The present invention relates to a structure providing countermeasures against condensation of moisture in exhaust gas with respect to a noise eliminator installed in an exhaust system of fuel cell.
In fuel cells, a power generating reaction between fuel gas supplied to the anode electrode and oxidizing gas supplied to the cathode electrode occurs in an electrolyte, in conjunction with moisture is produced. The produced moisture is discharged as fuel cell exhaust gas, along with unused fuel gas and oxidizing gas, through an exhaust system connected to the fuel cell. In such an exhaust system, the gas stream may produce a sound of a relatively high frequency, on the order of 500 Hz to 2000 Hz. In order to reduce the noise produced by the gas stream, the exhaust system of a fuel cell vehicle or the like is typically equipped with a sound absorption type noise eliminator whose interior is packed with a sound absorbing material (noise elimination material) such as glass wool.
One example of a noise eliminator of this type is that having the cross-sectional structure illustrated in
Meanwhile, fuel cell exhaust gases contain a large amount of moisture produced by the reaction of hydrogen and oxygen. This moisture may condense in the exhaust system upstream to form liquid water which flows into the noise eliminator, or the moisture may condense in the interior of the noise eliminator. As a result, water may accumulate in the vertical lower part (hereinafter referred to as the bottom part) of the noise eliminator. When this happens, because the sound absorbing material filled in the bottom part of the noise eliminator absorbs and holds the water (“contains water”), a specified sound absorption performance cannot be achieved, and, thus, noise elimination performance is impaired.
Means of addressing this problem have been proposed in the conventional art, such as, for example, the noise eliminator 120 proposed in Japanese Patent Laid-Open Publication No. 2002-206413. As illustrated in
However, in the noise eliminator of Japanese Patent Laid-Open Publication No. 2002-206413, the water flowing from the exhaust system upstream into the noise eliminator or the water, contained in exhaust gas, and condensing in the interior of the noise eliminator can cause a water film to be produced in the inner pipe or sound transmission holes. When a water film is produced in the sound transmission holes, much of the sound energy in the inner pipe or the guiding pipe is not discharged through the sound transmission holes to the sound absorbing chamber and expansion chamber, impairing the noise elimination performance of the noise eliminator. Thus, there has been a need for a tangible approach for suppressing formation of a water film in the sound transmission holes.
The present invention provides a noise eliminator allowing suppression of formation of a water film in sound transmission holes. A noise eliminator for a fuel cell according to the present invention includes an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe. The shape of the sound transmission holes is configured so that no liquid film is formed in the holes. Also, the shape of the sound transmission hole can be construed to have a function of reducing liquid surface tension in the hole.
The noise eliminator for a fuel cell according to the present invention has the following configurations.
(1) In one configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein the sound transmission hole has an inner diameter of 3 mm or longer and a depth of 1.2 mm or shorter.
Here, the peripheral part of the sound transmission hole in the inner pipe is preferably formed thinner in wall thickness than the other part thereof.
Also, a rib reinforcing the inner pipe is preferably formed between the sound transmission holes.
(2) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein the sound transmission hole is formed in the shape of an oval having a longitudinal axis along the axis direction of the inner pipe.
(3) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein there is formed a groove connecting the adjoining sound transmission holes.
(4) In still another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein the inner wall of the sound transmission hole is formed with a saw-tooth shape.
(5) In yet another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein a water repellant layer is formed in the inner wall of the sound transmission hole.
(6) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein a sound absorbing material is filled in the inner side of the inner wall of the sound transmission hole.
(7) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein the inner pipe is provided with a drift member drifting an exhaust gas stream so that the exhaust gas stream is prevented from directly impacting the sound transmission hole.
Here, the drift member is preferably a louver protruding in a manner inclined from an upstream end of the sound transmission hole to a downstream direction in the inner-pipe inner wall.
Also, the drift member may be arranged in the inner wall of an upstream portion of the inner pipe, being preferably a stream guide plate which guides exhaust gas to an area where no sound transmission hole is formed.
(8) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including a swirling stream generation member for generating a swirling stream along the inner pipe inner wall, the member being disposed upstream in the inner pipe.
