Combustion system of methanol engine with medium-large cylinder diameter, working method and engine

Abstract

The invention discloses a combustion system and a working method of a methanol engine with medium and large cylinder diameters and the engine, and belongs to the technical field of internal combustion engines, the combustion system comprises an electronic control unit, and a methanol supply system, a fuel supply system and an exhaust gas recirculation system which are connected with the electronic control unit; the methanol supply system consists of a high-pressure delivery pump, a high-pressure pipeline, a fuel switching valve group, a high-pressure injection pump, a high-pressure pipeline, a one-way valve and a methanol injector which are connected in sequence; a needle valve in the methanol injector is controlled through a hydraulic system, the medium of the hydraulic system is diesel oil, and the methanol injector is connected with an electronic control unit; the methanol injector is arranged in the center of the cylinder cover, and an intake valve and an exhaust valve are further arranged on the cylinder cover and arranged on the periphery of the methanol injector. The problems that the methanol substitution rate is gradually reduced and the output power of the engine is easily reduced due to high-pressure injection are solved.

Description

Technical Field

[0001] This invention belongs to the field of internal combustion engine technology, specifically relating to a combustion system, working method, and engine for a medium-to-large bore methanol engine. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Methanol engines are gaining increasing attention from the industry and supply chain due to their economic and emission reduction potential. Compared to traditional diesel engines, methanol engines reduce emissions of carbon dioxide, particulate matter, and nitrogen oxides, and produce no sulfur oxides. Currently, methanol engines generally employ low-pressure manifold injection technology, injecting methanol into the intake manifold through an injection valve mounted on the cylinder head's front intake manifold. The methanol mixes with air and then enters the cylinder for combustion. Ignition methods vary, with spark plug ignition and diesel ignition being used. Engines with larger cylinder diameters (≥150mm) typically use diesel ignition, but the methanol substitution rate gradually decreases as engine load increases.

[0004] Meanwhile, existing low-pressure manifold injection technology suffers from poor methanol atomization, which easily leads to concentrated and irregular heat release in the premixed gas, causing abnormal combustion phenomena such as pre-ignition, knocking, and localized overheating, damaging engine hardware. To address these issues, existing technologies employ high-pressure manifold injection, which may improve atomization. However, under high-pressure injection conditions, a large amount of atomized methanol will crowd out the intake space, thereby reducing engine power output. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a combustion system, operating method, and engine for a medium-to-large bore methanol engine, solving the problem of a gradual decrease in methanol substitution rate due to increased engine load, and the problem that methanol in traditional high-pressure injection technology easily leads to a reduction in engine output power.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a combustion system for a medium-to-large bore methanol engine, comprising: a methanol supply system, a fuel supply system, an electronic control unit, and an exhaust gas recirculation system; wherein the electronic control unit is connected to the methanol supply system, the fuel supply system, and the exhaust gas recirculation system respectively, so that the methanol supply system, the fuel supply system, and the exhaust gas recirculation system work together in coordination. The methanol supply system consists of a high-pressure delivery pump, a high-pressure pipeline, a fuel switching valve assembly, a high-pressure injection pump, a high-pressure pipeline, a check valve, and a methanol injector, which are connected in sequence. The needle valve in the methanol injector is controlled by a hydraulic system, the medium of which is diesel oil. The methanol injector is connected to the electronic control unit, and the opening time and duration of the needle valve are controlled by adjusting the pressure of the hydraulic oil in real time. The methanol injector is located at the center of the cylinder head, and the cylinder head is also equipped with an intake valve and an exhaust valve, which are located around the methanol injector.

[0007] As a further implementation, the methanol supply system employs high-pressure injection, with the injection pressure of the methanol injector being 3-60 MPa.

[0008] As a further implementation, the fuel supply system consists of a low-pressure fuel pump, a fuel filter, a high-pressure delivery pump, a high-pressure accumulator, a high-pressure pipeline, and a fuel injector, which are connected in sequence.

[0009] As a further implementation, the fuel injector is connected to the electronic control unit, and the fuel injector is disposed on the upper end or side of the cylinder head.

[0010] As a further implementation, the number of nozzles in the methanol injector and fuel injector is between 6 and 20, the nozzle angle is between 100° and 200°, and the axis of the nozzle forms a set angle with the axis of the methanol injector and fuel injector.

