A methanol engine system and control method

Abstract

This invention relates to the field of engine technology, specifically disclosing a methanol engine system. The system includes at least two methanol injectors on the intake manifold of the cylinder, each injector comprising a nozzle, with the two nozzles arranged sequentially along the extension direction of the intake manifold. By selecting different nozzles to change the position of the methanol spray in the intake manifold, and by adjusting parameters such as the injection pressure and timing of the two nozzles, the system can adapt to changes in engine operating conditions. This results in a more uniform methanol-air mixture entering the cylinder and ensures that the methanol spray remains in the center of the intake manifold flow path, reducing the formation of a liquid film on the intake manifold wall, thus achieving good combustion and emission performance. This invention also provides a control method for the methanol engine system, applicable to the aforementioned methanol engine system.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and in particular to a methanol engine system and control method. Background Technology

[0002] Existing methanol engine systems (hereinafter referred to as engines) have two methanol fuel injection methods: one is that methanol is injected into the intake manifold by a methanol nozzle; the other is that methanol is injected into the cylinder by a methanol nozzle.

[0003] For methanol injection via nozzles inside the intake manifold, methanol injection devices are more widely used due to their low injection pressure and the fact that the nozzles do not need to withstand high temperatures, resulting in lower cost and higher reliability. However, this technology also has problems such as uneven distribution of the injected methanol in the intake air, and some of the injected methanol droplets forming a liquid film on the intake manifold wall after colliding with it. This can lead to unstable combustion in the engine, increased methanol escape in the exhaust gas, and reduced energy efficiency.

[0004] Therefore, there is an urgent need for a methanol engine system and control method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a methanol engine system and control method, wherein the methanol injection device can adaptively adjust the methanol injection mode according to the engine speed and load operating status, improve the uniformity of methanol in the intake air, and at the same time reduce the amount of methanol adhering to the wall and the amount of methanol escaping, thereby improving energy efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a methanol engine system, the methanol engine system comprising:

[0008] A cylinder, wherein a compression space is formed inside the cylinder, the compression space is connected to the intake passage through a valve, the intake passage is also connected to the intake manifold, and the intake manifold can deliver air into the intake passage;

[0009] At least two methanol injectors are connected to a methanol main pipe. Each methanol injector includes a nozzle. At least two nozzles are disposed on the intake duct and are arranged sequentially along the extension direction of the intake duct. The horizontal distance 'a' between the nozzles and the valve decreases sequentially, and the vertical distance 'd' between the nozzles and the inner wall of the intake duct decreases sequentially. The nozzles can inject methanol into the intake duct.

[0010] Optionally, the cylinder includes a cylinder body and a cylinder head, the cylinder body and the cylinder head enclosing the compression space, the methanol injector is fixed to the cylinder head, and the nozzle passes through the cylinder head and is arranged in the intake manifold.

[0011] Optionally, the cylinder includes a crankshaft gear with missing teeth and a crankshaft that is drivenly connected to the crankshaft gear. The crankshaft gear is provided with a first displacement sensor, which is used to detect the high and low level signals and the missing tooth signal of the crankshaft gear.

[0012] The cylinder also includes a camshaft gear, on which a second displacement sensor is provided. The second displacement sensor is used to detect the position information of the piston in the cylinder, and the piston is connected to the crankshaft drive.

[0013] Optionally, the methanol engine system further includes an engine control system, which is communicatively connected to the first displacement sensor and the second displacement sensor.

[0014] Optionally, multiple cylinders are provided, each cylinder is connected to an air intake, and at least two methanol injectors are arranged on each air intake.

[0015] Optionally, the intake manifold is connected to multiple intake ducts, and the intake manifold can deliver air to each of the intake ducts respectively. The intake manifold is equipped with a pressure sensor, which is used to detect the pressure information in the intake manifold.

[0016] Optionally, the methanol main pipe is connected to multiple methanol branch pipes, each of which is connected to a methanol injector, and the methanol main pipe can deliver methanol to each of the intake ducts respectively.

