Method and apparatus for determining flow characteristics of an engine intake passage

Abstract

The application provides an engine intake passage flow characteristic determination method and device, and relates to the technical field of engines.The method comprises the following steps: obtaining a plurality of different intake valve lifts according to an intake valve lift curve of an engine; determining flow characteristic indexes of the engine intake passages corresponding to the plurality of different intake valve lifts based on a pre-constructed three-dimensional model of the engine intake passage and / or a preset boundary condition; and obtaining an average flow characteristic index according to the flow characteristic indexes of the engine intake passages corresponding to the plurality of different intake valve lifts. The flow characteristic of the intake passage can be more accurately reflected, which is beneficial to subsequent targeted optimization of the intake passage, and can reduce the development cycle, cost and risk of the intake passage.

Description

Technical Field

[0001] This application relates to the field of engine technology, specifically to a method and apparatus for determining the flow characteristics of an engine intake duct. Background Technology

[0002] For gasoline engines, the intake manifold is a crucial component of the intake system. Connecting the intake manifold and combustion chamber, it serves as the inlet and passage for fresh air, significantly influencing the air-fuel mixture. Therefore, the structure of the intake manifold and the matching of the intake manifold, valves, and combustion chamber are key factors determining the quality of mixture formation and combustion. To achieve a good mixture quality and fast combustion speed, smooth airflow is essential, minimizing flow losses and providing a uniform gas flow field. The movement of fresh charge requires suitable microscopic and macroscopic structures, which collectively affect engine power, fuel economy, emissions, and combustion noise. Therefore, the design of the intake manifold is extremely important.

[0003] During the design and development phase, the intake flow stability test is conducted using an air intake test bench to obtain the flow performance of the intake. This process is lengthy and requires testing resources and costs. Summary of the Invention

[0004] The purpose of this application is to provide a method and apparatus for determining the flow characteristics of an engine intake duct, which can more accurately reflect the flow characteristics of the intake duct, facilitate subsequent targeted optimization of the intake duct, and reduce the development cycle, cost and risk of the intake duct.

[0005] To achieve the above objectives, in a first aspect, this application provides a method for determining the flow characteristics of an engine intake manifold, comprising:

[0006] Multiple different intake valve lifts are obtained based on the engine's intake valve lift curve;

[0007] Based on a pre-built three-dimensional model of the engine intake duct and / or preset boundary conditions, the flow characteristic indicators of the engine intake duct corresponding to multiple different intake valve lifts are determined.

[0008] The average flow characteristic index is derived from the flow characteristic index of the engine intake manifold corresponding to multiple different intake valve lifts.

[0009] In some embodiments of this application, based on the foregoing scheme, multiple different intake valve lifts are obtained according to the engine's intake valve lift curve, including:

[0010] Based on the engine's performance development goals, the intake valve lift curve is determined, and multiple different intake valve lifts are selected based on the intake valve lift curve.

[0011] In some embodiments of this application, based on the aforementioned scheme, multiple different intake valve lifts are selected based on the intake valve lift curve, including: obtaining the maximum lift based on the intake valve lift curve, selecting the minimum lift according to actual needs, and selecting points in the form of an arithmetic sequence, thereby selecting multiple different intake valve lifts.

[0012] In some embodiments of this application, based on the aforementioned scheme, the flow characteristic indicators include the flow coefficient and the tumble ratio, and the average flow characteristic indicators include the average flow coefficient and the average tumble ratio.

[0013] In some embodiments of this application, based on the foregoing scheme, and based on a pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions, flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts are determined, including:

[0014] Based on the three-dimensional model of the engine intake duct and the preset boundary conditions, the flow coefficients of the engine intake duct corresponding to multiple different intake valve lifts are determined by using the first preset correlation relationship.

[0015] The first pre-defined association relationship is:

[0016]

[0017] in,

[0018]

[0019]

[0020]

[0021] Δp=p u -p m

[0022]

[0023] In the formula, FC is the flow coefficient of the engine intake manifold at each intake valve lift, and A is the flow coefficient of the intake manifold. eff For the effective flow area of ​​the intake duct, A piston Where D is the piston top surface area, M is the cylinder diameter, and c is the actual gas flow rate. th ρ is the theoretical intake velocity at the intake valve throat. th Here, k is the theoretical density at the intake valve throat, k is the adiabatic index, R is the ideal gas constant, and p is the theoretical density at the intake valve throat. u Due to environmental pressures, T u For ambient temperature, p m Pressure on the export end;

[0024] The preset boundary conditions include cylinder diameter D, adiabatic index k, ideal gas constant R, and ambient pressure p. u Ambient temperature T u .

