CN111948091A - Gas concentration measuring device and method - Google Patents

Abstract

The present disclosure provides a gas concentration measurement device, comprising: a preheating module for preheating and rectifying the input gas to be measured and then outputting the first-stage gas; a differential pressure conversion module, connected with the preheating module, for making The first-stage gas flowing through generates a differential pressure change value; and a processing module is used to obtain the volume concentration of the gas to be measured according to the differential pressure change value. Wherein, the differential pressure conversion module includes a capillary laminar flow unit with a plurality of capillaries, and the flow channels of the plurality of capillaries become the main channels of the air flow, forming a laminar flow structure. The present disclosure also provides a gas concentration measurement method, which adopts the above-mentioned gas concentration measurement device to measure the concentration of the gas to be measured.

Description

Gas concentration measuring device and method

technical field

The present disclosure relates to the technical field of instruments and equipment, and in particular, to a gas concentration measurement device and method.

Background technique

With the development of science and technology, it is sometimes necessary to measure the concentration of a certain gas in a space in real time. For example, to confirm whether the amount of gas fire extinguishing agent carried by a fire extinguishing system in a vehicle or aircraft is qualified, it is necessary to release the fire extinguishing agent to the required level. For the protected space, the volume concentration of the fire extinguishing agent in representative positions in each area of the space to be protected is simultaneously recorded by the measuring system. The concentration of the extinguishing agent must be higher than a known effective extinguishing concentration, which is the concentration of the extinguishing agent that is sufficient to extinguish a fire that may occur in the protected area within a certain period of time.

Patent CN109540747A discloses an airborne measuring device for the concentration of fire extinguishing agent in an aircraft power unit cabin, but the patent does not provide an implementation of the laminar flow differential pressure measuring device in a single-channel measuring unit, which is difficult for those skilled in the art to implement. Patent CN103163046A discloses a gas fire extinguishing agent concentration measuring device, but the patent adopts the overall heating method for the constant temperature and constant current micro-pressure difference generator, which is easily affected by environmental factors; the patent uses a flow controller to This causes the flow between the 4 channels to be unbalanced due to factors such as blockage and processing technology, which will lead to measurement errors. Patent CN110844118A discloses a test device and method for testing the differential pressure of a multi-void structure, but this patent adopts the scheme of immersing the porous screen in oil, which will cause pollution during use and make maintenance difficult. Patent CN105424546 discloses a concentration measurement device for a fire extinguishing agent concentration measurement system, but the through-hole solution adopted in this patent will bring inconvenience to equipment processing; the solution of the pressure stabilization chamber will cause gas mixing, which is not conducive to improving the response time; temperature; The sensor detects the temperature of the heating block and the pressure measuring block, not the temperature of the gas. When the environment changes, it will affect the measurement accuracy.

Therefore, how to obtain higher-precision gas concentration measurement results is an urgent technical problem to be solved.

public content

(1) Technical problems to be solved

Based on the above problems, the present disclosure provides a gas concentration measurement device and method to alleviate the technical problems in the prior art such as high processing difficulty, difficult maintenance, large fluctuation of measured values and large errors in gas concentration measurement.

(2) Technical solutions

In one aspect of the present disclosure, there is provided a gas concentration measurement device, comprising: a preheating module for preheating and rectifying the input gas to be measured and then outputting the first-stage gas; a differential pressure conversion module, which is connected to the preheating The modules are connected to generate a differential pressure change value for the first stage gas flowing through; and a processing module is used to obtain the volume concentration of the gas to be measured according to the differential pressure change value; wherein the differential pressure The conversion module includes a capillary laminar flow unit with a plurality of capillaries, and the flow channels of the plurality of capillaries become the main channels of the gas flow, forming a laminar flow structure.

According to an embodiment of the present disclosure, the preheating module includes: a gas flow channel for rectifying the gas to be measured; an electric heating unit in the preheating module for heating the gas flow channel, thereby conducting conduction heating of the gas to be measured; and a preheating module temperature control unit for measuring and regulating the temperature of the gas to be measured; wherein, the gas flow channel is not bent, and a plurality of capillary pipelines are arranged inside.

According to an embodiment of the present disclosure, the preheating module temperature control unit includes a preheating module thermocouple, which is arranged perpendicular to the gas flow direction.

According to an embodiment of the present disclosure, the differential pressure conversion module further includes: a differential pressure conversion module casing, which is wrapped around the capillary laminar flow unit, and an upstream differential pressure measurement hole is provided corresponding to the upstream end of the capillary laminar flow unit , corresponding to the downstream end of the capillary laminar flow unit is provided with a downstream differential pressure measurement hole; a differential pressure sensor, the two ends of which are respectively connected to the upstream differential pressure measurement hole and the downstream differential pressure measurement hole for measuring differential pressure measurement the differential pressure between the orifices; and a flow restricting element located at the downstream outlet of the differential pressure conversion module housing for maintaining a constant volume flow through the gas concentration measuring device.

According to an embodiment of the present disclosure, the differential pressure conversion module further includes: an electric heating unit for the differential pressure conversion module, for heating the differential pressure conversion module; and a temperature control unit for the differential pressure conversion module, for measuring and regulating all the The temperature of the gas to be measured in the capillary laminar flow unit and the limiting element is described, and the temperature control unit of the differential pressure conversion module includes a thermocouple of the differential pressure conversion module, which is arranged perpendicular to the gas flow direction.

According to an embodiment of the present disclosure, the differential pressure conversion module further includes: an upstream capillary rectifier element located between the upstream inlet of the differential pressure conversion module housing and the upstream differential pressure measurement hole; a downstream capillary rectifier element located in the upstream differential pressure measurement hole; between the downstream outlet of the differential pressure conversion module casing and the downstream differential pressure measurement hole; and an absolute pressure gauge, which is arranged at the upstream differential pressure measurement hole for monitoring the absolute pressure value in the gas flow channel and improving measurement accuracy.