(9) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein a vortex generation member generating a vortex in the vicinity of the inner-pipe inner wall is arranged in the inner pipe.
(10) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including stream guide means for causing a part of exhaust gas flowing into the inner pipe to flow out from inside the inner pipe through the upstream-side sound transmission holes to the sound absorbing chamber, wherein the exhaust gas flowing out to the sound absorbing chamber flows through the downstream-side sound transmission holes back into the inner pipe.
Here, the stream guide means may be a narrowed portion formed in the path of the inner pipe, or the stream guide means may be a duct arranged in the inner-pipe inner wall in a manner corresponding to the upstream-side sound transmission hole.
(11) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, the noise eliminator further including gas injection means for injecting gas from outside the noise eliminator directly to the sound absorbing chamber so that gas flows from the sound absorbing chamber through the sound transmission holes into the inner pipe.
(12) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an inner pipe having a plurality of sound transmission holes formed in a peripheral wall thereof and allowing exhaust gas to flow therethrough, and an outer shell, arranged to surround the inner pipe through a prescribed distance from the peripheral wall, and constituting a sound absorbing chamber with a sound absorbing material filled in a space between the outer shell and the inner pipe, wherein the sound transmission hole and a peripheral part thereof are formed in a manner projecting toward the axis center of the inner pipe.
(13) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including an outer shell allowing exhaust gas to flow therethrough, and an inner case having a plurality of through holes formed in a peripheral wall thereof and constituting a sound absorbing chamber with a sound absorbing material filled in the interior thereof, wherein the inner case is arranged over the entire stream path cross section of the outer shell so that all the exhaust gas flowing through the outer shell flows through the interior of the inner case.
(14) In another configuration, a noise eliminator for a fuel cell according to the present invention is characterized by including a shell allowing exhaust gas to flow therethrough, and a plate-shaped member partitioning the interior of the shell by a face thereof orthogonal to the direction of exhaust gas stream and having a plurality of through holes formed therein.
Embodiments of the present invention will be described in detail below with reference to the drawings.
An exhaust system of a fuel cell system in which a noise eliminator 10 of the present embodiment is used will be schematically described with reference to
The hydrogen tank 84 is joined through a fuel gas supplying path 85 to the fuel cell 82, and hydrogen gas (fuel gas) stored in the hydrogen tank 84 is supplied, after being subjected to flow rate adjustment by a regulator 90, through a control valve 92 to the fuel cell 82. The blower 86 is connected through an oxidizing gas supplying path 87 to the fuel cell 82, whereby oxidizing gas (air) is supplied to the fuel cell 82. In the fuel cell 82, the supplied hydrogen gas and air react to produce electric energy and at the same time produce moisture.
Air unused in the reaction and oxidizing gas containing moisture (water vapor) produced in the fuel cell are discharged from the fuel cell 82 through a given exhaust system. The noise eliminator 10 is disposed at the tail end of this exhaust system; the exhaust gas containing moisture, and water being the result of moisture contained in exhaust gas condensing in the interior of the preceding exhaust system relative to the noise eliminator 10 flow from the upstream end of the exhaust system upstream (the end indicated by the arrow D of
The noise eliminator according to the present embodiment is arranged in the exhaust system of the above described fuel cell system. More specifically, the noise eliminator is installed as an exhaust sound noise elimination device (muffler) for a fuel cell vehicle in the underbody (not illustrated) towards the rear of the vehicle hung by a bracket or the like.
The noise eliminator 10 according to the present embodiment will be described with reference to
The noise eliminator 10 includes, as illustrated in
The inner pipe 14 is, as illustrated in
Meanwhile, the wall thickness of the inner pipe section 22 is formed larger than the outer pipe section 20. In the inner pipe section 22, there are formed a plurality of through holes 23 in a manner corresponding to that used to form the above described sound transmission holes 18. The configuration of the through hole is designed so as not to seal the sound transmission hole 18 formed in the outer pipe section 20 when the inner pipe section 22 is installed in the outer pipe section 20. When the inner pipe section 22 having a relatively large wall thickness is inserted and welded to the outer pipe section 20, the thin-walled outer pipe section 20 is reinforced.
