A double-gradient cavity die head for preventing sedimentation of hydrogen fuel cells and a coating method thereof

Abstract

The present invention relates to a double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell and a coating method thereof, and belongs to the technical field of coating dies. The double-gradient cavity die head comprises an upper die head and a lower die head, and a cavity for accommodating the slurry is provided on the surface of the upper die head facing the slurry coating channel, and the depth and width of the cavity gradually decrease from the middle to both sides, and a feed hole is provided on the upper die head, and the feed hole is located at the center of the cavity. The coating method comprises the steps of tilting the facing surfaces of the upper die head and the lower die head downward by 0 to 45 degrees from the back to the lip, discharging the gas of the slurry in the cavity, closing the exhaust valve, and starting coating. The cavity structure of the present invention greatly slows down the sedimentation rate of the slurry and improves the lateral consistency of the coating.

Description

Technical Field

[0001] The invention relates to a double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell and a coating method thereof, belonging to the technical field of coating die heads. Background Art

[0002] According to the characteristics of hydrogen fuel cell slurry, the slurry is mainly composed of carbon powder slurry & catalyst (trace platinum or iridium oxide) and other solvents. Because the carbon powder slurry is doped with precious metals, the sedimentation rate of the slurry is very amazing. Generally, the particles in the slurry will settle within 30 minutes or one hour. The slurry is an unstable suspension. As the slurry flows to the outlet, the particles will also sink due to their own gravity. In particular, the slower flow rate on both sides of the cavity is quite obvious, resulting in poor lateral consistency of the coating. Summary of the invention

[0003] In order to solve the above problems, the present invention discloses a double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell and a coating method thereof, and the specific technical scheme thereof is as follows:

[0004] A double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell comprises an upper die head, a lower die head and a gasket. The upper die head and the lower die head are closely aligned. The gasket is located in a gap between the upper die head and the lower die head. The end positions of the upper die head and the lower die head are lips. A cavity for accommodating slurry is provided on the lower surface of the upper die head. The depth and width of the cavity gradually decrease from the middle to both sides. The gap from the cavity to the lip is a slurry coating channel. A feed hole is provided on the upper die head. The feed hole is located in the center of the cavity.

[0005] Furthermore, the feed hole is parallel to the slurry coating channel.

[0006] Furthermore, the upper die head is provided with three exhaust holes, which are respectively located at the center and two ends of the cavity.

[0007] Furthermore, the exhaust hole is perpendicular to the slurry coating channel.

[0008] Furthermore, the long side / short side of the cavity is 1.2~1.8, and the depth variation is: deep cavity / shallow cavity is 1.2~1.8.

[0009] Furthermore, the upper surface of the lower die head is inclined upward from the lip to the opposite side, with an inclination angle of 0~45°, the lower surface of the upper die head is fitted with the upper surface of the lower die head, and the slurry coating channel is inclined downward by 0~45°.

[0010] Furthermore, the lips of the upper die head and the lower die head both extend forward with a pointed edge, and the thickness of the lips of the upper die head and the lower die head are both 0.35-1.00 mm.

[0011] Furthermore, the shape of the gasket is a "concave" shape, and the gasket surrounds both ends and the upper side of the slurry coating channel.

[0012] The coating method of the double-gradient cavity die head for preventing sedimentation of the hydrogen fuel cell comprises the following steps:

[0013] Step 1: The upper die head and the lower die head are closely aligned and connected, the lower die head is placed horizontally, the upper die head is placed on the lower die head, and they are connected and fixed on the back. The facing surface of the upper die head and the lower die head is tilted downward by 0~45° from the back to the lip.

[0014] Step 2: The foil to be coated passes in front of the lip and moves at a steady speed of 3 to 60 m / min;

[0015] Step 3: Deliver hydrogen fuel cell slurry from the feed hole toward the cavity, the hydrogen fuel cell slurry fills the cavity, and the gas of the hydrogen fuel cell slurry is released from the exhaust hole. When no gas flows out of the exhaust pipe and the liquid pressure at the feed hole is stable, it is determined that the exhaust is complete, and the valve at the end of the exhaust hole is closed;

[0016] Step 4: Adjust the knife distance between the foil to be coated and the lip to 1~2 times the wet film thickness and start coating.

