A method for establishing a diesel engine cylinder combustion analysis model

Abstract

The present invention relates to the field of engine technology, and specifically to a method for establishing a diesel engine in-cylinder combustion analysis model. The top clearance structure of a closed combustion chamber is simplified into a top sloping roof structure with the same volume; the combustion chamber volume formed by the top of the piston and the bottom of the cylinder head when the engine piston is at the bottom dead center is used as the stroke volume; the annular gap structure formed by the piston, piston ring, and cylinder liner is extracted from the lower part of the stroke volume to form a piston ring gap, and the outer diameter of the piston ring gap is equal to the outer diameter of the stroke volume; the piston bowl shape is extracted from the lower part of the stroke volume, and the center line of the piston bowl shape coincides with the stroke volume; according to the piston axis, the top sloping roof structure, stroke volume, piston ring gap, and piston bowl shape are assembled to form a combustion analysis model. The combustion chamber model is constructed using the top sloping roof structure, stroke volume, piston ring gap, and piston bowl-shaped components, which is suitable for rapid in-cylinder combustion simulation analysis while ensuring the accuracy of the prediction results.

Description

Technical Field

[0001] The present invention relates to the technical field of engines, and in particular to a method for establishing a diesel engine cylinder combustion analysis model. Background Art

[0002] Currently, diesel engines are facing considerations such as upgraded emission regulations, increased power and torque, and upgraded fuel economy regulations, and need to continuously optimize in-cylinder combustion efficiency.

[0003] The in-cylinder combustion simulation analysis method can be used to quickly select the combination of injectors and piston bowl shapes. At the same time, the impact of changes in boundary conditions such as compression ratio, intake conditions, and swirl ratio on in-cylinder combustion efficiency, emissions, and economy can be considered.

[0004] Most of the combustion analysis model building methods currently used are holistic model building methods. Some structures of the combustion chamber model are small and difficult to perform structured meshing, so they need to be simplified or ignored. Using the holistic model for calculation will result in long calculation times, and ignored structures will affect the calculation results. Therefore, it is necessary to establish a combustion chamber model that is suitable for fast in-cylinder combustion simulation analysis and does not affect the performance component combination evaluation. Summary of the Invention

[0005] The purpose of the present invention is to address the defects of the existing technology and provide a method for establishing a diesel engine cylinder combustion analysis model, which is suitable for performing rapid cylinder combustion simulation analysis and does not affect the performance component combination evaluation.

[0006] The technical solution of the present invention is: simplifying the clearance structure at the top of the closed combustion chamber into a top inclined roof structure with the same volume;

[0007] The volume of the combustion chamber formed by the top of the piston and the bottom of the cylinder head when the engine piston is at the bottom dead center is taken as the stroke volume;

[0008] Extracting the annular gap structure formed by the piston, piston ring and cylinder liner at the lower part of the stroke volume to form a piston ring gap, wherein the outer diameter of the piston ring gap is equal to the outer diameter of the stroke volume;

[0009] Extracting a piston bowl shape below the stroke volume, wherein the center line of the piston bowl shape coincides with the stroke volume;

[0010] According to the piston axis, the top inclined roof structure, stroke volume, piston ring gap, and piston bowl shape are assembled to form a combustion analysis model.

[0011] More preferably, the top slanted roof structure is located at the upper part of the stroke volume, and the center line of the top slanted roof structure coincides with the stroke volume, the outer edge of the top slanted roof structure is flush with the outer edge of the stroke volume, the top slanted roof structure has an upper surface and a lower surface parallel to each other, the side of the top slanted roof structure facing the center line is an inclined surface for connecting the upper surface and the lower surface, and the distance between the edge of the upper surface and the center line is greater than the distance between the edge of the lower surface and the center line.

[0012] Preferably, simplifying the clearance structure at the top of the closed combustion chamber into a top inclined roof structure with a uniform volume includes:

[0013] Install the engine block, cylinder head, intake / exhaust valves, valve guides, cylinder gaskets, cylinder liners, pistons and injectors according to the actual assembly positions;

[0014] Ensure that the cylinder gasket thickness is at the compressed height, the intake and exhaust valves are closed, and the piston is at the top dead center position of the engine;

[0015] Extract the top structure of the closed combustion chamber formed inside the engine cylinder and calculate the volume V of the top structure of the closed combustion chamber 余隙 ;

[0016] The top structure of the closed combustion chamber is simplified to the volume and V 余隙 Equal top sloping roof structure.