With the above arrangement, the inner pipe 14 can be made of synthetic resin and have a desired stiffness, and sound transmission holes 18 having an inner diameter of 3 mm or greater and a depth of 1.2 mm or less can be formed in the peripheral wall of the inner pipe 14. The word “depth” used herein refers to the length of the sound transmission hole 18 in the direction along the center axis of the sound transmission hole 18 indicated by the dashed line E in
While the inner diameter of the sound transmission hole 18 is 3 mm or larger, the depth thereof is set to a sufficiently small value of 1.2 mm or less. While there is formed a water film having a size corresponding to the inner diameter of the sound transmission hole 18, because the area of the inner wall of the sound transmission hole 18 holding the water film is small, it is not possible for the inner wall of the sound transmission hole 18 to retain the water film. Consequently, in the noise eliminator 10 of the present embodiment, even when water flowing in from the exhaust system upstream side or water condensing in the interior of the noise eliminator attaches to the sound transmission holes, formation of a water film in the sound transmission holes can be suppressed.
In the noise eliminator 10 according to the present embodiment, in order to implement the inner pipe of synthetic resin having the sound transmission holes 18 of an inner diameter of 3 mm or larger and a depth of 1.2 mm or smaller, the inner pipe section 22 reinforcing the outer pipe section 20 was inserted to the interior of the thin-walled outer pipe section 20 in which the sound transmission holes 18 are formed, but the structure of the inner pipe is not limited thereto. The inner pipe can also be implemented by various embodiments described below.
For example, as with the variation illustrated in
Meanwhile, “the other part” (indicated by reference numeral 25 in
In this way, when the peripheral part 24 of the sound transmission hole 18 is formed thinner than the other part 25, it is possible to provide in the inner pipe of synthetic resin a sound transmission hole which ensures the stiffness of the inner pipe and which has the dimensions described above which suppress formation of a water film.
Also, as with the variation illustrated in
Meanwhile, except the part in which the rib 28 is formed, the inner pipe 14c is formed thinner to have a wall thickness of 1.2 mm or less; the sound transmission hole 18 is formed in this part.
In this way, when the rib 28 is formed in the inner wall 15 of the thin-walled inner pipe, it is possible to provide in the inner pipe 14c of synthetic resin the sound transmission hole 18 of dimensions which suppress formation of a water film, while ensuring the stiffness of the inner pipe 14.
A noise eliminator 10b according to the present embodiment will be described with reference to
According to the present embodiment, the sound transmission hole 18b is oval-shaped as indicated by the solid line in
When the configuration of the sound transmission hole 18b is set in this manner, the sound transmission hole inner wall 19b cannot retain a water film in the longitudinal axis direction of the sound transmission hole 18b. Even if a water film forms in this sound transmission hole 18b, the film is easily broken in the longitudinal axis direction indicated by the arrow G. Consequently, in the noise eliminator 10b of the present embodiment, even when water flowing in from the exhaust system upstream or water condensing in the interior of the noise eliminator attaches to the sound transmission hole, formation of a water film in the sound transmission hole can be suppressed.
Also, in the sound transmission hole 18b, the longitudinal axis of the oval shape is set parallel to the axis center F of the inner pipe 14. More specifically, the sound transmission hole 18b is set so that the stream direction of exhaust gas passing through the interior of the inner pipe 14 corresponds with the direction in which the longitudinal axis of the sound transmission hole 18b is set.
Accordingly, even if a water film forms in the sound transmission hole 18b, the water film is unevenly distributed and deformed in the longitudinal axis direction by the exhaust gas stream passing through the inner pipe 14. Because thin portions of the water film are thus formed, the film tension is easily broken. Consequently, in the noise eliminator 10b of the present embodiment, a water film can be suppressed from forming in the sound transmission hole.
In the noise eliminator 10b of the present embodiment, in order to suppress a water film from forming in the sound transmission hole, the sound transmission hole was formed to have an oval shape having its longitudinal axis along the axis direction of the inner pipe 14; but the configuration of the sound transmission hole is not limited thereto.