[0011] As a further implementation, the exhaust gas recirculation system includes a recirculation pipeline, a solenoid valve, and a temperature sensor. One end of the recirculation pipeline is connected to a crankcase, and the other end is connected to a turbocharger. The solenoid valve is located at the end of the recirculation pipeline near the crankcase, and the temperature sensor is located in the turbocharger.

[0012] As a further implementation, both the solenoid valve and the temperature sensor are connected to the electronic control unit.

[0013] Secondly, the present invention also provides a method for operating the combustion system of a medium-to-large bore methanol engine, comprising: During startup and low-load conditions, the electronic control unit receives the intake air temperature sensor signal, determines that the temperature is low, adjusts and increases the opening of the solenoid valve to introduce more high-temperature crankcase exhaust gas into the turbocharger to vaporize the methanol fuel. At the same time, the electronic control unit controls the fuel supply system to inject fuel, gradually increasing the temperature inside the cylinder to bring the cylinder to the ignition condition. Under medium to high load conditions, the intake air temperature rises, and the electronic control unit adjusts the opening of the solenoid valve to precisely control the internal temperature of the turbocharger within the set range. The opening signal of the solenoid valve is transmitted to the electronic control unit in real time. The electronic control unit precisely controls the injection pressure and injection pulse width of the methanol injector according to the load requirements. The fuel injector operates at the end of the compression stroke and after methanol injection. The electronic control unit calculates and adjusts the injection timing and pulse width of the ignition fuel in real time based on the current solenoid valve opening and engine load parameters.

[0014] Thirdly, the present invention also provides an engine, including the combustion system described above; further comprising: a combustion chamber, wherein the combustion chamber has a deep pit-type constricted-mouth and large-bellied structure; the ratio of the throat diameter to the cylinder bore of the combustion chamber is controlled between 0.45 and 0.55, and the volume of the deep pit is not less than 60% of the volume of the combustion chamber.

[0015] As a further implementation, the compression clearance of the combustion chamber is the distance between the top surface of the piston and the cylinder head, and the distance is controlled within a set range. The top surface edge of the piston is provided with a guide protrusion to enhance gas turbulence.

[0016] Compared with the prior art, the advantages and positive effects of this invention are: This invention employs an electronic control unit to enable the methanol supply system, fuel supply system, and exhaust gas recirculation system to work in coordination. The needle valve in the methanol injector is controlled by a hydraulic system using diesel fuel as the hydraulic medium. Besides controlling the needle valve's movement, diesel fuel also serves as a lubricant. Methanol, with its low viscosity, provides no lubrication and easily causes wear on the needle valve. Diesel fuel, with its viscosity, provides lubrication, thus improving the reliability of the needle valve. The methanol injector is connected to the electronic control unit to rationally control the timing and quantity of methanol injection, avoiding abnormal combustion phenomena such as pre-ignition and knocking. The opening timing and duration of the needle valve are controlled by adjusting the hydraulic oil pressure in real time. The methanol injector is located in the center of the cylinder head, ensuring uniform distribution of methanol as the main fuel in the combustion chamber. This improves methanol atomization and ensures complete entry of methanol fuel into the cylinder. The fuel injected by the fuel injector in the fuel supply system acts as an ignition source.

[0017] The exhaust gas recirculation system of this invention recirculates exhaust gas from the engine crankcase to the intake system turbocharger, which can further reduce engine emissions and increase engine intake temperature. The engine's compression end temperature is also higher, which promotes better vaporization of methanol when it is injected into the cylinder, and can also offset the latent heat of vaporization absorbed by methanol during the compression stroke. At the same time, the solenoid valve opening signal also serves as the control input signal for the needle valve in the fuel injector, reasonably adjusting the needle valve opening pressure and control pulse width to ignite the methanol and air mixture with a smaller amount of ignition diesel injection, thereby achieving a higher methanol substitution rate.

[0018] The fuel injector of the present invention is connected to an electronic control unit to reasonably control the timing and amount of fuel injection, avoiding abnormal combustion phenomena such as pre-ignition and knocking. The fuel injector is located on the upper end or side of the cylinder head. The fuel injector is arranged on the upper end or side of the cylinder head and between the intake valve and the exhaust valve, and is provided with an inclined angle to ensure that the fuel jet has a certain injection depth and width range after injection, so as to ensure that the fuel jet is more fully mixed with the methanol and air mixture in the cylinder, and achieves a better ignition effect. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a cross-sectional view showing the relative positions of the cylinder head, methanol injector, and fuel injector of the present invention. Figure 2 This is a top view of the cylinder head, methanol injector, and fuel injector of the present invention.

