Soot and pollutant emission control system of low-speed two-stroke dual-fuel engine with cylinder diameter of 460 mm and control method of soot and pollutant emission control system

Abstract

The invention discloses a soot and pollutant emission control system of a low-speed two-stroke dual-fuel engine with the cylinder diameter of 460 mm and a control method of the soot and pollutant emission control system. A cylinder cover of the engine is provided with a methanol fuel injector and a diesel injector; the included angle between the nozzle axis of the diesel injector and the nozzle axis of the methanol fuel injector is 30 degrees, diesel oil jetted by the diesel injector and methanol oil jetted by the methanol fuel injector are mutually crossed and mixed in the combustion chamber, the fuel injection proportion is controlled according to fuel energy, the injection amount of methanol accounts for 95% of the total fuel energy, and the injection amount of methanol accounts for 5% of the total fuel energy. And the injection amount of the diesel oil accounts for 5% of the total fuel energy. By means of innovative injection system arrangement, an accurate fuel control strategy and an operation parameter range optimized through system experiments, reliable ignition, stable combustion and collaborative emission reduction under high-proportion methanol replacement are achieved, and the system is an existing marine power system.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and more specifically, to a carbon soot and pollutant emission control system and control method for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm. Background Technology

[0002] With increasingly stringent requirements for low-carbon emission reduction in the global shipping industry, traditional low-speed two-stroke diesel engines face immense environmental pressure. Methanol, as a clean and renewable alternative marine fuel, offers advantages such as convenient storage and transportation, high oxygen content, and extremely low sulfur content, and is considered a crucial pathway to decarbonizing the shipping industry. Converting existing diesel engines into methanol dual-fuel engines is a realistic technological choice that balances economic efficiency with emission reduction goals.

[0003] However, achieving stable and efficient combustion of high proportions of methanol fuel in low-speed two-stroke engines faces numerous technical challenges: First, methanol has an extremely high latent heat of vaporization (approximately 1100 kJ / kg), more than four times that of diesel. Its low cetane number (approximately 3-5) makes compression ignition difficult, easily causing excessive evaporative heat absorption and localized low temperatures in the cylinder, leading to unstable combustion, misfires, or even detonation. Second, methanol and diesel have significantly different physicochemical properties, requiring adaptation modifications to the original fuel supply system for corrosion resistance and leak prevention. Third, the organization of methanol combustion is extremely sensitive to in-cylinder mixture formation, ignition, and combustion phase; even small changes in initial intake conditions (temperature and pressure) can lead to significant fluctuations in combustion efficiency and emissions performance.

[0004] Existing dual-fuel conversion solutions mostly focus on hardware adaptation of the fuel supply system or simple fuel substitution, lacking in-depth coupling optimization of methanol fuel characteristics and the working process of low-speed two-stroke engines. In particular, systematic solutions have not yet been formed in the coordinated control of injection system layout, fuel energy ratio, and initial intake conditions, resulting in problems such as decreased combustion efficiency, uneven emission control, and insufficient stability under high load conditions in actual operation.

[0005] Therefore, there is an urgent need to propose a method for methanol dual-fuel conversion of low-speed two-stroke diesel engines. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a carbon soot and pollutant emission control system and control method for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm. Through innovative injection system layout, precise fuel control strategy and operating parameter range optimized by system experiments, reliable ignition, stable combustion and synergistic emission reduction under high proportion of methanol substitution are achieved, providing a practical and feasible technical solution for the green upgrade of existing marine power systems.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A carbon soot and pollutant emission control system for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm is disclosed. The engine is a 6-cylinder engine with a cylinder bore of 460mm, a stroke of 1932mm, a rated speed of 108rpm, and a rated power of 6450kW. The cylinder head of the engine is equipped with fuel injectors configured to inject fuel into the engine's combustion chamber. The fuel injectors are a methanol fuel injector and a diesel fuel injector. The nozzle axis of the diesel fuel injector and the nozzle axis of the methanol fuel injector are in the same plane, and the angle between their nozzle axes is 30°. The diesel fuel jet from the diesel fuel injector and the methanol fuel jet from the methanol fuel injector cross-mix in the combustion chamber, achieving mixed injection of methanol and diesel fuel.

