A calculation method for the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine

Abstract

The present application discloses a method for calculating the spray combustion process of a high-pressure direct-injection dual-fuel marine internal combustion engine, which belongs to the field of simulation calculation of the engine spray combustion process, including: calculating the dual-fuel spray jet penetration distance and spray jet volume; judging the spray interference state, confirming the real-time medium composition in the cylinder of the marine internal combustion engine based on the concept of local uniform mixing, and calculating the ternary coupled entrainment process of high-reactivity fuel, low-reactivity fuel and air under the spray interference state; using the Monte Carlo method to obtain the collision frequency between spherical particles; based on the concept of random collision of particles and the assumption of equal distribution of matter in half, using the probability density function to obtain the momentum, material composition and thermodynamic properties of the mixture particles; using the Arrhenius single-step chemical reaction to calculate the combustion reaction rate; based on the first law of thermodynamics and the ideal gas state equation, calculating the instantaneous temperature and pressure in the cylinder, and quickly and accurately predicting the spray combustion process in the marine internal combustion engine under the high-pressure direct-injection dual-fuel mode.

Description

Technical Field

[0001] The present application relates to a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, and belongs to the field of simulation calculation of the engine spray combustion process. Background Art

[0002] Marine internal combustion engines are the main power unit for ocean-going transportation and have made important contributions to the development of international trade. The use of low-carbon or zero-carbon fuels in marine internal combustion engines is the main emission reduction measure in the future. However, the use of low-carbon or zero-carbon fuels alone in marine internal combustion engines is very challenging. For example, gaseous fuels such as hydrogen or natural gas are extremely difficult to compress and ignite, while ammonia fuels have combustion characteristics such as high autoignition temperature, narrow ignition limit and slow flame propagation speed. Therefore, the high-pressure direct injection dual-fuel mode is adopted, and high-reactivity fuels such as diesel are directly injected into the cylinder to form an oil-gas mixture with low-reactivity fuels such as ammonia. The multi-point ignition and autoignition process of the high-reactivity fuel is used to ignite the low-reactivity fuel, which can significantly improve the combustion process and thus improve the thermal efficiency of marine internal combustion engines.

[0003] In high-pressure direct injection dual-fuel marine internal combustion engines, since the dual-fuel injectors are controlled separately, the coupled injection strategy of the two can be flexibly adjusted, so as to form an ideal target reaction concentration distribution in the cylinder and achieve a perfect combustion effect of low-reactivity fuels such as ammonia. However, in the case of multiple injectors, the possibility of collision between direct injection jets increases, thereby changing the dual-fuel spray penetration and oil-gas mixing process. For example, after the two sprays collide, the spray area and circumference increase due to the diffusion of rebound droplets, and expand outward into a fan-shaped structure, so the interaction with the ambient gas is enhanced, accompanied by more eddy structures. At the same time, due to the interaction of the droplet groups after the spray collision, they are dispersed into smaller droplets, which increases the solubility of the ambient gas in the droplets, thereby greatly shortening the oil-gas mixing time, accelerating the evaporation rate, and resulting in a shorter ignition delay. However, since the collision process may be accompanied by the accumulation and momentum loss of unevaporated droplets, it is easy to cause excessive local equivalence ratio and excessive heat release, and a large number of inadequately mixed droplets added to the high-temperature combustion process will lead to a significant increase in soot emissions. It can be seen that the jet development, oil-gas mixing and combustion process under the spray collision caused by multiple injectors are very complicated, which is completely different from a single free spray. Good dual-fuel spray collision mixing is the key to improving the combustion process, and accurate calculation of the spray air entrainment is an important prerequisite for accurately evaluating the mixture concentration and combustion reaction rate. However, there is currently no accurate and effective calculation method applicable to the complex spray combustion process of high-pressure direct injection dual-fuel marine internal combustion engines. Summary of the invention

[0004] The purpose of this application is to provide a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, to achieve rapid and accurate prediction of the interference collision spray flame development process in a marine internal combustion engine under a high-pressure direct injection dual-fuel mode, and to provide theoretical analysis and engineering evaluation tools for adjusting the injection strategy of a high-pressure direct injection dual-fuel marine internal combustion engine and optimizing the mixing process, thereby improving the combustion and emission characteristics.

