JP4291686B2 - Exhaust system - Google Patents

Description

  The present invention relates to an exhaust device suitable for use in a fuel cell vehicle, and more particularly, to a technique for enhancing the noise reduction effect by effectively using condensed water accumulated in a muffler.

  In recent years, fuel cell vehicles that do not generate harmful exhaust gas from the viewpoint of environmental problems have attracted attention. This fuel cell vehicle obtains a driving force by electric energy generated by a chemical reaction between hydrogen and oxygen, and sends water vapor generated by the chemical reaction to a muffler through an exhaust pipe and discharges it into the atmosphere.

  For this reason, in the exhaust device having the exhaust pipe, the muffler, etc. used in such a fuel cell vehicle, the condensed water in the exhaust tends to accumulate in the muffler more easily than the exhaust device of the vehicle using gasoline or the like as fuel. It is in.

  Thus, if a large amount of condensed water contained in the exhaust gas is accumulated in the exhaust device, if the sound absorbing material made of glass wool or the like is filled in the exhaust device, the sound absorbing material absorbs a large amount of condensed water. The occupied area (that is, volume) of the air layer that the sound absorbing material should originally have is reduced, which may significantly reduce the sound absorbing effect. In addition, even when the exhaust system is not filled with a sound absorbing material, there is a concern that it may cause problems such as reduced corrosion resistance, abnormal noise, and cracking due to condensation of condensed water. ing.

  As one method for solving such a problem, conventionally, as in Patent Document 1, for example, a drain part made of a U-shaped tube for discharging condensed water is provided in the exhaust pipe, and condensed water is discharged from this drain part. Thus, a technique has been devised that prevents condensed water from accumulating in the exhaust device and causing the sound absorbing material to absorb condensed water.

As another method, a technique has been devised in which small holes are formed in an end plate of the muffler or a baffle partitioning the inside of the muffler, and condensed water that hinders noise reduction is discharged from these small holes.
Japanese Patent Laid-Open No. 10-30813 (refer to pages 3 and 4 and FIG. 1)

  In the technique of Patent Document 1, the drain part is provided with a normally closed valve means to prevent exhaust gas from being discharged from the drain part, and a predetermined amount of condensed water accumulates in the drain part. Then, the normally closed valve means is opened and the condensed water accumulated in the drain portion is discharged.

  However, since the noise caused by the exhaust in the exhaust pipe has a property of permeating water, this noise permeates the condensed water discharged from the drain portion, and goes into the atmosphere without being silenced together with the condensed water. There is a possibility of being released.

  In such a case, there is a risk of causing in-vehicle noise and outside-vehicle noise. As a result, there is still an inadequate problem that may reduce the silencing effect necessary for the exhaust device.

  In addition, in the other methods described above, if too many small holes are provided in the end plate or the baffle, not only does the contribution of airflow noise generation in these small holes increase, but sound absorbing material is scattered from these small holes. This is not sufficient as a solution to the above problem.

  In this way, in the muffler filled with the sound absorbing material, in order to prevent the sound absorption performance from being reduced due to the accumulation of a large amount of condensed water, it is conceivable to expand the expansion chamber volume in the muffler. Since the expansion chamber volume, sound absorbing material wire diameter, density, etc. are fixed by design, the silencing effect that can be achieved in the design range and volume is limited, and it is difficult to expect further silencing effect. is there.

  Accordingly, the present invention has been made to solve the above-described problems, and provides an exhaust device that can effectively improve the silencing effect of noise caused by exhaust gas while effectively utilizing condensed water in the exhaust gas. The purpose is to do.

  The invention according to claim 1 is used in a fuel cell vehicle equipped with a fuel cell stack as a power source, and is connected to the exhaust pipe and connected to the exhaust pipe. In an exhaust system that has a muffler that reduces noise caused by exhaust and a sound absorbing chamber that is provided in the muffler and is filled with a sound absorbing material for absorbing the noise, and that exhausts the exhaust to the atmosphere. A water amount adjusting hole for collecting a predetermined amount of condensed water contained in the exhaust gas in the sound absorbing chamber is provided in an end plate or a baffle for forming the sound absorbing chamber in the muffler.

