A quantitative calculation method for engine oil-air mixing process based on vector collaboration

Abstract

This invention discloses a quantitative calculation method for engine fuel-air mixing process based on vector collaboration, relating to the field of engines. The method includes: S1, establishing an engine model divided into multiple grids; S2, acquiring the volume and spatial coordinate information of each grid in the engine model, as well as the physical parameters of the fuel in each grid; S3, calculating the effective transport rate of the fuel in the target grid based on the physical parameters of the fuel in the target grid, and the volume and spatial coordinate information of each grid; S4, calculating the total effective transport rate of the fuel in all grids within the engine cylinder based on the effective transport rate of the fuel in each grid. This invention can directly and accurately quantify the fuel-air mixing rate, which not only helps to deepen the understanding of fuel atomization, evaporation, and mixing mechanisms, but also provides important data support for combustion chamber optimization design, fuel injection strategy optimization, and emission control.

Description

Technical Field

[0001] This invention relates to the field of engines, and more specifically to a quantitative calculation method for engine oil-gas mixing process based on vector collaboration. Background Technology

[0002] In related technologies, most methods are used to quantify the air-fuel mixture rate, including: statistical analysis methods, constructing characteristic parameters to quantitatively describe the air-fuel mixture process based on an understanding of relevant combustion models, and quantitative research on the diesel engine mixture process based on the concept of multi-field synergy. However, statistical analysis methods can only calculate the overall in-cylinder average value, lacking spatial information on the air-fuel mixture rate; constructing characteristic parameters to quantitatively describe the air-fuel mixture process based on an understanding of relevant combustion models only considers the influence of turbulence on air-fuel mixture, without considering the effects of diffusion and convection on air-fuel mixture; quantitative research on the diesel engine mixture process based on the concept of multi-field synergy ignores the basic field strength. For example, when the concentration field strength is basically the same, but the velocity field is very strong, the in-cylinder mass transfer and air-fuel mixture process may be more intense under conditions with low field synergy.

[0003] Therefore, there is an urgent need for a quantitative method for hydrocarbon mixing processes that can characterize spatial information and consider the effects of diffusion, convection, and the synergistic effects of multiple fields on hydrocarbon mixing. Summary of the Invention

[0004] In view of this, the present invention provides a quantitative calculation method for engine oil-gas mixing process based on vector cooperation, in order to solve the technical problems in related technologies such as the lack of spatial information on oil-gas mixing rate, failure to consider the influence of diffusion, convection and the synergistic effect of multiple fields on oil-gas mixing.

[0005] This invention provides a quantitative calculation method for engine oil-air mixing process based on vector cooperation, the method comprising:

[0006] S1. Establish an engine model divided by multiple grids; the engine model forms a physical field; the physical field includes: turbulence field, concentration field, density field, and velocity field;

[0007] S2. Obtain the volume and spatial coordinate information of each grid in the engine model, as well as the physical parameters of the fuel in each grid; the physical parameters include density, velocity, fuel mass fraction, turbulent kinetic energy, and turbulent kinetic energy dissipation rate;

[0008] S3. Calculate the effective transport rate of fuel in the target grid based on the physical parameters of the fuel in the target grid, the volume of each grid, and the spatial coordinate information; the target grid can be any one of multiple grids.

[0009] S4. Calculate the total effective transport rate of fuel in all grids within the engine cylinder based on the effective transport rate of fuel in each grid.

[0010] In one optional implementation, the engine model is a CFD simulation model that includes a turbulence model, a spray model, a combustion model, and an in-cylinder geometry model.

[0011] In one optional implementation, S3 includes:

[0012] S31. Calculate the turbulent diffusion coefficient corresponding to the target grid based on the turbulent kinetic energy and turbulent kinetic energy dissipation rate of the fuel in the target grid.

[0013] S32. Based on the turbulent diffusion coefficient and volume of the target grid, and the fuel mass fraction and density of the fuel in the target grid, calculate the effective diffusion and transport rate of the fuel in different directions of the target grid.

[0014] S33. Calculate the effective convective transport rate of fuel in different directions of the target grid based on the density, mass fraction and velocity of the fuel in the target grid.

[0015] S34. The effective transport rate of fuel in the target grid is obtained by superimposing the sum of the effective diffusion transport rates of fuel in different directions of the target grid and the sum of the effective convective transport rates of fuel in different directions of the target grid.

[0016] In one optional implementation, S32 includes:

[0017] ;

[0018] in, This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid Effective diffusion transport rate in the direction of diffusion.

[0019] In one optional implementation, S33 includes:

[0020] ;

[0021] in, This represents the density of fuel in the target grid. Let the fuel velocity be the velocity within the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid Effective convective transport rate in the direction.

