Air-assisted alternative fuel injection device, multi-point injection engine and operation method

Abstract

The invention relates to a gas-assisted alternative fuel injection device, a multi-point injection engine and an operation method.The gas-assisted alternative fuel injection device comprises a device body, one end of the device body is an injection end, and an alternative fuel channel and a high-temperature gas channel are arranged in the device body; the alternative fuel channel extends from the interior of the device body to the injection end to form an alternative fuel injection opening, and the high-temperature gas channel extends from the interior of the device body to the injection end to form a plurality of gas injection openings evenly distributed in the circumferential direction of the alternative fuel injection opening. The high-temperature gas channel is used for communicating with an exhaust pipeline of the engine or communicating with a gas inlet pipeline of the engine between the supercharger and the intercooler. According to the injection device, high-temperature gas is used for assisting injection, the fuel atomization condition can be improved, alternative fuel and air can be well mixed, the problem that the alternative fuel such as methyl alcohol or liquid ammonia is difficult to vaporize at low temperature can be solved, an engine can adapt to various severe environments and working conditions, and the operation stability of the engine is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and particularly relates to an air-assisted alternative fuel injection device, a multi-point injection engine and an operation method thereof. Background Art

[0002] Reducing greenhouse gas emissions has always been a key concern in the shipping industry. Only by researching and promoting the large-scale utilization of low-carbon / zero-carbon alternative fuels for ships can the problem of shipping greenhouse gas emissions be fundamentally solved. Methanol or ammonia fuel, as a new type of ship alternative fuel, has received increasing attention. Correspondingly, the research and promotion of alternative fuel engines such as marine methanol and ammonia fuels are also proceeding steadily.

[0003] In the prior art, the alternative fuel engine directly sprays the liquid alternative fuel into the required position by an injection device. In all-weather environments, such as different pressures and different temperatures, and under different engine operating conditions, especially at low temperatures and during rapid acceleration, it is difficult to maintain good mixing uniformity between the alternative fuel and air, which easily leads to poor atomization or wetting of the oil mist on the wall, forming an oil film. The accumulated alternative fuel liquid along the wall will drip down after long-term wetting and flow into the combustion chamber, causing uneven combustion or knocking, and affecting the smooth operation of the engine. Summary of the Invention

[0004] The first object of the present invention is to provide an air-assisted alternative fuel injection device to solve the problem that the current mixing uniformity between the alternative fuel and air is poor, which easily causes poor smoothness of the engine.

[0005] The second object of the present invention is to provide a multi-point injection engine and an operation method based on the above air-assisted alternative fuel injection device.

[0006] To achieve the above objects, the present invention provides the following technical solutions:

[0007] An air-assisted alternative fuel injection device includes a device main body. One end of the device main body is an injection end. An alternative fuel passage and a high-temperature gas passage are provided in the device main body. The alternative fuel passage extends from inside the device main body to the injection end to form an alternative fuel injection port. The high-temperature gas passage extends from inside the device main body to the injection end to form a plurality of gas injection ports circumferentially and uniformly distributed around the alternative fuel injection port. The high-temperature gas passage is used to communicate with the exhaust pipe of the engine or communicate with the intake pipe of the engine between the supercharger and the intercooler.

[0008] In an embodiment of the present application, the high-temperature gas passage includes a gas delivery passage, an annular diversion passage, and a plurality of gas outlet passages. The gas delivery passage is in communication with the annular diversion passage. The first end of each gas outlet passage is in communication with the annular diversion passage, and the second end of each gas outlet passage forms the gas injection port at the injection end.

[0009] In an embodiment of the present application, the alternative fuel passage includes a fuel delivery passage and a plurality of fuel outlet passages. The first end of each fuel outlet passage is in communication with the fuel delivery passage, and the second end of each fuel outlet passage forms a plurality of the alternative fuel injection ports at the injection end. Each gas injection port surrounds the alternative fuel injection port array formed by each alternative fuel injection port.

