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JPH0946786

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH0946786
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the
structure of a sound sensor probe used in an apparatus or the like for determining ignition /
extinguishing of a burner in an industrial furnace or the like.
[0002]
2. Description of the Related Art As this type of ignition detection means, for example, there is an
acoustic type as disclosed in Japanese Utility Model Publication No. 4-49482.
[0003]
In an industrial furnace or the like, when the fuel injected from the burner burns, volumetric
expansion occurs, which causes minute pressure oscillations in the furnace.
The combustion noise resulting from this pressure vibration is guided to a microphone outside
the furnace, and among the electrical signals output by the microphone, a frequency component
capable of clearly identifying combustion is extracted and electrically processed, and the
processing result is judged. Ignition / extinguishing is determined by comparing with a value
(threshold value). When this means is used, as shown in FIG. 14, the probe 21 of the sound
sensor 20 having a microphone is made to face the vicinity of the tip of the burner 32 through
the furnace wall 31 of the industrial furnace 30, and the combustion noise is taken out of the
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furnace . 10 is a flame.
[0004]
The conventional probe 21 of this type is, as shown in FIG. 15, a pipe (pipe) having a
predetermined length, which extends from the sensor body 23. Reference numeral 24 denotes a
probe holder, and the probe 21 is fixed to a holding member (not shown) of the furnace 30 via
the probe holder 24. Reference numeral 25 denotes a microphone in the sensor body 23.
[0005]
In the case of a furnace in which fuel and combustion air are fed at low speed (20 to 30 m / s),
since the level of air flow noise generated by these flows is relatively low, this air flow noise and
Discrimination with the combustion noise is easily possible.
[0006]
However, in the furnace blowing the combustion air at high speed, separation of the air flow
occurs at the tip end of the probe 21 or the like, and a wind noise is generated.
Theoretically, the energy level of the airflow noise increases and decreases in proportion to the
sixth power of the flow velocity. If the flow velocity is doubled, the airflow noise becomes 64
times (18 db up).
[0007]
As shown in FIG. 15, the tip 21A of the conventional probe 21 is cut at a right angle to the axial
direction, and since the sound intake port 21B is opened at this end face, the wind noise is
eliminated. It is easy to occur. For this reason, in the case of a furnace blowing combustion air at
a high speed, the combustion noise entering the microphone 25 may be buried in the large air
flow noise due to the wind noise etc. FIGS. 16 and 17 show an example in which the frequency
and the like hardly change between the time of combustion and the time of misfire, and the case
where the discrimination between the combustion and the misfire can not be made occurs.
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[0008]
(A) and (B) of FIG. 16 show the amplitude and frequency of the in-furnace sound at the time of
combustion, and (A) and (B) of FIG. 17 show the amplitude and frequency of the in-furnace sound
at the time of misfire, respectively. In both figures, 100 Hz or less is an area ¦ region where air
flow noise dominates, and 200-400 Hz is an area ¦ region where combustion noise dominates.
From both figures, it can be understood that the airflow noise is several times larger than the
combustion noise and the S / N ratio is poor.
[0009]
The present invention has been made to solve this problem, and it suppresses the generation of
wind noise caused by the end of the probe, and there is no possibility that the probe itself
becomes a cause of disturbance, and in particular, high speed combustion air can be obtained. An
object of the present invention is to provide a sound sensor suitable for use in a device that
determines combustion / misfire (extinguishing) of a blow-in furnace based on the sound in the
furnace.
[0010]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is
directed to a sound sensor for directing a tip of a cylindrical probe provided with a sound intake
port to a sound source and guiding the sound to the sensor main body. In the above, the tip of
the probe is a cone, and a sound intake port is formed near the cone or the cone.
A second aspect of the present invention is characterized in that the conical portion has an
inclined slope inclined with respect to the axial direction, and a sound intake port is formed on
the inclined end face. According to the third aspect of the present invention, the sound intake
port is composed of a plurality of pores aligned in the circumferential direction or the axial
direction. A fourth aspect is characterized in that at least a portion of the sound inlet is covered
with a net.
