CN113670678A - Constant-speed tracking sampling method for smoke detection - Google Patents
Constant-speed tracking sampling method for smoke detection Download PDFInfo
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- 238000005070 sampling Methods 0.000 title claims abstract description 105
- 239000000779 smoke Substances 0.000 title claims abstract description 103
- 238000001514 detection method Methods 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000003546 flue gas Substances 0.000 claims abstract description 111
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 107
- 238000000605 extraction Methods 0.000 claims description 10
- 238000012937 correction Methods 0.000 claims description 6
- 230000003189 isokinetic effect Effects 0.000 claims description 5
- 239000007983 Tris buffer Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 4
- 239000000243 solution Substances 0.000 description 7
- 238000010586 diagram Methods 0.000 description 4
- 239000003517 fume Substances 0.000 description 4
- 238000000149 argon plasma sintering Methods 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000012855 volatile organic compound Substances 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
- G01N1/2205—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with filters
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
- G01N1/2258—Sampling from a flowing stream of gas in a stack or chimney
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B11/00—Automatic controllers
- G05B11/01—Automatic controllers electric
- G05B11/36—Automatic controllers electric with provision for obtaining particular characteristics, e.g. proportional, integral, differential
- G05B11/42—Automatic controllers electric with provision for obtaining particular characteristics, e.g. proportional, integral, differential for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
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- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
- G01N2001/225—Sampling from a flowing stream of gas isokinetic, same flow rate for sample and bulk gas
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
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- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2247—Sampling from a flowing stream of gas
- G01N2001/227—Sampling from a flowing stream of gas separating gas from solid, e.g. filter
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
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- G01N2015/0681—Purposely modifying particles, e.g. humidifying for growing
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Abstract
The present disclosure provides a constant velocity tracking sampling method for smoke detection, the method includes obtaining a flue flow rate of smoke; acquiring the target flow of the flue gas according to the flue flow velocity of the flue gas, and calculating the flow difference value between the target flow of the flue gas and the actual sampling flow; and controlling the smoke detection equipment based on the flow difference value, so that the sampling speed of the smoke is equal to the flue flow speed of the smoke. According to the constant-speed tracking sampling method for smoke detection, the smoke detection equipment is controlled by calculating the flow difference value between the target flow and the actual sampling flow of smoke, so that the sampling speed of the smoke is equal to the flow speed of the smoke in a flue, constant-speed tracking sampling is realized, and the measurement accuracy of smoke concentration is improved.
Description
Technical Field
The disclosure relates to the field of smoke detection, in particular to a constant-speed tracking sampling method for smoke detection.
Background
Due to the fact that the density of the catering oil fume emission source is rapidly improved, the oil fume pollution amount is large, the range is wide, the low altitude diffusivity is strong, the urban haze is directly contributed, and the urban haze is harmful to human bodies greatly. Relevant researches show that the catering oil fume emission particulate matters are important sources of urban VOCs and PM2.5, the VOCs in the urban oil fume emission particulate matters react with nitrogen oxides in the environment, the oxidability of the atmosphere is enhanced, the formation of secondary particulate matters is accelerated, and the excessive ozone in summer is caused.
The oil smoke direct-reading detecting instrument based on the light scattering method adopted in the current market is constant flow sampling, and cannot dynamically track the sampling speed according to the flow velocity of the smoke in a flue, so that the measuring accuracy of the oil smoke concentration is reduced.
Disclosure of Invention
In view of this, the present disclosure provides a constant-speed tracking sampling method for flue gas detection, which controls a flue gas detection device by calculating a flow difference between a target flow and an actual sampling flow of flue gas, so that a sampling speed is equal to a flue gas flow speed of a flue, thereby improving a measurement accuracy of flue gas concentration.
The present disclosure provides a constant velocity tracking sampling method for smoke detection, comprising:
acquiring the flue flow velocity of the flue gas, wherein the calculation formula of the flue flow velocity of the flue gas is as follows:
wherein, VsFlue flow rate, K, for flue gasespFor pitot tube correction factor, PdIs the dynamic pressure of the flue gas in the flue, rhonIs the density of dry flue gas, XswIs the volume percentage of the water content in the flue gas, TsIs the temperature of flue gas in the flue, BaAt atmospheric pressure, PtThe total pressure of the flue gas in the flue is set;
acquiring the target flow of the flue gas according to the flue flow velocity of the flue gas, and calculating the flow difference value between the target flow of the flue gas and the actual sampling flow;
and controlling the smoke detection equipment based on the flow difference value to enable the sampling speed of the smoke to be equal to the flue flow speed of the smoke.
