Design method for combustion system of methanol-diesel double direct injection compression ignition engine

Abstract

The invention provides a methanol-diesel double direct injection compression ignition engine combustion system design method which comprises the following steps: establishing a methanol-diesel circulating injection quantity function based on a target methanol substitution rate to obtain a methanol circulating injection quantity and a diesel circulating injection quantity, parameters of a combustion system are designed according to the methanol circulating injection amount and the diesel circulating injection amount; a three-dimensional thermodynamic simulation model is constructed based on the design parameters, and a three-dimensional simulation result is obtained through simulation calculation; a combustion heat release rate in a pure diesel oil mode is simulated based on a multi-Weber function, the heat release rate is introduced into one-dimensional thermodynamic simulation software to obtain a pure diesel oil calibration model, and a methanol-diesel oil double direct injection simulation model is established based on the calibration model. And according to the three-dimensional simulation result, carrying out one-dimensional double-fuel-injection performance simulation verification on the methanol-diesel double-direct-injection simulation model. The relation between the small methanol substitution rate and the combustion system is concerned, the heat value of the fuel can be brought into play to a great extent, and the heat efficiency and output power of the engine are improved.

Description

Technical Field

[0001] This application belongs to the technical field of engines, and particularly relates to a design method for a combustion system of a methanol-diesel dual direct injection compression ignition engine. Background Technique

[0002] With the implementation of the national dual-carbon strategy, engines, as one of the main carbon emission sources, are gradually using low-carbon fuels to reduce carbon emissions. Among them, methanol, as a green and low-carbon fuel, has gradually become one of the alternative fuels.

[0003] Currently, for the combustion method with a medium and small methanol substitution rate, a secondary injector is usually added to the original single-injector cylinder head to inject methanol, and the injection scheme is matched with the combustion chamber scheme. However, the method of injecting methanol into the intake port will cause methanol to accumulate near the valve and not enter the cylinder. At the same time, it will corrode the valve components. Therefore, how to design the corresponding combustion system to meet the engine's demand for a medium and small methanol substitution rate is the biggest problem faced in this field. Summary of the Invention

[0004] In view of this, this application aims to propose a design method for a combustion system of a methanol-diesel dual direct injection compression ignition engine. This method focuses on the relationship between the medium and small methanol substitution rate and the combustion system, and can greatly exert the calorific value of the fuel, improve the thermal efficiency and output power of the engine.

[0005] To achieve the above object, the technical solution of this application is realized as follows: This application provides a design method for a combustion system of a methanol-diesel dual direct injection compression ignition engine, including: Establish a methanol-diesel cyclic injection quantity function based on the set target methanol substitution rate to obtain the methanol cyclic injection quantity and the diesel cyclic injection quantity, where the target methanol substitution rate is a medium and small methanol substitution rate; Design the parameters of the combustion system according to the methanol cyclic injection quantity and the diesel cyclic injection quantity, including: setting the methanol injection timing and the methanol injection duration, selecting the fuel injection types of the top-mounted injector and the side-mounted injector, and designing the spray holes of the top-mounted injector and the side-mounted injector and the combustion chamber; Construct a three-dimensional thermodynamic simulation model based on the design parameters, and obtain three-dimensional simulation results through simulation calculation; Simulate the combustion heat release rate in the pure diesel mode based on the multi-Wiebe function, and bring the heat release rate into a one-dimensional thermodynamic simulation software to obtain a pure diesel calibration model. Based on this calibration model, establish a methanol-diesel dual direct injection simulation model, and perform one-dimensional dual-injection performance simulation verification on the methanol-diesel dual direct injection simulation model according to the three-dimensional simulation results.

[0006] Further, the methanol cyclic injection quantity function is as follows: ; The diesel fuel cycle injection quantity function is as follows: ; In the formula, is the methanol fuel cycle injection quantity, is the diesel fuel cycle injection quantity in pure diesel mode, is the target methanol substitution rate, is the lower heating value of methanol, is the lower heating value of diesel fuel, is the diesel fuel cycle injection quantity.

[0007] Furthermore, the methanol injection timing is from the intake valve closing time to 20°CA before top dead center, the methanol injection duration is in the range of 0 - 30°CA, and the methanol injection pressure is not less than 60 Mpa; The overhead injector is a diesel injector, and the side injector is a methanol injector.

