Method for measuring deposition state of soot

Abstract

To measure the deposition state of soot by nondestructive inspection without changing the material or the structure of an actual heat exchanger.SOLUTION: The method for measuring the deposition state of soot of the present invention is a method for measuring the deposition state of soot S of an EGR cooler (1) that cools exhaust gas including soot S discharged from an internal combustion engine, the method including: performing CT imaging by X-rays in a state where a substance that has different X-ray transmittance with respect to the soot S and does not chemically react with the soot S is filled in an exhaust gas passage (C) inside the EGR cooler (1) so as not to affect the deposited soot S.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for measuring soot buildup. [Background technology]

[0002] Patent Document 1 discloses an EGR cooler configured so that exhaust gas flows inside a tube to cool the exhaust gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-152713 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, fins are provided inside the tubes, and exhaust gas flows through a flow path defined by the tubes and fins.

[0005] Exhaust gas contains soot produced by combustion in an internal combustion engine, and in the development of an EGR cooler it is essential to measure how soot accumulates in the flow passages.

[0006] However, there was room for improvement in the method of non-destructive testing without changing the materials or configuration of the components that make up the EGR cooler.

[0007] The present disclosure relates to a method for non-destructively measuring the soot deposition state of a heat exchanger without changing the material or construction of the actual heat exchanger. [Means for solving the problem]

[0008] A method according to one aspect of the present invention is a method for measuring a soot accumulation state of a heat exchanger that cools exhaust gas containing soot emitted from an internal combustion engine, the method comprising the steps of: A substance that has a different X-ray transmittance than soot and does not chemically react with soot is filled into the exhaust gas flow path inside the heat exchanger so as not to affect the accumulated soot, and then CT (Computed Tomography) imaging is performed using X-rays.

[0009] According to the present invention, the state of soot accumulation can be measured by non-destructive testing without changing the material or configuration of the actual heat exchanger. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of an EGR cooler according to this embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the EGR cooler according to this embodiment. [Figure 3] FIG. 3 is a view of the EGR cooler as seen from the front. [Figure 4] FIG. 4 is a partial enlarged view of part IV in FIG. [Figure 5] FIG. 5 illustrates a measurement system for measuring soot deposition. [Figure 6] Figure 6 shows an example of a CT image of the channel filled with a suspension of barium sulfate and water. [Figure 7] FIG. 7 illustrates a CT image in which the channel is not filled with anything. [Figure 8] FIG. 8 illustrates a CT image according to this embodiment in a cross section along the direction in which the tube extends. [Figure 9] FIG. 9 illustrates a CT image taken by a method for measuring the soot accumulation state according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. For the sake of convenience, the dimensions of each component shown in the drawings may differ from the actual dimensions of each component.

[0012] Furthermore, in the description of this embodiment using Figures 1 to 3, for convenience of explanation, the "left-right direction," "front-rear direction," and "up-down direction" will be referred to as appropriate. Here, the "up-down direction" includes the "upward direction" and the "downward direction." The "front-rear direction" includes the "forward direction" and the "rearward direction." The "left-right direction" includes the "leftward direction" and the "rightward direction." The symbol U shown in Figures 1 to 3 indicates the upward direction. The symbol D indicates the downward direction. The symbol F indicates the forward direction. The symbol B indicates the rearward direction. The symbol L indicates the leftward direction. The symbol R indicates the rightward direction. Note that when the EGR cooler is installed on a vehicle, these directions do not necessarily coincide with the respective directions set for the vehicle. Furthermore, the "up-down direction" in the description of Figure 5 and subsequent figures does not necessarily coincide with the "up-down direction" shown in Figures 1 to 3.

[0013] Fig. 1 is a perspective view of an EGR cooler 1 according to this embodiment. Fig. 2 is an exploded perspective view of the EGR cooler 1 according to this embodiment. The EGR cooler 1 is an example of a heat exchanger. The EGR cooler 1 is connected to an internal combustion engine (not shown) and is configured to cool high-temperature exhaust gas sent from the internal combustion engine.