[0010] In an embodiment of the present application, the fuel delivery passage includes a first delivery passage and a second delivery passage that are coaxially and sequentially connected. The first delivery passage is in communication with each fuel outlet passage through the second delivery passage. The diameter of the second delivery passage is greater than the diameter of the first delivery passage. The air-assisted alternative fuel injection device further includes a needle valve assembly disposed in the alternative fuel passage. The needle valve assembly includes:

[0011] A valve needle, including a needle body and a sealing portion. The sealing portion is disposed in the second delivery passage. The transition surface between the second delivery passage and the first delivery passage is used for sealing with the sealing portion to cut off the first delivery passage and the second delivery passage. The first end of the needle body is connected to the sealing portion, the second end of the needle body extends into the first delivery passage, and the needle body is slidably engaged with the device body. A flow-through gap for the alternative fuel to pass through is formed between the needle body and the inner wall of the first delivery passage;

[0012] An actuating member for applying a force to the valve needle to cause the sealing portion to be in sealing engagement with the transition surface when the alternative fuel is not being injected.

[0013] In an embodiment of the present application, the sealing portion is provided with a first sealing cone surface, and the transition surface is a second sealing cone surface. The first sealing cone surface is in sealing engagement with the second sealing cone surface.

[0014] A multi-point injection engine includes a pilot fuel injection device and the air-assisted alternative fuel injection device as described in any one of the above. The high-temperature gas passage of the air-assisted alternative fuel injection device is in communication with the exhaust pipeline of the multi-point injection engine, or the high-temperature gas passage of the air-assisted alternative fuel injection device is in communication with the intake pipeline of the multi-point injection engine between the supercharger and the intercooler.

[0015] An operating method for a multi-point injection engine as described above, comprising:

[0016] Step a: When the engine is in the powered-on but not started state, the air-assisted alternative fuel injection device injects gas, the air-assisted alternative fuel injection device does not inject alternative fuel, and the pilot fuel injection device does not inject pilot fuel;

[0017] Step b: When the engine is in the started state, obtain the engine operating parameters, in response to the obtained engine operating parameters, obtain the engine parameter settings from the memory, and control the alternative fuel injection amount of the air-assisted alternative fuel injection device and the pilot fuel injection amount of the pilot fuel injection device;

[0018] Step c: When the engine receives a shutdown command, the air-assisted alternative fuel injection device keeps injecting gas, stops injecting alternative fuel, the pilot fuel injection device injects pilot fuel, and the engine continues to run for a preset time and then stops.

[0019] In an embodiment of the present application, step b specifically includes:

[0020] Step b1: If the engine is in a low-speed and low-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a first preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a first pilot fuel injection amount;

[0021] Step b2: If the engine is in a medium-speed and medium-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a second preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a second pilot fuel injection amount;

[0022] Step b3: If the engine is in a high-speed and high-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a third preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a third pilot fuel injection amount;

[0023] The first preset alternative fuel injection amount < the second preset alternative fuel injection amount < the third preset alternative fuel injection amount;

[0024] The first preset pilot fuel injection amount > the second preset pilot fuel injection amount > the third preset pilot fuel injection amount. [[ID=z8]]

[0025] In an embodiment of the present application, step b1 further includes:

[0026] Obtain the time when the engine is in a low-speed and low-load operating state. If the time when the engine is in a low-speed and low-load operating state exceeds a preset duration, then as the time when the engine is in a low-speed and low-load operating state increases, gradually reduce the alternative fuel injection amount of the air-assisted alternative fuel injection device, and gradually increase the pilot fuel injection amount of the pilot fuel injection device.

[0027] In an embodiment of the present application, the preset time is 30s to 60s.