[0005] To achieve the above objectives, the first aspect of the present application provides a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, comprising:

[0006] S100 calculates the spray jet penetration distance and spray jet volume of each dual-fuel spray, wherein the dual-fuel spray includes a spray of a high-reactivity fuel injection and a spray of a low-reactivity fuel injection;

[0007] S200 determines the spray interference state of the dual-fuel spray through the macroscopic trajectory of the spray jet penetration distance, confirms the real-time medium composition in the cylinder of the marine internal combustion engine based on the concept of local uniform mixing, and calculates the entrainment process of the three-way coupling of high-reactivity fuel, low-reactivity fuel and air under the spray interference state according to the spray jet volume;

[0008] S300, based on the entrainment process, uses the Monte Carlo method to discretize the gaseous fuel and the entrained air into a number of spherical particles of equal mass, and obtains the collision frequency between the spherical particles according to the turbulent state of the dual-fuel spray region;

[0009] S400 is based on the concept of random particle collision and the assumption of equal division of matter in half, and uses probability density function to obtain the momentum, material composition and thermodynamic properties of mixture particles, wherein the mixture particles are particles formed by collision and mixing of two spherical particles;

[0010] S500 calculates the reaction rate of the dual-fuel spray combustion process using an Arrhenius single-step chemical reaction according to the momentum, material composition and thermodynamic properties;

[0011] S600 obtains the overall combustion heat release rate of the dual-fuel spray by accumulating the combustion enthalpy of all mixture particles according to the reaction rate, and calculates the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine based on the first law of thermodynamics and the ideal gas state equation.

[0012] In one implementation, step S100 specifically includes:

[0013] The instantaneous spray jet penetration distance and spray jet volume of the high-reactivity fuel are calculated according to the nozzle diameter contraction coefficient, spray cross-sectional velocity and volume fraction distribution factor, effective spray jet velocity, effective nozzle diameter, spray cone angle and injection duration of the high-reactivity fuel.

[0014] The instantaneous spray jet penetration distance and spray jet volume of low-reactivity fuel are calculated based on the nozzle diameter contraction coefficient of low-reactivity fuel, spray cross-sectional velocity and volume fraction distribution factor, effective injection velocity of spray jet, effective nozzle diameter, spray cone angle and injection duration.

[0015] In one implementation, step S200 specifically includes:

[0016] In the high-pressure direct injection dual-fuel mode, the low-reactivity fuel is injected at the top dead center along with the high-reactivity fuel. When the injectors of the dual-fuel spray are arranged together, the high-reactivity fuel is directly sprayed into the compressed air in the cylinder and is not affected by the low-reactivity fuel spray. The spray volume change rate of the high-reactivity fuel is obtained according to the spray jet volume, and the air entrainment rate of the high-reactivity fuel spray is calculated.

[0017] The low-reactivity fuel main spray penetrates into the high-reactivity fuel pilot spray. Before the low-reactivity fuel main spray exceeds the high-reactivity fuel pilot spray, it will entrain the oil-gas mixture of the high-reactivity fuel pilot spray. Assuming that the oil-gas mixture is mixed evenly, the spray volume change rate of the low-reactivity fuel is obtained according to the spray jet volume, and the effective entrainment rate of the low-reactivity fuel spray is calculated;

[0018] When the low-reactivity fuel main spray exceeds the high-reactivity fuel pilot spray, the high-reactivity fuel pilot spray is considered to be completely entrained in the low-reactivity fuel main spray, and the entrainment effect of the high-reactivity fuel pilot spray on the low-reactivity fuel main spray is ignored, and the effective entrainment rate of the low-reactivity fuel spray is calculated.

[0019] In one implementation, step S200 specifically includes:

[0020] In the low-pressure dual-fuel mode, the low-reactivity fuel enters the cylinder through the intake duct in advance and is fully mixed with the air during the intake and compression strokes to form a uniform mixture. It is assumed that the high-reactivity fuel penetrates into the uniform mixture of the low-reactivity fuel and the air in a direct injection manner. The spray volume change rate of the high-reactivity fuel is obtained based on the spray jet volume, and the effective entrainment rate of the high-reactivity fuel is calculated.