According to an embodiment of the present disclosure, the capillary laminar flow unit further includes: a sleeve, including a first sleeve and a second sleeve, respectively sleeved outside the plurality of capillaries from both sides; and an adhesive, coated The outer wall of the capillary tube and the inner wall of the sleeve are used to fix the plurality of capillary tubes so that they do not move under the action of the gas flow of the gas to be measured.

According to the embodiment of the present disclosure, the formula of the diameter d _LFE of the capillary is expressed as:

其中，μ为待测气体的动力黏度，n为毛细管的数量，ρ为待测气体的密度，Re为雷诺数，Q_V为流量。

Among them, μ is the dynamic viscosity of the gas to be measured, n is the number of capillaries, ρ is the density of the gas to be measured, Re is the Reynolds number, and Q _V is the flow rate.

Another aspect of the present disclosure provides a method for measuring gas concentration, using the gas concentration measuring device described in any one of the above to measure the concentration of a gas to be measured, the measuring method comprising: operation S1: Preliminary heat treatment; operation S2: input the gas to be measured in the space into the preheated gas concentration measuring device, and record the differential pressure value; and operation S3: according to the differential pressure value and the volume concentration of the gas to be measured and the differential pressure The empirical relationship between the values determines the gas concentration to be measured.

According to the embodiment of the present disclosure, the operation S1 includes: operation S11 : passing the gas to be measured with a concentration of 0 or a known concentration into the gas concentration measuring device; and: operation S12 : heating the unit and the differential pressure through the preheating module electrically The electric heating unit of the conversion module performs heating, so that the temperature values measured by the thermocouple of the preheating module and the thermocouple of the differential pressure conversion module are stable and the same, and the preheating process is completed.

(3) Beneficial effects

It can be seen from the above technical solutions that the gas concentration measuring device and method of the present disclosure have at least one or a part of the following beneficial effects:

(1) Fast response speed;

(2) High measurement accuracy;

(3) Good long-term stability;

(4) Easy to use and maintain;

(5) It can be used not only for rapid measurement of gas concentration, but also for long-term monitoring of gas concentration.

Description of drawings

FIG. 1 is a schematic diagram of the composition of a gas concentration measuring device according to an embodiment of the present disclosure.

FIG. 2 is an exploded view of a gas concentration measuring device according to an embodiment of the present disclosure.

3 is a partial cross-sectional structural schematic diagram of a differential pressure conversion module according to an embodiment of the present disclosure.

FIG. 4 is a perspective structural schematic diagram of a differential pressure conversion module according to an embodiment of the present disclosure.

FIG. 5 is a schematic diagram of the assembly of the capillary laminar flow unit according to the embodiment of the present disclosure.

FIG. 6 is a schematic structural diagram of a capillary laminar flow unit according to an embodiment of the present disclosure.

7 is a schematic structural diagram of a differential pressure conversion module and a preheating module according to another embodiment of the present disclosure.

FIG. 8 is a schematic structural diagram of a differential pressure conversion module and a preheating module of another embodiment of the present disclosure after installing a thermal insulation shell.

FIG. 9 is a schematic diagram of a gas concentration measurement system according to an embodiment of the present disclosure installed in a cabinet.

FIG. 10 is a schematic diagram of a rear interface of the cabinet shown in FIG. 9 .

FIG. 11 is a schematic diagram of the empirical relationship between the gas volume concentration and the differential pressure value according to an embodiment of the present disclosure.

FIG. 12 is a schematic flowchart of a gas concentration measurement method according to an embodiment of the present disclosure.

FIG. 13 is a schematic flowchart of the operation of the gas concentration measurement system according to the 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 Symbols of Main Elements of the Embodiments of the Present Disclosure in the Drawings]

