JP7247845B2 - Heat transfer analyzer - Google Patents

Description

The present invention belongs to a technical field related to a heat transfer analysis apparatus for performing heat transfer analysis of a structure including a heat source and a structure receiving heat from the heat source.

Conventionally, there is known a heat transfer analysis apparatus that performs heat transfer analysis (simulation) of a structure that receives heat from a heat source (see, for example, Patent Document 1). In the heat transfer analysis apparatus of Patent Document 1, the heat transfer analysis of a structure is performed using a one-dimensional heat transfer model in order to reduce the scale of the calculation model and shorten the calculation time. However, in order to improve the accuracy of the heat transfer analysis, the heat transfer model is corrected according to environmental changes of the heat transfer elements.

JP 2009-199355 A

However, it may be difficult to perform accurate heat transfer analysis only with a one-dimensional heat transfer model. For example, when conducting a heat transfer analysis of an engine piston, it is usually necessary to use a three-dimensional heat transfer model.

By the way, in some cases, a film portion such as a heat insulating film is formed on the crown surface of the piston body. It is conceivable to apply a three-dimensional heat transfer model to such a film portion in order to perform an accurate heat transfer analysis. When applying this three-dimensional heat transfer model, the number of grids (mesh) increases, so there is a problem that the calculation load increases further and the calculation time becomes considerably long.

The present invention has been made in view of the above points, and an object of the present invention is to provide a film-like first structural portion that receives heat from a heat source on one side in the thickness direction, and the first structure. In the heat transfer analysis of a structure having a second structural part superimposed on the other side surface in the thickness direction of the part, heat transfer that can achieve both suppression of increase in calculation load and securing of calculation accuracy An object of the present invention is to provide an analysis device.

To achieve the above object, the present invention provides a heat transfer analysis apparatus for performing heat transfer analysis of a structure in a system including a heat source and a structure receiving heat from the heat source, wherein the structure is , a film-like first structural portion that receives heat from the heat source on one side in the thickness direction, and a second structural portion superimposed on the other side in the thickness direction of the first structural portion. , the length of the second structural portion in the direction in which it overlaps with the first structural portion is greater than the thickness of the first structural portion, and a one-dimensional heat transfer model is used to determine the first Using a first heat transfer analysis section that performs heat transfer analysis in the thickness direction of the structural section and a two-dimensional or three-dimensional heat transfer model, two or three directions including the superimposition direction of the second structural section and a second heat transfer analysis unit that performs heat transfer analysis.

With the above configuration, the first heat transfer analysis section uses a one-dimensional heat transfer model to perform heat transfer analysis in the thickness direction of the first structural section, so an increase in calculation load can be suppressed. On the other hand, even if a one-dimensional heat transfer model is applied to the first structural part, if the thickness of the first structural part is smaller than the length of the second structural part in the overlapping direction with the first structural part, In combination with the fact that the second heat transfer analysis section uses a two-dimensional or three-dimensional heat transfer model to perform the heat transfer analysis, sufficient calculation accuracy can be ensured.

In the heat transfer analysis device, the first heat transfer analysis unit uses a one-dimensional heat transfer model to calculate the thickness of the first structural portion only when the thickness of the first structural portion is equal to or less than a predetermined threshold value. While performing the heat transfer analysis in the direction, if the thickness of the first structure portion is greater than the predetermined threshold, a two-dimensional or three-dimensional heat transfer model is used to analyze the thickness direction of the first structure portion. Preferably, it is configured to perform two-way or three-way heat transfer analysis.

As a result, when the thickness of the first structure portion is equal to or less than the predetermined threshold value, it is possible to further improve the calculation accuracy while suppressing an increase in the calculation load in the heat transfer analysis of the structure.

In one embodiment of the preferred configuration, the structure is an engine piston, the second structure is a piston body, and the first structure is a first structure formed on the crown surface of the piston body. wherein the first film portion has a thermal conductivity set lower than the thermal conductivity of the piston body and a volumetric specific heat set lower than the volumetric specific heat of the piston body. The second heat transfer analysis section is configured to perform heat transfer analysis in three directions including the overlapping direction of the piston body using a three-dimensional heat transfer model.