[0021] In one implementation, step S300 specifically includes:

[0022] The Monte Carlo method is used to discretize the gaseous fuel and the entrained air into a number of uniform spherical particles of equal mass, wherein the spherical particles include fuel particles and air particles;

[0023] The fuel particles and air particles are named and sorted in sequence, and the turbulent kinetic energy of the dual-fuel spray area and the collision frequency between the fuel particles and the air particles are calculated based on the total mass, turbulence generation rate, turbulence average length scale and collision coefficient of the dual-fuel spray area.

[0024] In one implementation, step S400 specifically includes:

[0025] Based on the concept of random particle collision, it is assumed that two colliding spherical particles exchange half of their momentum, material composition and thermodynamic properties with each other, and the exchanged momentum, material composition and thermodynamic properties are represented by variables;

[0026] The probability density function is used to calculate the variable state corresponding to the collision and mixing of the two spherical particles according to the random numbers of 1 or 0 and the variable state corresponding to the exchange of the two colliding spherical particles at any time.

[0027] In one implementation, step S500 specifically includes:

[0028] The fuel molar concentration and oxygen molar concentration of the mixture particles are obtained based on the momentum, material composition and thermodynamic properties, and the reaction rate of the fuel and oxygen combustion process in the mixture particles is calculated using Arrhenius single-step chemical reaction.

[0029] In one implementation, step S600 specifically includes:

[0030] According to the reaction rate, combined with the specific enthalpy of each substance, the combustion enthalpy change of the mixture particles during the combustion process is obtained, and the concentration and thermodynamic state of each substance in the mixture particles after the combustion reaction are calculated. The combustion enthalpy changes of all mixture particles are accumulated to obtain the overall combustion heat release rate of the dual-fuel spray, and the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine are calculated by the first law of thermodynamics and the ideal gas state equation.

[0031] The second aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the first aspect or any one of the embodiments of the first aspect when executing the computer program.

[0032] A third aspect of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the first aspect or any implementation of the first aspect are implemented.

[0033] As can be seen from the above, in order to fill the gap in the research field of high-pressure direct injection dual-fuel marine internal combustion engine spray combustion process, this application provides a high-pressure direct injection dual-fuel marine internal combustion engine spray combustion process calculation method, through the dual-fuel spray spray jet penetration distance of the macroscopic trajectory to determine the spray interference state, based on the concept of local uniform mixing to confirm the real-time medium composition in the cylinder of the marine internal combustion engine, and calculate the high-reactivity fuel, low-reactivity fuel and air ternary coupling entrainment process under the spray interference condition, and then use the Monte Carlo method to discretize the gas phase fuel and entrainment air into a series of equal mass and uniform spherical particles, and obtain the collision frequency between particles according to the turbulent state of the dual-fuel spray zone. Subsequently, based on the concept of random collision of particles and the assumption of equal distribution of matter in half, the probability density function is used to obtain the momentum and material composition of particles after collision and mixing, as well as the thermodynamic properties, and the Arrhenius single-step chemical reaction is used to calculate the reaction rate of the dual-fuel spray combustion process. Finally, the overall combustion heat release rate of the dual-fuel spray is obtained by accumulating the combustion enthalpy of all mixture particles, and the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine are calculated based on the first law of thermodynamics and the ideal gas state equation. This method has fast calculation speed and high calculation accuracy, and can be applied to various high-pressure direct injection dual-fuel and multi-fuel modes, providing a faster, more accurate and efficient numerical research method for the prediction and analysis of the spray combustion process of marine internal combustion engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A schematic flow chart of a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine provided in an embodiment of the present application;

[0036] Figure 2 This is a comparison chart of the heat release rate results of an ammonia-diesel dual-fuel fast compressor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0038] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0039] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise.