1 Shell base

2 shell cover

3 Gas inlet and outlet panels

4. 61 Gas inlet straight connector

5. 64 Gas pipeline of gas preheating module

6. 62 Gas preheating module heating clamp

7 Gas preheating module Electric heating unit

8 Gas preheating module feed-through connector

9 Gas low thermal conductivity hose for gas preheating module

10. 65 Gas preheating module temperature measuring tee joint

11 Thermocouple for gas preheating module

12, 69 Differential pressure conversion module shell

12-1 Air Inlet

12-2 Air 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 The first sleeve

13-3 Second sleeve

14 Differential pressure conversion module electric heating unit

15 Current limiting element

16 Differential pressure measuring hole connector

17 Upstream differential pressure measuring hose

18 Downstream differential pressure measuring hose

19 Differential pressure sensor 9() degree elbow

20 Differential pressure sensor installation clip

21 Differential pressure conversion module low thermal conductivity hose

22 Differential pressure conversion module temperature measurement tee

23 Differential pressure conversion module thermocouple

24 Differential pressure conversion module gas line

25 Flowmeter connector

26 Flowmeter

27 Flowmeter mounting clip

28 Front panel

29 Flow meter to gas outlet connecting hose

30 Gas Outlet Panel Mount Straight Fitting

31 three-hole current signal aviation plug

32 two-hole power aviation plug

33 Electrical rear panel

34 Solid State Relays

35 Power supply terminal

36 Rocker switch

37 Preheat module temperature controller

38 Differential pressure conversion module temperature controller

39 Differential pressure sensor

40 Gas concentration measuring device

41 Gas concentration measuring device fixed sub-box

42 Cooling ventilation equipment sub-box

43 Keyboard/Mouse Tray

44 Control gear box

45 Displays

46 Power supply box

47 Cabinets

48 Cabinet reserved space

49 Cabinet Wheels

50 Rear Access Door

51 Interface panel

51-1 Power output mounting holes

51-2 Power input connector mounting hole

51-3 Cabinet Gas Inlet Bulkhead Connector

51-4 Cabinet Gas Outlet Bulkhead Connector

52 Side Access Door

63 Mounting groove for electrically heated silicone pad

66 Upstream capillary rectifier element

67 Upstream differential pressure measuring hole connector

70 Downstream differential pressure measuring port connector

71 Downstream capillary rectifier element

72 Micro Orifice Plate Restriction Elements

73 Mounting hole for temperature measurement tee thermocouple of differential pressure conversion module

74 Differential pressure conversion module temperature measurement tee

75 Differential pressure conversion module temperature measurement three-way airflow outlet

76 Upstream capillary rectifying element fixing hole

77 Capillary laminar flow unit fixing hole

78 Downstream capillary rectifier element fixing hole

79 Gas inlet heat shield

80 Upper heat shield

81, 86 Side heat shield

82 Reserved hole for thermocouple of gas preheating module of upper heat shield

83 Reserved hole for thermocouple of differential pressure conversion module of upper heat shield

84 Fixing bolts

85 Bolt holes

Detailed ways

The present disclosure provides a gas concentration measurement device and method, which have high measurement accuracy, can be calibrated, have good repeatability, can adapt to changes in test environmental factors, can be used to analyze whether the gas concentration meets requirements, and has a wide range of applications. application prospects.

In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the present disclosure will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

In an embodiment of the present disclosure, a gas concentration measurement device is provided. With reference to FIGS. 1 to 8 , the gas concentration measurement device includes:

The preheating module is used to preheat and rectify the input gas to be tested and output the first stage gas;

a differential pressure conversion module, which is connected to the preheating module and used to generate a differential pressure change value for the first-stage gas flowing through; the differential pressure conversion module includes a capillary laminar flow unit with a plurality of capillaries;

A processing module, configured to obtain the volume concentration of the gas to be measured according to the differential pressure change value.

According to an embodiment of the present disclosure, the gas concentration measurement device includes: a housing, a gas inlet, a gas preheating module, a differential pressure conversion module, a gas outlet, a differential pressure sensor, a temperature control element and an electrical interface, and the gas inlet and gas outlet are installed On the casing, the gas inlet, the gas preheating module connection, the differential pressure conversion module and the gas outlet are connected in sequence through the gas pipeline elements. The differential pressure sensor is installed on the differential pressure conversion module and fixed on the casing. The temperature control element Installed inside the casing, the electrical interface is connected with the differential pressure sensor and the temperature control element, and is fixed on the casing, wherein: the casing is used to fix the components of the sensor, and is used to protect the internal components from mechanical, The function of vibration damage and shielding electromagnetic interference; the gas inlet is used to connect the gas pipeline and provide the interface for the gas to enter the sensor; the gas outlet is used to connect the gas pipeline and provide the interface for the gas to flow out of the sensor; the gas shown in the figure The preheating module is used to preheat and rectify the inflowing measured gas; the differential pressure conversion module is used to convert the measured gas concentration into differential pressure changes; the differential pressure sensor is used to measure the differential pressure conversion module The differential pressure change value; the temperature control element is used to control the heater to work according to the set value and the measurement result of the airflow temperature, so as to achieve the effect of controlling the airflow temperature; the electrical interface is used to supply power to the gas concentration measuring device, And output the measurement results of the device. The gas to be tested flows in from the test space through the gas pipeline, and the gas to be tested flows out of the device after being sensed by the gas concentration measuring device.

According to the embodiment of the present disclosure, the gas preheating module is composed of 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, and the gas inlet end of the gas preheating module is connected to The gas inlet is connected, the gas outlet end of the gas preheating module is connected to the differential pressure conversion module, the gas inlet end of the gas preheating module and the gas outlet end of the gas preheating module are connected through a gas flow channel, and the temperature control unit and the heating element are installed in the On the gas flow channel, wherein: the gas inlet end of the gas preheating module is used to introduce gas into the gas preheating module and realize the mechanical connection with the gas inlet; the gas outlet end of the gas preheating module is used to connect the differential pressure The conversion module, which transports the preheated gas to the differential pressure conversion module; the gas flow channel is used to rectify the gas and transfer the heat generated by the heating element into the gas to heat the gas flow; the heating The element is used to heat the gas flow channel; the temperature control unit is used to measure the gas flow problem after the gas flow channel is heated.

According to the embodiment of the present disclosure, the gas flow channel is not bent, a heat exchange structure with heat exchange and rectification functions is installed in the flow channel, and a heating component is installed outside the flow channel.

According to an embodiment of the present disclosure, the temperature control unit is installed at the downstream of the gas flow in the gas flow channel, adjacent to the gas outlet end of the gas preheating module.

According to an embodiment of the present disclosure, a differential pressure conversion module includes a capillary laminar flow unit, a current limiting element, a differential pressure measurement hole, an airflow temperature measurement section, a heating element, a flow indicator, and a differential pressure conversion module housing; the gas concentration difference conversion There is a circular flow channel for gas flow in the segment shell, the circular flow channel has a gas inlet and a gas outlet, and the gas concentration difference conversion section shell is provided with two differential pressure measurement holes along the direction perpendicular to the axis of the circular flow channel. The distance between the 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 coincides with the axis of the circular flow channel in the shell of the gas concentration difference conversion section, and the capillary The flow unit is installed between the 2 differential pressure measurement holes; the heating element is installed outside the casing of the gas concentration difference conversion section, which is used to keep the temperature of the gas flowing through the capillary laminar flow unit and the restricting element substantially constant; the restricting element It is installed at the outlet of the circular flow channel of the gas concentration difference conversion section. The inlet of the restrictor element is adjacent to the side of the capillary laminar flow unit. The outlet of the restrictor element is connected to the inlet of the airflow temperature measurement section, and the inlet of the flow indicator is connected to the airflow. The outlet of the temperature measurement section, the outlet of the flow indicator is connected to the gas outlet of the gas concentration sensor, wherein: the capillary laminar flow unit is used to form a differential pressure at both ends of the capillary laminar flow unit when the gas flows; the The flow restriction element is used to maintain a constant volume flow through the gas concentration measuring device; the differential pressure measuring hole is used to measure the differential pressure before and after the capillary laminar flow unit; the airflow temperature measurement section is used to measure the flow through The temperature of the gas of the restrictor element; the heating element is used to keep the temperature of the gas flowing through the capillary laminar flow unit and the restrictor element substantially constant; the flow indicator is used to display the state of the gas flowing through the differential pressure conversion module ; The differential pressure conversion module housing is used for installing the capillary laminar flow unit, the current limiting element and the heating element, and for opening the differential pressure measurement hole.

