JPH02106660A - Gas combustor noise reduction device - Google Patents

Abstract

PURPOSE:To make a remarkable attenuation of sound pressure near such a frequency as annoying ears by a method wherein a combustion chamber to be formed between a burner and a heat exchanger is enclosed by a double-walled clearance layer and several small holes are made at an inner circumferential wall of reducing sound with a specified volume arranged at a circumference of the combustion chamber, and the combustion chamber and a sound reduction chamber are communicated to each other through sound absorbing holes. CONSTITUTION:A combustion chamber 3 is enclosed by a double-walled clearance layer. A sound reducing chamber 4 is arranged around the combustion chamber 3. Several small holes are made at an inner circumferential wall 5 of the sound reducing chamber 4 to make sound absorbing holes. Sound attenuation chamber 4 is extended downwardly from a peripheral part of the combustion chamber 3 to enclose the circumference of a mixed gas chamber 9. Volume of sound attenuation chamber 4 is experimentally determined due to the fact that an attenuation amount of a sound pressure is determined by a volume. The sound absorbing holes composed of several small holes are determined by calculating the frequencies of absorbed sound with an equation and correcting it under experiment. In this equation, C: a velocity of sound in air (m/s), t: a plate thickness (mm), d: a hole diameter (mm), L: a thickness of rear air layer, P: an opening rate of a hole plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise reduction device for a gas combustor such as a gas water heater.

[Conventional technology]

Gas combustors such as gas water heaters are becoming more compact due to the adoption of high-load burners.

However, in gas combustors using high-load burners, especially all-air type high-load burners, a large amount of input is required by forcibly supplying fuel gas and combustion air and combusting the mixed gas. Although it is possible to obtain compact, highly efficient, and high-load combustion by increasing the amount of combustion per unit area under the Since the abnormal noise caused by the noise is significant, measures to reduce the noise are essential. Conventionally, one of the countermeasures against this problem was to use means for slowing down the ejection speed of the mixed gas from the flame hole in the high-load burner, for example, by using a deceleration plate burner that increased the flame hole area and reduced the flame hole load. are doing.

[Problem to be solved by the invention]

In the above conventional technology, airflow noise is eliminated due to a delay in the flow velocity of the mixed gas, and the resonance sound caused by air vibration is also blurred, reducing the occurrence of abnormal noise. However, in terms of back performance, the size of the flame hole area is In particular, there is a limit to
Unpleasant sounds in the range of 60 to 70 dB, which is the most annoying sound to humans, and the strongest frequency of 200 Hz, are still unresolved, and it is necessary to reduce unique noises in this range, such as the roaring noise caused by the vibrations of combustion flames. was an issue.

In view of the problems of the conventional technology, this invention
By surrounding the combustion chamber with a perforated void layer, 20
The object of the present invention is to provide a noise reduction device for a gas combustor, which reduces unpleasant noise in the vicinity of 0 Hz by reducing unpleasant noise by sound pressure attenuation.

[Means to solve the problem]

In order to achieve the above object, the invention of claim 1 in the noise reduction device for a gas combustor of this invention surrounds the combustion chamber formed between the burner and the heat exchanger with a double-walled void layer. A sound-reducing chamber with a certain volume is provided around the combustion chamber, and a number of small holes are bored in the inner wall of the sound-reducing chamber to provide sound-absorbing holes with a certain sound-absorbing frequency. The sound reduction chamber is configured to communicate with the sound reduction chamber, and the invention of claim 2 has a structure in which a heat insulating material of a predetermined thickness is provided on the inner surface of the sound reduction chamber made of a double wall void layer. It is something.

[For production]

In the noise reduction device for a gas combustor according to the present invention configured as described above, the invention according to claim 1 is such that since the combustion chamber is surrounded by a sound reduction chamber having sound absorption holes, the noise generated within the combustion chamber is The frequency of unpleasant noises such as roaring noises caused by the vibrations of the combustion flame is reduced by absorption in the sound absorption holes made up of a large number of small holes, and the sound pressure is reduced by buffering the noise in the sound reduction chamber.

Therefore, the sound pressure in the vicinity of the 200 ce frequency, which is the most annoying sound, is significantly attenuated.

