CN111487171B - Forward and backward combined dual-wavelength dispersed fire smoke detection method - Google Patents
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Abstract
The invention discloses a forward and backward combined double-wavelength dispersed fire smoke detection method, wherein a detector comprises a detection cavity, a light wave receiver and two light wave transmitters are arranged in the detection cavity, and an included angle between one transmitting tube and the receiver is an acute angle and is a forward transmitting tube; the included angle between the other transmitting tube and the receiver is more than 120 degrees, and the other transmitting tube is a backward transmitting tube; the two transmitting tubes sequentially transmit two light wave signals of blue light and red light, the two light wave signals are received by the receiving tube, the median particle size of smoke is judged by using the scattering power of the backward transmitting tube, and then whether smoke alarm is sent or not is judged by using the forward transmitting tube according to the median particle size of the smoke. The invention adopts the blue light and the red light emitted by the same double-color light emitting tube to judge the concentration of the particles, eliminates the influence of uncertain factors of the light emitting characteristics and the installation angle among different light emitting tubes, eliminates the problem of aging difference of different light emitting tubes due to long-term use, and greatly improves the precision and the anti-interference capability of smoke alarm.
Description
Technical Field
The invention belongs to the field of smoke detectors, relates to an optical detector, and particularly relates to a forward and backward combined dual-wavelength dispersed fire smoke detection method.
Background
In the current products based on the optical detection mode, the sensitivity of smoke particles with different colors, such as white smoke and black smoke, is not balanced; or the interference of water vapor, oil smoke and dust cannot be distinguished, and frequent false alarm is caused. Patent (CN 201510861356.9) scattered light smoke detector with two-color light emitting diodes describes a smoke detector device using a single two-wavelength light emitting diode and a single photoreceptor, which uses a single scattering angle, forward or backward, to evaluate the particle size of the detected smoke particles by a suitable evaluation (such as, for example, a ratio calculation) of the scattered light of the respective color received by the photoreceptor, to distinguish between smoke, dust and vapor. The patent has no way to distinguish white smoke or black smoke, and the sensitivity of the smoke detector cannot be kept balanced and stable for different types of fire smoke, so that the phenomenon that the sensitivity of the smoke detector is too high for white smoke and the sensitivity of the smoke detector is too low for black smoke is often caused.
In the patent (CN 201410748629.4) an aerosol particle size sensing method based on dual-wavelength dispersion signals and its application in fire smoke detection, it is proposed to measure the dispersion signals under two wavelengths, and determine the median particle size of aerosol particles by performing ratio operation on the received scattered light power; and determining whether a fire alarm signal should be issued by threshold comparison of the scattered light power. The device and the method are composed of two transmitting tubes with different wavelengths and a receiving tube with dual-wavelength receiving capability, wherein the scattering angle of blue light is 120 degrees, and the scattering angle of infrared light is 30 degrees. Since the forward scattering power and the backward scattering power per se vary with the particle size even in the same wavelength light source, it is very inaccurate to calculate the median particle size by the ratio of the backward scattering power of blue light to the forward scattering power of red light.
Patent (CN 201711415845.7) a method for detecting smoke in early fire with interference particle recognition capability proposes to arrange a dual-wavelength transmitter and two receivers in a detection chamber structure of a detector, wherein the two receivers collect scattered light power at different angles, one is a forward scattering angle, and the other is a backward scattering angle. The ratio (asymmetry ratio) of the scattered light power of two different angles is calculated by measuring the scattered light power, and the early detection of the fire smoke particles is realized by analyzing the fluctuation characteristic of the asymmetry ratio. The method has the disadvantages that because two receivers are adopted, the uncertainty of the asymmetric ratio is increased due to the difference between the photoelectric conversion efficiencies of the two receivers, the uncertainty can not be effectively eliminated, and the actual effect of distinguishing different particles and alarming fire by adopting the fluctuation characteristics is greatly weakened.
Disclosure of Invention
The invention solves the problem that the sensitivity of the existing products based on the optical detection mode is not balanced for white smoke and black smoke, such as smoke particles with different colors; or the interference of water vapor, oil smoke and dust cannot be distinguished, and frequent false alarm is caused. The invention provides a forward and backward combined dual-wavelength dispersed fire smoke detector and a method, which adopt alternative forward and backward scattering and alternative detection methods of two different wavelengths, can accurately identify the particle diameter, have very good interference elimination capability on water vapor, oil smoke and dust, have quite balanced and consistent sensitivity performance on smoke dust of various colors, simultaneously can avoid deviation caused by aging factors of different transmitting tubes, different installation angles and different transmitting tubes, and greatly improve the robustness of products.