According to the embodiment of the present disclosure, the lengths of the pressure measuring pipelines connected to the two differential pressure measurement holes on the differential pressure conversion module should be equal, and the pressure measuring pipelines should be made of materials with weak thermal conductivity.

According to the embodiment of the present disclosure, the gas flow channel of the gas preheating module, the capillary laminar flow unit in the differential pressure conversion module, the flow restricting element, and the axis of the gas flow channel in the gas flow temperature measurement section are preferably located on the same straight line. The gas flow through the cross section is circular.

According to the embodiment of the present disclosure, the outer wall of the capillary laminar flow unit is fitted with the inner wall of the circular flow channel in the casing of the gas concentration difference conversion section during assembly.

According to an embodiment of the present disclosure, the capillary laminar flow unit is characterized in that it is composed of a circular tubular outer wall and a circular capillary, a plurality of circular capillaries are arranged in the cylindrical outer wall, and the circular tubular outer wall is used for fixing the circular capillary, The flow channel of the multiple capillaries becomes the main channel of the air flow, forming a laminar flow structure, the gap between the capillary tubes, and the gap between the capillary tube and the sleeve are blocked by the adhesive, and the air flow rarely flows. The effective flow area of the gas pipeline before entering the differential pressure conversion module is the same or approximately the same as the effective flow area of the capillary laminar flow unit.

According to an embodiment of the present disclosure, the current limiting element is characterized in that a micro-precision orifice plate structure is used to maintain a constant gas volume flow.

According to an embodiment of the present disclosure, the gas concentration measuring device is characterized in that the ratio of the absolute pressure of the gas outlet to the gas inlet is not higher than 0.528.

As shown in Figure 2, the gas concentration measuring device consists of a shell base 1, a shell upper cover 2, a gas inlet and outlet panel 3, a gas inlet straight connector 4, a gas pipeline 5 of a gas preheating module, and a heating clamp block 6 of the gas preheating module , gas preheating module electric heating unit 7, gas preheating module straight-through joint 8, gas preheating module gas low thermal conductivity hose 9, gas preheating module temperature measuring tee joint 10, gas preheating module thermocouple 11, differential pressure Conversion module housing 12, differential pressure conversion module electric heating unit 14, current limiting element 15, differential pressure measuring hole connector 16, upstream differential pressure measuring hose 17, downstream differential pressure measuring hose 18, differential pressure sensor 90 degree elbow 19. Differential pressure sensor installation clip 20, low thermal conductivity hose 21, differential pressure conversion module temperature measuring tee 22, differential pressure conversion module thermocouple 23, differential pressure conversion module gas pipeline 24, flowmeter connector 25, flowmeter 26 , flowmeter installation clip 27, front panel 28, flowmeter to gas outlet connection hose 29, gas outlet panel installation straight connector 30, three-hole current signal aviation plug 31, two-hole power supply aviation plug 32, electrical rear panel 33, solid state The relay 34 , the power supply terminal 35 , the rocker switch 36 , the preheating module temperature controller 37 , the differential pressure conversion module temperature controller 38 and the differential pressure sensor 39 are composed.

3 and 4, the capillary laminar flow unit 13 is installed inside the differential pressure conversion module housing 12, and the positional relationship between the differential pressure conversion module housing 12, the capillary laminar flow unit 13 and the current limiting element 15 is given .

The casing base 1 and the casing upper cover 2 constitute the casing of the gas concentration measuring device, which is used to install and fix the parts of the gas concentration measuring device and protect the parts from being damaged by impact. The casing base 1 and the casing upper cover 2 are made of aluminum material, which has lower cost and better anti-electromagnetic interference characteristics. The shell base 1 and the shell upper cover 2 can also be made of other lighter materials. The casing upper cover 2 is fixed on the casing base 1 by screws.

The gas inlet and outlet panel 3 is fixed on the housing base 1 by screws, and the gas inlet panel is made of stainless steel.

The gas inlet straight joint 4 and the gas pipeline 5 of the gas preheating module are connected by a stainless steel ferrule. In order to improve the rectification and preheating of the gas flowing through the gas pipeline 5 of the gas preheating module, a certain number of stainless steel capillary pipelines are fixed in the gas pipeline 5 of the gas preheating module. Too thin capillary pipe diameter will cause too high flow resistance. The choice of capillary pipe diameter and length should be designed in consideration of gas flow rate 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 ferrule.

Two pieces of gas preheating module heating clamps 6 clamp the gas pipeline 5 of the gas preheating module through the semi-circular groove in the middle of the inner side, and clamp the gas pipeline 5 of the gas preheating module through bolts. The gap between the heating clamp 6 and the gas pipeline 5 of the gas preheating module is filled with thermal conductive silicone grease. In order to prevent the components from shaking, the heating clamp block 6 of the gas preheating module is fixed on the housing base 1 by screws.

The electric heating unit 7 of the gas preheating module is installed on the outside of the two pieces of gas preheating module heating clamps 6 . A preferred installation method is to paste the electric heating unit 7 of the gas preheating module on the outside of the heating clamp block 6 of the gas preheating module through heat-resistant glue. The electric heating unit 7 of the gas preheating module is covered with insulating material to prevent the heat from spreading to the outside. The electric heating unit 7 of the gas preheating module is preferably a product below 24V to improve the safety of the gas concentration measuring device.