[0014] As illustrated in FIG. 1, the EGR cooler 1 includes a heat exchanger 10, a gas inlet 20 for introducing exhaust gas into the heat exchanger 10, a gas outlet 30 for discharging exhaust gas from the heat exchanger 10, a water inlet 40 for introducing cooling water into the heat exchanger 10, and a water outlet 50 for discharging cooling water from the heat exchanger 10.

[0015] High-temperature exhaust gas flows into the heat exchange section 10 through the gas inlet section 20 and is discharged rearward through the gas outlet section 30. Meanwhile, cooling water flows into the heat exchange section 10 through the water inlet section 40 and is discharged downward through the water outlet section 50. As the exhaust gas and cooling water pass through the heat exchange section 10, heat exchange occurs between the exhaust gas and the cooling water. This cools the exhaust gas. The cooled exhaust gas is sent back to the internal combustion engine.

[0016] The heat exchange section 10 includes a plurality of tubes 11 and a casing 12 .

[0017] The tube 11 is a hollow member through which exhaust gas flows. The tube 11 has a flat, generally rectangular shape in cross section. The plurality of tubes 11 are arranged at regular intervals.

[0018] The casing 12 is configured to house a plurality of arranged tubes 11. The casing 12 is a rectangular cylindrical member that is long in the front-rear direction. Any number of tubes 11 may be housed in the casing 12, but in this embodiment, eleven tubes 11 are provided.

[0019] Exhaust gas flows inside the tubes 11. Cooling water flows through a space defined inside the casing 12 and outside the tubes 11. Fins 17 are provided inside the tubes 11. The fins 17 are configured to promote heat exchange between the exhaust gas and the cooling water. Dimples 13 are provided on the outer surface of the tubes 11 to induce turbulence in the cooling water and promote heat exchange.

[0020] A front end plate 14 is attached to the opening at the front end of the casing 12. A rear end plate 15 is attached to the opening at the rear end of the casing 12. The gas inlet section 20 is attached to the casing 12 via the front end plate 14. The gas outlet section 30 is attached to the casing 12 via the rear end plate 15. The tubes 11 are attached to these front end plate 14 and rear end plate 15.

[0021] 3 is a view of the EGR cooler 1 as seen from the front. Openings 14a are formed in the front end plate 14 at a plurality of positions corresponding to the tubes 11. The tubes 11 are fitted into the openings 14a in the front end plate 14. Similar openings are also formed in the rear end plate 15. The tubes 11 are also fitted into the openings in the rear end plate 15.

[0022] The internal space of the gas inlet section 20 and the internal space of the gas outlet section 30 are in communication with each other via the tubes 11. Furthermore, the spaces between the plurality of openings 14a in the front end plate 14 and the spaces between the plurality of openings in the rear end plate 15 are closed, so that the space inside the casing 12 and outside the tubes 11 is formed as a liquid-tight space between the front end plate 14 and the rear end plate 15.

[0023] FIG. 4 is a partially enlarged view of part IV in FIG. 3. For ease of explanation, FIG. 4 shows only the tubes 11 and the fins 17. The space inside the tubes 11 is divided into multiple spaces by the fins 17. When the EGR cooler 1 is operating, the space inside the tubes 11 functions as a flow path C for exhaust gas, and soot S may gradually accumulate on the wall surfaces of the fins 17 and the inner wall surface of the tubes 11. For the design of the EGR cooler 1, it is important to measure the accumulation state of soot S.

[0024] Next, a description will be given of a method for measuring the deposition state of soot S according to this embodiment. Fig. 5 illustrates a measurement system 100 for measuring the deposition state of soot S.

[0025] The measurement system 100 includes a suspension tank 110 , a pipe 120 , an X-ray irradiation device 130 , and an X-ray detection device 140 .

[0026] The suspension tank 110 is configured to be able to contain a suspension of water and a substance that does not chemically react with the soot S.

[0027] The substance that does not chemically react with soot S is a substance that has a different X-ray transmittance than soot S. In this embodiment, barium sulfate is used as the substance that does not chemically react with soot S. That is, the liquid contained in the suspension tank 110 is a suspension of barium sulfate and water.

[0028] A pipe 120 is configured to supply the suspension from the suspension tank 110 to the inside of the tubes 11 of the EGR cooler 1 .