[0008] Furthermore, the nozzle diameter of the overhead diesel injector is smaller than that of the diesel injector in pure diesel mode. There are two side methanol injectors. Among them, the included angle between the center line of one side methanol injector and the cylinder center line is set in the range of 0° - 45°, and the included angle between the center line of the other side methanol injector and the cylinder center line is set in the range of 45° - 90°; In response to the included angle between the center line of the side methanol injector and the cylinder center line being in the range of 0° - 45°, the included angle formed between the nozzle on the same side of the side injector and the injector center line is greater than the included angle formed between the nozzle on the opposite side of the side injector and the injector center line; In response to the included angle between the center line of the side methanol injector and the cylinder center line being in the range of 45° - 90°, the included angle formed between the nozzle on the same side of the side injector and the injector center line is less than the included angle formed between the nozzle on the opposite side of the side injector and the injector center line.

[0009] Furthermore, the diameter of the nozzle on the opposite side of the side injector is smaller than that of the nozzle on the same side.

[0010] Furthermore, the shape of the combustion chamber at least includes a shallow basin type, a quasi - hemispherical type, and an asymmetric pit type.

[0011] Furthermore, multiple Wiebe functions are used to fit multiple heat release rate curves to simulate the heat release rate in pure diesel mode. The heat release rate simulated by the multiple Wiebe functions is used as the input and brought into a one - dimensional thermodynamic simulation software for simulation. By adjusting the model parameters, a calibration model in pure diesel mode is obtained; Based on the calibration model, a methanol-diesel dual direct injection simulation model is established. The methanol-diesel dual direct injection simulation model is simulated through three-dimensional simulation results. Among them, the methanol-diesel dual direct injection simulation model provides boundary conditions for the three-dimensional thermodynamic simulation model, and the three-dimensional simulation results feed back to the methanol-diesel dual direct injection simulation model to verify the performance of the one-dimensional dual fuel injectors.

[0012] Compared with the prior art, the design method of a methanol-diesel dual direct injection compression ignition engine combustion system described in this application has the following beneficial effects: The design method of a methanol-diesel dual direct injection compression ignition engine combustion system described in this application designs and matches the corresponding combustion system according to the particularity of medium and small methanol substitution rates. By focusing on the relationship between medium and small methanol substitution rates and the combustion system, and being dedicated to a specific engine, it can maximize the calorific value of the fuel and improve the thermal efficiency and output power of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings: Figure 1 is a flowchart of the design method of a methanol-diesel dual direct injection compression ignition engine combustion system according to an embodiment of this application; Figure 2 is a schematic diagram comparing the simulated cylinder pressure and the experimental cylinder pressure according to an embodiment of this application; Figure 3 is the fuel reverse flow phenomenon caused by recent stage alcohol injection according to an embodiment of this application; Figure 4 is a schematic diagram of the relative position of the dual fuel injectors with medium and small methanol substitution rates according to an embodiment of this application; Figure 5 is a schematic diagram of the layout scheme of the side-mounted methanol fuel injector according to an embodiment of this application; Figure 6 is a three-dimensional simulation diagram of the influence of different spray hole angles of the side-mounted methanol fuel injector on in-cylinder combustion ignition according to an embodiment of this application; Figure 7 is a schematic diagram of the spray hole scheme of the side-mounted methanol fuel injector according to an embodiment of this application; Figure 8 is a schematic diagram comparing the spray hole settings of the top-mounted fuel injector according to an embodiment of this application; Figure 9 is a schematic diagram of the design change of the combustion chamber profile according to an embodiment of this application; Figure 10 is a three-dimensional simulation diagram of the influence of different piston combustion chamber profiles on the mixing degree of the in-cylinder mixture according to an embodiment of this application; Figure 11 Schematic diagram of multi-Weber curve coupling according to an embodiment of the present application; Figure 12 Schematic diagram of the injection timing of a small methanol substitution rate on the valve lift curve according to an embodiment of the present application; Detailed implementation manners

[0014] To make the objectives, technical solutions, and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to specific embodiments and the accompanying drawings.

