Calculation Method and Equipment for Fuel and Air Mixing Process of Marine Internal Combustion Engine

Abstract

A calculation method and device for the fuel and air mixing process of marine internal combustion engines, belonging to the field of simulation technology, solve the problems of low accuracy and long calculation time of the mixing process calculation method. The method of the present invention includes: abstracting the gaseous or liquid fuel injected within each calculation step and the entrained air into uniform spherical particles respectively through discrete assumptions, then using the Weber number based on fluid theory to characterize the comprehensive influence of the physical properties and kinetic states of the fuel and air particles, etc. on the collision results, then constructing a collision pulse spectrum diagram according to the Weber number of the collision particle pairs and the eccentricity between the particle mass centers, and clearly refining the effective collision region through the collision boundary line, and finally quantifying the mass exchange mechanism under different effective collision mechanisms, and a calculation method for the fuel and air mixing process of marine internal combustion engines is proposed. This method has a fast calculation speed and high calculation accuracy. The present invention is applicable to various marine internal combustion engine fuels and advanced injection strategies.

Description

Technical Field

[0001] This application relates to the field of simulation technology, and particularly to the simulation of the engine spray mixing process. Background Art

[0002] Marine transportation is the backbone of international trade logistics, with advantages such as low cost, large shipping volume, and long shipping distance, accounting for more than 90% of the global trade volume. As the main power device for marine transportation, marine internal combustion engines have made important contributions. In order to meet the increasingly strict carbon reduction regulations, marine internal combustion engines are forced to adopt different low-carbon or zero-carbon fuels to contribute to the implementation and development of the dual-carbon strategy in the shipping field.

[0003] The mixing state of fuel and air in marine internal combustion engines directly affects the subsequent combustion quality and emission levels. Therefore, it is crucial to adjust and optimize the mixing process of fuel and air in marine internal combustion engines. However, with the increasingly advanced injection strategies and more diverse fuels, the mixing process of fuel and air in marine internal combustion engines has become more complex and difficult to predict. For example, different fuel types and injection strategies result in different kinetic states and physicochemical properties such as the velocity, size, viscosity, and surface tension of oil and gas particles, leading to different collision results and ultimately very different oil and gas mixing effects. For green biodiesel and ammonia fuels, their viscosities are much higher than that of traditional diesel. High viscosity inhibits spray atomization, evaporation, and diffusion, and as the high-viscosity fuel is entrained by air, the viscosity of the mixture continuously changes, and the viscous force also changes accordingly. At the same time, the kinetic state of fuel particles gradually decreases during the mixing process. These coupled factors make the collision mechanism extremely complex. For gas fuels such as hydrogen and natural gas, the jet development does not involve the processes of droplet atomization, breakup, and evaporation, so the diffusion is faster, the cone angle is larger, and the mixing speed with air is faster. Especially in the dual-fuel mode of marine internal combustion engines, fuels with different gas-liquid states and atomization characteristics are mixed together, further increasing the difficulty of predicting the mixture concentration. Moreover, marine internal combustion engines have large cylinder bores and working volumes, and the amount of fuel and compressed air input in each working cycle is relatively large. It is necessary to improve the calculation speed while ensuring the prediction accuracy of the mixing process. However, the existing calculation methods for the mixing process currently need to handle a large number of particles, resulting in a long calculation time, and ignoring the influence of fuel physical properties and kinetic states on the collision process, leading to an imperfect mass exchange mechanism and being unable to quickly and accurately describe the fuel and air mixing process of marine internal combustion engines. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of low accuracy and long calculation time of the existing mixing process calculation methods, and provide a calculation method and device for the fuel and air mixing process of marine internal combustion engines.

[0005] The present invention is realized through the following technical solutions. On the one hand, the present invention provides a calculation method for the fuel and air mixing process of marine internal combustion engines, and the method includes:

[0006] Step 1: Obtain the spray penetration distance according to the fuel injection conditions, and calculate the air entrainment rate based on the spray penetration distance.

[0007] Step 2: Based on the discretization assumption, abstract the gaseous or liquid fuel injected within each calculation step and the entrained air into uniform spherical particles respectively, and calculate the volume and diameter of the fuel particles and the volume and diameter of the air particles according to the fuel injection mass and the air entrainment mass.

[0008] Step 3: Based on the fluid theory, use the Weber number to characterize the comprehensive influence of the physical properties and kinetic states of the fuel and air particles on the collision result, and couple the Weber number with the eccentricity between the mass centers of the colliding particle pairs to construct a collision pulse spectrum diagram.

[0009] Step 4: According to the collision parameters, particle size ratio and related parameters, clarify the lower limit boundary line of the rebound of particle pairs during collision, the dividing lines of coalescence and stretching separation, and the dividing lines of coalescence and reflexive separation, and divide into three effective collision regions of stretching separation, coalescence and reflexive separation.

[0010] Step 5: Abstract and simplify the physical processes of particle collisions under different effective collision mechanisms, and quantitatively calculate the mass, momentum and energy exchange processes between the colliding particle pairs to obtain the component concentration, kinetics and thermodynamic states after the mixing of the fuel and the gas.

[0011] Further, Step 1 includes:

[0012] Step 1.1: According to the nozzle diameter contraction coefficient C d , the spray cross-section velocity and volume fraction distribution factor β, the effective injection velocity U eff (t) of the spray jet, the effective nozzle diameter d eq , the spray cone angle θ and the fuel injection duration t j , calculate the instantaneous spray jet penetration distance S tip and the spray volume V spray :

[0013]

[0014]

[0015] Step 1.2: According to the ambient gas density ρ a , the spray volume change rate the fuel mass injection rate the fuel density ρ f and the spray cross-section velocity and volume fraction distribution factor β, calculate the air entrainment rate

[0016]

[0017] Furthermore, step 2 includes:

[0018] By discretizing the assumptions, the fuel injected and the air entrained within the computational step are respectively abstracted into uniform spherical particles. Based on the fuel mass m f and density ρ f as well as the mass m a of the air entrained and density ρ a , the volume V s and diameter d s of the fuel particles and the volume V l and diameter d l of the air particles are calculated:

[0019] Furthermore, step 3 includes:

[0020] Based on the lateral displacement b between the mass centers of the fuel particles and the air particles, the diameter d s of the fuel particles, the diameter d l of the air particles, the density ρ a of the air particles, the surface tension σ, and the relative velocity vector u r between the two particles, the dimensionless collision parameter B, the Weber number We, and the particle size ratio Δ are calculated:

[0021] Furthermore, step 4 includes:

[0022] Step 4.1: Based on the collision parameter B and the particle size ratio Δ, the coefficient τ and the ratio χ of the interaction region of the air particles to their volume are calculated: τ = (1 - B)(1 + Δ),

[0023] Step 4.2: Based on the collision parameter B, the particle size ratio Δ, the shape factor φ E and the ratio χ of the interaction region of the air particles to their volume, the lower rebound boundary line f 1 (B~We) of the particle pair collision is calculated:

[0024]

[0025] Step 4.3: Based on the collision parameter B and the particle size ratio Δ, the dividing line f 2 (B~We) between the coalescence and stretching separation of the particle pair collision is calculated:

[0026]

[0027] Step 4.4: Calculate parameters ξ and η based on the collision parameter B and the particle size ratio Δ s and η L : ξ = (1 / 2)B(1 + Δ), η S = 2(1 - ξ) 2 (1 - ξ 2 ) 1 / 2 -1, η L = 2(Δ - ξ) 2 (Δ 2 - ξ 2 ) 1 / 2 - Δ 3 ;

[0028] Step 4.5: Calculate the boundary line f between coalescence and reflex separation of particle pairs during collision based on the particle size ratio Δ, parameter η s and η L : f(B~We): 3 (B~We):

[0029]

[0030] Furthermore, Step 5 includes:

[0031] Step 5.1: During the stretching separation process, the binary particle pairs undergo non - central collisions, and their partial regions exchange substances with each other. Assume that the collision contact regions of fuel particle P s and air particle P l aggregate together to form a new homogeneous spherical particle P k ; At the same time, assume that the fuel mass fractions f s and f l , velocities u s and u l , densities ρ s and ρ l , and specific enthalpies h f and h a and h s and h l remain unchanged after stretching separation;

[0032] Calculate the collision region volume V s of fuel particle P l , the collision region volume V s of air particle P ss , and the volume V l of new particle P ls based on the ratio χ of the interaction region of air particles to their volume, the diameter d k of fuel particles, and the diameter d k of air particles: Vk = V ss + V ls ;

[0033] Step 5.2: According to the density ρ of air particles a , the density ρ of fuel particles f , fuel particle P s collision region volume V ss and air particle P l collision region volume V ls , calculate the masses of fuel particle P s and air particle P l as well as the new particle P k after stretching and separation and n represents the calculation step, n and n + 1 represent before and after the calculation respectively;

[0034] Step 5.3: According to the density ρ of air particles a , the density ρ of fuel particles f , fuel particle P s collision region volume V ss , air particle P l collision region volume V ls , fuel particle P s and air particle P l fuel mass fraction f s and f l , velocity u s and u l , as well as specific enthalpy h s and h l , calculate the density ρ k , fuel mass fraction f k , velocity u k and specific enthalpy h k of the new particle P k :

[0035] Step 5.4: During the coalescence process, binary particle pairs undergo head-on collisions and merge together; assume that the entire fuel particle P s and the entire air particle P l coalesce to form a new homogeneous and stable particle P k , and the original binary particle pair disappears; according to the volume V s and mass M sc of the entire fuel particle P sc and the volume V l and mass M lc of the entire air particle P lc, a new particle P is calculated k for the volume V k and mass M k : V k = V sc + V lc , M k = M sc + M lc ;

[0036] Step 5.5: Based on the mass M s of the entire fuel particle P, sc the mass M l of the entire air particle P, lc the fuel mass fraction f s of the fuel particle P l and the air particle P s and f l , the velocity u s and u l , as well as the specific enthalpy h s and h l , a new particle P k is calculated for the fuel mass fraction f k , the velocity u k and the specific enthalpy h k :

[0037] Step 5.6: During the reflexive separation process, it is assumed that within the calculation step size Δt, the fuel particle P s passes through the air particle P l , forming a swept volume ΔV, and ΔV is proportional to the volume fraction of the fuel particle volume V sr in the entire spray region volume; then the swept regions of the fuel particle P s and the air particle P l aggregate together to form a new homogeneous particle P k ; while the physical properties of the unswept regions of the fuel particle P s and the air particle P l , including the fuel mass fraction f s and f l , the velocity u s and u l , the density ρ f and ρ a as well as the specific enthalpy h s and h l remain unchanged after the reflexive separation compared to before the collision; based on the diameter d s of the fuel particle, the velocity u s of the fuel particle P l and the velocity u s of the air particle Pl 、Calculate the step size Δt and the fuel particle volume V sr 、The density ρ of the air particles a and the density ρ of the fuel particles f , calculate the swept volume ΔV, the fuel particle P s and the air particle P l of the swept mass M sr and M lr : M sr = ρ f ΔV, M lr = ρ a ΔV, where N represents the number of all particles in the entire spray area;

[0038] Step 5.7: According to the swept volume ΔV, the fuel particle P s and the air particle P l of the swept mass M sr and M lr , calculate the mass of the fuel particle P s and the air particle P l as well as the new particle P k after the reflexive separation and

[0039] Step 5.8: According to the swept mass M s of the fuel particle P l and the air particle P sr and M lr as well as the mass M k of the new particle P k after the reflexive separation, the fuel mass fraction f s of the fuel particle P l and the air particle P s and f l , the velocity u s and u l , and the specific enthalpy h s and h l , calculate the density ρ k , the fuel mass fraction f k , the velocity u k and the specific enthalpy h k of the new particle P k :

[0040] Step 5.9: For the collision of the mixture particles with two different fuel concentrations during the mixing process, distinguish according to the size, and represent the mixture particles with a smaller diameter by P s and represent the mixture particles with a larger diameter by P lIndicate, and then according to the mixing mechanism of pure fuel particles and pure air particles, repeat steps 3, 4, and steps 5.1 - 5.8 until the calculation ends to obtain the fuel concentration and air concentration inside each particle.

