A dual-fuel engine fuel injector

Abstract

The present invention relates to an injection nozzle for a dual-fuel engine, which comprises a needle valve body. An oil inlet passage is arranged inside the needle valve body, an oil cavity communicated with the oil inlet passage, and an annular oil passage communicated with the oil cavity. At the bottom of the needle valve body, a first layer of injection holes and a second layer of injection holes with different heights are respectively arranged; a needle valve rod is movably arranged inside the needle valve body, and a boss is arranged thereon. The first layer of injection holes is arranged at the sealed connection between the boss and the inner wall of the annular oil passage. Axially moving the needle valve rod can control the opening or closing of the first layer of injection holes by the boss; thereby controlling the simultaneous opening of the first layer of injection holes and the second layer of injection holes, or separately opening the second layer of injection holes. The present invention adopts a structure of two layers of injection holes in one injection nozzle, and has better load adaptability.

Description

Technical Field

[0001] The present invention relates to the technical field of high-pressure fuel injection for engines, and particularly to an injector for a dual-fuel engine. Background Art

[0002] Energy conservation and emission reduction are the current challenges faced by internal combustion engines. In order to reduce emissions such as nitrogen oxides, particulate matter, and carbon dioxide, new fuels such as natural gas and methanol have begun to be applied on a large scale in the field of internal combustion engines. However, these fuels such as natural gas and methanol are difficult to be directly compression-ignited in diesel engines and basically require diesel for ignition to achieve dual-fuel combustion. In these dual-fuel engines, the amount of pilot diesel required when operating in the dual-fuel mode is very small. In order to achieve stable injection of a small amount of diesel, the diesel nozzles equipped in these dual-fuel engines are often very small and cannot meet the requirements of large diesel injection. Therefore, once the supply of fuels such as natural gas or methanol is insufficient in these dual-fuel engines, they can only operate in the pure diesel mode with a small fuel amount, and the power generated cannot meet the normal power requirements of the equipment.

[0003] To solve the above problems, adding a separate injector for injecting a large amount of fuel on the cylinder head to achieve large-load operation in the pure diesel mode is an optional solution. However, this requires at least two diesel injectors to be arranged on the cylinder head, which is difficult in the limited cylinder head space. At the same time, it also makes the structure of the engine cylinder head more complex, bringing challenges to the engine manufacturing process and the reliability of the structural strength, etc.; in addition, it is very difficult to make the fuel injection directions of the two injectors optimal at the same time, and the engine performance in at least one of the dual-fuel or pure diesel working modes will be greatly affected. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a new type of injector for a dual-fuel engine. This injector can not only inject a small amount of pilot fuel but also inject a large amount of fuel to meet the large-load working mode of pure diesel, and only one diesel injector is used, which can save the cylinder head space of the engine, simplify the engine structure, and save costs.

[0005] To achieve the above object, an injector for a dual-fuel engine provided by the present invention includes a nozzle body and a needle valve rod;

[0006] An oil inlet passage is arranged inside the nozzle body, an oil cavity communicated with the oil inlet passage, and a first layer of injection holes and a second layer of injection holes with different heights are respectively arranged at the bottom of the nozzle body;

[0007] The needle valve rod is movably arranged inside the nozzle body. The outer surface of the upper end of the needle valve rod is hermetically connected with the inner surface of the nozzle body, and an annular oil passage is formed between the lower end of the needle valve rod and the nozzle body. The annular oil passage is communicated with the oil cavity;

[0008] A boss is also provided on the needle valve stem, and the first-layer fuel injection holes are arranged at the sealed connection between the boss and the inner wall of the annular oil passage. The needle valve stem is axially moved to control the opening or closing of the first-layer fuel injection holes by the boss, so as to control the simultaneous opening of the first-layer and second-layer fuel injection holes, or the second-layer fuel injection holes are opened separately.

[0009] Preferably, the boss is circumferentially and sealingly connected to the inner wall of the needle valve body to divide the annular oil passage into an upper oil passage and a lower oil passage; there is also a needle valve oil passage at the position of the boss on the needle valve stem, and the upper oil passage and the lower oil passage are communicated through the needle valve oil passage.

[0010] Preferably, a conical surface is provided at the bottom end of the needle valve stem, a ring groove is provided at the bottom of the needle valve body and is sealingly connected to the conical surface, and a pressure chamber is provided below the ring groove; the second-layer fuel injection holes are arranged in the pressure chamber.

[0011] Preferably, the needle valve oil passage is obliquely arranged inside the needle valve stem.

[0012] Preferably, the aperture of the first-layer fuel injection holes is larger than that of the second-layer fuel injection holes.

[0013] Preferably, the number of both the first-layer fuel injection holes and the second-layer fuel injection holes is 4 - 10.

[0014] Preferably, both the first-layer fuel injection holes and the second-layer fuel injection holes are evenly distributed along the circumferential direction of the needle valve body.

[0015] Preferably, the first-layer fuel injection holes and the second-layer fuel injection holes are staggered in the vertical direction.