As a result, when the thickness of the first film portion is equal to or less than the predetermined threshold value, it is possible to ensure both calculation accuracy and suppress an increase in calculation load in the heat transfer analysis of the engine piston.

In the above embodiment, between the central portion of the crown surface of the piston body and the first film portion, the surfaces on one side and the other side in the thickness direction are respectively on the first film portion and the piston body. A contacting second membrane may be provided. In this case, the second film portion has a thermal conductivity set lower than that of the piston body and a volumetric specific heat set larger than the volumetric specific heat of the piston body. The thermal analysis apparatus further includes a third heat transfer analysis section that performs heat transfer analysis of the second film section. When the total thickness of the first film portion and the second film portion is equal to or less than the predetermined threshold value, the third heat transfer analysis section uses a one-dimensional heat transfer model to On the other hand, when the total thickness is greater than the predetermined threshold value, a three-dimensional heat transfer model is used to analyze the thickness direction of the second film portion. It is preferably configured to perform heat transfer analysis in three directions, including:

As a result, when the total thickness of the first film portion and the second film portion is equal to or less than a predetermined threshold value, in the heat transfer analysis of the engine piston, both ensuring calculation accuracy and suppressing an increase in calculation load can be achieved. can be achieved.

The predetermined threshold is preferably set to 2.5 mm.

As a result, when the thickness of the first structure portion is 2.5 mm or less, it is possible to further improve the calculation accuracy while suppressing an increase in the calculation load in the heat transfer analysis of the structure.

In the heat transfer analysis device, the second heat transfer analysis section is configured to perform heat transfer analysis in three directions including the overlapping direction of the second structural section using a three-dimensional heat transfer model. preferably.

As a result, the calculation accuracy can be further improved in the heat transfer analysis of the structure.

As described above, according to the heat transfer analysis apparatus of the present invention, the first heat transfer analysis section performs heat transfer analysis in the thickness direction of the first structural section using a one-dimensional heat transfer model; a second heat transfer analysis section that uses a three-dimensional heat transfer model to perform heat transfer analysis in two or three directions, including the overlapping direction of the second structural section and the first structural section. As a result, in the heat transfer analysis of the structure, it is possible to achieve both suppression of an increase in calculation load and securing of calculation accuracy.

1 is a block diagram showing a heat transfer analysis device according to Embodiment 1. FIG. FIG. 2 is a simplified cross-sectional view showing an engine piston, which is an object of heat transfer analysis by the heat transfer analysis device; 4 is a flowchart showing piston heat transfer analysis processing by a heat transfer analysis controller of the heat transfer analysis apparatus; In the structure shown in FIG. 5, when the heat transfer analysis in the x direction of the first structural portion is performed using the one-dimensional heat transfer model, the x direction of the first structural portion using the two-dimensional heat transfer model. and y-direction heat transfer analysis, and FIG. (b) shows the error when the temperature gradient is 50 K/cm, and (c) shows the error when the temperature gradient is 100 K/cm. It is a sectional view showing the above-mentioned structure. 4 is a graph showing a y-direction temperature gradient of the temperature of the lower surface of the first structural portion; 4 is a graph showing the relationship between the film thickness of the first structure portion and the error when the temperature gradient is 100 K/cm. FIG. 5 is a block diagram showing a heat transfer analysis device according to Embodiment 2; FIG. 7 is a simplified cross-sectional view showing an engine piston, which is an object of heat transfer analysis by the heat transfer analysis apparatus according to Embodiment 2; Regarding the engine piston, a case where heat transfer analysis was performed for the entire engine piston using a one-dimensional heat transfer model, and a case where the first heat insulating film portion and the second heat insulating film portion were analyzed using the one-dimensional heat transfer model. Shown are the analysis results of a heat transfer analysis and a heat transfer analysis of the piston body using a three-dimensional heat transfer model. 10B is a graph showing the change in the heat flux of the combustion chamber side surface of the first heat shield film portion with respect to the crank angle, and (b) is a graph showing the change in the heat flux with respect to the crank angle at the position where the distance R is 3.1 mm. 1 is a graph showing changes in heat flux on the combustion chamber side surface of the first heat shield film portion, and (c) shows combustion in the first heat shield film portion with respect to the crank angle at a position where the distance R is 4.2 mm. 4 is a graph showing changes in heat flux on the chamber-side surface;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

(Embodiment 1)
FIG. 1 shows a heat transfer analysis device 1 according to Embodiment 1 of the present invention. This heat transfer analysis apparatus 1 performs heat transfer analysis of a structure in a system including a heat source and a structure receiving heat from the heat source.