[0015] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the ordinary meanings understood by those of ordinary skill in the field to which the present application belongs. The terms "first", "second", and similar terms used in the embodiments of the present application do not indicate any order, quantity, or importance, but are only used to distinguish different components. The terms "including" or "comprising" and the like mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms "connected" or "coupled" and the like are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0016] Please refer to Figure 1 As shown, this embodiment provides a design method for a combustion system of a methanol-diesel dual direct injection compression ignition engine, which specifically includes the following steps: Step S101: Establish a methanol-diesel cyclic injection quantity function based on a set target methanol substitution rate to obtain the methanol cyclic injection quantity and the diesel cyclic injection quantity, where the target methanol substitution rate is a medium and small methanol substitution rate.

[0017] Specifically, in this embodiment, the injection quantities of the two fuels are calculated according to the target substitution rate. The substitution rate determines the proportion of methanol and diesel in the total energy, which directly affects the power output, combustion characteristics, and emissions of the engine.

[0018] Among them, the methanol cyclic injection quantity function is as follows: The diesel cyclic injection quantity function is as follows: In the formula, is the methanol cyclic injection quantity, is the diesel cyclic injection quantity in the pure diesel mode, is the target methanol substitution rate, is the lower heating value of methanol in theory, is the lower heating value of diesel in theory, is the diesel cycle injection quantity.

[0019] Dynamically allocate the injection quantities of methanol and diesel through medium and small methanol substitution rates, ensure the equivalence of dual-fuel energy input, provide a combustion system design benchmark for subsequent steps, and make the simulation results more accurate.

[0020] Step S102: Design the parameters of the combustion system according to the methanol cycle injection quantity and the diesel cycle injection quantity, including: setting the methanol injection timing and the methanol injection duration, selecting the fuel injection types of the top-mounted injector and the side-mounted injector, and designing the nozzle holes of the top-mounted injector and the side-mounted injector and the combustion chamber.

[0021] Specifically, in this embodiment, for the combustion system facing medium and small methanol substitution rates, select the methanol injection timing in the low-pressure compression stage (i.e., from the intake valve closing moment to 20 °CA before top dead center), and the methanol injection duration is selected according to the methanol injection timing. To ensure the mixing effect of methanol and air, the duration is selected in the range of 10 - 30 °CA, and the methanol injection pressure is selected according to the in-cylinder environment of the engine and the methanol injection duration, generally not less than 60 Mpa.

[0022] As Figure 2 shown, within the 720 °CA crankshaft angle, it includes the intake lift, the exhaust lift, and the intake and exhaust overlap period. Adopting medium and small methanol substitution rates, the methanol injection timing is selected in the pure compression stage, that is, from intake closing to 20 °CA before top dead center, Figure 3 then shows the fuel reverse flow phenomenon caused by methanol injection in the intake stage. Therefore, methanol fuel cannot be injected in the intake stage.

[0023] As Figure 4 shown, for the fuel injection types, the top-mounted injector selected in this embodiment is a diesel injector, and the side-mounted injector is a methanol injector.

[0024] According to the positions of the dual injectors, carry out the design of the nozzle hole scheme of the side-mounted methanol injector, and the specific description is as follows: As Figure 5As shown, the side-mounted methanol injector forms a certain angle with the cylinder center line. Therefore, the conventional symmetric nozzle design cannot meet the purpose of achieving a quasi-uniform distribution of methanol in the combustion chamber, and an asymmetric nozzle angle needs to be designed. Generally, when the center line of the side-mounted injector and the cylinder center line are within the range of 0° to 45°, on the same side of the side-mounted injector, the nozzle should have a larger angle with the injector center line, and on the opposite side of the side-mounted injector, the nozzle should have a smaller angle with the injector center line; when the center line of the side-mounted injector and the cylinder center line are within the range of 45° to 90°, on the same side of the side-mounted injector, the nozzle should have a smaller angle with the injector center line, and on the opposite side of the side-mounted injector, the nozzle should have a larger angle with the injector center line. It should be noted that the above-mentioned larger / smaller should match the combustion chamber pit on the same side.

