Methanol engine combustion system, combustion control method and methanol engine

Abstract

The invention belongs to the technical field of engines, discloses a methanol engine combustion system, a control method and a methanol engine, and realizes more stable combustion during cold start and low-load working condition operation of the methanol engine through a glow plug; alpha is limited to be smaller than beta, and the vortex motion direction in the combustion chamber is the piston circumferential direction from the first reference surface to the second reference surface and passing through the preset plane, so that methanol injected into the combustion chamber through the methanol injection hole corresponding to the first reference surface can be guided by the vortex motion in the combustion chamber, and the methanol can be injected into the combustion chamber. The ignition time of the methanol injected into the combustion chamber from the methanol injection hole corresponding to the first reference surface by the glow plug is shortened, namely, the ignition delay period of the methanol is shortened; and then flame generated by combustion of methanol ignited by the glow plug is utilized to sequentially ignite methanol injected into the combustion chamber from other methanol injection holes, so that controllable combustion of direct injection methanol in the cylinder is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and in particular to a methanol engine combustion system, a combustion control method and a methanol engine. Background Art

[0002] Methanol is a low-carbon, oxygen-containing fuel with the advantages of being green and renewable, having efficient combustion and clean emissions. Methanol is liquid at room temperature and pressure, making it easy to store, transport and refuel. However, methanol's low cetane number and high auto-ignition temperature make it difficult to directly compression ignite it in a compression ignition engine. In addition, methanol's high ignition concentration limit, low vapor pressure and high latent heat of vaporization make it difficult for methanol engines to start cold, especially in low-temperature environments, and are prone to formaldehyde and unburned methanol emissions.

[0003] Currently, several methods exist to promote stable methanol ignition: intake air heating, diesel ignition, pre-combustion chamber jet ignition, and glow plug combustion. Intake air heating, which raises the intake air temperature to above 100°C to ensure stable methanol ignition, consumes a lot of energy, and excessively high intake air temperatures can reduce charging efficiency.

[0004] Diesel ignition requires a diesel injection system, while pre-chamber jet ignition requires a pre-chamber ignition system. This undoubtedly increases engine manufacturing and operating costs and the complexity of the electronic control system. Furthermore, due to the limited cylinder diameter of existing automotive engines, it is difficult to arrange the methanol and diesel injectors, or the pre-chamber, of the diesel injection system on the cylinder head.

[0005] The principle of glow plug combustion is to generate a localized high temperature on the surface of the glow plug's heating element, igniting the surrounding methanol mixture. However, existing glow plug combustion solutions suffer from a long ignition delay period for methanol ignition. Summary of the Invention

[0006] The object of the present invention is to provide a methanol engine combustion system, a combustion control method and a methanol engine, which can shorten the ignition delay period of methanol and achieve controllable and stable combustion of methanol directly injected into the cylinder.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A methanol engine combustion system includes a cylinder liner, a piston axially movably disposed within the cylinder liner, and a cylinder head that, together with the cylinder liner and the piston, forms a combustion chamber. The methanol engine combustion system also includes a methanol injector and a glow plug, both mounted on the cylinder head and each extending into the combustion chamber at one end. The methanol injector is coaxially disposed with the piston, and the glow plug is located radially to one side of the methanol injector. The injection end of the methanol injector has a plurality of methanol injection holes spaced circumferentially apart.

[0009] The central axes of all the methanol injection holes and the central axes of the glow plugs intersect at the same point on the central axis of the piston; the central axes of each methanol injection hole intersect with the central axis of the piston to form a reference plane, and the central axes of the glow plugs and the central axes of the piston intersect to form a predetermined plane;

[0010] Along the circumference of the piston, the preset plane is located between two adjacent reference planes; one of the reference planes adjacent to the preset plane is a first reference plane, and the other reference plane adjacent to the preset plane is a second reference plane. The angle between the first reference plane and the preset plane is α, and the angle between the second reference plane and the preset plane is β, where α<β.

[0011] The first reference plane has the central axis of the piston as its central axis and is rotated by an angle α along the direction of the vortex motion in the combustion chamber to coincide with the preset plane.

[0012] As a feasible implementation plan of the above-mentioned methanol engine combustion system, 5°≤α≤7°.

[0013] As an implementation scheme of the above-mentioned methanol engine combustion system, the plurality of methanol injection holes are arranged at equal intervals along the circumference of the methanol injector;

[0014] and / or, the glow plug is a temperature-controllable glow plug;

[0015] And / or, the compression ratio of the methanol engine is 18-20.