[0025] In some embodiments of this application, based on the foregoing scheme, and based on a pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions, flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts are determined, including:

[0026] A plane perpendicular to the cylinder axis is selected as the measurement plane. Based on the three-dimensional model of the engine intake manifold and the second preset correlation, the tumble ratio of the engine intake manifold corresponding to multiple different intake valve lifts is determined.

[0027] The second pre-defined association relationship is:

[0028]

[0029] in,

[0030]

[0031]

[0032]

[0033]

[0034]

[0035] In the formula, TR is the tumble ratio of the engine intake manifold at each intake valve lift, and ω FK To measure the rotational angular velocity of airflow on a plane, ω mot Let ω be the rotational angular velocity of the engine, and the measurement plane has n elements. i To measure the rotational angular velocity of the i-th element on the plane, a i To measure the area of ​​the i-th cell on the plane, r i To measure the radius of rotation of the i-th element relative to the rotation axis on the plane, V i，rel To measure the relative axial velocity of the i-th element on the plane, V i，ax To measure the axial velocity of the i-th element on the plane, To measure the average axial velocity of airflow on a plane, V p S is the average piston speed, S is the cylinder stroke, and N is the engine speed.

[0036] In some embodiments of this application, based on the aforementioned scheme, an average flow characteristic index is derived from the flow characteristic indexes of the engine intake manifold corresponding to multiple different intake valve lifts, including:

[0037] The average flow coefficient is obtained by weighted averaging the flow coefficients of the engine intake manifolds corresponding to multiple different intake valve lifts, and the average tumble ratio is obtained by weighted averaging the tumble ratios of the engine intake manifolds corresponding to multiple different intake valve lifts.

[0038] In some embodiments of this application, based on the foregoing scheme, after the step of deriving the average flow characteristic index according to the flow characteristic indexes of the engine intake passages corresponding to multiple different intake valve lifts, the method further includes:

[0039] The engine intake manifold is optimized based on the relationship between engine type and average flow coefficient and / or average tumble ratio.

[0040] In some embodiments of this application, based on the foregoing scheme, the engine intake manifold is optimized according to the relationship between the engine type and the average flow coefficient and / or average tumble ratio, including:

[0041] When the engine is a naturally aspirated gasoline engine, if the average flow coefficient is smaller compared to a standard model, then increase θ. If the angle and average flow coefficient are too large, then decrease θ. angle; θ is the angle between the tangent at the intersection of the upper side of the intake duct and the throat and the normal to the center line of the intake duct; θ is the angle between the tangent at the intersection of the lower side of the intake duct and the throat and the normal to the center line of the intake duct.

[0042] When the engine is a turbocharged gasoline engine, if the average tumble ratio is smaller compared to a standard engine, then reduce θ. If the average tumble ratio is too large, then increase θ. angle.

[0043] Secondly, this application provides an engine intake duct flow characteristic determination device, comprising:

[0044] The acquisition module is used to acquire multiple different intake valve lifts based on the engine's intake valve lift curve;

[0045] The determination module is used to determine the flow characteristic indicators of the engine intake duct corresponding to multiple different intake valve lifts based on a pre-built three-dimensional model of the engine intake duct and / or preset boundary conditions.

[0046] The processing module is used to derive the average flow characteristic index based on the flow characteristic indexes of the engine intake manifold corresponding to multiple different intake valve lifts.

[0047] This application provides a method and apparatus for determining the flow characteristics of an engine intake duct. The method includes: obtaining multiple different intake valve lifts based on the engine's intake valve lift curve; determining the flow characteristic indices of the engine intake duct corresponding to the multiple different intake valve lifts based on a pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions; and deriving an average flow characteristic index based on the flow characteristic indices of the engine intake duct corresponding to the multiple different intake valve lifts. This method can more accurately reflect the flow characteristics of the intake duct, which is beneficial for subsequent targeted optimization of the intake duct and can reduce the development cycle, cost, and risk of the intake duct. Attached Figure Description

[0048] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0049] Figure 1 This is a flowchart of the method for determining the flow characteristics of the engine intake duct in this application.