[0022] In one optional implementation, S34 includes:

[0023] S341, Based on fuel level in the target grid Effective diffusion transport rate in the direction Fuel in the target grid y Effective diffusion transport rate in the direction Fuel in the target grid z Effective diffusion transport rate in the direction Calculate fuel in the target grid , y The sum of the effective diffusion transport rates in the z-direction :

[0024] ;

[0025] in, , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid y Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid z Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid , , The sum of the effective diffusion transport rates in each direction; This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh;

[0026] S342, Based on fuel level in the target grid Effective convective transport rate in the direction Fuel in the target grid y Effective convective transport rate in the direction Fuel in the target grid z Effective convective transport rate in the direction Calculate fuel in the target grid , y The sum of effective convective transport rates in the z-direction :

[0027] ;

[0028] in, , , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective convective transport rate in the direction, For fuel in the target grid y Effective convective transport rate in the direction, For fuel in the target grid z Effective convective transport rate in the direction, For fuel in the target grid , , The sum of effective convective transport rates in each direction. For fuel in the target grid velocity in the direction, For fuel in the target grid y velocity in the direction, For fuel in the target grid z velocity in the direction, This represents the density of fuel in the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh;

[0029] S343, Based on fuel level in the target grid , y The sum of effective convective transport rates in the z-direction Fuel in the target grid , y The sum of the effective diffusion transport rates in the z-direction Calculate the effective transport rate of fuel in the target grid. :

[0030] ;

[0031] in, This represents the effective transport rate of fuel in the target grid.

[0032] In one alternative implementation, S4 includes:

[0033] ;

[0034] in, For the first cylinder of the engine The effective transport rate of each grid n This represents the total number of grids in all engine cylinders.

[0035] In an alternative implementation, after S2, the method further includes:

[0036] The effective transport rate coefficient of fuel in the target grid is calculated based on the physical parameters of fuel in the target grid and the spatial coordinate information of the target grid.

[0037] The effective transport rate of fuel in the target grid is calculated based on the effective transport rate coefficient of fuel in the target grid and the volume corresponding to the target grid. The target grid can be any one of multiple grids.

[0038] The total effective transport rate of fuel in all grids within the engine cylinder is calculated based on the effective transport rate of fuel in each grid.

[0039] In an alternative implementation, after S2, the method further includes:

[0040] The effective transport rate coefficient of fuel in the target grid is calculated based on the physical parameters of fuel in the target grid and the spatial coordinate information of the target grid.

[0041] Based on the internal volume of the engine cylinder and the effective transport rate coefficient corresponding to the target grid, calculate the volume average value of the effective fuel transport rate coefficient in the entire engine cylinder;

[0042] Based on the volume average value, the total effective transport rate of all grids within the engine cylinder is calculated.

[0043] In one optional implementation, the calculation process for the total effective transport rate of all grids within the engine cylinder includes:

[0044] ;

[0045] ;

[0046] ;

[0047] ;

[0048] ;

[0049] in, This represents the volume average of the effective fuel transport rate coefficient throughout the entire engine cylinder. This refers to the internal volume of the engine cylinder.

[0050] Based on the fundamental principles of mass transfer, this invention quantifies the contributions of diffusion and convection to oil-gas mixing. It also considers the spatial information of the oil-gas mixing rate, as well as the influence of turbulent fields, concentration fields, density fields, velocity fields, and the synergistic effects between these fields on oil-gas mixing. This precise quantification of the oil-gas mixing rate not only helps to deepen the understanding of fuel atomization, evaporation, and mixing mechanisms, but also provides important data support for combustion chamber optimization design, fuel injection strategy optimization, and emission control. Attached Figure Description

[0051] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0052] Figure 1 This is a flowchart illustrating a quantitative calculation method for engine oil-gas mixing process based on vector collaboration according to an embodiment of the present invention.

[0053] Figure 2 According to an embodiment of the present invention, fuel is in the target grid , , A schematic diagram illustrating the derivation principle of the sum of effective diffusion transport rates in each direction;

[0054] Figure 3 According to an embodiment of the present invention, fuel is in the target grid , , A schematic diagram illustrating the derivation principle of the sum of effective diffusion convection velocities in different directions;

[0055] Figure 4 This is the effective transport coefficient of the in-cylinder space of a certain engine model according to an embodiment of the present invention. Cloud map;

[0056] Figure 5 This is a graph showing the total effective transport rate R of the engine cylinder space of a certain model according to an embodiment of the present invention as a function of time. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In the field of engines, air-fuel mixing is crucial to overall engine performance. For example, in the combustion process of a diesel engine, the air-fuel mixing rate is a key parameter affecting combustion characteristics, emission characteristics, and fuel economy. Therefore, accurately quantifying the air-fuel mixing rate not only helps to deepen the understanding of fuel atomization, evaporation, and mixing mechanisms, but also provides important data support for combustion chamber optimization design, fuel injection strategy optimization, and emission control.

