CN111948091A - Gas concentration measuring device and method - Google Patents
Gas concentration measuring device and method Download PDFInfo
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- CN111948091A CN111948091A CN202010944314.2A CN202010944314A CN111948091A CN 111948091 A CN111948091 A CN 111948091A CN 202010944314 A CN202010944314 A CN 202010944314A CN 111948091 A CN111948091 A CN 111948091A
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Abstract
The present disclosure provides a gas concentration measuring device, including: the preheating module is used for preheating and rectifying the input gas to be detected and then outputting a first-stage gas; the differential pressure conversion module is connected with the preheating module and is used for enabling the gas flowing through the first stage to generate a differential pressure change value; and the processing module is used for obtaining the volume concentration of the gas to be measured according to the differential pressure change value. The differential pressure conversion module comprises a capillary laminar flow unit with a plurality of capillaries, and the flow channels of the capillaries become main channels of airflow to form a laminar flow structure. The present disclosure also provides a gas concentration measuring method, which uses the gas concentration measuring device to measure the concentration of the gas to be measured.
Description
Technical Field
The disclosure relates to the technical field of instruments and equipment, in particular to a gas concentration measuring device and method.
Background
With the development of technology, it is sometimes necessary to measure in real time a certain gas concentration state in a space, for example, to confirm whether the amount of a gaseous extinguishing agent carried by a fire extinguishing system in a vehicle or aircraft is acceptable, to release the extinguishing agent to the space to be protected, and to record the volume concentration of the extinguishing agent at a representative position in each area of the space to be protected by a measuring system. The concentration of fire suppressant must be above a known effective fire suppression concentration, which is a concentration of fire suppressant sufficient to suppress a possible fire in the protected area over a period of time.
Patent CN109540747A discloses an airborne measuring device for fire extinguishing agent concentration in a cabin of an aircraft power plant, but the patent does not show an implementation mode of a single-channel measurement unit inner laminar flow type differential pressure measuring device, and the implementation is difficult for those skilled in the art. Patent CN103163046A discloses a device for measuring the concentration of a gaseous extinguishing agent, but the patent adopts an integral heating mode for a constant-temperature constant-current micro-pressure difference generator, and is easily affected by environmental factors; the patent adopts the flow controller to control the flow of 4 ways together, and this causes the flow of 4 ways to probably cause the unbalance of flow because of factors such as jam, processing technology, etc. and then brings the measuring error. Patent CN110844118A discloses a pressure difference test device and method for a multi-cavity structure, but the patent adopts a scheme that a porous sieve is immersed in oil liquid, and the oil liquid can cause pollution and difficulty in maintenance in use. Patent CN105424546 discloses a concentration measuring device of a fire extinguishing agent concentration measuring system, but the through hole scheme adopted by the patent brings inconvenience to equipment processing; the scheme of the pressure stabilizing cavity can cause the mixing of gas, which is not beneficial to improving the response time; the temperature sensor detects the temperature of the heating block and the pressure measuring block, but not the temperature of gas, and when the environment changes, the measurement precision is affected.
Therefore, how to obtain a gas concentration measurement result with higher precision is a technical problem to be solved urgently.
BRIEF SUMMARY OF THE PRESENT DISCLOSURE
Technical problem to be solved
Based on the above problems, the present disclosure provides a gas concentration measurement apparatus and method to alleviate technical problems in the prior art, such as high processing difficulty, difficult maintenance, large measurement value fluctuation and large error during gas concentration measurement.
(II) technical scheme
In one aspect of the present disclosure, there is provided a gas concentration measurement apparatus including: the preheating module is used for preheating and rectifying the input gas to be detected and then outputting a first-stage gas; the differential pressure conversion module is connected with the preheating module and is used for enabling the first-stage gas flowing through to generate a differential pressure change value; the processing module is used for obtaining the volume concentration of the gas to be detected according to the differential pressure change value; the differential pressure conversion module comprises a capillary laminar flow unit with a plurality of capillaries, and the flow channels of the capillaries become main channels of air flow to form a laminar flow structure.
According to an embodiment of the present disclosure, the preheating module includes: the gas flow channel is used for rectifying the gas to be detected; the preheating module electric heating unit is used for heating the gas flow channel so as to conduct and heat the gas to be detected; the preheating module temperature control unit is used for measuring and regulating the temperature of the gas to be measured; the gas flow channel is not bent, and a plurality of capillary pipelines are arranged in the gas flow channel.
According to the embodiment of the present disclosure, the preheating module temperature control unit includes a preheating module thermocouple disposed perpendicular to a gas flow direction.
According to an embodiment of the present disclosure, the differential pressure conversion module further comprises: the differential pressure conversion module shell is coated outside the capillary laminar flow unit, an upstream differential pressure measuring hole is arranged at the upstream end corresponding to the capillary laminar flow unit, and a downstream differential pressure measuring hole is arranged at the downstream end corresponding to the capillary laminar flow unit; the two ends of the differential pressure sensor are respectively connected to the upstream differential pressure measuring hole and the downstream differential pressure measuring hole and are used for measuring the differential pressure between the differential pressure measuring holes; and a flow restriction element located at a downstream outlet of the differential pressure conversion module housing for maintaining a constant volumetric flow rate through the gas concentration measurement device.
According to an embodiment of the present disclosure, the differential pressure conversion module further comprises: the differential pressure conversion module electric heating unit is used for heating the differential pressure conversion module; and the differential pressure conversion module temperature control unit is used for measuring and regulating the temperature of the gas to be measured flowing through the capillary laminar flow unit and the flow limiting element, and comprises a differential pressure conversion module thermocouple which is arranged in a direction perpendicular to the gas flowing direction.
According to an embodiment of the present disclosure, the differential pressure conversion module further comprises: the upstream capillary rectifying element is positioned between the upstream inlet of the differential pressure conversion module shell and the upstream differential pressure measuring hole; the downstream capillary rectifying element is positioned between the downstream outlet of the differential pressure conversion module shell and the downstream differential pressure measuring hole; and the absolute pressure gauge is arranged at the upstream differential pressure measuring hole and used for monitoring the absolute pressure value in the gas flow channel and improving the measuring precision.
According to an embodiment of the present disclosure, the capillary-layer flow unit further includes: the sleeve comprises a first sleeve and a second sleeve which are sleeved outside the plurality of capillary tubes from two sides respectively; and the adhesive is coated on the outer wall of the capillary and the inner wall of the sleeve and used for fixing the multiple capillaries so that the capillaries do not move under the action of the airflow of the gas to be detected.