[0021] In the diagram: 1. Methanol injector; 2. Cylinder head; 3. Fuel injector; 4. Combustion chamber; 5. Intake valve; 6. Exhaust valve. Detailed Implementation

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. Example 1 This embodiment provides a combustion system for a medium-to-large bore methanol engine, such as... Figures 1-2 As shown, it includes: a methanol supply system, a fuel supply system, an electronic control unit, and an exhaust gas recirculation system; the electronic control unit is connected to the methanol supply system, the fuel supply system, and the exhaust gas recirculation system respectively, so that the methanol supply system, the fuel supply system, and the exhaust gas recirculation system work together in coordination. The methanol supply system consists of a high-pressure delivery pump, a high-pressure pipeline, a fuel switching valve group, a high-pressure injection pump, a high-pressure pipeline, a check valve, and a methanol injector 1, which are connected in sequence. The needle valve in the methanol injector 1 is controlled by a hydraulic system, the medium of which is diesel oil. The methanol injector 1 is connected to the electronic control unit to reasonably control the timing and amount of methanol injection, avoiding abnormal combustion phenomena such as pre-ignition and knocking. The opening timing and duration of the needle valve are controlled by adjusting the pressure of the hydraulic oil in real time. The methanol injector 1 is located at the center of the cylinder head 2. The cylinder head 2 is also equipped with an intake valve 5 and an exhaust valve 6, which are located around the methanol injector 1. The methanol injector 1 is located in the middle of the cylinder head, ensuring that methanol, as the main fuel, is evenly distributed in the combustion chamber 4. This improves the methanol atomization effect and ensures that the methanol fuel completely enters the cylinder. The fuel injected by the fuel injector 3 in the fuel supply system plays an ignition role. The needle valve of the methanol injector 1 is controlled by hydraulic control. The opening time and duration of the needle valve are controlled by adjusting the pressure of the hydraulic oil in real time to achieve a better control effect of the methanol injector 1. In addition to controlling the needle valve action, the hydraulic medium is diesel oil, which can also be used as lubricating oil for the needle valve. Since methanol has low viscosity and no lubricating effect, it is easy to cause wear of the needle valve. Diesel oil has a certain viscosity and can play a lubricating role, thereby improving the reliability of the needle valve.

[0024] As a further implementation, the methanol supply system adopts high-pressure injection, and the injection pressure of the methanol injector 1 is 3-60MPa, which can ensure the amount of methanol injected per unit time and make reasonable and effective adjustments to the methanol injection pressure and duration, thereby improving the engine's operating condition response capability and power adjustment range.

[0025] As a further implementation, the fuel supply system consists of a low-pressure fuel pump, a fuel filter, a high-pressure delivery pump, a high-pressure accumulator, a high-pressure pipeline, and a fuel injector 3, which are connected in sequence. The fuel injector 3 is connected to the electronic control unit to reasonably control the fuel injection timing and injection quantity, avoiding abnormal combustion phenomena such as pre-ignition and knocking. The fuel injector 3 is located on the upper end or side of the cylinder head 2. The fuel injector 3 is arranged on the upper end or side of the cylinder head 2 and between the intake valve 5 and the exhaust valve 6, with an inclined angle, which can ensure that the fuel jet has a certain injection depth and width range after injection, ensuring that the fuel jet is more fully mixed with the methanol and air mixture in the cylinder, achieving a better ignition effect.

[0026] As a further implementation, the number of orifices in the methanol injector 1 and the fuel injector 3 is between 6 and 20, and the orifice angle is between 100° and 200°. The axis of the orifice forms a set angle with the axis of the methanol injector 1 and the fuel injector 3. This is used to disperse methanol and fuel into fine jets, increasing the contact area between the fuel gas and air.