[0050] Figure 2 This is a graph showing the intake valve lift of a certain gasoline engine.

[0051] Figure 3 This is a schematic diagram of airflow entering the cylinder;

[0052] Figure 4 This is a schematic diagram of the engine intake manifold.

[0053] Figure 5 The flow coefficient-tumble ratio distribution diagrams are shown for naturally aspirated and turbocharged gasoline engines.

[0054] Figure 6 This is a structural block diagram of the device for determining the flow characteristics of the engine intake duct in this application. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0056] The following detailed description of some embodiments of this application will be provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0057] For gasoline engines, the flow characteristics (flow performance) of the intake manifold generally refer to its flow capacity and ability to generate tumble. To facilitate comparison of the flow performance of intake manifolds of different shapes and sizes, a dimensionless flow coefficient is typically used to evaluate the flow capacity of the intake manifold under different valve lifts, reflecting the degree of matching between the intake manifold and the combustion chamber. A dimensionless tumble ratio is used to evaluate the intake manifold's ability to form in-cylinder tumble under different valve lifts, reflecting the intensity of the tumble flow within the intake manifold.

[0058] Please see Figure 1 This application provides a method for determining the flow characteristics of an engine intake manifold, wherein the executing entity can be a simulation control system, and the method includes the following steps:

[0059] Step S1: Obtain multiple different intake valve lifts based on the engine's intake valve lift curve;

[0060] In some embodiments, multiple different intake valve lifts are obtained based on the engine's intake valve lift curve, including:

[0061] Based on the engine's performance development goals, the intake valve lift curve is determined, and multiple different intake valve lifts are selected based on this curve. Specifically, one-dimensional thermodynamic simulation can be used to determine the intake valve lift curve while meeting the performance development goals.

[0062] In some embodiments, the method for selecting multiple different intake valve lifts based on the intake valve lift curve is as follows:

[0063] First, the maximum lift L is obtained based on the intake valve lift curve. max Since the intake manifold flow capacity is weak when the intake valve lift is very small in actual situations, it is generally not analyzed; that is, the minimum lift L is selected based on actual needs. min The points are selected using an arithmetic sequence to determine multiple different intake valve lifts. That is, the intake valve lift L corresponding to the x-th point is... x The expression is:

[0064] L x =L min +(x_1)·Δ

[0065] Where Δ is the common difference of the arithmetic sequence; x is the number of points selected, which is a positive integer.

[0066] Generally, if the selected intake valve lifts are all integers, then the final selection of multiple different intake valve lifts can be expressed as: [L min], L x , ..., [L max [] represents the Gaussian symbol, which indicates the floor function.

[0067] like Figure 2 The image shows the intake valve lift curve for a certain gasoline engine. The maximum intake valve lift is 8.7 mm. In cases with very small intake valve lifts (e.g., 1 mm), due to weak intake manifold flow, no analysis is performed. L min With a valve lift of 2mm and Δ set to 1mm, the selected valve lifts according to the above expression are 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, and 8mm.

[0068] Step S2: Based on the pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions, determine the flow characteristic indicators of the engine intake duct corresponding to multiple different intake valve lifts.

[0069] Specifically, the method for constructing a three-dimensional model of an engine intake duct may include: obtaining the geometric parameters of the engine, and constructing a three-dimensional model of the engine intake duct based on experimental methods and the geometric parameters of the engine.

[0070] Step S3: Obtain the average flow characteristic index based on the flow characteristic index of the engine intake passage corresponding to multiple different intake valve lifts.

[0071] Specifically, flow characteristic indicators may include flow coefficient and tumble ratio, and average flow characteristic indicators may include average flow coefficient and average tumble ratio.

