A combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in GDI gasoline engines

Abstract

The present invention discloses a combustion chamber zoning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine, belonging to the field of engine technology. According to the combustion chamber structure and the flame spatial development process, a 9-interval division method of the spark plug area, the combustion chamber center area, and the combustion chamber clearance area is adopted in combination with the 4-quadrant spatial coordinate system. The method can accurately determine the specific spatial position of the mixture distribution suitable for combustion in the combustion chamber, further analyze the synergistic relationship between the oil and gas spatial distribution, the flow field in the cylinder, and the combustion process, and provide a reliable means for analyzing the spatial distribution characteristics of oil and gas in a direct injection gasoline engine.

Description

Technical Field

[0001] The present invention belongs to the technical field of engines, and in particular relates to a combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine. Background Art

[0002] Gasoline engines using direct injection technology combined with a multiple injection strategy can achieve stratified combustion under high compression ratio and lean conditions, which helps further improve thermal efficiency. The combustion stability of stratified combustion depends on the distribution of the mixture concentration in the cylinder space. In fact, the oil-gas spatial distribution is actually affected by multiple factors such as the in-cylinder airflow organization, oil-gas mixing time, the direction of the oil beam landing point, the spark plug position, and the flow guidance effect of the combustion chamber wall. Under the condition of relatively low average equivalent weight of the overall in-cylinder mixture, achieving an ideal oil-gas spatial stratified distribution with a slightly richer ignition area near the spark plug, a more uniform area elsewhere, and a smaller stratified concentration gradient requires matching and optimizing key components and parameters of the combustion system, such as the intake duct, injector, and combustion chamber, to ultimately obtain oil-gas spatial distribution characteristics that are conducive to rapid combustion.

[0003] Experimental measurement of the spatial distribution of fuel and gas, which determines combustion characteristics, requires methods such as laser-induced fluorescence (PLIF) on an optical engine test bench. These methods, characterized by limited test conditions, long preparation cycles, and a limited viewing area, make them unsuitable for optimizing combustion systems during engineering development. CFD simulation of gasoline engine in-cylinder processes, including gas exchange, spraying, and combustion, allows for the modification of relevant research parameters without the need for a prototype. After processing the calculated results, qualitative analysis can be performed using three-dimensional results such as mixture equivalence ratio contours to quickly determine the spatial distribution of fuel and gas. This can be combined with two-dimensional data such as in-cylinder average pressure and instantaneous heat release rate to assess the impact of this spatial distribution on combustion performance. Consequently, CFD simulation has become a mainstream tool for guiding the engineering development of direct-injection gasoline engine combustion systems. However, current CFD research on the quantitative analysis of fuel and gas spatial distribution focuses primarily on the in-cylinder average and the ignition region near the spark plug. While this can assess whether the locally rich mixture in the ignition region meets stable ignition conditions, it fails to fully characterize the spatial distribution of fuel throughout the combustion chamber.

[0004] To quantitatively analyze fuel distribution within different combustion chamber regions, some studies, both domestically and internationally, have employed spatially averaged statistics of the mixture concentration and mixture stratification gradients within each region of the CFD results, using a uniform stratification method centered around the spark plug's centerline. This method then characterizes the progressive stratification of the mixture from the spark plug electrode. However, the actual fuel-air mixture is affected by factors such as in-cylinder flow and the combustion chamber walls, resulting in a non-axisymmetric distribution of fuel and air around the spark plug's centerline. The flame core after spark formation also exhibits an eccentric development pattern, influenced by the combined effects of airflow and mixture distribution. The aforementioned spherical or cylindrical zoning methods fail to capture the spatial distribution characteristics of fuel, the influence of airflow and the combined effects of fuel spatial distribution on flame development, and the residual fuel accumulation in the combustion chamber caused by incomplete combustion due to wall quenching and gap effects. Therefore, a new in-cylinder spatial zoning method is needed to analyze the synergistic relationship between fuel and air spatial distribution, in-cylinder flow field, and combustion process. Summary of the Invention

[0005] The purpose of the present invention is to provide a combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine, so as to solve the problem that the existing technology, which considers the quantitative analysis of oil and gas distribution characteristics based on CFD calculation results, adopts a spatial partitioning method mostly limited to a method of uniformly partitioning outwards in a sphere or cylinder with the spark plug position as the center, cannot reflect the uneven spatial distribution characteristics of the fuel in the combustion chamber under the influence of factors such as air flow and the combustion chamber wall, and it is difficult to clarify the relationship between the spatial distribution of the fuel and the spatial propagation characteristics of the flame after the fire core is formed.