In this embodiment, the structure to be subjected to the heat transfer analysis by the heat transfer analysis apparatus 1 is the engine piston 11 which receives heat from the gas (heat source) in the combustion chamber, as shown in simplified form in FIG.

The engine piston 11 has a piston body 12 made of an aluminum alloy and a heat insulating film portion 13 formed on the crown surface of the piston body 12 . The heat insulating film portion 13 corresponds to the first structural portion, and the piston body 12 corresponds to the second structural portion. That is, the heat insulating film portion 13 receives heat from the gas in the combustion chamber on one side surface (the surface on the side of the combustion chamber) in the thickness direction of the heat insulating film portion 13 . The piston main body 12 is superimposed on the surface of the heat shield film portion 13 on the other side in the thickness direction (the surface on the side opposite to the combustion chamber). The length of the piston main body 12 in the overlapping direction with the heat insulating film portion 13 (in the central axis direction (vertical direction) of the engine piston 11 ) is set larger than the thickness of the heat insulating film portion 13 .

The heat shield film portion 13 is a film portion having a thermal conductivity set lower than that of the piston body 12 and a volume specific heat set lower than that of the piston body 12 . As a material of the heat insulating film portion 13, for example, a heat-resistant silicone resin can be exemplified. Examples of silicone resins include silicone resins composed of three-dimensional polymers with a high degree of branching, represented by methyl silicone resins and methylphenyl silicone resins. For example, polyalkylphenyl siloxanes are suitable. Such silicone resins may contain hollow particles such as shirasu balloons.

Since the temperature of the heat shield film portion 13 tends to fluctuate following the temperature inside the combustion chamber, which changes greatly, the heat shield film portion 13 suppresses the heat inside the combustion chamber from escaping to the piston body 12. As a result, the cooling loss of the engine provided with the engine piston 11 is reduced.

As shown in FIG. 1, the heat transfer analysis apparatus 1 includes a known microcomputer-based heat transfer analysis controller 2 , an input device 3 operated by a user for input, and a display device 4 .

The heat transfer analysis controller 2 has a CPU, memory, input/output bus, and the like. The CPU is a central processing unit that executes computer programs (including basic control programs such as an OS, and application programs that are started on the OS and implement specific functions). The memory is composed of RAM and ROM. Various computer programs and data are stored in the ROM. The RAM is a memory provided with a processing area used when the CPU performs a series of processes. The input/output bus inputs/outputs electrical signals to/from the heat transfer analysis controller 2 .

In this embodiment, the heat transfer analysis controller 2 includes a first heat transfer analysis section 2a, a second heat transfer analysis section 2b, and a display control section 2c. The first heat transfer analysis section 2a, the second heat transfer analysis section 2b, and the display control section 2c operate as described later according to the computer program stored in the ROM.

Information input by the user to the input device 3 is input to the first heat transfer analysis section 2a and the second heat transfer analysis section 2b. The input information includes heat transfer analysis of the engine piston 11 (piston body 12 and heat shield film 13), such as the shape, material, initial conditions (initial temperature, etc.) of the piston body 12 and heat shield film 13. information necessary for

The display control device 2c causes the display device 4 to display information required by the user (input to the input device) from the results of heat transfer analysis by the first heat transfer analysis unit 2a and the second heat transfer analysis unit 2b. . In this embodiment, the information required by the user is the temperature distribution of the surface of the heat insulating film 13 on the side of the combustion chamber.