[0009] The present invention also discloses a method for controlling carbon soot and pollutant emissions from a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, using the control system described above; the method includes: injecting methanol into the combustion chamber of the engine at a set injection pressure using a methanol fuel injector, wherein the amount of methanol injected is 95% of the total fuel energy; and injecting diesel fuel into the combustion chamber of the engine at a set injection pressure using a diesel fuel injector, wherein the amount of diesel fuel injected is 5% of the total fuel energy. The diesel fuel jet injected by the diesel fuel injector and the methanol fuel jet injected by the methanol fuel injector cross-mix in the combustion chamber to form a mixed fuel, and the methanol is ignited by the diesel fuel to achieve complete combustion.

[0010] The present invention also discloses a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, including the control system described above.

[0011] Implementing the embodiments of the present invention will have the following beneficial effects: This invention relates to an improved design for a low-speed two-stroke engine with a cylinder bore of 460mm. The engine's cylinder head incorporates both a methanol fuel injector and a diesel fuel injector. The nozzle axes of the diesel and methanol fuel injectors are located in the same plane, forming a 30° angle. This structure allows the diesel fuel jet from the diesel injector and the methanol fuel jet from the methanol fuel injector to cross-mix within the combustion chamber, achieving highly efficient synergistic injection of methanol and diesel fuel.

[0012] This invention further controls the fuel injection ratio according to fuel energy, with methanol injection accounting for 95% of the total fuel energy and diesel injection accounting for 5%. The initial intake air temperature is set to 365K~405K, and the initial intake air pressure is set to 0.403MPa~0.443MPa. Research results show that when the initial intake air temperature increases from 365K to 405K, the ignition delay period can be shortened from 9.5°CA to 5°CA, and the combustion duration is stable and controllable within the range of 12.6°CA to 17°CA. The CA50 phase remains stable, effectively avoiding combustion fluctuations and detonation at low temperatures, and achieving a steady increase in in-cylinder pressure and heat release rate. Within the range of 365K to 385K, the modified NOx emissions are significantly reduced compared to the unmodified diesel engine, with a reduction of 10%~60%. Meanwhile, when the initial intake pressure is controlled at 0.403MPa~0.443MPa, the combustion duration decreases from 17.3°CA to 16.5°CA as the pressure increases, and CA50 remains stable within the range of 13~14°CA, demonstrating good stability in the combustion phase. Under a pressure of 0.413MPa, compared to the original engine, NOx emissions can be reduced by 30.11%, and the peak soot concentration can be reduced by 46.10%, achieving synergistic emission reduction.

[0013] In addition, the engine is equipped with a corrosion-resistant methanol supply pipeline and a methanol fuel injector with a four-hole differentiated design, forming an economical, feasible, efficient and clean dual-fuel conversion solution for low-speed marine engines, providing a key technological path for the low-carbon transformation of the shipping industry. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of diesel spray distribution inside the cylinder of an unmodified diesel engine.

[0015] Figure 2 This is a schematic diagram of the in-cylinder methanol and diesel spray distribution of a 460mm bore low-speed two-stroke engine with methanol-diesel dual fuel system according to the present invention.

[0016] Figure 3 The graph shows the relationship between cylinder pressure and heat release rate at different initial intake temperatures.

[0017] Figure 4 The graph shows the combustion delay period (CA10), combustion duration (CA10-90), and combustion median period (CA50) at different initial intake temperatures.

[0018] Figure 5 For soot and NO at different initial intake temperatures X Emissions analysis chart.

[0019] Figure 6 The graph shows the relationship between cylinder pressure and heat release rate under different initial intake pressures.

[0020] Figure 7 The graph shows the combustion delay period (CA10), combustion duration (CA10-90), and combustion median period (CA50) under different initial intake pressures.

[0021] Figure 8 Soot and NO under different initial inlet pressures X Emissions analysis chart. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0023] This invention discloses a carbon soot and pollutant emission control system for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm. The engine is a 6-cylinder engine with a cylinder bore of 460mm, a stroke of 1932mm, a rated speed of 108rpm, and a rated power of 6450kW. The cylinder head of the engine is equipped with fuel injectors, which are configured to inject fuel into the combustion chamber of the engine. The fuel injectors are methanol fuel injectors and diesel fuel injectors. The nozzle axis of the diesel fuel injector and the nozzle axis of the methanol fuel injector are in the same plane, and the angle between the nozzle axes of the diesel fuel injector and the methanol fuel injector is 30°. The diesel fuel jet from the diesel fuel injector and the methanol fuel jet from the methanol fuel injector cross-mix in the combustion chamber to achieve the mixed injection of methanol and diesel fuel.