[0017] Optionally, the methanol main pipe is connected to a methanol tank via a delivery pipeline, and the delivery pipeline is equipped with a methanol pump and a methanol pressure regulating valve.

[0018] Optionally, each of the cylinders is connected to an exhaust manifold for discharging exhaust gases from the combustion of methanol.

[0019] On the other hand, the present invention provides a control method for a methanol engine system, applicable to any of the methanol engine systems described above, the specific steps of which include:

[0020] A first displacement sensor detects high / low level signals and missing tooth signals on the crankshaft gear and transmits these signals to the engine control system. The engine control system calculates the crankshaft angle and engine speed in real time based on these signals. Simultaneously, the engine control system drives at least one methanol injector on each cylinder to activate or deactivate injection at a specific crankshaft angle. This specific crankshaft angle is determined based on the engine speed and the boost pressure in the intake manifold; the boost pressure is calculated from pressure information detected by a pressure sensor.

[0021] The piston position information is detected by the second displacement sensor and transmitted to the engine control system. The engine control system determines whether the cylinder is in the intake / exhaust stroke or the compression / power stroke based on the position information.

[0022] At a specific moment during the intake and exhaust stroke of the cylinder, the nozzle of at least one methanol injector injects methanol into the intake manifold, and during this process, the intake manifold continuously supplies air into the intake manifold; the specific moment is determined by the engine control system based on the engine speed and engine load.

[0023] The injection rate of the nozzle is adjusted by regulating the methanol pump and the methanol pressure regulating valve, and the methanol injected by the nozzle is always kept in the middle position of the air intake.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention provides a methanol engine system, including a cylinder and at least two methanol injectors. The at least two methanol injectors are mounted on the cylinder, and both injectors can spray methanol into the cylinder's intake manifold. Each methanol injector includes a nozzle, and the at least two nozzles are arranged sequentially along the extension direction of the intake manifold. The horizontal distance 'a' between the nozzles and the valve decreases sequentially, as does the vertical distance 'd' between the nozzles and the inner wall of the intake manifold. By selecting different nozzles from the methanol injectors to spray methanol into the intake manifold, the horizontal and vertical positions of the nozzles spraying methanol in the intake manifold are optimized. Combined with adjustments to parameters such as the injection pressure and injection timing of the two nozzles, the system can adapt to changes in engine operating conditions, thereby forming a more uniform methanol-air mixture entering the cylinder and ensuring that the methanol spray is always in the middle of the intake manifold flow channel. This reduces the formation of a liquid film on the intake manifold wall, resulting in better combustion and emissions. The system requires fewer structural modifications, has lower costs, and a wider range of applications.

[0026] This invention also provides a control method for a methanol engine system, which is applied to the aforementioned methanol engine system. The engine control system determines the timing of each cylinder of the engine and then injects methanol into the intake manifold at the specified timing. This ensures that methanol is injected into the intake manifold during periods of high air velocity. By accurately calculating the timing of each cylinder, the methanol injection time can be well matched with the variation of the intake air velocity, thereby ensuring good mixing and atomization of methanol and achieving the best effect. At the same time, the engine control system adjusts the methanol injection rate and injection position according to the engine speed and engine load, so that the methanol spray is always in the middle of the intake manifold, reducing its contact with the intake manifold wall. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the methanol engine system provided in an embodiment of the present invention;

[0028] Figure 2 This is a partial structural diagram of the cylinder provided in an embodiment of the present invention.