[0072] like Figure 3 The diagram illustrates the airflow into the cylinder. Due to the throttling effect of the intake valve, the actual flow rate of the gas entering the cylinder is smaller than if there were no intake valve. The flow coefficient is defined as the ratio of the effective flow area through the intake manifold to the piston top surface area, reflecting the flow capacity of the intake manifold and its matching degree with the combustion chamber. Furthermore, the gas flow state inside the cylinder will differ depending on whether the gas enters from above or below the intake valve. Based on engineering experience, the air-fuel mixture enters the cylinder more from above the valve, creating a rotational motion. When the airflow inside the cylinder rotates around a direction perpendicular to the cylinder centerline, it is called tumble motion. In other words, tumble motion is a large-amplitude airflow rotational motion formed inside the cylinder, with the axis of rotation perpendicular to the cylinder centerline. Figure 3 The rotational motion indicated by the middle arrow can enhance airflow, increase the torque of the mixture, improve the tumble intensity of the mixture, and ensure the stability and uniformity of combustion.

[0073] In some embodiments, based on a pre-built three-dimensional model of the engine intake duct and / or preset boundary conditions, flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts are determined, including:

[0074] Based on the three-dimensional model of the engine intake duct and the preset boundary conditions, the flow coefficients of the engine intake duct corresponding to multiple different intake valve lifts are determined by using the first preset correlation relationship.

[0075] The first pre-defined association relationship is:

[0076]

[0077] in,

[0078]

[0079]

[0080]

[0081] Δp=p u -p m

[0082]

[0083] In the formula, FC is the flow coefficient of the engine intake manifold at each intake valve lift, and A is the flow coefficient of the intake manifold. eff For the effective flow area of ​​the intake duct, A piston Where D is the piston top surface area, M is the cylinder diameter, and c is the actual gas flow rate. th ρ is the theoretical intake velocity at the intake valve throat. th Here, k is the theoretical density at the intake valve throat, k is the adiabatic index, R is the ideal gas constant, and p is the theoretical density at the intake valve throat. u Due to environmental pressures, T u For ambient temperature, p m This is due to pressure at the export end.

[0084] Effective flow area A of the intake duct eff Piston top surface area A piston Actual gas flow rate M, theoretical intake velocity c at the intake valve throat th The theoretical density ρ at the intake valve throat th Pressure p at the outlet m It can be obtained through simulation software based on a 3D model of the engine intake manifold, with preset boundary conditions including cylinder diameter D, adiabatic index k, ideal gas constant R, and ambient pressure p. u Ambient temperature T u .

[0085] The main purpose of setting boundary conditions is to simulate the relevant parameters of the engine under actual operating conditions. By simulating the engine intake more realistically, the relevant parameters can be better determined.

[0086] In some embodiments, based on a pre-built three-dimensional model of the engine intake duct and / or preset boundary conditions, flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts are determined, including:

[0087] A plane perpendicular to the cylinder axis is selected as the measurement plane. Based on the three-dimensional model of the engine intake manifold and the second preset correlation, the tumble ratio of the engine intake manifold corresponding to multiple different intake valve lifts is determined.

[0088] Assuming the air-fuel mixture enters from above the valve, the measuring plane can be a cross-section that is half the cylinder diameter D at a distance from the end of the cylinder closest to the intake valve.

[0089] The second pre-defined association relationship is:

[0090]

[0091] in,

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] In the formula, TR is the tumble ratio of the engine intake manifold at each intake valve lift, and ω FK To measure the rotational angular velocity of airflow on a plane, ω mot Let ω be the rotational angular velocity of the engine, and the measurement plane has n elements. i To measure the rotational angular velocity of the i-th element on the plane, a i To measure the area of ​​the i-th cell on the plane, r i To measure the radius of rotation of the i-th element relative to the rotation axis on the plane, V i，rel To measure the relative axial velocity of the i-th element on the plane, V i，ax To measure the axial velocity of the i-th element on the plane, To measure the average axial velocity of airflow on a plane, V p Here, S represents the average piston speed, S represents the cylinder stroke, and N represents the engine speed. All of these parameters can be obtained using simulation software based on a 3D model of the engine intake manifold.

[0098] In some embodiments, an average flow characteristic index is derived based on the flow characteristic indices of the engine intake manifold corresponding to multiple different intake valve lifts, including:

[0099] The average flow coefficient is obtained by weighted averaging the flow coefficients of the engine intake manifolds corresponding to multiple different intake valve lifts, and the average tumble ratio is obtained by weighted averaging the tumble ratios of the engine intake manifolds corresponding to multiple different intake valve lifts.