[0017] Preferably, the simplified formula of the top inclined roof structure is as follows:

[0018] L_1=(1 / a*i)*(K_1+K_2+K_3+......K_i);

[0019] L_2=(1 / a*i)*(S_1+S_2+S_3+......S_i);

[0020] K_i=S_i-R_i;

[0021] V=π*H_1*[(D / 2)^2-(L_2*L_2+L_1*L_1+L_1*L_2) / 3];

[0022] V=V 余隙 ;

[0023] Where i is the number of valves, S_i is the radial distance between the centerline of the i-th valve and the centerline of the cylinder, K_i is the radial distance between the inner edge of the i-th valve and the centerline of the cylinder, R_i is the radius of the i-th valve, D is the engine cylinder diameter, H_1 is the height of the top sloping roof structure, a is the volume compensation coefficient, V is the volume of the top sloping roof structure, L_1 is the distance from the edge of the lower surface of the top sloping roof structure to the centerline, and L_2 is the distance from the edge of the upper surface of the top sloping roof structure to the centerline.

[0024] Preferably, the stroke volume is calculated by the formula V 冲 =π*(D / 2)^2*L, where L is the engine stroke and D is the engine cylinder diameter.

[0025] Preferably, the extraction of the piston ring gap includes:

[0026] Install the engine cylinder block, cylinder gasket, cylinder liner, piston and piston ring according to the actual assembly position;

[0027] Ensure that the piston is at the top dead center position of the engine and the first piston ring is in the compressed state after installation;

[0028] Extract the annular gap structure formed by the piston, piston ring and cylinder liner, and calculate its volume V 环隙 ;

[0029] The annular gap structure is simplified into volume and V 环隙 Equal piston ring clearance.

[0030] More preferably, the piston ring gap is located at the lower part of the stroke volume, and the center line of the piston ring gap coincides with the stroke volume, the outer edge of the piston ring gap is flush with the outer edge of the stroke volume, the piston ring gap has an upper surface and a lower surface parallel to each other, the side of the piston ring gap facing the center line is a slope for connecting the upper surface and the lower surface, and the distance between the edge of the upper surface and the center line is less than the distance between the edge of the lower surface and the center line.

[0031] Preferably, the simplified formula of the piston ring gap is as follows:

[0032] V=π*H_2*[(D / 2)^2-[(D / 2-L_4)^2+(D / 2-L_3)^2+(D / 2-L_3)*

[0033] D / 2-L_4)] / 3];

[0034] V=V 环隙 ;

[0035] Among them, H_2 is the height of the piston ring gap, L_3 is the distance from the edge of the upper surface of the piston ring gap to the center line, and L_4 is the distance from the edge of the lower surface of the piston ring gap to the center line.

[0036] Preferably, the piston bowl-shaped extraction includes:

[0037] Based on the actual structure of the engine, for pistons with valve avoidance pits, the valve avoidance pits are removed before extraction;

[0038] For pistons without valve avoidance pits, extract directly.

[0039] More preferably, after completing the assembly of the top sloping top structure, stroke volume, piston ring gap, and piston bowl shape according to the piston axis, the combustion analysis model is also cut to form a fan-shaped structure, and the angle α of the fan-shaped structure is 360° / n, where n is the number of nozzles.

[0040] The beneficial effects of the present invention are as follows: a combustion chamber model is constructed using a top sloping roof structure, stroke volume, piston ring gap, and piston bowl-shaped components, solving the problem of establishing a combustion chamber model suitable for rapid calculation of in-cylinder combustion simulation analysis. This method ensures that the compression ratio of the combustion chamber is consistent with the actual situation, so that the maximum explosion pressure in the cylinder is not affected; ensuring that the bowl shape is consistent with the actual structure can ensure that the oil beam injection and gas flow direction in the analysis are consistent with the actual situation, and ensure that the combustion flame distribution is consistent with the actual situation; the piston ring gap is simplified according to the actual ring gap structure of the engine, without affecting the simulation accuracy of carbon soot and unburned hydrocarbon generation in the piston ring gap; the volume of the cylinder head valve and the valve pit are simplified to an equal volume sloping roof structure, ensuring that the combustion chamber grid is easier to divide without affecting the calculation accuracy, and reducing the influence of the small volume and speeding up the calculation speed. The combustion chamber model adopts a fan-shaped structure, which can reduce the number of grids and reduce the calculation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the structure of the combustion analysis model of the present invention;