[0025] Figure 6 The influence of the change in the nozzle included angle on the in-cylinder mixture is given. It can be seen the influence of different nozzle angles on the methanol spray mixing and combustion. In the figure, the abscissa represents the crankshaft rotation angle value, and the ordinate represents the nozzle angle. As the nozzle angle increases, the in-cylinder mixture and flame development are better; Since methanol is injected into the cylinder before diesel, methanol will absorb a large amount of heat during the atomization and evaporation process, reducing the in-cylinder temperature and causing difficulty in atomizing diesel during the injection process; at the same time, since a part of diesel is replaced by methanol, the cyclic injection quantity of diesel decreases. Considering the above two aspects, the nozzle diameter of the diesel injector should be smaller than that of the diesel injector in the pure diesel mode of this engine, and the specific aperture should match the in-cylinder heat atmosphere and combustion of this engine.

[0026] At the same time, as Figure 7 shown, on the same side of the side-mounted injector, the nozzle aperture should be smaller, as can be seen Figure 7 in the side spray hole 1 in the middle. On the opposite side of the side-mounted injector, the nozzle aperture should be larger, as can be seen Figure 7 in the opposite side spray hole 2 in the middle.

[0027] According to the positions of the dual injectors, the nozzle scheme design of the top-mounted methanol injector is carried out, and the specific description is as follows: As Figure 8 shown, since methanol is injected into the cylinder before diesel, methanol will absorb a large amount of heat during the atomization and evaporation process, reducing the in-cylinder temperature and causing difficulty in atomizing diesel during the injection process; at the same time, since a part of diesel is replaced by methanol, the cyclic injection quantity of diesel decreases. Considering the above two aspects, the current nozzle diameter of the diesel injector (as can be seen Figure 8 in the spray hole 2 in the middle) should be smaller than the original nozzle diameter of the diesel injector in the pure diesel mode of this engine (as can be seen Figure 8 in the spray hole 1 in the middle), and the specific aperture should match the in-cylinder heat atmosphere and combustion of this engine. The sizes of the spray holes in the figure are for illustration purposes and do not represent the actual sizes.

[0028] In addition, in this embodiment, the intake port shape design is also carried out to increase the tumble flow inside the cylinder, including but not limited to straight ports, helical ports, tangential ports, etc.

[0029] The combustion chamber profile design is carried out to improve the mixing uniformity of methanol and air, and the specific description is as follows: To ensure that the fuel of the side-mounted methanol injector can be evenly distributed in the two ω-shaped pits on both sides, it is necessary to reduce the height of the boss, optimize the depth of the ω-pit, and conduct three-dimensional flow simulation analysis.

[0030] If reducing the height of the boss cannot meet the quasi-uniform distribution of methanol, the combustion chamber profile can be further designed into a shallow-basin type, and the depth of the ω-pit is optimized to further reduce the problem of uneven methanol spray mixing caused by the height of the boss, and three-dimensional flow simulation analysis is carried out.

[0031] If the shallow-basin type piston combustion chamber profile cannot meet the quasi-uniform distribution of methanol, the combustion chamber profile can be further designed into a quasi-hemispherical type, and three-dimensional flow simulation analysis is carried out.

[0032] If the quasi-hemispherical type combustion chamber profile cannot meet the quasi-uniform distribution of methanol, the combustion chamber profile can be further designed into an asymmetric structure, the center line of the piston design is moved towards the side away from the side-mounted methanol injector, the concave pit on the same side as the side-mounted methanol injector becomes shallower, and the concave pit on the opposite side of the side-mounted methanol injector becomes deeper to create a tumble flow effect and strengthen the distribution of methanol spray in the combustion chamber.

[0033] Figure 9 Schematic diagram of the change in the combustion chamber profile design, where the dashed line (1) represents reducing the height of the boss, and the combustion chamber profile remains ω-shaped; the dashed line (2) represents the combustion chamber profile changing from ω-shaped to shallow-basin type; the dashed line (3) represents the combustion chamber profile changing from shallow-basin type to quasi-hemispherical type; the dotted line (4) represents the combustion chamber profile changing from quasi-hemispherical type to asymmetric type.

[0034] Figure 10 Shows the influence of the change in the combustion chamber profile on the in-cylinder fuel-air mixture: from left to right are the ω-shaped, shallow-basin, and quasi-hemispherical combustion chamber profiles. At the same crankshaft rotation angle, the mixing degree in the cylinder of the hemispherical type is the best, and the ω-shaped is the worst. However, there is still the right half part of the hemispherical type, that is, the combustion chamber mixing on the side away from the side-mounted methanol injector is poor, and an asymmetric combustion chamber profile can be further designed.

