JPH0328644B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pulse combustor that serves as a heat source for domestic or industrial water heaters, space heaters, and the like.

Conventional configuration and problems thereof When a pulse combustor is started, fuel and combustion air are supplied to the combustion chamber by a blower fan, and combustion is forced by operating a spark plug. Once the system stabilizes and forms a combustion cycle, combustion air is automatically sucked in and self-ignition continues pulsed combustion at a constant frequency of tens to hundreds of hertz even when the spark plugs and blower fan are stopped.

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, a problem with the pulse combustor is that it produces a lot of noise during combustion. For this reason, various functional parts are sound-insulated and mufflers are installed. However, when a muffler is installed, the acoustic impedance changes, which can change the fundamental frequency of the combustion cycle. For this reason, the muffler that you have taken the pains to install is often not as effective as expected.
Therefore, the air valve device is surrounded by an air cushion chamber to insulate the sound leakage from the air valve device, and the acoustic impedance of the air cushion chamber is made large enough so as not to affect the fundamental frequency of pulse combustion. Even when a muffler is attached, a predetermined frequency can be maintained, making the muffler effective at muffling noise. However, in the case of pulse combustion, the combustion noise is very loud, so if the air valve device is surrounded by an air cushion chamber, vibrations of the walls of the air cushion chamber and sound leakage from the wall surface, especially sounds in the low frequency range, will also leak. becomes larger, and the thickness of the air cushion chamber must be increased. Therefore, even if a muffler is installed to reduce the noise emitted from the supply and exhaust ports, the noise leaking from the air cushion chamber increases, and a problem has arisen in which countermeasures must be taken.

Purpose of the Invention The present invention has been made in view of this problem.
By improving the air valve device, a pulse combustor with a simple structure and low noise is provided.

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

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the pulse combustor of the present invention includes a combustion chamber 1, a tail pipe 2 at one end thereof, a spark plug 3, an air chamber 4, an air supply path 5, an air valve device 6, a perforated plate 7, an air It is composed of a cushion chamber 8, a fuel supply path 9, a fuel valve device 10, and a sound absorbing material 11.

The combustion sound of the pulse combustor has a fundamental frequency determined by the shapes of the combustion chamber 1 and the tail pipe 2, and harmonic components consisting of integral multiples of the fundamental frequency. Since this fundamental frequency is a low frequency sound ranging from several tens of hertz to several hundred hertz, this sound is radiated from the air valve device 6 to the air cushion chamber 8, causing the wall surface of the air cushion chamber 8 to vibrate. , which increases the leakage of sound from the walls, especially of low-frequency components.

Therefore, in the embodiment of the present invention, in order to reduce the combustion sound when it passes through the air valve device 6,
A perforated plate 7 is provided in the air valve device 6 to form a gap with the inner wall surface of the air valve device 6, and a sound absorbing material 11 is filled in the gap between the inner wall surface of the air valve device 6 and the perforated plate 7. The perforated plate 7 may be a metal plate with many small holes, or a metal plate with many small holes such as sintered metal or foamed ceramic.
As shown in FIG. 2, the air valve device 6 includes an air valve chamber 13, an air valve port 14, and an air valve 15. A perforated plate 7 is provided inside the air valve chamber 12 with a gap between it and the wall surface.
When combustion occurs in the combustion chamber 1, a rapid pressure rise occurs within the combustion chamber 1, and the air valve 14 is pressed against the air valve port 13 due to the pressure propagation, thereby blocking the air port 15 on the air port. On the other hand, combustion noise is simultaneously radiated into the air valve chamber 12 via the air supply path 5. Combustion sound 16 entering the air valve chamber 12
is a large number of small holes 17 bored on the surface of the perforated plate 7.
The air enters the gap filled with the sound absorbing material 11 between the inner wall surface of the air valve chamber 12 and the perforated plate 7. The combustion sound 16 that has entered this gap repeatedly collides and disperses between the inner wall surface of the air valve chamber 12 and the surface of the perforated plate 7 while being absorbed by the sound absorbing material 11. Some of the sound that has entered the air gap is returned to air valve chamber 1.
Collision and dispersion occur repeatedly between this sound and the sound reverberating in the air valve chamber 12. In this way, the combustion sound 16 repeatedly collides and disperses within the air valve chamber 12, and the mutual interference mutes the combustion sound. Silencing due to this mutual interference is effective over a wide range from low frequency ranges to high frequency ranges. Furthermore, muffling the combustion noise in the air valve chamber 12 also prevents vibration of the air valve device 6 itself, which also has the effect of preventing new secondary noises from occurring on the surface of the air valve device 6.

As described above, the combustion noise generated in the combustion chamber 1 is muffled when passing through the air valve device 6 and radiated to the air cushion chamber 8. 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, since the combustion sound passing through the air valve chamber and radiated to the air cushion chamber is reduced, the vibration of the wall surface of the air cushion chamber and the leakage of sound from the wall surface are reduced. It is effective in reducing the noise of the pulse combustor.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pulse combustor according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of an air valve device of the same pulse combustor. DESCRIPTION OF SYMBOLS 1... Combustion chamber, 2... Tail pipe, 5... Air supply path, 6... Air valve device, 7... Perforated plate, 8... Air cushion chamber, 11... Air valve chamber, 12 ...Air valve port.

Claims (1)

[Claims] 1 A tail pipe connected to one end of the combustion chamber, a fuel supply passage and an air supply passage connected to the other end of the combustion chamber, a fuel valve device communicating with the fuel supply passage, and an air communication passage communicating with the air supply passage. a valve device; an air cushion chamber housing the air valve device therein and communicating with the air supply path; A pulse combustor is provided with a perforated plate, and a gap between the inner wall surface of the air valve device and the perforated plate is filled with a sound absorbing material.