JPH06300247A - Flame detecting method - Google Patents

Abstract

PURPOSE:To provide a flame detecting method, capable of being applied to both of oil burning and gas burning and capable of detecting the existence of the flame to be required for detection surely without being affected by the brightness in a furnace from the flame of other burners when a plurality of burners are arranged in parallel. CONSTITUTION:Light of incidence L is converted into a voltage signal V by a sensor 3 and a brightness component VO and flickering component VT are extracted by a filter 4 while the individual brightness of flame 1 is estimated employing the ratio of flickering/brightness 9 of the individual flame, then, the flickering component VT is corrected utilizing a difference between the moving average VO1 and the brightness component VO as brightness component VO2 in a furnace while the corrected flickering component VT1 is compared with a reference value VT0 to decide the existence of the flame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame detecting method, and more particularly to a transparent flame presence detecting method.

[0002]

2. Description of the Related Art For example, in the case of a large boiler, 30 to 60 combustors (burners) of a boiler are juxtaposed in one boiler, and each burner is provided with a flame detector for detecting a flame. Is detected and the operation of the burner is controlled. For the detection of such flame, in the case of a gas flame using gas as a fuel, an ultraviolet detector for detecting the presence or absence of the flame by detecting, for example, ultraviolet rays having a wavelength of 0.2 to 0.3 μm emitted from the gas flame. Was used. However, in such an ultraviolet detector, the detector deteriorates in a short period of time (for example, within one year) due to dirt, cloudiness, etc. on the detection tube (usually made of transparent glass), and the detection performance changes so that it is stable for a long period of time. There was a problem that could not be used. Further, due to the deterioration of the detector, the maintenance cost has to be high because it must be replaced frequently. Further, in this detector, since ultraviolet rays are greatly attenuated by the water vapor in the flame, there is a problem that the accuracy varies greatly depending on the water vapor content. In addition, because the flame of oil combustion hardly generates ultraviolet rays, the same detector cannot be used, and when oil combustion and gas combustion are used together, different types of detectors are provided, each with a separate control device. Had to prepare.
Therefore, conventionally, there has been a demand for flame detection means applicable to both oil combustion and gas combustion.

[0003]

On the other hand, a method of detecting the flame from the flicker of the flame has been conventionally used for detecting the flame of oil combustion. However, with a gas flame, the flame hardly glows, has little flicker, and is transparent. Therefore, the flame to be detected (hereinafter referred to as self-flame)
Even if disappears, if the inside of the furnace is bright due to the flames of other burners arranged side by side, it will be detected brightly, and conversely, even if the self-flame is burning, it will be detected very dark when the other burners disappear. there were. Therefore, in the conventional method of detecting the flame from the flicker, malfunction is likely to occur, and stable flame detection cannot be performed. Besides, the flicker of the flame itself
There was a problem that when the inside of the furnace became bright due to the combustion flame of another burner, it became relatively small. Therefore, the brightness and flicker of the flame to be detected are greatly affected by the combustion flames of other burners, and it is almost impossible to detect the self-flame by the conventional method.

The present invention was devised to solve such problems. That is, the object of the present invention is applicable to both oil combustion and gas combustion, and when a plurality of burners are juxtaposed, the presence or absence of self-flame is not affected by the brightness in the furnace due to the flames of other burners. It is to provide a flame detection method capable of stably and accurately detecting a flame.

[0005]

DISCLOSURE OF THE INVENTION
Flickering is flickering in self-flames with a narrow field of view.
Clear, flicker in wide field of view, for example, oncoming flame
I got a new finding that is almost invisible. this
Activated gas glows in the flame, and this mass
It fluctuates and moves, so in self-flames with a narrow field of view, flickering
However, in an oncoming flame with a wide field of view,
Because a small number of small blocks can be seen at the same time, they are averaged and
It is thought that it is flickering and invisible. Furthermore, the invention
The brighter is the ratio of the brightness of the flame to the flicker in a single flame.
The rate is almost constant regardless of the fuel and the amount of combustion.
I obtained new knowledge. This ratio is, for example, in the case of a gas flame.
1 to 2% in the case of oil flame and about 5% in the case of oil flame
It The present invention was devised based on such new findings.
Of. That is, according to the present invention, the incident light L is
Convert it into a voltage signal V, and use a filter to output the brightness component V _OWhen
Flicker component V_TExtracts the flicker / brightness of a single flame
The brightness of the flame 1 alone_O1And then
Moving average and brightness component V_ODifference of the brightness component V in the furnace
_O2As flicker component V_TCorrected and corrected
Ingredient V_T1And reference value V_T0To determine if there is a flame.
A flame detection method is provided.