[0016] To achieve the above objectives, the present invention further provides a methanol engine combustion system control method, which is used in the methanol engine combustion system provided by any of the above-mentioned possible implementation schemes; the methanol engine combustion system control method comprises the following steps:

[0017] When the methanol engine is in a medium load condition and / or a high load condition, methanol is injected into the combustion chamber twice through the methanol injector in each working cycle, and the amount of methanol injected into the combustion chamber for the first time is less than the amount of methanol injected into the combustion chamber for the second time;

[0018] The methanol injected into the combustion chamber for the first time is ignited by a flame formed by the combustion of the methanol injected into the combustion chamber for the second time.

[0019] As an implementation method of the above-mentioned methanol engine combustion system control method, when the methanol engine is in a medium load condition, the methanol injected into the combustion chamber for the first time is combusted by ignition by a glow plug or by compression ignition;

[0020] And / or, when the methanol engine is in a high-load operating condition, the methanol injected into the combustion chamber for the first time is combusted by compression ignition.

[0021] As an implementation method of the above-mentioned methanol engine combustion system control method, when the methanol engine is in a medium load condition, the amount of methanol injected into the combustion chamber for the first time accounts for 30% to 40% of the total methanol injection amount in one working cycle;

[0022] And / or, when the methanol engine is in a high-load operating condition, the amount of methanol injected into the combustion chamber for the first time accounts for 10% to 20% of the total amount of methanol injected in one working cycle.

[0023] As an implementable embodiment of the above-mentioned methanol engine combustion system control method, when the methanol engine is in medium load condition and / or high load condition, the time of first injecting methanol into the combustion chamber is 10°CA~20°CA before the top dead center of piston compression, and the time of second injecting methanol into the combustion chamber is 0°CA~5°CA after the top dead center of piston compression.

[0024] As an implementable embodiment of the above-mentioned methanol engine combustion system control method, when the methanol engine is in a low-load condition and / or a cold start condition, methanol is injected into the combustion chamber once through the methanol injector in each working cycle.

[0025] As an implementable embodiment of the above-mentioned methanol engine combustion system control method, the air inlet of the intake manifold of the methanol engine combustion system is provided with a throttle valve; when the methanol engine is in low-load and medium-load conditions, the throttle valve opening is adjusted to make the excess air coefficient 1.5-2, and the glow plug temperature is controlled to be 1200°C-1250°C, and / or, when the methanol engine is in high-load conditions, the throttle valve is controlled to be fully open, so that the excess air coefficient is 1.3-1.7, and the glow plug temperature is controlled to be 1100°C-1150°C.

[0026] To achieve the above objectives, the present invention further provides a methanol engine, comprising a methanol engine combustion system provided by any of the above-mentioned feasible embodiments, or a methanol engine combustion system control method provided by any of the above-mentioned feasible embodiments.

[0027] Beneficial effects of the present invention:

[0028] The methanol engine combustion system and the methanol engine provided by the present invention achieve more stable combustion of the methanol engine during cold start and low load operation through the glow plug. By limiting α<β and the direction of vortex motion in the combustion chamber to the piston circumference from the first reference plane to the second reference plane and passing through the preset plane, when the methanol engine is cold start and low load operation, the methanol injected into the combustion chamber through the methanol injection hole corresponding to the first reference plane can quickly move to the vicinity of the glow plug under the guidance of the vortex motion in the combustion chamber and be ignited by the glow plug, thereby shortening the time for the methanol injected into the combustion chamber through the methanol injection hole corresponding to the first reference plane to be ignited by the glow plug, that is, shortening the ignition delay period of the methanol, and then utilizing the flame generated by the combustion of the methanol ignited by the glow plug to sequentially ignite the methanol injected into the combustion chamber through other methanol injection holes, thereby achieving controllable combustion of the methanol directly injected into the cylinder.

[0029] When the methanol engine operates under medium and high load conditions, a control strategy is adopted to inject methanol into the combustion chamber twice through the methanol injector in each working cycle. The methanol injected into the combustion chamber for the first time ignites first, increasing the temperature in the combustion chamber, which helps to ignite the methanol injected into the combustion chamber for the second time. By distributing the timing of the second methanol injection into the combustion chamber and the methanol injection amount of the two methanol injections, the purpose of controlling the combustion process is achieved, and ultimately the controllable and stable combustion of the methanol directly injected into the cylinder is realized.