[0029] In the picture:

[0030] 100. Cylinder; 101. Valve; 102. Intake manifold; 103. Cylinder head; 104. Crankshaft gear; 105. First displacement sensor; 106. Camshaft gear; 107. Second displacement sensor;

[0031] 200. Methanol injector; 201. Nozzle;

[0032] 300. Intake manifold; 301. Intake end; 302. Intercooler;

[0033] 400. Methanol main pipe; 401. Methanol branch pipe; 402. Delivery pipeline; 403. Methanol tank; 404. Methanol pump; 405. Methanol pressure regulating valve;

[0034] 500. Main exhaust pipe; 501. Exhaust end;

[0035] 600. Turbocharger. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions. Furthermore, "above," "on top of," and "over" the first feature in relation to the second feature includes the first feature directly above and diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "under," and "below" the first feature in relation to the second feature includes the first feature directly below and diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0038] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0040] like Figure 1 and Figure 2 As shown, this embodiment provides a methanol engine system, which includes a cylinder 100 and at least two methanol injectors 200. A compression space is formed inside the cylinder 100, and the compression space is connected to an intake passage 102 through a valve 101. The intake passage 102 is also connected to an intake manifold 300, which can supply air into the intake passage 102. At least two methanol injectors 200 are disposed on the cylinder 100 and are connected to a methanol manifold 400. Methanol can be supplied to the methanol injectors 200 through the methanol manifold 400, and methanol can be injected into the intake passage 102 through the methanol injectors 200.

[0041] This embodiment uses two methanol injectors 200 as an example. Each methanol injector 200 includes a nozzle 201. Both nozzles 201 are disposed on the air intake duct 102 and arranged sequentially along the extending direction of the air intake duct 102. The extending direction of the air intake duct 102 is... Figure 2 In the F2 direction shown, the horizontal distance 'a' between the two nozzles 201 arranged sequentially and the valve 101 decreases sequentially, and the vertical distance 'd' between the two nozzles 201 and the inner wall of the intake duct 102 also decreases sequentially. The optimal positions of the horizontal distance 'a' between the two nozzles 201 and the valve 101, and the vertical distance 'd' between the nozzles 201 and the inner wall of the intake duct 102 can be obtained experimentally. Each nozzle 201 can inject methanol into the intake duct 102, and the preset direction of methanol injection is... Figure 2 The direction shown is F1, but since air also needs to be supplied within the intake duct 102, the airflow direction is also along... Figure 2 As shown in the F2 direction, due to the influence of high-speed airflow, the actual injection direction of methanol will change during the injection process; that is, the actual injection direction of methanol is... Figure 2 As shown in the F3 direction, this may lead to the problem of methanol droplets colliding with the intake duct 102 and forming a liquid film on the wall, as well as the problem of uneven distribution of methanol in the near term.

[0042] Therefore, by selecting different methanol injectors 200 nozzles 201 to inject methanol into the intake manifold 102, the injection position of methanol is changed. This optimizes the horizontal and vertical positions of the nozzles 201 injecting methanol into the intake manifold 102. By adjusting parameters such as the injection pressure and injection timing of the two nozzles 201, the system can adapt to changes in engine operating conditions, thereby forming a more uniform methanol-air mixture that enters the cylinder 100. It also ensures that the methanol spray is always in the middle of the intake manifold 102 flow channel, reducing the formation of a liquid film on the wall of the intake manifold 102. This results in better combustion and emissions, requires fewer structural modifications, has lower costs, and has a wider range of applications.

[0043] For example, when the engine speed is low and under low load, methanol can be injected through a nozzle 201 with a larger horizontal distance 'a' and a larger vertical distance 'd'. This improves the distribution of methanol in the intake air, increases the contact time between methanol and air, and promotes thorough mixing and atomization. Simultaneously, the higher vertical injection position prevents methanol from accumulating in the lower part of the intake manifold 102 and forming a liquid film, ensuring that as much methanol as possible enters the compression space of the cylinder 100, thereby improving engine performance and reducing emissions. Conversely, when the engine speed is high and under high load, methanol can be injected through a nozzle 201 with a smaller horizontal distance 'a' and a smaller vertical distance 'd'. This prevents methanol from accumulating in the upper part of the intake manifold 102. Furthermore, because this nozzle 201 is close to the valve 101, the intake process is shorter, which helps reduce methanol escape, thereby improving energy efficiency and reducing methanol pollution. Of course, in specific operating conditions requiring a large amount of methanol, both nozzles 201 can also inject methanol simultaneously to meet the combustion needs of the cylinder 100. In summary, when the nozzles 201 of the two methanol injectors 200 inject at different positions and at different times, the space of the entire intake duct 102 can be utilized more fully, which is conducive to forming a more uniform air-fuel mixture and improving engine efficiency.