The gas preheating module straight joint 8 is connected to the gas preheating module temperature measuring tee joint 10 through a low thermal conductivity hose 21, and the connection between them is a ferrule. The low thermal conductivity hose 21 is not only used to provide a gas flow path, but also to reduce the heat transfer between the gas pipeline 5 of the gas preheating module and the heating clamp block 6 of the gas preheating module to the temperature measuring tee joint 10 of the gas preheating module, and the The way of hose connection can reduce the inconvenience of installation caused by machining tolerance.

One end of the temperature measuring tee joint 10 of the gas preheating module perpendicular to the gas flow direction is used to install the thermocouple 11 of the gas preheating module. The thermocouple 11 of the gas preheating module is used to measure the temperature of the gas flow passing through the temperature measuring tee joint of the gas preheating module. The thermocouple 11 of the gas preheating module, the temperature controller 37 of the preheating module, the electric heating unit 7 of the gas preheating module, the solid state relay 34, the power supply terminal 35 and the lines connecting them form a temperature control loop, which controls and regulates the gas flowing through it. Airflow temperature at the preheating module temperature measurement tee joint.

In order to reduce the volume, the gas preheating module temperature measuring tee joint 10 and the air flow inlet 12-1 of the differential pressure conversion module housing 12 are connected by screws as shown in FIG. 4 . The capillary laminar flow unit 13 is installed in the flow channel of the differential pressure conversion module housing 12, and the airflow outlet 12-2 of the differential pressure conversion module housing 12 is connected to the restrictor element 15 through threads, as shown in FIG. 3, the differential pressure conversion module housing The differential pressure conversion module electric heating unit 14 is installed on the outer wall of the differential pressure conversion module. The upstream differential pressure measurement hole 12-3 and the downstream differential pressure measurement hole 12-4 of the differential pressure conversion module housing 12 are connected with two differential pressure measurement hole joints 16 by screws.

The two differential pressure measuring hole joints 16 are respectively connected to the upstream differential pressure measuring hose 17 and the downstream differential pressure measuring hose 18 through the ferrule. 2 differential pressure measuring holes of the pressure sensor 39. The upstream differential pressure measuring hose 17 and the downstream differential pressure measuring hose 18 have the same length, preferably hoses with poor thermal conductivity. The differential pressure sensor 39 is fixed on the housing base 1 by the differential pressure sensor mounting clip 20 .

The current limiting element 15 is connected to the temperature measuring tee 22 of the differential pressure conversion module through a low thermal conductivity hose 21 , and both ends of the low thermal conductivity hose 21 are connected by ferrules. The hose 21 is not only used to provide a gas flow path, but also used to reduce the heat transfer from the differential pressure conversion module housing 12 to the differential pressure conversion module temperature measuring tee 22, and to reduce the installation caused by processing tolerances through the hose connection inconvenient.

One end of the temperature measuring tee 22 of the differential pressure conversion module perpendicular to the gas flow direction is used to install the thermocouple 23 of the differential pressure conversion module. The thermocouple 23 of the differential pressure conversion module is used to measure the temperature of the airflow flowing 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 connecting them form a temperature control loop, which controls and regulates the flow through The differential pressure conversion module measures the airflow temperature at the temperature tee 22.

The air flow outlet end of the temperature measuring tee 22 of the differential pressure conversion module is connected to the gas pipeline 24 of the differential pressure conversion module, and the pipeline 24 is connected to the gas inlet section of the flowmeter 26 through a flowmeter joint 25 . Flowmeter 26 is secured to front panel 28 by flowmeter mounting clips 27 . The front panel 28 is fixed on the housing base 1 by screws. The gas outlet end of the flow meter 26 is connected to the gas outlet connecting hose 29 through another flow meter connector 25 . The other end of the hose 29 is connected to the gas outlet panel mounted straight fitting 30 . So far, the gas inlet straight joint 4 and the gas outlet panel-mounted straight joint 30 form a gas flow path through many elements. When the gas flows through this path, the gas volume concentration is converted into a differential pressure signal.

The rocker switch 36 , the preheating module temperature controller 37 , and the differential pressure conversion module temperature controller 38 are all fixed on the front panel 28 . The flow meter 26, the boat switch 36, the temperature controller 37 of the preheating module, and the temperature controller 38 of the differential pressure conversion module are all installed on one side panel to facilitate user operation.

The three-hole current signal aviation plug 31 and the two-hole power supply aviation plug 32 are mounted on the electrical rear panel 33 by screws, and the electrical rear panel 33 is mounted on the housing base 1 by screws. The three-hole current signal aviation plug is used to transmit the current signal generated by the differential pressure sensor. The two-hole power supply aviation plug 32 is used for power supply and is connected with the power supply terminal 35 and the rocker switch 36 . The rocker switch 36 can control the switching of the electrical part of the entire gas concentration measuring device.