In order to solve the technical problems, the invention adopts the technical scheme that:
a fire smoke detection method of dual wavelength dispersion combined with forward and backward is characterized in that a light wave receiver and two light wave transmitters are arranged in a detection cavity, each light wave transmitter is a transmitting tube capable of transmitting light waves with red and blue wavelengths, the light wave receiver is a receiving tube capable of receiving corresponding wavelengths, and an included angle between one transmitting tube and the receiver is an acute angle and is a forward transmitting tube; the fire smoke detection method is characterized in that the fire smoke detection method comprises the following specific steps:
step 1, under the smokeless condition, sequentially starting two transmitting tubes, wherein each transmitting tube respectively transmits red and blue light waves, and when the transmitting tubes transmit blue light, the bottom current intensity detected by a receiving tube is recorded as p BBD When the red light is emitted to the transmitting tube, the intensity of the bottom current detected by the receiving tube is recorded as p RBD When the forward emitting tube emits blue light, the bottom current intensity detected by the receiving tube is recorded as p BFD When the forward emitting tube emits red light, the bottom current intensity detected by the receiving tube is recorded as p RFD ；
when the median diameter of the smoke particles is greater than a constant value d 2 Judging whether the alarm concentration is reached or not by the scattering intensity of red light emitted by the forward emitting tube;
when the median diameter of the smoke particles is between the constant value d 1 And a constant value d 2 And in the meantime, whether the smoke reaches the alarm concentration or not is judged by the combination of the scattering intensity of the red light and the blue light emitted by the forward emitting tube.
Further, the air conditioner is provided with a fan,
the specific judgment method for the median particle size of the smoke in the step 3 is as follows:
step 3.1, calculating the scattering ratio of the backward emission tube after emitting blue light and red light
Defining a scattered light intensity ratio threshold TH L And TH H ；
Step 3.2, if N<TH L Then the median particle diameter of the smoke particles is known to be less than the constant value d 1 ；
Step 3.3, if TH L ≤N≤TH H Then, the median diameter of the smoke particles is known to be at a constant value d 1 And a constant value d 2 To (c) to (d);
step 3.4, if N>TH H The median particle diameter of the aerosol particles is then greater than the constant value d 2 ；
Step 3.5, if N > TH H Then, it means that the median diameter of the smoke particles is far greater than the constant value d 2 There is a large particle disturbance.
Further, the scattered light intensity ratio threshold value TH L And TH H Determined by previously setting smoke particles of known median size in a laboratory environment.
Further, scatteringLight intensity ratio threshold TH L The value is 0.4-0.6, and the scattered light intensity ratio threshold value TH H The value range is 1.4-1.8.
Further, in the step 4, when the median diameter of the particles is less than the constant value d 1 While the forward emission tube emits a scattering intensity p of blue light B ＝p BF -p BFD If p is B Greater than a set threshold TH FB If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out.
Further, in the step 4, when the median diameter of the smoke particles is larger than a constant value d 2 The forward emission tube emits the scattering intensity p of red light R ＝p RF -p RFD If p is R Greater than a set threshold TH FR If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out;
when the median diameter of the smoke particles is much greater than d 2 When it is, p is judged R Whether or not it is greater than the saturation threshold TH FR' If the smoke concentration is greater than the alarm concentration, the alarm of the smoke concentration is sent out; otherwise, the smoke concentration alarm is not sent out.
Further, in the step 4, when the median diameter of the smoke particles is between the constant value d 1 And a constant value d 2 In the meantime, whether the smoke reaches the alarm concentration is judged by the combination of the scattering intensity of the red light and the blue light emitted by the forward emitting tube, and the combined scattering intensity p = p B +m*p R And if p is greater than the set combined threshold TH, the alarm concentration is reached, and a smoke concentration alarm is sent out, wherein m is a correction factor.
Further, the threshold TH FB Threshold TH FR Saturation threshold TH FR' And the combined threshold TH is set by laboratory measurement according to the alarm time and concentration required by the national standard.
Furthermore, the value range of the correction factor m is 0.3-0.8.
Further, constant value d 1 In the range of 350-450nm, constant value d 2 The range is 750-850.
