CN112304835A - Calibration device and calibration method for high-concentration powder tester - Google Patents

Abstract

The invention discloses a calibration device and a calibration method for a high-concentration powder tester. Compared with the prior art, the device can form stable, uniform and polydisperse solid aerosol at a test section, and has small and exquisite integral size; can be used for high concentration (0-250 g/m) of limited space³) The powder measuring device or system is calibrated, and the calibration error is small.

Description

Calibration device and calibration method for high-concentration powder tester

Technical Field

The invention relates to the technical field of high-concentration powder testing and calibrating systems and methods, in particular to a calibrating device and a calibrating method for a high-concentration powder tester.

Background

The Halon fire extinguishing agent is used as a main fire extinguishing product for fire fighting, has the characteristics of high fire extinguishing speed, high efficiency, no electricity conduction, no residue after fire extinguishing and the like, and is widely applied to civil airliners, electronic computer rooms, cultural relic protection units, large ships and naval vessels. However, since the 70's of the 20 th century, scientists discovered that ozone in the earth's ozone layer was continuously decreasing and discovered that the majority of halon extinguishants used by the fire industry participated in the depletion of the ozone layer. Based on this, in 1987, the United nations environmental planning agency (UNEP) made a Montreal concerted book on ozone-destroying substances. Halon fire extinguishants have been banned so far in developed countries, and are also incorporated into obsolete materials in other developing countries.

Dry powder extinguishing agents are widely used in both military and civilian applications. The research shows that after the dry powder particles are ultra-refined, the fire extinguishing efficiency is improved by times. When fire is extinguished, due to good diffusivity, the fire extinguishing agent can bypass barriers and reserve a long residence time in a fire space, and the fire extinguishing efficiency is high. The fire extinguishing powder can be used for extinguishing A/B mixed fire, B and C fire in a full or semi-closed space, has the fire extinguishing efficiency 5-9 times higher than that of common dry powder, and is 2-3 times higher than that of a Halon fire extinguishing agent.

In order to authenticate the dry powder extinguishing system on the transportation means such as the airplane and the like, the concentration change of the extinguishing agent in different areas in the protective space needs to be recorded and monitored in real time. The concentration of fire suppressant needs to be above the critical fire suppression concentration for the fire zone in the desired time to ensure that all flames in the zone are extinguished. Generally, the critical extinguishing concentration of the dry powder extinguishing agent is 50g/m³The above. This means that the dry powder concentration monitoring equipment needs to monitor the concentration of the dry powder at 50g/m in real time³Sometimes even higher. There are no similar measuring devices on the market today. In order to develop a research suitable for a high concentration powder concentration detection device, it is necessary to develop a high concentration dust environment that can be used for calibration.

In the prior art, in a patent of a wide-range dust concentration detector calibration system and calibration method (CN109900609A), a wide-range dust concentration detector calibration system and calibration method are provided, which can form a continuous stable dust cloud with large concentration (the stable dust cloud concentration reaches 20 g/m) in a dust cloud testing room³) And the requirement of dry powder concentration test certification is not met. A measuring system for dry powder agent is disclosed in the patent "measuring system for powder base agent" (CN 101858846A)The method comprises the following steps: a sensor system comprising at least one sensor head located at least partially within a powder calibration column; and a control system in communication with the sensor system. However, in the system, the inert gas is mixed in the powder calibration column in a high-speed jet mode, the required mixing time is long, the stable distance is long, the calibration error is about +/-16%, and the error range is large.

Disclosure of Invention

In order to achieve higher accuracy of the dust concentration tester, the uniformity and accuracy of the calibration environment need to be ensured. Based on the above, the invention provides a method for high concentration (0-250 g/m)³) Provided are a calibration system and a calibration method of a powder tester.

The technical scheme adopted by the invention is as follows: the utility model provides a calibrating device for high concentration powder tester, includes even aerosol generation system, balance weighing system, test cavity, powder are caught and processing system, wherein:

the aerosol generating system comprises an air source part, an aerosol generator, a conveying pipeline and an aerosol outlet. The gas source part supplies gas for the aerosol generator through the conveying pipeline and is used for dispersing powder. The gas supply section includes a controller operable to regulate the flow of gas. The aerosol generator thoroughly mixes the powder sample with the gas stream to form a polydisperse aerosol.