In this embodiment, as shown in FIGS. 5 and 6 , the capillary 13-1 is fixed by the sleeve (including the first sleeve 13-2 and the second sleeve 13-3), so that any capillary will not Move with possible airflow. 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 present disclosure, the kinematic viscosity of the gas to be tested is μ, the density of the gas to be tested is ρ, the number of capillaries is n, the Reynolds number is Re, and Q _V is the flow rate; the inner diameter of a single capillary is d and the _LFE expression is :

由于工艺限制，d_LFE在工程中选择的范围一般为0.2mm至1mm；为了降低测量值的波动程度，Re的取值小于800；通过以上公式与参数确定毛细管的数量n和毛细管的内径d_LFE，即可确定毛细层流单元的截面结构，进而可以通过实验测量在流量QV下单位长度的差压值换算系数K₀，毛细层流单元的长度为L，则毛细层流单元产生的差压为ΔP＝K₀L，根据测量差压选用的传感器的有效量程，可以确定ΔP的值，进而根据L＝ΔP/K₀确定毛细层流单元的长度。

Due to process limitations, d _LFE is generally selected in the range of 0.2mm to 1mm in the project; in order to reduce the fluctuation of the measured value, the value of Re is less than 800; the number n of capillaries and the inner diameter of capillaries d _LFE are determined by the above formulas and parameters , the cross-sectional structure of the capillary laminar flow unit can be determined, and then the conversion coefficient K ₀ of the differential pressure value per unit length under the flow rate QV can be measured experimentally. The length of the capillary laminar flow unit is L, then the differential pressure generated by the capillary laminar flow unit For ΔP=K ₀ L, the value of ΔP can be determined according to the effective range of the sensor selected for measuring differential pressure, and then the length of the capillary laminar flow unit can be determined according to L=ΔP/K ₀ .

The number of the capillaries is 139, the inner diameter is 0.4mm, the wall thickness is 0.1mm, and the length is 70mm. The flow area of all capillaries is about 17.5mm ² , and the flow area of the front-end air inlet pipeline is about 16.4mm ² , and the two are similar. .

If the capillary tube 13-1 cannot be completely fixed by the mechanical force between the parts, a high temperature-resistant (such as temperature not lower than 120°C) adhesive can be coated on the outer wall of the capillary and the inner wall of the sleeve. The gas being tested reacts. Figure 6 shows a schematic diagram of the capillary laminar flow unit after assembly, and the end face of the capillary tube bundle is as flush as possible with the end face of the sleeve.

Further, in the embodiment of the present disclosure, part of the control board may also be installed in the gas concentration measuring device. The control board inside the gas concentration measuring device can convert the differential pressure signal into a concentration signal, and transmit it to the upper computer control software in the form of a digital signal. A small display screen is installed on the housing, and the concentration value can be displayed on the gas concentration measuring device. The control board can also control the heating element to work according to the temperature value of the gas. The gas concentration measuring device described in this embodiment will have stronger data processing and display capabilities, and adopt digital signal output, which is more conducive to signal transmission, and is suitable for application scenarios in which the gas concentration measuring device is distributed and used.

Further, in the embodiment of the present disclosure, the gas preheating module and the differential pressure conversion module can be manufactured into integral parts by means of finishing, instead of discrete components, further reducing the volume of the equipment, reducing the fluctuation of the gas flow, and reducing the Assembly difficulty. For example, this 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 an embodiment of the present disclosure, as shown in FIG. 7 , the gas preheating module includes a gas inlet straight-through joint 61, a gas preheating module gas pipeline 64, a gas preheating module temperature measuring tee joint 65; a gas preheating module heating clamp block 62 is installed outside the gas line 64 of the gas preheating module, and heats the fluid in the gas line. In order to improve the heating effect, a mounting groove 63 for the electric heating silicone pad of the gas preheating module heating clamp is processed on the surface of the gas preheating module heating clamp.

The differential pressure conversion module includes a differential pressure conversion module housing 69, a micro-orifice plate current limiting element 72 and a differential pressure conversion module temperature measuring tee 74, which are sequentially connected by a ferrule and a thread; the upstream differential pressure measuring hole joint 67 and the downstream differential pressure The measuring hole connector 70 is mounted on the upper part of the differential pressure conversion module housing 69 by means of threads. The upstream capillary rectifying element 66 , the capillary laminar flow unit 68 and the downstream capillary rectifying element 71 are installed in the gas flow channel in the middle of the differential pressure conversion module housing 69 along the gas flow direction. The projected positions of the pressure measuring holes on the gas flow channel are located between 66 and 68, 68 and 71, respectively.

The function of the added upstream capillary rectifying element 66 is to rectify the flowing gas, reducing the fluctuation of the measured pressure at 67 . When the air flows through the micro-orifice plate flow restricting element 72, since the size of the orifice plate suddenly becomes smaller than the cross-sectional area of the upstream airflow channel, pressure fluctuations will be generated at the pressure measuring holes upstream of the micro-orifice plate flow restricting element 72, and the downstream capillary rectification The function of element 71 is to reduce such pressure fluctuations, thereby increasing the measurement accuracy.

In the embodiment of the present disclosure, the length of the upstream capillary rectifying element 66 and the downstream differential pressure measuring hole joint 70 is 15 mm. Each is composed of 139 capillaries with an inner diameter of 0.4mm, a wall thickness of 0.1mm and a length of 15mm. The outside of the capillary is installed with a casing with an outer diameter of 10mm and a wall thickness of 1mm. The length of the casing is also 15mm. The end face of the casing is connected to the inner capillary. the end faces are flush.

The capillary laminar flow unit 68 is composed of 139 capillaries with an inner diameter of 0.4 mm, a wall thickness of 0.1 mm and a length of 70 mm, and two externally installed casings with an outer diameter of 10 mm and a wall thickness of 1 mm, and a length of 35 mm. Seal the gaps between the capillaries and secure the capillaries against movement within the cannula. The capillary effective flow area of the capillary laminar flow unit 68, the upstream capillary rectifying element 66 and the downstream capillary rectifying element 71 is 17.5mm ² , and the flow area of the air inlet pipeline at the temperature measuring tee joint of the front-end gas preheating module (16.4mm ² ) close, which is beneficial to reduce the pressure fluctuation caused by the gas flow.

In order to improve the measurement accuracy and improve the usability, the absolute pressure in the gas flow channel is measured at the position of the pressure measuring hole upstream of the differential pressure conversion module. In this embodiment, an absolute pressure gauge is added at the upstream differential pressure measuring hole joint 67 to monitor the absolute pressure value in the gas flow channel. The absolute pressure value can be used to correct the relationship between differential pressure and concentration. A typical application scenario is during the flight test of the concentration of fire extinguishing agent in the engine compartment of an aircraft, the pressure value at the measurement point will change, which is different from the ambient pressure when the ground sensor is calibrated. At this time, it can be corrected by the absolute pressure value in the flow channel. Differential pressure and concentration relationship.