The utility model provides a fire smoke detector of preceding dual wavelength dispersion that combines with backward, is including surveying the cavity, its characterized in that: the smoke alarm device is characterized in that a light wave receiver and two light wave transmitters are arranged in the detection cavity, each light wave transmitter is a transmitting tube capable of transmitting light waves with two wavelengths of red and blue, the light wave receiver is a receiving tube capable of receiving light waves with corresponding wavelengths, and an included angle between one transmitting tube and the receiver is an acute angle and is a forward transmitting tube, and the forward transmitting tube is used for judging a scattering intensity threshold value so as to judge whether smoke alarm is performed or not; and the included angle between the other transmitting tube and the receiver is more than 120 degrees, and the other transmitting tube is a backward transmitting tube and is used for judging the median particle size of the smoke.
The invention has the beneficial effects that:
the invention utilizes the difference characteristics of the scattering effect of the dual-wavelength and the forward and backward directions to different particle diameters, judges the average diameter of the particles through the received light intensity of different wavelengths and different angles, and accordingly adopts different judgment methods and thresholds to alarm fire and alarm obvious interfering particles.
(1) And a single receiving tube and an amplifying circuit are adopted, the unbalanced difference of multiple receiving circuits does not need to be considered, and the robustness is strong.
(2) The ratio of blue light to red light emitted by the same double-color light-emitting tube is adopted to judge the range of the average diameter of the particles, and the influence of uncertain factors of the light-emitting characteristics and the installation angle among different light-emitting tubes is eliminated.
(3) The concentration of the particles is judged by adopting the blue light and the red light emitted by the same double-color light-emitting tube, so that the influence of uncertain factors of the light-emitting characteristics and the installation angle among different light-emitting tubes is eliminated.
(4) The same light-emitting tube is adopted for discrimination, so that the problem of difference of aging of different light-emitting tubes due to long-term use can be solved.
(5) Determining the median of the particle diameters of the particles by using the stability of the back scattering power; and the characteristic of high forward scattering power is utilized to judge the particle concentration.
(6) When the particle concentration is between the blue and red wavelengths, a joint determination is made using the red and blue light.
Drawings
Fig. 1 is a schematic view of a fire smoke detector according to an embodiment of the present invention.
1-detection cavity, 2-forward transmitting tube, 3-backward transmitting tube and 4-receiving tube.
Detailed Description
As shown in fig. 1, the present invention provides a fire smoke detector, which includes a detection cavity 1, wherein a receiving tube 4 and two transmitting tubes are arranged inside the detection cavity 1, each of the light wave transmitters is a transmitting tube capable of transmitting light waves with two wavelengths, the light wave receiver is the receiving tube 4 capable of receiving corresponding wavelengths, an included angle between one transmitting tube and the receiver is an acute angle (such as 80 degrees), and the included angle is a forward transmitting tube 2 and is marked as a position a, which is used for judging a scattering intensity threshold value, so as to judge whether to alarm smoke; the other transmitting tube has an included angle with the receiver of more than 120 degrees (for example, 140 degrees), is a backward transmitting tube 3, is marked as a position B, and is used for judging the median particle size of the smoke.
The two paths of emitting tubes (the LED light emitting chips can be selected) can be provided with different emitting currents, the receiving circuit of one path of receiving tube 4 is provided with a proper amplification factor, the receiving tube 4 converts the received light intensity into current according to the received light intensity, so that the received light intensity can be known by measuring the current generated by the receiving tube 4, and for the selected receiving tube 4, the received light intensity can be obtained by measuring the current according to a fixed proportional relation.
The method for detecting smoke by using the fire smoke detector in the embodiment comprises the following steps:
step 1, under the smokeless condition, starting two transmitting tubes to respectively transmit red and blue light waves, and recording the bottom current intensity detected by a receiving tube 4 as p when the transmitting tubes 3 transmit blue light to the rear BBD When the red light is emitted to the emission tube 3, the intensity of the bottom current detected by the receiving tube 4 is recorded as p RBD When the forward transmitting tube 2 transmits blue light, the intensity of the bottom current detected by the receiving tube 4 is recorded asp BFD When the forward transmitting tube 2 transmits red light, the intensity of the bottom current detected by the receiving tube 4 is recorded as p RFD ；
step 3.1, calculating the scattering ratio of the backward transmitting tube 3 after transmitting the blue light and the red light
Defining a scattered light intensity ratio threshold TH L And TH H ；
Step 3.2, if N<TH L Then the median particle diameter of the smoke particles is known to be less than the constant value d 1 ；
Step 3.3, if TH L ≤N≤TH H Then, the median diameter of the smoke particles is known to be at a constant value d 1 And a constant value d 2 In the middle of;
step 3.4, if N>TH H The median particle diameter of the aerosol particles is then greater than the constant value d 2 。
Step 3.5, when N > TH H Then, it means that the median diameter of the smoke particles is far greater than the constant value d 2 Interfering particles, such as water vapor or dust, may be present.