[0044] As an optional embodiment, the cylinder 100 includes a cylinder block and a cylinder head 103, which together form a compression space. Two methanol injectors 200 are fixed to the cylinder head 103, and the nozzles 201 of the methanol injectors 200 pass through the cylinder head 103 and are arranged in the intake manifold 102. Furthermore, the two methanol injectors 200 are communicatively connected to an engine control system, which can control the opening and closing of the two methanol injectors 200. Specifically, the engine control system can be a microcontroller running a program, etc., which is a mature technology in the industry and will not be elaborated further here.

[0045] Furthermore, the cylinder 100 includes a crankshaft gear 104 with missing teeth and a crankshaft that is driven by the crankshaft gear 104. A first displacement sensor 105 is provided on the crankshaft gear 104. The first displacement sensor 105 is used to detect high and low level signals and missing tooth signals of the crankshaft gear 104. The first displacement sensor 105 is communicatively connected to the engine control system. The engine control system can determine the real-time crankshaft angle of the engine through the detected signals. The cylinder 100 also includes a camshaft gear 106, on which a second displacement sensor 107 is provided. The second displacement sensor 107 is used to detect the position information of the piston in the cylinder 100. The piston is driven by the crankshaft. The second displacement sensor 107 is also communicatively connected to the engine control system. The engine control system can determine whether the cylinder 100 is in the intake / exhaust stroke or the compression / power stroke through the detected position information. Then, based on the real-time calculated crankshaft angles of each cylinder, the engine control system controls the methanol injector 200 to inject methanol at specific moments during the intake and exhaust strokes of cylinder 100. These specific moments are when the crankshaft angle reaches 360°. By injecting methanol at these specific strokes and moments, firstly, the space of the entire intake manifold 102 can be utilized more fully, while the kinetic energy of the intake air can be used to enhance the droplet breaking and atomization effect, which is conducive to forming a more uniform air-fuel mixture and ensuring good mixing and atomization of methanol; secondly, it reduces the escape of methanol into the exhaust gas during the scavenging process during the overlap period of the intake and exhaust valves, which would cause reduced energy efficiency and methanol pollution.

[0046] See also Figure 1 In this embodiment, multiple cylinders 100 are provided. For example, four cylinders 100 are used here. Each cylinder 100 is connected to an air intake 102, and at least two methanol injectors 200 are arranged on each air intake 102. Here, two methanol injectors 200 are used as an example (methanol injector 200A and methanol injector 200B). Of course, in other embodiments, the cylinders 100 can also be set to two, three, five, six, etc., which will not be listed here.

[0047] The intake manifold 300 is connected to multiple intake ducts 102, allowing air to be supplied to each intake duct 102. The methanol manifold 400 is connected to multiple methanol branch pipes 401, each corresponding to a methanol injector 200, allowing methanol to be supplied to each intake duct 102. Each cylinder 100 is connected to an exhaust manifold 500, which is used to discharge exhaust gases from methanol combustion. A turbocharger 600 can also be installed at the intake end 301 of the intake manifold 300 and the exhaust end 501 of the exhaust manifold 500. An intercooler 302 is installed between the intake manifold 300 and the turbocharger 600 to cooperate with the turbocharger 600. As the engine speed increases, the exhaust gas is discharged through the exhaust manifold 500 at a speed that increases in sync with the speed of the turbocharger 600. The turbocharger 600 then compresses more air and sends it through the intake manifold 300 into the cylinder 100. The increased air pressure and density allow for the combustion of more fuel. By increasing the amount of fuel and adjusting the engine speed accordingly, the engine's output power can be increased.

