Combustion chamber structure for a methanol engine

Abstract

The utility model relates to the technical field of engine, and disclose a combustion chamber structure of methanol engine, including setting in the cylinder liner for forming the combustion chamber piston and cylinder cover, install on the cylinder cover intake tract, exhaust passage, spark plug, still install on the cylinder cover for the methanol injection methanol nozzle to the combustion chamber, the concave opening one side of piston has the split ridge opposite methanol nozzle, the upper end one side of piston is provided with the boss, the inner side of boss has the jet lip backflow area that is connected with the upper end of split ridge and is concave setting, the inner wall of the concave of piston is annular concave structure and is connected with the lower end of split ridge and forms the combustion chamber concave backflow area, the utility model discloses through the split ridge of piston, jet lip backflow area and combustion chamber concave backflow area, guide methanol jet to form directional flow, and multiple tumble is all in the combustion chamber inside circulation, avoids with cylinder liner wall surface direct contact, effectively reduced the cylinder liner corrosion rate, solved the core problem of methanol corrosion.

Description

Technical Field

[0001] This utility model relates to the field of engine technology, specifically to a combustion chamber structure for a methanol engine. Background Technology

[0002] A methanol engine is an internal combustion engine that uses methanol as its primary fuel. Its main advantages include minimal modification to the original engine and lower atmospheric pollution. Methanol is a liquid fuel, and its storage and transportation can utilize petroleum fuel storage and transportation systems, thus requiring less infrastructure investment. This technology promotes carbon neutrality and achieves the goals of safe, reliable, sustainable, clean, and low- (or zero-)carbon energy.

[0003] In the combustion scenarios of methanol engines (such as passenger car and commercial vehicle power systems), traditional combustion chamber structures, due to design flaws, struggle to resolve the contradiction between methanol fuel corrosion and low combustion efficiency. Specific problems include: 1. Methanol directly contacts the cylinder liner, resulting in a high corrosion rate. Traditional methanol engines use an intake manifold premixing method. After methanol is mixed with air, it fills the intake manifold and combustion chamber, directly contacting the cylinder liners. The formic acid in methanol (content of about 1%) and the formaldehyde generated by combustion will accelerate the corrosion of the cylinder liners, thus leading to a shortened engine life. 2. Uneven air-fuel mixture distribution leads to low combustion efficiency. Traditional intake manifold mixing makes it difficult to precisely control the air-fuel ratio of each cylinder, with deviations often reaching ±15%, resulting in localized overly rich or lean conditions. Uneven air-fuel ratios may lead to excessive emissions of unburned methanol. 3. There is a risk of backfire, resulting in poor safety. The intake manifold is filled with a methanol-gas mixture. Backfire (flame rushing back into the intake manifold) is likely to occur during valve overlap. Backfire may cause the intake manifold to rupture, increasing maintenance costs. To avoid backfire, traditional engines need to reduce the valve overlap angle, resulting in insufficient scavenging, increased residual exhaust gas coefficient, further deteriorating combustion, and creating a vicious cycle. 4. Difficult to adapt to multiple operating conditions, limiting strategy control. Traditional premixing methods cannot flexibly adjust the methanol injection quantity and timing according to operating conditions. When idling, the mixture is too lean, resulting in unstable idling speed. When idling at high speed, the power is reduced due to delayed fuel supply, resulting in a very poor user experience.

[0004] With the implementation of China VI and above emission standards, traditional structures can no longer meet the requirements of environmental protection and economy. There is an urgent need to design and develop an engine that can achieve direct injection of methanol fuel in the cylinder, break through the application bottleneck of methanol engines, and meet market needs. Utility Model Content

[0005] To address the technical problems existing in the background art, this utility model proposes a combustion chamber structure for a methanol engine.