The first heat transfer analysis unit 2a uses a one-dimensional heat transfer model to perform heat transfer analysis in the thickness direction (vertical direction) of the heat shield film part 13 . However, in the present embodiment, the first heat transfer analysis unit 2a uses the one-dimensional heat transfer model only when the thickness of the heat shield film portion 13 is equal to or less than a predetermined threshold value. Perform directional heat transfer analysis. When the thickness of the heat shield film portion 13 is greater than the predetermined threshold value, the first heat transfer analysis unit 2a uses a three-dimensional heat transfer model to analyze three directions including the thickness direction of the heat shield film portion 13. Conduct a heat transfer analysis.

The second heat transfer analysis unit 2b uses a three-dimensional heat transfer model to perform heat transfer analysis in three directions including the superimposition direction (vertical direction) of the piston body 12 .

Even if the first heat transfer analysis unit 2a performs a heat transfer analysis of the heat shield film 13 using a one-dimensional heat transfer model, the predetermined threshold is set to It is a value that sufficiently reduces the error (the error in the case where the heat transfer analysis of the heat shield film portion 13 is performed using a three-dimensional heat transfer model). In this embodiment, the predetermined threshold is set to 2.5 mm.

In the three-dimensional heat transfer model, the following three-dimensional heat transfer equation is solved for each lattice divided and generated in three dimensions.

In the above heat transfer equation, ρ is density, c is specific heat, T is temperature, t is time, k is thermal conductivity, and x, y, z are positions in the above three directions. Here, x is the position of the piston body 12 in the superimposition direction (vertical direction), and y and z are positions in two horizontal directions perpendicular to each other.

On the other hand, in a one-dimensional heat transfer model, the following one-dimensional heat transfer equation is solved for each lattice divided and generated in one dimension.

Here, x is the position in the thickness direction (vertical direction) of the heat insulating film portion 13 .

At the boundary between the heat shield film portion 13 and the piston body 12, the following boundary conditions are given. That is, the temperature of the surface (lower surface) of the heat shield film portion 13 on the side opposite to the combustion chamber is equal to the temperature of the upper surface of the piston body 12, and the heat flux of the lower surface of the heat shield film portion 13 is equal to that of the upper surface of the piston body 12. equal to the heat flux.

In parallel with the heat transfer analysis of the engine piston 11 by the heat transfer analysis device 1 (heat transfer analysis controller 2), the heat transfer analysis of the gas in the combustion chamber is performed by the fluid analysis controller 7 (see FIG. 1) of the fluid analysis device. will be This gas heat transfer analysis is also performed using a three-dimensional heat transfer model, similar to the heat transfer analysis of the piston body 12 by the second heat transfer analysis unit 2b. The fluid analysis controller 7 exchanges information with the heat transfer analysis controller 2 . The fluid analysis controller 7 may also be used as the heat transfer analysis controller 2 .

At the boundary portion between the heat shield film portion 13 and the gas, the following boundary conditions (that is, heat input conditions from the heat source to the heat shield film portion 13) are given. That is, the temperature of the surface (upper surface) of the heat shield film portion 13 on the side of the combustion chamber is equal to the temperature of the portion in contact with the heat shield film portion 13 of the gas, and the heat flux of the upper surface of the heat shield film portion 13 is equal to that of the gas. It is equal to the heat flux of the portion in contact with the heat insulating film portion 13 .

FIG. 3 is a flowchart showing piston heat transfer analysis processing by the heat transfer analysis controller 2 . This flowchart is started, for example, by a switch operation via the input device 3 by the user. It should be noted that the user inputs information necessary for the heat transfer analysis of the engine piston 11 before operating the switch.

In the first step S1, the shape of the engine piston 11 (the piston body 12 and the heat insulating film portion 13) is read, and in the next step S2, it is determined whether or not the thickness of the heat insulating film portion 13 is 2.5 mm or less. do.

If the determination in step S2 is YES, the process proceeds to step S3 to generate a one-dimensional grid for the heat shield film portion 13 and a three-dimensional grid for the piston body 12, and then proceeds to step S5.

On the other hand, if the determination in step S2 is NO, the process proceeds to step S4 to generate a three-dimensional grid for the entire engine piston 11, and then proceeds to step S5.

In step S5, initial conditions are set, and in the next step S6, it is determined whether or not the heat transfer calculations in steps S10 and S11 described below or the heat transfer calculations in step S12 described later have been completed.