In a possible embodiment of the present disclosure, the target flow rate of the flue gas is a constant-speed tracking flow rate at a sampling nozzle of the flue gas detection device or a constant-speed tracking flow rate at an orifice plate of the flue gas detection device.
In a possible embodiment of the present disclosure, the constant velocity tracking flow at the sampling nozzle of the smoke detection device is calculated by the following formula:
Qr＝0.047×d2×Vs
wherein Qr is the constant-speed tracking flow at the sampling nozzle of the smoke detection equipment, d is the diameter of the sampling nozzle, and V issIs the flue flow rate of the flue gas.
In a possible embodiment of the present disclosure, the constant velocity tracking flow at the orifice plate of the smoke detection device is calculated by the following formula:
wherein Qr' is the constant-speed tracking flow at the orifice plate of the smoke detection equipment, d is the diameter of the sampling nozzle, and VsFlue flow rate of flue gas, BaAt atmospheric pressure, PtIs the total pressure of flue gas in the flue, PdIs a cigaretteDynamic pressure of flue gas in the flue, KpFor pitot tube correction factor, TsIs the temperature of flue gas in the flue, TrIs the flue gas temperature before the flowmeter, PrIs the flue gas pressure before the flowmeter, XswIs the volume percentage of the moisture content in the smoke.
In a possible embodiment of the present disclosure, in a case that the target flow rate of the flue gas is a constant-speed tracking flow rate at a sampling nozzle of the flue gas detection device, the actual sampling flow rate is an actual sampling flow rate at the sampling nozzle of the flue gas detection device.
In a possible embodiment of the present disclosure, in a case that the target flow rate of the flue gas is a constant-speed tracking flow rate at a perforated plate of a flue gas detection device, the actual sampling flow rate is an actual sampling flow rate at the perforated plate of the flue gas detection device.
In a possible embodiment of the present disclosure, the controlling the smoke detection device based on the flow difference includes controlling a smoke extraction rate of the smoke detection device by a PID control system based on the flow difference, where the flow difference is used as an input of the PID control system, and controlling the smoke extraction rate of the smoke detection device by an output signal of the PID control system.
In one possible embodiment of the present disclosure, the output signal u (t) of the PID control system is calculated by the following formula:
wherein u (t) is an output signal of the PID control system, KpIs a proportionality coefficient, e (t) is the flow difference, KiIs an integral coefficient, t is an execution period of a PID control system, KdIs a differential coefficient.
In one possible embodiment of the disclosure, the measuring range of the flow difference is divided into a plurality of sections, and the proportionality coefficient K is divided into different sectionspIntegral coefficient KiAnd a differential coefficient KdHave different values.
In one possible embodiment of the disclosure, the PID control system stops calculating the output signal when the absolute value of the flow difference is smaller than a preset threshold.
According to the constant-speed tracking sampling method for smoke detection, the extraction rate of smoke detection equipment is controlled by calculating the flow difference value between the target flow and the actual sampling flow of smoke, so that the sampling speed of the smoke is equal to the flow speed of the smoke in a flue, constant-speed tracking sampling is realized, and the accuracy of smoke concentration is effectively improved.
Drawings
In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, a brief description will be given below of the drawings required for describing the embodiments or the prior art, and it is apparent that the drawings in the following description are some embodiments of the present disclosure, but not all embodiments. For a person skilled in the art, other figures can also be obtained from these figures without inventive exercise.
Fig. 1 is a schematic flow chart of a constant velocity tracking sampling method for smoke detection according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram illustrating a smoke dynamic pressure and a full pressure detection of the smoke detection device according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a smoke detection device according to an embodiment of the present disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are some, but not all embodiments of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
The technical solution of the present disclosure is explained in detail by specific examples below. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
When the sampling speed of the smoke detection equipment is greater than or less than the smoke speed in the flue, the sampling result is deviated, when the sampling speed is greater than the smoke speed in the flue, partial airflow outside the side line of the sampling nozzle enters the sampling nozzle, dust particles in the airflow cannot change the direction due to the inertia effect of the dust particles and enter the sampling nozzle along the airflow, the dust particles continue to advance along the original direction, and the concentration of the sample adopted in the way is lower than the actual concentration of the sampling point. When the sampling speed is lower than the flue gas speed in the flue, the concentration of the sample is higher than the actual concentration of the sampling point. Only when the sampling speed is equal to the flue gas speed in the flue, the concentration of the sample is equal to the actual concentration of the sampling point.
Based on the problems in the prior art, the embodiment of the disclosure provides a constant-speed tracking sampling method for smoke detection, which controls smoke detection equipment by calculating a flow difference value between a target flow and an actual sampling flow of smoke, so that the sampling speed of the smoke is equal to the flow speed of the smoke in a flue, and constant-speed tracking sampling is realized, thereby improving the accuracy of measured smoke concentration.