[0100] 1. Obtain the average flow coefficient using the weighted average method.

[0101]

[0102] in,

[0103] In the formula, FC mean FC is the average flow coefficient. x The intake valve lift is L x The flow coefficient at that time.

[0104] 2. Obtain the average tumble ratio using the weighted average method.

[0105]

[0106] In the formula, TR mean TR is the average tumble ratio. x The intake valve lift is L x The tumble ratio at that time.

[0107] In some embodiments, after obtaining the average flow characteristic index based on the flow characteristic indexes of the engine intake passage corresponding to multiple different intake valve lifts, the engine intake passage flow characteristic determination method of this application further includes: optimizing the engine intake passage based on the relationship between the engine type and the average flow coefficient and / or average tumble ratio.

[0108] like Figure 4 The diagram shows the structure of the engine intake duct. The intake duct 60 has an intake duct centerline 50 and an intake duct throat 40. The angle between the tangent 10 at the intersection of the upper side of the intake duct and the throat and the normal 20 of the intake duct centerline is defined as... The angle between the tangent 30 at the intersection of the lower side of the intake duct and the throat and the normal 20 of the intake duct centerline is θ. If θ is reduced... Increasing the angle of θ lowers the airway surface, making the intake passage more "smooth," thus increasing the tumble flow intensity but decreasing the flow capacity and flow coefficient; conversely, increasing θ... The angle raises the curved surface of the intake duct, making the intake duct "steep," thus reducing the tumble intensity but increasing the flow capacity and the flow coefficient.

[0109] Generally, different types of gasoline engines have different requirements for the level of in-cylinder tumble motion generated by the intake manifold, therefore the criteria for judging the rationality of the intake manifold design also differ. The following explanation uses naturally aspirated and turbocharged gasoline engines as examples. Naturally aspirated gasoline engines require enhanced flow capacity and a higher flow coefficient, while tumble intensity can be reduced; therefore, the optimization direction is to increase θ. The angle is universally applicable. However, turbocharged gasoline engines, due to their higher intake pressure, are less affected by the intake passage flow capacity, meaning they don't require high flow capacity. Instead, they demand high fuel-air mixing efficiency and combustion speed, thus requiring a higher tumble ratio to improve tumble intensity. Therefore, the optimization direction is to reduce θ. Angle, and universally applicable.

[0110] like Figure 5 The figure shows the flow coefficient-tumble ratio distribution for naturally aspirated and turbocharged gasoline engines. Figure 5 The oval box in the upper left corner shows the data set for the flow coefficient and tumble ratio of the standard (Benchmark) model of the naturally aspirated engine, while the oval box in the lower right corner shows the data set for the flow coefficient and tumble ratio of the turbocharged engine.

[0111] Based on this, the engine intake manifold is optimized according to the relationship between engine type and average flow coefficient and / or average tumble ratio, including:

[0112] When the engine is a naturally aspirated gasoline engine, the main consideration is the intake manifold flow capacity. If the average flow coefficient is smaller compared to a standard engine, then increase θ. If the angle and average flow coefficient are too large, then decrease θ. Angle; of course, θ, The magnitude of the angle increase or decrease depends on the actual situation. It must ensure that the flow coefficient requirements of the standard model are met, and that the average tumble ratio is comparable to the standard model, i.e., θ. While increasing or decreasing the angle, the average tumble ratio must not deviate from the standard model's requirement for the tumble ratio.

[0113] When the engine is a turbocharged gasoline engine, the main consideration is the intake manifold tumble intensity. If the average tumble ratio is smaller compared to a standard engine, then reduce θ. If the average tumble ratio is too large, then increase θ. Angle. Of course, θ, The magnitude of the angle increase or decrease depends on the actual situation. It must ensure that the tumble ratio requirements of the standard model are met, and that the average flow coefficient is comparable to that of the standard model, i.e., θ. While increasing or decreasing the angle, the average flow coefficient must not deviate from the standard model's requirements for the flow coefficient.