[0029] The X-ray irradiator 130 is configured to irradiate X-rays so that they pass through the EGR cooler 1. The X-ray detector 140 is configured to receive the X-rays that have passed through the EGR cooler 1.

[0030] The method for measuring the deposition state of soot S includes filling the exhaust gas flow path C inside the EGR cooler 1 with a substance that does not chemically react with soot S so as not to affect the deposited soot S, as illustrated in Fig. 4. "Affecting the deposited soot" means that the soot S adhering to the fins 17 is excessively removed or dissolved.

[0031] In this embodiment, the air in the flow path C is replaced with the suspension sufficiently slowly to fill it with a substance that does not chemically react with the soot S so as not to affect the accumulated soot S. This makes it difficult for the soot S adhering to the fins 17 to fall off.

[0032] The method for measuring the deposition state of soot S includes performing X-ray CT imaging with the flow passage C filled with a substance that does not chemically react with soot S. A CT image of any cross section of the EGR cooler 1 can be obtained by CT imaging. Here, the substance that does not chemically react with soot S has a different X-ray transmittance than soot S, so that soot S and the substance that does not chemically react with soot S are displayed with different brightnesses in the CT image. This makes it possible to distinguish between areas with soot S and areas without soot S.

[0033] When designing an EGR cooler, it is important to know how soot accumulates. For this reason, two main methods have been used to measure the state of soot accumulation in EGR coolers: destructive testing and non-destructive testing.

[0034] One example of a destructive testing method is to actually cut an EGR cooler at a certain cross section and measure the deposition state. This method has the advantage that it can measure an EGR cooler that is actually installed in a vehicle without changing the material or configuration of the EGR cooler. However, since destructive testing requires cutting the EGR cooler once, there is a possibility that the deposited soot will fall off due to vibration. In addition, since the EGR cooler is actually cut, there is a limit to the number of cross sections that can be measured. Furthermore, since the EGR cooler is actually cut, the EGR cooler cannot be re-installed in a vehicle after measurement.

[0035] On the other hand, one example of a non-destructive testing method is to make at least a portion of the EGR cooler transparent, allowing the flow path inside the tube to be visible from the outside and then photographing the tube. This method has the advantage that it does not require cutting the EGR cooler, and therefore cutting does not cause any changes in the soot accumulation state. However, because at least a portion of the EGR cooler is made transparent, it is necessary to use materials and configurations that are different from those of the EGR cooler actually installed in the vehicle. As a result, it is sometimes difficult to accurately determine whether the soot accumulation state will be the same in the EGR cooler actually installed in the vehicle.

[0036] As described above, both destructive and non-destructive testing methods have their own advantages and disadvantages, but a method for measuring the soot deposition state that combines the advantages of both has been desired. That is, a method for measuring the soot deposition state by non-destructive testing without changing the materials or configuration of the actual EGR cooler.

[0037] In this embodiment, X-ray CT imaging is performed in a state where the exhaust gas flow path C is filled with a substance that has a different X-ray transmittance than the soot S and does not chemically react with the soot S. Therefore, the voids in the flow path C are replaced with a substance that has a different X-ray transmittance than the soot S, and the outline of the substance can be confirmed by CT imaging. This allows the location where the soot S has accumulated in the flow path C to be measured, so the accumulation state of the soot S can be measured by non-destructive testing without changing the material or configuration of the actual EGR cooler 1.

[0038] The non-reactive substance is barium sulfate, which is suitable for CT imaging using X-rays. In addition, the non-reactive substance is a suspension of barium sulfate and water, which makes it easy to replace the voids in flow channel C with the barium sulfate suspension.

[0039] It is desirable that the suspension containing barium sulfate be aqueous, not oil-based. Since soot is generated by the combustion of fuel oil in an internal combustion engine, it tends to dissolve well in oil, but conversely, it is not highly hydrophilic. Therefore, if an aqueous suspension is used, the soot S adhering to the inside of the flow path C will be difficult to remove.