According to an embodiment of the present disclosure, the tube diameter d of the capillary tubeLFEIs expressed as:
In another aspect of the present disclosure, there is provided a gas concentration measurement method for measuring a concentration of a gas to be measured by using the gas concentration measurement apparatus described in any one of the above, the measurement method including: operation S1: carrying out preheating treatment on the gas concentration measuring device; operation S2: inputting the gas to be measured in the space into the gas concentration measuring device after preheating treatment, and recording a differential pressure value; and operation S3: and determining the concentration of the gas to be detected according to the empirical relationship between the differential pressure value and the volume concentration and differential pressure value of the gas to be detected.
According to an embodiment of the present disclosure, the operation S1 includes: operation S11: introducing gas to be measured with the concentration of 0 or a known concentration into the gas concentration measuring device; and: operation S12: the preheating module electric heating unit and the differential pressure conversion module electric heating unit are used for heating, so that the temperature values measured by the preheating module thermocouple and the differential pressure conversion module thermocouple are stable and the same, and the preheating treatment is completed.
(III) advantageous effects
According to the technical scheme, the gas concentration measuring device and the method disclosed by the invention have at least one or part of the following beneficial effects:
(1) the response speed is high;
(2) the measurement precision is high;
(3) the long-term stability is good;
(4) the use and maintenance are convenient;
(5) the gas concentration monitoring device can be used for quickly measuring the gas concentration and can also be used for monitoring the gas concentration for a long time.
Drawings
Fig. 1 is a schematic composition diagram of a gas concentration measurement device according to an embodiment of the present disclosure.
Fig. 2 is an exploded view of a gas concentration measurement device of an embodiment of the present disclosure.
Fig. 3 is a schematic view of a partial cross-sectional structure of a differential pressure conversion module according to an embodiment of the present disclosure.
Fig. 4 is a perspective schematic view of a differential pressure conversion module according to an embodiment of the disclosure.
Fig. 5 is a schematic view of a capillary flow cell assembly according to an embodiment of the disclosure.
Fig. 6 is a schematic structural diagram of a capillary-laminar flow unit according to an embodiment of the present disclosure.
Fig. 7 is a schematic structural diagram of a differential pressure conversion module and a preheating module according to another embodiment of the disclosure.
Fig. 8 is a schematic structural view of a differential pressure conversion module and a preheating module after being installed in an insulating housing according to another embodiment of the disclosure.
Fig. 9 is a schematic view of a gas concentration measurement system of an embodiment of the present disclosure installed in a cabinet.
Fig. 10 is a rear interface schematic of the enclosure shown in fig. 9.
FIG. 11 is a graphical illustration of an empirical relationship between gas volume concentration and differential pressure values for an embodiment of the disclosure.
Fig. 12 is a schematic flow chart of a gas concentration measurement method according to an embodiment of the present disclosure.
FIG. 13 is a schematic flow chart diagram illustrating operation of a gas concentration measurement system according to an embodiment of the present disclosure.
FIG. 14 is a schematic diagram of the composition of a gas concentration measurement system according to an embodiment of the present disclosure.
[ description of main reference numerals in the drawings ] of the embodiments of the present disclosure
1 casing base
2 casing upper cover
3 gas inlet and outlet panel
4. 61 gas inlet straight joint
5. 64 gas preheating module gas pipeline
6. 62 gas preheating module heating clamping block
7 gas preheating module electric heating unit
8 gas preheating module straight joint
9 gaseous low heat conduction hose of module that preheats
10. Temperature measuring three-way joint of 65 gas preheating module
11 gas preheating module thermocouple
12. 69 differential pressure conversion module casing
12-1 airflow inlet
12-2 airflow outlet
12-3 upstream differential pressure measuring hole
12-4 downstream differential pressure measuring hole
13. 68 capillary laminar flow unit
13-1 capillary
13-2 first sleeve
13-3 second sleeve
14 differential pressure conversion module electric heating unit
15 current limiting element
16 differential pressure measuring orifice joint
17 upstream differential pressure measuring hose
18 downstream differential pressure measurement hose
9() degree elbow of 19 differential pressure sensor
20 differential pressure sensor mounting clip
21 differential pressure conversion module low heat conduction hose
22 differential pressure conversion module temperature measurement tee
23 differential pressure conversion module thermocouple
24 differential pressure conversion module gas pipeline
25 flow meter joint
26 flow meter
27 flowmeter mounting clip
28 front panel
29 flow meter to gas outlet connection hose
30 gas outlet panel installation straight joint
31 three-hole current signal aviation plug
32 two-hole power supply aviation plug
33 electric rear panel
34 solid state relay
35 power supply terminal
36 boat-shaped switch
37 preheat module temperature controller
38 differential pressure conversion module temperature controller
39 differential pressure sensor
40 gas concentration measuring device
41 fixed plug-in box of gas concentration measuring device
42 cooling ventilation equipment subrack
43 keyboard/mouse tray
44 control device plug-in box
45 display
46 power supply plug-in box
47 machine cabinet
48 the cabinet reserves the space
49 cabinet wheel
50 rear access door
51 interface panel
51-1 power output mounting hole
51-2 power input connector mounting hole
51-3 cabinet gas inlet through-plate joint
51-4 cabinet gas outlet through-plate joint
52 side access door
63 electric heating silica gel pad mounting groove
66 upstream capillary flow straightening element
67 upstream differential pressure measuring orifice joint
70 downstream differential pressure measurement orifice joint
71 downstream capillary flow straightening element
72 micro-orifice plate current limiting element
73 differential pressure conversion module temperature measurement three-way thermocouple mounting hole
Temperature measuring tee joint of 74 differential pressure conversion module
Temperature measuring three-way airflow outlet of 75 differential pressure conversion module
76 upstream capillary fairing attachment hole
77 capillary laminar flow unit fixing hole
78 downstream capillary fairing element mounting holes
79 gas inlet heat insulation plate
80 Upper insulating Board
81. 86 side heat insulation plate
Thermocouple preformed hole of gas preheating module of 82 upper heat insulation plate
83 thermocouple preformed hole of differential pressure conversion module of upper heat insulation plate
84 fixed bolt
85 bolt hole
Detailed Description
The utility model provides a gas concentration measuring device and method, it has higher measurement accuracy, can be calibrated, and repeatability is better, can adapt to the change of test environment factor, can be used for the analysis gas concentration and whether satisfy the demand, has extensive application prospect.
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
In an embodiment of the present disclosure, there is provided a gas concentration measurement apparatus, as shown in fig. 1 to 8, including:
the preheating module is used for preheating and rectifying the input gas to be detected and then outputting a first-stage gas;
the differential pressure conversion module is connected with the preheating module and is used for enabling the first-stage gas flowing through to generate a differential pressure change value; the differential pressure conversion module comprises a capillary laminar flow unit with a plurality of capillaries;
and the processing module is used for obtaining the volume concentration of the gas to be detected according to the differential pressure change value.