[0017] The beneficial effects of the present invention are:

[0018] The present invention adopts a structure in which the cavity is placed in the upper mold, and the internal structure of the cavity is deep in the middle and shallow on both sides, wide in the middle and narrow on both sides. Through multiple cavity optimizations, the cavity profile of the present invention is finally obtained. At the same time, according to the simulation results, it can be seen that the optimized cavity greatly slows down the sedimentation rate of the slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention,

[0020] Figure 2 This is a side view of the present invention (taking the slurry coating channel tilted downward by 22.43° as an example),

[0021] Figure 3 is a perspective structural diagram of the present invention,

[0022] Figure 4 is a slurry distribution diagram of the simulation test of the present invention,

[0023] Figure 5 is a pressure distribution diagram of the slurry coating channel of the test embodiment of the present invention when the angle is 0°,

[0024] Figure 6is a pressure distribution diagram of the slurry coating channel of the test embodiment of the present invention when the angle is 22.43°,

[0025] Figure 7 is a pressure distribution diagram of the slurry coating channel of the test embodiment of the present invention when the angle is 45°,

[0026] Figure 8 is a slurry streamline diagram when the slurry coating channel of the test embodiment of the present invention is 0°,

[0027] Fig. 9 is a slurry streamline diagram when the slurry coating channel of the test embodiment of the present invention is 22.43°,

[0028] Fig.10 is a slurry streamline diagram when the slurry coating channel of the test embodiment of the present invention is 45°,

[0029] Fig.11 is a distribution diagram of slurry particle concentration on the bottom surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 0°,

[0030] Fig.12 is a distribution diagram of slurry particle concentration on the bottom surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 22.43°,

[0031] Fig.13 is a distribution diagram of slurry particle concentration on the bottom surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 45 degrees,

[0032] Fig.14 is a distribution diagram of slurry particle concentration on the top surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 0°,

[0033] Fig.15 is a distribution diagram of slurry particle concentration on the top surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 22.43°,

[0034] Fig.16 is a distribution diagram of slurry particle concentration on the top surface of the cavity when the slurry coating channel of the test embodiment of the present invention is 45°,

[0035] Fig.17 is the lateral consistency analysis in the slurry coating channel of the test embodiment of the present invention, that is, the lateral slurry flow rate,

[0036] Fig.18 is the lateral consistency analysis of the slurry coating channel outlet of the test embodiment of the present invention, that is, the slurry flow rate at the lip,

[0037] List of reference numerals: 1—connecting piece, 2—upper die head, 3—end exhaust hole, 4—cavity, 5—middle exhaust hole, 6—feed hole, 7—pad, 8—lower die head, 9—upper die head lip, 10—lower die head lip, 11—gasket. DETAILED DESCRIPTION

[0038] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0039] Combined with Figure 1-3 The structure of the present invention is introduced. The double-gradient cavity die head for preventing sedimentation of hydrogen fuel cells comprises a connector 1, an upper die head 2, an end exhaust hole 3, a cavity 4, a middle exhaust hole 5, a feed hole 6, a pad 7, a lower die head 8, an upper die head lip 9, a lower die head lip 10 and a gasket 11. The upper die head 2 and the lower die head 8 are connected by two connectors 1, the upper die head 2 and the lower die head 8 are closely aligned, the gasket 11 is located in the gap between the upper die head 2 and the lower die head 8, the upper die head 2 and the lower die head 8 are located at the end position of the slurry coating channel as a lip, the lip of the upper die head 2 is called the upper die head lip 9, and the lip of the lower die head 8 is called the lower die head lip 10. A cavity 4 for accommodating the slurry is provided on the surface of the upper die head facing the slurry coating channel, and the depth and width of the cavity 4 gradually decrease from the middle to the two sides. The gap between the cavity 4 and the lip is the slurry coating channel, and a feed hole 6 is provided on the upper die head, and the feed hole 6 is located at the center of the cavity 4. The feed hole 6 is connected to the feed pipeline, and the feed pipeline is provided with a feed valve for controlling the switch and flow of the slurry.