[0006]

The flicker of the transparent flame becomes relatively small when the inside of the furnace becomes bright due to the combustion flame of another burner. However, as described above, the flicker / brightness ratio of the single flame is 1 to 2% in the case of the gas flame, and is almost constant. Therefore, with the above-described configuration of the present invention, the brightness component V _O and the flicker component V _T of the incident light L are extracted, and the flicker / brightness ratio of the single flame is made constant, and the single brightness V _O1 of the self-flame 1 is obtained. Can be estimated. Then, the flicker component V _T1 of the single flame can be obtained by correcting the flicker component V _T by setting the difference between the single brightness V _O1 of the flame 1 and the actual brightness V _O as the brightness component V _O2 in the furnace. Therefore, the presence or absence of the flame can be determined by comparing the flicker component V _{T1 of the} corrected single flame with the reference value V _T0 .

[0007]

The principle of the present invention will be described below with reference to the drawings and formulas.
Reveal Figure 2 converts incident light from a flame into an electrical signal
10 is an example of a circuit that includes avalanche photo da
Iode, 11 is a logarithmic conversion circuit, 12 is a voltage amplification circuit
Shows. Avalanche photo diode 10
Disperses the incident light from the flame (radiant flux of light L (W))
Photo current i_cConvert to (A). This photocurrent i
_cIs i_c= NηL ... here
Where n is the multiplication factor and η is the conversion efficiency (A / W). Multiplication
The rate n is the photocurrent i_c(A) compared to the noise of the stray current
It is set so that it will be a sufficiently large value.
Is processed in the constant C of. Also, the logarithmic conversion circuit 1
1 is the photocurrent i_cLogarithmically converted to voltage V_DConverted to
Brightness voltage V_DIs V_D= K_Tln (i_c/ I_S) ・ ・ Expression
You can Where K_T= ΚT / q (semiconductor characteristic formula)
And κ is the Boltzmann constant (1.381 × 1
0^{-twenty three}), T is absolute temperature (about 300K at room temperature), q is
Charge (1.602 × 10 ^-19Coulomb)
R, K_T= 2.586 × 10^-2Can be regarded as a constant of
Wear. Also, I in the formula_SIs the reverse saturation current
It Further, the voltage amplifier circuit 12 has the voltage V_DBrightness voltage
Amplified to V (magnification a), V = aV_D..Expression can be expressed. formula,
, The multiplication factor n is 30 times, and the amplification factor a is 22.7.
If it is doubled, V = a · K_Tln (nηL / I_S) = 0.587lnL
+ C ... Expression. Here, C is a constant. flame
The incident light (radiant flux L of light) from is constant brightness L_oWhen
Flickering l_TAnd L = L_o+1_TAppears
Then, from the formula, V = 0.587lnL_o+ C + 0.587ln (1 + l
_T/ L_o) ... The constant C in the expression is
It can be set to zero by adjusting the zero point of the road output. Therefore,
Brightness L_oDC component V of voltage V corresponding to_oFlickering
L_TAC component V of voltage V corresponding to_TIs V_O= 0.
587lnL_o, V_T= 0.587ln (1 + 1_T/ L
_o), And from these two equations, V_T≈ 0.587 (l_T/ L_o) = 0.587 (l_T/5.5^VO) ・ ・ Expression, is obtained.