[0011]
As a result, since the tip of the probe is formed in a cone shape, the disturbance of the fluid due
to the tip portion of the probe is small even when it is exposed to the air flow, and the possibility
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that the probe itself causes the disturbance of the sensor is reduced.
[0012]
Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, the probe 41 is different from the conventional probe 21 in that the airflow noise
reduction tip 42 is attached to the tip of the probe main body 41A. The probe 41 is connected to
the sensor body 23 described above.
[0013]
As shown in FIGS. 2 and 3, the air flow noise reduction chip 42 has a shape in which the
connecting cylindrical portion 45 extends from the rear end of the chip main body 44 which is a
conical portion 43 having a conical tip. One sound intake port 46 is opened on the
circumferential surface of the portion of the main body 44 other than the above-mentioned
conical portion 43, and a sound introduction hole 47 communicating with the connection
cylindrical portion 45 and the sound intake port 46 in the chip main body 44. Is formed. The
shape of the sound inlet 46 does not have to be circular, and may be oval or square.
[0014]
In the example of FIG. 1, although the connection cylinder 45 of the airflow noise reduction chip
42 is fitted inside the tip of the probe main body 41A and fixed with the heat resistant cement
49, a screw cylinder having the connection cylinder 45 with a screw surface In some cases, screw
connection is made to the probe main body 41A.
[0015]
When the probe 41 of the present embodiment is exposed near the tip of the burner 32 as
shown in FIG. 18, since the tip of the probe 41 is conical, there is a fear that the tip of the probe
disturbs the flow of the air flow significantly. Instead, the wind noise caused by the separation of
the air flow is suppressed.
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When the probe 41 is disposed in the furnace, it is desirable that the sound intake 46 be directed
in the direction of reducing wind noise.
[0016]
An example of a measurement result at the time of using a sound sensor provided with this probe
41 in a furnace which blows in combustion air at high speed is shown in Drawing 12 and
Drawing 13.
[0017]
(A) and (B) in FIG. 12 show the amplitude and frequency of the in-furnace sound at the time of
combustion, respectively, and (A) and (B) in FIG. 13 show the amplitude and frequency of the infurnace sound at the time of misfire, respectively.
It is understood that the air flow noise is significantly reduced and the S / N ratio is improved as
compared to the conventional case where the probe 41 is not used.
[0018]
The conical portion 43 has a conical shape, but may have a streamline shape, a conical shape or
a tapered shape so long as it does not disturb the air flow.
[0019]
FIGS. 4 and 5 show another embodiment of the present invention, in which the outer surface of
the main body 44 of the airflow noise reduction chip 42 is covered with a fine mesh wire mesh
48, the example of FIGS. It is different.
The wire mesh 48 is fixed by welding or heat resistant cement. In the example shown in FIGS. 2
and 3, turbulence may occur in the vicinity of the sound inlet 46 due to air flow around the
sound inlet 46 of the chip main body 44, etc. However, in the case of this embodiment, the sound
inlet Since the wire mesh 46 is covered with the wire mesh 48, it substantially becomes a
collection of small openings and the above-mentioned turbulence is alleviated.
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[0020]
As a result, not only the sound caused by the turbulence of the air flow due to the shape of the
probe end but also the sound caused by the turbulence of the air flow by the sound intake 46 are
reduced, the sound transmitted to the microphone 25 through the sound intake 46 The air flow
noise is reduced as compared with the case of using the chip 42 in the example of FIG.
[0021]
Further, in the case of the embodiment shown in FIGS. 4 and 5, the wire mesh 48 exhibits a
dustproof effect.
FIGS. 6 and 7 show a third embodiment of the present invention, in which the sound inlet 46 is
constituted by a plurality of small diameter holes (for example, about 1 mm) in the radial
direction 461 to 467. It is. The group of radial holes 461 to 467 shown in the drawing is
provided over the range of 90 ° in the circumferential direction, but the range of 60 ° to 120
° is preferable from the viewpoint of reducing air flow entrainment.
