JP4606888B2 - Combustion equipment - Google Patents

Description

  The present invention relates to a combustion apparatus such as a water heater in which an all-primary air combustion type burner having a combustion plate in which a large number of small flame holes are formed is disposed in a combustion housing.

  Generally, in a water heater, a heat exchanger is arranged at the upper part of the combustion housing and a Bunsen type burner is arranged at the lower part of the combustion housing. However, the entire water heater has a combustion plate having many small flame holes. There is also known a primary air combustion type burner arranged in a combustion housing (see, for example, Patent Document 1).

  By the way, in a combustion apparatus, a Helmholtz resonance sound having a relatively low frequency is generally generated as combustion noise. However, if the combustion apparatus uses an all-primary-air combustion burner as the burner, and the combustion housing has an opposing wall parallel to the combustion plate facing the combustion plate of the burner, pressure fluctuations caused by combustion vibrations The energy is reflected by the facing wall and fed back to the combustion plate, and a resonance sound due to air column vibration is generated.

Here, if a sound absorbing material is attached to the opposing wall, pressure fluctuation energy is absorbed by the sound absorbing material, and combustion resonance noise due to air column vibration can be reduced. However, this requires a sound-absorbing material, which increases the cost.
Japanese Patent No. 2775197 (FIG. 6)

  In view of the above points, an object of the present invention is to provide a low-cost combustion apparatus that can reduce combustion resonance noise without using a sound absorbing material.

In order to solve the above-mentioned problems, the present invention is a combustion apparatus in which a burner of an all-primary air combustion type having a combustion plate in which a large number of small flame holes are formed is disposed in the combustion housing , in those with the plane-parallel opposite walls of the combustion plate mixture jetted from opposed and the small fire hole to the combustion plate is burned, the opposing walls, a large number of the combustion plate opposite to the surface having an irregular surface to which a convex portion formed by densely arranged, the upper part of the said combustion housing, said burner being arranged in the downward posture toward the combustion plate downwards, the bottom wall of the combustion housing is die-cast aluminum the molded, the bottom wall becomes the facing wall, the combustion housing, wherein the combustion plate and condensing type heat exchanger which is located between said bottom wall is arranged.

  According to the present invention, the pressure fluctuation wave is irregularly reflected by the unevenness of the wall surface of the opposing wall, and the surface resistance of the wall surface is increased to obtain the pressure fluctuation attenuation action, and as a result, the pressure fluctuation fed back to the combustion plate The energy is attenuated, and the combustion resonance due to air column vibration is reduced. And unlike what uses a sound-absorbing material, since it only forms an unevenness | corrugation in a wall surface, a number of parts does not increase and it can aim at cost reduction.

  By the way, an all-primary air combustion burner is disposed in the upper part of the combustion casing in a downward posture with the combustion plate facing downward, and is placed in the combustion casing between the combustion plate and the bottom wall of the combustion casing. When a heat exchanger of the same type is arranged, water in the combustion exhaust gas condensed by the heat exchanger falls on the bottom wall. Here, the bottom wall serves as an opposing wall facing the combustion plate of the burner, but a sound absorbing material cannot be attached to the bottom wall because condensed water falls. According to the present invention, even if no sound absorbing material is attached to the bottom wall, the wall surface can be formed in an uneven surface to reduce combustion resonance noise, which is very advantageous.

  Hereinafter, an embodiment in which the present invention is applied to a combustion apparatus including the water heater shown in FIG. 1 will be described. This combustion apparatus includes a combustion housing 1, and an all-primary air combustion burner 3 having a ceramic combustion plate 2 in which a large number of small flame holes 2 a are formed in the upper portion of the combustion housing 1 is provided with a combustion plate 2. It is arranged in a downward posture facing downward. An air supply passage 5 connected to the combustion fan 4 is connected to the burner 3. Then, a fuel gas supply pipe 6 is connected to the air supply passage 5 so that an air-fuel mixture of fuel gas and primary air is supplied to the burner 3 so that the air-fuel mixture is combusted on the lower surface of the combustion plate 2. .

  In the combustion housing 1, a condensing type heat exchanger 8 is disposed between the combustion plate 2 and the bottom wall 7 of the combustion housing 1. The heat exchanger 8 includes a large number of endothermic fins 8a and meandering endothermic pipes 8b penetrating through the endothermic fins 8a, and water flowing through the endothermic pipes 8b is radiated from the combustion plate 2 and the combustion exhaust of the burner 3. In addition, the water in the combustion exhaust is condensed and the water is also heated by the latent heat. The combustion exhaust gas that has passed through the heat exchanger 8 is discharged to the outside through an exhaust duct 10 connected to an exhaust port 9 opened at the lower side wall of the combustion housing 1.