[0028] As can be seen from the above technical solutions, the present invention discloses an air-assisted alternative fuel injection device. The air-assisted alternative fuel injection device includes a device main body. One end of the device main body is an injection end. An alternative fuel passage and a high-temperature gas passage are arranged in the device main body. The alternative fuel passage extends from the inside of the device main body to the injection end to form an alternative fuel injection port. The high-temperature gas passage extends from the inside of the device main body to the injection end to form a plurality of gas injection ports circumferentially and evenly distributed around the alternative fuel injection port. The high-temperature gas passage is used to communicate with the exhaust pipe of the engine or communicate with the intake pipe of the engine between the supercharger and the intercooler.

[0029] The above air-assisted alternative fuel injection device uses high-temperature gas to assist in injection. It can not only break and atomize liquid droplets into small particles through high-temperature gas, solve the problem of too large liquid droplet particles or poor atomization in the injection system, and enable the alternative fuel to be well mixed with air, but also solve the problem that alternative fuels such as methanol or liquid ammonia are difficult to vaporize at low temperatures, enable the engine to adapt to various harsh environments and working conditions, and improve the running stability of the engine. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic structural diagram of the air-assisted alternative fuel injection device provided by the embodiment of the present invention;

[0032] Figure 2 It is the first sectional view of the air-assisted alternative fuel injection device provided by the embodiment of the present invention;

[0033] Figure 3 It is a partial schematic view of the first sectional view of the air-assisted alternative fuel injection device provided by the embodiment of the present invention;

[0034] Figure 4The second sectional view of the air-assisted alternative fuel injection device provided by the embodiment of the present invention;

[0035] Figure 5 The schematic structural diagram of the injection end of the air-assisted alternative fuel injection device provided by the embodiment of the present invention;

[0036] Figure 6 The flowchart of the operation method of the multi-point injection engine provided by the embodiment of the present invention.

[0037] In the figure:

[0038] 1 is the device main body; 2 is the injection end; 3 is the alternative fuel channel; 301 is the first delivery channel; 302 is the second delivery channel; 303 is the fuel outlet channel; 304 is the alternative fuel injection port; 4 is the high-temperature gas channel; 401 is the gas delivery channel; 402 is the annular diversion channel; 403 is the gas outlet channel; 404 is the gas injection port; 5 is the valve needle; 501 is the needle body; 502 is the sealing part. Detailed implementation manners

[0039] One of the cores of the present invention is to provide an air-assisted alternative fuel injection device. The structural design of the air-assisted alternative fuel injection device enables it to solve the problems of poor mixing uniformity of the current alternative fuel and air, which is likely to cause poor engine smoothness.

[0040] Another core of the present invention is to provide a multi-point injection engine and an operation method using the above air-assisted alternative fuel injection device.

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Please refer to Figures 1 to 5 .

[0043] An air-assisted alternative fuel injection device is disclosed in the embodiment of the present invention. The air-assisted alternative fuel injection device includes a device main body 1. One end of the device main body 1 is an injection end 2. An alternative fuel channel 3 and a high-temperature gas channel 4 are arranged in the device main body 1. The alternative fuel channel 3 extends from inside the device main body 1 to the injection end 2 to form an alternative fuel injection port 304. The high-temperature gas channel 4 extends from inside the device main body 1 to the injection end 2 to form a plurality of gas injection ports 404 that are circumferentially evenly distributed around the alternative fuel injection port 304. The high-temperature gas channel 4 is used to communicate with the exhaust pipe of the engine or communicate with the intake pipe of the engine between the supercharger and the intercooler.

[0044] During application, the high-temperature gas passage 4 extracts high-temperature exhaust gas from the engine exhaust pipe or high-temperature intake air between the supercharger and the intercooler for assisting alternative fuel injection. In the solution of using high-temperature exhaust gas as the auxiliary gas source, it can also reduce the NOx emissions of the engine, especially ammonia fuel engines. Since multiple gas injection ports 404 are arranged around the alternative fuel injection port 304, when high-temperature gas and alternative fuel are injected simultaneously, the high-temperature gas jet around the alternative fuel can break up the large liquid particles of the diffused alternative fuel, making the droplets finer, improving the atomization effect. At the same time, it can also use the high-temperature gas to heat the alternative fuel droplets, further improving the vaporization effect.

