KR100335666B1 - A fuel injector for a large two - stroke internal combustion engine - Google Patents

Abstract

The fuel injector 1 for the large two-stroke internal combustion engine has an elongated outer housing 2 mounted in the water-cooled cylinder cover 51. The fuel injector opening and closing main valve seat 18 is located in the upper cooled valve portion 1a, while the second closing member 32 for fuel flow to the nozzle hole 24 is not cooled. It is located in the nozzle 4 in the part 1b. The nozzle bore includes an upper bore portion 22 having a larger diameter than the lower bore portion 29 having a nozzle hole. When the valve slide 15 is in the closed position, the second closing member is located in the region 23 with the tapered diameter. On the one hand, when the valve is closed, the closing member blocks most of the fuel volume in the nozzle bore from the nozzle bore, on the other hand, the valve slide ends at a distance from the nozzle bore so that the lower portion 30 of the slide It does not disturb atomization when the injector is opened.

Description

FUEL INJECTOR FOR A LARGE TWO-STROKE INTERNAL COMBUSTION ENGINE}

The present invention relates to a fuel injector for a large two-stroke internal combustion engine, such as a marine propulsion diesel engine, wherein the valve has at least a fuel nozzle with a cooled valve portion at the top and a transverse nozzle hole extending from a central longitudinal nozzle bore. With an elongated outer housing mounted to the water-cooled cylinder cover in a manner with a lower substantially uncooled valve portion including a lower portion of the valve slide, the valve slide is adapted to open and close for fuel injection and is located within the cooled valve portion. It has an upper portion for supporting the movable valve portion for the valve seat and a thin lower portion extending into the nozzle bore and supporting a second closure member for fuel flow to the nozzle aperture and positioned in the lower valve portion.

Fuel injectors for four-stroke engines are known, in which the main valve seat is located directly above the nozzle hole, for example disclosed in EP-A-0 451 408. Here the front part of the injector with the valve seat is cooled by the coolant in the cylinder cover because the cylinder cover has a small thickness and the injector housing is very short so that only the cooling effect is directed towards the tip of the injector. As a result of the cooling, the nozzle and valve seat may be made of tempered steel.

In large two-stroke engines, the cylinder cover is so thick that the lower valve section of the injector extends downwardly from the adjacent surface of the injector toward the nozzle bore against the cooling cylinder cover, so the lower section is not sufficiently cooled and is driven by the combustion gas of the engine. Heated to high temperature. Compared to medium speed and high speed engines fueled by diesel oil, the temperature level is further increased in large two-stroke internal combustion engines fueled by heavy fuel oil preheated to approximately 150 ° C. As is known, the temperature level in the protruding portion of the fuel nozzle can be achieved between 500 and 600 ° C. by the injector in such engines. Since the high temperature in the lower valve section leads to a functional failure in the main valve sheet, for example due to coking or corrosion of the material, the main valve sheet in such an injector should be located in the upper cooled valve section. . As a result, the flow path between the main valve seat and the nozzle hole is long and has a large volume, which is typically on the order of 2-3 percent of the fuel volume injected during the engine cycle.

When the main valve seat is closed at the end of fuel injection, the amount of fuel in the path between the valve seat and the nozzle hole is cut off from the supply pressure of the fuel. This amount of fuel can seep out or overflow through the nozzle bore in the period when the injector is basically closed. This residual amount of fuel is not atomized in the combustion chamber so only some fuel combustion or noncombustion is achieved. Unburned fuel leads to coking of the combustion chamber and downstream engine components, leading to the release of fuel that is harmful to the environment with the exhaust gases, and also naturally increases fuel consumption.

Most of these disadvantages also remain in the fuel injectors disclosed in WO 93/07386, the type mentioned at the outset. The valve slide here retains a ring-shaped second closure member, in which the ring extends past the nozzle hole to block it, thereby blocking the amount of oil in the path below the main valve seat by closing the nozzle when the injector is closed. Prevents flow through holes. In the opening movement of the injector, the nozzle hole is not covered by the ring sliding upward in the nozzle bore. The central nozzle bore has a constant diameter to allow the sliding ring to be inserted and displaced into the bore.