[0041] Furthermore, step 2 further includes:

[0042] According to the total mass M of the spray zone s , the turbulence production rate G, the turbulence mean length scale L, and the collision coefficient C col , calculate the turbulent kinetic energy k of the spray zone and the collision frequency ω of fuel particles and air particles:

[0043] In a second aspect, the present invention provides a computer device, including a memory and a processor. A computer program is stored in the memory. When the processor runs the computer program stored in the memory, it executes the steps of a calculation method for the fuel and air mixing process of a marine internal combustion engine as described above.

[0044] In a third aspect, the present invention provides a computer-readable storage medium, in which multiple computer instructions are stored. The multiple computer instructions are used to cause a computer to execute a calculation method for the fuel and air mixing process of a marine internal combustion engine as described above.

[0045] In a fourth aspect, the present invention provides an electronic device, including:

[0046] At least one processor; and,

[0047] A memory communicatively connected to the at least one processor; wherein,

[0048] The memory stores instructions executable by the at least one processor. The instructions are executed by the at least one processor to enable the at least one processor to execute a calculation method for the fuel and air mixing process of a marine internal combustion engine as described above.

[0049] Advantages of the present invention:

[0050] In the present invention, by means of discretization assumptions, the gaseous or liquid fuel injected within each calculation step and the entrained air are respectively abstracted into uniform spherical particles. Then, based on fluid theory, the Weber number is used to characterize the comprehensive influence of the physical properties and kinetic states of fuel and air particles, etc. on the collision results. Next, a collision pulse spectrum diagram is constructed according to the Weber number of the collision particle pairs and the eccentricity between the particle mass centers, and the effective collision region is clearly refined through the collision boundary line. Finally, the mass exchange mechanism under different effective collision mechanisms is quantified, and a calculation method for the fuel and air mixing process of a marine internal combustion engine is proposed.

[0051] In the present invention, by discretizing the assumptions, the injected fuel and the entrained air within the calculation step are respectively abstracted into uniform spherical particles, significantly reducing the number of collision and mixing particles to be processed and improving the calculation speed.

[0052] Secondly, based on fluid theory, the present invention uses the Weber number to characterize the comprehensive influence of the physical properties and kinetic states of fuel and air particles on the collision results, and couples the Weber number with the eccentricity between the mass centers of the colliding particle pairs to construct a collision pulse spectrum diagram, which can comprehensively reflect the spray mixing dynamics of fuels with different physical properties under variable injection strategies, expanding the application range and improving the prediction accuracy.

[0053] Then, the present invention clearly refines the effective collision region through the collision boundary line and quantifies the mass exchange mechanism under different effective collision mechanisms, enabling a more scientific, real, accurate, and rapid calculation of the real-time mixing state of fuel and air, greatly improving the prediction accuracy, and providing a powerful numerical research method for the analysis of the fuel and air mixing process in marine internal combustion engines.

[0054] The present invention has a fast calculation speed and high calculation accuracy, can be applied to various marine internal combustion engine fuels and advanced injection strategies, and provides a more rapid, accurate, and efficient numerical research method for the analysis of the fuel and air mixing process in marine internal combustion engines.

[0055] The present invention realizes the rapid and accurate prediction of the fuel and air mixing process under advanced injection strategies and fuel diversification, and provides a theoretical analysis and engineering evaluation tool for marine internal combustion engines to adjust injection strategies to optimize the mixing process and thus improve combustion and emission characteristics. Brief Description of the Drawings

[0056] To more clearly illustrate the technical solutions of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0057] Figure 1 It is the flow chart of the prediction method of the present invention;

[0058] Figure 2 It is the schematic diagram of the stretching and separation of colliding particle pairs;

[0059] Figure 3 It is the schematic diagram of the coalescence of colliding particle pairs;

[0060] Figure 4 It is the schematic diagram of the reflexive separation of colliding particle pairs;

[0061] Figure 5 It is the collision pulse spectrum diagram of the present invention. Detailed Embodiments

[0062] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0063] Embodiment 1. A method for calculating the fuel and air mixing process of a marine internal combustion engine, as Figure 1 shown, the method includes:

[0064] Step 1: Obtain the spray penetration distance according to the fuel injection conditions, and calculate the air entrainment rate through the spray penetration distance;

[0065] Step 2: Based on the discretization assumption, abstract the gaseous or liquid fuel injected within each calculation step and the entrained air into uniform spherical particles respectively, and calculate the volume and diameter of the fuel particles and the volume and diameter of the air particles according to the fuel injection mass and the air entrainment mass;

[0066] Step 3: Based on fluid theory, use the Weber number to characterize the comprehensive influence of the physical properties and kinetic states of the fuel and air particles on the collision result, and couple the Weber number with the eccentricity between the mass centers of the colliding particle pairs to construct a collision pulse spectrum diagram;

[0067] Step 4: According to the collision parameters, the particle size ratio, and related parameters, clarify the lower limit boundary line of the rebound of the particle pair collision, the coalescence and stretching separation demarcation line, and the coalescence and self-reflection separation demarcation line, and divide into three effective collision regions such as stretching separation, coalescence, and self-reflection separation;

[0068] Step 5: Abstract and simplify the physical process of particle collision under different effective collision mechanisms, and quantitatively calculate the mass, momentum, and energy exchange processes between the colliding particle pairs to obtain the component concentration, kinetics, and thermodynamic state after the fuel and gas are mixed.

[0069] In this embodiment, in order to fill the gap in the research field of the fuel and air mixing process of marine internal combustion engines, in this embodiment, the gaseous or liquid fuel injected within each calculation step and the entrained air are abstracted into uniform spherical particles through discrete assumptions, and then based on fluid theory, the Weber number is used to characterize the comprehensive influence of the physical properties and kinetic states of fuel and air particles, etc. on the collision results. Then, according to the Weber number of the colliding particle pairs and the eccentricity between the particle mass centers, a collision pulse spectrum diagram is constructed, and the effective collision region is clearly refined through the collision boundary line. Finally, the mass exchange mechanism under different effective collision mechanisms is quantified, and a calculation method for the fuel and air mixing process of marine internal combustion engines is proposed. This method has a fast calculation speed and high calculation accuracy, and can be applied to various marine internal combustion engine fuels and advanced injection strategies, providing a more rapid, accurate and efficient numerical research means for the analysis of the fuel and air mixing process of marine internal combustion engines.