[0045] Compared with the prior art, the gas-assisted alternative fuel injection device provided by the embodiment of the present invention uses high-temperature gas to assist injection. It can not only break and atomize liquid droplets into small particles through the high-temperature gas, solve the problem of too large droplet particles or poor atomization in the injection system, and enable the alternative fuel to be well mixed with air, but also solve the problem that alternative fuels such as methanol or liquid ammonia are difficult to vaporize at low temperatures, enabling the engine to adapt to various harsh environments and working conditions and improving the running stability of the engine.

[0046] As Figures 2 to 4 shown, the high-temperature gas passage 4 includes a gas delivery passage 401, an annular diversion passage 402, and a plurality of gas outlet passages 403. The gas delivery passage 401 is connected to the annular diversion passage 402. The first end of each gas outlet passage 403 is connected to the annular diversion passage 402, and the second end of each gas outlet passage 403 forms a gas injection port 404 at the injection end 2. The high-temperature gas first enters the gas delivery passage 401, enters the annular diversion passage 402 along the gas delivery passage 401, then enters each gas outlet passage 403, and finally sprays out from the gas injection port 404.

[0047] Correspondingly, as Figures 2 to 4 shown, the alternative fuel passage 3 includes a fuel delivery passage and a plurality of fuel outlet passages 303. The first end of each fuel outlet passage 303 is connected to the fuel delivery passage, and the second end of each fuel outlet passage 303 forms a plurality of alternative fuel injection ports 304 at the injection end. Each gas injection port 404 surrounds the array of alternative fuel injection ports 304 formed by each alternative fuel injection port 304. The alternative fuel first enters the fuel delivery passage, then passes through the fuel outlet passages 303, and finally sprays out through the alternative fuel injection ports 304.

[0048] Furthermore, in order to control the injection of the alternative fuel, in one embodiment of the present application, as Figure 2 and Figure 3As shown, the fuel delivery passage includes a first delivery passage 301 and a second delivery passage 302 that are coaxial and connected in sequence. The first delivery passage 301 communicates with each fuel outlet passage 303 through the second delivery passage 302. The diameter of the second delivery passage 302 is larger than that of the first delivery passage 301 to facilitate the installation of a needle valve assembly for controlling the injection of alternative fuel.

[0049] The needle valve assembly includes a valve needle 5 and an actuator. Among them, the valve needle 5 includes a needle body 501 and a sealing portion 502. The sealing portion 502 is disposed in the second delivery passage 302. The transition surface between the second delivery passage 302 and the first delivery passage 301 is used to seal with the sealing portion 502 to cut off the first delivery passage 301 and the second delivery passage 302. The first end of the needle body 501 is connected to the sealing portion 502. The second end of the needle body 501 extends into the first delivery passage 301, and the needle body 501 is slidably engaged with the device main body 1. A flow passage gap for the alternative fuel to pass through is formed between the needle body 501 and the inner wall of the first delivery passage 301.

[0050] The actuator is used to apply a force to the valve needle 5 so that when the alternative fuel is not injected, the sealing portion 502 is in sealing cooperation with the transition surface. The actuator includes, but is not limited to, a spring, a piston cylinder, an electromagnet, etc., as long as it can drive the needle body 501 to reciprocate.

[0051] In a preferred embodiment, the actuator is a spring disposed in the second delivery passage 302. The spring is disposed between the actuator and the device main body 1. When the alternative fuel is not injected, the spring is in an unforced state. The pre-tightening force of the spring itself pushes the sealing portion 502 of the actuator to be in sealing cooperation with the transition surface. When the injection of the alternative fuel starts, the valve needle 5 moves under the pressure of the alternative fuel, so that the sealing portion 502 is disengaged from the transition surface to achieve the injection of the alternative fuel.