[0030] The present invention provides a methanol engine combustion system control method. When the methanol engine is operating under medium and / or high load conditions, methanol is injected into the combustion chamber twice during each working cycle through a methanol injector. A small amount of methanol is injected into the combustion chamber for the first time. After the methanol injected into the combustion chamber first ignites and burns, a large amount of methanol is injected into the combustion chamber for the second time. The flame formed by the combustion of the methanol injected into the combustion chamber for the first time ignites the methanol injected into the combustion chamber for the second time. By injecting methanol into the combustion chamber twice in succession, the temperature in the combustion chamber is increased by the combustion of the methanol injected for the first time, thereby facilitating the ignition of the methanol injected into the combustion chamber for the second time. By allocating the timing of the second injection of methanol into the combustion chamber and the amount of methanol injected for the two injections, the combustion of the methanol engine under medium and / or high load conditions is controlled, so that the thermal efficiency of the methanol engine can reach that of a diesel engine. Moreover, due to the lower combustion temperature of methanol, the methanol engine can significantly reduce NOx emissions compared to diesel and produces almost no soot. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a simplified structural diagram of the methanol engine combustion system provided by the present invention;

[0032] Figure 2 Schematic diagram of the injection of the methanol beam provided by the present invention;

[0033] Figure 3 This is a flame development diagram of the methanol engine provided by the present invention when it is in high-load working condition and adopts a single injection strategy;

[0034] Figure 4 A diagram showing the flame development process of the methanol engine provided by the present invention when it is in a high-load operating condition and adopts a two-injection strategy;

[0035] Figure 5 Cylinder pressure curves of the methanol engine provided by the present invention when it is in high-load working condition and adopts single injection strategy and double injection strategy;

[0036] Figure 6 This is a flame development diagram of the methanol engine provided by the present invention when it is in medium load condition and adopts a two-injection strategy;

[0037] Figure 7 This is a flame development diagram of the methanol engine provided by the present invention when it is in low-load operating condition and adopts a single injection strategy;

[0038] Figure 8 This is a flow chart of the methanol engine combustion system control method provided by the present invention.

[0039] In the picture:

[0040] 1. Cylinder head; 2. Cylinder liner; 3. Piston; 4. Combustion chamber; 41. First reference plane; 42. Second reference plane; 43. Preset plane; 5. Methanol injector; 6. Glow plug; 7. Intake duct; 8. Intake valve; 9. Exhaust duct; 10. Exhaust valve; 11. Intake manifold; 12. Throttle valve. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0042] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0043] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0044] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meanings.

[0045] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a methanol engine combustion system, including a cylinder liner 2, a piston 3 axially movably arranged in the cylinder liner 2, and a cylinder head 1 that forms a combustion chamber 4 with the cylinder liner 2 and the piston 3; the methanol engine combustion system also includes a methanol injector 5 and a glow plug 6, both of which are installed in the cylinder head 1 and one end of each extends into the combustion chamber 4, the methanol injector 5 is coaxially arranged with the piston 3, and the glow plug 6 is located on one radial side of the methanol injector 5. The glow plug 6 is used to heat the mixture in the combustion chamber 4, and the gas in the combustion chamber 4 is a mixture of methanol and air.

[0046] The injection end of the methanol injector 5 has a plurality of methanol injection holes arranged at circumferential intervals; the central axes of all the methanol injection holes and the central axis of the electric glow plug 6 intersect at the same point of the central axis of the piston 3; the central axis of each methanol injection hole intersects with the central axis of the piston 3 to form a reference plane, and the central axis of the electric glow plug 6 and the central axis of the piston 3 intersect to form a preset plane 43.

[0047] Along the circumference of the piston 3, the preset plane 43 is located between two adjacent reference planes; one of the reference planes adjacent to the preset plane 43 is the first reference plane 41, and the other reference plane adjacent to the preset plane 43 is the second reference plane 42. The angle between the first reference plane 41 and the preset plane 43 is α, and the angle between the second reference plane 42 and the preset plane 43 is β, where α<β; the first reference plane 41 has the central axis of the piston 3 as its central axis and is rotated by an angle α along the direction of the vortex motion in the combustion chamber 4 to coincide with the preset plane 43. It should be noted that Figure 2The middle arrow indicates the direction of vortex movement in the combustion chamber 4.