For example, as with the variation illustrated in
When the configuration of the sound transmission hole 18c is set in this manner, it is not possible for the sound transmission hole inner wall 19c to retain a water film in the part 31 at a longer distance from the center E of the sound transmission hole 18c. Thus, even if a water film forms in the sound transmission hole 18c, the surface tension of the film is easily broken at the part 31 farther from the center E, thus enabling suppression of water film formation in the sound transmission hole.
Also, as with the variation illustrated in
When such a groove 32 is provided, even if a water film forms in these sound transmission holes 18, the water constituting a water film in the one sound transmission hole 18 is pushed through the groove 32 to the other sound transmission hole 18 by effect of exhaust gas stream passing through the interior of the inner pipe 14 or of acceleration acting on the noise eliminator 10b. For example, the water constituting a water film formed in the sound transmission hole 18d can pass, as indicated by the arrow H, through the groove 32 to the sound transmission hole 18e. Accordingly, in the one sound transmission hole 18d, the amount of water constituting a water film decreases and thus the water film tension becomes easily breakable.
Consequently, according to the noise eliminator of the present embodiment, each time the sound transmission holes 18d and 18e is subjected to effects of exhaust gas stream inside the inner pipe 14 or of acceleration, the number of sound transmission holes in which a water film forms can be reduced, thus allowing suppression of water film formation in the sound transmission holes.
A noise eliminator 10c according to the present embodiment will be described with reference to
According to the present embodiment, in the inner wall 19d of a sound transmission hole 18, as illustrated in
When the above described water repellent finish is applied and the water repellent layer 34 is formed at least in the inner wall 19d of the sound transmission hole 18, the inner wall 19d of the sound transmission hole 18 cannot hold a water film. Accordingly, in the noise eliminator 10c of the present embodiment, even when water flowing in from the exhaust system upstream or water condensing in the interior of the noise eliminator attaches to the sound transmission hole, formation of a water film in the sound transmission hole can be suppressed.
A noise eliminator 10d according to the present embodiment will be described with reference to
According to the present embodiment, a sound absorbing material 16b is, as illustrated in
According to this configuration, in the noise eliminator 10d of the present embodiment, when water flowing in from the exhaust system upstream, or water condensing in the interior of the noise eliminator 10d attaches to the sound transmission hole 18, it also naturally attaches to the projection 36 of the sound absorbing material 16b, disposed in the inner side of the sound transmission hole 18. The water attaching to the projection 36 disperses to parts other than the projection 36 of the sound absorbing material 16b by the capillary phenomenon. Consequently, the projection 36 of the sound absorbing material 16b does not continue to be all wet.
Accordingly, even if a water film forms in the sound transmission hole 18, the water constituting this water film is made to disperse to another part of the sound absorbing material 16b by the projection 36 of the sound absorbing material 16b and thus the tension of the film forming in the sound transmission hole 18 is easily broken. Consequently, in the noise eliminator 10 of the present embodiment, even when water flowing in from the exhaust system upstream or water condensing in the interior of the noise eliminator attaches to the sound transmission hole, formation of a water film in the sound transmission hole can be suppressed.
A noise eliminator 10e according to the present embodiment will be described with reference to
The inner pipe 14 is provided with a drift member drifting the exhaust gas stream so that the exhaust gas stream does not impact directly against the sound transmission hole 18. The drift member is arranged inside the inner pipe 14; because the exhaust gas stream containing moisture does not directly impact against the sound transmission hole 18, fixing of the moisture contained in the exhaust gas stream to the sound transmission hole 18 is suppressed to a great extent. In the noise eliminator 10 of the present embodiment, the drift member is arranged inside the inner pipe 14 to prevent the exhaust gas stream from impacting against the sound transmission hole 18; thus, formation of a water film in the sound transmission hole 18 can be suppressed.
According to the present embodiment, a louver 38 as illustrated in
As indicated by the arrow J in
In addition, the louver 38 is as illustrated in
In the noise eliminator 10e of the present embodiment, as the drift member drifting the exhaust gas stream to prevent the exhaust gas stream from impacting directly against the sound transmission hole 18, the louver 38 protruding from the upstream end of the sound transmission hole 18 is provided, but the drift member is not limited to this configuration.