[0016] Preferably, when the needle valve stem is moved so that the conical surface is separated from the ring groove and the boss covers the position of the first-layer fuel injection holes, the second-layer fuel injection holes are opened separately; when the needle valve stem is moved so that the conical surface is separated from the ring groove and the boss moves away from the position of the first-layer fuel injection holes, the first-layer and second-layer fuel injection holes are opened simultaneously.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention adopts a fuel injector structure with two layers of injection holes in one injector nozzle, having better load adaptability, and can realize the switching between two fuel injection modes by separately opening the second-layer fuel injection holes and simultaneously opening the first-layer and second-layer fuel injection holes; this injector nozzle can not only inject a small amount of pilot fuel, but also inject a large amount of fuel to meet the large-load working mode of pure diesel. Only one diesel injector needs to be arranged, which can reduce the number of injectors arranged on the cylinder head of the dual-fuel engine and simplify the structure of the cylinder head. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of the fuel injector nozzle of the dual-fuel engine of the present invention;

[0020] Figure 2 is a schematic structural view of the needle valve body of the present invention;

[0021] Figure 3 is a schematic structural view of the needle valve stem of the present invention;

[0022] Figure 4 and Figure 5 is a schematic structural view of the two - layer spray hole distribution of the present invention. Specific Embodiments

[0023] A fuel injector for a dual - fuel engine proposed by the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and all use non - precise scales, only for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention. In order to make the objectives, features, and advantages of the present invention more obvious and understandable, please refer to the accompanying drawings. It should be known that the structures, scales, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical essence. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the efficacy that the present invention can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0024] Such as Figure 1 、 Figure 2 and Figure 3As shown in the figure, the present invention provides a fuel injector for a dual-fuel engine, which includes a nozzle body 1 and a valve stem 4. An oil inlet passage 2 is obliquely arranged inside the nozzle body 1. An oil cavity 3 is communicated below the oil inlet passage 2, and an annular oil passage 8 is communicated at the bottom of the oil cavity 3. The bottom of the nozzle body 1 is respectively provided with a first layer of injection holes 5 and a second layer of injection holes 7 with different heights. The second layer of injection holes 7 is located below the first layer of injection holes 5. The valve stem 4 is movably arranged inside the nozzle body 1 and can move axially along the nozzle body 1. A boss 10 is arranged on the valve stem 4. The boss 10 is circumferentially and sealingly connected with the inner wall of the annular oil passage 8 to form an annular first sealing surface 11, thereby dividing the annular oil passage 8 into an upper oil passage 81 and a lower oil passage 82. A valve stem oil passage 6 for communicating the upper oil passage 81 and the lower oil passage 82 is also arranged on the valve stem 4. The two ends of the valve stem oil passage 6 are respectively located above and below the boss 10. The bottom end of the valve stem 4 is provided with a conical surface 12. A ring groove 13 for sealing connection with the conical surface 12 is arranged at the bottom of the nozzle body 1. A pressure chamber 9 is arranged below the ring groove 13. The second layer of injection holes 7 is arranged in the pressure chamber 9. When the conical surface 12 of the valve stem 4 moves away from the ring groove 13, the pressure chamber 9 is communicated with the lower oil passage 82. When the valve stem 4 is inserted into the nozzle body 1, the conical surface 12 is sealingly connected with the ring groove 13 of the nozzle body 1 to form a second sealing surface 14. The outer surface of the upper end of the valve stem 4 is sealingly connected with the inner surface of the nozzle body 1 to form a third sealing surface 15. When the valve stem 4 is inserted into the nozzle body 1, the first layer of injection holes 5 is arranged at the position of the first sealing surface 11. At this time, the first layer of injection holes 5 is sealed and closed by the boss 10, and the second layer of injection holes 7 is sealed and closed by the conical surface 12 and the ring groove 13. Axially moving the valve stem 4 can move the conical surface 12 away from the ring groove 13, thereby opening the second layer of injection holes 7. Continuing to move the valve stem 4 upward can move the boss 10 away from the position of the first layer of injection holes 5, thereby further opening the first layer of injection holes 5.

[0025] When only the second layer of injection holes 7 is used for fuel injection, the lifting height of the valve stem 4 is controlled so that the conical surface 12 of the valve stem 4 is separated from the ring groove 13 of the nozzle body 1. The annular oil passage 8 is communicated with the pressure chamber 9. Fuel enters the annular oil cavity 3 through the oblique oil inlet passage 2. The fuel in the annular oil cavity 3 flows downward into the annular oil passage 8. Due to the obstruction of the cylindrical first sealing surface 11 formed by the contact between the outer surface of the boss 10 and the inner wall of the nozzle body 1, the fuel in the upper oil passage 81 enters the lower oil passage 82 again through the valve stem oil passage 6. At this time, the second layer of injection holes 7 is communicated with the entire fuel supply path (i.e., the oil path entering the oil cavity 3 and the annular oil passage 8 through the oil inlet passage 2). After the fuel enters the pressure chamber 9, it is ejected through the second layer of injection holes 7.