[0035] Step S103: Construct a three-dimensional thermodynamic simulation model based on the design parameters, and obtain three-dimensional simulation results through simulation calculations.

[0036] Specifically, in this embodiment, a three-dimensional thermodynamic simulation model is constructed based on the above design parameters (including setting the alcohol injection timing and duration, selecting the fuel injection types of the overhead injector and side injector, and designing the injection holes of the overhead injector and side injector and the combustion chamber). Three-dimensional simulation requires accurate injection quantity as input parameters to simulate the real spray, mixing, and combustion processes. Errors in the injection quantity will lead to inaccurate simulation of fuel distribution, combustion speed, and emission generation in the three-dimensional simulation, thus affecting the optimization results. It should be noted here that the three-dimensional thermodynamic simulation model uses existing mature simulation models, and the specific construction process will not be elaborated too much.

[0037] Step S104: Simulate the combustion heat release rate in the pure diesel mode based on the multi-Wiebe function, and substitute the heat release rate into the one-dimensional thermodynamic simulation software to obtain the pure diesel calibration model. Based on this calibration model, establish a methanol-diesel dual direct injection simulation model, and conduct one-dimensional dual injection performance simulation verification on the methanol-diesel dual direct injection simulation model according to the three-dimensional simulation results.

[0038] Specifically, in this embodiment, the multi-Wiebe function represents the combustion model and can describe the heat release law during the combustion process. Its mathematical expression is specifically: = In the formula, represents the heat release rate, , , represent the model parameters, represents the crankshaft angle.

[0039] As Figure 11 shown, a zero-dimensional combustion model is constructed based on the multi-Wiebe function to calculate the heat release rate curve. By adjusting the proportion of different Wiebe curves, the required heat release rate curve is finally obtained. The multi-Wiebe function is used to fit the heat release rate curve to determine the model parameters and verify the fitting accuracy to ensure that the model can accurately describe the combustion characteristics of pure diesel.

[0040] Figure 12 shows the comparison of the cylinder pressure obtained by establishing the simulation model using the multi-Wiebe function and the experimental cylinder pressure. The fitting degree of the two curves is very high, verifying the feasibility of this scheme.

[0041] Select a one-dimensional heat transfer simulation software (such as GT-Power, AVL BOOST, etc.), and establish an engine model of pure diesel combustion in the software, including the cylinder, intake and exhaust systems, fuel injection system, etc. Substitute the heat release rate simulated by the multi-Wiebe function as the input and conduct simulation in the one-dimensional model. By adjusting the model parameters (such as combustion efficiency, heat transfer coefficient, etc.), make the simulation results coincide with the actual experimental data. The calibrated model is the calibration model of the pure diesel mode.

[0042] Based on the pure diesel calibration model, a methanol injection system is added, and the injection parameters of methanol and diesel (such as injection timing, injection pressure, injection quantity, etc.) are set to establish a methanol-diesel dual direct injection simulation model. Since the combustion characteristics of methanol and diesel are different, the combustion model needs to be adjusted. For example, the combustion speed of methanol is relatively fast, and it may be necessary to adjust the parameters of the heat release rate model.

[0043] Use a three-dimensional simulation software (such as CONVERGE, ANSYS Fluent, etc.) to simulate the methanol-diesel dual direct injection system, and obtain detailed data of the combustion process (such as temperature field, pressure field, emission distribution, etc.). According to the three-dimensional simulation results, optimize the combustion parameters in the one-dimensional model to verify whether the one-dimensional model can accurately predict the performance of the methanol-diesel dual direct injection system.

[0044] The design method of the combustion system of the methanol-diesel dual direct injection compression ignition engine described in this application is based on the demand for medium and small methanol substitution rates, and is calibrated for the theoretical working cycle and the multi-Weber combustion model to obtain the in-cylinder pressure and temperature in the pure diesel mode; based on the substitution rate demand, the methanol injection timing and injection pressure are designed, and the nozzle hole schemes of the top-mounted injector and side-mounted injector and the combustion chamber matching scheme are matched. Using three-dimensional simulation software, the combustion system design is completed, and finally the one-dimensional dual injector performance simulation verification is carried out. This method matches the corresponding combustion system according to different methanol substitution rates, is dedicated to a special machine, and can give full play to the calorific value of the fuel to a greater extent, improving the thermal efficiency and output power of the engine.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the specification of the present invention.

