JPS6033408A - Pulsating combustion apparatus - Google Patents

Abstract

PURPOSE:To provide a pulsating combustion apparatus in which noise is low, by providing a resonator which resonates in the basic frequency band of pulsating combustion in an air supply path which connects an air valve device to a combustion chamber. CONSTITUTION:A resonator 6 which resonates in the basic frequency band of pulsating combustion is provided in an air supply path 5 which connects an air valve device 7 to a combustion chamber 1. A Helmholtz resonator such as the one which consists of an air supply path 5 with a plurality of holes 12 being punched and being surrounded by a resonance chamber 13, or the other one which consists of an air supply path 5 to which a pipe 14, of which one end is connected to a resonance chamber 13, is connected, can be used as a resonator 6. The noise of basic frequency can be silenced when combustion noise passes through the resonator 6, by determining the shape and form of each element in accordance with the basic frequency band of pulsating combustion. In addition, the noises of higher frequency elements can also be expected to be silenced by this resonator 6.

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, fuel gas and combustion air are supplied to the combustion chamber by a blower fan, and combustion is forced by operating the ignition valve. Once the system stabilizes and forms 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.

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 installed muffler is often not as effective as expected. Therefore, the air valve device is surrounded by an air cushion chamber, and the acoustic impedance of the air cushion chamber is made large enough to not affect the fundamental frequency of pulse combustion, so that even if a muffler is attached, a predetermined frequency can be maintained. Effective sound deadening. However, in the case of pulse combustion, pressure fluctuations within the combustion chamber are large, so there is a drawback that sound leakage from the wall surface of the air cushion chamber, especially sound in the low frequency range, is large.

OBJECTS OF THE INVENTION The present invention has been made in view of these drawbacks, 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 The present invention connects till pulp to one end of a combustion chamber, connects a gas supply path equipped with a gas pulp device to the other end, and an air valve device provided in an air cushion chamber, and connects the combustion chamber to the air valve. This is a pulse combustor that is constructed by providing a resonator that resonates at the fundamental frequency of pulse combustion in the air supply path that connects the device.

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 the present invention has a combustion chamber 1
．． Tilvipe 22 spark plug 3. Air chamber 4, air supply path 6. Resonator 6. Air valve device 7° air cushion chamber 8. Gas supply path9. Gas valve device 10. It is composed of a solenoid valve 11.

The combustion sound of a pulse combustor (as shown in Fig. 2) has a fundamental frequency f determined by the shapes of the combustion chamber 1 and till pipe 2, and harmonic components consisting of sounds at integral multiples of the fundamental frequency. Fundamental frequency f.

Since this is a low frequency sound ranging from several tens of hertz to several hundred hertz, this sound vibrates the wall of the air cushion chamber 8.
Sound leakage from walls, especially low-frequency sound leakage, is increased.

Therefore, in the present invention, a resonator 6 that resonates at this frequency is provided in the air supply path 6 that connects the combustion chamber 1 and the air valve device 7. A plurality of holes 12 are provided in the air supply path 6 as shown in Figure a.
Use a Helmholt resonator, such as one with a hole bored through it and surrounded by a resonance chamber 13, or one in which the air supply path 5 is connected to a conduit 14 whose one end is connected to the resonance chamber 13, as shown in (b). Can be done. The resonance frequency is determined by the shape of each element. Therefore, by determining the shape of each element in accordance with the fundamental frequency f0 of pulse combustion, the combustion sound can be reduced to the resonator 6.
It is possible to muffle the sound of the fundamental frequency when passing through. Furthermore, harmonic components can also be expected to be muffled. Further, as the resonator 6, an air column resonator as shown in FIG. 3(C) in which a resonance tube 15 with one end closed is connected to the air supply path 5 can also be used. When the shape of each element is determined, the air column resonator resonates at the fundamental frequency and its harmonic components, so it is very effective in silencing noise of the fundamental frequency and its harmonic components, such as pulse combustion. be.

When the resonance chamber 13 and the resonance tube 16 are made larger to increase the silencing effect, the combustion air flowing through the air supply path 6 flows into the resonance chamber 13 and the resonance tube 15, disturbing the flow of combustion air and causing a combustion condition. may deteriorate and combustion may not continue.

In that case, the boundary between the resonator 6 and the air supply path 5, that is, the boundary between the plurality of holes 12 and the resonance chamber 13 in FIG.
In (b), the boundary between the air supply path 5 and the conduit 14, and in (C), the boundary between the air supply path 6 and the resonance tube 15 is provided with an acoustically transparent section 16 that has the property of blocking fluid flow and allowing sound pressure to pass through. Just set it up. The sound-transmitting section 16 is composed of a thin film-like material that blocks fluid and allows only sound pressure to pass through, or is constructed by filling the resonance chamber 13 and resonance tube 16 with a sound-absorbing material such as glass wool. Although the fluid resistance is very large, the acoustic resistance is very small. This makes it difficult for the combustion air to flow into the resonance chamber 13 and the resonance tube 15, while the combustion sound flows into the resonance chamber 13 and the resonance tube, making it possible to muffle the sound without disturbing the flow field and improve combustion and conditions. can be maintained.

Therefore, when the combustion sound generated in the combustion chamber 1 passes through the air supply path 5, the sound of the fundamental frequency and harmonic components are muffled and enters the air cushion chamber 8. Therefore, the low-frequency sound component that causes the wall surface of the air cushion chamber to vibrate is attenuated, the wall surface of the air cushion chamber hardly vibrates, and the leakage of sound from the wall surface is significantly reduced. Therefore, noise is reduced compared to conventional burners,
Even if a muffler is to be installed, it is sufficient to install a muffler that is relatively small and has a simple structure.

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

[Brief explanation of drawings]

Fig. 1 is a block diagram of a pulse combustor according to an embodiment of the present invention, Fig. 2 is a frequency characteristic diagram of the pulse combustor, and Fig. 3 is a block diagram of a different embodiment of the resonator of the pulse combustor of the present invention. It is. 1... Combustion chamber, 2... Till pipe,
5... Air supply path, 6... Resonator, 7
... Valve device, 8 ... Air cushion chamber, 16 ... Sound transmission section.

Claims (4)

[Claims] (1) A till pipe connected to one end of the combustion chamber, a gas supply path and an air chamber connected to the other end of the combustion chamber, an air supply path connected to the air chamber, and an air pulp to the air supply path. 1. A pulse combustor comprising at least a cushion chamber connected through the air supply path, the air supply path being provided with a resonator that resonates at the fundamental frequency of pulse combustion. (2) The pulse combustor according to claim 1, wherein the resonator has Helmholtz resonance at the fundamental frequency of pulse combustion. (3) The pulse combustor according to claim 1, wherein the resonator resonates with the air column at the fundamental frequency of pulse combustion. (4) Claims 1, 2, or 2, in which a sound-transmitting part is provided at the boundary between the air supply path and the resonator, and has the property of blocking fluid flow and allowing sound pressure to pass through. :゛The pulse combustor described in item 3.