The balance weighing system comprises a balance, a data acquisition system and a data line. The balance measures the mass loss of the powder in the aerosol generator in real time and carries out data acquisition processing through the data acquisition system.

The testing cavity is composed of a section of cylindrical pipeline, transparent materials such as quartz, high borosilicate and PMMA are selected, and anti-static treatment is carried out. The aerosol with uniform polydispersion enters the pipeline cavity through the aerosol inlet, and finally the particle speeds of different particle sizes reach stability through uniform diffusion for a certain distance and move downwards at a constant speed. The distance of the calibration section from the port should be greater than 15 times the diameter of the pipe.

The powder capturing and processing system comprises a connecting hose, a powder settling bin and a pressure release port. The powder enters the powder settling bin through the connecting hose, and the powder settles in the settling bin. In order to avoid the influence of the pressure in the settling bin on the powder movement, redundant gas is released from the pressure release port. The other end of the pressure release port is connected with the atmosphere environment.

A calibration method for a high-concentration powder tester is used for the accuracy correction of the high-concentration tester and comprises the following steps:

step S1), before calibration experiment, drying the powder to be measured in a drying oven for 24h, taking out and placing in a dryer for 2h, and carrying out pretreatment on the powder;

step S2), setting the testing environment to be 25 ℃, selecting dry air as an air source, putting dry powder into an aerosol generator, and putting the aerosol generator on a balance;

step S3), a data acquisition system of the balance is opened, the mass change M' of the balance is recorded in real time, an air source is started and adjusted to a specified flow Q, and then an aerosol generator is started to generate polydisperse aerosol;

step S4), collecting real-time signals of the calibration instrument, such as shading rate and transmissivity;

step S5), selecting a stable section I in the signals, and calculating the concentration C of the aerosol as M'/Q by using the mass loss and the flow of the aerosol generator;

step S6), the signals I are in one-to-one correspondence with the concentration C of the aerosol, an X-Y diagram is drawn, and fitting processing is carried out in a data fitting mode, so that the relation between the corresponding signals and the measured concentration is obtained.

The working principle of the invention is as follows:

because the concentration of the calibration environment is too high, the calibration of the test environment by a filter membrane weighing method is difficult. The concentration in the test environment is characterized in terms of mass loss and specified flow rate, and is in one-to-one correspondence with the signals obtained by the instrument to be calibrated. The concentration of certain powder under certain signal output is obtained through a data fitting mode.

The invention has the beneficial effects that:

(1) the time for the powder to reach stability in the test cavity is short, the distance is short, and the device is small and exquisite;

(2) the invention has good repeatability;

(3) the calibration environment provided by the invention has good uniformity and high precision, and the measurement error of the high-concentration dust tester is controlled within 10%.

Drawings

Fig. 1 is a schematic diagram of a calibration device for a high-concentration powder tester according to the present invention, wherein 1 is an aerosol generation system, 2 is a balance weighing system, 3 is a test chamber, and 4 is a powder capture and processing system;

FIG. 2 is a schematic diagram of an aerosol generating system, wherein 11 is a gas source portion, 12 is an aerosol generator, 13 is a delivery conduit, and 14 is an aerosol outlet;

FIG. 3 is a schematic diagram of a balance weighing system, wherein 21 is a balance, 22 is a data acquisition system, and 23 is a data line;

fig. 4 is a schematic diagram of a main testing chamber and a powder capturing and processing system, wherein 31 is an aerosol inlet, 32 is a pipeline chamber, 33 is a calibration section, 41 is a connection hose, 42 is a powder settling bin, and 43 is a pressure release port;

FIG. 5 is a schematic diagram of an embodiment for calibration testing, wherein 51 is a laser emitting end and 52 is a laser receiving end;

FIG. 6 is a schematic view of the dispersion of dust aerosol in a test chamber for one embodiment of a calibration test;

FIG. 7 is a graph of photo-electric signal over time for one embodiment of a calibration test;

FIG. 8 is a real-time plot of mass over time for a calibration test;

FIG. 9 is a calibration fit curve.

Detailed Description

The invention is further illustrated with reference to the accompanying drawings and the detailed description. It should be understood that the following examples are further illustrative of the present disclosure and are not to be construed as limiting the scope of the present disclosure, but rather that the present disclosure is not limited to the following examples, and that any simple modification or replacement based on the spirit of the present disclosure is within the scope of the present disclosure.