According to an embodiment of the present disclosure, the gas concentration measurement apparatus includes: casing, gas inlet, gaseous preheating module, differential pressure conversion module, gas outlet, differential pressure sensor, temperature control element and electrical interface, gas inlet, gas outlet install on the casing, gas inlet, gaseous preheating module connects, differential pressure conversion module and gas outlet connect gradually through gas piping component, differential pressure sensor installs on differential pressure conversion module to fix on the casing, temperature control element installs inside the casing, electrical interface and differential pressure sensor, temperature control element are connected, and fix on the casing, wherein: the shell is used for fixing all parts of the sensor and protecting internal components from mechanical and vibration damage and shielding electromagnetic interference; the gas inlet is used for connecting a gas pipeline and providing a gas inlet interface for the sensor; the gas outlet is used for connecting a gas pipeline and providing a connector for gas to flow out of the sensor; the gas preheating module is used for preheating and rectifying the inflowing gas to be detected; the differential pressure conversion module is used for converting the concentration of the gas to be detected into differential pressure change; the differential pressure sensor is used for measuring a differential pressure change value of the differential pressure conversion module; the temperature control element is used for controlling the heater to work according to a set value and the result of the measurement of the airflow temperature so as to achieve the effect of controlling the airflow temperature; and the electrical interface is used for supplying power to the gas concentration measuring device and outputting the measuring result of the device. The gas to be measured flows in from the test space through the gas pipeline, and the gas to be measured flows out from the device after being sensed by the gas concentration measuring device.
According to the embodiment of the present disclosure, the gas preheating module comprises a gas inlet end of the gas preheating module, a gas outlet end of the gas preheating module, a gas flow channel, a heating element and a temperature control unit, the gas inlet end of the gas preheating module is connected with the gas inlet, the gas outlet end of the gas preheating module is connected with the differential pressure conversion module, the gas inlet end of the gas preheating module is connected with the gas outlet end of the gas preheating module through the gas flow channel, and the temperature control unit and the heating element are installed on the gas flow channel, wherein: the gas inlet end of the gas preheating module is used for introducing gas into the gas preheating module and realizing mechanical connection with the gas inlet; the gas outlet end of the gas preheating module is used for connecting the differential pressure conversion module and conveying the preheated gas to the differential pressure conversion module; the gas flow channel is used for rectifying gas and transferring heat generated by the heating element into the gas to heat the gas flow; the heating element is used for heating the gas flow channel; and the temperature control unit is used for measuring the air flow problem after the air flow channel is heated.
According to the embodiment of the disclosure, the gas flow channel is not bent, the heat exchange structure with the heat exchange and rectification functions is installed in the flow channel, and the heating component is installed outside the flow channel.
According to the embodiment of the disclosure, the temperature control unit is installed at the downstream of the gas flow in the gas flow passage, adjacent to the gas outlet end of the gas preheating module.
According to the embodiment of the disclosure, the differential pressure conversion module comprises a capillary laminar flow unit, a flow limiting element, a differential pressure measuring hole, an airflow temperature measuring section, a heating element, a flow indicator and a differential pressure conversion module shell; a circular flow channel for gas to flow is arranged in the gas concentration difference conversion section shell, the circular flow channel is provided with a gas inlet and a gas outlet, the gas concentration difference conversion section shell is provided with 2 differential pressure measurement holes along the direction vertical to the axis of the circular flow channel, the distance between projection points of the axis of the differential pressure measurement hole on the axis of the circular flow channel is greater than the length of the capillary laminar flow unit, the axis of the capillary laminar flow unit is overlapped with the axis of the circular flow channel in the gas concentration difference conversion section shell, and the capillary laminar flow unit is arranged between the 2 differential pressure measurement holes; the heating element is arranged outside the shell of the gas concentration difference conversion section and is used for keeping the temperature of the gas flowing through the capillary laminar flow unit and the flow limiting element to be basically constant; the flow limiting element is arranged at the outlet of the circular flow channel of the shell of the gas concentration difference conversion section, the inlet of the flow limiting element is close to one side of the capillary laminar flow unit, the outlet of the flow limiting element is connected with the inlet of the gas flow temperature measuring section, the inlet of the flow indicator is connected with the outlet of the gas flow temperature measuring section, and the outlet of the flow indicator is connected with the gas outlet of the gas concentration sensor, wherein: the capillary laminar flow unit is used for forming differential pressure at two ends of the capillary laminar flow unit when gas flows through the capillary laminar flow unit; the flow limiting element is used for keeping constant volume flow passing through the gas concentration measuring device; the differential pressure measuring hole is used for measuring the differential pressure value before and after the capillary laminar flow unit; the gas flow temperature measuring section is used for measuring the temperature of the gas flowing through the flow limiting element; the heating element is used for keeping the temperature of the gas flowing through the capillary laminar flow unit and the flow limiting element to be basically constant; the flow indicator is used for displaying the state of gas flowing through the differential pressure conversion module; the differential pressure conversion module is composed of a shell, is used for installing a capillary laminar flow unit, a flow limiting element and a heating element, and is used for arranging a differential pressure measuring hole.
According to the embodiment of the disclosure, the length of the pressure measuring pipeline connected with the 2 differential pressure measuring holes on the differential pressure conversion module is equal, and the pressure measuring pipeline is made of a material with weak heat conductivity.
According to the embodiment of the disclosure, the axes of the gas flow channel in the gas preheating module, the capillary laminar flow unit in the differential pressure conversion module, the flow limiting element and the gas flow channel in the gas flow temperature measuring section are preferably located on the same straight line, and the section of the gas flow in the flow channel is circular.
According to the embodiment of the disclosure, the outer wall of the capillary laminar flow unit is attached to the inner wall of the circular flow channel in the gas concentration difference conversion section shell during assembly.
According to the embodiment of the disclosure, the capillary laminar flow unit is characterized by comprising a circular tubular outer wall and circular capillaries, wherein the circular capillaries are arranged in the cylindrical outer wall, the circular tubular outer wall is used for fixing the circular capillaries, flow channels of the capillaries become main channels of airflow to form a laminar flow structure, gaps among the capillaries and gaps between the capillaries and a sleeve are blocked by adhesives, and the airflow flows through the capillary laminar flow unit extremely rarely. The effective flow area of the gas pipeline before entering the differential pressure conversion module is the same as or approximately the same as that of the capillary laminar flow unit.