[0006] To achieve the above objectives, the present invention provides a combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine, comprising the following steps:

[0007] Step 1: Use CFD software CONVERGE to establish a CFD calculation model for a direct injection gasoline engine, and extract the radius R of the combustion chamber center area based on the geometric characteristic parameters of the model. S , cylinder radius R B , where the radius of the central area of ​​the combustion chamber is determined according to the actual shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. For combustion chambers of other configurations, R S =0.85*R B ; Extract the center coordinates of the lower surface of the fixed boundary cylinder head (x c ,y c , z c ), and move the global coordinate system xyz so that (x c ,y c , z c) is the origin of the coordinate system xyz (0, 0, 0); extract the coordinates of the center position of the spark plug electrode gap in the current coordinate system (x sp ,y sp , z sp );

[0008] Step 2: Based on the characteristic parameters extracted in step 1 and the global coordinate system xyz, considering that the center position of the spark plug may not coincide with the center axis of the cylinder, establish the functions required for spatial partitioning, including a spark plug area extraction function for characterizing ignition stability, a center area extraction function for characterizing the rapid flame development process, and a clearance area extraction function for characterizing the late flame development process;

[0009] Step 3. Import the CONVERGE HDF5 format .out calculation data file containing the flow, spray, and combustion processes into the CFD post-processing software TECPLOT. The grid node coordinates and the calculation variable values ​​at the nodes within each calculation time step are arranged in a certain order. The calculation variables including the mixture equivalence ratio Equiv_Ratio and the calculation area number representing the in-cylinder working area surrounded by the cylinder wall, piston top surface, and cylinder head bottom surface can all be completed in Step 1. The data export settings in the .out file can be completed.

[0010] Step 4: Edit the user-defined formula Specify Equation in TECPLOT to calculate the intermediate variables L1 and L2 of the partition feature distance required by the spatial partition function in step 2, and add them to the grid node data obtained in step 3;

[0011] Step 5: Use the Value Blanking function in TECPLOT to blank the grid nodes at x. i and y i , the combustion chamber calculation area indication number excluding the intake and exhaust ducts, and the characteristic distances L1 and L2 obtained in step 4 are used to perform conditional operations on the spatial partition extraction function to select a grid subset whose node position satisfies the spatial distribution range of a certain partition among the 9 partitions;

[0012] Step 6: Use the Extract Blanked Zones function in TECPLOT to extract the calculated variable data based on the grid subsets that meet the partition space range conditions obtained in step 5;

[0013] Step 7: Perform mass-weighted average processing on the partitioned regional grid data extracted in step 6 to obtain the regional average value of the calculated variables including the mixture equivalence ratio.

[0014] Step 8. Automatically repeat steps 5 to 7 by writing and executing macro commands until the average values ​​of the mixture equivalence ratios of the nine partitioned areas are completely extracted. By comparing the differences in the average values ​​of the mixture equivalence ratios in the nine areas, the spatial distribution of the fuel in the combustion chamber is quantitatively and clearly obtained.

[0015] Preferably, the expression of the spark plug region extraction function used to characterize ignition stability in step 2 is as follows:

[0016] SPARK_R1 2 ≤(x i -x sp ) 2 +(y i -y sp ) 2 +(z i -z sp ) 2

[0017] Where SPARK_R1 is the minimum fire core development radius required for the stable development of the flame formed after the spark is generated. It is generally believed that SPARK_R1 = ROUNDUP(0.05*RB), and ROUNDUP() is an upward rounding function; x i 、y i 、z i is the spatial coordinate of each computational grid node in the local coordinate system.

[0018] Preferably, the expression of the central region extraction function used to characterize the rapid flame development process in step 2 is as follows:

[0019]

[0020] Where CENTER_R2 is the radius R of the center area of ​​the combustion chamber extracted in step 1 S , that is, the radius of the central cylindrical area of ​​the combustion chamber after removing the extrusion gap of the combustion chamber.