[0042] Figure 2 for Figure 1 AA sectional view;

[0043] Figure 3 This is a schematic diagram of the top sloping roof structure of the present invention;

[0044] Figure 4 This is a schematic diagram of the piston ring gap structure of the present invention. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0046] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0047] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0049] Example 1

[0050] Figure 1 Shows the preferred embodiment of this application ( Figure 1 FIG. 1 shows a schematic structural diagram of a diesel engine cylinder combustion analysis model provided in the first embodiment of the present application. For ease of explanation, only the parts related to this embodiment are shown, which are described in detail as follows:

[0051] like Figure 1 As shown, the combustion analysis model structure of this scheme consists of a top inclined top structure 1, a stroke volume 2, a piston ring gap 3, and a piston bowl shape 4.

[0052] like Figure 2 As shown, the combustion chamber model adopts a fan-shaped structure, and the calculation method of the fan-shaped structure is as follows:

[0053] The fan angle of the combustion chamber model is calculated according to the number of holes in the injector. Figure 2 The angle α shown is the sector angle:

[0054] α=360° / n

[0055] Where: n is the number of nozzle holes.

[0056] The construction process of the combustion analysis model of this scheme is as follows:

[0057] Constructing the top sloping roof structure 1: Simplify the clearance structure at the top of the closed combustion chamber into a top sloping roof structure with the same volume;

[0058] Construct stroke volume 2: The volume of the combustion chamber formed by the top of the piston and the bottom of the cylinder head when the engine piston is at bottom dead center is used as the stroke volume;

[0059] Constructing a piston ring gap 3: extracting the ring gap structure formed by the piston, piston ring and cylinder liner at the lower part of the stroke volume to form a piston ring gap, wherein the outer diameter of the piston ring gap is equal to the outer diameter of the stroke volume;

[0060] Constructing the piston bowl shape 4: extracting the piston bowl shape below the stroke volume, wherein the center line of the piston bowl shape coincides with the stroke volume;

[0061] After completing the assembly of the top sloping top structure, stroke volume, piston ring gap, and piston bowl shape according to the piston axis, the combustion analysis model is also cut to form a fan-shaped structure. The angle α of the fan-shaped structure is 360° / n, where n is the number of nozzles.

[0062] More preferably, Figure 3 As shown, the top slanted roof structure is located at the upper part of the stroke volume, and the center line of the top slanted roof structure coincides with the stroke volume, the outer edge of the top slanted roof structure is flush with the outer edge of the stroke volume, and the top slanted roof structure has an upper surface and a lower surface parallel to each other, and the side of the top slanted roof structure facing the center line is an inclined surface for connecting the upper surface and the lower surface, and the distance between the edge of the upper surface and the center line is greater than the distance between the edge of the lower surface and the center line.

[0063] Preferably, simplifying the clearance structure at the top of the closed combustion chamber into a top inclined roof structure with a uniform volume includes:

[0064] Install the engine block, cylinder head, intake / exhaust valves, valve guides, cylinder gaskets, cylinder liners, pistons, fuel injectors and other components according to the actual assembly positions;

[0065] Ensure that the cylinder gasket thickness is at the compressed height, the intake and exhaust valves are closed, and the piston is at the top dead center position of the engine;

[0066] The cre / o tool is used to extract the top structure of the closed combustion chamber formed inside the engine cylinder and calculate the volume V of the top structure of the closed combustion chamber. 余隙 ;

[0067] In order to ensure the volume and V 余隙 On the premise of being equal, the top structure of the closed combustion chamber is simplified into a top sloping roof structure using the following formula.