According to the embodiment of the disclosure, the flow limiting element is characterized in that a micro precise orifice structure is adopted to maintain constant gas volume flow.
According to an embodiment of the present disclosure, the gas concentration measurement device is characterized in that a ratio of a gas outlet to a gas inlet absolute pressure is not higher than 0.528.
As shown in fig. 2, the gas concentration measuring device is composed of a housing base 1, a housing upper cover 2, a gas inlet and outlet panel 3, a gas inlet through joint 4, a gas preheating module gas pipeline 5, a gas preheating module heating clamping block 6, a gas preheating module electric heating unit 7, a gas preheating module through joint 8, a gas preheating module gas low heat conduction hose 9, a gas preheating module temperature measuring three-way joint 10, a gas preheating module thermocouple 11, a differential pressure conversion module housing 12, a differential pressure conversion module electric heating unit 14, a flow limiting element 15, a differential pressure measuring orifice joint 16, an upstream differential pressure measuring hose 17, a downstream differential pressure measuring hose 18, a differential pressure sensor 90-degree elbow 19, a differential pressure sensor mounting clamp 20, a low heat conduction hose 21, a differential pressure conversion module temperature measuring three-way 22, a differential pressure conversion module thermocouple 23, a differential pressure conversion module gas pipeline 24, the device comprises a flow meter connector 25, a flow meter 26, a flow meter mounting clamp 27, a front panel 28, a flow meter-to-gas outlet connecting hose 29, a gas outlet panel mounting through connector 30, a three-hole current signal aviation plug 31, a two-hole power supply aviation plug 32, an electric rear panel 33, a solid state relay 34, a power supply terminal 35, a ship-shaped switch 36, a preheating module temperature controller 37, a differential pressure conversion module temperature controller 38 and a differential pressure sensor 39.
Referring to fig. 3 and 4, the capillary laminar flow unit 13 is installed inside the differential pressure conversion module housing 12, and the positional relationship among the differential pressure conversion module housing 12, the capillary laminar flow unit 13, and the flow restriction element 15 is shown.
The shell base 1 and the shell upper cover 2 form a shell of the gas concentration measuring device, and are used for installing and fixing parts of the gas concentration measuring device and protecting the parts from being damaged by impact. The shell base 1 and the shell upper cover 2 are made of aluminum materials, so that the cost is low, and the anti-electromagnetic interference performance is good. The housing base 1 and the housing upper cover 2 may be made of other lighter materials. The housing upper cover 2 is fixed on the housing base 1 by screws.
The gas inlet and outlet panel 3 is fixed on the shell base 1 through screws, the gas inlet panel is made of stainless steel, and the gas inlet straight joint 4 and the gas outlet panel mounting straight joint 30 are mounted and pressed on the gas inlet and outlet panel 3 through nuts.
The gas inlet straight joint 4 is connected with a gas pipeline 5 of the gas preheating module by a stainless steel cutting sleeve. In order to improve the rectification and preheating effects of the gas preheating module gas pipeline 5 on the gas flowing through, a certain number of stainless steel capillary pipelines are fixed in the gas preheating module gas pipeline 5. Too thin capillary tube diameter can cause too high flow resistance, and the selection of capillary tube diameter and length should be designed in consideration of gas flow and preheating effect. The gas outlet end of the gas pipeline 5 of the gas preheating module is connected with the straight joint 8 of the gas preheating module through a clamping sleeve.
The two gas preheating module heating clamping blocks 6 clamp the gas preheating module gas pipeline 5 through the semicircular grooves in the middle of the inner sides, the gas preheating module gas pipeline 5 is clamped tightly through bolts, and gaps between the gas preheating module heating clamping blocks 6 and the gas preheating module gas pipeline 5 are filled with heat-conducting silicone grease. In order to prevent the components from shaking, the gas preheating module heating clamping block 6 is fixed on the shell base 1 through screws.
The gas preheating module electric heating unit 7 is arranged on the outer side of the two gas preheating module heating clamping blocks 6. The preferred installation is to attach the gas preheating module electric heating unit 7 to the outside of the gas preheating module heating block 6 by heat-resistant glue. The gas preheating module electric heating unit 7 is coated with heat insulation materials to prevent heat from spreading outwards. The gas preheating module electrically heats the unit 7, preferably a product below 24V, to improve the safety of the gas concentration measuring device.
The direct connector 8 of the gas preheating module is connected with the temperature measuring three-way connector 10 of the gas preheating module through a low heat conduction hose 21, and the connection mode between the direct connector and the temperature measuring three-way connector is a clamping sleeve. The low heat conduction hose 21 is used for providing a gas flow path, reducing the heat transfer from the gas pipeline 5 of the gas preheating module and the heating clamping block 6 of the gas preheating module to the temperature measuring three-way joint 10 of the gas preheating module, and reducing the installation inconvenience caused by machining tolerance by a hose connection mode.
One end of the temperature measuring three-way joint 10 of the gas preheating module, which is vertical to the gas flowing direction, is used for installing a thermocouple 11 of the gas preheating module. The gas preheating module thermocouple 11 is used for measuring the temperature of the gas flow flowing through the temperature measuring three-way joint of the gas preheating module. The gas preheating module thermocouple 11, the preheating module temperature controller 37, the gas preheating module electric heating unit 7, the solid-state relay 34, the power supply terminal 35 and a circuit connected between the two form a temperature control loop, and the temperature of the air flow flowing through the temperature measuring three-way joint of the gas preheating module is controlled and regulated.
In order to reduce the volume, the gas preheating module temperature measuring three-way joint 10 and the gas flow inlet 12-1 of the differential pressure conversion module shell 12 are connected through threads as shown in fig. 4. A capillary laminar flow unit 13 is installed in a flow channel of a differential pressure conversion module shell 12, an airflow outlet 12-2 of the differential pressure conversion module shell 12 is connected with a flow limiting element 15 through threads, as shown in figure 3, a differential pressure conversion module electric heating unit 14 is installed on the outer wall of the differential pressure conversion module shell, an upstream differential pressure measuring hole 12-3 and a downstream differential pressure measuring hole 12-4 of the differential pressure conversion module shell 12 are connected with a 2-branch differential pressure measuring hole connector 16 through threads.
The 2 differential pressure measuring hole joints 16 are respectively connected with an upstream differential pressure measuring hose 17 and a downstream differential pressure measuring hose 18 through clamping sleeves, and the two differential pressure measuring hoses 17 and 18 are connected with 2 differential pressure measuring holes of a differential pressure sensor 39 through a differential pressure sensor 90-degree elbow 19. The lengths of the upstream differential pressure measurement hose 17 and the downstream differential pressure measurement hose 18 are the same, and hoses having poor heat conductivity are preferable. The differential pressure sensor 39 is fixed to the housing base 1 by the differential pressure sensor mounting clip 20.