[0027] As a further implementation, the exhaust gas recirculation system includes a recirculation pipeline, a solenoid valve, and a temperature sensor. One end of the recirculation pipeline is connected to the crankcase, and the other end is connected to the turbocharger. The solenoid valve is located at the end of the recirculation pipeline near the crankcase, and the temperature sensor is located in the turbocharger. Both the solenoid valve and the temperature sensor are connected to the electronic control unit. Specifically, the exhaust gas recirculation system recirculates the exhaust gas from the engine crankcase to the intake system turbocharger, which can further reduce engine emissions and increase the engine intake air temperature. The higher compression end temperature allows for a higher methanol substitution rate with lower ignition energy. The recirculation pipeline, temperature sensor, and solenoid valve are arranged from the crankcase to the turbocharger to connect the crankcase exhaust gas with the turbocharger; the exhaust gas temperature is generally greater than 100°C. During actual engine operation, the intake air temperature is fed back to the electronic control unit (ECU). Upon receiving the temperature signal, the ECU controls the opening of the solenoid valve. The crankcase exhaust gas raises the overall temperature of the engine's intake system, increasing the cylinder charging temperature. When methanol is injected into the cylinder, it promotes better vaporization of the methanol and simultaneously counteracts the latent heat of vaporization absorbed by the methanol during the compression stroke. The solenoid valve opening signal can also serve as the control input signal for the needle valve within the fuel injector 3. By appropriately adjusting the needle valve opening pressure and control pulse width, a smaller amount of ignition diesel fuel can be injected to ignite the methanol-air mixture, achieving a higher methanol substitution rate.

[0028] Example 2 This embodiment provides a method for operating the combustion system of a medium-to-large bore methanol engine, including: During startup and under low load conditions, the electronic control unit receives a signal from the intake air temperature sensor, determines that the temperature is low, and adjusts to increase the opening of the solenoid valve to introduce more high-temperature crankcase exhaust gas into the turbocharger to vaporize the methanol fuel. At the same time, the electronic control unit controls the fuel supply system to inject fuel, gradually increasing the temperature inside the cylinder to bring it to the ignition condition. Utilizing the high-temperature environment created by the exhaust gas recirculation system, the smallest possible amount of ignition fuel is used, i.e., an extremely short pulse width or a slightly low opening pressure, so that the diesel fuel can quickly complete compression ignition after injection and form a stable ignition core, thereby reliably igniting the surrounding premixed methanol-air mixture.

[0029] Under medium to high load conditions, the intake air temperature rises. The electronic control unit (ECU) adjusts the opening of the solenoid valve to precisely control the internal temperature of the turbocharger within a set range. The opening signal of the solenoid valve is transmitted to the ECU in real time. The ECU precisely controls the injection pressure and injection pulse width of the methanol injector 1 according to the load requirements. The fuel injector 3 operates at the end of the compression stroke, after methanol injection. The ECU calculates and adjusts the injection timing and pulse width of the ignition fuel in real time based on the current solenoid valve opening and engine load parameters. In the engine's combustion system, methanol serves as the primary fuel, providing most of the engine's energy. Under the precise control of the ECU, the fuel supply system completes the ignition task with the minimum necessary fuel quantity, achieving a high methanol substitution rate, high efficiency, and low emissions. The exhaust gas recirculation system also simultaneously suppresses the formation of nitrogen oxides.

[0030] Example 3 This embodiment provides an engine, including the aforementioned combustion system; it also includes a combustion chamber 4, which has a deep-pit, constricted-mouth, large-bellied structure; the ratio of the throat diameter to the cylinder bore of the combustion chamber 4 is controlled between 0.45 and 0.55, and the volume of the deep pit is not less than 60% of the volume of the combustion chamber 4; during the intake and compression processes, it can effectively guide the airflow movement, forming strong tumble and squeeze flows. During the intake stroke, after the air enters the combustion chamber 4, it forms a stable tumble flow under the action of the deep pit and constriction, enhancing the air turbulence; at the end of the compression stroke, the constriction structure causes the gas at the edge of the combustion chamber 4 to be squeezed towards the central deep pit, and the tumble and squeeze flows are coupled to form a complex and strong three-dimensional turbulent field, which promotes the mixing of fuel gas and air and improves combustion efficiency.

[0031] As a further implementation, the compression clearance of the combustion chamber 4 is the distance between the top surface of the piston and the cylinder head, and the distance is controlled within a set range. A guide protrusion is provided on the edge of the piston's top surface to enhance gas turbulence. It is understood that the compression clearance can generate a certain amount of airflow turbulence during compression, further breaking up the edge of the gas jet, refining the gas particles, and promoting mixing. The guide protrusion on the piston's top surface edge can guide the airflow in the compression clearance to flow in a specific direction, enhancing the turbulence effect on the gas jet and improving the uniformity of the mixture.