[0114] Based on the same inventive concept, such as Figure 6 As shown, this application also provides an engine intake duct flow characteristic determination device, comprising:

[0115] Module 1 is used to obtain multiple different intake valve lifts based on the engine's intake valve lift curve;

[0116] Module 2 is used to determine the flow characteristic indicators of the engine intake duct corresponding to multiple different intake valve lifts based on a pre-built three-dimensional model of the engine intake duct and / or preset boundary conditions.

[0117] Processing module 3 is used to derive the average flow characteristic index based on the flow characteristic index of the engine intake passage corresponding to multiple different intake valve lifts.

[0118] In some embodiments, the engine intake duct flow characteristic determination device further includes an optimization module for optimizing the engine intake duct based on the relationship between the engine type and the average flow coefficient and / or average tumble ratio.

[0119] In summary, this application provides a method and apparatus for determining the flow characteristics of an engine intake duct. During the design and development phase, the flow coefficient and tumble ratio reflecting the flow characteristics of the intake duct under different lifts are predicted using a pre-constructed three-dimensional engine model. The average flow coefficient and average tumble ratio are obtained. For different types of engines (e.g., naturally aspirated gasoline engines and turbocharged gasoline engines) with different requirements for the intake duct, suitable optimization directions are proposed to minimize the flow loss of the intake duct, provide the most uniform gas flow field, obtain good air-fuel mixture quality and faster combustion speed, shorten the development cycle of the intake duct, and reduce development costs and risks.

[0120] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that this application is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for determining the flow characteristics of an engine intake duct, characterized in that, include: Multiple different intake valve lifts are obtained based on the engine's intake valve lift curve; Based on a pre-constructed 3D model of the engine intake duct and / or preset boundary conditions, flow characteristic indices for the engine intake duct corresponding to multiple different intake valve lifts are determined. These flow characteristic indices include flow coefficient and tumble ratio. The determination of the tumble ratio includes: selecting a plane perpendicular to the cylinder axis as the measurement plane; obtaining the axial velocity of each grid cell within the measurement plane, and subtracting the overall average axial velocity of the airflow on the measurement plane to obtain the relative axial velocity of each cell; obtaining the rotational angular velocity of each cell based on the relative axial velocity and the cell's rotation radius; weighting the rotational angular velocities of each cell using the product of the cell's area and the square of its rotation radius as the weight to obtain the rotational angular velocity of the airflow on the measurement plane; and finally, comparing the rotational angular velocity of the airflow on the measurement plane with the engine's equivalent rotational angular velocity calculated based on the piston's average velocity to obtain the tumble ratio for the corresponding intake valve lift. The average flow characteristic index is derived from the flow characteristic index of the engine intake manifold corresponding to multiple different intake valve lifts. The average flow characteristic index includes the average flow coefficient and the average tumble ratio. The engine intake manifold is optimized based on the relationship between the engine type and the average flow coefficient and / or the average tumble ratio; wherein optimizing the engine intake manifold includes: increasing or decreasing... , angle, The angle between the tangent at the intersection of the upper side of the intake duct and the throat and the normal to the centerline of the intake duct. It is the angle between the tangent at the intersection of the lower side of the intake and the throat and the normal to the center line of the intake.

2. The method for determining the flow characteristics of an engine intake duct according to claim 1, characterized in that, The process of obtaining multiple different intake valve lifts based on the engine's intake valve lift curve includes: Based on the engine's performance development goals, the intake valve lift curve is determined, and multiple different intake valve lifts are selected based on the intake valve lift curve.

3. The method for determining the flow characteristics of an engine intake duct according to claim 2, characterized in that, The selection of multiple different intake valve lifts based on the intake valve lift curve includes: obtaining the maximum lift based on the intake valve lift curve, selecting the minimum lift according to actual needs, and selecting points in the form of an arithmetic sequence to select multiple different intake valve lifts.

4. The method for determining the flow characteristics of an engine intake duct according to claim 1, characterized in that, The process, based on a pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions, determines flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts, including: Based on the three-dimensional model of the engine intake duct and the preset boundary conditions, the flow coefficients of the engine intake duct corresponding to multiple different intake valve lifts are determined using the first preset correlation relationship. The first preset association relationship is: in, In the formula, FC is the flow coefficient of the engine intake manifold at each intake valve lift. The effective flow area of ​​the air intake duct, The area of ​​the piston top surface. The cylinder diameter, This represents the actual gas flow rate. This is the theoretical intake velocity at the intake valve throat. This is the theoretical density at the intake valve throat. The adiabatic index, Let be the ideal gas constant. Due to environmental pressures, For ambient temperature, Pressure on the export end; The preset boundary conditions include the cylinder diameter. adiabatic index Ideal gas constant Environmental pressure Ambient temperature .