The flow limiting element 15 is connected with a differential pressure conversion module temperature measuring tee 22 through a low heat conduction hose 21, and two ends of the low heat conduction hose 21 are connected in a clamping sleeve mode. The hose 21 is used not only to provide a gas flow path, but also to reduce the heat transfer from the differential pressure conversion module housing 12 to the differential pressure conversion module temperature measurement tee 22, and to reduce the inconvenience of installation due to machining tolerances by means of hose connection.
One end of the temperature measuring tee 22 of the differential pressure conversion module, which is vertical to the gas flowing direction, is used for installing a thermocouple 23 of the differential pressure conversion module. The differential pressure conversion module thermocouple 23 is used for measuring the temperature of the air flow passing through the temperature measuring tee 22 of the differential pressure conversion module. The differential pressure conversion module thermocouple 23, the differential pressure conversion module temperature controller 38, the differential pressure conversion module electric heating unit 14, the solid-state relay 34, the power supply terminal 35 and the lines connected between the two form a temperature control loop for controlling and adjusting the temperature of the air flow passing through the temperature measuring tee 22 of the differential pressure conversion module.
The gas flow outlet end of the temperature measuring tee 22 of the differential pressure conversion module is connected with a gas pipeline 24 of the differential pressure conversion module, and the pipeline 24 is connected with the gas inlet section of a flowmeter 26 through a flowmeter connector 25. The flow meter 26 is fixed to the front panel 28 by a flow meter mounting clip 27. The front panel 28 is fixed to the housing base 1 by screws. The gas outlet end of the flow meter 26 is connected to a gas outlet connection hose 29 via another flow meter connection 25. The other end of the hose 29 is connected to a gas outlet panel mounting through fitting 30. To this end, the gas inlet feedthrough 4 and the gas outlet panel mounting feedthrough 30 constitute a gas flow path by many elements. As the gas flows through this path, the gas volume concentration is converted into a differential pressure signal.
Boat switch 36, preheat module temperature controller 37, and differential pressure transfer module temperature controller 38 are all secured to front panel 28. The flow meter 26, boat switch 36, preheat module temperature control 37, and differential pressure transfer module temperature control 38 are all mounted on a side panel for user operation.
Three-hole current signal aviation plug 31, two-hole power supply aviation plug 32 pass through the screw and install on electric rear panel 33, and electric rear panel 33 passes through the screw and installs at casing base 1. The three-hole current signal aviation plug is used for transmitting a current signal generated by the differential pressure sensor. The two-hole power supply aviation plug 32 is used for supplying power and is connected with a power supply terminal 35 and a ship-shaped switch 36. The boat switch 36 can control the switching of the entire electrical part of the gas concentration measuring apparatus.
In this embodiment, as shown in FIGS. 5 and 6, the capillary 13-1 is held by the sleeves (including the first sleeve 13-2 and the second sleeve 13-3) so that either capillary does not move under the influence of a possible air flow. The length of the capillary 13-1 is equal to the sum of the lengths of the sleeve 13-2 and the sleeve 13-3.
According to the embodiment of the disclosure, the dynamic viscosity of the gas to be measured is mu, the density of the gas to be measured is rho, the number of capillaries is n, the Reynolds number is Re, and QVIs the flow rate; the inner diameter of a single capillary tube is dLFEThe expression is as follows:
The number of the capillary tubes is 139, the inner diameter is 0.4mm, the wall thickness is 0.1mm, the length is 70mm, and the flow area of all the capillary tubes is about 17.5mm2The flow area of the front end air inlet pipeline is about 16.4mm2Two, twoThey are close to each other.
If the mechanical force between the components is not sufficient to secure the capillary 13-1, a high temperature resistant (e.g., not less than 120 ℃) adhesive may be applied to the outer wall of the capillary and the inner wall of the sleeve, and the adhesive used may not react with the gas being measured. Fig. 6 shows a schematic view of the assembled capillary flow cell with the end faces of the capillary bundle as flush as possible with the end faces of the sleeve.
Further, in the embodiments of the present disclosure, part of the control board card may also be installed in the gas concentration measurement apparatus. The control board card in the gas concentration measuring device can convert the differential pressure signal into a concentration signal and transmit the concentration signal to the upper computer control software in the form of a digital signal. A small display screen is arranged on the shell, and can display the concentration value on the gas concentration measuring device. The control board card can also control the heating element to work according to the temperature value of the gas. The gas concentration measuring device has stronger data processing and displaying capacity, adopts digital signal output, is more favorable for signal transmission, and is suitable for application scenes in which the gas concentration measuring device is dispersedly arranged for use.
Further, in the embodiment of the present disclosure, the gas preheating module and the differential pressure conversion module may be manufactured into an integral component by a finish machining method, instead of each discrete device, so as to further reduce the volume of the equipment, reduce the fluctuation of the airflow, and reduce the assembly difficulty. For example, the present embodiment discloses a structure of a gas preheating module and a differential pressure conversion module, which is more compact, has higher precision, and is more conducive to comprehensive analysis of measurement results.
According to the embodiment of the present disclosure, as shown in fig. 7, the gas preheating module includes a gas inlet through joint 61, a gas preheating module gas pipeline 64, and a gas preheating module temperature measuring three-way joint 65; the gas preheat module heater clamp block 62 is mounted outside of the gas preheat module gas line 64 to heat the fluid in the gas line. In order to improve the heating effect, a groove 63 for mounting the electric heating silica gel pad of the gas preheating module heating clamping block is processed on the surface of the gas preheating module heating clamping block.
The differential pressure conversion module comprises a differential pressure conversion module shell 69, a micro orifice plate current limiting element 72 and a differential pressure conversion module temperature measuring tee 74 which are sequentially connected through a clamping sleeve and threads; an upstream differential pressure measurement orifice fitting 67 and a downstream differential pressure measurement orifice fitting 70 are threadably mounted to an upper portion of the differential pressure conversion module housing 69. An upstream capillary rectifying element 66, a capillary laminar flow unit 68 and a downstream capillary rectifying element 71 are arranged in a gas flow channel in the middle of a differential pressure conversion module shell 69 along the gas flow direction, and the projection positions of pressure measuring holes of an upstream differential pressure measuring hole joint 67 and a downstream differential pressure measuring hole joint 70 in the gas flow channel are respectively positioned between 66 and 68, and between 68 and 71.