[0059] In related technologies, methods for quantifying the oil-gas mixing rate mainly fall into three categories: statistical analysis, constructing characteristic parameters that quantitatively describe the oil-gas mixing process based on an understanding of relevant combustion models, and quantitative research on the diesel engine mixing process based on the concept of multi-field synergy.

[0060] Firstly, statistical analysis methods refer to quantifying the overall air-fuel mixture rate in the engine cylinder by statistically analyzing the mass of the air-fuel mixture within the suitable combustion range of the in-cylinder equivalence ratio, or by statistically analyzing the mass of air within the fuel grid in the cylinder. However, this method can only calculate the overall average value in the engine cylinder, lacking spatial information on the air-fuel mixture rate.

[0061] Secondly, the construction of quantitative characteristic parameters describing the oil-gas mixing process based on the understanding of relevant combustion models mainly refers to the assumption, based on the understanding of the generalized turbulent breakup model (EBU), that the combustion rate is equal to the turbulent mixing rate, i.e., the oil-gas mixing rate is proportional to the reciprocal of the turbulent mixing time. However, this method only considers the influence of turbulence on oil-gas mixing, without considering the effects of diffusion and convection on oil-gas mixing.

[0062] Third, quantitative research on diesel engine mixing processes based on the concept of multi-field synergy refers to research conducted on the basis of "field effect." The in-cylinder fuel-air mixing process in a diesel engine is the result of the coupled and synergistic effects of multiple physical fields, the most important of which are the velocity field and the concentration field. The basic principle of the field effect states that if the velocity direction is aligned with the fuel concentration gradient direction, it will accelerate the fuel mass transfer process. The angle between the velocity vector direction and the concentration gradient direction is defined as the field effect angle; the smaller this angle, the stronger the in-cylinder mass transfer and fuel-air mixing process. Although velocity weighting, concentration weighting, and grid volume weighting have been subsequently adopted, the concept of the field effect angle neglects the important information of the underlying field strength. For example, when the concentration field strength is basically the same, but the velocity field is very strong, a smaller field effect angle may result in a stronger in-cylinder mass transfer and fuel-air mixing process, ignoring the influence of the synergistic effects of multiple physical fields on fuel-air mixing.

[0063] Based on this, embodiments of the present invention provide a quantitative calculation method for engine oil-gas mixing process based on vector collaboration, which can characterize the spatial information of the entire engine cylinder and consider the influence of diffusion and the synergistic effect of multiple fields on oil-gas mixing, and can directly quantify the oil-gas mixing rate.

[0064] Figure 1 This is a quantitative calculation method for engine oil-gas mixing process based on vector cooperation according to an embodiment of the present invention. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than that shown here.

[0065] like Figure 1 As shown, the process includes the following steps:

[0066] S1. Establish an engine model divided by multiple grids; the engine model forms a physical field; the physical field includes: turbulence field, concentration field, density field, and velocity field.

[0067] In one alternative implementation, the engine model is a CFD simulation model that includes a turbulence model, a spray model, a combustion model, and an in-cylinder geometry model.

[0068] Specifically, the engine model is a hybrid model composed of multiple sub-models, and it is implemented using computational fluid dynamics (CFD) simulation technology to comprehensively simulate and analyze the oil-gas mixing process inside the engine.

[0069] The engine model can mesh the in-cylinder geometry, which means discretizing the in-cylinder geometry into a series of small units. Each mesh is a micro-element hexahedron. By performing fluid dynamics analysis on each micro-element hexahedron, quantitative data on the in-cylinder fuel-air mixture, such as velocity, concentration, density, and fuel mass fraction, can be output.

[0070] For example, an engine model is built using CONVERGE 3.0 or a later version of the software, and the engine model is calibrated based on the measured test data.

[0071] S2. Obtain the volume and spatial coordinate information of each grid in the engine model, as well as the physical parameters of the fuel in each grid; the physical parameters include density, velocity, fuel mass fraction, turbulent kinetic energy, and turbulent kinetic energy dissipation rate.

[0072] The spatial coordinate information of each grid can be the coordinate information of the four corners of the infinitesimal hexahedron in three-dimensional space.

[0073] It should be noted that the volume and spatial coordinate information of each grid, as well as the physical parameters of the fuel in each grid, can be obtained directly from the engine model output, or calculated based on the engine model output.