In practice, it has been demonstrated that injectors with a second closure member contain higher fuel consumption, especially at high loads of the engine. This is probably due to changed injection conditions when the injector is opened and the oil is atomized into the combustion chamber.

It is an object of the present invention to provide fuel injectors that, despite the relatively high temperature levels in the area near the nozzle apertures, can limit the ejection of fuel when the injector is closed and provide relatively good injection and distribution of fuel when the injector is opened. To provide.

For this purpose, the fuel injector according to the invention has a downwardly decreasing diameter area in which the nozzle bore is located in the valve section, the nozzle hole extending from the smaller diameter bore portion and the lower portion of the valve slide. Ended at a height above this best nozzle hole, the second closure member is characterized by being located in the region for the closing diameter of the bore when the slide is in the closed position.

It has surprisingly been found that the fuel injector according to the invention achieves the above object. The second closing member suppresses the amount of upstream fuel penetrating into the nozzle hole when the injector is closed. The reduction in fuel consumption when the injector is opened may be explained by the fact that the bore portion leading to the nozzle hole advantageously has a small diameter, which provides uniform flow conditions for the nozzle hole. Since the valve slide in all positions ends at the upper height of the nozzle hole, it is assumed that the fuel flow to these holes is only slightly affected by the presence of the second closing member.

In the closed position of the valve, the main valve seat prevents fuel pressure on the pump side from affecting the area around the second closing member. There is therefore no appreciable pressure drop across the closure member, which includes the freedom to design the closure member in such a way that only the closure member in the closed position affects only the material of the fuel nozzle with extremely small force.

The end of the valve slide away from the top nozzle also has the advantage that the slide tip is not affected by the force of corrosion occurring around the nozzle hole when the valve is opened.

In a preferred embodiment, the second closure member has a cylindrical portion, which can slide to seal into the portion with the smaller diameter of the nozzle bore. As the slide moves downward toward the closed position, the cylindrical portion is spaced apart by the narrower lower portion of the nozzle bore, thereby preventing the flow connection between the nozzle hole and the wider upstream portion of the nozzle bore. The cylindrical part only affects the nozzle itself with small frictional forces that occur as the surfaces slide past each other. In the closed position of the injector, the cylindrical portion is received inside the lower portion of the nozzle bore without the nozzle being affected by the original closing force.

In an embodiment where the manufacture is particularly simple, the thin lower portion of the valve slide with the second closure member is a rigid extension of the slide upper portion. The rigidity of the thin portion allows the tip of the slide to remain coaxial with the upper portion of the slide so that it is also coaxial with the nozzle bore.

In another embodiment, the thin lower portion of the valve slide is a flexible extension transverse to the valve slide upper portion, the lower portion having a guide at a height above the second closure member which is a wall of the bore portion having a larger diameter. The center of gravity of the closing member in the nozzle is brought into contact with. Separate guides that center the slide tip are, of course, more difficult to manufacture than the cylindrical smooth bottom part, but instead the tip of the slide centers itself on the nozzle bore, so the lower part of the slide is aligned with the upper part. There is no need to be. This substantially facilitates mounting the slide to the injector and ensures good centering of the slide tip even after prolonged operation. Self-aligning slide tips are particularly advantageous when the lower part of the slide is a separate replaceable unit.

Preferably, the guide is designed as several longitudinal fins extending radially from the lower part of the slide, with the upper and lower ends of the pins preferably being pointed. The longitudinal pins only slightly disturb the downward flow of fuel when the injector is opened. The disturbance of the flow can be further reduced by sharpening the ends of the fins, so that the flow achieves a smooth flow from the fins. In view of the best possible flow conditions in the lower part of the nozzle, the lower free end of the slide may be appropriately conical, thus filling the entire bore cross section from the flow of fuel around the slide in the path of the second closure member. So many vortices do not begin when they are changed.