[0022]
FIG. 8 shows a fourth embodiment of the present invention, in which radial rows of holes 461 to
467 are provided in a plurality of rows in the axial direction (each row is indicated by 46N), and
FIGS. There is an advantage that the opening area of the sound inlet 46 can be made larger than
in the case of the above.
[0023]
FIGS. 9 and 10 show a fifth embodiment of the present invention, in which the conical portion 43
of the tip 42 is a conical portion having an inclined end face 43A inclined with respect to the
axial direction. The sound intake 46 is open at 43A.
The probe attached with the tip 42 is attached to the furnace wall with the inclined end face 43A
oriented along the direction of the air flow (indicated by a solid arrow).
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[0024]
FIG. 11 shows a sixth embodiment of the present invention, in which the tip of the probe main
body 41A is closed by the blind plug 50, and the sound intake 46 is formed in the probe main
body 41A. The blind plug 50 has a conical shape in the same manner as the tip 42.
[0025]
Further, the inner cylindrical surface of the probe main body 41A is covered with a heat
insulating material 51 and a sound absorbing material 52. Since the sound absorbing material 52
is present, only the sound from the sound intake 46 can be transmitted to the microphone 25.
The heat insulating material 51 may be omitted.
[0026]
As described above, according to the present invention, since the tip of the probe is formed in a
cone shape, the disturbance of the fluid due to the tip portion of the probe is small even when
exposed to the air flow, and the probe itself may cause noise. Since it lose ¦ eliminates, compared
with the past, the sound from a different sound source can be extracted distinguishably in high
accuracy. In particular, the present invention is suitable for use in a device that determines
combustion / misfire (extinguishing) of a furnace that blows combustion air at high speed by the
noise in the furnace.
[0027]
Brief description of the drawings
[0028]
1 is a longitudinal sectional view showing a first embodiment of the present invention.
[0029]
2 is a plan view of the chip in the above embodiment.
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[0030]
3 is a longitudinal sectional view of the chip.
[0031]
4 is a plan view of a chip showing a second embodiment of the present invention.
[0032]
5 is a cross-sectional view of the second embodiment.
[0033]
6 is a plan view of a chip showing a third embodiment of the present invention.
[0034]
7 is a cross-sectional view of the chip in the third embodiment.
[0035]
8 is a plan view of a chip showing a fourth embodiment of the present invention.
[0036]
9 is a plan view of a chip showing a fifth embodiment of the present invention.
[0037]
10 is a plan view of the chip in the fifth embodiment.
[0038]
11 is a cross-sectional view of a probe showing a sixth embodiment of the present invention.
[0039]
12 is a diagram showing the vibration amplitude and the frequency component of the in-furnace
sound at the time of combustion taken out from the sensor when the present invention is
implemented.
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[0040]
13 is a diagram showing the vibration amplitude and the frequency component of the in-furnace
sound at the time of misfire taken out from the sensor when the present invention is
implemented.
[0041]
<Figure 14> It is the figure which shows the relationship between the sound sensor and the
furnace in order to explain ignition detection method.
[0042]
15 is a cross-sectional view showing a probe of the conventional sound sensor.
[0043]
<Figure 16> It is the figure which shows the oscillation amplitude and the frequency component
of the sound inside the furnace at the time of combustion which is taken out from the
conventional sensor.
[0044]
<Figure 17> It is the figure which shows the oscillation amplitude and the frequency component
of the sound in the furnace at the time of the misfire which is taken out from the conventional
sensor.
[0045]
18 is a diagram showing the relationship between the sound sensor and the furnace for
explaining the ignition detection method.
[0046]
Explanation of sign
[0047]
DESCRIPTION OF SYMBOLS 10 flame 20 sensor 21 probe 21A probe tip 21B sound intake 23
sensor main body 25 microphone 30 industrial furnace 31 furnace wall 32 burner 41 probe 41
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A probe main body 42 tip 43 cone 43A inclined surface 44 tip main body 45 connection
cylindrical portion 46 sound intake Mouth 47 sound introduction hole 48 wire mesh 49 heat
resistant cement 50 blind plug 51 heat insulating material 52 sound absorbing material
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