  According to a second aspect of the present invention, there is provided the exhaust system according to the first aspect, wherein the predetermined amount of the condensed water accumulated in the sound absorbing chamber is 10% to 30% of the volume of the sound absorbing chamber in the muffler. %].

  Invention of Claim 3 is the exhaust apparatus of Claim 1 or 2, Comprising: The said water amount adjustment hole of the said muffler provided the scattering prevention means which prevents the scattering of the said sound-absorbing material, It is characterized by the above-mentioned. To do.

  According to the first aspect of the present invention, the water amount adjusting hole for accumulating a predetermined amount of condensed water contained in the exhaust gas in the sound absorbing chamber is provided in the end plate or the baffle for forming the sound absorbing chamber in the muffler. Thus, the condensed water fed into the sound absorption chamber together with the exhaust is not drained until the predetermined amount is reached, and is drained from the water amount adjusting hole when the predetermined amount is exceeded. The condensed water accumulated in the sound absorbing chamber is absorbed by the sound absorbing material filled in the sound absorbing chamber, and then reaches the entire sound absorbing material by a capillary phenomenon, which functions as a sound absorbing film. And since the sound absorption film by this condensed water serves as a cushion that absorbs the high-frequency component of the noise generated along with the discharge of the exhaust, compared to the conventional exhaust device that actively discharged the condensed water, Noise can be effectively reduced, and condensed water can be effectively used for the noise reduction action. Thus, according to the present invention, the condensate in the exhaust gas can be effectively used, and the noise reduction effect caused by the exhaust gas can be significantly improved.

  According to the second aspect of the present invention, the predetermined amount of the condensed water accumulated in the sound absorbing chamber is 10% to 30% of the volume of the sound absorbing chamber in the muffler. The amount accumulated in the sound absorbing chamber is suppressed within a predetermined range, and the sound absorbing film formed on the sound absorbing material in the sound absorbing chamber by the condensed water can be optimized, so that the sound absorbing action of noise by the sound absorbing material is not degraded. This noise can be effectively reduced.

  According to the invention described in claim 3, since the scattering prevention means for preventing the scattering of the sound absorbing material is provided in the water amount adjusting hole of the muffler, it is possible to prevent the sound absorbing material from scattering from the water amount adjusting hole. . In addition, according to the present invention, since the scattering prevention means is provided in the water amount adjustment hole, it is possible to reduce the contribution rate of airflow noise caused by exhaust passing through the water amount adjustment hole.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

“Exhaust system configuration”
1 to 3 show an embodiment of an exhaust device according to the present invention, FIG. 1 is an overall configuration diagram of the exhaust device according to the present invention, and FIG. FIG. 3 is a cross-sectional view showing the AA cross section in FIG.

  In an exhaust device 1 for a fuel cell vehicle shown in FIG. 1, a waste hydrogen combustor 4 is connected to a stack portion 2 of the fuel cell via an exhaust tube 3 as an exhaust pipe. A flexible tube 5 is connected to the exhaust hydrogen combustor 4 via an exhaust tube 3, and an introduction pipe 7 of a muffler 6 is connected to the flexible tube 5 via an exhaust tube 3. At this time, connecting flanges 3a are interposed between the exhaust tubes 3 connecting the stack portion 2, the exhaust hydrogen combustor 4 and the flexible tube 5 and between the exhaust tube 3 and the introduction pipe 7 of the muffler 6, respectively. Has been.

  In the exhaust device 1, exhaust gas composed of water vapor and exhaust hydrogen generated by the chemical reaction between hydrogen and oxygen in the stack unit 2 is sent to the exhaust hydrogen combustor 4 through the exhaust tube 3. The exhaust hydrogen combustor 4 burns the exhaust hydrogen in the exhaust.

  Thereafter, the exhaust gas passes through the flexible tube 5 through the exhaust tube 3, is introduced into the muffler 6 through the introduction tube 7, and is separated into a liquid and a gas composed of condensed water in the muffler 6. The gas portion is discharged into the atmosphere via the discharge pipe 8 of the muffler 6, and a liquid portion, that is, condensed water is stored in a predetermined amount in the muffler 6. 10 (see FIG. 2 and FIG. 3) is discharged to the outside.