[0074] S3. Calculate the effective transport rate of fuel in the target grid based on the physical parameters of the fuel in the target grid, the volume of each grid and the spatial coordinate information; the target grid is any one of multiple grids.

[0075] It should be noted that the embodiments of the present invention quantify the engine air-fuel mixing rate based on the fundamental principle of mass transfer. The core idea is to focus on whether the transport process (which includes two types: diffusion and convection) can affect the equivalence ratio. or fuel mass fraction Changes (equivalent ratio) With fuel mass fraction (Proportional), if a certain transport process does not cause the equivalent ratio or fuel mass fraction If the change in ... or fuel mass fraction If the change is significant, then the transport is either effective diffusion transport or effective convection transport.

[0076] Effective transport includes effective diffusion transport or effective convective transport, and correspondingly, effective transport rate includes effective diffusion transport rate or effective convective transport rate.

[0077] By obtaining the physical parameters of the fuel in the target grid, the volume of each grid, and the spatial coordinate information, the effective transport rate of the fuel in the target grid can be calculated.

[0078] S4. Calculate the total effective transport rate of fuel in all grids within the engine cylinder based on the effective transport rate of fuel in each grid.

[0079] In one optional implementation, step S3 includes:

[0080] S31. Calculate the turbulent diffusion coefficient corresponding to the target grid based on the turbulent kinetic energy and turbulent kinetic energy dissipation rate of the fuel in the target grid.

[0081] It should be noted that for the fuel diffusion process in the engine cylinder, including molecular diffusion and turbulent diffusion, although molecular diffusion still exists at the microscopic scale, turbulent diffusion plays a dominant role in most practical situations due to its higher diffusion rate and stronger mixing effect, while molecular diffusion can be ignored.

[0082] Turbulent diffusion coefficient for each grid It can be represented as:

[0083] ;

[0084] in, , It is a constant, with a value of 0.0845; For turbulent kinetic energy, ; The turbulent kinetic energy dissipation rate, ; This is the turbulent Schmidt number, with a value of 0.78.

[0085] Therefore, turbulent diffusion coefficient This can be further expressed as:

[0086] ;

[0087] Due to different positions within the engine cylinder and different times at the same position or The difference is evident from this, which shows that the turbulent diffusion coefficient It changes with time and space.

[0088] S32. Based on the turbulent diffusion coefficient and volume of the target grid, and the fuel mass fraction and density of the fuel in the target grid, calculate the effective diffusion and transport rate of fuel in different directions of the target grid.

[0089] In one optional implementation, step S32 includes:

[0090] ;

[0091] in, This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid Effective diffusion transport rate in the direction of diffusion.

[0092] It should be noted that, in this embodiment of the invention, fuel is used in the target grid. Effective diffusion transport rate in the direction Taking one example for calculation, similarly, others... y direction and z Effective diffusion transport rate in the direction , The calculation method is the same, and will not be repeated here.

[0093] S33. Based on the fuel density, fuel mass fraction and velocity in the target grid, calculate the effective convective transport rate of fuel in different directions of the target grid.

[0094] In one optional implementation, step S33 includes:

[0095] ;

[0096] in, This represents the density of fuel in the target grid. For fuel in the target grid velocity in the direction, This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid Effective convective transport rate in the direction.

[0097] It should be noted that, in this embodiment of the invention, fuel is used in the target grid. Effective convective transport rate in the direction Taking one example for calculation, similarly, others... y direction and z Effective convective transport rate in the direction , The calculation method is the same, and will not be repeated here.

[0098] S34. The effective transport rate of fuel in the target grid is obtained by superimposing the sum of the effective diffusion transport rates of fuel in different directions of the target grid and the sum of the effective convective transport rates of fuel in different directions of the target grid.

[0099] In one alternative implementation, step S34 includes:

[0100] S341, Based on fuel level in the target grid Effective diffusion transport rate in the direction Fuel in the target grid y Effective diffusion transport rate in the direction Fuel in the target grid z Effective diffusion transport rate in the direction Calculate fuel in the target grid , y The sum of the effective diffusion transport rates in the z-direction :

[0101] ;

[0102] in, , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid y Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid z Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid , , The sum of the effective diffusion transport rates in each direction; This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh;

[0103] S342, Based on fuel level in the target grid x Effective convective transport rate in the direction Fuel in the target grid y Effective convective transport rate in the direction Fuel in the target grid z Effective convective transport rate in the direction Calculate fuel in the target grid , y The sum of effective convective transport rates in the z-direction :

[0104] ;

[0105] in, , , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective convective transport rate in the direction, For fuel in the target grid y Effective convective transport rate in the direction, For fuel in the target grid z Effective convective transport rate in the direction, For fuel in the target grid , , The sum of effective convective transport rates in each direction. For fuel in the target grid velocity in the direction, For fuel in the target grid y velocity in the direction, For fuel in the target grid z velocity in the direction, This represents the density of fuel in the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh;

[0106] S343, Based on fuel level in the target grid , y The sum of the effective diffusion transport rates in the z-direction Fuel in the target grid , y The sum of effective convective transport rates in the z-direction Calculate the effective transport rate of fuel in the target grid. :

[0107] ;

[0108] in, This represents the effective transport rate of fuel in the target grid.