[0024] In one specific embodiment, the system is configured to control the fuel injection ratio according to fuel energy, wherein the injection amount of methanol accounts for 95% of the total fuel energy and the injection amount of diesel accounts for 5% of the total fuel energy.

[0025] In one specific embodiment, the injection pressure of the methanol fuel injector is 800 bar to 1000 bar; the injection pressure of the diesel injector is 500 bar to 600 bar.

[0026] In one specific embodiment, the initial intake air temperature of the engine is 365K~405K, and the initial intake air pressure is 0.403MPa~0.443MPa; preferably, the initial intake air temperature is controlled at 375K~395K, and the initial intake air pressure is controlled at 0.413MPa~0.443MPa.

[0027] Specifically, by setting specific initial intake air temperature and pressure, this invention significantly improves the combustion performance of methanol in the cylinder, making the cylinder pressure and heat release rate more stable, improving combustion stability, shortening the ignition delay period and extending the combustion duration, thereby achieving more complete combustion of methanol.

[0028] In one specific embodiment, the diesel injector is connected to a diesel supply unit, the diesel output end of which is connected to the input end of the diesel injector for supplying diesel fuel.

[0029] In one specific embodiment, the methanol fuel injector is connected to a methanol supply unit, and the methanol output terminal of the methanol supply unit is connected to the input terminal of the methanol fuel injector to provide methanol.

[0030] In one specific embodiment, the methanol supply module includes a methanol tank and a methanol supply pipeline; the input end of the methanol supply pipeline is connected to the methanol tank, and the output end of the methanol supply pipeline is connected to a methanol fuel injector.

[0031] In one specific embodiment, the diesel supply module includes a diesel tank and a fuel supply line; the input end of the fuel supply line is connected to the diesel tank, and the output end of the fuel supply line is connected to a diesel injector.

[0032] In one specific embodiment, the alcohol supply pipeline is made of a material resistant to methanol corrosion.

[0033] In one specific embodiment, the alcohol supply pipeline is a double-walled pipe structure.

[0034] In one specific embodiment, the system also includes fuel lubrication and supply equipment configured for methanol fuel.

[0035] In one specific embodiment, the methanol fuel injector adopts a four-hole injector structure, and the diameter of each nozzle is designed differently based on the injection volume of methanol, the injection pressure, and the specific position of the nozzle on the cylinder head.

[0036] The present invention also discloses a method for controlling carbon soot and pollutant emissions of a low-speed two-stroke dual-fuel engine with a cylinder diameter of 460mm, using the control system described above; the method includes: using a methanol fuel injector to inject methanol into the combustion chamber of the engine at a set injection pressure, the amount of methanol injected being 95% of the total fuel energy; using a diesel injector to inject diesel fuel into the combustion chamber of the engine at a set injection pressure, the amount of diesel fuel injected being 5% of the total fuel energy; the diesel fuel jet injected by the diesel injector and the methanol fuel jet injected by the methanol fuel injector cross-mix in the combustion chamber to form a mixed fuel, and using diesel fuel to ignite methanol to achieve complete combustion.

[0037] In one specific embodiment, the injection pressure of the diesel injector is 500 bar to 600 bar; the injection pressure of the methanol fuel injector is 800 bar to 1000 bar.

[0038] In one specific embodiment, the initial intake air temperature of the engine is controlled at 365K~405K, and the initial intake air pressure is controlled at 0.403MPa~0.443MPa; preferably, the initial intake air temperature is controlled at 375K~395K, and the initial intake air pressure is controlled at 0.413MPa~0.443MPa.

[0039] In one specific embodiment, the diesel injection timing is -1°CA and the methanol injection timing is -2.2°CA, where CA represents the crankshaft angle.

[0040] In one specific embodiment, diesel fuel is compressed and ignited, which in turn ignites methanol.

[0041] The present invention also discloses a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, including the control system described above.

[0042] In one specific embodiment, the engine's NOx emissions are 8g / kWh to 20g / kWh, and the peak carbon emission factor is 0.5g / kWh to 5g / kWh.

[0043] This invention also discloses a combustion optimization method for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm. The method includes obtaining data on cylinder pressure, cylinder temperature, and heat release rate based on bench tests; adjusting the injection timing, injection pressure, and injection ratio of methanol and diesel to determine the optimal methanol supply ratio that maximizes combustion efficiency; and generating a dual-fuel injection strategy for diesel and methanol based on this ratio. The method also includes constructing a scavenging control strategy that works in conjunction with the initial intake air temperature and initial intake air pressure to optimize the engine's combustion and emission performance by adjusting the initial intake air temperature and initial intake air pressure.