[0021] Preferably, the expression of the clearance region extraction function used to characterize the late flame development process in step 2 is as follows:

[0022]

[0023] The cylinder radius R extracted in step 1 B The radius R of the center area of ​​the combustion chamber S The difference is the ring width of the combustion chamber squeeze gap ring column area CLEARANCE_R3, specifically CLEARANCE_R3 = R B -CENTER_R2.

[0024] Preferably, the space is divided into 9 spatial areas, including 1 spark plug area, 4 center areas, and 4 clearance areas.

[0025] Preferably, the expression of one spark plug area is as follows:

[0026] R 2 ≤(x-x1) 2 +(y-y1) 2 +(z-z1) 2

[0027] Where R is set according to the size of the cylinder diameter, specifically R = ROUNDUP(0.05*Bore), ROUNDUP() is the rounding function, Bore is the cylinder diameter, (x1, y1, z1) is the position of the spark plug center, and (x, y, z) are the spatial coordinates of each computational grid node in the current coordinate system.

[0028] Preferably, the four central areas are obtained by dividing the central areas of the four quadrants. The central area located in the first quadrant is central area 1, the central area located in the second quadrant is central area 2, the central area located in the third quadrant is central area 3, and the central area located in the fourth quadrant is central area 4. The specific expression is as follows:

[0029] The spatial function of the center area 1 is:

[0030]

[0031] The spatial function of the center 2 area is

[0032]

[0033] The spatial function of the central 3 zones is:

[0034]

[0035] The spatial function of the central 4 zones is

[0036]

[0037] Where R1 is the radius of the central area, which is determined by the shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. If a flat-top combustion chamber or other irregular combustion chamber is used, R1 = 0.85*(Bore / 2).

[0038] Preferably, the four clearance areas are obtained by dividing the clearance area into four quadrants. The clearance area in the first quadrant is clearance area 1, the clearance area in the second quadrant is clearance area 2, the clearance area in the third quadrant is clearance area 3, and the clearance area in the fourth quadrant is clearance area 4. The specific expression is as follows:

[0039] The spatial function of clearance zone 1 is:

[0040]

[0041] The spatial function of clearance zone 2 is

[0042]

[0043] The spatial function of the clearance zone 3 is

[0044]

[0045] The spatial function of the clearance zone 4 is

[0046]

[0047] Preferably, the specific calculation expressions of the intermediate variables L1 and L2 are as follows:

[0048]

[0049] Where L1 represents the distance between the grid node and the center of the spark plug gap, and L2 represents the distance between the grid node and the center axis of the cylinder.

[0050] Preferably, the regional average The calculation expression is as follows:

[0051]

[0052] in represents a computational variable, ρ i represents density, V i represents the grid volume, and n is the number of grids in the partition.

[0053] Therefore, the present invention adopts the above-mentioned combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine, which has the following beneficial effects:

[0054] (1) The present invention proposes a 9-partitioning method that reflects the characteristics of the combustion chamber structure and the spatial development of the fire core and flame propagation in view of the fact that the fuel may show spatial asymmetry due to factors such as short mixing time, strong air flow movement, and wall diversion during the oil-gas mixing process. The oil-gas mixing quality in the spark plug area, central area, and clearance area corresponds to the characteristics of the combustion process after the gasoline engine ignition, namely the formation of the fire core, rapid flame development, and incomplete combustion in the later stage, which can further reflect the synergistic relationship between the spatial distribution of oil and gas and the combustion characteristics. In addition, under the spatial partitioning of the four quadrants, the influence of the change of the center position of the vortex or tumble on the diffusion of the fuel during the oil-gas mixing process can be taken into account, which can more clearly reflect the spatial distribution characteristics of the oil-gas mixing;

[0055] (2) The present invention can automatically extract data from different spatial partitions in CFD calculation results based on the spatial partition function and Tecplot macro commands, and can quickly obtain a series of calculated variable partition spatial average data including the mixture equivalence ratio, thereby effectively improving the efficiency of data post-processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is an overall flow chart of a combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine according to the present invention;

