JP2004308988A - Muffling device of combustor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffling device of a combustor having a large degree of freedom in the design of a flow passage size, capable of providing high muffling effects, and enabling a reduction in flow passage resistance in the ignition of the combustor. <P>SOLUTION: This muffling device of the combustor fitted to the exhaust tube of the combustor comprises an exhaust gas flow passage for passing, therein, the exhaust gas exhausted from the combustor, an expansion hollow formed by enlarging the cross sectional area of a part of the exhaust gas flow passage in a stepped state, and a plurality of exhaust gas inflow ports formed at the exhaust gas inflow side of the expansion hollow. By this, the high muffling effects can be provided since sonic wave with large frequency generated from the combustor can be efficiently attenuated. Also, since the sonic wave with high frequency is efficiently attenuated by complicated resonance, the length of the expansion hollow can be shortened less than that of a normal resonance type muffling device. In addition, since the plurality of exhaust gas inflow ports are formed, the exhaust gas resistance of the muffling device in the ignition of the combustion can be reduced. Accordingly, the ignition of the combustor can also be smoothly performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a muffler for silencing combustion noise in a combustor used for a water heater.
[0002]
[Prior art]
Conventionally, as a muffler for muffling a combustion noise in a combustor used for a water heater, an expansion type muffler having an expansion cavity provided in a part of an exhaust pipe, and a length of the expansion cavity in a direction of an exhaust axis. There is known a resonance type silencer configured to reduce the length of a sound wave so as to resonate a sound wave in an expansion cavity.
[0003]
As an expansion type silencer, for example, in Patent Literature 1, a plurality of disk-shaped metal plates are arranged at predetermined intervals in an exhaust pipe, and a narrow exhaust pipe is provided between a metal plate extension and an exhaust pipe inner wall. A muffler having a configuration in which a passage is formed and a wide exhaust passage is formed between metal plates is described.
[0004]
In this silencer, the exhaust gas repeats expansion and contraction between the narrow exhaust passage and the wide exhaust passage, so that the acoustic energy of the sound wave transmitted through the exhaust gas is attenuated and is silenced.
[0005]
Patent Literature 2 discloses a muffler in which a discontinuous reduced-diameter node portion and a discontinuously expanded expansion cavity portion are formed side by side in an exhaust stack.
[0006]
In this silencer, the sound wave that has entered the silencer is reduced by being reflected at a change in the cross section of the exhaust stack. First, the sound wave is partially reflected back at the boundary between the node portion and the inflated cavity portion, and a part of the sound wave travels into the inflated cavity. Sound waves traveling into the expansion cavity are irregularly reflected in the expansion cavity due to rapid expansion. Then, the sound wave is partially reflected back at the boundary between the inflated cavity portion and the node portion, and partly proceeds to the node portion. By repeating this, the sound energy is attenuated to mute the sound.
[0007]
[Patent Document 1]
Japanese Utility Model Publication No. 60-101549 [Patent Document 2]
JP-A-51-43939 [0008]
[Problems to be solved by the invention]
However, in the case of the conventional expansion type silencer, it is necessary to increase the length of the expansion cavity in order to increase the noise reduction effect, and there is a disadvantage that the muffler becomes large.
[0009]
Further, in the resonance type silencer, the ratio of the length to the diameter of the expansion cavity is determined by the frequency of resonance, so that the degree of freedom in design is limited. In particular, when the diameter of the exhaust stack is determined to be constant in design in order to optimize the exhaust resistance of the combustor, the range of the length of the expansion cavity is determined from the resonance frequency. However, if the length of the expansion cavity must be shorter than the above range due to the installation space of the muffler, a sufficient muffling effect cannot be obtained.
[0010]
Further, in a structure in which a plurality of disk-shaped metal plates are provided in the exhaust cylinder as in the muffler described in Patent Document 1, the flow path resistance of the exhaust cylinder increases. Therefore, the exhaust resistance of the combustor at the time of ignition increases, and smooth ignition cannot be performed.