  Here, as shown in FIGS. 2 and 3, the muffler 6 is connected to the upstream exhaust tube 3 and is connected to the upstream exhaust tube 3 and provided with an introduction pipe 7 for introducing exhaust gas (water vapor). A plate 6a (hereinafter referred to as an end plate 6a), an end plate 6b on the other end side provided with a discharge pipe 8 for releasing the exhaust gas introduced into the muffler 6 into the atmosphere, and these end plates 6a A cylindrical shell 6c closed at both ends by an end plate 6b. The end plate 6a, the end plate 6b and the shell 6c, and the introduction pipe 7 and the discharge pipe 8 are respectively provided. They are joined by fitting welding.

  An attachment hook 9 for attaching the muffler 6 to the vehicle body outside the figure is fixed at a predetermined position on the outer periphery of the shell 6c by using a technique such as a welding method. A sound absorbing chamber 11 filled with a sound absorbing material (not shown) is formed. Further, the exhaust tube that communicates the introduction pipe 7 and the exhaust pipe 8 is provided with a plurality of discharge holes 7 a for discharging condensed water in the exhaust into the sound absorption chamber 11.

  In the case of this embodiment, the end plate 6a of the muffler 6 is provided with a water amount adjusting hole 10 for discharging condensed water exceeding a predetermined amount stored in the muffler 6, for example, in a circular shape. Further, the water amount adjusting hole 10 is provided with a lid M made of a scattering prevention mesh, foam metal, stainless steel wire or the like which is a scattering prevention means for preventing the sound absorbing material filled in the sound absorbing chamber 11 from scattering. ing. However, the lid M does not completely seal the water amount adjusting hole 10 but prevents scattering of the sound absorbing material while circulating condensed water or exhaust gas.

[Experimental considerations]
Here, the exhaust flow when the exhaust device 1 according to the present embodiment was actually used was examined.

  The condensed water sent into the sound absorbing chamber 11 together with the exhaust gas is stored in the sound absorbing chamber 11 without being drained until a predetermined amount is reached, and is discharged from the water amount adjusting hole 10 when the predetermined amount is exceeded. At this time, the amount of condensed water stored in the muffler 6 is shown in FIGS. 4A and 4B showing the relationship between the amount of condensed water absorbed by the sound absorbing material in the sound absorbing chamber 11 and the average acoustic power density. As can be seen, in the region where the frequency of noise caused by exhaust emission is 200 [Hz] to 1100 [Hz], no silencing effect is observed, but the frequency is 1100 [Hz] to 2000 [Hz]. In the region, a silencing effect of 5 [dB] to 10 [dB] can be seen when the water absorption is in the range of 200 [cc] to 500 [cc].

However, although it depends on the noise frequency to be actually suppressed, if the target noise is air flow noise, the flow rate of the exhaust gas flowing through the exhaust tube 3 is usually about 5 [m ³ ] or less, so the muffler 6 What is necessary is just to aim to mute the range of about 1100 [Hz] to 2000 [Hz], which is the peak value of the airflow noise generated in the above. In addition, the average sound power density said here represents the average value of the sound of a certain frequency range, and is a value obtained by averaging the energy level of the sound of each frequency.

In this way, 200 [cc] to 500 [cc] (that is, 10 [%] to 30 [%] of the volume of the sound absorbing chamber 11 in the muffler 6) are accumulated in the sound absorbing chamber 11 in the muffler 6. As can be seen from FIG. 5 showing the relationship between the noise frequency and the insertion loss, the amount of condensed water stored in the sound absorbing chamber 11 indicated by the solid line (hereinafter referred to as the amount of water absorption) is Compared to the case of 0 [cc], the amount of water absorption indicated by the broken line is 305 [cc], the amount of water absorption indicated by the one-dot chain line is 429 [cc], and the water absorption amount indicated by the two-dot chain line In the case of 457 [cc], it is possible to remarkably improve the silencing effect of the noise generated by the exhaust in the muffler 6.
The insertion loss referred to here is the difference between the noise level on the exhaust inlet side and the noise level on the outlet side. In FIG. 5, the plus side is the level at which the input sound level is attenuated, and the minus side. Indicates that the level of the input sound is increased.