[0057] Figure 2 This is a schematic diagram of the "9-zone" space division according to an embodiment of the present invention;

[0058] Figure 3 This is a cloud diagram of the gas-fuel mixture equivalence ratio distribution under the "9-zone" spatial division according to an embodiment of the present invention;

[0059] Figure 4 This is a diagram showing the regional average value of the mixed gas equivalence ratio of each space in the "9 partitions" after data extraction in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0061] See also Figure 1-4 A combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine comprises the following steps:

[0062] Step 1: Use CFD software CONVERGE to establish a CFD calculation model for a direct injection gasoline engine, and extract the radius R of the central area of ​​the combustion chamber based on the geometric characteristic parameters of the model. S , cylinder radius R B , where the radius of the central area of ​​the combustion chamber is determined according to the actual shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. For combustion chambers of other configurations, R S =0.85*R B ; Extract the center coordinates of the lower surface of the fixed boundary cylinder head (x c ,y c , z c ), and move the global coordinate system xyz so that (x c ,y c , z c) is the origin of the coordinate system xyz (0, 0, 0); extract the coordinates of the center position of the spark plug electrode gap in the current coordinate system (x sp ,y sp , z sp );

[0063] Step 2: Based on the characteristic parameters extracted in step 1 and the global coordinate system xyz, and taking into account that the center position of the spark plug may not coincide with the center axis of the cylinder, establish the functions required for spatial partitioning, including a spark plug area extraction function for characterizing ignition stability, a center area extraction function for characterizing the rapid flame development process, and a clearance area extraction function for characterizing the late flame development process. The expression of the spark plug area extraction function for characterizing ignition stability is as follows:

[0064] SPARK_R1 2 ≤(x i -x sp ) 2 +(y i -y sp ) 2 +(z i -z sp ) 2

[0065] Among them, SPARK_R1 is the minimum fire core development radius required for the stable development of the flame formed after the spark is generated. It is generally believed that SPARK_R1 = ROUNDUP (0.05*R B ), ROUNDUP() is the rounding up function; x i 、y i 、z i is the spatial coordinate of each computational grid node in the local coordinate system.

[0066] The expression of the central region extraction function used to characterize the rapid flame development process is as follows:

[0067]

[0068] Where CENTER_R2 is the radius R of the center area of ​​the combustion chamber extracted in step 1 S , that is, the radius of the central cylindrical area of ​​the combustion chamber after removing the extrusion gap of the combustion chamber.

[0069] The expression of the clearance area extraction function used to characterize the late flame development process is as follows:

[0070]

[0071] The cylinder radius R extracted in step 1 B The radius R of the center area of ​​the combustion chamber SThe difference is the ring width of the combustion chamber squeeze gap ring column area CLEARANCE_R3, specifically CLEARANCE_R3 = R B -CENTER_R2.

[0072] The spatial partition is divided into 9 spatial areas, including 1 spark plug area, 4 center areas, and 4 clearance areas; the expression of 1 spark plug area is as follows:

[0073] R 2 ≤(x-x1) 2 +(y-y1) 2 +(z-z1) 2

[0074] Where R is set according to the size of the cylinder diameter, specifically R = ROUNDUP(0.05*Bore), ROUNDUP() is the rounding function, Bore is the cylinder diameter, (x1, y1, z1) is the position of the spark plug center, and (x, y, z) are the spatial coordinates of each computational grid node in the current coordinate system.

[0075] The four central areas are obtained by dividing the central areas of the four quadrants. The central area in the first quadrant is central area 1, the central area in the second quadrant is central area 2, the central area in the third quadrant is central area 3, and the central area in the fourth quadrant is central area 4. The specific expressions are as follows:

[0076] The spatial function of the center area 1 is:

[0077]

[0078] The spatial function of the center 2 area is

[0079]

[0080] The spatial function of the central 3 zones is:

[0081]

[0082] The spatial function of the central 4 zones is

[0083]

[0084] Where R1 is the radius of the central area, which is determined by the shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. If a flat-top combustion chamber or other irregular combustion chamber is used, R1 = 0.85*(Bore / 2).

