A fuel cell hedge exhaust silencer

Abstract

The present invention relates to a fuel cell counterflow exhaust muffler. The invention comprises an air passage for the flow of air; a hydrogen passage for the flow of hydrogen and separated from the air passage; a counterflow passage in communication with the air passage and the hydrogen passage respectively; wherein the air and hydrogen can flow into the counterflow passage axially symmetrically after passing through the air passage and the hydrogen passage respectively and then be discharged. The counterflow exhaust muffler can offset the radial velocity by the radial counterflow of two-phase gas flow, significantly reduce the overall flow rate of the discharged gas, limit the direction of the gas flow and reduce the collision friction with the pipe wall.

Description

Technical Field

[0001] This invention relates to the field of exhaust noise reduction technology, and in particular to a fuel cell counter-current exhaust noise reducer. Background Technology

[0002] Exhaust noise, as a significant component of engine noise, poses a considerable threat to human health. Various measures have been taken to control noise within a reasonable range, with installing an exhaust muffler being the most effective method.

[0003] Exhaust mufflers can be classified into three categories: reactive mufflers, resistive mufflers, and impedance-resistance composite mufflers. Resistive mufflers achieve noise reduction by installing sound-absorbing materials inside the muffler; however, the sound-absorbing materials are prone to corrosion, not resistant to high temperatures, and have complex structures, which has limited their widespread application. Reactive mufflers consist of simple steel structures and can effectively avoid the problems of resistive mufflers. However, reactive mufflers also have their drawbacks; their noise reduction capacity and exhaust back pressure are contradictory, making it impossible to simultaneously increase noise reduction capacity and reduce exhaust back pressure. In addition, fuel cell systems contain a certain amount of hydrogen in their exhaust gases, and stainless steel is prone to hydrogen embrittlement. Impedance-resistance composite mufflers combine the advantages and disadvantages of both types, but they are also not the best choice for fuel cell mufflers. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of existing fuel cell mufflers, such as easy corrosion of materials, complex structure, contradiction between noise reduction and exhaust back pressure, and incomplete applicability to fuel cell systems.

[0005] To solve the above-mentioned technical problems, the present invention provides a fuel cell counter-current exhaust muffler, comprising:

[0006] Air passage, used for air circulation;

[0007] A hydrogen passage for the flow of hydrogen and separated from the air passage;

[0008] The counter-current channel is connected to both the air channel and the hydrogen channel;

[0009] Air and hydrogen flow axially and symmetrically into the counterflow channel after passing through the air channel and the hydrogen channel, respectively, and then exit.

[0010] In one embodiment of the present invention, the pressure and flow rate of the air flowing into the air channel and the pressure and flow rate of the hydrogen flowing into the hydrogen channel are kept consistent.

[0011] In one embodiment of the present invention, a first pressure regulator is installed at the air inlet of the air channel, and a second pressure regulator is installed at the air inlet of the hydrogen channel. The first pressure regulator and the second pressure regulator are used to adjust the pressure and flow rate of the air and hydrogen, respectively.

[0012] In one embodiment of the present invention, the air passage and the hydrogen passage are respectively symmetrically arranged along the central axis of the counter-current passage.

[0013] In one embodiment of the invention, at least a portion of the counter-current channel forms a common sidewall with the air channel and the hydrogen channel respectively, and the two common sidewalls are arranged opposite to each other.

[0014] In one embodiment of the present invention, the two common sidewalls are respectively provided with anti-flush holes symmetrically arranged along the central axis of the anti-flush channel, and the central axes of the two symmetrically arranged anti-flush holes are on the same straight line or at an angle.

[0015] In one embodiment of the present invention, the relative distance between the two symmetrically arranged punch holes is equal to (2n+1)λ, where λ is the wavelength of the sound wave generated by the monopole sound source, and 2n+1 is an odd number.

[0016] In one embodiment of the present invention, the inner wall of the counter-current channel has a layer of sound-absorbing material.

[0017] In one embodiment of the present invention, the cross-sectional areas of the air passage and the hydrogen passage are respectively smaller than the cross-sectional area of ​​the counter-current passage.

[0018] In one embodiment of the invention, a housing and a tailpipe are further included, wherein the air passage and the hydrogen passage are respectively formed in the housing, and the tailpipe extends axially and communicates with the counter-current passage.

[0019] The technical solution of the present invention has the following advantages over the prior art:

[0020] The fuel cell counter-current exhaust muffler of the present invention reduces the overall flow velocity of the exhaust gas by radially opposing two-phase airflows of equal volume, thereby limiting the direction of the exhaust flow and making it mainly flow along the axial direction, thus reducing collision and friction with the pipe wall.