In particular, if the fuel is in the gaseous state, it may be appropriate to design the injector such that in the closed position the second closure member is adjacent to the inclined surface in the bore region with reduced diameter, which closure member is replaceable in the longitudinal direction of the slide. And designed to be loaded with a spring to move away from the upper portion of the slide. The inclined surface acts as a valve sheet, but as a result of the substitution of the second closure member with respect to the upper portion of the slide, the closure member can be pressed against the sheet beyond the force generated by the associated spring. The force of the spring is suitable for the material strength in the nozzle. That is, for example, the force of the spring can be chosen small so that the closure member does not apply most load on the sheet material.

Preferably, the thin portion under the valve slide with the second closure member is a separate unit, which is removably fixed to the upper portion. This makes it possible to replace the second closure member independently of the upper portion of the slide and furthermore if the closure member needs to be a material that is more temperature resistant than the upper portion of the slide, the two parts can be made separately In other words, manufacturing advantages are obtained in that they can be manufactured as individual materials.

In order to obtain the maximum possible loss of oil loss during the period when the injector is closed, the area of the nozzle bore with a reduced diameter is preferably substantially closer to the nozzle hole than to the main valve seat. This limits the volume of the nozzle bore below the second closure member.

In order to achieve good onset of fuel atomization when the injector is opened, the second closing member only opens a portion of the nozzle bore having a small diameter when the movable valve portion of the slide has moved a certain distance away from the main valve seat. The injector can be designed appropriately. Thus, before the closing member is opened for the passage of fuel to the bore leading to the nozzle hole, the pressure of the fuel in the nozzle bore having a larger diameter can be raised to an appropriately high pressure. Thus, when fuel begins to be discharged through the nozzle hole, this occurs at a higher pressure, which promotes atomization. The delay in opening of the closure member may in one embodiment be adjusted through the length of the cylindrical portion that can slide to seal into the nozzle bore, in another embodiment the delay may be adjusted by the position of the stop, This pulls the replaceable closure member along the movement of the slide.

Embodiments of the present invention will be described in more detail later with reference to the schematic drawings.

1 is a longitudinal sectional view of the first embodiment of a fuel injector;

2 and 3 are enlarged cross-sectional views of the lower part in the open and closed positions for the second embodiment of the injector.

4 and 5 show corresponding partial cross-sectional views of a third embodiment mounted in a cylinder cover.

6 and 7 show corresponding partial cross-sectional views of a fourth embodiment.

FIG. 1 shows a fuel injector or fuel valve, which is indicated as reference numeral 1 as a whole with the upper flange 2 securing the injector in the engine. The flange has an upper connection portion 3, on which a pressure pipe, not shown, can be fixed, and pressurized fuel is supplied from a suitable fuel source, such as a fuel pump or a high pressure reservoir.

The injector has a nozzle 4 at the bottom. Fuel can be passed through the upper flow path 5 from the connection in the connection part 3 towards the nozzle 4, which spring guide 7 and the circulation slide 8 from the central bore 6 of the connection part. Is passed toward the pressure chamber 9, which is limited by the slide 8 and the slide guide 10. On the lower side of the sheet 11, the fuel can flow further toward the nozzle through the intermediate flow path 13 in the form of a central bore in the pressure pipe 13, the pressure portion 14 and the valve slide 15, The central bore here is connected to the main pressure chamber 16 via several inclined bores 17. The intermediate flow path ends downward in the main valve seat 18. In this injector open position below the valve seat, the fuel is directed to the lower flow path 19 in the form of a central bore 20 at the bottom of the slide guide 21 for the valve slide 15 and to a nozzle bore coaxial with it. Flows forward through it (see FIG. 2).

The central longitudinal nozzle bore includes an upper bore portion 22 with a larger diameter, which merges into the lower bore portion with a smaller diameter through the region 23 with a reduced diameter, from which the nozzle hole 24 ) Extends as shown in subsequent figures.