[0052] Of course, the actuator can also be provided with structures such as a piston cylinder and an electromagnet on the basis of the spring to increase the response speed of the needle valve assembly.

[0053] Further, to improve the sealing effect, the sealing portion 502 is provided with a first sealing cone surface, and the transition surface is a second sealing cone surface. The first sealing cone surface is in sealing cooperation with the second sealing cone surface. As the actuator pushes the valve needle 5, the first sealing cone surface and the second sealing cone surface can fit together to achieve a good sealing effect.

[0054] The air-assisted alternative fuel injection device further includes a pressure detection device. The pressure detection device is used to detect the gas pressure in the high-temperature gas passage 4 and alarm the user through the engine controller when the gas pressure is lower than the preset air pressure value.

[0055] The embodiment of the present application also provides a multi-point injection engine, which includes an ignition fuel injection device and the air-assisted alternative fuel injection device as described in the above embodiment. Among them, the ignition fuel injection device is used to inject ignition fuel, and the ignition fuel includes but is not limited to diesel. The high-temperature gas passage 4 of the air-assisted alternative fuel injection device is communicated with the exhaust pipeline of the multi-point injection engine, or the high-temperature gas passage 4 of the air-assisted alternative fuel injection device is communicated with the intake pipeline of the multi-point injection engine between the supercharger and the intercooler. Since the multi-point injection engine adopts the air-assisted alternative fuel injection device in the above embodiment, the technical effects of the multi-point injection engine can be referred to the above embodiment.

[0056] The embodiment of the present application also provides an operation method of the multi-point injection engine as described in the above embodiment, as Figure 6 shown, the operation method includes:

[0057] Step a: When the engine is in the power-on and unstarted state, the air-assisted alternative fuel injection device injects gas, the air-assisted alternative fuel injection device does not inject alternative fuel, and the ignition fuel injection device does not inject ignition fuel.

[0058] When the engine is in the power-on and unstarted state, the engine is not actually running. At this time, the air-assisted alternative fuel injection device pre-injects gas for blowing and cleaning, and at the same time detects whether the air pressure is normal. If it is normal, continue to wait for the engine to start. If it is not normal, alarm and wait for maintenance and replacement.

[0059] Step b: When the engine is in the starting state, obtain the engine operation parameters, in response to the obtained engine operation parameters, obtain the engine parameter settings from the memory, and control the alternative fuel injection amount of the air-assisted alternative fuel injection device and the ignition fuel injection amount of the ignition fuel injection device.

[0060] When the engine just starts, the speed is unstable. The air-assisted alternative fuel injection device keeps injecting gas and does not inject alternative fuel, but runs with ignition fuel such as diesel to heat the engine and increase the engine temperature. After the engine speed is stable, then according to the pre-stored engine parameter settings in the memory, control the alternative fuel injection amount of the air-assisted alternative fuel injection device and the ignition fuel injection amount of the ignition fuel injection device. Under different working conditions of the engine, the ratio of the alternative fuel injection amount and the ignition fuel injection amount is different to meet the goals of low emissions and optimal economy.

[0061] Step c: When the engine receives a shutdown command, the air-assisted alternative fuel injection device keeps injecting gas, stops injecting alternative fuel, the ignition fuel injection device injects ignition fuel, and the engine continues to run for a preset time and then stops.

[0062] After receiving the shutdown command, the air-assisted alternative fuel injection device still continues to inject gas to purge the alternative fuel in the nozzle and intake passage, preventing the problem of rust on the surface of in-cylinder parts caused by the residue of alternative fuel, which can greatly reduce the harm caused by frequent engine start-stop. In particular, it can play a good role in protecting the nozzle from being cleaned.

[0063] In a specific embodiment of the present application, the above preset time is 30s to 60s.

[0064] Further optimize the above technical solution, such as Figure 5 As shown, step b specifically includes:

[0065] Step b1: If the engine is in a low-speed and low-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a first preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a first preset pilot fuel injection amount.