As described above, the ratio of brightness and flicker of a flame in a single flame is substantially constant, and this ratio is 1 to 2% in the case of a gas flame, for example. Also,
Since the brightness of the self-flame is almost constant in a short time, the flicker l _T in a short time can be regarded as almost constant. Compared with this, the brightness and flicker of the self-flame during lighting and extinguishing change rapidly. From the formula, l
_{If T} is constant, the relationship between the DC component V _o and the AC component V _T as shown in FIG. 3 is obtained. In this figure, point 1
Indicates a single flame, in which case V _O1 corresponds to the brightness of the single flame, and V _T1 corresponds to flicker.
_T1 is about 0.01 V when the amplification factor is a. Also,
Point 2 corresponds to a state where the inside of the furnace is brightened by the combustion flames of other burners arranged side by side, and the direct current component V _o of the brightness becomes large due to the addition of the brightness V ₀₂ inside the furnace, and an AC component V _T of the voltage V corresponding to the flicker l _T alone flame simultaneously decreased by the formula in the brightness effect of the furnace. In FIG. 3, the flame to be detected (called self-flame) is burning, and many other flames are burning. In the normal case, the voltage V obtained from the above-mentioned circuit
The DC component V _o and the AC component V _{T of} are at the position of point 2 in the figure. In this state, the obtained DC component V _{o of the} voltage V
And the AC component V _T , based on the formula, the AC component V _T1 of the individual flame 1 is separated into a DC component V _{02 corresponding} to the brightness of the individual flame and the brightness in the furnace so that the AC component V _T1 becomes 0.01 V. You can This learning is performed, for example, every 0.25 seconds, and the moving average value of the brightness of the individual flame for 3 minutes is stored as V ₀₁ . Then, even though the self-flame is burning, when some of the other burners disappear, this state corresponds to, for example, point 3 on the solid line in the figure, and the overall brightness is detected as dark. A DC component V _o of this state in the detected voltage V, to calculate the brightness of the furnace from the moving average brightness of a single flame learned and to correct the AC component V _T, for example, as shown in 1 ' , AC component V _T1 is 0.
It is corrected to the vicinity of 01V. On the contrary, when the self-flame disappears in the bright state of the furnace due to the combustion flames of the other burners arranged side by side, the AC component V _T corresponding to the flicker becomes a little small, as shown by point 4 in the figure, for example. The brightness V _o is detected with almost no change. However, in the absence of self-flame, because there is almost no flicker, the DC component V _o and an AC component V _T of the voltage V detected in this state,
When the corrected moving average value V ₀₁ of the brightness of the individual flame is corrected based on the equation, for example, as shown in 1 ″, the AC component V
_T1 becomes smaller than 0.01V of single flame 1. Even at this time, the correction value of the AC component V _T1 is learned so that the flicker of the individual flame becomes 0.01 V, and the operation of restoring the flicker reduction by correction is continued, but the time constant of the moving average is 3 Because it is a long time, it is possible to continue detecting fire extinguishing several times before restoring. Therefore, the brightness V in the furnace where the learned DC component V _o and AC component V _T of the detected voltage V are learned
It is possible to determine the presence or absence of flame by correcting the flicker by ₀₂ and making it closer to a certain level of flicker and comparing this with a reference value (for example, 0.01 V). This is the principle of the present invention.

FIG. 1 is a block diagram showing the method according to the invention.
It is a diagram. In this figure, 1 is self-flame, 2 is boy
In the furnace, 3 is a photo sensor, 4 is a filter, and 5 is calculation.
Circuit, 6 is a difference circuit, 7 is a correction circuit, and 8 is a comparison circuit.
It The photo sensor 3 is the avalanche photo described above.
.Diode 10, logarithmic conversion circuit 11, and voltage amplification circuit
It consists of the path 12 and converts the incident light L from the flame into a voltage signal V.
Replace. Further, the filter 4 converts the voltage signal V into the DC component V
_oAnd AC component V_TTo extract. Furthermore, the arithmetic circuit 5 is
Flow component V_oAnd AC component V_TBased on the formula, a single flame
AC component V of 1 _T1DC of a single flame with a voltage of 0.01 V
Calculate the component and calculate its moving average V_O1Is calculated. Also the difference
The divider circuit 6 has a moving average V of the DC component._O1And brightness component V_Oof
Brightness component V in the furnace_O2Ask as. Furthermore, the correction times
The path 7 has a brightness component V_O2Flicker component V_TCorrected
Flickering component V of single flame 1_T1Ask for. Also compare
The circuit 8 uses the corrected fluctuating component V_T1And reference value V_T0When
To determine if there is a flame and output a control signal
It is like this. With this configuration, the method of the present invention
According to this, the photo sensor 3 supplies the incident light L to the sensor.
The brightness component V is converted by the filter 4 into the pressure signal V._OWhen
Flicker component V_TIs extracted and the independent flame is calculated by the arithmetic circuit 5.
A single brightness of flame 1 with a flicker / brightness ratio of 9
Moving average V_O1And the difference circuit 6 calculates a single
Rusa's moving average V_O1And brightness component V_ODifference V_O2Seeking
V by the correction circuit 7_O2Is the brightness component V in the furnace_O2Tochichi
Rattle component V_TWas corrected and corrected by the comparison circuit 8.
Flicker component V_T1And reference value V_T0Compared with
Judge nothing. The flicker / brightness ratio of the single flame is
Usually, it is 1 to 2%, and from this, the amplification factor a is 2
2.7 times, the flicker component V of the single flame_T1Is
It is 0.006-0.012V. Therefore, the reference value
V_T0Is set to 0.006V, for example, and is corrected by the comparison circuit 8.
Shattering component V_T1Is the reference value V_T0In the following cases,
It can be determined that the flame is extinguished. The above theory
Ming explained the gas-fired flame, but this method
It can be applied to flame flames and coal flames as well.
It For example, in the case of oil-fired flame, the flicker of the single flame
/ Brightness ratio is usually about 5%.
It is possible to detect the presence or absence of flame by the method. In addition,
The avalanche photodiode was used in the above description.
But the large photocurrent i_c, The amplification factor n = 1
The photodiode of can be used. Which one to use
Even if there is, it does not affect the expression by processing the constant C of the expression.
This is as already mentioned.