If the determination in step S6 is NO, the process proceeds to step S7 to set the time increments. This time increment is finer as the phenomenon changes more rapidly.

In the next step S8, a boundary condition at the boundary portion between the heat insulating film portion 13 and the piston body 12 and a boundary condition (heat input condition) at the boundary portion between the heat insulating film portion 13 and the gas are set.

In the next step S9, it is determined whether or not there is a lattice generated in one dimension. If the determination in step S9 is YES, the process proceeds to step S10, where the first heat transfer analysis unit 2a uses a one-dimensional heat transfer model to perform heat transfer calculation (heat transfer analysis), and in the following step S11, the second heat transfer analysis unit 2b uses a three-dimensional heat transfer model to perform heat transfer calculation (heat transfer analysis) of the piston body 12, and then step S6. return.

On the other hand, if the determination in step S9 is NO, the process proceeds to step S12, where the first heat transfer analysis unit 2a and the second heat transfer analysis unit 2b analyze the heat shield film using a three-dimensional heat transfer model. Heat transfer calculation (heat transfer analysis) of the portion 13 and the piston body 12 is performed, and then the process returns to step S6.

The processing operations of steps S7 to S11 or the processing operations of steps S7 to S9 and S12 are repeated until the heat transfer calculations by the first heat transfer analysis unit 2a and the second heat transfer analysis unit 2b are completed. Then, when the heat transfer calculation by the first heat transfer analysis unit 2a and the second heat transfer analysis unit 2b is completed and the determination in step S6 becomes YES, the process proceeds to step S13, and the display control unit 2c controls the heat shield film. The temperature distribution of the combustion chamber side surface of the portion 13 is displayed on the display device 4, and then the piston heat transfer analysis process is terminated.

FIGS. 4A to 4C show the structure 21 shown in FIG. Heat transfer analysis in the x-direction and y-direction of the first structural portion 22 using a two-dimensional heat transfer model when heat transfer analysis in the x-direction of the first structural portion 22 is performed using a dimensional heat transfer model. is a diagram showing the error in the temperature of the upper surface (the surface on the heat source side) of the first structural portion 22 in the case of performing . In both cases, a two-dimensional heat transfer model is used to analyze heat transfer in the x and y directions for the second structural portion 23 .

Here, the temperature of the upper surface of the first structural portion 22 is T1, the temperature of the lower surface of the first structural portion 22 (the surface on the side of the second structural portion 23) is T2, and the temperature T2 of the lower surface is as shown in FIG. In addition, it is assumed that the temperature changes in the y direction with a constant temperature gradient. FIG. 4(a) shows the error when the y-direction temperature gradient of the temperature T2 of the lower surface is 30 K/cm, and FIG. 4(b) shows the error when the temperature gradient is 50 K/cm. , FIG. 4(c) shows the error when the temperature gradient is 100 K/cm.

4A to 4C, the horizontal axis is the film thickness of the first structural portion 22, and the vertical axis is the average value of the temperature of the upper surface and the temperature of the lower surface of the first structural portion 22. difference (referred to as temperature difference in the thickness direction). In FIGS. 4A to 4C, for example, the error is in the range of 0.00% to 0.50% in the white portions.

As shown in FIGS. 4A to 4C, the larger the film thickness of the first structural portion 22, the larger the error. Further, the larger the temperature gradient and the larger the temperature difference in the thickness direction, the larger the error. Even if the temperature gradient and the temperature difference in the thickness direction are large, the error is small, being 0.50% or less, if the film thickness is 2.5 mm or less. For this reason, the predetermined threshold is preferably set to 2.5 mm.

FIG. 7 is a graph showing the relationship between the film thickness of the first structural portion 22 and the error when the temperature gradient is 100 K/cm. Here, the temperature difference in the thickness direction is assumed to be a constant value.

In the graph of FIG. 7, the amount of increase in error with respect to the increase in film thickness differs from the position where the film thickness of the first structure portion 22 is 2.5 mm. That is, the graph in FIG. 4 is a straight line when the film thickness exceeds 2.5 mm, and the error greatly increases as the film thickness increases. On the other hand, the graph of FIG. 7 is a curve close to a parabola that is convex downward when the film thickness is 2.5 mm or less, and the increase in error with respect to the film thickness is small. For this reason as well, the predetermined threshold is preferably set to 2.5 mm.