[0070] Embodiment 2. This embodiment further limits a calculation method for the fuel and air mixing process of a marine internal combustion engine described in Embodiment 1. In this embodiment, Step 1 is further limited, specifically including:

[0071] Step 1 includes:

[0072] Step 1.1: According to the nozzle diameter contraction coefficient C d , the spray cross-sectional velocity and volume fraction distribution factor β, the effective injection velocity U eff (t) of the spray jet, the effective nozzle diameter d eq , the spray cone angle θ, and the fuel injection duration t j , the instantaneous spray jet penetration distance S tip and the spray volume V spray are calculated as follows:

[0073]

[0074]

[0075] Step 1.2: According to the ambient gas density ρ a , the spray volume change rate the fuel mass injection rate the fuel density ρ f , and the spray cross-sectional velocity and volume fraction distribution factor β, the air entrainment rate

[0076]

[0077] In this embodiment, a calculation method for the air entrainment rate is provided.

[0078] Embodiment 3. This embodiment further limits a calculation method for the fuel and air mixing process of a marine internal combustion engine described in Embodiment 2. In this embodiment, Step 2 is further limited, specifically including:

[0079] Step 2 includes:

[0080] By means of discretization hypothesis, the fuel injected within the calculation step length and the air entrained are respectively abstracted into uniform spherical particles. According to the fuel mass m f and density ρ f as well as the mass m a of the air entrained and density ρ a , the volume V s and diameter d s of the fuel particles and the volume V l and diameter d l of the air particles are calculated as follows:

[0081] In this embodiment, a method for abstracting the gaseous or liquid fuel injected within each calculation step length and the air entrained into uniform spherical particles respectively, and calculation methods for the volume and diameter of the fuel particles and the volume and diameter of the air particles are provided.

[0082] Firstly, abstracting into uniform spherical particles ignores the local concentration heterogeneity factor and reasonably simplifies the calculation process from the particle scale; secondly, considering the collision process of particles of different sizes significantly reduces the number of colliding and mixing particles to be processed and improves the calculation speed; the acquisition method of this embodiment can calculate the fuel mass and air entrainment mass within each step length, regard the equal-mass fuel and air as a uniform small ball, and then combine the density to obtain information such as the diameter according to the volume formula of the ball.

[0083] Embodiment 4. This embodiment further limits a calculation method for the fuel and air mixing process of a marine internal combustion engine described in Embodiment 3. In this embodiment, Step 3 is further limited, specifically including:

[0084] Step 3 includes:

[0085] According to the lateral displacement b between the mass centers of the fuel particles and the air particles, the diameter d s of the fuel particles, the diameter d l of the air particles, the density ρ a of the air particles, the surface tension σ, and the relative velocity vector u r between the two particles, the dimensionless collision parameter B, Weber number We, and particle size ratio Δ are calculated:

[0086] In this embodiment, a method for characterizing the comprehensive influence of the physical properties and kinetic states of fuel and air particles on the collision result is provided, and a method for constructing a collision pulse spectrum diagram by coupling the Weber number with the eccentricity between the centers of mass of colliding particle pairs is also provided. As Figure 5 shown in the collision pulse spectrum diagram, the abscissa is the Weber number, which is related to the kinetic state and physical and chemical properties of the colliding particles; the ordinate is the collision parameter, which is related to the size and impact angle of the colliding particles; the three lines in the figure are the corresponding collision boundary lines, and the divided regions are the collision regions. Since there is no substantial mass and energy exchange between particles under the rebound mechanism, it is regarded as an ineffective collision during the mixed calculation, and only the other three (stretching separation, coalescence, self-reflection separation) effective collision mechanisms are considered. The Weber number reflects the fluid characteristics of particles with different physical properties in different motion states, while the eccentricity between the centers of mass of particle pairs reflects the degree of collision contact. Using the pulse spectrum diagram, the region to which the real-time collision result belongs can be accurately determined according to the real-time Weber number and eccentricity of the colliding particle pairs, so as to perform targeted calculations of the mass exchange mechanism. Therefore, it can comprehensively reflect the spray mixing dynamics of fuels with different physical properties under variable injection strategies, expand the application range and improve the prediction accuracy.

[0087] Embodiment 5 is a further limitation on the method for calculating the fuel and air mixing process of a marine internal combustion engine described in Embodiment 4. In this embodiment, Step 4 is further limited, specifically including:

[0088] Step 4 includes:

[0089] Step 4.1: According to the collision parameter B and the particle size ratio Δ, calculate the coefficient τ and the ratio χ of the interaction region of air particles to their volume: τ = (1 - B)(1 + Δ),

[0090] Step 4.2: According to the collision parameter B, the particle size ratio Δ, the shape factor φ E and the ratio χ of the interaction region of air particles to their volume, calculate the lower rebound boundary line f 1 (B - We):

[0091]

[0092] Step 4.3: According to the collision parameter B and the particle size ratio Δ, calculate the dividing line f 2 (B - We) of coalescence and stretching separation of particle pairs during collision:

[0093]

[0094] Step 4.4: According to the collision parameter B and the particle size ratio Δ, calculate the parameters ξ, η sand η L : ξ = (1 / 2)B(1 + Δ), η S = 2(1 - ξ) 2 (1 - ξ 2 ) 1 / 2 -1, η L = 2(Δ - ξ) 2 (Δ 2 - ξ 2 ) 1 / 2 - Δ 3 ;

[0095] Step 4.5: According to the particle size ratio Δ, parameter η s and η L , calculate the boundary line f 3 (B - We) for the coalescence and self - reflexive separation of particle collisions:

[0096]

[0097] In this embodiment, a method for dividing three effective collision regions, namely tensile separation, coalescence, and self - reflexive separation, is provided. According to the above three boundary lines (the lower bounce - limit boundary line, the boundary line for coalescence and tensile separation, and the boundary line for coalescence and self - reflexive separation), the three effective collision regions of tensile separation, coalescence, and self - reflexive separation can be clearly and refinedly divided on the above - mentioned pulse spectrum diagram. Then, by performing quantitative calculations on specific mass exchange mechanisms within their respective effective collision regions, the real - time mixing state of fuel and air can be calculated more scientifically, truly, accurately, and quickly, greatly improving the prediction accuracy.