[0066] Step b2: If the engine is in a medium-speed and medium-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a second preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a second preset pilot fuel injection amount.

[0067] Step b3: If the engine is in a high-speed and high-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a third preset alternative fuel injection amount, and the pilot fuel injection device injects pilot fuel at a third preset pilot fuel injection amount.

[0068] The first preset alternative fuel injection amount < the second preset alternative fuel injection amount < the third preset alternative fuel injection amount.

[0069] The first preset pilot fuel injection amount > the second preset pilot fuel injection amount > the third preset pilot fuel injection amount.

[0070] It can be seen that when the engine is in a low-speed and low-load operating state, the pilot fuel injection amount is the largest and the alternative fuel injection amount is the smallest; when the engine is in a medium-speed and medium-load operating state, the pilot fuel injection amount and the alternative fuel injection amount are moderate; when the engine is in a high-speed and high-load operating state, the pilot fuel injection amount is the smallest and the alternative fuel injection amount is the largest.

[0071] Such as Figure 5 As shown, step b1 further includes:

[0072] Obtain the time when the engine is in a low-speed and low-load operating state. If the time when the engine is in a low-speed and low-load operating state exceeds the preset duration, then as the time when the engine is in a low-speed and low-load operating state increases, gradually reduce the alternative fuel injection amount of the air-assisted alternative fuel injection device until the alternative fuel injection amount is 0, and gradually increase the pilot fuel injection amount of the pilot fuel injection device.

[0073] As shown in this application and the claims, unless the context clearly indicates otherwise, words such as "a", "an", "one", and / or "the" are not specifically singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. A method or device may also include other steps or elements. An element defined by the statement "comprising one..." does not exclude the existence of other identical elements in the process, method, article, or device that includes the element.

[0074] In the description of this application, unless otherwise clearly defined, words such as "arrangement", "installation", "connection", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in this application in combination with the specific content of the technical solution.

[0075] It should be noted that the various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts among the embodiments can be referred to each other.

[0076] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An air-assisted alternative fuel injection device, characterized in that, It includes a device main body (1), one end of the device main body (1) is a spraying end (2), a substitute fuel passage (3) and a high-temperature gas passage (4) are arranged in the device main body (1), the substitute fuel passage (3) extends from inside the device main body (1) to the spraying end (2) to form a substitute fuel spraying port (304), the high-temperature gas passage (4) extends from inside the device main body (1) to the spraying end (2) to form a plurality of gas spraying ports (404) circumferentially and uniformly distributed around the substitute fuel spraying port (304), and the high-temperature gas passage (4) is used to communicate with the exhaust pipe of the engine or communicate with the intake pipe of the engine between the supercharger and the intercooler.

2. The air-assisted alternative fuel injection device according to claim 1, wherein The high-temperature gas passage (4) includes a gas delivery passage (401), an annular diversion passage (402) and a plurality of gas outlet passages (403), the gas delivery passage (401) is communicated with the annular diversion passage (402), the first end of each gas outlet passage (403) is communicated with the annular diversion passage (402), and the second end of each gas outlet passage (403) forms the gas spraying port (404) at the spraying end (2).

3. The air-assisted alternative fuel injection device according to claim 1, wherein The substitute fuel passage (3) includes a fuel delivery passage and a plurality of fuel outlet passages (303), the first end of each fuel outlet passage (303) is communicated with the fuel delivery passage, the second end of each fuel outlet passage (303) forms a plurality of the substitute fuel spraying ports (304) at the spraying end, and each gas spraying port (404) is arranged outside the substitute fuel spraying port (304) array formed by each substitute fuel spraying port (304).