[0048] The glow plug 6 is used to achieve more stable combustion of the methanol engine during cold start and low load operation; by limiting α<β; the direction of the vortex movement in the combustion chamber 4 is from the first reference plane 41 to the second reference plane 42 and through the circumference of the piston 3 of the preset plane 43, so that when the methanol engine is cold started and operated under low load conditions, the methanol injected into the combustion chamber 4 through the methanol injection hole corresponding to the first reference plane 41 can be guided by the vortex movement in the combustion chamber 4 and quickly move to the vicinity of the glow plug 6 and be ignited by the glow plug 6, shortening the time for the methanol injected into the combustion chamber 4 through the methanol injection hole corresponding to the first reference plane 41 to be ignited by the glow plug 6, that is, shortening the methanol ignition delay period, and then using the flame generated by the combustion of the methanol ignited by the glow plug 6 to ignite the methanol injected into the combustion chamber 4 through other methanol injection holes in turn.

[0049] It should be noted that, for an engine, the ignition delay period refers to the period from the start of injection to the formation of the flame center in the cylinder.

[0050] When the methanol engine is operating under medium and high load conditions, a control strategy is adopted to inject methanol twice into the combustion chamber 4 through the methanol injector in each working cycle. The methanol injected into the combustion chamber 4 for the first time ignites first, increasing the temperature in the combustion chamber 4, which helps to ignite the methanol injected into the combustion chamber 4 for the second time. By distributing the timing of the second injection of methanol into the combustion chamber 4 and the methanol injection amount of the two methanol injections, the purpose of controlling the combustion process is achieved, and ultimately controllable and stable combustion of the methanol directly injected into the cylinder is realized.

[0051] In some embodiments, a plurality of methanol injection holes are arranged at equal intervals along the circumference of the methanol injector 5 to improve the uniformity of methanol in the entire combustion chamber 4 , and improve combustion stability and combustion effect.

[0052] The injection point of the methanol oil beam injected from the methanol injection hole on the inner wall of the combustion chamber 4 can refer to the injection point of the diesel oil beam of the basic diesel engine on the inner wall of the combustion chamber 4, for example, they can be on the same horizontal plane.

[0053] In some embodiments, the number of methanol injection holes is 8 to 12. For example, the number of methanol injection holes is 10. It should be noted that the number of methanol injection holes can also be 8, 9, 11, 12, etc., or other numbers such as 6, 7, 13, or 14, etc., depending on the model of the methanol engine, and will not be listed here.

[0054] In some embodiments, 5°≤α≤7°. This configuration allows the methanol injected into the combustion chamber 4 through the methanol injection hole corresponding to the first reference plane 41 to be guided by the vortex motion within the combustion chamber 4 and quickly move to the vicinity of the glow plug 6 and be ignited by the glow plug 6, effectively shortening the time it takes for the methanol injected into the combustion chamber 4 through the methanol injection hole corresponding to the first reference plane 41 to be ignited by the glow plug 6.

[0055] It should be noted that α can select any angle value within the range of greater than or equal to 5° and less than or equal to 7°. For example, α can select any angle value of 5°, 5.1°, 5.2°, 5.3°, 5.4°, 5.5°, 5.6°, 5.7°, 5.8°, 5.9°, 6°, 6.1°, 6.2°, 6.3°, 6.4°, 6.5°, 6.7°, 6.8°, 6.9°, and 7°.

[0056] In some embodiments, the glow plug 6 is a temperature-controllable glow plug, which facilitates adjusting the temperature of the glow plug 6 according to actual needs. It should be noted that the temperature-controllable glow plug is a prior art in the art and will not be described in detail here.

[0057] In some embodiments, the cylinder head 1 is provided with an intake duct 7 and an exhaust duct 9. The intake duct 7 is equipped with an intake valve 8, the intake port of the intake duct 7 being connected to an intake manifold 11, the intake port of the intake manifold 11 being equipped with a throttle valve 12 for regulating the intake air flow rate. The exhaust duct 9 is equipped with an exhaust valve 10. The top surface of the piston 3 is provided with a recess, so that the top surface of the piston 3, the inner circumferential wall of the cylinder liner 2, and the wall of the cylinder head 1 facing the cylinder liner 2 together form the combustion chamber 4.

[0058] In some embodiments, the head of the glow plug 6 is located above the lip of the combustion chamber 4 .

[0059] In some embodiments, the compression ratio of the methanol engine is controlled to be 18-20.

[0060] During the compressor design phase, the engine's compression ratio is increased by adjusting the volume of the recess on the top surface of piston 3. The volume of the recess on the top of piston 3 directly determines the volume of combustion chamber 4 formed between cylinder head 1 and piston 3. The engine's compression ratio refers to the degree to which the gas in combustion chamber 4 is compressed when piston 3 moves from bottom dead center to top dead center.