Fig. 1 is a schematic flow chart of a constant velocity tracking sampling method for smoke detection according to an embodiment of the present disclosure.
As shown in fig. 1, an embodiment of the present disclosure provides a method for isokinetic tracking sampling for smoke detection, including:
s110: acquiring the flue flow velocity of the flue gas, wherein the calculation formula of the flue flow velocity of the flue gas is as follows:
wherein, VsFlue flow rate, K, for flue gasespFor pitot tube correction factor, PdIs the dynamic pressure of the flue gas in the flue, rhonIs the density of dry flue gas, XswIs the volume percentage of the water content in the flue gas, TsIs the temperature of flue gas in the flue, BaAt atmospheric pressure, PtThe total pressure of the flue gas in the flue.
S120: and acquiring the target flow of the flue gas according to the flue flow velocity of the flue gas, and calculating the flow difference value between the target flow of the flue gas and the actual sampling flow.
In an embodiment of the present disclosure, the target flow rate of the flue gas may be a constant-velocity tracking flow rate at a sampling nozzle of a flue gas detection device, and the constant-velocity tracking flow rate at the sampling nozzle of the flue gas detection device is calculated by the following formula:
Qr＝0.047×d2×Vs
wherein Qr is the constant-speed tracking flow at the sampling nozzle of the smoke detection equipment, d is the diameter of the sampling nozzle, and V issIs the flue flow rate of the flue gas.
In this embodiment, under the condition that the target flow of the flue gas is the constant-speed tracking flow at the sampling nozzle of the flue gas detection device, the actual sampling flow is the actual sampling flow at the sampling nozzle of the flue gas detection device. The actual sampling flow at the sampling nozzle of the smoke detection device can be measured by a flow meter adjacent to the sampling nozzle.
Further, in this embodiment, the flow difference between the target flow of the flue gas and the actual sampling flow is a flow difference between the constant-speed tracking flow at the sampling nozzle of the flue gas detection device and the actual sampling flow at the sampling nozzle of the flue gas detection device measured by the flow meter adjacent to the sampling nozzle.
In another embodiment of the present disclosure, the target flow rate of the flue gas may be a constant-speed tracking flow rate at an orifice plate of a flue gas detection device, and the constant-speed tracking flow rate at the orifice plate of the flue gas detection device is calculated by the following formula:
wherein Qr' is the constant-speed tracking flow at the orifice plate of the smoke detection equipment, d is the diameter of the sampling nozzle, and VsFlue flow rate of flue gas, BaAt atmospheric pressure, PtIs the total pressure of flue gas in the flue, PdDynamic pressure of flue gas in flue, KpFor pitot tube correction factor, TsIs the temperature of flue gas in the flue, TrIs the flue gas temperature before the flowmeter, PrIs the flue gas pressure before the flowmeter, XswIs the volume percentage of the moisture content in the smoke.
In this embodiment, the flue flow velocity V of the flue gassThe unit of (A) is m/s, and the temperature T of the flue gas before the flowmeterrThe unit of the flow rate is L/min, the unit of the constant-speed tracking flow rate at the sampling nozzle of the smoke detection equipment is L/min, the unit of the constant-speed tracking flow rate at the orifice plate of the smoke detection equipment is mm, and the unit of the smoke pressure before the flowmeter is kPa.
In this embodiment, under the condition that the target flow of the flue gas is the constant-speed tracking flow at the perforated plate of the flue gas detection device, the actual sampling flow is the actual sampling flow at the perforated plate of the flue gas detection device. The actual sampling flow at the orifice plate of the smoke detection device can be measured by a flow meter adjacent to the orifice plate of the smoke detection device.
Further, in this embodiment, the flow difference between the target flow and the actual sampling flow of the flue gas is a flow difference between the constant-speed tracking flow at the perforated plate of the flue gas detection device and the actual sampling flow at the perforated plate of the flue gas detection device measured by the flow meter adjacent to the perforated plate of the flue gas detection device.
S130: and controlling the smoke detection equipment based on the flow difference value to enable the sampling speed of the smoke to be equal to the flue flow speed of the smoke.
In an embodiment of the present disclosure, the controlling the smoke detection device based on the flow difference value includes controlling a smoke extraction rate of the smoke detection device through a PID control system based on the flow difference value, where the flow difference value is used as an input of the PID control system, and controlling the smoke extraction rate of the smoke detection device through an output signal of the PID control system.