In addition, the sound absorption frequency due to the diameter and arrangement (for example, vertical and horizontal pitch) of the many small holes that make up the sound absorption holes is determined by the thickness of the inner peripheral wall, the diameter of the holes, the thickness of the air layer behind the perforated plate. The volume of the sound attenuation chamber is determined by a rough estimate based on the hole area ratio, etc., and then modified through experiments to determine the optimal one. The volume is determined by experiment or other tests to obtain the highest amount of attenuation in conjunction with the sound absorption frequency of the sound absorption hole.

In the invention as claimed in claim 2, since the heat insulating material is provided on the inner surface of the sound attenuation chamber, the efficient sound reduction is made more effective by the buffering effect in the sound attenuation room in combination with the sound absorption effect of the insulating material. It can be done.

[Embodiments] Hereinafter, embodiments of the noise reduction device for a gas combustor according to the present invention will be described with reference to the drawings.

In the embodiment shown in FIGS. 1 and 2, the noise reduction device of the present invention is applied to an instantaneous gas water heater. A high-load plate burner in which a large number of combustion flame holes 1b formed by a hole and a prepared flame hole consisting of a plurality of small diameter flame holes are arranged with a constant interval between adjacent combustion flame holes. By increasing the amount of combustion per unit area, the combustion flame becomes larger and high-load combustion with a large load on the combustion chamber can be achieved, while abnormal noise caused by airflow noise etc. can be reduced. 2 is a heat exchanger, which is a fin-and-tube type heat exchanger, which exchanges heat while the cold water from the water supply pipe flows through the heat absorption tube, heats it to a heating field, and draws out hot water at the desired temperature from the hot water outlet pipe. It has become. 3 is a combustion chamber, which includes the high-load plate burner 1 and the heat exchanger 2.
is formed between. Reference numeral 8 designates an exhaust top provided above the heat exchanger 2, which is used to discharge exhaust gas heated in the heat exchanger 2 by the combustion flame 13 of the high-load plate burner 1 to the outside. 9 is a high load plate burner 1
A mixed gas chamber formed in the lower part of the mixed gas chamber 9.A two-stage porous rectifier plate 10.11 is provided on the upper part, and a mixed gas introduction pipe 12 is connected to the lower part. The mixed gas supplied to the two-stage rectifying plate 10.1
1, the fluid is rectified and dispersed to be evenly supplied to each part of the high-load plate burner 1.

In the instantaneous gas water heater having the above configuration, the invention according to claim 1 provides a sound reduction chamber 4 around the combustion chamber 3 by surrounding the combustion chamber 3 with a double-walled void layer. A number of small holes are bored in the inner circumferential wall 5 to provide sound absorption holes 6, and the sound reduction chamber 4 extends downward from the periphery of the combustion chamber 3 to the periphery of the mixed gas chamber 9, as in the embodiment. In addition to surrounding and forming the combustion chamber 3
or by extending outward only around the combustion chamber 3.
It may be formed by extending upward from the periphery of the heat exchanger 2 to surround the periphery of the heat exchanger 2. The sound reduction chamber 4 can reduce sound if it has a certain volume, but since the amount of sound pressure attenuation is determined by the volume, the volume that provides the highest amount of attenuation is determined by experiment or other means.

In addition, the sound absorption hole 6 consisting of a large number of small holes, for example, C: Speed of sound in air (m/s): Temporary FX (m) d: Diameter of the hole (m) L: Thickness of the rear air layer ( m) P: Perforation ratio of perforated plate (= i1'') The sound absorption frequency is determined using the calculation formula, and then the optimum one is determined by modifying it through experiment.The above calculation According to experiments, the diameter and arrangement (horizontal and vertical pinch) of the small holes are the third
As shown in the figure and Fig. 4, ti&50■, horizontal 77+
Small holes with a diameter of 3I1m are drilled at a pitch of 20am (
It was optimal to drill holes with small holes (vertical and horizontal spacing) as this did not affect the combustibility of the flame.

In the invention as claimed in claim 2, a heat insulating material 7 is provided on the inner surface of the sound attenuation chamber 4, and the heat insulating material 7 may be made of a material that also has sound absorbing properties, such as ceramics or glass wool. It is preferable to use a heat insulating material, the thickness of which is about 7 ma+, and is attached to the inside of the sound attenuation chamber 4 formed of a stainless steel plate 14 with a thickness of about 0.5 mm, or by other means. .