Fig. 1 schematically shows a calibration device for a high-concentration powder tester, which comprises an aerosol generation system 1, a balance weighing system 2, a test chamber 3 and a powder capturing and processing system 4. The aerosol generating system 1 comprises a gas supply portion 11, an aerosol generator 12, a delivery conduit 13, and an aerosol outlet 14. The gas supply section 11 includes a controller operable to regulate the flow of gas Q, which can be regulated. In some embodiments, gas source portion 11 may be high purity nitrogen, dry air, or a device or system that provides the relevant gas. Depending on the measurement environment and the usage scenario. The aerosol generator 12 intimately mixes the powder sample with the gas stream to form a polydisperse aerosol. In some embodiments, the aerosol generator is selected from the RGB-1000 model produced by PALAS, Germany. The aerosol generator is capable of a metered constant diffusion mass flow rate at a maximum level in the range of about 10mg/h to about 430 g/h. The aerosol generator is conveyed to the rotary brush through the piston, the rotary brush can accurately convey a certain amount of samples to the diffusion head, the air flow is accelerated at the diffusion head through the acceleration of the nozzle, the high-speed air flow provides necessary turbulence and shearing force for the sufficient dispersion of the powder, the agglomerated particles are finally dispersed and output, and the output aerosol is in polydisperse distribution. It is to be noted that the aerosol is formed in the aerosol generator and is transported to the test chamber 3 by a pipe.

The generated aerosol enters the pipeline cavity 32 through the aerosol inlet 31, and is uniformly diffused for a certain distance, so that the particle speeds of different particle sizes are stable and move downwards at a constant speed. In one embodiment, the movement of the powder in the conduit is numerically simulated. Sodium bicarbonate powder was used as a dummy, and the powder consisted of 5 different particle sizes, 0.48 μm (10%), 0.63 μm (20%), 0.79 μm (30%), 1.10 μm (20%), 2.08 μm (10%). The aerosol is ejected from a cylindrical orifice of 6mm diameter into the duct chamber 32. As can be seen from fig. 6, the powder can be stabilized in the pipe cavity 32 in a short time.

The balance 21 measures the mass loss of the powder in the aerosol generator in real time, and the data acquisition system 22 acquires and processes the data to calculate the mass loss M' in unit time. For the purpose of comparison with the test instrument signal, it is desirable that the value of M' be as stable as possible. This means that the amount of aerosol emitted by the aerosol generator per unit of time should be a certain value. Figure 7 shows a graph of mass loss of an aerosol generator over time obtained by experiments in some examples. The powder loss rate M' was 0.070 g/s. The air volume passing through the aerosol generator is 2.15m³H is used as the reference value. Thus, the concentration of the powder generated by the aerosol generator can be calculated to be 117.2g/m³。

In order to avoid as much as possible loss of aerosol during transport, the transport pipe 13 should be as short as possible. In some embodiments, the test chamber 3 is made of a cylindrical tube, and is made of a transparent material such as quartz, borosilicate, or PMMA, and is treated to prevent static electricity. The calibration section 33 is used to position the instrument to be calibrated. To obtain more accurate data, the calibration section 33 should be more than 15 times the diameter of the pipe from the port.

The powder capturing and processing system 4 is composed of a connecting hose 41, a powder settling bin 42 and a pressure release port 43. The powder enters a powder settling bin 42 through a connecting hose 41, and the powder is settled in the settling bin. In order to avoid the influence of the pressure in the settling bin on the powder movement, the redundant gas is released through the pressure release port 43. The other end of the pressure relief port 43 is connected to the atmosphere.

A calibration method for a high-concentration powder tester is used for accuracy correction of the high-concentration tester. In some embodiments, the aerosol generator is of the RGB-1000 type, and the dry powder is a superfine dry powder fire extinguishing agent manufactured by Shandong national Tai Co., Ltd, wherein the fire extinguishing agent comprises ammonium dihydrogen phosphate as a main component, and 90% of the fire extinguishing agent has a cumulative distribution particle size of 1 micron. The specific steps for calibrating the high concentration powder tester are as follows:

step S1), before calibration experiment, drying the ammonium dihydrogen phosphate superfine dry powder extinguishing agent to be detected in a drying box for 24h, taking out and placing in a dryer for 2h, and performing pretreatment on powder;

step S2), setting the testing environment to be 25 ℃, selecting dry air as an air source, placing dry powder on a powder column of an aerosol generator, and placing the aerosol generator on a balance;

step S3), a data acquisition system of the balance is opened, the mass change M' of the balance is recorded in real time, an air source is started, and the specified flow Q is adjusted. The aerosol generator is then turned on to effect the generation of polydispersed aerosol.