  Further, in the present embodiment, 200 [cc] to 500 [cc] (10 [%] to 30 [%] of the volume of the sound absorbing chamber 11) of condensed water is accumulated in the sound absorbing chamber 11 in the muffler 6. Since it is only necessary to drill the water amount adjusting hole 10 in the end plate 6a, the drilling position L varies depending on the volume (shape and size) of the muffler. For example, a muffler having a length of 130 mm and a length of 150 mm In the case of No. 6, as shown in FIG. 6 showing the relationship between the water amount adjusting hole position and the amount of water stored in the muffler, the end plate 6a is drilled at a position of about 15 mm to 35 mm from the bottom of the shell 6c. It is preferable to do this.

  Further, specifically, the size of the water amount adjusting hole 10 is φ4 [mm] or less, preferably φ2 [mm] to φ3 [mm] in consideration of airflow noise caused by the exhaust gas flowing through the water amount adjusting hole 10. It is preferable to set within a range. However, this size can be appropriately changed within a range of φ4 [mm] or less according to the shape of the water amount adjusting hole 10.

  As described above, according to the exhaust device 1 of the present embodiment, the water amount adjusting hole for storing a predetermined amount of condensed water contained in the exhaust gas composed of water vapor discharged from the fuel cell vehicle in the sound absorption chamber 11. 10 is provided in the end plate 6a for forming the sound absorbing chamber 11 in the muffler 6, so that the condensed water sent into the sound absorbing chamber 11 together with the exhaust gas is the predetermined amount (that is, the sound absorbing chamber 11 in the muffler 6). If this predetermined amount is exceeded without being drained until it reaches 10 [%] to 30 [%] of the volume of the water, it is drained from the water amount adjusting hole 10.

  The condensed water accumulated in the sound absorbing chamber 11 is absorbed by the sound absorbing material filled in the sound absorbing chamber 11, and then reaches the entire sound absorbing material by a capillary phenomenon, which functions as a sound absorbing film. And since the sound absorption film by this condensed water serves as a cushion that absorbs the high-frequency component of the noise generated along with the discharge of the exhaust, compared to the conventional exhaust device that actively discharged the condensed water, Noise can be effectively reduced, and condensed water can be effectively used for the noise reduction action.

  Thus, according to the present invention, the condensate in the exhaust gas can be effectively used, and the noise reduction effect caused by the exhaust gas can be significantly improved.

  Further, according to the present embodiment, the predetermined amount of the condensed water accumulated in the sound absorbing chamber 11 is 10% to 30% of the volume of the sound absorbing chamber 11 in the muffler 6. The amount of water accumulated in the sound absorbing chamber is suppressed within a predetermined range, and the sound absorbing film formed by the condensed water soaking into the entire sound absorbing material by capillary action can be optimized. This noise can be effectively reduced without deteriorating the sound absorbing function.

  Furthermore, according to this embodiment, since the cover M for preventing the sound absorbing material from scattering is provided in the water amount adjusting hole 10 of the muffler 6, it is possible to prevent the sound absorbing material from scattering from the water amount adjusting hole 10. . In addition, according to the present invention, since the lid M is provided in the water amount adjusting hole 10, it is possible to reduce the contribution rate of the generation of airflow sound caused by the exhaust passing through the water amount adjusting hole 10. .

"Other embodiments"
Although specific embodiments to which the present invention is applied have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  For example, as shown in FIG. 7 where parts corresponding to those in FIG. 3 are assigned the same reference numerals, a baffle 20d for partitioning the sound absorbing chamber 11 is formed in a shell 20c between the end plate 20a and the end plate 20b. It is also possible to apply to the muffler 20 provided.

  In this case, since the inside of the shell 20c is partitioned by the baffle 20d, the first chamber 21 is formed on the upstream side of the sound absorbing chamber 11, so that the water amount adjusting hole 10 is formed in the baffle 20d.