When the injector is in the closed position as shown in FIG. 1, the upper flow path 5 is connected through an unshown lateral path in the spring guide 7 with voids, the voids being wrapped by The preheated fuel can be circulated in the upper part of the injector in a known manner. As noted here, the injector of FIG. 1 is intended for the injection of oil, in particular for heavy fuel oil injection. When fuel injection is initiated, the oil pressure in the upper fuel flow path 5 and the pressure chamber 9 is increased so that the circulation slide 8 moves upward and blocks the transverse circulation path. At the same time, the flow path through the sheet 11 is opened and the pressure diffuses downward into the main pressure chamber 16 through the intermediate flow path 12 and the inclined bore 17. The compression spring 25 is retained on the upper spring disk 27 and pushed downwards through the lower spring disk 27 on the valve slide 15 to form an annular conical surface on the valve slide and the main valve seat 18. The valve portion 28, which is movable relative to, is pressed against the valve seat 18.

When the oil pressure in the main pressure chamber 16 reaches the valve opening pressure determined by the pre-loading of the compression spring 25, the valve slide 15 moves downward while at the same time the oil It begins to flow past the sheet 18.

The movable valve portion 28 restricts the upper portion of the valve slide 15 from the thin lower portion 30 of the slide. In the embodiment shown in FIG. 1, the lower portion 30 is cylindrical and has a diameter slightly smaller than the diameter of the nozzle bore portion 29 having a smaller diameter, so that the lower portion 30 of the slide has a lower bore. It may slide to seal into portion 29. Since the lower part 30 protrudes a certain distance into the bore part 29 when the injector is closed, the valve in the upper bore part 22 before the lower part 30 of the slide is lifted out of the bore part 29. By opening the pressure is increased, thereby opening for the oil flow to the nozzle hole. The pressure build up in the oil prior to the final path to the nozzle hole promotes fine atomization of the oil at the onset of atomization.

A nozzle hole, not shown in FIG. 1, is located at the end of the bore portion 29, ie several bore diameters are spaced apart from the lower cone tip of the valve slide 15 when the slide is in the closed position as shown. . The lower portion 30 of the valve slide has a substantially constant diameter, but only requires precise machining on the bottom portion, which acts as the closing member 32 and slides into the lower portion 29 of the nozzle bore.

In the first embodiment shown in FIG. 1, the lower portion 30 of the valve slide 15 is formed integrally with the upper portion of the valve slide as its rigid extension, thereby guiding the slide portion of the upper slide. Without positioning other than within 21, the lower portion 30 is centered with respect to the nozzle bore.

In the mounting position of the injector, the adjacent surface 31 at the front end of the injector housing 2a is clamped against the conical surface facing upward on the cylinder cover of the engine. This adjacent surface is at the lowest position where the injector is exposed to a substantial cooling effect since the cover is cooled by coolant that circulates in the engine and maintains the temperature of the cover at, for example, 80 ° C. at the adjacent surface 31. to be. On top of the conical contiguous surface 31, the temperature of the injector generally corresponds to the temperature of the oil circulating in the injector and can be preheated, for example to 120-150 ° C. At least in its lowest part, the nozzle section located below the inclined adjacent surface 31 is in contact with the high temperature in the cylinder combustion chamber. Thus, the bottom portion of the nozzle is not substantially cooled. Next, as a whole, the valve 1 has an upper cooling valve portion 1a positioned above the adjacent surface 31 and substantially cooling extending upwardly from the lower end of the nozzle 4 to the adjacent surface 31. It can be said that it is divided into the lower valve part 1b which is not.

The nozzle 4 is a high temperature resistant material, which may also counteract the corrosive effects of the fuel in the region around the nozzle aperture. Since the tempered steel cannot withstand the high temperature levels in the uncooled valve section 1b, the nozzles can be made of, for example, the Inconell alloy ma 758 or Stellite 6 (Stellite 6) described in EP-AO 569 655. It is made from other high temperature resistant alloys such as 6).

It can be seen that the main valve seat is located in the cooled valve portion, while the closing member 32 and the upper portions of the bore portion 29 are located in the uncooled valve portion 1b. As the closure member 32 generally does not affect the material of the nozzle with the force acting in the longitudinal direction, both the closure member and the nozzle have a long service life despite the high temperature level.

In the following description of another embodiment, the same reference numerals as above are used for elements having the same function.