[0061] It should be noted that the compression ratio of the methanol engine can be any value within the range of greater than or equal to 18 and less than or equal to 20. For example, the compression ratio of the methanol engine can be any value among 18, 18.1, 18.2, 18.3, 18.4, 18.5, 18.6, 18.7, 18.8, 18.9, 19, 19.1, 19.2, 19.3, 19.4, 19.5, 19.6, 19.7, 19.8, 19.9, and 20.

[0062] Designing the methanol engine's compression ratio to 18-20 is equivalent to increasing the engine's compression ratio, increasing the degree of gas compression within the combustion chamber 4 as the piston 3 moves from bottom dead center to top dead center. This effectively increases the overall temperature within the combustion chamber 4, raising the overall temperature within the cylinder and reducing ignition difficulty. Consequently, the temperature required for the glow plug 6 to preheat the mixture can be effectively reduced, effectively reducing the glow plug 6's energy consumption. The most direct factors affecting the lifespan of the glow plug 6 are its surface temperature and the number of times it is switched on and off. Therefore, reducing the temperature required for the glow plug 6 to preheat the mixture can also effectively extend its lifespan.

[0063] Compared with the existing diesel engine combustion system, the methanol engine combustion system provided by the present invention mainly replaces the diesel injector with a methanol injector 5 and is equipped with a glow plug 6. The engine modification is small and the cost increase is less than that of the diesel engine combustion system.

[0064] Figure 3 Figure 3 shows the flame development process for a methanol engine operating under high-load conditions using a single injection strategy. Under high-load conditions, the amount of methanol injected is relatively large. Due to the high latent heat of vaporization, if methanol is injected into combustion chamber 4 once per operating cycle, the methanol vaporizes and absorbs heat, causing the temperature inside combustion chamber 4 to drop. This results in a long ignition delay period for methanol. Consequently, at high compression ratios, the sudden combustion of a large amount of methanol can cause knock in the methanol engine, resulting in a rough and uncontrollable combustion process. Alternatively, the low temperature inside combustion chamber 4 prevents glow plug 6 from igniting the methanol, leading to misfires.

[0065] In order to solve the above technical problems, the present invention also provides a methanol engine combustion system control method for the above methanol engine combustion system.

[0066] The methanol engine combustion system control method comprises the following steps:

[0067] When the methanol engine is operating under medium and / or high load conditions, methanol is injected into the combustion chamber 4 twice via the methanol injector 5 during each operating cycle. The amount of methanol injected into the combustion chamber 4 during the first injection is smaller than the amount injected into the combustion chamber 4 during the second injection. The methanol injected into the combustion chamber 4 during the second injection is ignited by the flame generated by the combustion of the methanol injected during the first injection. It should be noted that one operating cycle of the methanol engine consists of a crankshaft rotation of 720 degrees.

[0068] The methanol engine combustion system control method adopts a high compression ratio. When the methanol engine is in a medium load and / or high load condition, methanol is injected into the combustion chamber 4 twice through the methanol injector 5 in each working cycle. A small amount of methanol is injected into the combustion chamber 4 for the first time. After the methanol injected into the combustion chamber 4 for the first time ignites and burns first, a large amount of methanol is injected into the combustion chamber 4 for the second time. The flame formed by the combustion of the methanol injected into the combustion chamber 4 for the first time ignites the methanol injected into the combustion chamber 4 for the second time.

[0069] By injecting methanol into the combustion chamber 4 twice in succession, the temperature in the combustion chamber 4 is increased by combustion of the methanol injected for the first time, so as to facilitate ignition of the methanol injected into the combustion chamber 4 for the second time. By allocating the timing of the second injection of methanol into the combustion chamber 4 and the injection amount of the methanol for the two injections, the combustion of the methanol engine under medium load and / or high load conditions can be controlled, so that the thermal efficiency of the methanol engine can reach the thermal efficiency of the diesel engine. Moreover, since the combustion temperature of methanol is lower, compared with the use of diesel, the methanol engine can significantly reduce NOx emissions and almost no carbon soot is produced.

[0070] In some embodiments, when the methanol engine is in a high-load operating condition, the methanol injected into the combustion chamber 4 for the first time is burned by compression ignition.