[0010]

As described above, the flicker of the transparent flame is caused when the inside of the furnace becomes bright due to the combustion flame of another burner.
It becomes relatively small. However, as described above, the flicker / brightness ratio 9 of a single flame is 1 to 2% in the case of a gas flame.
And is almost constant. Therefore, according to the above configuration of the present invention, the brightness component V _O and the flicker component V _T of the incident light L are
Can be extracted, and the independent brightness V _O1 of the self-flame 1 can be estimated by _keeping the flicker / brightness ratio of the individual flame constant. Next, the flicker component V _T1 of the single flame is corrected by correcting the flicker component V _T with the difference between the single brightness V _O1 of the flame 1 and the actual brightness V _O as the brightness component V _O2 in the furnace.
The flicker component V _{T1 of the} corrected single flame can be compared with the reference value V _T0 to determine the presence or absence of the flame.

Therefore, the method of the present invention can be applied to both oil combustion and gas combustion, and is independent of the brightness in the furnace due to the flames of other burners when a plurality of burners are juxtaposed. Moreover, it has an excellent effect that the presence or absence of self-flame can be detected stably and accurately.

[Brief description of drawings]

1 is a block diagram illustrating a method according to the present invention.

FIG. 2 is a circuit diagram for converting incident light from a flame into an electric signal.

FIG. 3 is a diagram showing a relationship between a flame DC component V _o and an AC component V _T.

[Explanation of symbols]

1 Self-flame 2 Boiler furnace 3 Photo sensor 4 Filter 5 Calculation circuit 6 Difference circuit 7 Correction circuit 8 Comparison circuit 9 Single flame flicker / brightness ratio 10 Avalanche photo diode 11 Logarithmic conversion circuit 12 Voltage amplification circuit L Incident light V Voltage signal V _O Brightness component V _T Flicker component V _O1 Single brightness of flame V _{O2 In-} furnace brightness component V _T1 Corrected flickering component V _T0 Standard value of flickering component

Claims (4)

[Claims] 1. A sensor converts incident light L into a voltage signal V, a filter extracts a brightness component V _O and a flicker component V _T, and a flicker / brightness ratio of a single flame is used to calculate a flame 1
Of the independent brightness V _O1 is estimated, the difference between the moving average and the brightness component V _O is used as the brightness component V _O2 in the furnace to correct the flicker component V _T, and the corrected flickering component V _T1 and the reference value. V
A flame detection method, which comprises comparing with _T0 to determine the presence or absence of a flame. 2. The flicker / brightness ratio of the individual flame is
It is 1-2%, The flame detection method of Claim 1 characterized by the above-mentioned. 3. The sensor is an avalanche photo sensor.
The flame detection method according to claim 2, comprising a diode, a logarithmic conversion circuit, and a voltage amplification circuit. 4. The amplification factor a in the sensor is 22.
7 times, and the flicker component V _T1 of the single flame is 0.0
It is 06-0.012V, It is characterized by the above-mentioned.
Flame detection method described in.