The added upstream capillary flow straightening element 66 serves to straighten the gas flowing past and reduce the fluctuations in the measured pressure at 67. When the airflow flows through the micro orifice plate flow-limiting element 72, pressure fluctuation is generated at the pressure measuring hole at the upstream of the micro orifice plate flow-limiting element 72 due to the fact that the size of the orifice plate is suddenly smaller than the cross section area of the upstream airflow flow channel, and the downstream capillary rectifying element 71 is used for reducing the pressure fluctuation, so that the measurement accuracy is improved.
In the disclosed embodiment, upstream capillary fairing 66 and downstream differential pressure measurement orifice junction 70 are 15mm in length. Each of the capillary tubes consists of 139 capillary tubes with the inner diameter of 0.4mm, the wall thickness of 0.1mm and the length of 15mm, sleeve tubes with the outer diameter of 10mm and the wall thickness of 1mm are arranged outside the capillary tubes, the length of the sleeve tubes is also 15mm, and the end faces of the sleeve tubes are flush with the end faces of the inner capillary tubes.
The capillary laminar flow unit 68 is composed of 139 capillaries with inner diameter of 0.4mm, wall thickness of 0.1mm and length of 70mm, 2 sleeves with outer diameter of 10mm and wall thickness of 1mm and sleeve with length of 35mm are arranged outside, the gap between the capillaries is sealed by using an adhesive, and the capillaries are fixed in the sleeves and cannot move. The effective capillary flow area of the capillary laminar flow unit 68, the upstream capillary flow straightening element 66 and the downstream capillary flow straightening element 71 is 17.5mm2And the flow area (16.4 mm) of the air inlet pipeline at the temperature-measuring three-way joint of the front-end gas preheating module2) Proximity is beneficial to reduce pressure fluctuations caused by gas flow.
In order to improve the measurement accuracy and the usability, the absolute pressure in the gas flow channel is measured at the position of a pressure measuring hole on the upstream of the differential pressure conversion module. The present embodiment adds an absolute pressure gauge at the upstream differential pressure measurement orifice joint 67 for monitoring the absolute pressure value in the gas flow passage. This absolute pressure value can be used to correct the differential pressure versus concentration. A typical application scenario is that when the concentration of the fire extinguishing agent in an aircraft engine compartment is tested in an air test flight mode, the pressure value at a measuring point changes and is different from the environmental pressure when a ground sensor is used for correction, and at the moment, the relation between differential pressure and concentration can be corrected through the absolute pressure value in a flow channel.
The absolute pressure value has another function of judging the validity of the measurement data and correcting the validity. A typical application scenario is that when the fire extinguishing agent in the space to be measured is suddenly sprayed, the pressure at the measuring point rises, and in some cases, the pressure rise is transmitted to the upstream differential pressure measurement orifice joint 67, and the pressure at the downstream differential pressure measurement orifice joint 71 does not rise yet, so that an error is brought about. At this time, if the pressure gauge detects a sudden change or abnormal rise of the pressure, the absolute pressure gauge may determine that the differential pressure value at that time is abnormal by an algorithm, and correct the abnormal differential pressure value by subtracting the absolute pressure rise difference in the differential pressure conversion, for example.
In the embodiment of the present disclosure, as shown in fig. 8, a plurality of heat insulation panels are additionally installed outside the structure of the gas preheating module and the differential pressure conversion module, so that the heat diffusion of the electric heating element can be effectively reduced through the installation of the heat insulation panels, the influence of the environment on the measurement is reduced, and the damage of mechanical force and vibration to the gas preheating module and the differential pressure conversion module can be prevented.
Furthermore, in the embodiment of the present disclosure, a micro-electromechanical method may be adopted, the size of the gas concentration measurement device is further reduced, the differential pressure gas concentration measurement device is installed on the circuit board, the projection areas of the gas preheating module and the differential pressure conversion module do not exceed the area of the circuit board, and are fixed on the circuit board and the housing, and the circuit board is provided with a temperature measurement and control circuit, so as to realize temperature control of the gas in the gas preheating module and the differential pressure conversion module. The volume of the gas concentration measuring apparatus can be controlled to be not more than 10cm long, 5cm high, 4cm wide. The present embodiment can be applied to applications with strict size requirements, such as real-time monitoring of a certain gas concentration in a device.
The present disclosure also provides a system for gas concentration measurement, as shown in fig. 9, 10 and 14, the system for gas concentration measurement is composed of a gas concentration measurement device and a control device, the gas concentration measurement device and the control device are connected with an electric line through a signal transmission line, wherein:
the system for measuring the gas concentration comprises at least one gas concentration measuring device, a gas concentration measuring device and a gas concentration measuring device, wherein the gas concentration measuring device is used for converting the gas concentration into an electric signal;
and the control device is used for communicating with the gas concentration measuring device, supplying power and converting the electric signal generated by the gas concentration measuring device into a concentration value.
According to an embodiment of the present disclosure, the control device may be operable to determine an empirical relationship between gas volume concentration and differential pressure value for the gas to be measured, as shown in fig. 11. The relationship between the gas volume concentration and the differential pressure value is described by a quadratic exponential decay curve.
The measuring device is connected with the control device through an electric circuit, the measuring device transmits a measuring signal to the control device, the control device processes and converts the measuring signal into a concentration signal and outputs the concentration signal through the I/O equipment, and the control device supplies power to the measuring device and controls the working state of the measuring device.
As shown in fig. 9 and 10 in combination, 8 gas concentration measurement devices 40 are mounted in the cabinet by a gas concentration measurement device fixing box 41. The fixed inserting box 41 of the gas concentration measuring device is reserved with fixed slot positions of the gas concentration measuring device 40, gaps through which air can flow are reserved among the slot positions, ventilation air can flow through the gaps, and heat emitted by the gas concentration measuring device 40 is prevented from interfering other gas concentration measuring devices 40.
The cooling and ventilation equipment plug box 42 is installed on the gas concentration measuring device fixing plug box, and the cooling and ventilation equipment plug box 42 generates airflow blown into the gas concentration measuring device fixing plug box 41, so that temperature interference between the gas concentration measuring devices 40 is prevented.
The upper portion of the cooling fan box 42 is provided with a keyboard/mouse tray 43. The keyboard/mouse tray 43 is provided with a control device box 44 at the upper part. The control device is mounted inside the control device box 44.
A display 45 is arranged on the upper part of the control device plug box 44, and a power supply plug box 46 is arranged on the upper part of the display 45. The power supply outlet 46 is used to safely supply power to the various electrical devices within the cabinet.