[0026] When injecting fuel through the first-layer fuel injection holes 5 and the second-layer fuel injection holes 7 simultaneously, since the outer surface of the boss 10 contacts the inner wall of the nozzle body 1 to form a cylindrical first sealing surface 11 that seals the first-layer fuel injection holes 5, it is necessary to control the lifting height of the needle valve stem 4 so that the cylindrical first sealing surface 11 crosses the position where the first-layer fuel injection holes 5 are located. At this time, the lower oil passage 82 communicates with the first-layer fuel injection holes 5, and the first-layer fuel injection holes 5 are opened. The fuel entering the lower oil passage 82 through the above fuel supply passage is ejected from the first-layer fuel injection holes 5. At the same time, the fuel passing through the above fuel supply passage also flows into the pressure chamber 9 and is ejected through the second-layer fuel injection holes 7.

[0027] As Figure 4 , 5 shown, two layers of fuel injection holes are arranged circumferentially on the nozzle body 1. The first-layer fuel injection holes 5 and the second-layer fuel injection holes 7 are evenly distributed at the bottom of the nozzle body 1. At the same time, the fuel injection holes of the two layers are staggered in the vertical direction. More specifically, the first-layer fuel injection holes 5 are opened at the first sealing surface 11 on the nozzle body 1 and are large-aperture fuel injection holes. The number of the first-layer fuel injection holes 5 is 4 - 10. The second-layer fuel injection holes 7 are opened at the pressure chamber 9 and are small fuel injection holes for ignition. The number of the second-layer fuel injection holes 7 is 4 - 10.

[0028] In summary, the fuel injector for a dual-fuel engine provided by the present invention can achieve a flexible fuel injection strategy by using the first and second layers of fuel injection holes, has better load adaptability, can inject a small amount of pilot fuel, and can also inject a large amount of fuel to meet the large-load working mode of pure diesel. Only one diesel injector is used, which can reduce the number of injectors arranged on the dual-fuel engine, save the space of the engine cylinder head, and meet the current development requirements of engine intensification.

[0029] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A dual-fuel engine fuel injector, characterized in that, Comprising: A needle valve body (1) and a needle valve stem (4); an oil inlet passage (2) is provided inside the needle valve body (1), an oil cavity (3) communicated with the oil inlet passage (2), and a first layer of injection holes (5) and a second layer of injection holes (7) with different heights are respectively provided at the bottom of the needle valve body (1); The needle valve stem (4) is movably arranged inside the needle valve body (1), and an annular oil passage (8) is formed between the needle valve stem (4) and the needle valve body (1), and the annular oil passage (8) is communicated with the oil cavity (3); A boss (10) is further provided on the needle valve stem (4), and the first layer of injection holes (5) is arranged at the sealed connection between the boss (10) and the inner wall of the annular oil passage (8). Axially moving the needle valve stem (4) can control the opening or closing of the first layer of injection holes (5) by the boss (10), so as to control the simultaneous opening of the first layer of injection holes (5) and the second layer of injection holes (7), or the separate opening of the second layer of injection holes (7); the boss (10) is circumferentially and sealingly connected with the inner wall of the needle valve body (1) to divide the annular oil passage (8) into an upper oil passage (81) and a lower oil passage (82); a needle valve oil passage (6) is also provided at the position of the boss (10) on the needle valve stem (4), and the upper oil passage (81) and the lower oil passage (82) are communicated through the needle valve oil passage (6); The needle valve oil passage (6) is obliquely arranged inside the needle valve stem (4).

2. The fuel injector of the dual-fuel engine according to claim 1, characterized in that A conical surface (12) is provided at the bottom end of the needle valve stem (4), a ring groove (13) sealingly connected with the conical surface (12) is provided at the bottom of the needle valve body (1), and a pressure chamber (9) is provided below the ring groove (13); the second layer of injection holes (7) is arranged in the pressure chamber (9).

3. The fuel injector of the dual-fuel engine according to claim 1, characterized in that, The aperture of the first layer of injection holes (5) is larger than that of the second layer of injection holes (7).

4. The fuel injector of the dual-fuel engine according to claim 1, characterized in that, The number of both the first layer of injection holes (5) and the second layer of injection holes (7) is 4 - 10.

5. The fuel injector of the dual-fuel engine according to claim 1, characterized in that, Both the first layer of injection holes (5) and the second layer of injection holes (7) are evenly distributed along the circumferential direction of the needle valve body (1).

6. The fuel injector of the dual-fuel engine according to claim 1, wherein The first layer of injection holes (5) and the second layer of injection holes (7) are staggeredly distributed in the vertical direction.

7. The fuel injector of the dual-fuel engine according to claim 1, characterized in that, The outer surface at the upper end of the needle valve stem (4) is sealingly connected with the inner surface of the needle valve body (1).

8. The fuel injector of the dual-fuel engine according to claim 2, characterized in that When the needle valve stem (4) is moved so that the conical surface (12) is separated from the ring groove (13) and the boss (10) covers the position of the first layer of injection holes (5), the second layer of injection holes (7) is separately opened; when the needle valve stem (4) is moved so that the conical surface (12) is separated from the ring groove (13) and the boss (10) moves away from the position of the first layer of injection holes (5), the first layer of injection holes (5) and the second layer of injection holes (7) are simultaneously opened.

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