5. The method for determining the flow characteristics of an engine intake duct according to claim 1, characterized in that, The process, based on a pre-constructed three-dimensional model of the engine intake duct and / or preset boundary conditions, determines flow characteristic indices of the engine intake duct corresponding to multiple different intake valve lifts, including: Based on the three-dimensional model of the engine intake duct and a second preset correlation, the tumble ratio of the engine intake duct corresponding to multiple different intake valve lifts is determined; the second preset correlation is: in, In the formula, TR is the tumble ratio of the engine intake manifold at each intake valve lift. To measure the rotational angular velocity of airflow on a plane, The rotational angular velocity of the engine is measured on the plane with... Units, To measure the first on the plane The rotational angular velocity of each unit, To measure the first on the plane The area of ​​each unit To measure the first on the plane The radius of rotation of each unit relative to the rotation axis. To measure the first on the plane The relative axial velocity of each unit To measure the first on the plane The axial velocity of each unit To measure the average axial velocity of airflow on a plane, The average piston speed, For cylinder stroke, This refers to the engine speed.

6. The method for determining the flow characteristics of an engine intake duct according to claim 1, characterized in that, The average flow characteristic index is derived based on the flow characteristic indices of the engine intake manifold corresponding to multiple different intake valve lifts, including: The average flow coefficient is obtained by weighted averaging the flow coefficients of the engine intake manifolds corresponding to multiple different intake valve lifts, and the average tumble ratio is obtained by weighted averaging the tumble ratios of the engine intake manifolds corresponding to multiple different intake valve lifts.

7. The method for determining the flow characteristics of an engine intake duct according to claim 1, characterized in that, The optimization of the engine intake manifold based on the relationship between engine type and average flow coefficient and / or average tumble ratio includes: When the engine is a naturally aspirated gasoline engine, if the average flow coefficient is smaller compared to a standard model, then the increase is necessary. , If the angle and average flow coefficient are too large, then decrease... , angle; When the engine is a turbocharged gasoline engine, if the average tumble ratio is smaller compared to a standard engine, then reduce... , Angle, if the average tumble ratio is too large, then increase , angle.

8. A device for determining the flow characteristics of an engine intake duct, characterized in that, include: The acquisition module is used to acquire multiple different intake valve lifts based on the engine's intake valve lift curve; The determination module is used to determine the flow characteristic indicators of the engine intake manifold corresponding to multiple different intake valve lifts, based on a pre-constructed three-dimensional model of the engine intake manifold and / or preset boundary conditions. The flow characteristic indicators include the flow coefficient and the tumble ratio. The determination of the tumble ratio includes: selecting a plane perpendicular to the cylinder axis as the measurement plane; obtaining the axial velocity of each grid cell in the measurement plane, and subtracting the overall average axial velocity of the airflow on the measurement plane to obtain the relative axial velocity of each cell; obtaining the rotational angular velocity of each cell based on the relative axial velocity and the cell's rotation radius; weighting the rotational angular velocities of each cell by the product of the cell's area and the square of its rotation radius to obtain the rotational angular velocity of the airflow on the measurement plane; and comparing the rotational angular velocity of the airflow on the measurement plane with the equivalent rotational angular velocity of the engine calculated based on the average piston velocity to finally obtain the tumble ratio under the corresponding intake valve lift. The processing module is used to derive an average flow characteristic index based on the flow characteristic indexes of the engine intake manifold corresponding to multiple different intake valve lifts. The average flow characteristic indexes include the average flow coefficient and the average tumble ratio. The engine intake manifold is optimized based on the relationship between the engine type and the average flow coefficient and / or the average tumble ratio; wherein optimizing the engine intake manifold includes: increasing or decreasing... , angle, The angle between the tangent at the intersection of the upper side of the intake duct and the throat and the normal to the centerline of the intake duct. It is the angle between the tangent at the intersection of the lower side of the intake and the throat and the normal to the center line of the intake.

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