[0109] In one alternative implementation, step S4 includes:

[0110] ;

[0111] in, For the first cylinder of the engine The effective transport rate of each grid n This represents the total number of grids across all engine cylinders. This represents the total effective transport rate of all grids within the engine cylinder.

[0112] Furthermore, the following explains the derivation of the total effective transport rate of fuel in all grids within the engine cylinder:

[0113] 1. Fuel in the target grid , , The sum of effective diffusion transport rates in each direction The derivation process is as follows:

[0114] It should be noted that the infinitesimal hexahedron introduced below is a hexahedral mesh in CFD simulation, such as... Figure 2 As shown.

[0115] According to Fick's diffusion law (i.e., Fick's first law), we know that:

[0116] (1)

[0117] in, Represents fuel in a hexahedral micro-element Diffusion flux in the direction, i.e., fuel diffusion in the infinitesimal hexahedron. When diffusion transport occurs in a directional direction, it refers to the mass passing through a unit area per unit time, with the unit being... ; This is the diffusion coefficient, in units of... ; This refers to the fuel mass concentration.

[0118] It should be noted that the negative sign in formula (1) indicates that the direction of fuel diffusion is opposite to the direction of the concentration gradient.

[0119] At this time, within a unit of time, the fuel in the infinitesimal hexahedron x Mass of diffusion transport in the direction (That is, the diffusion transport rate) is:

[0120] (2)

[0121] Based on fuel mass concentration With fuel mass fraction The relationship shows that:

[0122] (3)

[0123] in, Let be the density of fuel in a hexahedral micro-element.

[0124] At this time, Substituting into formula (1), we get:

[0125] (4)

[0126] As can be seen from formula (4), fuel in a micro-element hexahedron Diffusion flux in the direction It can be decomposed into two parts, which can be seen as the superposition of two virtual processes. The first process is: the density of fuel on both sides of the plane. Same, but There is a mass fraction gradient of fuel in the direction; the second process is: the mass fraction of fuel on both sides of the plane. Same, but There is a density gradient of fuel in the direction.

[0127] It should be noted that the two sides of the plane represent the two sides of the left and right sides of the corresponding hexahedron of the infinitesimal element.

[0128] Both of the above processes will cause fuel to circulate in the micro-element hexahedron. Mass of diffusion transport in the direction change ， However, the second process does not affect the fuel mass fraction. Changes occur, constituting ineffective diffusion transport; therefore, effective diffusion transport is expressed as follows:

[0129] (5)

[0130] in, For fuel in a micro-element hexahedron Effective diffusion flux in the direction.

[0131] It should be noted that for the fuel diffusion process in the engine cylinder, including molecular diffusion and turbulent diffusion, although molecular diffusion still exists at the microscopic scale, turbulent diffusion plays a dominant role in most practical situations due to its higher diffusion rate and stronger mixing effect, while molecular diffusion can be ignored.

[0132] The turbulent diffusion coefficient can be defined as:

[0133] (6)

[0134] in, , It is a constant, with a value of 0.0845; For turbulent kinetic energy, ; The turbulent kinetic energy dissipation rate, ; This is the turbulent Schmidt number, with a value of 0.78.

[0135] Therefore, turbulent diffusion coefficient This can be further expressed as:

[0136] (7)

[0137] Due to different positions within the engine cylinder and different times at the same position or The difference is evident from this, which shows that the turbulent diffusion coefficient It changes with time and space.

[0138] In formula (7) Replace with formula (5) ,get:

[0139] (8)

[0140] Then, Replace the formula (2) Fuel was obtained in a micro-element hexahedron. The effective diffusion transport rate for diffusion transport in the directional direction is:

[0141] (9)

[0142] in, For the first The volume of a micro-element hexahedron shows that fuel exists within the micro-element hexahedron. The effective diffusion in the direction includes three terms. The first term is due to the turbulent diffusion coefficient on both sides of the grid. The difference is due to the density on both sides of the grid. The third item is caused by the different mass fraction gradients of fuel on both sides of the grid.

[0143] It should be noted that the two sides of the grid represent the left side of the left face and the right side of the right face of the corresponding hexahedron element.