[0098] Embodiment Six is a further limitation on the method for calculating the fuel - air mixing process of a marine internal combustion engine described in Embodiment Five. In this embodiment, Step 5 is further limited, specifically including:

[0099] Step 5 includes:

[0100] Step 5.1: During the tensile separation process, binary particle pairs undergo non - central collisions, and some of their regions exchange substances with each other. Assume that the collision contact regions of fuel particle P s and air particle P l aggregate together to form a new homogeneous spherical particle P k . At the same time, assume that the fuel mass fractions f s and f l , velocities u s and u l , densities ρ s and ρ l , and specific enthalpies h f and ρ a in the non - collided regions of fuel particle Ps and h l Remains unchanged after stretching separation.

[0101] According to the ratio of the interaction area of ​​air particles to their volume, x, and the diameter of the fuel particles, d s and the diameter d of the air particles l , the fuel particle P is calculated s Collision area volume V ss 、Air particles P l Collision area volume V ls And the new particle P k The volume V k : V k =V ss +V ls ;

[0102] Step 5.2: According to the density of air particles ρ a , the density of the fuel particles ρ f 、Fuel particles P s Collision area volume V ss and air particles P l Collision area volume V ls , the fuel particle P is calculated s and air particles P l And the new particle P k Mass after stretching and n represents the calculation step, n and n+1 represent before and after the calculation respectively;

[0103] Step 5.3: According to the density of air particles ρ a , the density of the fuel particles ρ f 、Fuel particles P s Collision area volume V ss 、Air particles P l Collision area volume V ls 、Fuel particles P s and air particles P l Fuel mass fraction f s and f l , speed u s and u l , and specific enthalpy h s and h l , calculate the new particle P k The density ρ k , fuel mass fraction f k , speed u k and specific enthalpy h k :

[0104] Step 5.4: During the coalescence process, the binary particle pairs undergo head-on collisions and merge together. Assume that the entire fuel particle P s and the entire air particle P l coalesce to form a new homogeneous and stable particle P k , and the original binary particle pair disappears. Based on the volume V s and mass M sc of the entire fuel particle P sc and the volume V l and mass M lc of the entire air particle P lc , the volume V k and mass M k of the new particle P k are calculated as follows: V k = V sc + V lc , M k = M sc + M lc ;

[0105] Step 5.5: Based on the mass M s of the entire fuel particle P sc , the mass M l of the entire air particle P lc , the fuel mass fractions f s and f l of the fuel particle P s and the air particle P l , the velocities u s and u l , and the specific enthalpies h s and h l , the fuel mass fraction f k , the velocity u k , and the specific enthalpy h k of the new particle P k are calculated as follows:

[0106] Step 5.6: During the reflexive separation process, assume that within the computational time step Δt, the fuel particle P s passes through the air particle P l , forming a swept volume ΔV, and ΔV is proportional to the volume fraction of the fuel particle volume V sr in the entire spray region volume. Then the swept regions of the fuel particle P s and the air particle P l aggregate together to form a new homogeneous particle P k . And the fuel particle Ps and the physical properties of the unswept region of the air particles P l including the fuel mass fraction f s and f l velocity u s and u l density ρ f and ρ a and specific enthalpy h s and h l , remain unchanged after the reflexive separation compared to before the collision. According to the diameter d of the fuel particles s , fuel particles P s and air particles P l velocity u s and u l , calculation step size Δt, fuel particle volume V sr , density ρ of the air particles a and density ρ of the fuel particles f , the swept volume ΔV, fuel particles P s and air particles P l swept mass M sr and M lr are calculated as follows: M sr = ρ f ΔV, M lr = ρ a ΔV, where N represents the number of all particles in the entire spray region;

[0107] Step 5.7: According to the swept volume ΔV, fuel particles P s and air particles P l swept mass M sr and M lr , calculate the mass of fuel particles P s and air particles P l and new particles P k after the reflexive separation and

[0108] Step 5.8: According to the swept mass M s of fuel particles P l and air particles P sr and M lr , and the mass M k of the new particles P k after the reflexive separation, fuel particles P s and air particles P l fuel mass fraction f s and f l velocity u s and u l, and specific enthalpy h s and h l , the new particle P k is calculated for density ρ k , fuel mass fraction f k , velocity u k and specific enthalpy h k :

[0109] Step 5.9: For the collision of mixture particles with two different fuel concentrations during the mixing process, according to the size, the mixture particles with a smaller diameter are represented by P s , and the mixture particles with a larger diameter are represented by P l . Then, according to the mixing mechanism of pure fuel particles and pure air particles, repeat steps 3, 4, and 5.1 - 5.8 until the calculation ends to obtain the fuel concentration and air concentration in each particle.

[0110] In this embodiment, a method for abstractly and simplifying the description of the physical process of particle collision under different effective collision mechanisms is provided, as well as a method for quantitatively calculating and obtaining the component concentration, kinetics, and thermodynamic state after fuel and gas mixing (the fuel mass fraction represents the component concentration, the velocity represents the kinetic state, and the specific enthalpy represents the thermodynamic state). This method simplifies the calculation process of fuel and air mixing, can scientifically and truly reflect the dynamic material exchange under different mixing mechanisms, has high calculation accuracy, fast calculation speed, and wide application range.