[0046] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the embodiments of this application shall be included within the protection scope of this application.

Claims

1. A methanol-diesel dual direct injection compression ignition engine combustion system design method, characterized in that: include: A methanol-diesel cycle injection amount function is established based on a set target methanol substitution rate to obtain a methanol cycle injection amount and a diesel cycle injection amount, wherein the target methanol substitution rate is a small and medium methanol substitution rate; The parameters of the combustion system are designed according to the methanol cycle injection amount and the diesel cycle injection amount, including: setting the methanol injection time and the duration of the methanol injection, selecting the fuel injection type of the overhead injector and the side injector, and designing the injection holes and the combustion chamber of the overhead injector and the side injector; Constructing a three-dimensional thermodynamic simulation model based on the design parameters, and obtaining a three-dimensional simulation result through simulation calculation; The combustion heat release rate in pure diesel mode is simulated based on the multi-Weber function, and the heat release rate is introduced into the one-dimensional thermodynamic simulation software to obtain a pure diesel calibration model. A methanol-diesel dual direct injection simulation model is established based on the calibration model. According to the three-dimensional simulation results, a one-dimensional dual injection performance simulation verification is performed on the methanol-diesel dual direct injection simulation model.

2. The method according to claim 1, characterized in that: The methanol cycle injection amount function is as follows: ； The diesel cycle injection quantity function is as follows: ； In the formula, is the methanol cycle injection amount, is the diesel cycle injection amount in pure diesel mode, is the target methanol substitution rate, is the theoretical lower calorific value of methanol, The theoretical lower calorific value of diesel, is the diesel cycle injection amount.

3. The method according to claim 1, characterized in that: The alcohol injection time is from the closing time of the intake valve to 20°CA before the top dead center, the alcohol injection duration is in the range of 0~30°CA, and the alcohol injection pressure is not less than 60Mpa; The overhead fuel injector is a diesel fuel injector, and the side fuel injector is a methanol fuel injector.

4. The method according to claim 3, characterized in that: The diameter of the spray hole of the overhead diesel injector is smaller than the diameter of the spray hole of the diesel injector in the pure diesel mode. Two side-mounted methanol injectors are provided, wherein the angle between the center line of one side-mounted methanol injector and the center line of the cylinder is set in the range of 0° to 45°, and the angle between the center line of the other side-mounted methanol injector and the center line of the cylinder is set in the range of 45° to 90°; In response to the center line of the side-mounted methanol fuel injector and the center line of the cylinder being within a range of 0° to 45°, an angle formed between the injection hole on the same side of the side-mounted fuel injector and the center line of the fuel injector is greater than an angle formed between the injection hole on the opposite side of the side-mounted fuel injector and the center line of the fuel injector; In response to the centerline of the side-mounted methanol injector and the centerline of the cylinder being in the range of 45° to 90°, the angle formed between the spray hole on the same side of the side-mounted injector and the centerline of the injector is smaller than the angle formed between the spray hole on the opposite side of the side-mounted injector and the centerline of the injector.

5. The method according to claim 4, characterized in that: The diameter of the spray hole on the opposite side of the side-mounted fuel injector is smaller than the diameter of the spray hole on the same side.

6. The method according to claim 3, characterized in that: The shapes of the combustion chamber at least include a shallow basin type, a hemispherical type and an asymmetric pit type.

7. The method according to claim 1, characterized in that: Multiple heat release rate curves are fitted by multi-Weber function to simulate the combustion heat release rate in pure diesel mode. The heat release rate simulated by multi-Weber function is used as input and brought into one-dimensional thermodynamic simulation software for simulation. By adjusting the model parameters, the calibration model in pure diesel mode is obtained. A methanol-diesel dual direct injection simulation model is established based on the calibration model, and the methanol-diesel dual direct injection simulation model is simulated through three-dimensional simulation results. The methanol-diesel dual direct injection simulation model provides boundary conditions for the three-dimensional thermodynamic simulation model, and the three-dimensional simulation results feed back to the methanol-diesel dual direct injection simulation model to perform simulation verification of the one-dimensional dual injector performance.

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