[0044] The following are specific embodiments. The main parameters of the 460mm bore low-speed two-stroke engine used in the following embodiments are shown in Table 1.

[0045] Table 1. Basic performance parameters of an engine with a 460 mm cylinder bore.

[0046] Example 1 Based on the engine shown in Table 1, this embodiment provides a carbon soot and pollutant emission control system for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460 mm. A fuel injector is installed on the cylinder head of this engine, configured to inject fuel into the engine's combustion chamber. The fuel injector is a methanol fuel injector and a diesel fuel injector. The methanol fuel injector adopts a four-hole nozzle structure.

[0047] The diesel injector is connected to a diesel supply unit, which includes a diesel tank and a fuel supply line. The input end of the fuel supply line is connected to the diesel tank, and the output end is connected to the diesel injector. The methanol fuel injector is connected to a methanol supply unit, which includes a methanol tank and a methanol supply line. The input end of the methanol supply line is connected to the methanol tank, and the output end is connected to the methanol fuel injector.

[0048] The nozzle axis of the diesel injector and the nozzle axis of the methanol fuel injector are in the same plane, and the angle between the nozzle axis of the diesel injector and the nozzle axis of the methanol fuel injector is 30°. The diesel fuel jet sprayed by the diesel injector and the methanol fuel jet sprayed by the methanol fuel injector cross and mix in the combustion chamber to achieve the mixed injection of methanol and diesel fuel.

[0049] The control method using the above system includes: using methanol fuel injectors and diesel injectors respectively, injecting methanol and diesel into the combustion chamber of the engine at a set injection pressure. The amount of methanol injected is 95% of the total fuel energy, and the amount of diesel injected is 5% of the total fuel energy. The diesel fuel jet injected by the diesel injector and the methanol fuel jet injected by the methanol fuel injector cross-mix in the combustion chamber to form a mixed fuel. The diesel fuel is used to ignite the methanol to achieve complete combustion.

[0050] The diesel injector has an injection pressure of 600 bar; the methanol fuel injector has an injection pressure of 800 bar.

[0051] The combustion and emission performance of the engine were analyzed under different initial intake temperatures, with the initial intake pressure set at 0.423 MPa. Figure 3 The graph shows the relationship between cylinder pressure and heat release rate at different initial intake temperatures. Figure 4 The graphs show the combustion delay period (CA10), combustion duration (CA10-90), and median combustion period (CA50) at different initial intake temperatures. Figure 5 For soot and NO at different initial intake temperatures XThe emissions analysis chart shows that the optimal range for initial intake air temperature is 375K to 395K. Within this range, the engine achieves the best balance between combustion stability and emissions performance. Specifically, when the initial temperature is below 375K, methanol vaporization is incomplete, easily leading to unstable combustion. As the initial temperature increases from 365K to 405K, the ignition delay period correspondingly shortens from 9.5°CA to 5°CA and tends to stabilize, while the combustion duration correspondingly lengthens from 12.6°CA to 17°CA and then tends to stabilize. The CA50 phase remains stable, effectively avoiding combustion fluctuations and detonation at low temperatures, and achieving a steady increase in in-cylinder pressure and heat release rate. Within the 365K to 385K range, after modification, NOx emissions are 9g / kWh~13g / kWh, significantly lower than the unmodified diesel engine (14g / kWh~15g / kWh).

[0052] The combustion and emission performance of the engine under different initial intake pressures were analyzed, with the initial intake temperature set at 375K. Figure 6 This is a graph showing the relationship between cylinder pressure and heat release rate under different initial intake pressures. Figure 7 The graphs show the combustion delay period (CA10), combustion duration (CA10-90), and median combustion period (CA50) under different initial intake pressures. Figure 8 Soot and NO under different initial inlet pressures X The emissions analysis chart shows that the preferred range for the initial intake pressure is 0.413 MPa to 0.443 MPa. Within this range, the overall performance of the engine is systematically optimized, specifically: the combustion duration is shortened from 17.3°CA at 0.403 MPa to 16.5°CA at 0.443 MPa, and the CA50 phase is stabilized at 13~14°CA; furthermore, at 0.413 MPa, the NOx emissions in this embodiment are reduced by 30.11% compared to the unmodified diesel engine (14g / kWh~15g / kWh), and the peak soot concentration is reduced by 46.10% compared to the unmodified diesel engine (3g / kWh~5g / kWh), achieving synergistic emission reduction.