[0144] In summary, fuel is within the target grid. , , The sum of effective diffusion transport rates in each direction for:

[0145] (10)

[0146] in, , The positive or negative sign represents the direction of effective diffusion. >0 indicates that the effective diffusion direction of the fuel is outward from the grid, reducing the stoichiometry within that grid; if <0 indicates that the effective diffusion direction of the fuel is towards the inside of the grid, which increases the stoichiometry within that grid.

[0147] in, The theoretical air-fuel ratio can be selected according to the type of fuel. For example, the theoretical air-fuel ratio of diesel is 14.3, and that of gasoline is 14.7.

[0148] 2. Fuel in the target grid , , The sum of effective convective transport rates in each direction The derivation process is as follows: Figure 3 As shown:

[0149] Convection transport refers to the process of material transfer caused by the macroscopic movement of the working fluid.

[0150] (11)

[0151] in, For fuel in a micro-element hexahedron Convection current in the direction, i.e., fuel flow in the infinitesimal hexahedron. The mass passing through a unit area per unit time during convective transport in a directional direction; Represents fuel in a hexahedral micro-element velocity in the direction, Fuel mass concentration, For fuel in a micro-element hexahedron Convective transport rate in the direction.

[0152] Formula (3) Substituting into equation (11), we get:

[0153] (12)

[0154] According to formula (12), fuel in a micro-element hexahedron Convective transport rate in the direction It consists of three parts, which can be viewed as the superposition of three virtual processes. The first process has the same density and velocity on both sides of the grid, with a fuel mass fraction gradient. The second process has the same fuel mass fraction and velocity on both sides of the grid, with a density gradient. The third process has the same fuel mass fraction and density on both sides of the grid, with a velocity gradient. All three processes lead to fuel mass transport, but only the first process causes a change in the fuel mass fraction within the grid. Therefore, fuel in the micro-element hexahedron... The effective convective transport rate in the direction is:

[0155] (13)

[0156] In summary, fuel is within the target grid. , , The sum of effective convective transport rates in each direction for:

[0157] (14)

[0158] in, , , Positive and negative signs represent the directionality of effective convective transport. This indicates that the effective convective transport direction is outward from the grid, and the equivalence ratio within the grid decreases. This indicates that the direction of effective convective transport is towards the inside of the grid, and the equivalent ratio within the grid increases.

[0159] 3. Fuel in the target grid , , The sum of effective diffusion transport rates in each direction Fuel in the target grid , , The sum of effective convective transport rates in each direction Superimposed to the effective transport rate .

[0160] Effective transport rate The expression is:

[0161] (15)

[0162] Effective transport rate The effects of in-cylinder turbulence, concentration, density, velocity fields, and the synergistic effects between these fields on oil-gas mixing were comprehensively considered.

[0163] It should be noted that the mass concentration or mass fraction of the fuel mentioned above refers to gaseous fuel.

[0164] The inside of an engine cylinder can be viewed as being composed of a mesh of many infinitesimal hexahedral elements, and the total effective transport rate within the entire engine cylinder... R for:

[0165] (16)

[0166] in, For the first cylinder of the engine The effective transport rate of each grid n This represents the total number of grids in all engine cylinders.

[0167] In an optional implementation, after step S2, the method further includes:

[0168] Calculate the effective transport rate coefficient corresponding to the target grid based on the physical parameters and spatial coordinate information of the target grid;

[0169] The effective transport rate coefficient and volume of the target grid are used to calculate the effective transport rate of the target grid, where the target grid is any one of multiple grids.

[0170] Calculate the total effective transport rate of all grids within the engine cylinder based on the effective transport rate corresponding to each grid.

[0171] Specifically, the effective diffusion transport coefficient is defined. Effective convective transport coefficient and effective transport coefficient The specific calculation method is as follows:

[0172] (17)

[0173] (18)

[0174] (19)

[0175] The transport coefficient is calculated because different mesh refinement strategies exist in CFD simulations. To eliminate the influence of mesh size on transport rate, the transport coefficient is used to quantify the effective transport intensity within the combustion chamber space. Furthermore, using the transport coefficient has the advantage of quantifying the effective transport intensity of engines with different cylinder diameters, as the expression for the transport coefficient is independent of mesh volume and combustion chamber volume.

[0176] (20)

[0177] (twenty one)

[0178] (twenty two)

[0179] It should be noted that the effective diffusion transport coefficients in the above formulas (20)-(22) are... Effective convective transport coefficient and effective transport coefficient The calculation process can be performed using the aforementioned fuel in the target grid. , , The sum of effective diffusion transport rates in each direction Fuel in the target grid , , The sum of effective convective transport rates in each direction Effective transport rate of fuel in the target grid The inverse operation yields the result.