The cabinet headspace 48 is located at the lower portion of the gas concentration measurement device fixing insert 41. In this embodiment, the cabinet headspace 48 allows for another gas concentration measurement device fixing insert 41 to be installed, extending the number of gas concentration measurement devices to 16. In some applications, the cabinet headspace 48 is used to house printers and maintenance kits, which improves the ease of use of the system.
Two sides of the cabinet 47 are provided with 2 side access doors 52, the rear part of the cabinet 47 is provided with a rear access door 50, an interface panel 51 is arranged under the rear access door 50, the interface panel 51 is provided with a power output mounting hole 51-1, a power input connector mounting hole 51-2, 8 cabinet gas inlet penetrating plate joints 51-3 and 8 cabinet gas outlet penetrating plate joints 51-4, and the joints are respectively connected with a gas inlet through joint 4 and a gas outlet panel mounting through joint 30 on a gas concentration measuring device through pipelines. The connection scheme can effectively reduce the complexity of system connection in the test and avoid damaging the gas concentration measuring device. In some applications, if there are contaminants in the test space such as dust that may enter the gas line, a filter may be installed in the gas line between the interface panel 51 and the gas inlet feedthrough 4 to prevent the contaminants from clogging up after entering the gas concentration measurement device.
The present disclosure also provides a gas concentration measuring method, as shown in fig. 12, the gas concentration measuring method including:
operation S1: carrying out preheating treatment on the gas concentration measuring device;
operation S2: inputting the gas to be measured in the space into the gas concentration measuring device after preheating treatment, and recording a differential pressure value; and
operation S3: and determining the concentration of the gas to be detected according to the empirical relationship between the differential pressure value and the volume concentration and differential pressure value of the gas to be detected.
According to an embodiment of the present disclosure, the operation S1 includes:
operation S11: introducing gas to be measured with the concentration of 0 or a known concentration into the gas concentration measuring device; and:
operation S12: the preheating module electric heating unit and the differential pressure conversion module electric heating unit are used for heating, so that the temperature values measured by the preheating module thermocouple and the differential pressure conversion module thermocouple are stable and the same, and the preheating treatment is completed.
According to an embodiment of the present disclosure, more specifically, as shown in fig. 13, a gas concentration measurement method may include:
step 101: connecting a test point in the test space with a gas concentration measuring device by using a gas pipeline;
step 102: checking whether a state of gas flowing through the gas concentration measuring device is normal;
step 103: preheating the gas concentration measuring device to a set temperature, and checking an output signal of the measuring device;
step 104: calibrating the gas concentration measurement device with a target gas of known concentration;
step 105: carrying out tests and recording data;
step 106: after the test is finished, cooling the gas concentration measuring device, and purging residual gas in the measuring device;
step 101, connecting and checking a gas pipeline. And according to the test field condition, connecting the test point in the test space with a gas inlet interface of the corresponding gas concentration measuring device on the cabinet by using a gas pipeline with the same length and specification, and checking whether the gas inlet joint of the corresponding gas concentration measuring device on the cabinet is correctly connected with the gas inlet straight joint 4 of the gas concentration measuring device. And connecting a gas outlet connector of the gas cabinet on the cabinet and a vacuum pump by using gas pipelines with the same length and specification, and checking whether the gas outlet connector of the corresponding gas concentration measuring device on the cabinet is correctly connected with the direct connector 30 arranged on the gas outlet panel of the gas concentration measuring device.
The gas flow conditions are checked, step 102. The vacuum pump is started, and whether the gas flow state of each gas concentration measuring device is normal, and whether gas leakage and blockage occur is checked through a vacuum meter on the vacuum pump and a flow meter 26 on the gas concentration measuring device. If there is a problem, the maintenance is performed. The next step was carried out after confirming that there was no problem.
Step 103, preheating the gas concentration measuring device, and checking the output signal of the gas concentration measuring device. And under the condition that the gas normally flows through the gas concentration measuring device, starting the control device, collecting output signals of the gas concentration measuring device, and starting the heating of each gas concentration measuring device. At this time, the gas entering the gas concentration measuring device should be at a target gas concentration of 0 or a certain stable known concentration. When the gas preheating module thermocouples and the differential pressure conversion module thermocouples of the gas concentration measuring devices have stable and same measured temperature values, the preheating of the gas concentration measuring devices is completed. And checking whether the output signal of the gas concentration measuring device collected by the control device is stable. And entering the next step after the signal of the gas concentration measuring device is stable.
In step 104, the differential pressure and concentration relationship of the gas concentration measurement device is calibrated. When target gas with known concentration is placed at a test point in the test space, the gas is sucked into the gas pipeline and flows into the gas concentration measuring device. A known concentration of a target gas may be stored in a gas sampling bag or tank. It should be noted that the process and environmental conditions of the target gas with known concentration entering the gas pipeline should be as similar as possible to the test environment, or the influence of different test environments can be avoided through reasonable design, so that the calibration accuracy can be improved. When the output signal of the gas concentration measuring device changes after the target gas with known concentration flows through the gas concentration measuring device, the change value is recorded. By repeating the process, corresponding data points of the signal of the gas concentration measuring device and the gas concentration can be obtained, and the corresponding relation between the signal of the gas concentration measuring device and the gas concentration can be obtained by fitting the data points by adopting an empirical model. In many cases, all points do not need to be calibrated each time, only some points need to be calibrated, and the corresponding relation can be obtained through known empirical model fitting. When environmental conditions such as chamber temperature, humidity and test conditions are similar, the existing correspondence can be used, i.e. this step can be skipped.
The step 105, test development. After the test space has been prepared for testing, the test is started and the control device records the target gas concentration versus time curves for a plurality of measurement points.
In step 106, the test is completed, and the system is shut down. After the test is completed, the test data is saved, and the heating of the gas concentration measuring device is closed. At the moment, gas is continuously introduced into the gas concentration measuring device, heated elements in the gas concentration measuring device are cooled, and the vacuum pump is closed when temperature values measured by a gas preheating module thermocouple and a differential pressure conversion module thermocouple of the gas concentration measuring device are reduced to acceptable levels. If the target gas is toxic or corrosive, it is ensured that the gas concentration measuring device and the target gas in the gas pipeline are flushed clean by air before the vacuum pump is turned off. And finally closing the control device. If the test is not carried out for a long time, the air inlet on the cabinet is plugged after the system is closed, so that pollutants such as dust are prevented from entering.