[0006] The present invention proposes a combustion chamber structure for a methanol engine, including a piston and a cylinder head disposed within a cylinder liner to form a combustion chamber, wherein an intake manifold, an exhaust manifold, and a spark plug are mounted on the cylinder head. The cylinder head is also equipped with a methanol nozzle for injecting methanol into the combustion chamber. The piston has a flow-diverting ridge on one side of the recess opening, which is opposite to the methanol nozzle. A boss is provided on the upper side of the piston. The inner side of the boss has a jet lip recirculation area that is connected to the upper end of the flow-diverting ridge and is recessed. The inner wall of the piston recess has an annular concave structure and is connected to the lower end of the flow-diverting ridge to form the combustion chamber recess recirculation area. To address the issues of methanol fuel's tendency to corrode cylinder liners and the low efficiency of traditional intake air mixing methods, this structure achieves highly efficient corrosion-resistant combustion through a "directional jet + recirculation zone design." The methanol nozzle directly injects methanol into the combustion chamber, and the flow divider guides the jet to the recirculation zone at the jet lip and the recirculation zone in the combustion chamber recess, preventing the fuel from directly contacting the cylinder liner and significantly reducing the corrosion rate. The boss and the recirculation zone work together to constrain the airflow path, ensuring that the fuel circulates inside the combustion chamber, thus resolving the contradiction between methanol corrosion and combustion efficiency.

[0007] As a further optimization of this utility model, the diversion ridge, the jet lip recirculation zone, and the combustion chamber pit recirculation zone are connected to form an inclined ω-shaped auxiliary combustion chamber, which reduces the area of ​​the squeeze zone by 22%. The design of the inclined ω-shaped auxiliary combustion chamber, while maintaining a certain vortex, introduces multiple tumble flows, which greatly improves turbulent kinetic energy, accelerates the heat release of combustion, and increases the flame propagation speed in the combustion chamber, thereby improving the actual combustion efficiency and thermal efficiency. Moreover, the multiple tumble flow design also makes the airflow movement more intense, the fuel and air mix more evenly, reduces the air-fuel ratio deviation, and avoids incomplete combustion caused by local over-richness.

[0008] As a further optimization of this utility model, when the methanol jet collides with the splitting ridge, the methanol jet undergoes a first separation and is divided into two parts. The first part of the methanol jet moves upward along the jet wall and forms a first tumble in the return zone of the jet lip. The second part of the methanol jet moves downward along the jet wall and forms a second tumble in the return zone of the combustion chamber pit. The second tumble collides a second time in the piston pit and separates a portion of the methanol jet again, which then returns to the combustion chamber to form a third tumble. The formation of multiple tumbles avoids direct contact between the methanol fuel and the cylinder liner, reducing cylinder liner corrosion. The three-stage tumble design constructs a "contactless combustion" mode: the first tumble forms an upper vortex in the jet lip recirculation zone, the second tumble forms a lower vortex in the combustion chamber recess recirculation zone, and the third tumble achieves full-domain circulation through secondary collisions. The contact rate between fuel and cylinder liner wall is greatly reduced, and the tumble motion can also wash away residual formic acid and formaldehyde, further reducing the risk of corrosion.

[0009] As a further optimization of this utility model, the methanol jet forms three methanol gas vortices after two collisions and separations. The three methanol gas vortices are located in the combustion chamber pit, the jet lip recirculation area, and the combustion chamber pit recirculation area, respectively. Three gas vortices ensure uniform fuel distribution throughout the combustion chamber: the vortex in the combustion chamber recess ensures the concentration in the main combustion zone, the vortex in the jet lip recirculation zone enhances the mixture concentration near the spark plug, which is beneficial for ignition, and the vortex in the combustion chamber recess recirculation zone replenishes fuel in the edge area, which greatly improves combustion efficiency and reduces unburned methanol emissions.

[0010] As a further optimization of this utility model, the angle α between the methanol jet of the methanol nozzle and the piston combustion chamber axis is 75°, which ensures that the jet accurately hits the splitting ridge, reduces energy loss, and stabilizes the fuel separation ratio. This angle allows the jet to maintain kinetic energy at the end of the compression stroke, avoiding premature collision with the wall, thus adapting to different speed conditions.

[0011] As a further optimization of this utility model, both the boss and the piston are made of aluminum alloy and are integrally formed, which greatly improves the connection strength between the boss and the piston, and can withstand higher combustion pressure. The aluminum alloy material is lightweight, reducing the reciprocating inertial force, while having good thermal conductivity, avoiding methanol decomposition caused by local overheating, thereby reducing the amount of formaldehyde generated.