[0180] To shorten the computation time, the effective diffusion transport coefficient can be calculated first. Effective convective transport coefficient and effective transport coefficient The part of differentiation, including , , , , Then calculate the effective diffusion transport coefficient. Effective convective transport coefficient and effective transport coefficient At this point, the calculated result , , , , Simply substitute the values. Finally, calculate the fuel level in the target grid. , , The sum of effective diffusion transport rates in each direction Fuel in the target grid , , The sum of effective convective transport rates in each direction, and the effective transport rate The transport coefficients are multiplied by the volume of their respective grids. This embodiment of the invention reduces the time spent on derivative calculations, avoids redundant calculations, and shortens the computation time.

[0181] The calculation of the total effective transport rate of all grids in the engine cylinder is consistent with the aforementioned method and steps, and will not be repeated here.

[0182] In an alternative implementation, after S2, the method further includes:

[0183] The effective transport rate coefficient of fuel in the target grid is calculated based on the physical parameters of fuel in the target grid and the spatial coordinate information of the target grid.

[0184] Based on the internal volume of the engine cylinder and the effective transport rate coefficient corresponding to the target grid, calculate the volume average value of the effective fuel transport rate coefficient in the entire engine cylinder;

[0185] Based on the volume average value, the total effective transport rate of all grids within the engine cylinder is calculated.

[0186] It should be noted that the effective transport rate coefficient is calculated in the same way as described above, and will not be repeated here.

[0187] In some alternative implementations, the calculation of the total effective transport rate of all grids within the engine cylinder includes:

[0188] ;

[0189] ;

[0190] ;

[0191] ;

[0192] ;

[0193] in, This represents the volume average of the effective fuel transport rate coefficient throughout the entire engine cylinder. This refers to the internal volume of the engine cylinder.

[0194] The physical meanings of the other parameters are consistent with those described above and will not be repeated here.

[0195] For example, step a: use CFD simulation to calculate the physical parameters inside the engine cylinder of the target model. It is preferable to use CONVERGE 3.0 or higher software to build a CFD simulation model that includes turbulence, spray and combustion models and calibrate the model based on the measured experimental data.

[0196] Step b: Using the CFD model established in step a, calculate the physical fields within the engine cylinder, including density, velocity, fuel mass fraction, turbulent kinetic energy, turbulent kinetic energy dissipation rate, and mesh volume, and output the spatial coordinate information of each mesh. After the CFD simulation calculation is completed, CONVERGE 3.0 or a later version of the software will output an HDF5 data file containing the above information.

[0197] Step c: Import the HDF5 data file into the CFD post-processing software TECPLOT.

[0198] Step d: In TECPLOT, edit the user-defined formula (Specify Equation) to calculate the effective diffusion transport coefficient. Effective convective transport coefficient Effective transport coefficient and the corresponding effective transport rate , , .

[0199] ;

[0200] ;

[0201] ;

[0202] ;

[0203] ;

[0204] ;

[0205] Step e: Use TECPLOT's Slices function to view the cloud map of the calculation results related to the effective transport rate, such as... Figure 4 As shown.

[0206] Step f: Edit the user-defined formula (Specify Equation) in TECPLOT. The absolute value is obtained. .

[0207] Step g: Use the volume average calculation function of the variable in TECPLOT, Analyze>Average, and select the variable as... ,calculate average volume over the entire spatial range Then, compared with the current cylinder volume. Multiplying these together, we obtain the total effective transport rate R of the entire field. The results are shown in [link to results]. Figure 5 As shown.

[0208] ;

[0209] ;

[0210] It should be noted that the above technical approach uses mature post-processing software. In addition, effective transport rate parameters can be calculated by self-programming. The implementation method includes writing post-processing programs using programming languages ​​such as MATLAB or Python.

[0211] In summary, this invention, based on the fundamental principles of mass transfer, quantifies the contributions of diffusion and convection to oil-gas mixing. It also considers the spatial information of the oil-gas mixing rate, as well as the influence of turbulent fields, concentration fields, density fields, velocity fields, and the synergistic effects between these fields on oil-gas mixing. This precise quantification of the oil-gas mixing rate not only helps to deepen the understanding of fuel atomization, evaporation, and mixing mechanisms, but also provides important data support for combustion chamber optimization design, fuel injection strategy optimization, and emission control.