[0040] When the EGR cooler 1 is disposed as shown in FIG. 5, the tubes 11 extend in the vertical direction. That is, the EGR cooler 1 is disposed so that the flow path C is oriented in the vertical direction. The suspension of barium sulfate and water is filled into the flow path C of the EGR cooler 1 from the bottom. By filling the flow path C from the bottom, the voids in the flow path can be slowly replaced with the suspension. This makes it difficult for the soot S to fall out of the flow path C while the suspension is being filled. This allows for more accurate measurement of the deposition state of the soot S.

[0041] On the other hand, if the suspension is filled from above the EGR cooler, or if the EGR cooler 1 is installed sideways and the suspension is filled from the left and right directions, a region with a high flow velocity will be created inside the tubes 11, making it easier for the soot S to drop out of the flow paths C. For this reason, it is particularly preferable to slowly fill the suspension from below the EGR cooler 1 with the EGR cooler 1 standing upright so that the tubes 11 extend in the vertical direction.

[0042] The method for measuring the deposition state of soot S may include replacing voids inside the exhaust gas flow path C with water before filling the suspension into the exhaust gas flow path C inside the EGR cooler 1. In this case, the voids inside the flow path C are replaced with water and then filled with the suspension.

[0043] Because water has a lower viscosity than the suspension containing barium sulfate, the voids inside flow path C are easily replaced with water. In other words, by replacing the voids inside flow path C with water once, it is possible to prevent some of the voids inside flow path C from remaining as air bubbles. After that, by replacing the water with the suspension containing barium sulfate, the suspension containing barium sulfate is easily filled into every corner of the voids inside flow path C. This makes it possible to more clearly identify the contours of soot S.

[0044] (Variation) Next, a method for measuring the deposition state of soot S and a measurement system for measuring the deposition state of soot S according to a modified example will be described. As illustrated in Fig. 5, measurement system 100 may include a hopper 150. When measurement system 100 includes hopper 150, suspension tank 110 and pipe 120 may not be employed.

[0045] The hopper 150 is configured to discharge barium sulfate powder into the flow path C. That is, the substance that does not chemically react with the soot S in the method for measuring the deposition state of the soot S according to the modified example is barium sulfate powder. The barium sulfate powder also has a different X-ray transmittance from the soot S.

[0046] In the method for measuring the deposition state of soot S according to the modified example, a substance that has a different X-ray transmittance than soot S and does not chemically react with soot S is filled into the exhaust gas flow path C, and X-ray CT imaging is performed. As a result, the voids in the flow path C are replaced with a substance that has a different X-ray transmittance than soot S, and the outline of this substance can be confirmed by CT imaging. This allows the location where soot S is deposited in the flow path C to be measured, so the deposition state of soot S can be measured by non-destructive testing without changing the material or configuration of the actual EGR cooler 1.

[0047] (Measurement result 1) Next, CT images taken using the method for measuring the deposition state of soot S according to this embodiment are shown. Fig. 6 shows an example of a CT image in a state where a suspension of barium sulfate and water is filled into the flow path C. On the other hand, Fig. 7 shows an example of a CT image in a state where nothing is filled into the flow path C.

[0048] In FIG. 6, the gray portion A1 indicates a portion filled with a suspension of barium sulfate and water. In other words, the gray portion A1 is a void portion in the flow path C. The black portion B1 indicates a portion not filled with the suspension of barium sulfate and water. In other words, the black portion B1 is a portion in the flow path C where soot S has accumulated. As illustrated in FIG. 6, barium sulfate and soot S are depicted with different intensities in the CT image, so the boundary between the void portion in the flow path C and the portion in the flow path C where soot S has accumulated can be visually recognized.

[0049] 7, it is not possible to distinguish between the gaps in the flow path C and the areas where the soot S is deposited in the flow path C. This demonstrates that the method for measuring the deposition state of the soot S in this embodiment can measure the deposition state of the soot S.

[0050] Fig. 8 illustrates a CT image according to this embodiment of a cross section along the tube extension direction. By changing the arrangement of the EGR cooler 1 or the arrangement of the X-ray irradiation device 130 and the X-ray detection device 140 from the arrangement illustrated in Fig. 5, a CT image of a cross section along the tube extension direction can be obtained. In this case, too, the boundary between the void portion in the flow path C and the portion in the flow path C where soot S has accumulated can be visually recognized in the CT image.