[0021] Meanwhile, because the punches are symmetrically distributed and have the same diameter, when gas of equal flow rate passes through, the sound waves generated by the flow rate change have consistent and opposite characteristics. Some of the sound waves cancel each other out, while the remaining sound waves are absorbed by the sound-absorbing material in the inner cavity, effectively reducing the noise of flow rate fluctuation.

[0022] By reducing airflow velocity through a counter-current mechanism, the muffler effectively reduces airflow velocity within the muffler while maintaining its silencing performance. This decreases exhaust resistance and consequently lowers the exhaust back pressure, effectively reducing turbulent noise from the collision of high-speed gas with the pipe wall. Furthermore, the larger cross-sections of the air and hydrogen channels compared to the counter-current channel increase the airflow area, effectively enlarging the pipe diameter. This increases the time and distance sound waves travel within the pipe wall, increasing energy loss and thus improving the overall performance of the muffler. Attached Figure Description

[0023] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Figure 1 This is a schematic diagram of the overall structure of the muffler of the present invention.

[0025] Figure 2 This is an enlarged schematic diagram of the punching hole of the present invention.

[0026] Figure 3 This is a schematic diagram of the radial ejection model of the punch hole in this invention.

[0027] Figure 4 This is a schematic diagram of the non-radial ejection model of the punching hole according to the present invention.

[0028] Figure 5 This is a schematic diagram of the sound waves superimposed according to the present invention.

[0029] Explanation of reference numerals on the accompanying drawings:

[0030] 1. First voltage regulator; 2. Second voltage regulator; 3. Air passage; 4. Hydrogen passage; 5. Housing; 6. Air outer cavity; 7. Hydrogen outer cavity; 8. Counterflow passage; 9. Counterflow hole; 10. Tailpipe. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] In this invention, when directions (up, down, left, right, front, and back) are described, it is only for the convenience of describing the technical solution of this invention, and does not indicate or imply that the technical features referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0033] In this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number. In the description of this invention, the terms "first" and "second" are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0034] In this invention, unless otherwise explicitly defined, the terms "setting," "installing," and "connecting" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium; a fixed connection, a detachable connection, or an integrally formed connection; a mechanical connection, an electrical connection, or a connection capable of mutual communication; or the internal connection of two components or the interaction between two components. Those skilled in the art can reasonably determine the specific meaning of the above terms in this invention based on the specific content of the technical solution.

[0035] Reference Figure 1 , Figure 2 As shown, a fuel cell counter-current exhaust muffler of the present invention includes:

[0036] Air passage 3, used for air circulation;

[0037] Hydrogen channel 4 is used for the flow of hydrogen and is separated from the air channel 3.

[0038] The counter-current channel 8 is connected to the air channel 3 and the hydrogen channel 4 respectively;

[0039] Air and hydrogen flow axially and symmetrically into the counterflow channel 8 after passing through the air channel 3 and the hydrogen channel 4, respectively, and then are discharged.

[0040] Within the fuel cell exhaust system, aerodynamic noise primarily originates from pressure pulsation and eddy current noise, which can be simplified into three categories: eddy current noise generated by friction between high-speed fluid and the pipe wall, fluctuation noise caused by pressure changes, and noise generated by free turbulent gas flow. This counter-flow exhaust muffler uses radial counter-flow of two-phase airflow to cancel out radial velocity, significantly reducing the overall velocity of the exhaust gas, limiting the airflow direction, and reducing collision and friction with the pipe wall.

[0041] In one embodiment, the pressure and flow rate of the air flowing into the air channel 3 and the pressure and flow rate of the hydrogen flowing into the hydrogen channel 4 are kept consistent. To achieve this effect, a first pressure regulator 1 is installed at the air inlet of the air channel 3, and a second pressure regulator 2 is installed at the air inlet of the hydrogen channel 4. The first pressure regulator 1 and the second pressure regulator 2 are used to adjust the pressure and flow rate of the air and hydrogen, respectively. This allows the two-phase airflows of equal volume to radially counteract each other, further optimizing the counteracting effect.

[0042] The air channel 3 and the hydrogen channel 4 are symmetrically arranged along the central axis of the counter-current channel 8. The shapes of the counter-current channel 8, the air channel 3, and the hydrogen channel 4 include circles, rectangles, etc.