[0212] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A quantitative calculation method for engine oil-air mixing process based on vector cooperation, characterized in that, The method includes: S1. Establish an engine model divided by multiple grids; the engine model forms a physical field; the physical field includes: turbulence field, concentration field, density field, and velocity field; S2. Obtain the volume and spatial coordinate information of each grid in the engine model, as well as the physical parameters of the fuel in each grid; the physical parameters include density, velocity, fuel mass fraction, turbulent kinetic energy, and turbulent kinetic energy dissipation rate; S3. Calculate the effective transport rate of fuel in the target grid based on the physical parameters of the fuel in the target grid, the volume of each grid, and the spatial coordinate information; the target grid can be any one of multiple grids. S4. Calculate the total effective transport rate of fuel in all grids within the engine cylinder based on the effective transport rate of fuel in each grid. S3 includes: S31. Calculate the turbulent diffusion coefficient corresponding to the target grid based on the turbulent kinetic energy and turbulent kinetic energy dissipation rate of the fuel in the target grid. S32. Based on the turbulent diffusion coefficient and volume of the target grid, and the fuel mass fraction and density of the fuel in the target grid, calculate the effective diffusion and transport rate of the fuel in different directions of the target grid. S33. Calculate the effective convective transport rate of fuel in different directions of the target grid based on the density, mass fraction and velocity of the fuel in the target grid. S34. The sum of the effective diffusion transport rates of fuel in different directions of the target grid and the sum of the effective convective transport rates of fuel in different directions of the target grid are superimposed to obtain the effective transport rate of fuel in the target grid. S32 includes: ； in, This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid x Effective diffusion transport rate in the direction of diffusion; S33 includes: ； in, This represents the density of fuel in the target grid. Let the fuel velocity be the velocity within the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh. For fuel in the target grid Effective convective transport rate in the direction.

2. The method according to claim 1, characterized in that, The engine model is a CFD simulation model that includes a turbulence model, a spray model, a combustion model, and an in-cylinder geometry model.

3. The method according to claim 2, characterized in that, S34 includes: S341, Based on fuel level in the target grid Effective diffusion transport rate in the direction Fuel in the target grid Effective diffusion transport rate in the direction Fuel in the target grid Effective diffusion transport rate in the direction Calculate fuel in the target grid , , The sum of effective diffusion transport rates in each direction : ； in, , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid Effective diffusion transport rate in the direction of diffusion. For fuel in the target grid , , The sum of the effective diffusion transport rates in each direction; This represents the density of fuel in the target grid. The turbulent diffusion coefficient corresponding to the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh; S342, Based on fuel level in the target grid Effective convective transport rate in the direction Fuel in the target grid Effective convective transport rate in the direction Fuel in the target grid Effective convective transport rate in the direction Calculate fuel in the target grid , , The sum of effective convective transport rates in each direction : ； in, , The target mesh is located at , , Unit vector in direction For fuel in the target grid Effective convective transport rate in the direction, For fuel in the target grid Effective convective transport rate in the direction, For fuel in the target grid Effective convective transport rate in the direction, For fuel in the target grid , , The sum of effective convective transport rates in each direction. For fuel in the target grid velocity in the direction, For fuel in the target grid velocity in the direction, For fuel in the target grid velocity in the direction, This represents the density of fuel in the target grid. This represents the fuel mass fraction corresponding to the fuel in the target grid. The volume of the target mesh; S343, Based on fuel level in the target grid , , The sum of effective diffusion transport rates in each direction Fuel in the target grid , , The sum of effective convective transport rates in each direction Calculate the effective transport rate of fuel in the target grid. : ； in, This represents the effective transport rate of fuel in the target grid.

4. The method according to claim 3, characterized in that, S4 includes: ； in, For the first cylinder of the engine The effective transport rate of each grid This represents the total number of grids in all engine cylinders.

5. The method according to claim 1, characterized in that, Following S2, the method further includes: The effective transport rate coefficient of fuel in the target grid is calculated based on the physical parameters of fuel in the target grid and the spatial coordinate information of the target grid. The effective transport rate of fuel in the target grid is calculated based on the effective transport rate coefficient of fuel in the target grid and the volume corresponding to the target grid. The target grid can be any one of multiple grids. The total effective transport rate of fuel in all grids within the engine cylinder is calculated based on the effective transport rate of fuel in each grid.

6. The method according to claim 1, characterized in that, Following S2, the method further includes: The effective transport rate coefficient of fuel in the target grid is calculated based on the physical parameters of fuel in the target grid and the spatial coordinate information of the target grid. Based on the internal volume of the engine cylinder and the effective transport rate coefficient corresponding to the target grid, calculate the volume average value of the effective fuel transport rate coefficient in the entire engine cylinder; Based on the volume average value, the total effective transport rate of all grids within the engine cylinder is calculated.

7. The method according to claim 6, characterized in that, The calculation process for the total effective transport rate of all grids within the engine cylinder includes: ； ； ； ； ； in, This represents the volume average of the effective fuel transport rate coefficient throughout the entire engine cylinder. This refers to the internal volume of the engine cylinder.

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