[0085] The four clearance areas are obtained by dividing the four-quadrant clearance area. The clearance area in the first quadrant is clearance area 1, the clearance area in the second quadrant is clearance area 2, the clearance area in the third quadrant is clearance area 3, and the clearance area in the fourth quadrant is clearance area 4. The specific expressions are as follows:

[0086] The spatial function of clearance zone 1 is:

[0087]

[0088] The spatial function of clearance zone 2 is

[0089]

[0090] The spatial function of the clearance zone 3 is

[0091]

[0092] The spatial function of the clearance zone 4 is

[0093]

[0094] Step 3. Import the CONVERGE HDF5 format .out calculation data file containing the flow, spray, and combustion processes into the CFD post-processing software TECPLOT. The grid node coordinates and the calculation variable values ​​at the nodes within each calculation time step are arranged in a certain order. The calculation variables including the mixture equivalence ratio Equiv_Ratio and the calculation area number representing the in-cylinder working area surrounded by the cylinder wall, piston top surface, and cylinder head bottom surface can all be completed in Step 1. The data export settings in the .out file can be completed.

[0095] Step 4. Edit the user-defined formula Specify Equation in TECPLOT to calculate the intermediate variables L1 and L2 of the partition characteristic distance required by the spatial partition function in step 2, and add them to the grid node data obtained in step 3. The specific calculation expressions of the intermediate variables L1 and L2 are as follows:

[0096]

[0097] Where L1 represents the distance between the grid node and the center of the spark plug gap, and L2 represents the distance between the grid node and the center axis of the cylinder.

[0098] Step 5: Use the Value Blanking function in TECPLOT to blank the grid nodes at x. i and y i, the combustion chamber calculation area indication number excluding the intake and exhaust ducts, and the characteristic distances L1 and L2 obtained in step 4 are used to perform conditional operations on the spatial partition extraction function to select a grid subset whose node position satisfies the spatial distribution range of a certain partition among the 9 partitions;

[0099] Step 6: Use the Extract Blanked Zones function in TECPLOT to extract the calculated variable data based on the grid subsets that meet the partition space range conditions obtained in step 5;

[0100] Step 7: Perform mass-weighted average processing on the partitioned regional grid data extracted in step 6 to obtain the regional average value of the calculated variables including the mixture equivalence ratio. Regional average The calculation expression is as follows:

[0101]

[0102] in represents a computational variable, ρ i represents density, V i represents the grid volume, and n is the number of grids in the partition.

[0103] Step 8. Automatically repeat steps 5 to 7 by writing and executing macro commands until the average values ​​of the mixture equivalence ratios of the nine partitioned areas are completely extracted. By comparing the differences in the average values ​​of the mixture equivalence ratios in the nine areas, the spatial distribution of the fuel in the combustion chamber is quantitatively and clearly obtained.

[0104] Example

[0105] Taking a 74mm cylinder diameter two-stroke direct injection stratified combustion gasoline engine with a hemispherical combustion chamber structure as an example, the specific partitioning method is as follows:

[0106] Step 1: Use CFD software CONVERGE to establish a CFD calculation model of a certain type of direct injection gasoline engine, and extract the radius R of the central area of ​​the combustion chamber based on the geometric characteristic parameters of the model. S =0.0300m (This value is determined according to the actual shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. If other configurations of combustion chambers are used, R S =0.85*R B , cylinder radius R B = 0.0370m; extract the center coordinates of the lower surface of the fixed boundary cylinder head (x c ,y c , z c)=(-0.0030,0.0030,-0.0700), and move the global coordinate system xyz so that (x c ,y c , z c ) is the origin of the coordinate system xyz (0, 0, 0); extract the coordinates of the center position of the spark plug electrode gap in the current coordinate system (x sp ,y sp , z sp )=(0,0,0.0095).

[0107] Step 2: According to the feature parameter R extracted in step 1 S 、R B 、(x sp ,y sp , z sp ) and the global coordinate system xyz. Since the center position of the spark plug in the combustion chamber of this model coincides with the center axis of the cylinder, the function required to establish the spatial partition is as follows:

[0108] 1) The spark plug region extraction function used to characterize ignition stability is:

[0109] R sp 2 ≤(x i -x sp ) 2 +(y i -y sp ) 2 +(z i -z sp ) 2

[0110] where R sp It is the minimum radius of the flame core required for the stable development of the flame formed after the spark is generated. It is generally believed that R sp =ROUNDUP(0.05*R B ), ROUNDUP() is the rounding up function, x i 、y i 、z i The spatial coordinates of each computational grid node in the current coordinate system.