In one embodiment of the present disclosure, the output signal u (t) of the PID control system is calculated by the following formula:
wherein u (t) is the output signal of the PID control system, e (t) is the flow difference value, KpIs a proportionality coefficient, e (t) is the flow difference, KiIs an integral coefficient, t is an execution period of a PID control system, KdIs a differential coefficient.
Further, in an embodiment of the present disclosure, the relationship between the output signal u (t) of the PID control system and the flow rate difference e (t) may not be completely linear, and in this case, the measuring range of the flow rate difference may be divided into multiple segments, and the proportionality coefficient K may be divided into different segmentspIntegral coefficient KiAnd a differential coefficient KdHave different values. For example, K may bep、KiAnd KdAre respectively set to 50, 20 and 1, and when the flow difference e (t) is less than 2L, K isp、KiAnd KdKeeping the initial value unchanged; when the flow difference e (t) is more than or equal to 2L and less than 10L, K is addedp、KiAnd KdMultiplying the initial values by 1.5 respectively, namely setting the values to be 75, 30 and 1.5 respectively; when the flow difference is more than or equal to 10L and less than 20L, K is addedp、KiAnd KdRespectively, multiply by 2, i.e. set to values of 100, 40, 2, respectively. By applying a voltage to K over different ranges of the flow difference e (t)p、KiAnd KdDifferent values are set, so that the control efficiency of the PID control system can be improved, and the control stability of the PID control system can be obviously enhanced.
In an embodiment of the disclosure, since the flow value is related to factors such as gas circuit design, circuit and sampling pump characteristics, and sensor reading, the flow value itself has a certain fluctuation, and when the absolute value of the flow difference e (t) is smaller than a preset threshold, the PID control system stops calculating the output signal. Specifically, the preset threshold value may be set to 0.1, that is, when the absolute value of e (t) is less than 0.1, the PID control system stops calculating the output signal, so that the control signal increment is 0, to enhance the stability of flow control. It should be noted that the values of the preset threshold are only examples, and those skilled in the art can set the preset threshold according to the requirement.
The output value u (t) of the PID control system is a PWM output signal, and in an embodiment of the present disclosure, an overload protection function may be further provided to the PWM output signal. For example, in this embodiment, the PWM output signals are respectively set to a maximum value and a minimum value, and if the PWM output signals are greater than the maximum value, the PWM output signals are still output according to the maximum value; if the PWM output signal is smaller than the minimum value, the PWM output signal is still output according to the minimum value, and in this way, the pulse of the PWM output signal can be prevented from being too large or too small, so that the damage to an air suction device (such as a fan or a pump) of the smoke detection equipment is avoided. In this embodiment, the maximum value of the PWM output signal may be set to 999 and the minimum value may be set to 70. It should be noted that the maximum value or the minimum value of the PWM output signal is only an example, the value of the PWM output signal is not specifically limited in this embodiment, and a person skilled in the art can set the relevant value according to the requirement.
Fig. 2 is a schematic diagram illustrating a smoke dynamic pressure and a total pressure detection of the smoke detection device according to an embodiment of the disclosure, as shown in fig. 2, a smoke dynamic pressure P in a fluedAnd the total pressure P of the flue gas in the fluetMeasured by the pitot tube 201. Specifically, the flue gas in the flue flows from bottom to top, one end of the pitot tube 201 extends into the flue 202, and the other end of the pitot tube 201 is connected with a dynamic pressure sensor and a full pressure sensor respectively and is used for providing dynamic pressure P for the flue gas in the fluedAnd the total pressure P of the flue gas in the fluetThe measurement is performed.
Fig. 3 is a schematic structural diagram of a smoke detection device provided in an embodiment of the present disclosure, and as shown in fig. 3, the smoke detection device includes a pitot tube 301 and a sampling tube 302, and a temperature sensor 303 extends into the pitot tube 301 and is configured to collect a smoke temperature in a flue and send the smoke temperature back to a smoke temperature detection unit 304 disposed at an end of the pitot tube 301 far from the flue for analysis. In this embodiment, when the pitot tube 301 is an S-shaped pitot tube, the temperature sensor 303 may be separately disposed between two pipes of the pitot tube.
The sampling nozzle 305 is arranged at one end of the sampling pipe 302 entering the flue, the moisture content sensor 306, the light scattering module 307, the filter 308, the orifice plate 309 and the fan 310 are sequentially arranged at one end of the sampling pipe 302 far away from the flue according to the sequence from near to far from the flue, wherein the moisture content sensor 306 is used for detecting the volume percentage of the moisture content in the flue gas, the light scattering module 307 is used for detecting the flue gas concentration, the filter 308 is used for stabilizing and buffering the flue gas flow, and the fan 310 is used for receiving an output signal of a PID control system and adjusting the flue gas extraction rate. In addition, a collection nozzle flowmeter and an orifice flowmeter (not shown in the figure) are respectively arranged near the sampling nozzle 305 and the orifice 309, and are used for collecting and displaying the actual sampling flow at the sampling nozzle and the actual sampling flow at the orifice. In this embodiment, the fan 310 may also be other devices capable of adjusting the smoke extraction rate, such as an air pump.