It should be understood that the above embodiments are only exemplary, and the gas concentration measuring apparatus and method of the present disclosure can be applied to the measurement of the concentration of any gas to be measured in a plurality of spaces to be measured, for example, a structure in which the test space is protected by a fire extinguishing system, such as an engine compartment. The engine compartment is only one representative structure in a non-limiting embodiment (the engine compartment is provided with a gas fire extinguishing system), and any other test space, such as a battery compartment of an energy storage power station, an engine compartment, a battery compartment or a weapon compartment of an air, land or water vehicle, etc., can also be applied with the gas concentration measuring device and method of the present disclosure, and is not limited herein.
So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. Further, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by those of ordinary skill in the art.
From the above description, those skilled in the art should clearly recognize that the gas concentration measuring apparatus and method of the present disclosure are applicable.
In summary, the present disclosure provides a gas concentration measuring device and method, which have high measurement accuracy, can be calibrated, have good repeatability, can adapt to the change of the test environmental factors, can be used for analyzing whether the gas concentration meets the requirements, and have a wide application prospect.
It should also be noted that directional terms, such as "upper", "lower", "front", "rear", "left", "right", and the like, used in the embodiments are only directions referring to the drawings, and are not intended to limit the scope of the present disclosure. Throughout the drawings, like elements are represented by like or similar reference numerals. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure.
And the shapes and sizes of the respective components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.
Unless otherwise indicated, the numerical parameters set forth in the specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present disclosure. In particular, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Generally, the expression is meant to encompass variations of ± 10% in some embodiments, 5% in some embodiments, 1% in some embodiments, 0.5% in some embodiments by the specified amount.
Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.
The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element or any ordering of one element from another or the order of manufacture, and the use of the ordinal numbers is only used to distinguish one element having a certain name from another element having a same name.
In addition, unless steps are specifically described or must occur in sequence, the order of the steps is not limited to that listed above and may be changed or rearranged as desired by the desired design. The embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e., technical features in different embodiments may be freely combined to form further embodiments.
Those skilled in the art will appreciate that the modules in the device in an embodiment may be adaptively changed and disposed in one or more devices different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component, and furthermore they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification, including the accompanying claims, abstract, and drawings, and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or elements are mutually exclusive. Each feature disclosed in this specification, including the accompanying claims, abstract, and drawings, may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Also in the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (10)
1. A gas concentration measurement device comprising:
the preheating module is used for preheating and rectifying the input gas to be detected and then outputting a first-stage gas;
the differential pressure conversion module is connected with the preheating module and is used for enabling the first-stage gas flowing through to generate a differential pressure change value; and
the processing module is used for obtaining the volume concentration of the gas to be detected according to the differential pressure change value;
the differential pressure conversion module comprises a capillary laminar flow unit with a plurality of capillaries, and the flow channels of the capillaries become main channels of air flow to form a laminar flow structure.
2. The gas concentration measurement device of claim 1, the preheat module comprising:
the gas flow channel is used for rectifying the gas to be detected;
the preheating module electric heating unit is used for heating the gas flow channel so as to conduct and heat the gas to be detected; and
the preheating module temperature control unit is used for measuring and regulating the temperature of the gas to be measured;
the gas flow channel is not bent, and a plurality of capillary pipelines are arranged in the gas flow channel.
3. The gas concentration measurement device of claim 2, the preheat module temperature control unit comprising a preheat module thermocouple disposed perpendicular to a gas flow direction.
4. The gas concentration measurement device of claim 1, the differential pressure conversion module further comprising:
the differential pressure conversion module shell is coated outside the capillary laminar flow unit, an upstream differential pressure measuring hole is arranged at the upstream end corresponding to the capillary laminar flow unit, and a downstream differential pressure measuring hole is arranged at the downstream end corresponding to the capillary laminar flow unit;
the two ends of the differential pressure sensor are respectively connected to the upstream differential pressure measuring hole and the downstream differential pressure measuring hole and are used for measuring the differential pressure between the differential pressure measuring holes; and
and the flow limiting element is positioned at the downstream outlet of the differential pressure conversion module shell and is used for keeping the constant volume flow of the gas flowing through the gas concentration measuring device.
5. The gas concentration measurement device of claim 4, the differential pressure conversion module further comprising:
the differential pressure conversion module electric heating unit is used for heating the differential pressure conversion module; and
and the differential pressure conversion module temperature control unit is used for measuring and regulating the temperature of the gas to be measured flowing through the capillary laminar flow unit and the flow limiting element, and comprises a differential pressure conversion module thermocouple which is arranged in a direction perpendicular to the gas flowing direction.
6. The gas concentration measurement device of claim 4, the differential pressure conversion module further comprising:
the upstream capillary rectifying element is positioned between the upstream inlet of the differential pressure conversion module shell and the upstream differential pressure measuring hole;
the downstream capillary rectifying element is positioned between the downstream outlet of the differential pressure conversion module shell and the downstream differential pressure measuring hole; and
and the absolute pressure gauge is arranged at the upstream differential pressure measuring hole and used for monitoring the absolute pressure value in the gas flow channel and improving the measuring precision.
7. The gas concentration measurement device according to claim 1, the capillary flow cell further comprising:
the sleeve comprises a first sleeve and a second sleeve which are sleeved outside the plurality of capillary tubes from two sides respectively; and
and the adhesive is coated on the outer wall of the capillary and the inner wall of the sleeve and used for fixing the multiple capillaries so that the capillaries do not move under the action of the airflow of the gas to be detected.
8. The gas concentration measuring apparatus according to claim 1, a tube diameter d of the capillary tubeLFEIs expressed as:
mu is the dynamic viscosity of the gas to be measured, n is the number of capillaries, rho is the density of the gas to be measured, Re is the Reynolds number, and QVIs the flow rate.
9. A gas concentration measurement method for performing concentration measurement of a gas to be measured using the gas concentration measurement apparatus according to any one of claims 1 to 8, the measurement method comprising:
operation S1: carrying out preheating treatment on the gas concentration measuring device;
operation S2: inputting the gas to be measured in the space into the gas concentration measuring device after preheating treatment, and recording a differential pressure value; and
operation S3: and determining the concentration of the gas to be detected according to the empirical relationship between the differential pressure value and the volume concentration and differential pressure value of the gas to be detected.
10. The gas concentration measurement method according to claim 9, the operation S1 including:
operation S11: introducing gas to be measured with the concentration of 0 or a known concentration into the gas concentration measuring device; and:
operation S12: the preheating module electric heating unit and the differential pressure conversion module electric heating unit are used for heating, so that the temperature values measured by the preheating module thermocouple and the differential pressure conversion module thermocouple are stable and the same, and the preheating treatment is completed.
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| CN113671119A (en) * | 2021-08-02 | 2021-11-19 | 德尔格安全设备（中国）有限公司 | Gas detection device and temperature compensation method thereof |
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