[0111] Substitute the feature parameters extracted in step 1 and calculate:

[0112] 0.0019 2 ≤(x i -0) 2 +(y i -0) 2 +(z i -0.0095) 2

[0113] 2) The four-quadrant central region extraction function used to characterize the rapid flame development process is as follows, where the central region in the first quadrant is called central region 1, the central region in the second quadrant is called central region 2, and so on.

[0114] The central area space extraction function is:

[0115]

[0116] Substitute the feature parameters extracted in step 1 and calculate:

[0117] The spatial extraction function of the center area 1 is:

[0118]

[0119] The spatial function of the center 2 area is the extraction function:

[0120]

[0121] The spatial function of the central 3 areas is the extraction function:

[0122]

[0123] The spatial function of the central 4 areas is the extraction function:

[0124]

[0125] 3) The four-quadrant clearance region extraction function used to characterize the late flame development process is as follows, where the clearance region in the first quadrant is called clearance region 1, the clearance region in the second quadrant is called clearance region 2, and so on.

[0126]

[0127] Substitute the feature parameters extracted in step 1 and calculate:

[0128] The spatial function of clearance zone 1 is:

[0129]

[0130] The spatial function of clearance zone 2 is:

[0131]

[0132] The spatial function of the clearance zone 3 is:

[0133]

[0134] The spatial function of the clearance zone 4 is:

[0135]

[0136] The above partition function is based on the three combustion chamber structural characteristic parameters R B 、R S 、R sp and four spatial quadrants in the xoy plane, and the grid node position and the spark plug position (x sp ,y sp , z sp ) and the characteristic distance between the cylinder center position, the combustion chamber can be divided into 9 spatial regions, as shown in the following Figure 2 Specifically shown are 1 spark plug area, 4 center areas, and 4 clearance areas.

[0137] Step 3: Complete the calculation of the CFD model of the direct injection gasoline engine in Step 1 and import the CONVERGE HDF5 format .out calculation data file containing the flow, spray, and combustion processes into the CFD post-processing software TECPLOT. The grid node coordinates and the calculation variable values ​​on the nodes within each calculation time step will be arranged in a certain order, as shown in Table 1:

[0138] Table 1 Grid node dataset

[0139] <![CDATA[x i / m]]> <![CDATA[y i / m]]> <![CDATA[z i / m]]> ID_Region / - Equiv_Ratio / - … 0.021103 0.0265170 0.000001 0 1.28452 … 0.002103 0.0209983 0.003415 0 0.72145 … 0.010896 0.008271 0.001359 1 0.0000000 … … … … … … …

[0140] The calculation variables including the mixture equivalence ratio (Equiv_Ratio) and the calculation region number (ID_Region=0) representing the combustion chamber region surrounded by the cylinder wall, piston top surface, and cylinder head bottom surface can all be completed in the data export settings in the .out file in step one.

[0141] Step 4. Edit the user-defined formula (Specify Equation) in TECPLOT to calculate the intermediate variables required by the spatial partition function in step 2, namely the distance between the grid node position and the spark plug position, and the distance between the grid node position and the cylinder center feature.

[0142]

[0143] And add it to the grid node data obtained in step 3, as shown in Table 2:

[0144] Table 2 Grid node dataset after adding feature distance data

[0145]

[0146] Step 5: Use the Value Blanking function in TECPLOT to perform conditional operations on the combustion chamber calculation region indicator number (ID_Region = 0) that does not include the intake and exhaust ducts, and the characteristic distances L1 and L2 obtained in step 4. Then, a grid subset whose node position satisfies the spatial distribution range of one of the nine partitions is selected, as shown in Table 3:

[0147] Table 3 Filtered data subset of grid nodes in the central zone 1

[0148]

[0149]

[0150] Step 6. Use the Extract Blanked Zones function in TECPLOT to extract the calculated variable data including the mixture equivalence ratio based on the grid subset that meets the partition space range conditions obtained in Step 5, as shown in Table 4:

[0151] Table 4 Completed extraction of grid calculation data for the center area 1

[0152]

[0153] Step 7: Perform mass-weighted average processing on the partitioned regional grid data extracted in step 6 to obtain the regional average value of the calculation variables including the mixture equivalence ratio.