[0048] Different methanol injection rates and positions are used depending on the engine speed and load to ensure that the methanol spray is in the middle of the intake manifold 102, reducing the contact between the methanol spray and the wall of the intake manifold 102. In this embodiment, a pressure sensor is installed on the intake manifold 300 to measure the intake pressure (pressure information) within the intake manifold 300. The methanol injection rate is achieved by controlling the methanol injection pressure. Specifically, since the methanol injection rate is mainly affected by the methanol injection pressure, the air pressure and density within the intake manifold 102, and the structural parameters of the methanol injector 200, and since the structural parameters of the methanol injector 200 are fixed, the intake pressure within the intake manifold 102 (approximately equal to the air pressure within the intake manifold 300) can also be obtained through pressure sensor measurement. When other values ​​remain constant, the methanol injection rate can be calculated using thermodynamic formulas. The methanol main pipe 400 is connected to the methanol tank 403 through the delivery pipe 402. The delivery pipe 402 is equipped with a methanol pump 404 and a methanol pressure regulating valve 405. The methanol injection pressure can be adjusted by the methanol pump 404 and the methanol pressure regulating valve 405, thereby adjusting the methanol injection rate.

[0049] This embodiment also provides a control method for a methanol engine system, which is applied to the above-mentioned methanol engine system, and the specific steps include:

[0050] The first displacement sensor 105 detects the high / low level signal and the missing tooth signal of the crankshaft gear 104, and transmits the high / low level signal and the missing tooth signal to the engine control system. The engine control system calculates the engine crankshaft angle and engine speed in real time based on the high / low level signal and the missing tooth signal. At the same time, the engine control system drives at least one methanol injector 200 on each cylinder 100 to start or stop injection at a specific crankshaft angle. The specific crankshaft angle is determined based on the engine speed and the boost pressure of the intake manifold 300. The boost pressure is calculated from the pressure information detected by the pressure sensor.

[0051] The piston position information is detected by the second displacement sensor 107 and transmitted to the engine control system. The engine control system determines whether the cylinder 100 is in the intake / exhaust stroke or the compression / power stroke based on the position information. When the cylinder 100 is in the intake / exhaust stroke, at least one methanol injector 200 injects methanol into the intake manifold 102 through its nozzle 201. During this process, the intake manifold 300 continuously supplies air into the intake manifold 102. The specific moment is determined by the engine control system based on the engine speed and engine load. The engine load can be obtained by calculating the fuel and methanol injection quantities. For example, in some embodiments, the specific moment can be when the engine crankshaft angle is 360°. Of course, the specific moment can also be any other moment.

[0052] The injection rate of nozzle 201 is adjusted by regulating methanol pump 404 and methanol pressure regulating valve 405, and the methanol injected by nozzle 201 is always kept in the middle position of intake duct 102.

[0053] The engine control system determines the timing of each cylinder of the engine (a mature technology in the prior art), and then injects methanol into the intake manifold 102 at the timing of each cylinder. This ensures that methanol is injected into the intake manifold 102 during periods of high air velocity. By accurately calculating the timing of each cylinder, the timing of methanol injection can be well matched with the changes in intake air velocity, thereby ensuring good mixing and atomization of methanol and achieving the best effect. At the same time, the engine control system adjusts the injection rate and position of methanol according to the engine speed and load, so that the methanol spray is always in the middle of the intake manifold 102, reducing its contact with the wall of the intake manifold 102.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A methanol engine system, characterized in that, include: A cylinder (100) has a compression space inside it. The compression space is connected to an intake passage (102) through a valve (101). The intake passage (102) is also connected to an intake manifold (300). The intake manifold (300) can deliver air into the intake passage (102). At least two methanol injectors (200) are connected to a methanol main pipe (400). Each methanol injector (200) includes a nozzle (201). At least two nozzles (201) are disposed on the air intake (102) and arranged sequentially along the extension direction of the air intake (102). The horizontal distance a between the nozzles (201) and the valve (101) decreases sequentially. The vertical distance d between the nozzles (201) and the inner wall of the air intake (102) decreases sequentially. The nozzles (201) can inject methanol into the air intake (102). The intake manifold (300) is equipped with a pressure sensor for detecting pressure information inside the intake manifold (300). The methanol manifold (400) is connected to the methanol tank (403) through a delivery pipeline (402). The delivery pipeline (402) is equipped with a methanol pump (404) and a methanol pressure regulating valve (405) that can adjust the injection rate of the nozzle (201). Based on the pressure information, the nozzle (201) can be positioned at different locations and / or the injection rate of the nozzle (201) can be adjusted so that the injected methanol is located in the middle of the intake passage (102).