4. The air-assisted alternative fuel injection device according to claim 3, characterized in that, The fuel delivery passage includes a first delivery passage (301) and a second delivery passage (302) which are coaxially and sequentially connected, the first delivery passage (301) is communicated with each fuel outlet passage (303) through the second delivery passage (302), the diameter of the second delivery passage (302) is larger than that of the first delivery passage (301), and the air-assisted substitute fuel injection device further includes a needle valve assembly arranged in the substitute fuel passage (3), and the needle valve assembly includes: A valve needle (5), including a needle body (501) and a sealing part (502), the sealing part (502) is arranged in the second delivery passage (302), and the transition surface between the second delivery passage (302) and the first delivery passage (301) is used to seal with the sealing part (502) to cut off the first delivery passage (301) and the second delivery passage (302), the first end of the needle body (501) is connected to the sealing part (502), the second end of the needle body (501) extends into the first delivery passage (301), and the needle body (501) is slidably matched with the device main body (1), and a flow-through gap for the substitute fuel to pass through is formed between the needle body (501) and the inner wall of the first delivery passage (301). An actuator for applying a force to the valve needle (5) to cause the sealing portion (502) to be in sealing fit with the transition surface when the alternative fuel is not being injected.

5. The air-assisted alternative fuel injection device according to claim 4, wherein, The sealing portion (502) is provided with a first sealing conical surface, and the transition surface is a second sealing conical surface, and the first sealing conical surface is in sealing fit with the second sealing conical surface.

6. A multi-point injection engine, characterized in that, Comprising an ignition fuel injection device and the air-assisted alternative fuel injection device according to any one of claims 1-5, wherein the high-temperature gas passage (4) of the air-assisted alternative fuel injection device communicates with the exhaust pipe of the multi-point injection engine, or the high-temperature gas passage (4) of the air-assisted alternative fuel injection device communicates with the intake pipe of the multi-point injection engine between the supercharger and the intercooler.

7. A method for operating a multi-point injection engine as claimed in claim 6, characterized in that, Comprising: Step a: When the engine is in the power-on and unstarted state, the air-assisted alternative fuel injection device injects gas, the air-assisted alternative fuel injection device does not inject alternative fuel, and the ignition fuel injection device does not inject ignition fuel; Step b: When the engine is in the starting state, obtain the engine operating parameters, in response to the obtained engine operating parameters, obtain the engine parameter settings from the memory, and control the alternative fuel injection amount of the air-assisted alternative fuel injection device and the ignition fuel injection amount of the ignition fuel injection device; Step c: When the engine receives a shutdown command, the air-assisted alternative fuel injection device keeps injecting gas, stops injecting alternative fuel, the ignition fuel injection device injects ignition fuel, and the engine continues to run for a preset time and then stops.

8. The operating method according to claim 7, characterized in that The specific content of step b includes: Step b1: If the engine is in a low-speed and low-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a first preset alternative fuel injection amount, and the ignition fuel injection device injects ignition fuel at a first ignition fuel injection amount; Step b2: If the engine is in a medium-speed and medium-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a second preset alternative fuel injection amount, and the ignition fuel injection device injects ignition fuel at a second ignition fuel injection amount; Step b3: If the engine is in a high-speed and high-load operating state, the air-assisted alternative fuel injection device injects alternative fuel at a third preset alternative fuel injection amount, and the ignition fuel injection device injects ignition fuel at a third ignition fuel injection amount; The first preset alternative fuel injection amount < the second preset alternative fuel injection amount < the third preset alternative fuel injection amount; The first preset alternative fuel injection amount > the second preset alternative fuel injection amount > the third preset alternative fuel injection amount.

9. The operating method according to claim 8, characterized in that The specific content of step b1 further includes: Obtain the time when the engine is in the low-speed and low-load operating state. If the time when the engine is in the low-speed and low-load operating state exceeds the preset duration, then as the time when the engine is in the low-speed and low-load operating state increases, gradually reduce the alternative fuel injection amount of the air-assisted alternative fuel injection device and gradually increase the ignition fuel injection amount of the ignition fuel injection device.

10. The operating method according to claim 7, characterized in that, The preset time is 30s - 60s.

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