[0012] The combustion chamber structure of the methanol engine proposed in this utility model has the following beneficial effects: (i) By using the piston's flow divider ridge, the jet lip return zone, and the combustion chamber recess return zone, the methanol jet is guided to form a directional flow. The methanol jet ejected from the methanol nozzle first collides and separates with the flow divider ridge. One part forms the first tumble along the jet lip return zone, and the other part forms the second tumble along the combustion chamber recess return zone. The remaining part collides with the combustion chamber recess a second time to form the third tumble. All three tumbles circulate inside the combustion chamber, avoiding direct contact with the cylinder liner wall, effectively reducing the cylinder liner corrosion rate and solving the core problem of methanol corrosion. (ii) The diversion ridge, the jet lip recirculation zone and the combustion chamber pit recirculation zone together form an inclined ω-shaped structure, which reduces the area of ​​the squeeze zone. While maintaining the vortex, double tumble flow is introduced, which greatly increases the turbulent kinetic energy. The tumble flow accelerates the flame propagation speed and shortens the combustion duration, thereby improving the actual thermal efficiency. At the same time, the methanol gas vortex is evenly distributed in the three regions, which makes the actual combustion more complete and helps to reduce the amount of unburned methanol emissions, which meets the requirements of low carbon and environmental protection. (iii) The angle between the methanol nozzle jet and the combustion chamber axis is 75°. This angle allows the jet to accurately hit the splitting ridge, ensuring that the fuel is evenly distributed into each recirculation zone after separation. The uniformity of fuel distribution is greatly improved. Moreover, the methanol nozzle is used for methanol injection feeding, which avoids the safety hazards caused by traditional intake pipe premixing. It is also conducive to controlling the air-fuel ratio deviation of each cylinder and avoiding combustion instability caused by local over-rich or over-lean conditions, thereby effectively improving power density. (iv) The boss and piston are integrally formed of aluminum alloy, which greatly improves mechanical strength and can withstand higher combustion pressure. The jet lip return area on the inner side of the boss further constrains the tumble path, reduces energy loss, and avoids mechanical interference between the piston and cylinder head, thereby improving operational reliability. (v) This structure is designed specifically for direct injection in the cylinder. By adjusting the injection timing and injection quantity of methanol, it can flexibly adapt to different working conditions such as idling, high speed, and high load. Compared with the traditional intake manifold mixing method, it eliminates the risk of backfire of the mixture in the intake manifold, greatly improves safety, and does not require modification of the original engine basic structure, thus reducing the modification cost. (vi) Through efficient combustion and corrosion protection design, this structure can give full play to the low carbon advantage of methanol fuel, while reducing harmful emissions such as formaldehyde and formic acid, meeting the National VI and above emission standards, and providing core technical support for the promotion of new energy engines.

[0013] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0014] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a three-dimensional cross-sectional structural diagram of the present invention; Figure 3 This is a front sectional view of the present invention. Figure 4 This is a three-dimensional structural diagram of the piston of this utility model.

[0015] Figure descriptions: 1. Piston; 11. Flow divider ridge; 12. Jet lip recirculation area; 13. Combustion chamber recess recirculation area; 2. Cylinder head; 3. Intake manifold; 4. Exhaust manifold; 5. Spark plug; 6. Methanol nozzle; 7. Boss. Detailed Implementation

[0016] The embodiments of this utility model are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols 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 this utility model, and should not be construed as limiting this utility model.

[0017] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0018] Please see Figures 1-4 This invention provides a combustion chamber structure for a methanol engine. Addressing issues such as the easy corrosion of cylinder liners by methanol fuel and the low efficiency of traditional air-fuel mixing methods, the combustion chamber employs an innovative design of "direct injection + directional flow field control + multi-recirculation zone synergy." The core consists of a piston 1, a cylinder head 2, and supporting injection and ignition components. Through the flow-dividing ridge 11 on the piston top, the jet lip recirculation zone 12, and the combustion chamber recess recirculation zone 13, the methanol jet is guided to form a three-stage tumble flow, achieving highly efficient combustion where "fuel does not contact the cylinder liner," while simultaneously improving mixing uniformity and combustion efficiency.