Note that when the heat transfer analysis of the first structural portion 22 is performed using the one-dimensional heat transfer model and the heat transfer analysis of the second structural portion 23 is performed using the three-dimensional heat transfer model, the three-dimensional Errors in the temperature of the upper surface of the first structural portion 22 are also shown in FIGS. 4(a) to 4(c) and The same tendency as in FIG. 7 is obtained.

Therefore, in the present embodiment, if the thickness of the heat shield film portion 13 is equal to or less than the predetermined threshold value, it is possible to suppress an increase in the calculation load and ensure the calculation accuracy in the heat transfer analysis of the engine piston 11. can. In particular, if the thickness of the heat shield film portion 13 is 2.5 mm or less, in the heat transfer analysis of the engine piston 11, calculation accuracy can be further improved while suppressing an increase in calculation load.

In the above-described embodiment, an example in which the structure to be analyzed by the heat transfer analysis device 1 is the engine piston 11 is shown, but the structure is not limited to this. A film-shaped first structural portion that receives heat from a heat source on one side in the thickness direction, and a second structural portion that is superimposed on the other side in the thickness direction of the first structural portion. If the length of the second structural portion in the overlapping direction with the first structural portion is larger than the thickness of the first structural portion, the heat transfer analysis by the heat transfer analysis device 1 is performed. Can be targeted. Further, if the thickness of the first structural portion is smaller than the length of the second structural portion in the overlapping direction with the first structural portion, the one-dimensional heat transfer model is always used to determine the thickness of the first structural portion. It is also possible to perform heat transfer analysis in the thickness direction. Furthermore, if the second structural portion has, for example, a shape that elongates when viewed from the overlapping direction, a two-dimensional heat transfer model is used to determine the shape of the second structural portion including the overlapping direction. It is also possible to perform directional heat transfer analysis.

(Embodiment 2)
FIG. 8 shows a heat transfer analysis apparatus 1 according to Embodiment 2 of the present invention, and FIG. 9 shows an engine piston 11 as a structure to be subjected to heat transfer analysis by the heat transfer analysis apparatus 1. As shown in FIG. In FIGS. 8 and 9, the same parts as in FIGS. 1 and 2 are given the same reference numerals, and detailed description thereof is omitted.

In this embodiment, between the central portion of the crown surface of the piston body 12 and the heat insulating film portion 13 (hereinafter referred to as the first heat insulating film portion 13), the surfaces on one side and the other side in the thickness direction are the first A second heat shielding film portion 14 (corresponding to a second film portion) is provided in contact with the heat shielding film portion 13 and the piston body 12, respectively. The second heat insulating film portion 14 is a film portion having a thermal conductivity set lower than that of the piston body 12 and a volumetric specific heat set larger than that of the piston body 12 . The thermal conductivity of the second heat shield film portion 14 is set higher than the heat conductivity of the first heat shield film portion 13 . That is, the second heat shield film portion 14 has a higher heat storage property than the first heat shield film portion 13 and has a role of increasing the temperature of the first heat shield film portion 13 . As a result, the temperature of the first heat insulating film portion 13 approaches the temperature of the gas in the combustion chamber, and as a result, the escape of heat in the combustion chamber to the piston body 12 is further suppressed.

As a material of the second heat insulating film portion 14, for example, a ceramic material can be exemplified. In general, a ceramic material has low thermal conductivity, high volumetric specific heat, and excellent heat resistance. Specifically, a preferred ceramic material is zirconia. In addition, ceramic materials such as silicon nitride, silica, cordierite, and mullite can also be exemplified.

In this embodiment, in the heat transfer analysis controller 2, in addition to the first heat transfer analysis unit 2a, the second heat transfer analysis unit 2b, and the display control unit 2c similar to those in the first embodiment, a second heat shield A third heat transfer analysis section 2 d is provided for performing heat transfer analysis of the film portion 14 .