[0040] Combination Figure 1 It can be seen that the shape of the gasket 11 is a "concave" shape, and the gasket surrounds the two ends and the upper side of the slurry coating channel, that is, the gasket 11 is attached to the area of ​​the lower surface of the upper die head except the cavity and the slurry coating channel. The function of the gasket 11 is to seal the upper die head and the lower die head, and secondly, to allow a gap to exist in the area without the gasket between the upper die head and the lower die head through the thickness of the gasket 11, that is, to form a slurry coating channel.

[0041] The feed hole 6 is parallel to the slurry coating channel. The parallel slurry flow direction is conducive to the slurry flowing evenly toward the slurry coating channel, which is conducive to the lateral uniformity of coating.

[0042] The upper die head 2 is also provided with three exhaust holes, which are located at the center and both ends of the cavity respectively. The exhaust holes located at the center are called middle exhaust holes 5, and the exhaust holes located at both ends are called end exhaust holes 3. The function of the exhaust holes is to discharge the bubbles in the slurry in the cavity 4 when starting, so as to ensure that the coating layer is uniform in thickness and has no aeration points. An exhaust valve is provided on the exhaust hole. When there are no bubbles in the slurry discharged from the exhaust hole, the exhaust valve is closed, and the slurry is sprayed from the slurry coating channel through the lip position onto the foil to be coated.

[0043] The vent hole is perpendicular to the slurry coating channel. This vertical angle allows the slurry to be discharged from the vent hole after filling the entire cavity 4, ensuring that the slurry in the cavity 4 is in a full state.

[0044] The long side / short side of the cavity is 1.2~1.8, and the depth variation is: deep cavity / shallow cavity = 1.2~1.8. The upper surface of the lower die head is tilted upward from the lip to the opposite side, with an inclination angle of 0~45°. The lower surface of the upper die head fits the upper surface of the lower die head, and the slurry coating channel is tilted downward by 0~45°. The lip thickness of the upper die head and the lower die head is 0.35~1.00mm. This structure is selected after multiple optimizations, and it has been verified through experiments that the structural proportion and lateral uniformity of the coating are the best.

[0045] The lips of the upper die 2 and the lower die 8 both extend forward with a pointed edge. The lips with pointed edges are conducive to the spraying of the slurry and are convenient for adjusting the distance between the lips and the foil to be coated.

[0046] A cushion block 7 is provided below the lower die head 8 , and the height of the lips of the upper die head 2 and the lower die head 8 from the installation table or the ground can be adjusted by changing the thickness of the cushion block 7 .

[0047] The present invention takes the inlet flow rate in the slurry feed hole as 3.8 mL / s, the coating speed as 6 m / min, the thickness of the gasket as 0.1 mm, and the knife gap GAP (the distance from the lip to the foil) as 100 μm as an example to simulate and test the coating process of the slurry coating channel at different inclination angles.

[0048] See also Figure 4 , Figure 4 The red area in the figure is the slurry area. After the slurry fills the cavity, the gas in the slurry is discharged, and the coating speed of the slurry is stabilized, the subsequent pressure distribution, slurry streamlines, and particle concentration distribution simulations are performed.

[0049] The coating process parameters of the simulation state are shown in Table 1 below.

[0050] Table 1

[0051]

[0052] The coating liquid in Table 1 is the slurry.

[0053] See also Figure 5-7 , when the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43°, and 45°, respectively, the pressure distribution of the slurry in the cavity and the slurry coating channel is not much different.

[0054] See also Figure 8-10, when the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43°, and 45°, respectively, the slurry streamlines in the cavity and the slurry coating channel are not much different.

[0055] See also Figure 11-13 When the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43° and 45° respectively, due to the effect of gravity, the precious metal particles contained in the slurry appear in low-concentration areas near the upper boundary on both sides of the cavity, and the concentration change in the low-concentration area becomes smaller and smaller in the order of 0°, 22.43° and 45°.

[0056] See also Figure 14-16 , when the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43°, and 45°, respectively, the smaller the angle, the more serious the particle aggregation.

[0057] See also Fig.17 When the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43° and 45° respectively, the smaller the angle, the more obvious the "drum edge" phenomenon of the outlet particle distribution, which is more likely to lead to an increase in the precious metal content of the edge coating.

[0058] See also Fig.18 , when the inclination angles of the feed hole and the slurry coating channel to the horizontal plane are 0°, 22.43°, and 45°, respectively, the outlet flow rate is basically the same.