Here, the bottom wall 7 of the combustion housing 1 is an opposing wall that faces the combustion plate 2 and is parallel to the surface (lower surface) of the combustion plate 2 in which the air-fuel mixture ejected from the small flame hole 2a burns . If the wall surface of the bottom wall 7 is flat, the pressure fluctuation energy generated by the combustion vibration is reflected by the bottom wall 7 and fed back to the combustion plate 2 to generate a resonance sound due to air column vibration. In particular, after the burner 3 is ignited, combustion resonance noise is likely to occur during the temperature rising process in which the temperature in the combustion housing 1 rises. The frequency f of the resonance sound due to the air column vibration is f = C / 2L where L is the distance between the combustion plate 2 and the bottom wall 7 and C is the speed of sound. When an experiment was performed using a combustion apparatus with L = 0.3 m, it was confirmed that resonance sound having a frequency of about 600 to 630 Hz was generated during the temperature rising process. When the average temperature in the combustion casing 1 during the temperature raising process is set to 70 ° C. and the sound velocity (373.5 m) at this temperature is substituted into C in the above formula, when L = 0.3 m, f = 622.5 Hz. Therefore, it agrees with the measured frequency of the resonance sound. From this, it can be seen that resonance sound is generated by air column vibration.

  Combustion resonance noise due to air column vibration can be reduced by attaching a sound absorbing material to the bottom wall 7 and absorbing the pressure fluctuation energy reflected by the bottom wall 7 with the sound absorbing material. However, since condensed water falls from the heat exchanger 8 to the bottom wall 7, a sound absorbing material cannot be attached to the bottom wall 7.

  Therefore, in the present embodiment, the wall surface of the bottom wall 7 is formed as an uneven surface in which semicylindrical convex portions 7a having a diameter of about 20 mm are arranged without gaps as shown in FIG. According to this, the pressure fluctuation wave is irregularly reflected by the unevenness of the wall surface of the bottom wall 7, and the surface resistance of the wall surface is increased, so that the pressure fluctuation attenuation action is obtained. As a result, the pressure fluctuation energy fed back to the combustion plate 2 is attenuated, and combustion resonance noise due to air column vibration is reduced.

  Since the combustion resonance noise can be reduced by forming the wall surface of the bottom wall 7 in this manner, it is very effective as a noise countermeasure for the combustion apparatus in which condensed water falls on the bottom wall 7. Here, when the combustion housing 1 is made of aluminum die-casting, the wall surface of the bottom wall 7 can be easily formed into an uneven surface by a mold, and when the combustion housing 1 is made of sheet metal, the bottom wall can be formed by press molding. The wall surface of 7 can be easily formed as an uneven surface. And since a sound-absorbing material becomes unnecessary, a number of parts does not increase and cost reduction can be aimed at.

  In the above embodiment, the wall surface of the bottom wall 7 is formed as an uneven surface in which semi-cylindrical convex portions 7a are arranged. However, the present invention is not limited to this, for example, a hemispherical shape as shown in FIG. The protrusions 7b may be formed on the uneven surface, or the conical protrusions 7c as shown in FIG. 4 may be formed on the uneven surface. In addition, when a plane part exists widely between these convex part 7a, 7b, 7c, since a pressure fluctuation wave will be reflected toward the combustion plate 2 in a plane part, convex part 7a, so that a plane part hardly remains. It is necessary to arrange 7b and 7c densely.

  As described above, the embodiment in which the present invention is applied to the combustion apparatus in which the all primary air combustion burner 3 is arranged in the downward direction in the upper portion of the combustion housing 1 has been described. However, the all primary air combustion burner is disposed in the lower portion of the combustion housing. The present invention can be similarly applied to a combustion apparatus arranged in an upward orientation, in which the ceiling wall of the combustion housing is an opposing wall parallel to the combustion plate facing the combustion plate of the burner. In other words, the wall surface of the ceiling wall of the combustion housing is formed as an uneven surface, so that combustion resonance noise due to air column vibration can be reduced. Further, the present invention can also be applied to a combustion apparatus other than a water heater in which no heat exchanger is disposed in the combustion housing.

Explanatory sectional drawing which shows the combustion apparatus of embodiment of this invention. The perspective view which shows the wall surface shape of the bottom wall of the combustion housing of the combustion apparatus of FIG. The perspective view which shows the wall surface shape of 2nd Embodiment. The perspective view which shows the wall surface shape of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Combustion housing, 2 ... Combustion plate, 2a ... Small flame hole, 3 ... All primary air combustion type burner, 7 ... Bottom wall (opposing wall) of combustion housing, 7a, 7b, 7c ... Convex part of wall surface of opposing wall , 8 ... Heat exchanger.

Claims (1)

In the combustion housing, a combustion apparatus which is disposed a burner of the total primary air combustion having a combustion plate formed with a number of small burner ports, the combustion housing is the opposite and the small fire hole to the combustion plate In the one having an opposing wall parallel to the surface of the combustion plate where the jetted air-fuel mixture burns,
The opposing wall has a concavo-convex surface formed by densely arranging a large number of convex portions on a surface facing the combustion plate,
At an upper portion in said combustion housing, they are arranged in a flat position in which the burner is directed to the combustion plate downwards,
The bottom wall of the combustion housing is molded by aluminum die casting, the bottom wall becomes the opposing wall,
The combustion in a housing, the combustion plate and the combustion apparatus characterized by condensing type heat exchanger which is located is disposed between the bottom wall.

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