[0071] Figure 4 This diagram illustrates the flame development process for a methanol engine operating under high-load conditions using a two-injection strategy. As can be clearly seen from the accompanying figure, when the methanol engine is operating under high-load conditions, the methanol injected into combustion chamber 4 initially mixes with the air within the combustion chamber 4. The pressure within the combustion chamber 4 is relatively high, and the methanol injected initially into the combustion chamber 4 is directly compression-ignited, forming multiple ignition points within the combustion chamber 4. Methanol is then injected again into the combustion chamber 4. The methanol injected a second time encounters the flame and ignites, forming a diffusion combustion process similar to diesel injection.

[0072] When the methanol engine is in high-load condition, by injecting methanol twice into the combustion chamber 4 in succession, the combustion process of methanol can be controlled, so as to solve the problem of rough combustion or misfire of the engine caused by single injection of methanol.

[0073] Figure 5This is the cylinder pressure curve diagram of the methanol engine under high load conditions using a single injection strategy and a double injection strategy. Figure 5 The curve of two single injections refers to the injection time of one of the single injection strategies as the first injection time of the two injections. Figure 5 The red curve in the figure; the injection time of another single injection strategy is the second injection time of the two injections, see Figure 5 Medium blue curve. Figure 5 It can be seen that the methanol engine will have misfire problems as shown by the red curve, and the methanol engine burns more roughly as shown by the blue curve.

[0074] See Figures 3 to 5 It can be clearly seen that in single injection, the sudden combustion of a large amount of methanol at a high compression ratio will cause detonation in the methanol engine; while in double injection, after one injection, multiple ignition points are formed in the combustion chamber 4, and after the second injection, the methanol diffuses and burns. Compared with a single injection, the increase in cylinder pressure in the double injection is not so obvious, which can effectively solve the detonation problem existing in a single injection.

[0075] In some embodiments, when the methanol engine is in a medium load condition, methanol injected into the combustion chamber 4 for the first time is mixed with the air in the combustion chamber 4 and ignited by the glow plug 6 to cause the methanol injected into the combustion chamber 4 to burn.

[0076] Figure 6 This diagram illustrates the flame development process for a methanol engine operating at medium load, using a double-injection strategy and ignited by glow plug 6. As can be clearly seen from the figure, the flame spreads outward from glow plug 6, forming a circle of flames within combustion chamber 4. Methanol is then injected again into combustion chamber 4. Upon encountering the flame, the methanol injected a second time ignites and burns, creating a diffusion combustion process similar to diesel injection.

[0077] As an alternative, when the methanol engine is in a medium-load condition, the methanol injected into the combustion chamber 4 for the first time can be burned by compression ignition.

[0078] In some embodiments, when the methanol engine is operating at medium load, the amount of methanol injected into the combustion chamber 4 for the first time accounts for 30% to 40% of the total amount of methanol injected during a working cycle. This range was determined through repeated testing. By limiting this ratio range, the flame generated by the combustion of the methanol injected into the combustion chamber 4 for the first time can be effectively utilized to ignite the methanol injected into the combustion chamber 4 for the second time, thereby improving combustion stability and shortening the ignition delay period of the methanol.

[0079] Specifically, when the methanol engine is in medium load condition, the first methanol injection amount injected into the combustion chamber 4 is Q1, and the total methanol injection amount injected into the combustion chamber 4 during one working cycle is Q2. The ratio of Q1 to Q2 can be selected as any value within the range of greater than or equal to 30% and less than or equal to 40%. For example, the ratio of Q1 to Q2 can be any value among 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40%.

[0080] In some embodiments, when the methanol engine is operating at high load, the amount of methanol injected into the combustion chamber 4 for the first time accounts for 10% to 20% of the total amount of methanol injected during a working cycle. This range was determined through repeated testing. By limiting this ratio range, the flame generated by the combustion of the methanol injected into the combustion chamber 4 for the first time can be effectively utilized to ignite the methanol injected into the combustion chamber 4 for the second time, thereby improving combustion stability and shortening the ignition delay period of the methanol.

[0081] Specifically, when the methanol engine is in a high-load condition, the first methanol injection amount injected into the combustion chamber 4 is Q3, and the total methanol injection amount injected into the combustion chamber 4 during one working cycle is Q4. The ratio of Q3 to Q4 can be selected as any value within the range of greater than or equal to 10% and less than or equal to 20%. For example, the ratio of Q3 to Q4 can be any value among 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0082] In some embodiments, when the methanol engine is in medium load and / or high load conditions, the first time methanol is injected into the combustion chamber 4 is 10°CA to 20°CA before the top dead center of compression of the piston 3, and the second time methanol is injected into the combustion chamber 4 is 0°CA to 5°CA after the top dead center of compression of the piston 3.