[0059] The above simulation test results are summarized in Table 2.

[0060] Fig.17 and Fig.18 The horizontal axis represents the distribution from one end of the lip to the other end, and X represents the distance from 0 to the other end with one end as the 0 point.

[0061] Table 2

[0062]

[0063] Based on the above comprehensive evaluation, this patent selects an example in which the inclination angle of the feed hole and the slurry coating channel to the horizontal plane is 0~45° as the optimized structure of the present invention.

[0064] The coating process of the present invention is described below:

[0065] Step 1: The upper die head and the lower die head are closely aligned and connected, the lower die head is placed horizontally, the upper die head is placed on the lower die head, and they are connected and fixed on the back. The facing surface of the upper die head and the lower die head is tilted downward by 0~45° from the back to the lip.

[0066] Step 2: The foil to be coated passes in front of the lip and moves at a steady speed of 3 to 60 m / min;

[0067] Step 3: Deliver hydrogen fuel cell slurry from the feed hole toward the cavity, the hydrogen fuel cell slurry fills the cavity, and the gas of the hydrogen fuel cell slurry is released from the exhaust hole. When no gas flows out of the exhaust pipe and the liquid pressure at the feed hole is stable, it is determined that the exhaust is complete, and the valve at the end of the exhaust hole is closed;

[0068] Step 4: Adjust the knife distance between the foil to be coated and the lip to 1~2 times the wet film thickness and start coating.

[0069] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0070] The meaning of "and / or" described in this application means that the situations where each exists alone or both exist at the same time are included.

[0071] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0072] With the above-mentioned ideal embodiments of the present invention as inspiration, through the above-mentioned description content, relevant personnel can make various changes and modifications without departing from the scope of the technical idea of ​​the present invention.

Claims

1. A double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell, comprising an upper die head, a lower die head and a gasket, wherein the upper die head and the lower die head are closely aligned, the gasket is located in the gap between the upper die head and the lower die head, and the upper die head and the lower die head are located at the end of the slurry coating channel as a lip, characterized in that: A cavity for accommodating slurry is provided on the lower surface of the upper die head, and the depth and width of the cavity gradually decrease from the middle to the two sides, and the gap between the cavity and the lip is a slurry coating channel. A feed hole is provided on the upper die head, and the feed hole is located in the center of the cavity; The feed hole is parallel to the slurry coating channel; The upper die head is also provided with three exhaust holes, which are respectively located at the center and two ends of the cavity; The exhaust hole is perpendicular to the slurry coating channel; The long side / short side of the cavity is 1.2-1.8, and the depth variation is: deep cavity / shallow cavity is 1.2-1.8; The upper surface of the lower die head is tilted upward from the lip to the opposite side, and the tilt angle is 0-45°. The lower surface of the upper die head is in contact with the upper surface of the lower die head, and the slurry coating channel is tilted downward by 0-45°. The lips of the upper die head and the lower die head both extend forward with a pointed edge, and the thickness of the lips of the upper die head and the lower die head is 0.35-1.00 mm.

2. The double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell according to claim 1, characterized in that: The shape of the gasket is a "concave" shape, and the gasket surrounds the two ends and the upper side of the slurry coating channel.

3. A coating method for a double-gradient cavity die head for preventing sedimentation of a hydrogen fuel cell according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: The upper die head and the lower die head are closely aligned and connected, the lower die head is placed horizontally, the upper die head is placed on the lower die head, and they are connected and fixed on the back. The facing surface of the upper die head and the lower die head is tilted downward by 0~45° from the back to the lip. Step 2: The foil to be coated passes in front of the lip and moves at a steady speed of 3 to 60 m / min; Step 3: Deliver hydrogen fuel cell slurry from the feed hole toward the cavity, the hydrogen fuel cell slurry fills the cavity, and the gas of the hydrogen fuel cell slurry is released from the exhaust hole. When no gas flows out of the exhaust pipe and the liquid pressure at the feed hole is stable, it is determined that the exhaust is complete, and the valve at the end of the exhaust hole is closed; Step 4: Adjust the knife distance between the foil to be coated and the lip to 1~2 times the wet film thickness and start coating.

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