FIG. 5, the longitudinal axis A ′ of the longitudinal bore 32 in the figure extends at a nonzero angle β with respect to the longitudinal axis A of the nozzle head 3.

It is obvious that the method described using the three embodiments can also be combined with each other.

In the fuel injection nozzle 1 according to the invention, it is more preferred if the passage of the valve seat 8 has an area as large as the flow cross section of the longitudinal bore 31 in the open position of the nozzle needle. This means that the flow cross section between the nozzle needle and the valve seat 8 in the open position of the nozzle needle 7 is equal to or larger than the flow cross section of the longitudinal bore 32. Since the flow cross section of the longitudinal bore 32 is larger than the total flow cross section of all the nozzle holes 31, the flow cross section no longer increases downstream of the pressure chamber 6 at the position where the nozzle needle 7 is open. Do not. This means that the flow rate of the fuel does not decrease due to the increase in the flow cross section. This is desirable in fuel injection nozzles because it is inefficient to recover the kinetic energy (diffuser efficiency) by widening the flow cross section.

The nozzle head for fuel injection nozzle according to the present invention can be manufactured using all known processing methods. The longitudinal bores 32, the nozzle holes 31, the rounded sections and, if necessary, the extensions 321 may be manufactured by boring and / or electrochemical machining methods, for example electrolytic machining.

Claims (15)

In a fuel injection nozzle for a two-stroke large diesel engine, The nozzle body (2) and A nozzle head 3 connected to the nozzle body 2 Including, The fuel injection nozzle is a nozzle needle (7) located inside the nozzle body (2) With The end of the nozzle needle cooperates with the valve seat 8, in the open position, the nozzle needle 7 opens the fuel passage of the valve seat 8, and in the closed position, closes the passage. , The nozzle needle has a longitudinal bore 32 extending from the valve seat 8 through the nozzle head 3 and having a flow diameter, The nozzle needle also has one or more nozzle holes 31 starting from the longitudinal bore 32 and allowing fuel to be injected into the combustion chamber 20 of the combustion engine, The ratio of the length L of the longitudinal bores 32 to the flow diameter of the longitudinal bores 32 is 17 or more, Fuel injection nozzle. The method of claim 1, The sum of the nozzle holes forms the total flow diameter for the fuel, And said flow diameter of said longitudinal bore (32) is no more than twice the total flow diameter of all said nozzle holes (31). The method according to claim 1 or 2, And the longitudinal bore (32) has a broadened section (321) in the region of the nozzle hole (31). The method of claim 3, The expansion portion (321) is a fuel injection nozzle, characterized in that formed asymmetrically with respect to the longitudinal axis of the longitudinal bore (32). The method of claim 3, Fuel injection nozzle, characterized in that the longitudinal bore (32) extends obliquely with respect to the longitudinal axis (A) of the nozzle head (3). The method according to claim 1 or 2, And each nozzle hole (31) is opened into the longitudinal bore (32) at an angle of at least 90 degrees. The method according to claim 1 or 2, A fuel injection nozzle, characterized in that the transition region between the longitudinal bore (32) and the nozzle hole (31) is rounded. The method according to claim 1 or 2, Fuel injection nozzle, characterized in that in the open position of the nozzle needle, the passage of the valve seat (8) has an area greater than or equal to the flow cross section of the longitudinal bore (32). The method according to claim 1 or 2, A fuel injection nozzle, characterized in that the nozzle head (3) is removably connected to the nozzle body (2). A two-stroke large diesel engine, comprising a fuel injection nozzle (1) according to claim 1. delete The method of claim 1, A fuel injection nozzle, wherein the ratio of the length L of the longitudinal bores to the flow diameter of the longitudinal bores is at least 20. The method of claim 1, A fuel injection nozzle, wherein the ratio of the length L of the longitudinal bores to the flow diameter of the longitudinal bores is at least 22. 3. The method of claim 2, The flow diameter of the longitudinal bore (32) is 0.5 to 1.5 times the total flow diameter of all of the nozzle holes (31). delete

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