[0083] When the methanol engine is in a medium load condition and / or a high load condition, the timing of injecting methanol into the combustion chamber 4 twice is limited to achieve a smooth and controllable combustion condition in the combustion chamber 4 .

[0084] In some embodiments, when the methanol engine is in a low-load operating condition and / or a cold start operating condition, methanol is injected into the combustion chamber 4 once through the methanol injector 5 in each working cycle.

[0085] Taking the methanol engine in low load condition as an example, Figure 7 This diagram illustrates the flame development process for a methanol engine operating under low-load conditions using a single-injection strategy. A relatively small amount of methanol is injected into combustion chamber 4, and the methanol injected into combustion chamber 4 is ignited by glow plug 6. This ensures that the methanol in combustion chamber 4 is ignited by glow plug 6, thereby improving the stability of methanol ignition under low-load conditions.

[0086] In some embodiments, when the methanol engine is in low-load and medium-load conditions, the throttle valve 12 is adjusted to open so that the excess air coefficient is 1.5 to 2, and the temperature of the glow plug 6 is controlled to be 1200°C to 1250°C, and / or, when the methanol engine is in high-load conditions, the throttle valve 12 is controlled to be fully open so that the excess air coefficient is 1.3 to 1.7, and the temperature of the glow plug 6 is controlled to be 1100°C to 1150°C.

[0087] By controlling the temperature of the glow plug 6 inside the combustion chamber 4 and the excess air coefficient of the methanol mixture, stable and reliable ignition of the engine under different operating conditions can be achieved.

[0088] The excess air coefficient refers to the ratio of the actual air mass supplied to a unit mass of fuel to the theoretical air mass required for complete combustion of the unit mass of fuel. The temperature of the glow plug 6 refers to the surface temperature of the glow plug 6 .

[0089] In some embodiments, the injection pressure of the methanol injector 5 when injecting methanol into the combustion chamber 4 ranges from 600 bar to 1000 bar. The load of the methanol engine is determined based on the mean effective pressure of the methanol engine. Specifically, when the mean effective pressure of the methanol engine is between 2 bar and 7 bar, the methanol engine is determined to be in a low-load operating condition. When the mean effective pressure of the methanol engine is between 7 bar and 15 bar, the methanol engine is determined to be in a medium-load operating condition. When the mean effective pressure of the methanol engine is between 15 bar and 25 bar, the methanol engine is determined to be in a high-load operating condition.

[0090] The mean effective pressure of a methanol engine refers to the cycle work done per unit cylinder displacement. The method for determining the mean effective pressure of a methanol engine belongs to the prior art in this field and will not be described in detail here.

[0091] Figure 8 FIG. 1 is a flow chart of a method for controlling a methanol engine combustion system according to an embodiment of the present invention. Figure 8 As shown, the methanol engine combustion system control method includes the following steps:

[0092] S100, determining an operating condition of the methanol engine based on an average pressure of the methanol engine;

[0093] S200, the methanol engine is in a cold start condition, and methanol is injected into the combustion chamber 4 once through the methanol injector 5 in each working cycle;

[0094] S300: The methanol engine is in a low-load operating condition, and methanol is injected into the combustion chamber 4 once through the methanol injector 5 in each working cycle;

[0095] S400: The methanol engine is in a medium-load operating condition. Methanol is injected twice into the combustion chamber 4 via the methanol injector 5 during each operating cycle. The methanol injected into the combustion chamber 4 for the first time is combusted by ignition via the glow plug 6. The methanol injected into the combustion chamber 4 for the second time is ignited by the flame formed by the combustion of the methanol injected into the combustion chamber 4 for the first time.

[0096] S500, the methanol engine is in a high-load working condition. In each working cycle, methanol is injected into the combustion chamber 4 twice through the methanol injector 5. The methanol injected into the combustion chamber 4 for the first time is burned by compression ignition, and the methanol injected into the combustion chamber 4 for the second time is ignited by the flame formed by the combustion of the methanol injected into the combustion chamber 4 for the first time.

[0097] An embodiment of the present invention further provides a methanol engine comprising the methanol engine combustion system provided by any of the above embodiments and employing the above methanol engine combustion system control method. The methanol engine has the same technical effects as the above methanol engine combustion system and methanol engine combustion system control method.