Two thresholds d of median particle diameter 1 And d 2 Generally measured in a laboratory environmentTo obtain, the constant value d of this embodiment 1 In the range of 350-450nm, constant value d 2 In the range 750-850, depending on the wavelength emitted by the corresponding emitter tube.
The scattered light intensity ratio threshold value TH L And TH H Determined by previously setting smoke particles of known median size in a laboratory environment.
Scattered light intensity ratio threshold TH L The value is 0.4-0.6, and the scattered light intensity ratio threshold value TH H The value range is 1.4-1.8.
step 4.1, when the median diameter of the particles is less than a constant value d 1 While the forward emission tube 2 emits a scattering intensity p of blue light B ＝p BF -p BFD If p is B Greater than a set threshold TH FB If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out.
Step 4.2, when the median diameter of the smoke particles is larger than a constant value d 2 While the forward emission tube 2 emits a scattering intensity p of red light R ＝p RF -p RFD If p is R Greater than a set threshold TH FR If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out.
Step 4.3, when the median diameter of the smoke particles is between a constant value d 1 And a constant value d 2 In the meantime, whether the smoke reaches the alarm concentration is judged through the combination of the scattering intensity of the red light and the blue light emitted by the forward emission tube 2, and the combined scattering intensity p = p B +m*p R And if p is greater than the set combined threshold TH, the alarm concentration is reached, and the smoke concentration alarm is sent out, wherein m is a correction factor, and the value range of the correction factor m is 0.3-0.8.
Step 4.4, when the median diameter of the smoke particles is far larger than d 2 While the forward emission tube 2 emits a scattering intensity p of red light R ＝p RF -p RFD If p is R Greater than a set saturation threshold TH FR' Then the alarm is strongAnd (4) sending out a smoke concentration alarm; otherwise, the smoke concentration alarm is not sent out.
The threshold TH FB Threshold TH FR Combined threshold TH and saturation threshold TH FR' The four thresholds correspond to four different average particle diameters, in this embodiment, the four thresholds are set according to alarm time and concentration requirements required by national standards, according to 4 typical experimental fires and 2 interference sources (water vapor and 1um particulate matter) defined in GB20517-2006, change curves of forward and backward and red and blue light heat radiation intensities in the 4 experimental fires and the 2 interference sources are recorded.
For the above threshold value, one embodiment of the present invention is to make the light conversion current of the receiving tube 4 flow through a precision resistor (usually 1 mega ohm), measure the current by measuring the voltage difference between two ends of the resistor, and then amplify the weak voltage value, usually 30-60 times, according to the performance of different receiving tubes 4, and then set the threshold value, threshold TH FR A value of about 0.2V and a threshold TH FB The value is about 0.1V (generally 0.08-0.12V), the combined threshold TH is generally about 0.15V (generally 0.13-0.18V), and the saturation threshold TH FR' About 0.6V, generally between 0.4 and 0.8V.