The second embodiment of the fuel injector shown in FIGS. 2 and 3 is also intended for engines using oil as fuel. The thin lower portion 30 of the valve slide is a separate replaceable unit here, which is the center at the bottom of the upper portion of the valve slide until the collar 41 on the lower portion 30 abuts the end surface of the upper portion. It has an outer helix screwed to an inner helix in the bore 40 at its upper end. Locking pins 45 inserted in aligned bores in the upper and lower portions of the slide lock the lower portion 30 against rotation against the upper portion of the slide. If the lower slide portion 30 is worn or damaged, the locking pin 45 can be removed and the lower portion 30 can be replaced by three. This makes it possible to avoid replacing the entire slide.

The lower portion 30 is stretched transversely with respect to the upper portion of the valve slide and is thin and flexible. When the slide is in the closed position shown in FIG. 3, the closing member 32 formed by the front cylindrical portion of the portion 30 protrudes into the bore portion 29 and the oil in the upper bore portion 22 is nozzled. Prevents penetration into the hole 24. The amount of oil in the bore portion 29 below the tip of the valve slide amounts to about 10 percent of the total amount of oil under the main valve seat 18.

The closure member 32 is centered in the nozzle bore by the guide 42, which slides along the guide surface 43 in the nozzle bore. The guides 42 are several, for example four, radially extending longitudinal pins, the upper and lower ends of which are pointed. The oil may flow past the guide 42 through the longitudinal space between the pins.

In FIG. 2, the valve slide 15 is shown in its fully open position, the oil flows past the main valve seat 18 into the nozzle bore and the oil in the region 23 with decreasing diameter It flows past the conical free end 44 of the valve slide and flows downward into the nozzle hole 24 as a joint flow covering the entire cross section of the nozzle bore. The distance between the free end 44 of the slide and the nozzle hole will probably be wide enough that the downward oil flow into the nozzle will not be substantially disturbed by the fact that the lower portion 30 of the slide extends into the nozzle bore.

The number of nozzle holes 24 at the tip of the nozzle depends on the power produced by the working cylinder of the engine and the number of injectors per cylinder. For example, by having four or five nozzle holes all open on the same side of the nozzle, the longitudinal axes of the two outermost nozzle holes form a common angle of less than 100 °, often only 80 ° or less To form an angle. The oil is thus atomized with a scalloped mist of finely distributed oil particles.

The injector for gasified fuel injection will now be described. In principle, the fact that the valve slide is lifted by the adjusting oil affecting the piston region suitable for the purpose on the slide, and the inclined conduit in the inlet conduit 50 and the valve housing 33 in the cover indicated by reference numeral 51. The injector is constructed in the same manner as described above, except that the gas is laterally fed into the lower portion of the valve housing through 52.

The inclined conduit 52 is opened into the pressure chamber 53, which is located directly on top of the main valve seat 18. Modes of operation and configurations of such gas injectors are known in the art. The injector must inject a relatively large volume of gas during the engine cycle. The flow path in the injector should therefore have a moderately large cross-sectional area, which means that the nozzle bore and, therefore, the nozzle itself also have a large diameter. Thus an adjacent surface 31 ′ of the injector pressed against the cooling cone surface on the cover 51 is formed above the nozzle 4 itself, so that the outer diameter of the injector housing can be kept moderately small. Otherwise the cover has a cooling channel 55 near the surface 54 as shown in FIG. 4. The portion of the nozzle located below the adjacent surface 31 ′ is affected by very high temperatures in the combustion chamber 56 and is substantially uncooled.

As the gas flows substantially easier than oil, the nozzle bore has a substantially larger diameter than in this embodiment, and the closure member on the lower portion of the valve slide has a conical inclined surface 57 in the bore region having a decreasing diameter. Contact with The closing member may be a valve needle 58 as shown in FIGS. 4 and 5, or may be a ball member 59 in the form of a ball as shown in FIGS. 6 and 7.