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0042] Embodiment 1

[0043] The present application embodiment provides a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, such as Figure 1 As shown, the method includes:

[0044] S100 calculates the spray jet penetration distance and spray jet volume of each dual-fuel spray, wherein the dual-fuel spray includes a spray of a high-reactivity fuel injection and a spray of a low-reactivity fuel injection;

[0045] In one implementation, step S100 specifically includes:

[0046] According to the high reactivity fuel nozzle diameter contraction coefficient C d1 , spray cross-sectional velocity and volume fraction distribution factor β, effective injection velocity U of the spray jet eff1 (t), effective nozzle diameter d eq1 , spray cone angle θ1 and injection duration t j1 The instantaneous spray jet penetration distance S of the highly reactive fuel is calculated tip1 and spray volume V spray1 , the specific calculation formula is as follows:

[0047]

[0048]

[0049] According to the low-reactivity fuel nozzle diameter contraction coefficient C d2 , spray cross-sectional velocity and volume fraction distribution factor β, effective injection velocity U of the spray jet eff2 (t), effective nozzle diameter d eq2 , spray cone angle θ2 and injection duration t j2 , the instantaneous spray jet penetration distance S of low-reactivity fuel is calculated tip2 and spray volume V spray2 , the specific calculation formula is as follows:

[0050]

[0051]

[0052] S200 determines the spray interference state of the dual-fuel spray through the macroscopic trajectory of the spray jet penetration distance, confirms the real-time medium composition in the cylinder of the marine internal combustion engine based on the concept of local uniform mixing, and calculates the entrainment process of the three-way coupling of high-reactivity fuel, low-reactivity fuel and air under the spray interference state according to the spray jet volume;

[0053] In one implementation, step S200 specifically includes:

[0054] In the high-pressure direct injection dual-fuel mode, the low-reactivity fuel injection is usually followed by the high-reactivity fuel injection at around the top dead center. When the injectors of the dual-fuel spray are closely installed together, the high-reactivity fuel is directly injected into the compressed air in the cylinder and is not affected by the low-reactivity fuel spray. According to the spray jet volume V spray1 Get the spray volume change rate of high reactivity fuel The ambient gas density ρ combined with the high-reactivity fuel a1 , mass injection rate and density ρ f1 , spray cross-sectional velocity and volume fraction distribution factor β and injection duration t j1 , the air entrainment rate of the highly reactive fuel spray is calculated The specific calculation formula is as follows:

[0055]

[0056] In one implementation, step S200 further includes:

[0057] In the high-pressure direct injection dual-fuel mode, the low-reactivity fuel main spray first penetrates the high-reactivity fuel pre-spray, and then exceeds the high-reactivity fuel pre-spray after a period of time. Before the low-reactivity fuel main spray exceeds the high-reactivity fuel pre-spray, it will entrain the oil-air mixture of the high-reactivity fuel pre-spray. Assuming that the high-reactivity fuel pre-spray is evenly mixed, according to the spray jet volume V spray2 Get the spray volume change rate of low-reactivity fuel The average density of the pilot spray combined with the high-reactivity fuel is aveHP , air mass in pre-spray spray m a1 , the mass of high reactivity fuel m f1 , mass injection rate of low-reactivity fuel and density ρ f2 , and the starting point t of low-reactivity fuel injection 2s and the end point t 2e , the effective entrainment rate of the low-reactivity fuel spray is calculated The specific calculation formula is as follows:

[0058]

[0059] In one implementation, step S200 further includes:

[0060] In the high-pressure direct injection dual-fuel mode, when the low-reactivity fuel main spray exceeds the high-reactivity fuel pre-spray, the high-reactivity fuel pre-spray is considered to be completely entrained in the low-reactivity fuel main spray, ignoring the entrainment effect of the pre-spray on the main spray. According to the ambient gas density ρ of the low-reactivity fuel, a2 , spray volume change rate Mass injection rate and density ρ f2 , spray cross-sectional velocity and volume fraction distribution factor β and injection duration t j2 , the effective entrainment rate of the low-reactivity fuel spray is calculated The specific calculation formula is as follows:

[0061]

[0062] In one implementation, step S200 specifically includes:

[0063] In the low-pressure dual-fuel mode, the low-reactivity fuel enters the cylinder through the intake duct in advance and is fully mixed with the air during the intake and compression strokes. Assuming that a high-reactivity fuel such as diesel is directly injected into the uniform mixture of the low-reactivity fuel and air, according to the spray jet volume V spray1 Get the spray volume change rate of high reactivity fuel Combined with the average density of the homogeneous mixture ρ aveLP , total intake air mass m aLP , the total mass of low-reactivity fuel m fLP , mass injection rate of high-reactivity fuel and density ρ f1 , the starting point of high-reactivity fuel injection t 1s and the end point t 1e , the effective entrainment rate of the highly reactive fuel is calculated as The specific calculation formula is as follows:

[0064]

[0065] In one embodiment, for liquid fuel spray, when the high-temperature air rolls in, it will evaporate the cold fuel, according to the coefficient C r , injection pressure difference Δp j , nozzle diameter d n , cylinder pressure p, cylinder temperature T, liquid fuel mass m liq , the heat required for vaporization of unit fuel mass E, and the heat absorption rate per unit fuel mass r a and the fuel evaporation rate r V , the specific calculation formula is as follows:

[0066]

[0067]

[0068] In one embodiment, the embodiment of the present application determines the interference state of the two spray beams through the macroscopic trajectory of the dual-fuel spray jet penetration distance, taking into account the spatial layout factors of the injector, and can be applied to various dual-fuel injector installation schemes, including adjacent, cross and opposed injector spatial layout structures, and can be extended to the spray interference prediction of marine internal combustion engines with three or more multi-injectors. At the same time, based on the concept of local uniform mixing, the real-time medium composition in the cylinder of the marine internal combustion engine is confirmed, and the entrainment process of the three-way coupling of high-reactivity fuel, low-reactivity fuel and air under the spray interference condition is calculated, which can truly reflect the complex entrainment process of the dual-fuel spray and improve the prediction accuracy.

[0069] S300, based on the entrainment process, uses the Monte Carlo method to discretize the gaseous fuel and the entrained air into a number of spherical particles of equal mass, and obtains the collision frequency between the spherical particles according to the turbulent state of the dual-fuel spray region;

[0070] In one implementation, step S300 specifically includes:

[0071] The Monte Carlo method is used to discretize the gaseous fuel and the entrained air into a series of uniform spherical particles of equal mass, wherein the spherical particles include fuel particles and air particles;

[0072] The fuel particles and air particles are named and sorted in sequence according to the total mass M of the dual-fuel spray area. s , turbulence generation rate G, turbulence average length scale L and collision coefficient C col , the turbulent kinetic energy k in the dual-fuel spray area and the collision frequency ω between fuel particles and air particles are calculated. The specific calculation formula is as follows:

[0073]

[0074]

[0075] In one embodiment, the embodiment of the present application uses the Monte Carlo method to discretize the gaseous fuel and the entrained air into a series of uniform spherical particles of equal mass, and controls the mixing rate of the fuel and gas through the collision frequency between particles in combination with the turbulent state of the dual-fuel spray region, thereby greatly simplifying the mathematical description of the complex physical mixing process.

[0076] S400 is based on the concept of random particle collision and the assumption of equal division of matter in half, and uses probability density function to obtain the momentum, material composition and thermodynamic properties of mixture particles, wherein the mixture particles are particles formed by collision and mixing of two spherical particles;

[0077] In one implementation, step S400 specifically includes:

[0078] Based on the concept of random particle collision, it is assumed that two colliding spherical particles exchange half of their momentum, material composition and thermodynamic properties with each other, and the exchanged momentum, material composition and thermodynamic properties are represented by variables x;

[0079] The probability density function is used to calculate the variable states f(x1, t) and f(x2, t) at time t+Δt after the collision and mixing of the two spherical particles, based on the random number X of 1 or 0 and the corresponding exchanged variable states f(x1, t) and f(x2, t) of the two colliding spherical particles at time t. The specific calculation formula is as follows:

[0080]

[0081]

[0082] In one embodiment, the embodiment of the present application is based on the concept of random particle collisions and the assumption of equal division of matter in half, and uses a probability density function to obtain the momentum, material composition, and thermodynamic properties of spherical colliding particles after mixing. It can quickly and accurately calculate the complex mixing process of multi-media in the dual-fuel spray area, thereby improving the calculation speed.