Another function of the absolute pressure value is to judge the validity of the measured data and make corrections. A typical application scenario is that when the fire extinguishing agent in the measured space is sprayed suddenly, the pressure at the measurement point will rise. The pressure at the pressure measuring hole joint 71 has not yet risen, thereby causing an error. At this time, if the absolute pressure meter detects a sudden change or abnormal increase in pressure, the algorithm can judge that the differential pressure value at this moment is abnormal, and then correct it, for example, subtract the absolute pressure increase in the differential pressure conversion. difference.

In the embodiment of the present disclosure, as shown in FIG. 8 , the assembly of a plurality of heat insulation panels is added to the outside of the structure of the gas preheating module and the differential pressure conversion module. The assembly of the heat insulation panels can effectively reduce electrical heating. The heat dissipation of the components reduces the influence of the environment on the measurement, and can protect the gas preheating module and differential pressure conversion module from damage caused by mechanical force and vibration.

Further, in the embodiment of the present disclosure, the size of the gas concentration measuring device can be further reduced by means of a micro-electromechanical method, the differential pressure gas concentration measuring device is installed on the circuit board, and the gas preheating module and the differential pressure conversion module are connected to each other. The projected area does not exceed the area of the circuit board, and is fixed on the circuit board and the casing. The circuit board is provided with a temperature measurement and temperature control circuit to realize the temperature control of the gas in the gas preheating module and the differential pressure conversion module. The volume of the gas concentration measuring device can be controlled to be no more than 10cm long, 5cm high and 4cm wide. This embodiment can be applied in applications with strict size requirements, such as real-time monitoring of a certain gas concentration in equipment.

The present disclosure also provides a system for gas concentration measurement, as shown in FIG. 9 , FIG. 10 , and FIG. 14 , the gas concentration measurement system is composed of a gas concentration measurement device and a control device. The gas concentration measurement device and the control device Connected by signal transmission lines and electrical lines, where:

The system for gas concentration measurement, comprising at least one gas concentration measurement device for converting the gas concentration into an electrical signal;

The control device is used for communicating and supplying power with the gas concentration measuring device, and converting the electrical signal generated by the gas concentration measuring device into a concentration value.

According to an embodiment of the present disclosure, as shown in FIG. 11 , the control device is operable to determine an empirical relationship between the gas volume concentration and the differential pressure value for the gas to be measured. The relationship between the gas volume concentration and the differential pressure value is described by a quadratic exponential decay curve.

The measurement device and the control device are connected by electrical lines, the measurement device transmits the measurement signal to the control device, the control device processes and converts the measurement signal into a concentration signal, and outputs it through the I/O device, and the control device supplies power to the measurement device to control the measurement device working status.

As shown in FIG. 9 and FIG. 10 , eight gas concentration measuring devices 40 are installed in the cabinet through the gas concentration measuring device fixing sub-box 41 . A fixed slot for the gas concentration measuring device 40 is reserved on the gas concentration measuring device fixed sub-box 41, and a space for air circulation is reserved between the slots, and the gap can be used for ventilation airflow to flow through to prevent the gas concentration measuring device 40 from emitting The emitted heat interferes with other gas concentration measuring devices 40 .

A cooling and ventilation device sub-box 42 is installed on the fixed sub-box of the gas concentration measurement device, and the cooling and ventilation device sub-box 42 generates an air flow blown into the fixed sub-box 41 of the gas concentration measurement device to prevent temperature interference between the gas concentration measurement devices 40.

A keyboard/mouse tray 43 is installed on the upper part of the cooling ventilator box 42 . The upper part of the keyboard/mouse tray 43 is mounted with a control device slot 44 . A control device is installed inside the control device sub-box 44 .

A display 45 is attached to the upper part of the control device sub-box 44 , and a power supply sub-box 46 is attached to the upper part of the display 45 . The power supply sub-box 46 is used to safely supply power to various electrical equipment in the cabinet.

The reserved space 48 of the cabinet is located at the lower part of the fixed sub-box 41 of the gas concentration measuring device. In this embodiment, the reserved space 48 of the cabinet can be used to install another fixed sub-box 41 of the gas concentration measuring device, so that the number of the gas concentration measuring device can be expanded to 16 pieces. In some applications, the reserved space 48 in the cabinet is used to install printers and maintenance toolboxes to improve the usability of the system.

There are two side access doors 52 on both sides of the cabinet 47, and a rear access door 50 at the rear of the cabinet 47. An interface panel 51 is installed on the rear access door 50, and the interface panel 51 is provided with a power output installation hole 51- 1. Power input connector mounting hole 51-2, 8 cabinet gas inlet through-board joints 51-3, 8 cabinet gas outlet through-board joints 51-4, the joints are respectively connected to the gas inlet on the gas concentration measuring device through pipes Straight fitting 4 and gas outlet panel mounted straight fitting 30 are connected. This connection scheme can effectively reduce the complexity of the system connection during the test and avoid damage to the gas concentration measuring device. In some applications, if there are contaminants such as dust that may enter the gas pipeline in the test space, a filter can be installed on the gas pipeline between the interface panel 51 and the gas inlet straight joint 4 to prevent pollutants from entering the gas concentration Blockage after measuring device.

The present disclosure also provides a gas concentration measurement method, as shown in FIG. 12 , the gas concentration measurement method includes:

Operation S1: preheating the gas concentration measuring device;

Operation S2: Input the gas to be measured in the space into the preheated gas concentration measuring device, and record the differential pressure value; and

Operation S3: Determine the concentration of the gas to be measured according to the differential pressure value and the empirical relationship between the volume concentration of the gas to be measured and the differential pressure value.