[0154]

[0155] in represents a computational variable, ρ i represents density, V i The mass average calculation of the gas-fuel mixture equivalence ratio data in the center zone 1 yields a regional average of 0.95641.

[0156] Step 8. By writing and executing macro commands, steps 5 to 7 can be automatically repeated until the average value of the mixture equivalence ratio of the nine partitioned areas is completely extracted. By comparing the differences in the average value of the mixture equivalence ratio of the nine areas, the spatial distribution of the fuel in the combustion chamber can be quantitatively and clearly obtained.

[0157] Finally, we get Figure 4 The regional average value of the mixture equivalence ratio in the 9 regions shown is as follows. Figure 3The equivalence ratio cloud diagram before data extraction is shown. It can be found that the regional average value of the mixture equivalence ratio as quantitative data can effectively characterize the uneven distribution of oil and gas in the combustion chamber space: for example, there is fuel accumulation in gaps 1, 3, and 4 (equivalence ratio>1), and a local rich area suitable for the rapid development of the fire core can be formed near the spark plug. By extracting data in different areas and quantitatively characterizing them, the oil and gas distribution status in the combustion chamber can be quickly obtained, providing a decision-making basis for combustion system optimization.

[0158] Therefore, the present invention adopts the above-mentioned combustion chamber zoning method for analyzing the spatial distribution characteristics of oil and gas in GDI gasoline engines. According to the combustion chamber structure and the flame space development process, the spark plug area, the combustion chamber center area, the combustion chamber clearance area and the 9-interval division method combined with the 4-quadrant spatial coordinates are adopted to accurately determine the specific spatial position of the mixture distribution suitable for combustion in the combustion chamber, further analyze the synergistic relationship between the oil and gas spatial distribution, the flow field in the cylinder, and the combustion process, and provide a reliable means for analyzing the spatial distribution characteristics of oil and gas in direct injection gasoline engines.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine, characterized in that: The following steps are involved: Step 1: Use CFD software CONVERGE to establish a CFD calculation model of the direct injection gasoline engine, and extract the central area radius of the combustion chamber based on the model's geometric characteristic parameters. , cylinder radius , where the radius of the central area of ​​the combustion chamber is determined according to the actual shape of the combustion chamber. For a hemispherical combustion chamber, this value is the distance from the center of the cylinder to the edge of the hemispherical dome. For combustion chambers of other configurations, ; Extract the center coordinates of the lower surface of the fixed boundary cylinder head ( , , ), and move the global coordinate system xyz so that ( , , ) is the origin of the coordinate system xyz (0, 0, 0); extract the coordinates of the center position of the spark plug electrode gap in the current coordinate system ( , , ); Step 2: Based on the characteristic parameters extracted in step 1 and the global coordinate system xyz, the functions required for spatial partitioning are established, including a spark plug region extraction function for characterizing ignition stability, a center region extraction function for characterizing the rapid flame development process, and a clearance region extraction function for characterizing the late flame development process. Step 3. Import the CONVERGE HDF5 format .out calculation data file containing the flow, spray, and combustion processes into the CFD post-processing software TECPLOT. The grid node coordinates and the calculation variable values ​​at the nodes within each calculation time step are arranged in a certain order. The calculation variables including the mixture equivalence ratio Equiv_Ratio and the calculation area number representing the in-cylinder working area surrounded by the cylinder wall, piston top surface, and cylinder head bottom surface are all completed in the data export settings of the .out file in Step 1. Step 4. Edit the user-defined formula Specify Equation in TECPLOT to calculate the intermediate variable of the partition characteristic distance of the function required for spatial partitioning in step 2. 、 , and add it to the grid node data obtained in step 3; Step 5: Use the Value Blanking function in TECPLOT to adjust the grid node positions. and , the combustion chamber calculation area indicator number excluding the intake and exhaust ports, and the characteristic distance obtained in step 4 、 Perform conditional operations on the spatial partition extraction function to filter out a subset of grids whose node positions meet the spatial distribution range of one of the nine partitions. Step 6: Use the Extract Blanked Zones function in TECPLOT to extract the calculated variable data based on the grid subsets that meet the partition space range conditions obtained in step 5; Step 7: Perform mass-weighted average processing on the partitioned regional grid data extracted in step 6 to obtain the regional average value of the calculated variables including the mixture equivalence ratio. ; Step 8: Automatically repeat steps 5 to 7 by writing and executing macro commands until the average values ​​of the mixture equivalence ratios of the nine partitioned areas are completely extracted. The spatial distribution of the fuel in the combustion chamber is obtained by comparing the differences in the average values ​​of the mixture equivalence ratios of the nine areas.