[0011]
Therefore, an object of the present invention is to provide a muffler for a combustor, which has a large degree of freedom in designing a flow path size, can obtain a high muffling effect, and can also reduce the flow path resistance when the combustor is ignited. Is to do.
[0012]
[Means for Solving the Problems]
A first configuration of a muffler for a combustor according to the present invention is a muffler for a combustor attached to an exhaust stack of the combustor, wherein an exhaust passage through which exhaust discharged from the combustor passes, and the exhaust passage And a plurality of exhaust inflow ports formed on the exhaust inflow side of the expansion cavity.
[0013]
Since the expansion cavity is formed by increasing the cross-sectional area of a part of the exhaust flow passage in a step-like manner, the sound pressure of sound waves entering the expansion cavity from the combustor sharply decreases, and the acoustic energy becomes heat. Converted to energy and silenced. At this time, since a plurality of exhaust inlets are formed on the exhaust inflow side of the expansion cavity, sound waves entering the expansion cavity from each exhaust inlet are irregularly reflected inside the expansion cavity. Therefore, the phase of the sound wave is diffused and attenuated by the irregular reflection. In addition, the sound waves enter the expansion cavity from a plurality of exhaust inlets and thus interfere with each other in a complicated manner, and interfere with each other at many frequencies and are amplified (that is, an antinode is generated). Sound waves having a frequency amplified by the interference are converted to heat and attenuated by the viscosity of air. Therefore, a sound wave having a large frequency is efficiently attenuated, and a high silencing effect is obtained. In addition, since a sound wave having a large frequency is efficiently attenuated by complicated resonance, the length of the expansion cavity can be reduced as compared with a normal resonance type silencer. Therefore, the degree of freedom in designing the size of the exhaust passage is increased.
[0014]
Further, by forming a plurality of exhaust inlets, the exhaust resistance of the muffler when the combustor is ignited is reduced. Accordingly, ignition of the combustor is performed smoothly.
[0015]
In a second configuration of the muffler of the combustor according to the present invention, in the first configuration, the expansion cavity includes a cylindrical hollow muffler and a plurality of mufflers provided on an exhaust inflow side of the muffler. A disk-shaped inflow side plate having an exhaust gas inlet, and a disk-shaped outflow side plate provided on the exhaust gas outflow side of the muffler chamber and formed with an exhaust gas outlet having a diameter smaller than the inner diameter of the muffler chamber. It is characterized by having.
[0016]
With this configuration, sound waves that enter the silencing chamber from the plurality of exhaust inlets of the inflow side plate interfere with each other in the noise chamber, are converted into heat, and are silenced.
[0017]
Here, the ratio l / d of the length l of the silencing chamber to the inner diameter d of the silencing chamber can be 0.5 or less. This is because by setting 1 / d ≦ 0.5, resonance of high-frequency sound waves in the sound deadening chamber is easily caused, and the sound deadening effect is enhanced.
[0018]
In a third configuration of the muffler for a combustor according to the present invention, in the second configuration, the inflow-side plate may be configured such that a plurality of exhaust inflow ports are formed at positions symmetric with respect to the center of the inflow-side plate. Features.
[0019]
As described above, by forming the acoustic wave in a symmetrical position with respect to the exhaust gas inlet, sound waves entering the muffling chamber from each exhaust gas inlet are likely to generate a strong interference mode. On the other hand, the greater the interference, the more easily the sound energy is converted into heat energy due to the viscosity of the air. Therefore, the attenuation rate of the sound wave can be increased.
[0020]
Further, by forming the exhaust inflow ports symmetrically with respect to the center of the inflow side plate, interference of sound waves entering the muffling chamber from each exhaust inflow port is increased, and a high noise reduction effect can be obtained.
[0021]
In a fourth configuration of the muffler for a combustor according to the present invention, in the second configuration, the exhaust inlet formed in the inflow-side plate is smaller than an inner diameter of a muffler chamber provided at the center of the inflow-side plate. A central opening having a diameter and three side openings formed symmetrically with respect to the center of the inflow side plate are provided.