2. The methanol engine system according to claim 1, characterized in that, The cylinder (100) includes a cylinder body and a cylinder head (103), which together form the compression space. The methanol injector (200) is fixed to the cylinder head (103), and the nozzle (201) passes through the cylinder head (103) and is arranged in the intake manifold (102).

3. The methanol engine system according to claim 1, characterized in that, The cylinder (100) includes a crankshaft gear (104) with missing teeth and a crankshaft that is connected to the crankshaft gear (104) in a transmission. The crankshaft gear (104) is provided with a first displacement sensor (105), which is used to detect the high and low level signals and the missing tooth signal of the crankshaft gear (104). The cylinder (100) also includes a camshaft gear (106), on which a second displacement sensor (107) is provided. The second displacement sensor (107) is used to detect the position information of the piston of the cylinder (100), and the piston is connected to the crankshaft drive.

4. The methanol engine system according to claim 3, characterized in that, The methanol engine system also includes an engine control system, which is communicatively connected to the first displacement sensor (105) and the second displacement sensor (107).

5. The methanol engine system according to claim 1, characterized in that, Multiple cylinders (100) are provided, and each cylinder (100) is connected to an air intake (102). At least two methanol injectors (200) are arranged on each air intake (102).

6. The methanol engine system according to claim 5, characterized in that, The main intake pipe (300) is connected to multiple intake ducts (102), and the main intake pipe (300) can deliver air to each of the intake ducts (102).

7. The methanol engine system according to claim 5, characterized in that, The methanol main pipe (400) is connected to multiple methanol branch pipes (401), and each methanol branch pipe (401) is connected to a methanol injector (200) in a corresponding manner. The methanol main pipe (400) can deliver methanol to each of the intake ducts (102).

8. The methanol engine system according to claim 5, characterized in that, Each of the cylinders (100) is connected to an exhaust manifold (500) for discharging exhaust gases from the combustion of methanol.

9. A control method for a methanol engine system, characterized in that, The methanol engine system applied to any one of claims 1-8 includes the following specific steps: The high / low level signal and the missing tooth signal of the crankshaft gear (104) are detected by the first displacement sensor (105), and the high / low level signal and the missing tooth signal are transmitted to the engine control system. The engine control system calculates the engine crankshaft angle and engine speed in real time based on the high / low level signal and the missing tooth signal. At the same time, the engine control system drives at least one methanol injector (200) on each cylinder (100) to start or stop injection at a specific crankshaft angle. The specific crankshaft angle is determined based on the engine speed and the boost pressure of the intake manifold (300). The boost pressure is calculated from the pressure information detected by the pressure sensor. The piston position information is detected by the second displacement sensor (107) and transmitted to the engine control system. The engine control system determines whether the cylinder (100) is in the intake / exhaust stroke or the compression / power stroke based on the position information. When the cylinder (100) is in a specific moment of intake and exhaust stroke, the nozzle (201) of at least one methanol injector (200) injects methanol into the intake manifold (102), and during this process, the intake manifold (300) continuously supplies air into the intake manifold (102); the specific moment is determined by the engine control system based on the engine speed and engine load.

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