For example, as with a variation illustrated in
The “area 39 where no sound transmission hole 18 is formed” refers to an area, downstream of the upstream end 41 of the inner pipe 14g, and excluding the area 43 (indicated by the dotted line in
In this way, the exhaust gas stream does not directly impact the “area 43 in which the sound transmission hole 18 is formed”. Consequently, very little of the moisture contained in the exhaust gas attaches to the sound transmission hole 18.
As described above, in the noise eliminator 10e of the present embodiment, the louver 38 protruding from the upstream side of the sound transmission hole 18 is arranged inside the inner pipe 14g, or the stream guide plate 40 is arranged in the upstream side end 41, and thus very little moisture attaches to the sound transmission hole 18. Consequently, formation of a water film in the sound transmission hole is suppressed.
A noise eliminator 10f according to the present embodiment will be described with reference to
According to the present embodiment, the swirling stream generation member 44 is, as illustrated in
Accordingly, in the noise eliminator 10f of the present embodiment, even if a water film forms in the sound transmission hole, the exhaust gas is pressed against the water film and thus the film tension is easily broken. Consequently, in the noise eliminator 10 of the present embodiment, formation of a water film in the sound transmission hole can be suppressed.
Here, it is also preferable that the sound transmission hole 18f is, as illustrated in
When the sound transmission hole 18f is configured in this manner, even if a water film forms in the sound transmission hole 18f, the water film is polarized and deformed in the longitudinal direction of the sound transmission hole 18f by the exhaust gas stream (swirling stream) flowing along the inner-pipe inner wall 15, and, because the film includes thin patches, the film tension is easily broken.
A noise eliminator 10g according to the present embodiment will be described with reference to
The inner pipe 14i is provided with a vortex generation member generating a vortex in the vicinity of the inner wall 15 of the inner pipe 14i. The vortex generation member produces a vortex 48 upstream of the sound transmission hole 18. The produced vortex 48 flows downstream along the inner wall of the inner pipe 14 towards the sound transmission hole 18. The turbulent flow of the vortex 48 as it reaches the sound transmission hole 18 suppresses formation of water films in the sound transmission hole 18, and, upon impact, acts to break up any films that may have formed. In the noise eliminator 10g of the present embodiment, because the inner pipe 14i is provided with the vortex generation member to produce a vortex in the vicinity of the inner-pipe inner wall 15, formation of a water film in the sound transmission hole can be suppressed.
According to the present embodiment, as the vortex generation member, a Karman vortex generation member 46 is, as illustrated in
The exhaust gas stream flowing into the inner pipe 14i from the direction indicated by the arrow D is divided into two streams (an upper stream and a lower stream indicated by the arrows M1 and M2, respectively, in
In the noise eliminator 10g of the present embodiment, the Karman vortex generation member 48 produces a vortex in the vicinity of the inner-pipe inner wall 15, but the vortex generation member is not limited to this configuration.
For example, as with the variation illustrated in
Of the exhaust gas stream flowing from a direction indicated by the arrow D into the inner pipe 14j, the flow (indicated by the arrow N in
A noise eliminator 10h according to the present embodiment will be described with reference to
The stream guide means cause a portion of the exhaust gas flowing inside the inner pipe 14 to flow out from inside the inner pipe 14 through the sound transmission hole 18g in the upstream side to the sound absorbing chamber 17. More specifically, in the sound transmission hole 18g in the upstream side, the stream guide means produce an exhaust gas stream flowing from inside the inner pipe 14 to the sound absorbing chamber. 17. The sound absorbing chamber 17 is a hermetically-closed space surrounded by the inner-pipe outer wall and outer-shell inner wall, with the exception of the sound transmission holes 18g and 18h, and the exhaust gas flowing out from the sound transmission hole 18g in the upstream side to the sound absorbing chamber 17 flows back from the sound transmission hole 18h in the downstream side into the inner pipe 14. In the sound transmission hole 18h in the downstream side, there is produced an exhaust gas stream flowing from the sound absorbing chamber 17 into the inner pipe 14.