According to the constant-speed tracking sampling method for smoke detection provided by the embodiment of the disclosure, the smoke extraction rate of the smoke detection equipment is controlled based on the flow difference value between the target flow and the actual sampling flow of the smoke, so that the sampling speed of the smoke is equal to the flow speed of the smoke in a flue, constant-speed tracking sampling is realized, and the measurement accuracy of smoke concentration is improved.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present disclosure, and not for limiting the same; while the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present disclosure.
Claims (10)
1. A constant velocity tracking sampling method for smoke detection is characterized by comprising the following steps:
acquiring the flue flow velocity of the flue gas, wherein the calculation formula of the flue flow velocity of the flue gas is as follows:
wherein, VsFlue flow rate, K, for flue gasespFor pitot tube correction factor, PdIs the dynamic pressure of the flue gas in the flue, rhonIs the density of dry flue gas, XswIs the volume percentage of the water content in the flue gas, TsIs the temperature of flue gas in the flue, BaAt atmospheric pressure, PtThe total pressure of the flue gas in the flue is set;
acquiring the target flow of the flue gas according to the flue flow velocity of the flue gas, and calculating the flow difference value between the target flow of the flue gas and the actual sampling flow;
and controlling the smoke detection equipment based on the flow difference value to enable the sampling speed of the smoke to be equal to the flue flow speed of the smoke.
2. The method according to claim 1, wherein the target flow rate of the flue gas is a constant velocity tracking flow rate at a sampling nozzle of the flue gas detection device or a constant velocity tracking flow rate at an orifice plate of the flue gas detection device.
3. The isokinetic tracking sampling method for smoke detection according to claim 2, wherein the isokinetic tracking flow at the sampling nozzle of the smoke detection device is calculated by the following formula:
Qr＝0.047×d2×Vs
wherein Qr is the constant-speed tracking flow at the sampling nozzle of the smoke detection equipment, d is the diameter of the sampling nozzle, and V issIs the flue flow rate of the flue gas.
4. The isokinetic tracking sampling method for smoke detection as set forth in claim 2, wherein the isokinetic tracking flow at the orifice plate of the smoke detection device is calculated by the following formula:
wherein Qr' is the constant-speed tracking flow at the orifice plate of the smoke detection equipment, d is the diameter of the sampling nozzle, and VsFlue flow rate of flue gas, BaAt atmospheric pressure, PtIs the total pressure of flue gas in the flue, PdDynamic pressure of flue gas in flue, KpFor pitot tube correction factor, TsIs the temperature of flue gas in the flue, TrIs the flue gas temperature before the flowmeter, PrIs the flue gas pressure before the flowmeter, XswIs the volume percentage of the moisture content in the smoke.
5. The method according to claim 2, wherein in the case that the target flow rate of the flue gas is an equal-speed tracking flow rate at a sampling nozzle of the flue gas detection device, the actual sampling flow rate is an actual sampling flow rate at the sampling nozzle of the flue gas detection device.
6. The method according to claim 2, wherein in the case that the target flow rate of the flue gas is the constant velocity tracking flow rate at the orifice plate of the flue gas detection device, the actual sampling flow rate is the actual sampling flow rate at the orifice plate of the flue gas detection device.
7. The method of claim 1, wherein controlling the smoke detection device based on the flow difference value comprises controlling a smoke extraction rate of the smoke detection device through a PID control system based on the flow difference value, wherein the flow difference value is used as an input of the PID control system, and the smoke extraction rate of the smoke detection device is controlled through an output signal of the PID control system.
8. The method of claim 7, wherein the output signal u (t) of the PID control system is calculated by the following formula:
wherein u (t) is an output signal of the PID control system, KpIs a proportionality coefficient, e (t) is the flow difference, KiIs an integral coefficient, t is an execution period of a PID control system, KdIs a differential coefficient.
9. The method of claim 8, wherein said flow differential is divided into a plurality of segments, and said scaling factor K is applied to different segmentspIntegral coefficient KiAnd a differential coefficient KdHave different values.
10. The method of claim 8, wherein the PID control system stops calculating the output signal when the absolute value of the flow difference is less than a preset threshold.
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