[0111] Embodiment Seven, this embodiment further limits the calculation method of the fuel and air mixing process of a marine internal combustion engine described in Embodiment Six. In this embodiment, step 2 is further limited, specifically including:

[0112] Step 2 further includes:

[0113] According to the total mass M s of the spray zone, the turbulence generation rate G, the turbulence mean length scale L, and the collision coefficient C col , the turbulent kinetic energy k of the spray zone and the collision frequency ω between fuel particles and air particles are calculated:

[0114] In this embodiment, a calculation method for the collision frequency is provided. This collision frequency is applied to determine the end time of the calculation in step 5.9, that is, when the total number of particle pair collisions reaches the calculated collision frequency, the calculation ends. This method determines the particle collision frequency through the turbulence intensity in the combustion chamber, truly reflects the influence law of factors such as high-pressure fuel injection, gas vortex, and combustion expansion on the fuel and gas mixing rate, improves the accuracy of the mixing process calculation, and at the same time has a wide application range, and can be applied to engines under different injection pressures, different working conditions, and different combustion modes.

[0115] Embodiment 8. This embodiment is based on the embodiment of a calculation method for the fuel and air mixing process of a marine internal combustion engine as described above, and specifically includes:

[0116] Step 1. According to the nozzle diameter contraction coefficient C d , the spray cross-section velocity and the volume fraction distribution factor β, the effective injection velocity U eff (t), the effective nozzle diameter d eq , the spray cone angle θ, and the fuel injection duration t j , calculate the instantaneous spray jet penetration distance S tip and the spray volume V spray :

[0117] Step 2. According to the ambient gas density ρ a , the spray volume change rate the fuel mass injection rate the fuel density ρ f and the spray cross-section velocity and the volume fraction distribution factor β, calculate the air entrainment rate

[0118] Step 3. By means of the discretization assumption, the fuel injected and the air entrained within the calculation step are respectively abstracted into uniform spherical particles. According to the fuel mass m f and the density ρ f and the mass of the entrained air m a and the density ρ a , calculate the volume V s and the diameter d s of the fuel particles and the volume V l and the diameter d l of the air particles:

[0119] According to the total mass M s in the spray zone, the turbulence generation rate G, the turbulence mean length scale L, and the collision coefficient C col , calculate the turbulent kinetic energy k in the spray zone and the collision frequency ω between the fuel particles and the air particles: Used to determine the collision frequency, that is, the total number of particle collision calculations. After completing the corresponding number of collisions, the calculation in step 18 stops.

[0120] Step 4. According to the lateral displacement b between the mass centers of the fuel particles and the air particles, the diameter d s of the fuel particles, the diameter d l of the air particles, and the density ρ of the air particlesa and the surface tension σ and the relative velocity vector u between two particles r , the dimensionless collision parameter B, Weber number We and particle size ratio Δ are calculated as follows:

[0121] Step 5, according to the collision parameter B and the particle size ratio Δ, the coefficient τ and the ratio χ of the interaction region between the air particle and its volume are calculated: τ = (1 - B)(1 + Δ),

[0122] Step 6, according to the collision parameter B, the particle size ratio Δ, and the shape factor φ E and the ratio χ of the interaction region between the air particle and its volume, the lower bounce boundary line f of the particle pair collision is calculated 1 (B - We):

[0123] Step 7, according to the collision parameter B and the particle size ratio Δ, the dividing line f between coalescence and stretching separation of the particle pair collision is calculated 2 (B - We): f 2 (B ∼ We)

[0124] Step 8, according to the collision parameter B and the particle size ratio Δ, the parameters ξ, η s and η L are calculated as follows: ξ = (1 / 2)B(1 + Δ), η S = 2(1 - ξ) 2 (1 - ξ 2 ) 1 / 2 - 1, η L = 2(Δ - ξ) 2 (Δ 2 - ξ 2 ) 1 / 2 - Δ 3 ;

[0125] Step 9, according to the particle size ratio Δ, the parameter η s and η L , the dividing line f between coalescence and reflexive separation of the particle pair collision is calculated 3 (B ∼ We):

[0126] Step 10, during the stretching separation shown in Figure 2 , the binary particle pair undergoes an off - center collision, and their partial regions exchange substances with each other. Assume that the collision contact regions of the fuel particle P s and the air particle P l aggregate together to form a new homogeneous spherical particle P k . At the same time, assume that the fuel particle Ps and the fuel mass fraction f l in the non-collision region of the air particles P s and f l velocity u s and u l density ρ f and ρ a as well as the specific enthalpy h s and h l remain unchanged after stretching and separation.

[0127] Based on the ratio χ of the interaction region of air particles to their volume, the diameter d of fuel particles s and the diameter d of air particles l , the collision region volume V s of the fuel particle P ss , the collision region volume V l of the air particle P ls and the volume V k of the new particle P k are calculated as follows: V k = V ss + V ls ;

[0128] Step 11, based on the density ρ of air particles a , the density ρ of fuel particles f , the collision region volume V s of the fuel particle P ss and the collision region volume V l of the air particle P ls , the masses of the fuel particle P s , the air particle P l and the new particle P k after stretching and separation are calculated. and n represents the calculation step, for example, n and n + 1 represent before and after the calculation respectively.

[0129] Step 12, based on the density ρ of air particles a , the density ρ of fuel particles f , the collision region volume V s of the fuel particle P ss , the collision region volume V l of the air particle P ls , the fuel mass fraction f s of the fuel particle P l and the air particle P s and f l velocity u s and u l , as well as the specific enthalpy h sand h l , the new particle P is calculated k for its density ρ k , fuel mass fraction f k , velocity u k and specific enthalpy h k :

[0130] Step 13, during the coalescence process shown in Figure 3 , the binary particle pairs undergo a head-on collision and merge together. Assume that the entire fuel particle P s and the entire air particle P l coalesce to form a new homogeneous and stable particle P k , while the original binary particle pair disappears. Based on the volume V s and mass M sc of the entire fuel particle P sc and the volume V l and mass M lc of the entire air particle P lc , the volume V k and mass M k of the new particle P are calculated k : V k =V sc +V lc , M k =M sc +M lc ;

[0131] Step 14, based on the mass M s of the entire fuel particle P sc , the mass M l of the entire air particle P lc , the fuel mass fraction f s of the fuel particle P l and the air particle P s and f l , the velocity u s and u l , as well as the specific enthalpy h s and h l , the fuel mass fraction f k , velocity u k and specific enthalpy h k of the new particle P are calculated k :