[0083] S500 calculates the reaction rate of the dual-fuel spray combustion process using an Arrhenius single-step chemical reaction according to the momentum, material composition and thermodynamic properties;

[0084] In one embodiment, an Arrhenius single-step chemical reaction is used, and the fuel molar concentration X of the mixture particles formed after the spherical particles collide and mix is ​​determined. f Its index a, oxygen molar concentration and its index b, reaction constant A, cylinder temperature T and its index n, fuel activation energy E a and the ideal gas constant R, the reaction rate k of the combustion of fuel and oxygen in the mixture particles is calculated r , the specific calculation formula is as follows:

[0085]

[0086] S600 obtains the overall combustion heat release rate of the dual-fuel spray by accumulating the combustion enthalpy of all mixture particles according to the reaction rate, and calculates the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine based on the first law of thermodynamics and the ideal gas state equation.

[0087] In one embodiment, the enthalpy change during the combustion of the mixture particles is obtained based on the combustion reaction rate of the mixture particles and the specific enthalpy of each substance, and the concentration and thermodynamic state of each substance in the mixture particles after the combustion reaction are calculated. Then, the combustion enthalpy change of all mixture particles is accumulated to obtain the overall combustion heat release rate of the dual-fuel spray, and the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine are calculated by the first law of thermodynamics and the ideal gas state equation.

[0088] In one embodiment, the embodiment of the present application uses the Arrhenius single-step chemical reaction to calculate the combustion process of the fuel and oxygen based on the fuel molar concentration and oxygen molar concentration of the mixture particles after collision mixing, and obtains the thermodynamic properties such as the heat release rate, temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine based on the first law of thermodynamics and the ideal gas state equation. It can quickly and accurately calculate the combustion process in the dual-fuel spray zone and predict the thermodynamic state in the engine cylinder, greatly improving the calculation speed. At the same time, the overall package reaction model of fuel and oxygen is simple and flexible, and can be extended to the combustion process calculation of various marine internal combustion engine fuels, providing a powerful numerical research method for the prediction and analysis of the spray combustion process of high-pressure direct injection dual-fuel marine internal combustion engine.

[0089] As can be seen from the above, the embodiment of the present application provides a method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, which judges the spray interference state through the macroscopic trajectory of the spray jet penetration distance of the dual-fuel spray, confirms the real-time medium composition in the cylinder of the marine internal combustion engine based on the concept of local uniform mixing, and calculates the entrainment process of the high-reactivity fuel, low-reactivity fuel and air ternary coupling under the spray interference condition, and calculates the evaporation rate of the liquid fuel according to the physical properties of the liquid fuel and the injection conditions and the thermodynamic state in the cylinder. Then, the Monte Carlo method is used to discretize and abstract the gas phase fuel and the entrained air into a series of spherical particles of equal mass and uniformity, and the collision frequency between particles is obtained according to the turbulent state of the dual-fuel spray zone. Subsequently, based on the concept of random collision of particles and the assumption of equal division of matter in half, the probability density function is used to obtain the momentum and material composition and thermodynamic properties of the particles after collision and mixing, and according to the molar concentration of fuel and molar concentration of oxygen after collision and mixing of spherical particles, the reaction rate of fuel and oxygen combustion in the particles is calculated using the Arrhenius single-step chemical reaction. Finally, the combustion enthalpy of all mixture particles and the concentration and thermodynamic state of each substance in the mixture particles after the combustion reaction are calculated. The overall combustion heat release rate of the dual-fuel spray is obtained by accumulating the combustion enthalpy of all mixture particles, and the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine are calculated based on the first law of thermodynamics and the ideal gas state equation. This method has fast calculation speed and high calculation accuracy, and can be applied to various high-pressure direct injection dual-fuel and multi-fuel modes, providing a faster, more accurate and efficient numerical research method for the prediction and analysis of the spray combustion process of marine internal combustion engines.

[0090] Embodiment 2

[0091] In an application scenario, the embodiment of the present application uses an ammonia-diesel dual-fuel fast compressor to conduct experiments to verify the effect of the method described in Example 1. The injection parameters and experimental conditions of the ammonia-diesel dual-fuel fast compressor are shown in Table 1.