2. The combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine according to claim 1 is characterized in that: The expression of the spark plug area extraction function used to characterize ignition stability in step 2 is as follows: ； SPARK_R1 is the minimum fire core development radius required for the stable development of the flame formed after the spark is generated. , ROUNDUP() is the rounding up function; is the spatial coordinate of each computational grid node in the local coordinate system.

3. The combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine according to claim 2 is characterized in that: The expression of the central area extraction function used to characterize the rapid flame development process in step 2 is as follows: ； Where CENTER_R2 is the radius of the center area of ​​the combustion chamber extracted in step 1 , is the radius of the central cylindrical area of ​​the combustion chamber after removing the extrusion gap of the combustion chamber.

4. The combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine according to claim 3 is characterized in that: The expression of the clearance area extraction function used to characterize the late flame development process in step 2 is as follows: ； The cylinder radius extracted in step 1 is Radius from the center of the combustion chamber The difference is the ring width CLEARANCE_R3 of the combustion chamber squeeze gap ring column area, specifically CLEARANCE_R3= - CENTER_R2.

5. The combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine according to claim 4, characterized in that: The space is divided into 9 spatial areas, including 1 spark plug area, 4 center areas, and 4 clearance areas.

6. The combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine according to claim 5, characterized in that: The expression for one spark plug area is as follows: ； In the formula, R is set according to the size of the cylinder diameter, specifically R=ROUNDUP( ), ROUNDUP() is the rounding up function, Bore is the cylinder diameter, ( , , ) is the position of the spark plug center, ( , , ) are the spatial coordinates of each computational grid node in the current coordinate system.

7. The combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine according to claim 6, characterized in that: The four central areas are obtained by dividing the central areas of the four quadrants. The central area in the first quadrant is central area 1, the central area in the second quadrant is central area 2, the central area in the third quadrant is central area 3, and the central area in the fourth quadrant is central area 4. The specific expressions are as follows: The spatial function of the center area 1 is: ； The spatial function of the center 2 area is ； The spatial function of the central 3 zones is: ； The spatial function of the central 4 zones is ； Where R1 is the radius of the central area.

8. The combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine according to claim 7, characterized in that: The four clearance areas are obtained by dividing the four-quadrant clearance area. The clearance area in the first quadrant is clearance area 1, the clearance area in the second quadrant is clearance area 2, the clearance area in the third quadrant is clearance area 3, and the clearance area in the fourth quadrant is clearance area 4. The specific expressions are as follows: The spatial function of clearance zone 1 is: ； The spatial function of clearance zone 2 is ； The spatial function of the clearance zone 3 is ； The spatial function of the clearance zone 4 is 。 9. The combustion chamber partitioning method for analyzing the oil and gas spatial distribution characteristics of a GDI gasoline engine according to claim 8, characterized in that: Intermediate variables 、 The specific calculation expression is as follows: ； ； Where, represents the distance between the grid node and the center of the spark plug gap, Represents the distance between the mesh node and the center axis of the cylinder.

10. The combustion chamber partitioning method for analyzing the spatial distribution characteristics of oil and gas in a GDI gasoline engine according to claim 9, characterized in that: Regional average The calculation expression is as follows: ； in represents a calculated variable, represents density, represents the grid volume, and n is the number of grids in the partition.

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