[0019] Specifically, traditional intake manifold premixing methods can easily lead to direct contact between methanol and cylinder liners, resulting in a corrosion rate as high as 0.1 mm / year. This structure, through directional jet control, reduces the contact rate between methanol and cylinder liners by 80%, and lowers the corrosion rate to below 0.02 mm / year.

[0020] Furthermore, the ω-type auxiliary combustion chamber design reduces the squeezing area by 22% compared to the traditional structure, increases turbulent kinetic energy by 30%, accelerates flame propagation speed to 40m / s, and improves combustion efficiency from 32% to 38%.

[0021] Specifically, piston 1 and boss 7 are integrally formed by low-pressure casting using ZL114A high-strength aluminum alloy. The top of the piston is heat-treated with T6, achieving a hardness of HB120-140, ensuring that it will not deform at a combustion temperature of 180℃.

[0022] Furthermore, the flow divider ridge 11 is located at the edge of the piston recess opening, with rounded corners at both ends to avoid the jet impact generating vortex dead zones. The surface of the flow divider ridge is sprayed with an Al2O3 ceramic coating (thickness 50μm, porosity <1%), which improves the methanol corrosion resistance by 5 times, while reducing the surface roughness to Ra0.8μm and reducing fuel adhesion.

[0023] Furthermore, the jet lip return zone 12 is an arc-shaped concave structure on the inner side of the boss 7, which smoothly transitions with the upper end of the splitting ridge through rounded corners to form a flow guiding channel. When the methanol jet hits the splitting ridge, 30% of the flow moves upward along this channel to form the first tumble (flow velocity 18-22m / s). The center of the tumble is ≤8mm away from the spark plug electrode 5, ensuring that the local air-fuel ratio is stable at 1.2-1.4 (λ value) during ignition.

[0024] Furthermore, the combustion chamber recess recirculation zone 13 is an annular inclined structure on the inner wall of the piston recess. 70% of the methanol jet from the splitting ridge moves downward along this area to form a second tumble (flow velocity 12-15 m / s). Some of the tumble bounces off the bottom of the combustion chamber recess and mixes with the surrounding air to form a third tumble (covering 60% of the combustion chamber edge area), thus avoiding localized excessive leaning.

[0025] Specifically, the methanol nozzle 6 adopts a side-mounted oblique spray layout, with the nozzle axis and the combustion chamber center axis forming an angle of 75°±0.5°, ensuring that the jet trajectory is accurately pointed to the middle of the split ridge 11 (deviation ≤0.5mm). The injection pressure of the methanol nozzle 6 is adjustable from 18-25MPa, and the injection duration can be adjusted within 0.5-5ms, adapting to idle speed of 800rpm to high speed of 6000rpm. The nozzle head extends out of the bottom surface of the cylinder head and is a certain straight distance from the split ridge to avoid fuel adhering to the cylinder head surface during injection.

[0026] Specifically, intake manifold 3 has a double-helix structure (vortex ratio 2.8), which forms a clockwise vortex in the cylinder and creates a "cross vortex" with the counterclockwise tumble of the methanol jet to accelerate mixing. Exhaust manifold 4 adopts a symmetrical branch design, with exhaust back pressure ≤45kPa (at 4000rpm), ensuring rapid discharge of combustion exhaust gas. The intake and exhaust valve diameters are 35mm and 30mm respectively, with a valve overlap angle of 12°, reducing the escape of unburned methanol during scavenging.

[0027] Specifically, the flow divider ridge 11, the jet lip recirculation zone 12, and the combustion chamber recess recirculation zone 13 are connected to form an inclined ω-shaped structure with an overall depth of 35 mm, a maximum diameter of 85 mm, a compression ratio of 12.5:1 (compression final pressure 1.8 MPa), and a combustion chamber surface-to-volume ratio of 8.2 m³ / s. 1 Compared to traditional flat-bottom combustion chambers, it reduces heat loss from the walls by 12%. The minimum distance between the piston top and the cylinder head bottom is 1.2mm, which creates a strong squeezing flow at the end of the compression stroke, promoting secondary mixing of methanol vapor and air.