[0092] Fast press cylinder diameter / mm 220 Effective compression ratio 20.5 Equivalent speed / rpm 1000 Top dead point temperature / K 920 Top dead center pressure / bar 125 Fuel Type Diesel + Ammonia Fuel Fuel injection temperature / K 293 <![CDATA[Fuel density / (kg / m 3 )]]> Diesel: 870; Ammonia fuel: 610 Fuel injection pressure / (MPa) Diesel: 200; Ammonia fuel: 56 Fuel injection duration / (ms) Diesel: 0.52; Ammonia fuel: 2.7 Injector holes 1 Nozzle diameter / mm Diesel: 0.2; Ammonia fuel: 0.98 Fuel injection mass / (mg) Diesel: 5; Ammonia fuel: 220

[0093] Table 1 Injection parameters and experimental conditions

[0094] Based on the above injection parameters and experimental conditions, the calculated results of the heat release rate of the ammonia-diesel dual-fuel fast compressor are compared with the experimental data. Figure 2 As shown, it can be seen that the method of the embodiment of the present application has fast calculation speed and high calculation accuracy, and can be applied to various high-pressure direct injection dual-fuel and multi-fuel modes.

[0095] Embodiment 3

[0096] An embodiment of the present application provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the memory is used to store software programs and modules, and the processor executes various functional applications and data processing by running the software programs and modules stored in the memory. The memory and the processor are connected via a bus. Specifically, the processor implements any step in the first embodiment above by running the computer program stored in the memory.

[0097] It should be understood that in the embodiments of the present application, the processor referred to may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0098] The memory may include a read-only memory, a flash memory, and a random access memory, and provides instructions and data to the processor. A part or all of the memory may also include a nonvolatile random access memory.

[0099] It should be understood that the above-mentioned integrated module / unit, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on such an understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The above-mentioned computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the above-mentioned computer program includes computer program code, and the above-mentioned computer program code can be in source code form, object code form, executable file or some intermediate form. The above-mentioned computer-readable medium may include: any entity or device capable of carrying the above-mentioned computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the above-mentioned computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0100] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

[0101] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the above-mentioned device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0102] It should be noted that the methods and detailed examples provided in the above embodiments can be combined with the devices and equipment provided in the embodiments, and references can be made to each other, and no further details will be given.

[0103] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0104] In the embodiments provided in the present application, it should be understood that the disclosed apparatus / terminal equipment and method can be implemented in other ways. For example, the apparatus / equipment embodiments described above are only schematic, for example, the division of the above modules or units is only a logical function division, and in actual implementation, other division methods can be used, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0105] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine, characterized in that: include: S100 calculates the spray jet penetration distance and spray jet volume of each dual-fuel spray, wherein the dual-fuel spray includes a spray of a high-reactivity fuel injection and a spray of a low-reactivity fuel injection; S200 determines the spray interference state of the dual-fuel spray through the macroscopic trajectory of the spray jet penetration distance, confirms the real-time medium composition in the cylinder of the marine internal combustion engine based on the concept of local uniform mixing, and calculates the entrainment process of the three-way coupling of high-reactivity fuel, low-reactivity fuel and air under the spray interference state according to the spray jet volume; S300, based on the entrainment process, uses the Monte Carlo method to discretize the gaseous fuel and the entrained air into a number of spherical particles of equal mass, and obtains the collision frequency between the spherical particles according to the turbulent state of the dual-fuel spray region; S400 is based on the concept of random particle collision and the assumption of equal division of matter in half, and uses probability density function to obtain the momentum, material composition and thermodynamic properties of mixture particles, wherein the mixture particles are particles formed by collision and mixing of two spherical particles; S500 calculates the reaction rate of the dual-fuel spray combustion process using an Arrhenius single-step chemical reaction according to the momentum, material composition and thermodynamic properties; S600 calculates the overall combustion heat release rate of the dual-fuel spray by accumulating the combustion enthalpy of all mixture particles according to the reaction rate, and calculates the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine based on the first law of thermodynamics and the ideal gas state equation; Step S200 specifically includes: In the high-pressure direct injection dual-fuel mode, the low-reactivity fuel is injected at the top dead center along with the high-reactivity fuel. When the injectors of the dual-fuel spray are arranged together, the high-reactivity fuel is directly sprayed into the compressed air in the cylinder and is not affected by the low-reactivity fuel spray. The spray volume change rate of the high-reactivity fuel is obtained according to the spray jet volume, and the air entrainment rate of the high-reactivity fuel spray is calculated. The low-reactivity fuel main spray penetrates into the high-reactivity fuel pilot spray. Before the low-reactivity fuel main spray exceeds the high-reactivity fuel pilot spray, it will entrain the oil-gas mixture of the high-reactivity fuel pilot spray. Assuming that the oil-gas mixture is mixed evenly, the spray volume change rate of the low-reactivity fuel is obtained according to the spray jet volume, and the effective entrainment rate of the low-reactivity fuel spray is calculated; When the low-reactivity fuel main spray exceeds the high-reactivity fuel pilot spray, the high-reactivity fuel pilot spray is considered to be completely entrained in the low-reactivity fuel main spray, and the entrainment effect of the high-reactivity fuel pilot spray on the low-reactivity fuel main spray is ignored, and the effective entrainment rate of the low-reactivity fuel spray is calculated; In the low-pressure dual-fuel mode, the low-reactivity fuel enters the cylinder through the intake duct in advance and is fully mixed with the air during the intake and compression strokes to form a uniform mixture. It is assumed that the high-reactivity fuel penetrates into the uniform mixture of the low-reactivity fuel and the air in a direct injection manner. The spray volume change rate of the high-reactivity fuel is obtained based on the spray jet volume, and the effective entrainment rate of the high-reactivity fuel is calculated.