[0043] To achieve radial counter-current flow of air and hydrogen, at least a portion of the counter-current flow channel 8 forms a common sidewall with both the air channel 3 and the hydrogen channel 4, with the two common sidewalls positioned opposite each other. The portion of the air channel 3 sharing the common sidewall with the counter-current flow channel 8 forms an air outer cavity 6, and the portion of the hydrogen channel 4 sharing the common sidewall with the counter-current flow channel 8 forms a hydrogen outer cavity 7. Gases from the air bypass and air exhaust of the fuel cell system enter the air outer cavity 6 from the air channel 3 after passing through the first pressure regulator 1. Hydrogen and water from the anode exhaust, after vapor-water separation, enter the hydrogen outer cavity 7 from the hydrogen channel 4 after passing through the second pressure regulator 2.

[0044] The two common sidewalls are each provided with counter-punching holes 9 symmetrically arranged along the central axis of the counter-punching channel 8. The central axes of the two symmetrically arranged counter-punching holes 9 are either on the same straight line or at an angle. Preferably, they are on the same straight line to increase counter-punching efficiency.

[0045] In one embodiment, the left inner wall of the hydrogen outer cavity 7 is a rectangular plane, with a 25mm diameter punch hole 9 every 30mm on the plane, for a total of 3 punch holes. The right inner wall of the air outer cavity 6 (relative to the left inner wall of the hydrogen outer cavity 7) is a rectangular plane, with a 25mm diameter punch hole 9 every 30mm on the plane, for a total of 3 punch holes. The punch holes 9 are round holes, and the positions and sizes of the two rows of punch holes 9 correspond to each other.

[0046] Reference Figure 3 As shown, in terms of gas flow rate analysis, assuming that the hydrogen and air have uniform pressure and flow rate after passing through the pressure regulator, the gas radially ejected from the punch hole 9 (the corresponding punch holes 9 are in a straight line) can be approximated by the following model, according to the law of conservation of momentum:

[0047] m1v1+m2v2=m1v′1+m2v′2

[0048] In this formula, m1 is the mass of hydrogen, v1 is the velocity of hydrogen before the collision, v1′ is the velocity of hydrogen after the collision, m2 is the mass of air, v2 is the velocity of air before the collision, and v2′ is the velocity of air after the collision. Both sides of the equation are vector sums.

[0049] Because of the presence of the voltage regulator, the gas mass passing through the punch hole at the same time can be controlled to be equal, the radial velocity is equal, but the direction is different, that is, m1=m2, v1=-v2. The flowing gas is regarded as a moving elastic body, and the collision of the two gases can be regarded as an elastic collision. After the collision, the radial momentum cancels each other out, the velocity returns to zero, and no eddy noise is generated.

[0050] Reference Figure 4 As shown, for the non-radial ejection model (corresponding to the angled punch 9), based on the property of vector decomposition, its velocity is decomposed into radial velocity and axial velocity, with the radial velocities canceling each other out. Most of the airflow traveling along the axial direction can minimize the frictional noise generated by impact with the pipe wall.

[0051] In acoustic cancellation analysis, according to aeroacoustic theory, the gas flow through the opposing orifice 9 can be approximated as a monopole model, and its radiated noise power W is related to the gas velocity, mass, and orifice size. According to the formula:

[0052]

[0053] In the formula, ρ is the jet gas density, D is the nozzle diameter, V is the gas velocity, ρ0 is the ambient gas density, c0 is the ambient gas sound speed, and M is the flow Mach speed.

[0054] When the gas flow rate and mass ratio are controlled to be equal by a pre-control device, and the size and shape of the punch holes 9 are exactly the same, the sound waves generated by the gas passing through the punch holes 9 can be regarded as opposing sound waves with equal frequency and wavelength. (Refer to...) Figure 5 As shown, based on the superposition principle of waves, the relative distance L between the punch holes 9 is controlled by simulation calculation to make it equal to (2n+1)λ, where λ is the wavelength of the sound wave generated by the monopole sound source and 2n+1 is an odd number. This allows the radial sound wave to disappear after superposition, and the non-radial sound wave is also weakened by the same effect, thus achieving noise reduction.

[0055] In one embodiment, the inner wall of the counter-flow channel 8 has a layer of sound-absorbing material. By radially counter-flowing two-phase airflows of equal volume, the radial velocity is offset, significantly reducing the overall velocity of the exhaust gas, limiting the airflow direction, and reducing collision and friction with the pipe wall. The counter-flow holes 9 are symmetrically distributed with consistent diameters, ensuring that the sound waves generated by flow rate changes are counter-flowing and partially absorbed by the sound-absorbing material, effectively reducing flow fluctuation noise.

[0056] In the case of gas flowing at constant pressure within a pipe, it can be regarded as a constant pressure vessel model. When gas moves from a small-volume vessel to a larger-volume vessel, a gas diffusion effect occurs, resulting in a decrease in pressure and a reduction in pressure fluctuations, thereby reducing pressure fluctuation noise.