[0068] The simplified formula for the top sloping roof structure is:

[0069] L_1=(1 / a*i)*(K_1+K_2+K_3+......K_i);

[0070] L_2=(1 / a*i)*(S_1+S_2+S_3+......S_i);

[0071] K_i=S_i-R_i;

[0072] V=π*H_1*[(D / 2)^2-(L_2*L_2+L_1*L_1+L_1*L_2) / 3];

[0073] V=V 余隙 ;

[0074] Where i is the number of valves, S_i is the radial distance between the centerline of the i-th valve and the centerline of the cylinder, K_i is the radial distance between the inner edge of the i-th valve and the centerline of the cylinder, R_i is the radius of the i-th valve, D is the engine cylinder diameter, H_1 is the height of the top sloping roof structure, a is the volume compensation coefficient, V is the volume of the top sloping roof structure, L_1 is the distance from the edge of the lower surface of the top sloping roof structure to the centerline, and L_2 is the distance from the edge of the upper surface of the top sloping roof structure to the centerline.

[0075] In this embodiment, H_1 is 1 to 3 mm, and a is 0.8 to 1.2.

[0076] Preferably, the stroke volume 2 is the volume of the combustion chamber formed by the top of the piston and the bottom of the cylinder head when the engine piston is at the bottom dead center. The stroke volume is calculated by the formula V 冲 =π*(D / 2)^2*L, where L is the engine stroke and D is the engine cylinder diameter.

[0077] Preferably, the piston ring gap is located below the stroke volume, and the centerline of the piston ring gap coincides with the stroke volume. The outer edge of the piston ring gap is flush with the outer edge of the stroke volume. The piston ring gap has a mutually parallel upper surface and lower surface. The side of the piston ring gap facing the centerline is an inclined surface for connecting the upper and lower surfaces. The distance between the edge of the upper surface and the centerline is less than the distance between the edge of the lower surface and the centerline. Extracting the piston ring gap includes:

[0078] Install the engine cylinder block, cylinder gasket, cylinder liner, piston, piston ring and other components according to the actual assembly position;

[0079] Ensure that the piston is at the top dead center position of the engine and the first piston ring is in the compressed state after installation;

[0080] Use the cre / o tool to extract the annular gap structure formed by the piston, piston ring and cylinder liner, and calculate its volume V 环隙 ;

[0081] In order to ensure the volume and V 环隙 Under the premise of being equal, the annular gap structure is simplified to the piston annular gap using the following formula, such as Figure 4 shown.

[0082] Preferably, the simplified formula of the piston ring gap is as follows:

[0083] V=π*H_2*[(D / 2)^2-[(D / 2-L_4)^2+(D / 2-L_3)^2+(D / 2-L_3)*

[0084] D / 2-L_4)] / 3];

[0085] V=V 环隙 ;

[0086] Among them, H_2 is the height of the piston ring gap, L_3 is the distance from the edge of the upper surface of the piston ring gap to the center line, and L_4 is the distance from the edge of the lower surface of the piston ring gap to the center line.

[0087] In this embodiment, H_2 is 2-3 mm, L_3 is 8-10 mm, and L_4 is 4-6 mm.

[0088] Preferably, the piston bowl-shaped extraction includes:

[0089] Based on the actual structure of the engine, for pistons with valve avoidance pits, the valve avoidance pits are removed before extraction;

[0090] For pistons without valve avoidance pits, extract directly.

[0091] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0092] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for establishing a diesel engine in-cylinder combustion analysis model, characterized by: The clearance structure at the top of the closed combustion chamber is simplified to a top inclined roof structure with the same volume; The volume of the combustion chamber formed by the top of the piston and the bottom of the cylinder head when the engine piston is at the bottom dead center is taken as the stroke volume; Extracting the annular gap structure formed by the piston, piston ring and cylinder liner at the lower part of the stroke volume to form a piston ring gap, wherein the outer diameter of the piston ring gap is equal to the outer diameter of the stroke volume; Extracting a piston bowl shape below the stroke volume, wherein the center line of the piston bowl shape coincides with the stroke volume; According to the piston axis, the top inclined roof structure, stroke volume, piston ring gap, and piston bowl shape are assembled to form a combustion analysis model; The top slanted roof structure is located at the upper part of the stroke volume, and the center line of the top slanted roof structure coincides with the stroke volume. The outer edge of the top slanted roof structure is flush with the outer edge of the stroke volume. The top slanted roof structure has an upper surface and a lower surface parallel to each other. The side of the top slanted roof structure facing the center line is an inclined surface for connecting the upper surface and the lower surface. The distance between the edge of the upper surface and the center line is greater than the distance between the edge of the lower surface and the center line.

2. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: Simplifying the top clearance structure of the closed combustion chamber into a top inclined roof structure with uniform volume includes: Install the engine block, cylinder head, intake / exhaust valves, valve guides, cylinder gaskets, cylinder liners, pistons and injectors according to the actual assembly positions; Ensure that the cylinder gasket thickness is at the compressed height, the intake and exhaust valves are closed, and the piston is at the top dead center position of the engine; Extract the top structure of the closed combustion chamber formed inside the engine cylinder and calculate the volume V of the top structure of the closed combustion chamber 余隙 ; The top structure of the closed combustion chamber is simplified to the volume and V 余隙 Equal top sloping roof structure.

3. The method for establishing a diesel engine cylinder combustion analysis model according to claim 2, characterized in that: The simplified formula of the top inclined roof structure is as follows: L_1=(1 / a*i)*(K_1+K_2+K_3+......K_i); L_2=(1 / a*i)*(S_1+S_2+S_3+......S_i); K_i=S_i-R_i; V=π*H_1*[(D / 2)^2-(L_2*L_2+L_1*L_1+L_1*L_2) / 3]; V=V 余隙 ; Where i is the number of valves, S_i is the radial distance between the centerline of the i-th valve and the centerline of the cylinder, K_i is the radial distance between the inner edge of the i-th valve and the centerline of the cylinder, R_i is the radius of the i-th valve, D is the engine cylinder diameter, H_1 is the height of the top sloping roof structure, a is the volume compensation coefficient, V is the volume of the top sloping roof structure, L_1 is the distance from the edge of the lower surface of the top sloping roof structure to the centerline, and L_2 is the distance from the edge of the upper surface of the top sloping roof structure to the centerline.

4. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: The stroke volume is given by the formula V 冲 =π*(D / 2)^2*L, where L is the engine stroke and D is the engine cylinder diameter.

5. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: The extraction of the piston ring gap includes: Install the engine cylinder block, cylinder gasket, cylinder liner, piston and piston ring according to the actual assembly position; Ensure that the piston is at the top dead center position of the engine and the first piston ring is in the compressed state after installation; Extract the annular gap structure formed by the piston, piston ring and cylinder liner, and calculate its volume V 环隙 ; The annular gap structure is simplified into volume and V 环隙 Equal piston ring clearance.

6. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: The piston ring gap is located at the lower part of the stroke volume, and the center line of the piston ring gap coincides with the stroke volume. The outer edge of the piston ring gap is flush with the outer edge of the stroke volume. The piston ring gap has an upper surface and a lower surface parallel to each other. The side of the piston ring gap facing the center line is an inclined surface for connecting the upper surface and the lower surface. The distance between the edge of the upper surface and the center line is less than the distance between the edge of the lower surface and the center line.

7. The method for establishing a diesel engine cylinder combustion analysis model according to claim 5, characterized in that: The simplified formula for the piston ring gap is as follows: V=π*H_2*[(D / 2)^2-[(D / 2-L_4)^2+(D / 2-L_3)^2+(D / 2-L_3)*D / 2-L_4)] / 3]; V=V 环隙 ; Where H_2 is the height of the piston ring gap, L_3 is the distance from the edge of the upper surface of the piston ring gap to the center line, L_4 is the distance from the edge of the lower surface of the piston ring gap to the center line, and D is the engine cylinder diameter.

8. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: The piston bowl extraction includes: Based on the actual structure of the engine, for pistons with valve avoidance pits, the valve avoidance pits are removed before extraction; For pistons without valve avoidance pits, extract directly.

9. The method for establishing a diesel engine cylinder combustion analysis model according to claim 1, characterized in that: After completing the assembly of the top sloping top structure, stroke volume, piston ring gap, and piston bowl shape according to the piston axis, the combustion analysis model is also cut to form a fan-shaped structure. The angle α of the fan-shaped structure is 360° / n, where n is the number of nozzles.

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