The effects of the above embodiments will now be specifically explained along with experimental examples.

EXPERIMENTAL EXAMPLE In the instantaneous gas water heater (see FIGS. 1 and 2) equipped with the sound absorption holes 6 and the sound reduction chamber 4 of the example, an experiment was conducted on the difference in sound pressure depending on the presence or absence of the sound absorption holes 6.

The measurement point was set 1 m away from the instantaneous gas water heater, and the fuel gas of CM was used as the gas type, and the air amount was 16 Nrr.
r/h, 14 Nrrr/h, 12 Nrrf
/h, the results of measuring the sound pressure are shown in Table 1.
The values shown in were measured.

The sound pressure difference in the numerical values in Table 1 depending on the presence or absence of sound absorption holes,
That is, ■-■ at 16 Nboh, 14 Nrrr
■-■ at /h, 5th @-[phase] at 12 Nd/h
It is shown graphically in the figure. In addition, in Fig. 5, a is 16
■-■ at N-boh, b is 14 ■-■ at N-boh
, C indicates @-[phase] at 12 Npo/h.

Frequency 1 (1
/3 octave) Sound pressure difference (dB) for (H2)
As is clear from the above, the unpleasant sound in the frequency range centered on 200 Hz is approximately 60 to 70 d for those without sound absorption holes.
B, whereas the one with sound absorption holes is approximately 27 dB.
Furthermore, by reducing the frequency by 200 Hz, the sound pressure in the entire area can be reduced by 10 dB, so the unpleasant noises that are most annoying to humans, such as the humming noise caused by the vibration of the combustion flame, can be reduced by 200 Hz. Sound absorption decreases and almost disappears.

[Effects of the Invention] Since the present invention has the above-mentioned configuration, it achieves the following effects.

The invention according to claim 1 provides a sound reduction chamber having a constant volume around the combustion chamber, and a sound absorption hole having a constant sound absorption frequency made of a large number of small holes is provided in the inner circumferential wall of the sound reduction chamber. The sound pressure of unpleasant sounds such as whirring noise caused by the vibration of the combustion flame generated in the combustion chamber is absorbed and reduced by the sound absorption holes and the sound reduction chamber, and the sound pressure around 200Hz, which is considered to be the most annoying sound, is significantly attenuated. In particular, in gas combustors using all-in-one air type high-load burners, it is possible to almost eliminate unpleasant noises in the range around 200 centimeters, which has traditionally been a problem. .

In addition, in the invention as claimed in claim 2, since the heat insulating material of a predetermined thickness is provided on the inner surface of the sound attenuation chamber, in combination with the sound absorption effect of the heat insulating material, the noise reduction in the sound attenuation chamber can be effectively performed. .

Note that, as in the illustrated embodiment, if the sound reduction chamber is formed to surround the area from the combustion chamber to the mixed gas chamber,
This is advantageous in that the instruments can be made compact.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the noise reduction device for a gas combustor according to the present invention, FIG. 2 is a sectional view taken along line XX in FIG.
Figure 3 is a front view showing an example of the diameter and arrangement of sound absorption holes;
The figure is a cross-sectional view, and FIG. 5 is a graph showing the relationship between the sound pressure difference and the frequency obtained in an experimental example. 1...-burner, 2... heat exchanger, 3... combustion chamber,
4...Sound reduction chamber, 5...Inner peripheral wall, 6...Sound absorption hole, 7
...Insulation material. Figure 1↑

Claims (1)

[Claims] 1. A combustion chamber (3) formed between a burner (1) and a heat exchanger (2), etc., surrounded by a double wall void layer.
A gas combustor characterized in that a sound reduction chamber (4) is provided around the sound reduction chamber (4), and a number of small holes are bored in the inner circumferential wall (5) of the sound reduction chamber (4) to provide sound absorption holes (6). Noise reduction device. 2. The noise reduction device for a gas combustor according to claim 1, wherein a heat insulating material (7) is provided on the inner surface of the sound reduction chamber (4).