Step S4), the used calibration instrument is as shown in fig. 5, the laser emitting end and the laser receiving end are respectively arranged at two ends of the calibration section, and dust-proof treatment is performed to avoid measurement errors caused by dust adhering to the lens in the test process. The optical distance between the laser emitting end and the laser receiving end is 15 mm. Before the test, the initial intensity I of the laser is recorded₀. And when the powder passes through, recording the light intensity signal in real time.

Step S5), selecting an average value I 'of a stable section of signals in the signals, and calculating the concentration C of the dust aerosol in the pipeline cavity to be M'/Q by using the mass loss and the flow of the aerosol generator;

step S6), according to the initial light intensity, the transmissivity I'/I is adjusted₀And drawing an X-Y diagram corresponding to the concentration C of the aerosol one by one, and fitting by a data fitting mode to obtain the relation between the corresponding signal and the measured concentration.

Claims (4)

1. The utility model provides a calibrating device for high concentration powder tester, its characterized in that includes even aerosol generating system (1), balance weighing system (2), test cavity (3) and powder capture and processing system (4), wherein:

the aerosol generating system (1) comprises an air source part (11), an aerosol generator (12), a conveying pipeline (13) and an aerosol outlet (14); the gas source part (11) supplies gas to the aerosol generator (12) through the conveying pipeline (13) and is used for dispersing powder; the gas source part (11) comprises a controller which can be used for adjusting the gas flow; an aerosol generator (12) mixes the powder sample with the gas stream thoroughly to form a polydisperse aerosol;

the balance weighing system (2) comprises a balance (21), a data acquisition system (22) and a data line (23); the balance (21) measures the mass loss of powder in the aerosol generator in real time and carries out data acquisition processing through the data acquisition system (22);

the testing cavity (3) is composed of a section of cylindrical pipeline, the uniformly polydispersed aerosol enters the pipeline cavity (32) through the aerosol inlet (31), and after a section of distance uniform diffusion, the particle speeds of different particle sizes are stable finally, and the particles move downwards at a constant speed, and the distance between the calibration section (33) and the port is more than 15 times of the diameter of the pipeline;

the powder capturing and processing system (4) consists of a connecting hose (41), a powder settling bin (42) and a pressure release port (43); the powder enters a powder settling bin (42) through a connecting hose (41), the powder settles in the settling bin, in order to avoid the influence of the pressure in the settling bin on the powder movement, redundant gas is released through a pressure release port (43), and the other end of the pressure release port (43) is connected with the atmospheric environment.

2. The calibration device of claim 1, wherein the test chamber is made of a transparent material such as quartz, borosilicate, or PMMA, and is treated to prevent static electricity.

3. The calibration device for the high concentration powder tester as recited in claim 1, wherein the other end of the pressure release port is connected to an atmospheric environment or a dust removal device.

4. A calibration method for a high-concentration powder tester is characterized by comprising the following steps: the method comprises the following steps:

step S1), before calibration experiment, drying the powder to be measured in a drying oven at 50 ℃ for 24h, taking out and placing in a dryer for 2h, and carrying out pretreatment on the powder;

step S2), setting the testing environment at 25 ℃, keeping the pressure and humidity constant, selecting dry air as an air source, putting the powder into an aerosol generator, and putting the aerosol generator on a balance;

step S3), a data acquisition system of the balance is opened, the mass change M' of the balance is recorded in real time, an air source is started and adjusted to a specified flow Q, and then an aerosol generator is started to generate polydisperse aerosol;

step S4), collecting real-time signals of the calibration instrument, such as shading rate and transmissivity;

step S5), selecting a stable section I in the signals, and calculating the concentration C of the aerosol as M'/Q by using the mass loss and the flow of the aerosol generator;

step S6), the signals I are in one-to-one correspondence with the aerosol concentration C, an X-Y corresponding point diagram is drawn, and the data are subjected to fitting processing, so that the relation between the signal output and the measured concentration is obtained.

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