[0132] Step 15, during the self-reflective separation process shown in Figure 4 , assume that within the calculation step size Δt, the fuel particle P s passes through the air particle Pl , a swept volume ΔV is formed, and ΔV is proportional to the volume fraction of the fuel particles in the volume of the entire spray region. Then, the swept regions of the fuel particle P sr and the swept regions of the air particles P s aggregate together to form a new homogeneous particle P l . And the physical properties of the unswept regions of the fuel particle P k and the air particles P s , including the fuel mass fraction f l and f s , the velocity u l and u s , the density ρ l and ρ f , and the specific enthalpy h a and h s , etc., remain unchanged after the reflexive separation compared to before the collision. According to the diameter d l of the fuel particles, the velocity u s of the fuel particle P s and the velocity u l of the air particle P s and u l , the calculation step size Δt, the volume V sr of the fuel particles, the density ρ a of the air particles, and the density ρ f of the fuel particles, the swept volume ΔV, the swept mass M s of the fuel particle P l and the swept mass M sr and M lr are calculated as follows: M sr = ρ f ΔV, M lr = ρ a ΔV; N represents the number of all particles in the entire spray region;

[0133] Step 16, according to the swept volume ΔV, the swept mass M s of the fuel particle P l and the swept mass M sr and M lr of the air particle P s and the air particle P l , the masses of the fuel particle P k and the air particle P and

[0134] Step 17, according to the swept mass M s of the fuel particle P l and the swept mass M sr and Mlr and the new particle P after reflexive separation k with mass M k 、fuel particle P s and air particle P l with fuel mass fraction f s and f l 、velocity u s and u l 、and specific enthalpy h s and h l ,the density ρ of the new particle P is calculated k 、fuel mass fraction f k 、velocity u k and specific enthalpy h k as follows k :

[0135] Step 18, for the collision of mixture particles with two different fuel concentrations during the mixing process, according to the size, the mixture particles with smaller diameter are represented by P s and the mixture particles with larger diameter are represented by P l . Then, according to the mixing mechanism of the above pure fuel particles and pure air particles (the above refers to Steps 3 to 17, which take the collision and exchange of pure fuel particles and pure air particles as examples and are equally applicable to the subsequent collision and exchange process of the mixed particles, including the collision of mixture particles and fuel particles, the collision of mixture particles and air particles, the collision of mixture particles and mixture particles, etc. No matter which two types of property particles collide, they all strictly follow the same calculation process: first establish the collision pulse spectrum diagram, determine the collision boundary line, divide each effective collision region, and then perform the corresponding calculation of momentum, mass and energy exchange of particle pairs for different effective collision regions);

[0136] Just repeat the calculation process of Steps 4 to 17 until the calculation ends. For example, when the total number of particle pair collisions reaches the calculated collision frequency (the calculation method of the collision frequency is shown in Step 3), the calculation ends. After the calculation ends, the fuel concentration and air concentration in each particle can be obtained, thus providing accurate information for the subsequent chemical reaction combustion process of fuel and air.

[0137] The above is only a description of the preferred specific implementation manner of the present invention, and does not limit the concept and scope of the present invention. Without departing from the innovative concept of the present invention and the scope protected by the claims, any modifications, variations and improvements made by those skilled in the art based on the technical solution of the present invention shall fall within the protection scope of the present invention. The technical content claimed by the present invention has been fully recorded in the claims.