2. The method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine according to claim 1, characterized in that: Step S100 specifically includes: The instantaneous spray jet penetration distance and spray jet volume of the high-reactivity fuel are calculated according to the nozzle diameter contraction coefficient, spray cross-sectional velocity and volume fraction distribution factor, effective spray jet velocity, effective nozzle diameter, spray cone angle and injection duration of the high-reactivity fuel. The instantaneous spray jet penetration distance and spray jet volume of low-reactivity fuel are calculated based on the nozzle diameter contraction coefficient of low-reactivity fuel, spray cross-sectional velocity and volume fraction distribution factor, effective injection velocity of spray jet, effective nozzle diameter, spray cone angle and injection duration.

3. The method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine according to claim 1 or 2, characterized in that: Step S300 specifically includes: The Monte Carlo method is used to discretize the gaseous fuel and the entrained air into a number of uniform spherical particles of equal mass, wherein the spherical particles include fuel particles and air particles; The fuel particles and air particles are named and sorted in sequence, and the turbulent kinetic energy of the dual-fuel spray area and the collision frequency between the fuel particles and the air particles are calculated based on the total mass, turbulence generation rate, turbulence average length scale and collision coefficient of the dual-fuel spray area.

4. The method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine according to claim 1 or 2, characterized in that: Step S400 specifically includes: Based on the concept of random particle collision, it is assumed that two colliding spherical particles exchange half of their momentum, material composition and thermodynamic properties with each other, and the exchanged momentum, material composition and thermodynamic properties are represented by variables; The probability density function is used to calculate the variable state corresponding to the collision and mixing of the two spherical particles according to the random numbers of 1 or 0 and the variable state corresponding to the exchange of the two colliding spherical particles at any time.

5. The method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine according to claim 1 or 2, characterized in that: Step S500 specifically includes: The fuel molar concentration and oxygen molar concentration of the mixture particles are obtained based on the momentum, material composition and thermodynamic properties, and the reaction rate of the fuel and oxygen combustion process in the mixture particles is calculated using Arrhenius single-step chemical reaction.

6. The method for calculating the spray combustion process of a high-pressure direct injection dual-fuel marine internal combustion engine according to claim 5, characterized in that: Step S600 specifically includes: According to the reaction rate, combined with the specific enthalpy of each substance, the combustion enthalpy change of the mixture particles during the combustion process is obtained, and the concentration and thermodynamic state of each substance in the mixture particles after the combustion reaction are calculated. The combustion enthalpy changes of all mixture particles are accumulated to obtain the overall combustion heat release rate of the dual-fuel spray, and the instantaneous temperature and pressure in the cylinder of the high-pressure direct injection dual-fuel marine internal combustion engine are calculated by the first law of thermodynamics and the ideal gas state equation.

7. An electronic device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method according to any one of claims 1 to 6 when executing the computer program.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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