[0032] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A combustion system for a medium-to-large bore methanol engine, characterized in that, include: The system includes a methanol supply system, a fuel supply system, an electronic control unit, and an exhaust gas recirculation system. The electronic control unit is connected to the methanol supply system, the fuel supply system, and the exhaust gas recirculation system, respectively, so that the methanol supply system, the fuel supply system, and the exhaust gas recirculation system work together in coordination. The methanol supply system consists of a high-pressure delivery pump, a high-pressure pipeline, a fuel switching valve assembly, a high-pressure injection pump, a high-pressure pipeline, a check valve, and a methanol injector, which are connected in sequence. The needle valve in the methanol injector is controlled by a hydraulic system, the medium of which is diesel oil. The methanol injector is connected to the electronic control unit, and the opening time and duration of the needle valve are controlled by adjusting the pressure of the hydraulic oil in real time. The methanol injector is located at the center of the cylinder head, and the cylinder head is also equipped with an intake valve and an exhaust valve, which are located around the methanol injector.

2. The combustion system of a medium-to-large bore methanol engine as described in claim 1, characterized in that, The methanol supply system employs high-pressure injection, with the methanol injector having an injection pressure of 3-60 MPa.

3. The combustion system of a medium-to-large bore methanol engine as described in claim 1, characterized in that, The fuel supply system consists of a low-pressure fuel pump, a fuel filter, a high-pressure delivery pump, a high-pressure accumulator, high-pressure pipelines, and fuel injectors, which are connected in sequence.

4. The combustion system of a medium-to-large bore methanol engine as described in claim 3, characterized in that, The fuel injector is connected to the electronic control unit and is located on the upper end or side of the cylinder head.

5. The combustion system of a medium-to-large bore methanol engine as described in claim 4, characterized in that, The number of nozzles in the methanol injector and fuel injector is between 6 and 20, and the nozzle angle is between 100° and 200°. The axis of the nozzle is at a set angle to the axis of the methanol injector and fuel injector.

6. The combustion system of a medium-to-large bore methanol engine as described in claim 1, characterized in that, The exhaust gas recirculation system includes a recirculation pipeline, a solenoid valve, and a temperature sensor. One end of the recirculation pipeline is connected to the crankcase, and the other end is connected to a turbocharger. The solenoid valve is located at the end of the recirculation pipeline near the crankcase, and the temperature sensor is located in the turbocharger.

7. The combustion system of a medium-to-large bore methanol engine as described in claim 6, characterized in that, Both the solenoid valve and the temperature sensor are connected to the electronic control unit.

8. The method for operating the combustion system of a medium-to-large bore methanol engine as described in any one of claims 2-7, characterized in that, include: During startup and low-load conditions, the electronic control unit receives the intake air temperature sensor signal, determines that the temperature is low, adjusts and increases the opening of the solenoid valve to introduce more high-temperature crankcase exhaust gas into the turbocharger to vaporize the methanol fuel. At the same time, the electronic control unit controls the fuel supply system to inject fuel, gradually increasing the temperature inside the cylinder to bring the cylinder to the ignition condition. Under medium to high load conditions, the intake air temperature rises, and the electronic control unit adjusts the opening of the solenoid valve to precisely control the internal temperature of the turbocharger within the set range. The opening signal of the solenoid valve is transmitted to the electronic control unit in real time. The electronic control unit precisely controls the injection pressure and injection pulse width of the methanol injector according to the load requirements. The fuel injector operates at the end of the compression stroke and after methanol injection. The electronic control unit calculates and adjusts the injection timing and pulse width of the ignition fuel in real time based on the current solenoid valve opening and engine load parameters.

9. An engine, characterized in that, The combustion system includes the combustion system as described in any one of claims 2-7; it further includes a combustion chamber, wherein the combustion chamber has a deep pit-type constricted-mouth and large-belly structure; the ratio of the throat diameter to the cylinder diameter of the combustion chamber is controlled between 0.45 and 0.55, and the volume of the deep pit is not less than 60% of the volume of the combustion chamber.

10. An engine as described in claim 9, characterized in that, The compression clearance of the combustion chamber is the distance between the top surface of the piston and the cylinder head, and the distance is controlled within a set range. The top surface edge of the piston is provided with a guide protrusion to enhance gas turbulence.

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