Claims

1. A method for calculating the mixing process of fuel and air for a marine internal combustion engine, characterized in that: The method comprises: Step 1: Obtain the spray penetration distance according to the fuel injection conditions, and calculate the air entrainment rate through the spray penetration distance; Step 2: Based on the discretization assumption, the gaseous or liquid fuel injected and the air sucked in each calculation step are abstracted into uniform spherical particles, and the volume and diameter of the fuel particles and the volume and diameter of the air particles are calculated according to the fuel injection mass and the air entrainment mass; Step 3: Based on fluid theory, the Weber number is used to characterize the comprehensive influence of the physical properties and dynamic states of the fuel and air particles on the collision results, and the Weber number is coupled with the eccentricity between the center of mass of the colliding particle pair to construct a collision spectrum; Step 4: According to the collision parameters, particle size ratio and related parameters, the lower limit boundary of the rebound of the particle pair collision, the boundary between coalescence and stretching separation, and the boundary between coalescence and self-reflexive separation are determined, and three effective collision regions of stretching separation, coalescence and self-reflexive separation are divided; Step 5: Abstract and simplify the description of the particle collision physics process under different effective collision mechanisms, and quantitatively calculate the mass and momentum of the colliding particles and the energy exchange process to obtain the component concentration and kinetic and thermodynamic state of the fuel and gas mixture; Step 1 includes: Step 1.1: According to the nozzle diameter contraction coefficient C d , spray cross-sectional velocity and volume fraction distribution factor β, effective injection velocity U of the spray jet eff (t), effective nozzle diameter d eq , spray cone angle θ and injection duration t j , the instantaneous spray jet penetration distance S is calculated tip and spray volume V spray : Step 1.2: According to the density of air particles ρ a , spray volume change rate Fuel mass injection rate The density of the fuel particles is f As well as the spray cross-sectional velocity and volume fraction distribution factor β, the air entrainment rate is calculated Step 5 includes: Step 5.1: During the stretching separation process, the binary particle pairs collide non-centrally and their parts exchange matter with each other. Assume that the fuel particle P s and air particles P l The collision contact areas are aggregated together to form a new homogeneous spherical particle P k ; At the same time, it is assumed that the fuel particle P s and air particles P l The fuel mass fraction f in the non-collision area s and f l , speed u s and u l , density ρ f and ρ a and specific enthalpy h s and h l Remains unchanged after stretching separation; According to the ratio of the interaction area of ​​air particles to their volume, x, and the diameter of the fuel particles, d s and the diameter d of the air particles l , the fuel particle P is calculated s Collision area volume V ss 、Air particles P l Collision area volume V ls And the new particle P k The volume V k : V k =V ss +V ls ; Step 5.2: According to the density of air particles ρ a , the density of the fuel particles ρ f 、Fuel particles P s Collision area volume V ss and air particles P l Collision area volume V ls , the fuel particle P is calculated s and air particles P l And the new particle P k Mass after stretching and n represents the calculation step, n and n+1 represent before and after the calculation respectively; Step 5.3: According to the density of air particles ρ a , the density of the fuel particles ρ f 、Fuel particles P s Collision area volume V ss 、Air particles P l Collision area volume V ls 、Fuel particles P s and air particles P l Fuel mass fraction f s and f l , speed u s and u l , and specific enthalpy h s and h l , calculate the new particle P k The density ρ k , fuel mass fraction f k , speed u k and specific enthalpy h k : Step 5.4: During the coalescence process, the binary particle pairs collide head-on and merge together; assuming that the entire fuel particle P s and the entire air particle P l Agglomerate together to form a new homogeneous and stable particle P k , and the original binary particle pair disappears; according to the entire fuel particle P s Volume V sc and quality M sc and the entire air particle P l Volume V lc and quality M lc , calculate the new particle P k The volume V k and quality M k :V k =V sc +V lc 、M k =M sc +M lc ; Step 5.5: According to the whole fuel particle P s Quality M sc , the entire air particle P l Quality M lc 、Fuel particles P s and air particles P l Fuel mass fraction f s and f l , speed u s and u l , and specific enthalpy h s and h l , calculate the new particle P k Fuel mass fraction f k , speed u k and specific enthalpy h k : Step 5.6: During the reflexive separation process, assume that within the calculation step Δt, the fuel particle P s Passing through air particles P l , forming a swept volume ΔV, and ΔV is related to the fuel particle volume V sr The volume fraction of the fuel particle P in the entire spray area is proportional to s The swept area and air particles P l The swept area aggregates together to form a new homogeneous particle P k ; and the fuel particle P s and air particles P l The physical properties of the unswept area, including the fuel mass fraction f s and f l , speed u s and u l , density ρ f and ρ a and specific enthalpy h s and h l , after the reflexive separation, it remains unchanged from before the collision; according to the diameter d of the fuel particle s 、Fuel particles P s and air particles P l The speed u s and u l , calculation step length Δt, fuel particle volume V sr , the density of air particles ρ a and the density of the fuel particles ρ f , the swept volume ΔV and fuel particles P are calculated s and air particles P l The sweep mass M sr and M lr : M sr =ρ f ΔV、M lr =ρ a ΔV, N represents the number of all particles in the entire spray area; Step 5.7: According to the swept volume ΔV, fuel particles P s and air particles P l The sweep mass M sr and M lr , the fuel particle P after self-reflexive separation is calculated s and air particles P l And the new particle P k Quality and Step 5.8: According to the fuel particle P s and air particles P l The sweep mass M sr and M lr And the new particle P after self-reflexive separation k The quality of M k 、Fuel particles P s and air particles P l Fuel mass fraction f s and f l , speed u s and u l , and specific enthalpy h s and h l , calculate the new particle P k The density ρ k , fuel mass fraction f k , speed u k and specific enthalpy h k : Step 5.9: For the collision of two mixture particles with different fuel concentrations during the mixing process, separate the mixture particles with smaller diameters by P. s Indicates that the mixture particles with larger diameters are denoted by P l Then, according to the mixing mechanism of pure fuel particles and pure air particles, steps 3, 4 and steps 5.1-5.8 are repeated until the calculation is completed to obtain the fuel concentration and air concentration in each particle.

2. The method for calculating the mixing process of fuel and air for a marine internal combustion engine according to claim 1, characterized in that: Step 2 includes: Through the discretization assumption, the fuel injected and the air sucked in within the calculation step are abstracted into uniform spherical particles. f and density ρ f And the air mass m a and density ρ a , calculate the volume V of the fuel particle s and diameter d s and the volume V of the air particle l and diameter d l :

3. The method for calculating the mixing process of fuel and air for a marine internal combustion engine according to claim 2, characterized in that: Step 3 includes: According to the lateral displacement b between the center of mass of the fuel particle and the air particle, the diameter d of the fuel particle s , the diameter of the air particles d l , the density of air particles ρ a and the surface tension σ and the relative velocity vector u between the two particles r , the dimensionless collision parameter B, Weber number We and particle size ratio Δ are calculated:

4. The method for calculating the mixing process of fuel and air for a marine internal combustion engine according to claim 3, characterized in that: Step 4 includes: Step 4.1: Based on the collision parameter B and the particle size ratio Δ, the coefficient τ and the ratio of the interaction area of ​​the air particle to its volume χ are calculated: τ = (1-B)(1+Δ), Step 4.2: Based on the collision parameter B, particle size ratio Δ, shape factor φ E The ratio of the interaction area of ​​the air particle to its volume, χ, is used to calculate the lower limit boundary line f1(B-We) of the rebound of the particle collision: Step 4.3: According to the collision parameter B and the particle size ratio Δ, the boundary line f2 (B~We) between the aggregation and stretching separation of the particle pair collision is calculated: Step 4.4: Calculate the parameters ξ and η based on the collision parameter B and the particle size ratio Δ. s and η L :ξ=(1 / 2)B(1+Δ),η S =2(1-ξ) 2 (1-ξ 2 ) 1 / 2 -1, η L =2(Δ-ξ) 2 (Δ 2 -ξ 2 ) 1 / 2 -Δ 3 ; Step 4.5: According to the particle size ratio Δ and parameter η s and η L , the boundary line f3(B~We) between the coalescence and reflexive separation of particle pairs is calculated:

5. The method for calculating the mixing process of fuel and air for a marine internal combustion engine according to claim 1, characterized in that: Step 2 also includes: According to the total mass M of the spray area s , turbulence generation rate G, turbulence average length scale L and collision coefficient C col , the turbulent kinetic energy k in the spray zone and the collision frequency ω between fuel particles and air particles are calculated:

6. A computer device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor runs the computer program stored in the memory, the steps of the method according to any one of claims 1 to 5 are performed.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a plurality of computer instructions, and the plurality of computer instructions are used to enable a computer to execute the method according to any one of claims 1 to 5.

8. An electronic device, characterized in that: include: at least one processor; as well as, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 5.

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