When the stream guide means are arranged in the noise eliminator 10h, an exhaust gas stream can be produced in such a manner that a portion of the streams flows out from inside the inner pipe 14 through the sound transmission hole 18g in the upstream side to the sound absorbing chamber 17 and flows back through the sound transmission hole 18h in the downstream side into the inner pipe 14. Because the exhaust gas streams flows through both the upstream and downstream sound transmission holes 18g and 18h, formation of water films in the sound transmission holes 18g and 18h is suppressed, and any films that do form tend to be broken by the exhaust gas stream flowing through the sound transmission holes 18g and 18h. Accordingly, in the noise eliminator 10h of the present embodiment, formation of a water film in the sound transmission hole can be further suppressed.
According to the present embodiment, a narrowed section 52 as illustrated in
When exhaust gas flows in from the direction indicated by the arrow D, the pressure in the upstream side relative to the narrowed section 52 in the inner pipe 14k increase. On the other hand, downstream of the narrowed section 52 in the inner pipe 14k, the pressure becomes lower than in upstream side relative to the narrowed section 52. In this way, when the narrowed section 52 is formed in the inner pipe 14k, a pressure differential between the flow upstream and downstream of the narrowed section 52 is created, causing a portion of the exhaust gas flowing upstream of the narrowed section 52 in the inner pipe 14k to flow out from the upstream-side sound transmission hole 18 to the sound absorbing chamber 17. Further, the exhaust gas flowing out to the sound absorbing chamber 17 flows, as indicated by the arrow P in
In this way, in the noise eliminator 10h of the present embodiment, because the narrowed section 52 is arranged in the inner pipe 14k, exhaust gas streams flowing from inside the inner pipe 14k through the sound transmission hole 18g in the upstream side into the sound absorbing chamber 17, and flowing from the sound absorbing chamber 17 through the sound transmission hole 18h in the downstream side into the inner pipe 14k, are produced. Accordingly, water films rarely form in the upstream and downstream sound transmission holes 18g and 18h, and any films that do form are easily broken by the exhaust gas stream flowing through the sound transmission holes 18g and 18h.
In the noise eliminator 10h of the present embodiment, the formation of the narrowed section 52 in the inner pipe 14k allows a portion of the exhaust gas to flow out through the upstream sound transmission hole 18g into the sound absorbing chamber 17, but the stream guide means are not limited to this configuration.
For example, as with the variation illustrated in
Of the exhaust gas streams flowing from a direction indicated by the arrow D into the inner pipe 141, the stream indicated by the arrow Q in
In this manner, providing for each upstream sound transmission hole 18 a duct 54 having an upstream opening can produce the exhaust gas streams flowing through the upstream and downstream sound transmission holes 18i. As a result, formation of a water film in the sound transmission hole can be further suppressed.
A noise eliminator 10i according to the present embodiment will be described with reference to
Separately from the exhaust gas stream flowing from the upstream of the exhaust system into the inner pipe 14, the gas injection means injects gas from the outside of the noise eliminator 10i into the sound absorbing chamber 17. Because the pressure of the injected gas is greater than the pressure inside the inner pipe 14, when gas is injected into the sound absorbing chamber 17, the gas inside the sound absorbing chamber 17 flows through the sound transmission hole 18 into the inner pipe 14. In this way, a stream flowing from inside the sound absorbing chamber 17 through the sound transmission hole 18 and into the inner pipe 14 can be produced.
Consequently, water film rarely form in the sound transmission hole 18, and, even should such a film form, the stream flowing through the sound transmission hole 18 acts to break up the film. As a result, in the noise eliminator 10 according to the present embodiment, formation of water films in the sound transmission hole can be suppressed.
According to the present embodiment, a bypass stream path 60 which bypasses the fuel cell 82 and directly connects the oxidizing gas supplying path 87 and the interior of the sound absorbing chamber 17 as illustrated in
Referring to
Here, the pressure of oxidizing gas flowing in the bypass stream path 60 (the pressure of oxidizing gas injected into the sound absorbing chamber) is set higher than the pressure of exhaust gas flowing in the inner pipe 14, so the oxidizing gas flowing through the gas inlet 58 into the sound absorbing chamber 17 flows from the sound absorbing chamber 17 through the sound transmission hole 18 into the inner pipe 14.