When the total thickness of the first heat shield film portion 13 and the second heat shield film portion 14 is equal to or less than the predetermined threshold value, the third heat transfer analysis unit 2d uses a one-dimensional heat transfer model to While the heat transfer analysis in the thickness direction of the second heat shield film portion 14 is performed, if the total thickness is greater than the predetermined threshold value, the second heat shield film portion 14 is analyzed using a three-dimensional heat transfer model. Perform heat transfer analysis in three directions including the thickness direction. Also in this embodiment, the predetermined threshold value is set to 2.5 mm as in the first embodiment.

When the thickness of the heat shield film portion 13 is equal to or less than the predetermined threshold value, the first heat transfer analysis unit 2a uses a one-dimensional heat transfer model to analyze the heat shield film portion 13 as in the first embodiment. On the other hand, if the thickness of the heat shield film portion 13 is greater than the predetermined threshold value, a three-dimensional heat transfer model is used to perform a heat transfer analysis including the thickness direction of the heat shield film portion 13. Perform directional heat transfer analysis.

As in the first embodiment, the second heat transfer analysis unit 2b uses a three-dimensional heat transfer model to perform heat transfer analysis in three directions including the superimposed direction (vertical direction) of the piston body 12 .

In the present embodiment, if the total thickness of the first heat insulating film portion 13 and the second heat insulating film portion 14 is equal to or less than the predetermined threshold value, in the heat transfer analysis of the engine piston 11, as in the first embodiment, , it is possible to ensure both the calculation accuracy and the suppression of an increase in the calculation load. In particular, if the total thickness is 2.5 mm or less, in the heat transfer analysis of the engine piston 11, calculation accuracy can be further improved while suppressing an increase in calculation load.

FIGS. 10A to 10C show the engine piston 11 of the second embodiment when heat transfer analysis is performed using a one-dimensional heat transfer model for the entire engine piston 11 (heat transfer analysis A case). Then, the heat transfer analysis of the first heat shield film portion 13 and the second heat shield film portion 14 is performed using the one-dimensional heat transfer model, and the heat transfer analysis of the piston body 12 is performed using the three-dimensional heat transfer model. The analysis results are shown for the case (heat transfer analysis B). The total thickness of the first heat insulating film portion 13 and the second heat insulating film portion 14 is 2.5 mm or less.

FIG. 10(a) shows the first heat shield film portion with respect to the crank angle at a position where the distance R from the piston center (the central axis of the piston body 12) is 0.0 mm in the case of heat transfer analysis A and B. 13 shows changes in heat flux on the combustion chamber side surface at 13. FIG. FIG. 10B shows the change in the heat flux of the combustion chamber side surface of the first heat shield film portion 13 with respect to the crank angle at the position where the distance R is 3.1 mm in the cases of the heat transfer analyzes A and B. indicates FIG. 10(c) shows the change in the heat flux of the combustion chamber side surface of the first heat shield film portion 13 with respect to the crank angle at the position where the distance R is 4.2 mm in the cases of the heat transfer analyzes A and B. indicates The crank angle is 0° at the compression top dead center.

Since the radius of the second heat insulating film portion 14 is 3.1 mm, the position where the distance R is 3.1 m corresponds to the boundary position between the piston body 12 and the second heat insulating film portion 14 .

10(a) and 10(c), there is almost no difference in the analysis results between heat transfer analysis A and heat transfer analysis B, but as shown in FIG. 2 At the portion corresponding to the boundary position with the heat shield film portion 14, the difference in the analysis results between the heat transfer analysis A and the heat transfer analysis B becomes remarkable. In particular, heat transfer analysis B is more preferable than heat transfer analysis A in order to perform an accurate heat transfer analysis for this portion.

On the other hand, if the heat transfer analysis is performed for the entire engine piston 11 using a three-dimensional heat transfer model, it is possible to perform a more accurate heat transfer analysis than in the case of heat transfer analysis B, but the calculation time is becomes quite long. When performing heat transfer analysis using a three-dimensional heat transfer model for the entire engine piston 11, depending on the number of meshes, the calculation time is 3 to 10,000 times that of heat transfer analysis B. It takes. Therefore, from the viewpoint of suppressing an increase in calculation load and ensuring calculation accuracy, heat transfer analysis of the first heat shield film portion 13 and the second heat shield film portion 14 is performed using a one-dimensional heat transfer model. It is desirable to conduct a heat transfer analysis of the piston body 12 using a three-dimensional heat transfer model.