[0098] Obviously, the above-described embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A methanol engine combustion system comprising a cylinder liner (2), a piston (3) axially movably disposed in the cylinder liner (2), and a cylinder head (1) which, together with the cylinder liner (2) and the piston (3), forms a combustion chamber (4); characterized in that: The methanol engine combustion system further comprises a methanol injector (5) and a glow plug (6), both of which are mounted on the cylinder head (1) and have one end extending into the combustion chamber (4), the methanol injector (5) being coaxially arranged with the piston (3), and the glow plug (6) being located on one radial side of the methanol injector (5); the injection end of the methanol injector (5) has a plurality of methanol injection holes arranged at intervals in the circumferential direction; The central axes of all the methanol injection holes and the central axis of the glow plug (6) intersect at the same point of the central axis of the piston (3); the central axis of each methanol injection hole intersects with the central axis of the piston (3) to form a reference plane, and the central axis of the glow plug (6) and the central axis of the piston (3) intersect to form a preset plane (43); Along the circumference of the piston (3), the preset plane (43) is located between two adjacent reference planes; one of the reference planes adjacent to the preset plane (43) is a first reference plane (41), and the other reference plane adjacent to the preset plane (43) is a second reference plane (42); an angle between the first reference plane (41) and the preset plane (43) is α, and an angle between the second reference plane (42) and the preset plane (43) is β, where α<β; The first reference plane (41) has the central axis of the piston (3) as its central axis and is rotated by an angle α along the direction of vortex motion in the combustion chamber (4) to coincide with the preset plane (43).

2. The methanol engine combustion system according to claim 1, characterized in that: 5°≤α≤7°。 3. The methanol engine combustion system according to claim 1 or 2, characterized in that: The plurality of methanol injection holes are arranged at equal intervals along the circumference of the methanol injector (5); and / or, the glow plug (6) is a temperature-controllable glow plug; And / or, the compression ratio of the methanol engine is 18-20.

4. A methanol engine combustion system control method, characterized in that: Used for the methanol engine combustion system according to any one of claims 1 to 3; the methanol engine combustion system control method comprises the following steps: When the methanol engine is in a medium load condition and / or a high load condition, methanol is injected into the combustion chamber (4) twice through the methanol injector (5) in each working cycle, and the amount of methanol injected into the combustion chamber (4) for the first time is less than the amount of methanol injected into the combustion chamber (4) for the second time; The methanol injected into the combustion chamber (4) for the first time is burned using a flame formed by the combustion of the methanol.

5. The methanol engine combustion system control method according to claim 4, characterized in that: When the methanol engine is in a medium load condition, the methanol injected into the combustion chamber (4) for the first time is combusted by ignition through a glow plug (6) or by compression ignition; And / or, when the methanol engine is in a high-load operating condition, the methanol injected into the combustion chamber (4) for the first time is combusted by compression ignition.

6. The methanol engine combustion system control method according to claim 4, characterized in that: When the methanol engine is in a medium load condition, the amount of methanol injected into the combustion chamber (4) for the first time accounts for 30% to 40% of the total amount of methanol injected in one working cycle; And / or, when the methanol engine is in a high-load operating condition, the amount of methanol injected into the combustion chamber (4) for the first time accounts for 10% to 20% of the total amount of methanol injected in one working cycle.

7. The methanol engine combustion system control method according to claim 4, characterized in that: When the methanol engine is in a medium load condition and / or a high load condition, the time when methanol is first injected into the combustion chamber (4) is 10°CA to 20°CA before the compression top dead center of the piston (3), and the time when methanol is secondly injected into the combustion chamber (4) is 0°CA to 5°CA after the compression top dead center of the piston (3).

8. The methanol engine combustion system control method according to claim 4, characterized in that: When the methanol engine is in a low-load operating condition and / or a cold start operating condition, methanol is injected into the combustion chamber (4) once through the methanol injector (5) in each working cycle.

9. The methanol engine combustion system control method according to claim 4, characterized in that: The air inlet of the intake manifold (11) of the methanol engine combustion system is provided with a throttle valve (9); when the methanol engine is in a low-load working condition or a medium-load working condition, the opening of the throttle valve (9) is adjusted so that the excess air coefficient is 1.5-2 and the temperature of the glow plug (6) is controlled to be 1200°C-1250°C; and / or, when the methanol engine is in a high-load working condition, the throttle valve (9) is controlled to be fully opened so that the excess air coefficient is 1.3-1.7 and the temperature of the glow plug (6) is controlled to be 1100°C-1150°C.

10. Methanol engine, characterized in that: It comprises the methanol engine combustion system according to any one of claims 1 to 3, or adopts the methanol engine combustion system control method according to any one of claims 4 to 9.

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