JPS60213706A - Pulse combustion apparatus - Google Patents

Abstract

PURPOSE:To obtain a low-noise pulse combustion apparatus, by providing a porous plate with a space between the plate and the inner wall of a feed air conduit interior and filling up the space with acoustic material. CONSTITUTION:A porous plate 7 is provided with a space between the plate and the inner wall of a feed air conduit 5 interior, and the space is filled up with acoustic material 11. Combustion noise 12 transmitted through an air chamber 4 is absorbed by a plurality of small holes 13 bored through the surface of the porous plate 7 and is introduced into the space between the porous plate 7 and the feed air conduit 5. The space is filled up with the acoustic material 11, and so noise introduced into the space is absorbed by the acoustic material 11 between the porous plate 7 and the inner wall surface for the feed air conduit 5 and at the same time, as the result of the continuous noise impact and dispersion, the combustion noise 12 is silenced by mutual interference.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a pulse combustor.

Conventional Structure and Problems When a pulse combustor is started, combustion air is supplied to the combustion chamber using fuel gas and a blower fan, and combustion is forced by operating a spark plug. Once the system has stabilized and formed a combustion cycle, even if the spark plugs and blower fan are stopped, combustion air is automatically sucked in and self-ignition continues pulsed combustion at a constant frequency of tens to hundreds of hertz. do.

Such a pulse combustor burns under high load, has good heat transfer characteristics, automatically performs ignition and air supply/exhaust except during startup, and has the advantages of a simple structure.

However, the pulse combustor has the problem of high noise during combustion. For this purpose, a muffler is installed, but since the acoustic impedance changes when a muffler is installed, the fundamental frequency of the combustion cycle may change. For this reason, the muffler that has been installed is often not as effective as expected. Therefore, we surrounded the air pulp equipment with an air cushion chamber, and made the acoustic impedance of the air cushion chamber sufficiently large so as not to affect the fundamental frequency of pulse combustion. The sound is effectively muted. However, in the case of pulse combustion, since the combustion noise is very loud, there are problems such as vibration of the wall surface of the air cushion chamber and sound leakage from the wall surface, especially sound leakage in the low frequency range. For this reason, even if a muffler is installed to reduce the noise emitted from the supply and exhaust ports, there are cases in which a problem arises in that the sound leaking from the main body becomes louder.

OBJECTS OF THE INVENTION The present invention has been made in view of these problems, and it is an object of the present invention to provide a pulse combustor with a simple structure and low noise.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a perforated plate in the air supply path with a gap between it and the inner wall surface thereof, and fills this gap with a sound absorbing material.

Description of examples An embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, the pulse combustor of this embodiment includes a combustion chamber 1, a till pipe 2, an internal fire plug 3, an air chamber 4, an air supply path 6, an air pulp device 6, a perforated plate 7, an air It is composed of a cushion chamber 8, a fuel supply path 9, a fuel pulp device 10, and a sound absorbing material 11.

The combustion sound of the pulse combustor has a fundamental frequency f0 determined by the shapes of the combustion chamber 1 and the till pipe 2, and harmonic components consisting of sounds at integral multiples of the fundamental frequency. Since this fundamental frequency f0 is a low-frequency sound ranging from several tens of hertz to several hundred hertz, this sound vibrates the wall surface of the air cushion chamber 8, thereby preventing sound leakage from the wall surface, especially low-frequency component sound leakage. It's getting bigger.

Therefore, in this embodiment, in order to reduce the sound that passes through the air valve device 6 and enters the air cushion chamber 8, a gap is created in the air supply path S with the inner wall surface of the air supply path 5. Perforated plate 7f: provided 1, and the gap between the air supply path 6 and the perforated plate 7 is filled with sound absorbing material 11. The perforated plate 7 may be a metal plate with many small holes, or a material with many small holes such as sintered metal or foamed ceramic. As shown in FIG.
The sound is absorbed and enters the gap between the air supply path 6 and the perforated plate 7. Since the void is filled with the sound absorbing material 11, the sound that enters the void will be absorbed by the sound absorbing material 11 between the inner wall surface of the air supply path 5 and the surface of the perforated plate 7, and will not collide or be dispersed. This is repeated, and the combustion sound 12 is muffled due to mutual interference. Silencing due to this mutual interference is effective over a wide range from low frequency ranges to high frequency ranges. Further, since the sound absorbing material 11 has the property of blocking fluid and allowing sound pressure to pass through, even if the present invention is implemented, the flow state of the air supply path 6 will not change and combustion will not be affected. Furthermore, the present invention does not use a method of simultaneously attenuating sound pressure and flow pressure by providing an expansion chamber or the like in the air supply system as a method for reducing combustion noise. Combustion noise can be muffled without attenuating the operating pressure of the pulp 14. As a result, the air pulp 14 is opened and closed smoothly, and combustion noise can be reduced while maintaining a good combustion state.

As described above, the combustion noise generated in the combustion chamber 1 is muffled when passing through the air supply path 6, and the air cushion chamber 8
is radiated to. Therefore, the low-frequency sound component that causes the wall surface of the air cushion chamber 8 to vibrate is attenuated, the wall surface of the air cushion chamber 8 hardly vibrates, and the leakage of sound from the wall surface is significantly reduced. Therefore, noise can be reduced compared to conventional pulse combustors.

Effects of the Invention According to the present invention, the vibration of the wall surface of the air cushion chamber and the leakage of sound from the wall surface are significantly reduced, which is effective in reducing the noise of the pulse combustor.

[Brief explanation of drawings]

FIG. 1 shows the cross-sectional structure of a pulse combustor according to an embodiment of the present invention.
Figure 2 is an enlarged sectional view of the air supply path of the pulse combustor. 1... Combustion chamber, 2... Till pipe,
6... Air supply path, 6... Air pulp device, 7... Perforated plate, 8... Air cushion chamber, 11...・Sound absorbing material.

Claims (1)

[Claims] A till pipe connected to one end of the combustion chamber, a fuel supply path and an air supply path connected to the other end of the combustion chamber, a fuel valve device connected to the fuel supply path, and an air pulp connected to the air supply path. an apparatus; the air pulp apparatus;
An air cushion chamber is housed in the air cushion chamber and connected to the air supply path, and a perforated plate is provided in the air supply path with a gap between the inner wall surface of the air supply path and a sound absorbing chamber. Fully filled pulse combustor.