[0022]
According to this configuration, most of the frequency band of the sound wave generated from the combustor can be silenced.
[0023]
Here, the ratio of the diameter D of the center opening and the side opening to the inner diameter d of the silencing chamber can be D / d = 0.14 to 0.26. This is because it has been experimentally confirmed that a particularly high silencing effect can be obtained by setting this range.
[0024]
A fifth configuration of the muffler for a combustor according to the present invention is characterized in that, in any one of the first to fourth configurations, the expansion cavity is made of a sound absorbing material.
[0025]
With this configuration, sound waves propagating in the expansion cavity are absorbed and attenuated by the sound absorbing material on the side wall of the expansion cavity. Therefore, the noise reduction effect can be further increased.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram in which a muffler according to an embodiment of the present invention is incorporated in a combustor.
In FIG. 1, a burner 2 is provided at a lower portion of a combustor 1, and burns a fuel made of oil or gas in a combustion chamber 3. A heat exchanger 4 is provided at an upper portion of the combustion chamber 3. The heat exchanger 4 exchanges heat with high-temperature exhaust gas generated by combustion in the combustion chamber 3 with water. Further, a silencer 5 is attached inside the exhaust pipe above the heat exchanger 4. An exhaust port 6 is provided above the silencer 5, and exhaust gas is discharged from the exhaust port 6 to the atmosphere. Reference numeral 4a denotes a smoke tube of the heat exchanger 4, in which a baffle plate (not shown) is usually inserted so that the combustion gas is in good contact with the inner surface of the smoke tube 4a.
[0027]
2 is a perspective view of the muffler of FIG. 1, FIG. 3 is a sectional view of the muffler of FIG. 1, and FIG. 4 is a bottom view of the muffler of FIG.
[0028]
The silencer 5 is formed of rock wool, which is a sound absorbing material formed by hardening glass fiber or the like with a resin. The silencer 5 includes a cylindrical silencing cylinder portion 5a having a silencing chamber 5e formed therein, and a plurality of exhaust inlets (a central opening 5f and three side portions) provided on the exhaust inflow side of the silencing cylinder portion 5a. A disk-shaped inflow side plate 5b having an opening 5g), and a disk provided on the exhaust outflow side of the silencer cylinder portion 5a and having an exhaust outlet 5d formed at the center thereof with a diameter smaller than the inner diameter of the silencer cylinder portion 5a. Outflow side plate 5c. In this embodiment, the exhaust outlet 5d is provided at the center of the outflow side plate 5c, but it is not necessarily required to be at the center. The inflow side plate 5b has a central opening 5f having a diameter smaller than the inner diameter of the sound deadening chamber 5e in the center thereof. The side opening 3f is formed at a position symmetrical with respect to the center of the inflow side plate 5b. One is formed.
[0029]
The operation of the muffler of the combustor according to the present embodiment configured as described above will be described below.
[0030]
When the burner 2 of the combustor 1 is ignited, the pressure in the combustion chamber 3 rises sharply. Therefore, the gas in the combustion chamber passes through the heat exchanger 4 and the silencer 5 and is discharged from the exhaust port 6 to the atmosphere. At this time, since the central opening 5f and the three side openings 5g are perforated in the inflow side plate 5b of the muffler 5, the airflow resistance in the inflow side plate 5b of the muffler 5 is small. Therefore, at the time of ignition, the gas quickly passes through the silencer 5 and is discharged, so that an increase in the pressure in the combustion chamber 3 is suppressed. Therefore, a decrease in the flow rate of the air supplied to the combustion chamber 3 is suppressed, and smooth ignition can be performed.
[0031]
Next, when the burner 2 of the combustor 1 is burning, the exhaust gas is continuously exhausted from the exhaust port 6 through the heat exchanger 4 and the silencer 5 from the combustion chamber 3. At this time, in the combustion chamber 3, a combustion noise is generated with the combustion of the fuel. This combustion noise is transmitted to the muffler 5 through the exhaust passage.