[0028] During use, methanol is ejected from the nozzle at a pressure of 20 MPa, forming a continuous jet. After flying for 1.5 ms, it impacts the middle of the splitting ridge 11. At this time, the jet kinetic energy is converted into upward and downward velocity components. The upper airflow climbs along the jet lip return zone 12 and is constrained by the boss 7 to form a clockwise first tumble. A high-concentration gas vortex with a diameter of about 20 mm is formed around the spark plug. The lower airflow moves downward along the combustion chamber pit return zone 13 to form a counterclockwise second tumble, covering the bottom area of ​​the pit. Part of the airflow in the second tumble impacts the bottom of the pit and mixes with the air vortex entering from the intake duct to form a third tumble circulating along the edge of the combustion chamber, so that the methanol concentration in the edge area is maintained at 8-10%, avoiding incomplete combustion caused by local excessive leaning. Spark plug 5 generates 80mJ of ignition energy, rapidly igniting the high-concentration air-fuel mixture in the first tumble stream, forming a 3mm diameter flame core. The airflow in the first tumble stream accelerates the flame's propagation outwards, sequentially igniting the mixtures in the second and third tumble streams. The combustion pressure reaches its peak at 10°CAATDC. The synergistic effect of the three tumble streams ensures the flame front evenly covers the entire combustion chamber, achieving a combustion rate of 0.04kg / (m³). 3 •s), 90% of the combustion heat release is completed before 30°C CAATDC, and the third tumble continuously washes the edge of the combustion chamber, so that the remaining small amount of unburned methanol is fully burned, and the exhaust temperature is controlled at 650-700°C to avoid NOx generation caused by excessively high temperature.

[0029] In summary, this combustion chamber structure, through precise flow field control and corrosion-resistant design, perfectly solves the core pain points of methanol engines and can be widely used in passenger cars, commercial vehicles and other fields, providing reliable technical support for the large-scale application of methanol fuel.

[0030] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A combustion chamber structure for a methanol engine, comprising a piston (1) and a cylinder head (2) disposed within a cylinder liner to form a combustion chamber, wherein an intake manifold (3), an exhaust manifold (4), and a spark plug (5) are mounted on the cylinder head (2), characterized in that: The cylinder head (2) is also equipped with a methanol nozzle (6) for injecting methanol into the combustion chamber. The piston (1) has a flow divider ridge (11) on one side of the recess opening that is opposite to the methanol nozzle (6). The piston (1) has a boss (7) on one side of the upper end. The inner side of the boss (7) has a jet lip recirculation area (12) that is connected to the upper end of the flow divider ridge (11) and is recessed. The inner wall of the piston (1) has an annular concave structure and is connected to the lower end of the flow divider ridge (11) to form a combustion chamber recess recirculation area (13).

2. The combustion chamber structure of a methanol engine according to claim 1, characterized in that, The flow divider ridge (11), the jet lip recirculation zone (12), and the combustion chamber pit recirculation zone (13) are connected to each other to form an inclined ω-shaped auxiliary combustion chamber.

3. The combustion chamber structure of a methanol engine according to claim 1, characterized in that, When the methanol jet collides with the splitting ridge (11), the first separation occurs, and the methanol jet is divided into two parts. The first part of the methanol jet moves upward along the jet wall and forms the first tumble in the jet lip recirculation zone (12). The second part of the methanol jet moves downward along the jet wall and forms the second tumble in the combustion chamber pit recirculation zone (13). The second tumble collides twice in the pit of the piston (1) and separates a portion of the methanol jet again, which recirculates in the combustion chamber to form the third tumble.

4. The combustion chamber structure of a methanol engine according to claim 3, characterized in that, After two collisions and separations, the methanol jet forms three methanol gas vortices, which are located in the combustion chamber pit, the jet lip recirculation zone (12), and the combustion chamber pit recirculation zone (13), respectively.

5. The combustion chamber structure of a methanol engine according to claim 1, characterized in that, The angle between the methanol jet from the methanol nozzle (6) and the combustion chamber axis of the piston (1) is α = 75°.

6. The combustion chamber structure of a methanol engine according to claim 1, characterized in that, Both the boss (7) and the piston (1) are aluminum alloy products and are integrally formed.

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