[0053] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A carbon soot and pollutant emission control system for a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, characterized in that, The engine is a 6-cylinder engine with a bore of 460mm, a stroke of 1932mm, a rated speed of 108rpm, and a rated power of 6450kW. The cylinder head of the engine is provided with a fuel injector, wherein the fuel injector is configured to inject fuel into the combustion chamber of the engine. The fuel injector is a methanol fuel injector and a diesel fuel injector; The nozzle axis of the diesel injector and the nozzle axis of the methanol fuel injector are in the same plane, and the angle between the nozzle axis of the diesel injector and the nozzle axis of the methanol fuel injector is 30°. The diesel fuel jet sprayed by the diesel injector and the methanol fuel jet sprayed by the methanol fuel injector cross and mix with each other in the combustion chamber to achieve the mixed injection of methanol and diesel fuel.

2. The carbon soot and pollutant emission control system for a 460mm bore low-speed two-stroke dual-fuel engine according to claim 1, characterized in that, The system is configured to control the fuel injection ratio according to fuel energy, wherein methanol accounts for 95% of the total fuel energy and diesel accounts for 5% of the total fuel energy. The injection pressure of the methanol fuel injector is 800 bar to 1000 bar; the injection pressure of the diesel fuel injector is 500 bar to 600 bar. The engine has an initial intake air temperature of 365K~405K and an initial intake air pressure of 0.403MPa~0.443MPa.

3. The carbon soot and pollutant emission control system for a 460mm bore low-speed two-stroke dual-fuel engine according to claim 1, characterized in that, The diesel injector is connected to a diesel supply unit, and the diesel output end of the diesel supply unit is connected to the input end of the diesel injector to provide diesel fuel. The methanol fuel injector is connected to a methanol supply unit, and the methanol output terminal of the methanol supply unit is connected to the input terminal of the methanol fuel injector to supply methanol.

4. The carbon soot and pollutant emission control system for a 460mm bore low-speed two-stroke dual-fuel engine according to claim 1, characterized in that, The methanol supply module includes a methanol tank and a methanol supply pipeline; the input end of the methanol supply pipeline is connected to the methanol tank, and the output end of the methanol supply pipeline is connected to the methanol fuel injector. The diesel supply module includes a diesel tank and a fuel supply line; the input end of the fuel supply line is connected to the diesel tank, and the output end of the fuel supply line is connected to the diesel injector.

5. The carbon soot and pollutant emission control system for a 460mm bore low-speed two-stroke dual-fuel engine according to claim 4, characterized in that, The material of the methanol supply pipeline is resistant to methanol corrosion; The methanol fuel injector adopts a four-hole injector structure.

6. A method for controlling carbon soot and pollutant emissions from a low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, characterized in that, The control system described in any one of claims 1-5 is used; the method includes: injecting methanol into the combustion chamber of the engine at a set injection pressure using a methanol fuel injector, wherein the amount of methanol injected is 95% of the total fuel energy; injecting diesel into the combustion chamber of the engine at a set injection pressure using a diesel injector, wherein the amount of diesel injected is 5% of the total fuel energy, wherein the diesel fuel jet injected by the diesel injector and the methanol fuel jet injected by the methanol fuel injector cross-mix in the combustion chamber to form a mixed fuel, and using diesel to ignite methanol to achieve complete combustion.

7. The method for controlling carbon soot and pollutant emissions from a low-speed two-stroke dual-fuel engine with a 460mm cylinder bore according to claim 6, characterized in that, The injection pressure of the methanol fuel injector is 800 bar to 1000 bar; the injection pressure of the diesel fuel injector is 500 bar to 600 bar. The engine has an initial intake air temperature of 365K~405K and an initial intake air pressure of 0.403MPa~0.443MPa.

8. A low-speed two-stroke dual-fuel engine with a cylinder bore of 460mm, characterized in that, Including as claimed in claim 1 The control system described in any one of the 5.

9. The 460mm bore low-speed two-stroke dual-fuel engine according to claim 8, characterized in that, The engine emits NOx at a rate of 8g / kWh to 20g / kWh and has a peak carbon emission factor of 0.5g / kWh to 5g / kWh.

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