  And the condensed water discharged | emitted from the sound absorption chamber 11 is discharged | emitted from the drain hole 22 provided in the end plate 20a outside after being discharged | emitted to the 1st chamber 21 through the water quantity adjustment hole 10. FIG. It has become. In this case, the position of the drain hole 22 for discharging the condensed water to the outside is not limited to the end plate 20a, but as shown in FIG. You may make it drill below the outer peripheral part periphery of the 1st chamber 21. FIG.

  Further, the introduction pipe 7 and the discharge pipe 8 do not need to be communicated by the exhaust tube and provided in a straight line. For example, as shown in FIG. The present invention can also be applied to the muffler 30 in which the pipes 8 are separated from each other and arranged in a state shifted in the flow direction of the exhaust gas. In this case, the introduction pipe 7 is fitted and welded to the end plate 30a, and the discharge pipe 8 is fitted and welded to the end plate 30b and the baffle 30d.

  In the exhaust device having the muffler 20 shown in FIG. 8, the same effect as the exhaust device 1 described above can be obtained, and the baffle 20 d is formed inside the muffler 20, thereby penetrating the muffler 20. Since the exhaust tube communicating with the introduction pipe 7 and the discharge pipe 8 provided in this manner is supported between the end plate 20a and the end plate 20b, the advantage that the exhaust tube can be stably supported can be obtained. .

  Furthermore, in the above-described embodiment, the case where the circular water amount adjusting hole 10 is provided in the end plate 6a of the muffler 6 has been described. However, the present invention is not limited to this, and the water amount adjusting hole 10 is formed in a star shape or an elliptical shape. It may be provided in a shape or a shape such as a slit 12 having a long hole extending in the circumferential direction as shown in FIG. 10, or a plurality of the water amount adjusting holes 10 may be provided.

1 is an overall configuration diagram schematically showing a configuration in an embodiment of an exhaust device according to the present invention. It is a perspective view which expands and shows the muffler in FIG. It is sectional drawing which expands and shows the muffler in FIG. It is a graph which shows the relationship between the amount of water absorption of a sound-absorbing material, and an average sound power density, (a) is a graph in case the frequency of the noise in this exhaust apparatus is the area | region of 200 [Hz] -1100 [Hz], (b ) Is a graph when the frequency of the noise is in the range of 1100 [Hz] to 2000 [Hz]. It is a graph which shows the relationship between the frequency of noise, and insertion loss. It is a graph which shows the relationship between the arrangement position of a water quantity adjustment hole, and the amount of stored water of condensed water. It is sectional drawing which shows the muffler by other embodiment. It is sectional drawing which shows the muffler by other embodiment. It is sectional drawing which shows the muffler by other embodiment. It is a top view which shows the end plate by other embodiment.

Explanation of symbols

1 ... Exhaust device 3 ... Exhaust tube (exhaust pipe)
6, 20, 30 ... Muffler 6a, 20a, 30a ... End plate 10 ... Water volume adjustment hole 11 ... Sound absorption chamber 20d, 30d ... Baffle 22, 32 ... Drainage hole L ... Drilling position

Claims (3)

An exhaust pipe (3) that is used in a fuel cell vehicle equipped with a fuel cell stack (2) as a power source and circulates exhaust gas composed of water vapor generated in the fuel cell stack (2), and the exhaust pipe (3) A muffler (6) connected to reduce the noise caused by the exhaust, and a sound absorption chamber (11) provided in the muffler (6) and filled with a sound absorbing material for absorbing the noise, In the exhaust device for discharging the exhaust to the atmosphere,
A water amount adjusting hole (10) for accumulating a predetermined amount of condensed water contained in the exhaust gas in the sound absorbing chamber (11) is an end plate for forming the sound absorbing chamber (11) in the muffler (6). 6a) or a baffle (20d). An exhaust system (1) according to claim 1,
The exhaust apparatus according to claim 1, wherein the predetermined amount of the condensed water accumulated in the sound absorbing chamber (11) is 10% to 30% of the volume of the sound absorbing chamber (11) in the muffler (6). Exhaust device (1) according to claim 1 or 2,
An exhaust device characterized in that the water amount adjusting hole (10) of the muffler (6) is provided with scattering prevention means for preventing the sound absorbing material from scattering.

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