The closing member is not pressed against the inclined surface 57 with a valve closing force of the same magnitude as the closing force acting on the main valve seat 18, but is biased only towards the closed position by a weak compression spring. This may be, for example, a compression spring 61 received in the air gap in the upper portion of the valve slide to press the entire lower slide portion 30 and replaceably located in the central bore in the upper portion, or the lower slide portion 30 ) And a compression spring 60 acting on the valve portion 59 which is replaceably located in the longitudinal direction on the lower portion 30 (see FIGS. 6 and 7).

The displaceably positioned slide portion 30 shown in FIGS. 4 and 5 supports one part of the bayonet coupling, which is for example protruding pins at several upper ends. These pins may pass through corresponding grooves at the ends of the upper portion of the valve slide. As the pin passes through the air gap, the lower part can be rotated to its mounting position, where it contacts the bottom of the air gap, so that the bottom side of the pin is in downward displacement of the part 30 with respect to the upper part of the valve slide. Act as a stop for the

The valve part 59 shown in FIGS. 6 and 7 is restricted so as not to be displaced away from the upper part of the valve slide by a stop in the form of a collar 62, the color being the slide part 30. Capture the thick lower part of the.

It will be apparent that the components from the various embodiments described above can be combined in new embodiments in different ways.

In the embodiment shown in the figure, the second closure member is in a closed position located at the ceiling height of the combustion chamber.

Claims (10)

The valve 1 is not cooled at the bottom, including at least the lower portion of the fuel nozzle 4 with the cooled valve portion 1a at the top and the lateral nozzle holes 24 extending from the central longitudinal nozzle bore. With an elongated outer housing 33 mounted to the water-cooled cylinder cover 51 in such a way that there is no valve portion 1b, the valve slide 15 is adapted to open and close for fuel injection and is located within the cooled valve portion. An upper portion supporting the movable valve portion 28 for the valve seat 18 and a lower valve portion extending into the nozzle bores 22, 23 and 29 and supporting a second closure member for fuel flow to the nozzle aperture In a large two-stroke internal combustion engine fuel injector 1, such as a diesel engine for ship propulsion, having a thin lower portion 30 located therein, the nozzle bore has a downwardly decreasing diameter located in the lower valve portion 1b. Having a region 24, the nozzle hole 24 extends from a bore portion 29 having a smaller diameter, the lower portion 30 of the valve slide ends at a height above the upper nozzle hole, and the second closure member. (32,58,59) are fuel injectors (1) for large two-stroke internal combustion engines, characterized in that they are located in the region (23) for the decreasing diameter of the bore when the slide (15) is in the closed position. 2. The fuel injector of claim 1, wherein the second closure member has a cylindrical portion that can be sealed to slide into a portion of the nozzle bore having a smaller diameter. 2. The fuel injector of claim 1, wherein the thin lower portion (30) of the valve slide with the second closure member is a rigid extension of the upper portion. 2. The thin lower portion 30 of the valve slide is a transversely flexible extension of the upper portion and at a height above the second closure member 32, the lower portion has a guide 42, which is A fuel injector, characterized in that the closing member is centered in the nozzle bore by contacting a wall of a portion 22 of the bore having a larger diameter. 5. The fuel injector according to claim 4, wherein the guide 42 has a plurality of radially extending longitudinal pins on the lower portion 30 of the slide, the upper and lower ends of which are pointed. . 2. The closing member 58 according to claim 1, wherein in the closed position, the second closure members 58, 59 abut the inclined surface 57 in the area 23 of the bore with decreasing diameter, said closure member in the longitudinal direction of the slide. A fuel injector, characterized in that it is spaced apart and subjected to a load of a spring for a movement away from the top of the slide 15. The lower part 30 of the valve slide with the second closing members 32, 58, 59 is a separate unit, which is removably fixed to the upper part. Fuel injector, characterized in that. The fuel injector according to claim 1, wherein the area (23) of the nozzle bore with decreasing diameter is closer to the nozzle hole (24) than the main valve seat (18). 7. The portion of the nozzle bore according to any one of claims 1 to 6, wherein the second closing member has a small diameter when the movable valve portion 28 of the slide moves a predetermined distance away from the main valve seat 18. A fuel injector, characterized in that only 29 is opened. The fuel injector according to claim 1, wherein the lower free ends (44,58) of the slides are conical.