[0057] In one embodiment, the radial dimensions of the hydrogen outer cavity 7 and the air outer cavity 6 are equal and smaller than the radial dimension of the counter-current channel 8 (i.e., the cross-sectional areas of the air channel 3 and the hydrogen channel 4 are smaller than the cross-sectional area of ​​the counter-current channel 8, respectively). Therefore, the gas pressure analysis can adopt the following model structure: constant pressure gas enters the inner cavity from the inlet pipe, which is equivalent to the pipe diameter being enlarged. The time and distance of the sound wave rebounding in the pipe wall are increased, resulting in greater energy loss, making the sound wave more easily absorbed by the sound-absorbing material in the inner cavity.

[0058] In one embodiment, the system further includes a housing 5 and a tailpipe 10. The air passage 3 and the hydrogen passage 4 are respectively formed within the housing 5. The tailpipe 10 extends axially and connects to the counterflow passage 8. The tailpipe 10 is straight and has its rear end directly connected to the atmosphere to reduce gas turbulence caused by bends.

[0059] By radially opposing two-phase airflows of equal volume, their radial velocities cancel each other out, thereby significantly reducing the overall flow velocity of the exhaust gas and limiting the direction of the exhaust flow, causing it to flow mainly along the axial direction, thus reducing collision and friction with the pipe wall.

[0060] Meanwhile, since the punch holes 9 are completely symmetrically distributed and have the same diameter, when gas of equal flow rate passes through, the sound waves generated by the flow rate change have consistent and opposite characteristics. Some of the sound waves cancel each other out, while the remaining sound waves are absorbed by the sound-absorbing material in the inner cavity, effectively reducing the noise of flow rate fluctuation.

[0061] By reducing airflow velocity through a counter-current method, the muffler effectively reduces airflow velocity within the muffler while maintaining its silencing performance. This decreases exhaust resistance and consequently reduces exhaust back pressure, effectively minimizing turbulent noise from high-speed gas collisions with the pipe wall. Furthermore, the larger cross-sections of air passage 3 and hydrogen passage 4 compared to the counter-current passage 8 increase the airflow area, effectively enlarging the pipe diameter. This increases the time and distance sound waves travel within the pipe wall, increasing energy loss and thus improving the overall performance of the muffler.

[0062] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A fuel cell counter-current exhaust muffler, characterized in that, include: Air passage (3) is used for air circulation; Hydrogen channel (4) is used for the flow of hydrogen and is separated from the air channel (3); The counter-current channel (8) is connected to the air channel (3) and the hydrogen channel (4) respectively; Air and hydrogen flow axially and symmetrically into the counterflow channel (8) and then out after passing through the air channel (3) and the hydrogen channel (4), respectively. The pressure and flow rate of the air flowing into the air channel (3) are consistent with the pressure and flow rate of the hydrogen flowing into the hydrogen channel (4); The air inlet of the air channel (3) is equipped with a first pressure regulator (1), and the air inlet of the hydrogen channel (4) is equipped with a second pressure regulator (2). The first pressure regulator (1) and the second pressure regulator (2) are used to adjust the pressure and flow rate of the air and hydrogen, respectively. At least a portion of the counter-current channel (8) forms a common sidewall with the air channel (3) and the hydrogen channel (4), and the two common sidewalls are arranged opposite to each other. The two common sidewalls are respectively distributed with anti-flush holes (9) symmetrically arranged along the central axis of the anti-flush channel (8), and the central axes of the two symmetrically arranged anti-flush holes (9) are on the same straight line or at an angle; The relative distance between the two symmetrically arranged punch holes (9) is equal to (2n+1)λ, where λ is the wavelength of the sound wave generated by the monopole sound source and 2n+1 is an odd number. This achieves the disappearance of radial sound waves after superposition, and the weakening of non-radial sound waves under the same effect, thereby achieving noise reduction. The inner wall of the counter-flow channel (8) has a layer of sound-absorbing material.

2. The fuel cell counter-current exhaust muffler according to claim 1, characterized in that, The air channel (3) and the hydrogen channel (4) are respectively symmetrically arranged along the central axis of the counter-current channel (8).

3. A fuel cell counter-current exhaust muffler according to claim 1, characterized in that, The cross-sectional areas of the air passage (3) and the hydrogen passage (4) are smaller than the cross-sectional area of ​​the counter-current passage (8).

4. A fuel cell counter-current exhaust muffler according to claim 1, characterized in that, It also includes a housing (5) and a tailpipe (10), the air passage (3) and the hydrogen passage (4) are respectively formed in the housing (5), and the tailpipe (10) extends axially and is connected to the counter-flow passage (8).

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