[0032]
Here, since the inflow side plate 5b is provided on the exhaust inflow side of the silencer 5, a part of the sound wave of the combustion noise is reflected by the inflow side plate 5b. The sound wave that has not been reflected propagates through the central opening 5f and the three side openings 5g into the sound deadening chamber 5e.
[0033]
By the way, the sound waves that have propagated into the sound deadening room 5e from the four openings interfere with each other, and also interfere with the sound waves reflected inside the sound deadening room 5e, thereby creating a complicated mode in the sound deadening room 5e. Therefore, in the sound deadening chamber 5e, sound waves resonate over a wide frequency range, and the acoustic energy of the sound waves having the resonated frequency is attenuated due to the viscosity of the exhaust gas, and the sound is muted.
[0034]
Further, in the sound deadening chamber 5e, the sound wave is attenuated by the sound absorbing material (rock wool) on the side wall, so that the sound is further suppressed.
[0035]
On the exhaust outflow side of the silencing chamber 5e, part of the sound wave is reflected by the outflow side plate 5c, and the rest propagates from the exhaust outlet 5d to the exhaust port 6. However, most of the high-frequency sound waves propagating to the exhaust port 6 are silenced in the silencing chamber 5e, so that most of the sound waves are low-frequency sound waves, and the combustion noise leaking to the outside is effectively suppressed.
[0036]
【The invention's effect】
As described above, according to the present invention, a sound wave having a large frequency generated from the combustor is efficiently attenuated, so that a high noise reduction effect can be obtained. In addition, since a sound wave having a large frequency is efficiently attenuated by complicated resonance, the length of the expansion cavity can be reduced as compared with a normal resonance type silencer. Furthermore, the exhaust resistance of the silencer at the time of ignition of the combustor is reduced by forming a plurality of exhaust inlets. Accordingly, ignition of the combustor is performed smoothly.
[0037]
Further, by forming the exhaust inflow ports symmetrically with respect to the center of the inflow side plate, interference of sound waves entering the muffling chamber from each exhaust inflow port is increased, and a high noise reduction effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram in which a muffler according to an embodiment of the present invention is incorporated in a combustor.
FIG. 2 is a perspective view of the muffler of FIG.
FIG. 3 is a cross-sectional view of the muffler of FIG.
FIG. 4 is a bottom view of the muffler of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Combustor 2 Burner 3 Combustion chamber 4 Heat exchanger 5 Silencer 5a Silencer cylinder 5b Inflow side plate 5c Outflow side plate 5d Exhaust outlet 5e Silencer chamber 5f Central opening 5g Side opening 6 Exhaust outlet

Claims (5)

In the muffler of the combustor attached to the stack of the combustor,
An exhaust passage through which exhaust discharged from the combustor passes;
An expansion cavity formed by enlarging the flow channel cross-sectional area of a part of the exhaust flow channel in a stepped manner,
Exhaust inflow ports formed on the exhaust inflow side of the expansion cavity,
A silencer for a water heater combustor, comprising: The expansion cavity is
A cylindrical hollow silencer,
A disk-shaped inflow side plate having a plurality of exhaust inflow ports provided on an exhaust inflow side of the sound deadening chamber,
A disk-shaped outflow side plate provided on the exhaust outflow side of the silencing chamber and having an exhaust outlet having a diameter smaller than the inner diameter of the silencing chamber,
The muffler for a combustor according to claim 1, further comprising: The muffler for a combustor according to claim 2, wherein the inlet side plate has a plurality of exhaust inlets formed symmetrically with respect to the center of the inlet side plate. An exhaust inlet formed in the inflow side plate,
A central opening having a diameter smaller than the inner diameter of the silencing chamber provided at the center of the inflow side plate,
Three side openings formed at symmetrical positions with respect to the center of the inflow side plate,
The muffler for a combustor according to claim 2, comprising: The muffler for a combustor according to any one of claims 1 to 4, wherein the expansion cavity is made of a sound absorbing material.

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