In this way, the bypass stream path 60 directly connecting the oxidizing gas supplying path 87 outside the noise eliminator 10 and the interior of the sound absorbing chamber 17 is provided in the noise eliminator 10 of the present embodiment, such that a gas stream flowing from the sound absorbing chamber 17 through the sound transmission hole 18 into the inner pipe 14 can be formed. Accordingly, formation of a water film in the sound transmission hole can be further suppressed.
According to the present embodiment, oxidizing gas is removed from the oxidizing gas supplying path to the bypass stream path and injected into the sound absorbing chamber, but the configuration is not limited thereto. For example, it is also preferable that a gas outlet is arranged in an anode purge valve intermittently discharging anode gas (hydrogen) and is connected to the bypass stream path, whereby the anode gas is injected into the sound absorbing chamber. With this configuration, gas is intermittently supplied to the sound absorbing chamber and produces a pressure wave when injected, and any water films forming in the sound transmission hole 18 can be broken up by this pressure wave.
It is also preferable that a valve (not illustrated) which can be opened and closed instantaneously be provided in the bypass stream path 60. The instantaneous opening or closing of this valve produces a pressure wave in the oxidizing gas downstream of the valve. When this pressure wave propagates through the sound absorbing chamber 17 to the sound transmission hole 18.
It is also preferable that the adjustment valve 82b is opened or closed instantaneously. Such instantaneous opening and closing of the adjustment valve 82b produces a pressure wave as indicated by the arrow D in the exhaust gas flowing into the inner pipe 14. This pressure wave propagates from the inner pipe 14 to the sound transmission hole 18, and again acts to break up any water films forming in the sound transmission hole.
A noise eliminator 10j according to the present embodiment will be described with reference to
According to the present embodiment, the sound transmission hole 18i and its peripheral part 62 are, as illustrated in
In this manner, in the noise eliminator 10i of the present embodiment, even when a water film forms in the sound transmission hole 18i, because the sound transmission hole 18i is exposed to a relatively rapid flow, the water film is polarized towards a downstream direction and deformed, such that portions of the film are thinner and the film is, thus, easily broken or dispersed. Consequently, formation of water films in the sound transmission hole can be further suppressed.
A noise eliminator 10k according to the present embodiment will be described with reference to
The inner case 66 is as illustrated in
The inner case 66 described above is, as illustrated in
When the noise eliminator 10k is configured in this manner, all the exhaust gas flowing through the outer shell 12d flows, as indicated by the arrow W, through the through hole 18j of the inner-case wall surface 68 and the sound absorbing chamber 17 residing therein. Accordingly, in the noise eliminator 10k of the present embodiment, formation of a water film in the through hole 18j can be suppressed.
It is preferable that the configuration of the inner case 66 and outer shell 12d is set so that the area of the wall surface 68 having the through hole 18j of the inner case 66 is maximized. When the area of the wall surface 68 having the through hole 18j of the inner case 66 is maximized and the number of the through holes 18j is set accordingly, the pressure loss caused by exhaust gas flowing through the inner case 66 can be reduced.
A noise eliminator 10m according to the present embodiment will be described with reference to
The plate-shaped member 72 is a hard plate member having a substantially circular shape as illustrated in
The exhaust gas flowing in from the direction indicated by the arrow D flows, as indicated by the arrow D, through the through hole 18k of the plate-shaped member 72. The exhaust gas stream indicated by the arrow D is a turbulent flow produced upstream in the exhaust system, and this turbulent flow is rectified when the exhaust gas flows through the plurality of through holes 18k formed in the plate-shaped member 72. In this way, the turbulent flow is rectified each time it passes through the through holes 18k of each plate-shaped member, whereby the sound propagating from the exhaust system upstream to the interior of the shell 74 is silenced.
In the noise eliminator 10m of the present embodiment, the flowing—in exhaust gas is reliably directed through the through hole 18k of the plate-shaped member 72, and formation of water films in the through hole 18k is thereby suppressed. As a result, a desired noise elimination performance can be achieved without using a sound absorbing material.
As described above, the noise eliminator for a fuel cell according to the present invention is useful as a noise eliminator in an exhaust system of a fuel cell.
Number | Date | Country | Kind |
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2005-185371 | Jun 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/312841 | 6/21/2006 | WO | 00 | 11/15/2007 |