The present invention is not limited to the above embodiments, and substitutions are possible without departing from the scope of the claims.

The above-described embodiments are merely examples, and should not be construed as limiting the scope of the present invention. The scope of the present invention is defined by the scope of claims, and all variations and modifications within the equivalent scope of the claims are within the scope of the invention.

INDUSTRIAL APPLICABILITY The present invention is useful for a heat transfer analysis apparatus that performs heat transfer analysis of a structure in a system including a heat source and a structure that receives heat from the heat source.

REFERENCE SIGNS LIST 1 heat transfer analysis device 2 controller 2a first heat transfer analysis section 2b second heat transfer analysis section 2d third heat transfer analysis section 11 engine piston (structure)
12 Piston body (second structure)
13 Heat shielding film (first heat shielding film (first structural part))

Claims (6)

A heat transfer analysis device for performing heat transfer analysis of a structure in a system including a heat source and a structure receiving heat from the heat source,
The structure includes a film-like first structural portion that receives heat from the heat source on one side in the thickness direction, and a second structural portion that is superimposed on the other side in the thickness direction of the first structural portion. and
a length of the second structural portion in a direction in which it overlaps with the first structural portion is greater than a thickness of the first structural portion;
a first heat transfer analysis unit that uses a one-dimensional heat transfer model to analyze heat transfer in the thickness direction of the first structural unit;
a second heat transfer analysis unit that uses a two-dimensional or three-dimensional heat transfer model to perform heat transfer analysis in two or three directions including the overlapping direction of the second structural unit. Characteristic heat transfer analysis equipment. In the heat transfer analysis device according to claim 1,
The first heat transfer analysis section performs heat transfer analysis in the thickness direction of the first structural section using a one-dimensional heat transfer model only when the thickness of the first structural section is equal to or less than a predetermined threshold. On the other hand, when the thickness of the first structural portion is greater than the predetermined threshold value, a two-dimensional or three-dimensional heat transfer model is used to estimate the heat transfer in two or three directions including the thickness direction of the first structural portion. A heat transfer analysis device configured to perform heat analysis. In the heat transfer analysis device according to claim 2,
The structure is an engine piston,
The second structural portion is a piston body,
The first structural portion is a first film portion formed on the crown surface of the piston body,
The first film portion is a film portion having a thermal conductivity set lower than that of the piston body and a volumetric specific heat set lower than the volumetric specific heat of the piston body,
The second heat transfer analysis unit is configured to perform heat transfer analysis in three directions including the overlapping direction of the piston body using a three-dimensional heat transfer model. analysis equipment. In the heat transfer analysis device according to claim 3,
Between the central portion of the crown surface of the piston body and the first film portion, there is provided a second film whose surfaces on one side and the other side in the thickness direction are in contact with the first film portion and the piston body, respectively. Department is established,
the second film portion is a film portion having a thermal conductivity set lower than that of the piston body and a volumetric specific heat set larger than the volumetric specific heat of the piston body;
further comprising a third heat transfer analysis unit that performs heat transfer analysis of the second film,
When the total thickness of the first film portion and the second film portion is equal to or less than the predetermined threshold value, the third heat transfer analysis section uses a one-dimensional heat transfer model to On the other hand, when the total thickness is greater than the predetermined threshold value, a three-dimensional heat transfer model is used to analyze the thickness direction of the second film portion. A heat transfer analysis device configured to perform heat transfer analysis in three directions including: In the heat transfer analysis device according to any one of claims 2 to 4,
The heat transfer analysis apparatus, wherein the predetermined threshold is set to 2.5 mm. In the heat transfer analysis device according to claim 1 or 2,
The second heat transfer analysis section is configured to perform heat transfer analysis in three directions including the overlapping direction of the second structural section using a three-dimensional heat transfer model. Heat transfer analyzer.

Images