[0051] (Measurement result 2) FIG. 9 illustrates a CT image captured using a method for measuring the deposition state of soot S according to a modified example. As illustrated in FIG. 9, even when the flow path is filled with barium sulfate powder, it is possible to distinguish between the void portion in the flow path C and the portion in the flow path C where soot S has deposited. However, the barium sulfate powder is not necessarily filled uniformly, and air may be mixed in between the clumps of barium sulfate powder. For this reason, when the suspension is filled, it is easier to visually recognize the boundary between the void portion in the flow path C and the portion in the flow path C where soot S has deposited.

[0052] The present invention has been described above based on the embodiments. Each of the above embodiments is an example of the present disclosure, and the present invention is not limited to the above-described embodiments and can be freely modified, improved, etc. as appropriate. In addition, the material, shape, dimensions, numerical values, form, number, location, etc. of each component in the above-described embodiments are arbitrary as long as they enable the present invention to be implemented, and are not limited thereto.

[0053] The EGR cooler 1 according to this embodiment is a so-called counterflow type EGR cooler in which the cooling water flows in the opposite direction to the exhaust gas flow in the heat exchanger 10. However, a so-called parallel flow type EGR cooler in which the cooling water flows in the opposite direction to the exhaust gas flow in the heat exchanger 10 may also be employed.

[0054] The configurations listed below also form part of this disclosure. (1): A method for measuring a soot accumulation state of a heat exchanger that cools soot-containing exhaust gas emitted from an internal combustion engine, comprising: A method for measuring the state of soot deposition, in which a substance that has a different X-ray transmittance than soot and does not chemically react with soot is filled into the exhaust gas flow path inside the heat exchanger so as not to affect the accumulated soot, and then X-ray CT imaging is performed. (2): The substance is barium sulfate. (1) A method for measuring the state of soot deposition. (3): The material is a suspension of barium sulfate and water. (1) A method for measuring the soot deposition state described above. (4): The heat exchanger is arranged so that the flow path is oriented along the vertical direction, The suspension is filled from the lower part of the flow path of the heat exchanger. (3) A method for measuring the soot deposition state described above. (5): The voids inside the flow path are filled with the suspension after being replaced with water. A method for measuring the soot deposition state according to (3) or (4). (6): The substance is barium sulfate powder. (2) A method for measuring the soot deposition state described above. (7): The heat exchanger is an EGR cooler. A method for measuring the state of soot deposition according to any one of (1) to (6). [Explanation of symbols]

[0055] 1 EGR cooler 10 Heat exchange section 11 tubes 12 Casing 13 Dimples 14 Front end plate 14a aperture 15 Rear end plate 17 Finn 20 Gas inlet 30 Gas outlet 40 Water inlet 50 Water outlet 100 Measurement System 110 Suspension tank 120 Pipe 130 X-ray irradiation equipment 140 X-ray detection device 150 Hopper A1 part B1 part C flow path S coal

Claims

1. A method for measuring a soot accumulation state of a heat exchanger that cools soot-containing exhaust gas emitted from an internal combustion engine, comprising: A method for measuring the state of soot accumulation, in which a substance that has a different X-ray transmittance than soot and does not chemically react with soot is filled into the exhaust gas flow path inside the heat exchanger so as not to affect the accumulated soot, and then X-ray CT imaging is performed.

2. The substance is barium sulfate. The method for measuring soot deposition according to claim 1.

3. The material is a suspension of barium sulfate and water. The method for measuring soot accumulation according to claim 1.

4. The heat exchanger is arranged so that the flow path is oriented along the vertical direction, The suspension is filled from the lower part of the flow path of the heat exchanger. The method for measuring soot accumulation according to claim 3.

5. The voids inside the flow path are filled with the suspension after being replaced with water. The method for measuring the soot deposition state according to claim 3 or 4.

6. The substance is barium sulfate powder. The method for measuring soot accumulation according to claim 2.

7. The heat exchanger is an EGR cooler. The method for measuring soot accumulation according to claim 1.

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