Claims (6)
1. A fire smoke detection method of dual wavelength dispersion combined with forward and backward is characterized in that a light wave receiver and two light wave transmitters are arranged in a detection cavity, each light wave transmitter is a transmitting tube capable of transmitting light waves with red and blue wavelengths, the light wave receiver is a receiving tube capable of receiving corresponding wavelengths, and an included angle between one transmitting tube and the receiver is an acute angle and is a forward transmitting tube; the included angle between the other transmitting tube and the receiver is more than 120 degrees, and the other transmitting tube is a backward transmitting tube, and the fire smoke detection method is characterized by comprising the following specific steps:
step 1, under the smokeless condition, sequentially starting two transmitting tubes, wherein each transmitting tube respectively transmits two red and blue light waves, and when the transmitting tubes transmit blue light, the intensity of bottom current detected by a receiving tube is recorded as p BBD When the red light is emitted to the transmitting tube, the intensity of the bottom current detected by the receiving tube is recorded asp RBD When the forward transmitting tube transmits blue light, the intensity of the bottom current detected by the receiving tube is recorded as p BFD When the forward transmitting tube transmits red light, the intensity of the bottom current detected by the receiving tube is recorded as p RFD ；
Step 2, in the smoke detection environment, opening the backward emission tube at intervals of T, sequentially emitting blue light and red light, recording the receiving intensity of the receiving tube, and recording the receiving intensity as p BB And p RB (ii) a The intensity of reception of the receiver tube, denoted p, is recorded immediately after the forward-emitting tube has been switched on, likewise after the blue light has been emitted and the red light has been emitted BF And p RF ；
Step 3, the scattering power of the backward transmitting tube with uniform power is utilized to judge the median diameter of the smoke, two thresholds exist in the median diameter of the smoke, and the two thresholds are respectively a constant value d 1 And a constant value d 2 Wherein d is 1 <d 2 ；
Step 4, judging the scattering intensity threshold value by using a forward transmitting tube with strong scattering power, and when the median particle size of the smoke is smaller than a constant value d 1 Judging whether the alarm smoke concentration is reached or not by using the blue light scattering intensity threshold of the forward emission tube;
when the median diameter of the smoke particles is greater than a constant value d 2 Judging whether the alarm concentration is reached or not by the scattering intensity of red light emitted by the forward emitting tube;
when the median diameter of the smoke particles is between the constant value d 1 And a constant value d 2 In the meantime, whether the smoke reaches the alarm concentration is judged by the combination of the scattering intensity of the red light and the blue light emitted by the forward emitting tube;
the specific judgment method for the median particle size of the smoke in the step 3 is as follows:
step 3.1, calculating the scattering ratio of the backward emission tube after emitting blue light and red light
Defining a scattered light intensity ratio threshold TH L And TH H ；
Step 3.2, if N is less than TH L Then the median particle diameter of the smoke particles is known to be less than the constant value d 1 ；
Step 3.3, if TH L ≤N≤TH H Then, the median diameter of the smoke particles is known to be at a constant value d 1 And a constant value d 2 To (c) to (d);
step 3.4, if N > TH H The median particle diameter of the aerosol particles is then greater than the constant value d 2 ；
Step 3.5, if N > TH H Then, it means that the median diameter of the smoke particles is far greater than the constant value d 2 Large particle interference is present;
in the step 4, when the median diameter of the particles is less than the constant value d 1 While the forward emission tube emits a scattering intensity p of blue light B ＝p BF -p BFD If p is B Greater than a set threshold TH FB If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out;
when the median diameter of the smoke particles is greater than a constant value d 2 While the forward emission tube emits a scattering intensity p of red light R ＝p RF -p RFD If p is R Greater than a set threshold TH FR If the alarm concentration is reached, the smoke concentration alarm is sent out; otherwise, the smoke concentration alarm is not sent out;
when the median diameter of the smoke particles is much greater than d 2 When it is, p is judged R Whether or not it is greater than the saturation threshold TH FR' If the smoke concentration is greater than the alarm concentration, the alarm of the smoke concentration is sent out; otherwise, the smoke concentration alarm is not sent out;
when the median diameter of the smoke particles is between the constant value d 1 And a constant value d 2 In the meantime, whether the smoke reaches the alarm concentration is judged by the combination of the scattering intensity of the red light and the blue light emitted by the forward emitting tube, and the combined scattering intensity p = p B +m*p R If p is larger than the set joint threshold TH, the alarm concentration is reached, and a smoke concentration alarm is sent out, wherein m is a correction factor.
2. A forward and backward combined dual wavelength dispersive fire smoke detection method according to claim 1 in which: the scattered light intensity ratio threshold value TH L And TH H Determined by previously setting smoke particles of known median size in a laboratory environment.
3. A forward and backward combined dual wavelength dispersive fire smoke detection method according to claim 2, wherein: threshold value TH of scattered light intensity ratio L The value is 0.4-0.6, and the scattered light intensity ratio threshold value TH H The value range is 1.4-1.8.
4. A forward and backward combined dual wavelength dispersive fire smoke detection method according to claim 1 in which: the threshold TH FB Threshold TH FR Saturation threshold TH FR' And the combined threshold TH is set by laboratory measurement according to the alarm time and concentration required by national standard.
5. A forward and backward combined dual wavelength dispersive fire smoke detection method according to claim 1 in which: the value range of the correction factor m is 0.3-0.8.
6. A method of dual wavelength dispersive fire smoke detection according to any of the claims 1 to 5, in combination of forward and backward direction, wherein: constant value d 1 In the range of 350-450nm, constant value d 2 The range is 750-850.
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