According to an embodiment of the present disclosure, the operation S1 includes:

Operation S11: Pass the gas to be measured with a concentration of 0 or a known concentration into the gas concentration measuring device; and:

Operation S12: Heating is performed by the electric heating unit of the preheating module and the electric heating unit of the differential pressure conversion module, so that the temperature values measured by the thermocouple of the preheating module and the thermocouple of the differential pressure conversion module are stable and the same, and the preheating process is completed.

According to an embodiment of the present disclosure, more specifically, as shown in FIG. 13 , the gas concentration measurement method may include:

Step 101: use a gas pipeline to connect the test point in the test space and the gas concentration measuring device;

Step 102: Check whether the state of the gas flowing through the gas concentration measuring device is normal;

Step 103: the gas concentration measuring device is preheated to the set temperature, and the output signal of the measuring device is checked;

Step 104: Calibrate the gas concentration measuring device with the target gas of known concentration;

Step 105: carry out the test and record the data;

Step 106: the test is completed, the gas concentration measurement device is cooled, and the residual gas in the measurement device is purged;

In step 101, connect and check the gas pipeline. According to the test site conditions, use gas pipelines of the same length and specifications to connect the test points in the test space with the gas inlet interface of the corresponding gas concentration measuring device on the cabinet, and check the gas inlet connector of the corresponding gas concentration measuring device on the cabinet and the gas concentration measurement Whether the gas inlet straight fitting 4 of the device is connected correctly. Use gas pipelines of the same length and specifications to connect the gas cabinet gas outlet connector on the cabinet to the vacuum pump, and check whether the gas outlet connector of the corresponding gas concentration measurement device on the cabinet and the gas outlet panel installation straight connector 30 of the gas concentration measurement device on the cabinet are correctly connected.

In the step 102, the gas flow state is checked. Turn on the vacuum pump, and check whether the gas flow state of each gas concentration measuring device is normal through the vacuum gauge on the vacuum pump and the flow meter 26 on the gas concentration measuring device, and whether there is air leakage or blockage. Repair if there is a problem. Go to the next step after confirming that there is no problem.

In the step 103, the gas concentration measuring device is preheated, and the output signal of the gas concentration measuring device is checked. When the gas flows normally from the gas concentration measuring device, the control device is turned on, the output signal of the gas concentration measuring device is collected, and the heating of each gas concentration measuring device is started. At this time, the gas entering the gas concentration measuring device should be when the target gas concentration to be measured is 0 or a stable known concentration. When the temperature values measured by the thermocouples of the gas preheating module and the thermocouple of the differential pressure conversion module of each gas concentration measuring device are stable and the same, the preheating of the gas concentration measuring device is completed. At this time, check whether the output signal of the gas concentration measuring device collected by the control device is stable. When the signal of the gas concentration measuring device is stable, go to the next step.

In the step 104, the relationship between the differential pressure and the concentration of the gas concentration measuring device is calibrated. Place the target gas of known concentration at the test point in the test space, the gas will be sucked into the gas pipeline, and then flow into the gas concentration measuring device. Target gases of known concentrations can be stored in gas sampling bags or tanks. It should be specially pointed out that the process and environmental conditions of the known concentration of target gas entering the gas pipeline should be similar to the test environment as much as possible, or the influence of different test environments should be avoided through reasonable design, which can improve the accuracy of calibration. When the target gas of known concentration flows through the gas concentration measuring device, the output signal of the gas concentration measuring device will change, and the change value is recorded. By repeating this process, the corresponding data points of the signal of the gas concentration measuring device and the gas concentration can be obtained, and by fitting these data points with an empirical model, the corresponding relationship between the signal of the gas concentration measuring device and the gas concentration can be obtained. In many cases, it is not necessary to calibrate all the points each time, only a few points need to be calibrated, and the corresponding relationship can be obtained by fitting a known empirical model. When the environmental conditions such as laboratory temperature and humidity are similar to the test conditions, the existing corresponding relationship can also be used, that is, this step can be skipped.

In the step 105, a test is carried out. After the test space has been prepared for the test, the test starts, and the control device records the time-varying curve of the target gas concentration at multiple measurement points.

In step 106, the test is completed and the system is shut down. After the test is completed, save the test data and turn off the heating of the gas concentration measuring device. At this time, gas is continuously fed into the gas concentration measurement device to cool the heated components in the gas concentration measurement device. When the temperature measured by the thermocouple of the gas preheating module and the thermocouple of the differential pressure conversion module of the gas concentration measurement device is reduced to an acceptable level , turn off the vacuum pump. If the target gas is toxic or corrosive, before turning off the vacuum pump, make sure that the target gas in the gas concentration measuring device and the gas pipeline has been flushed with air. Finally turn off the controls. If the test is not carried out for a long time, the gas inlet on the cabinet should be plugged after the system is turned off to prevent the entry of contaminants such as dust.

It should be understood that the above-mentioned specific embodiments are only exemplary descriptions, and the gas concentration measurement device and method of the present disclosure can be applied to the measurement of any gas concentration to be measured in a variety of spaces to be measured, for example, the test space is an engine compartment that is subject to fire System protection structure. The engine compartment is only a representative structure in a non-limiting example (a gas fire extinguishing system is installed in the engine compartment), any other test spaces, such as battery compartments of energy storage power stations, engines of air, land, and water vehicles The gas concentration measuring device and method of the present disclosure can also be applied to the compartment, battery compartment or weapon compartment, etc., which is not limited herein.

So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the accompanying drawings or the text of the description, the implementations that are not shown or described are in the form known to those of ordinary skill in the technical field, and are not described in detail. In addition, the above definitions of various elements and methods are not limited to various specific structures, shapes or manners mentioned in the embodiments, and those of ordinary skill in the art can simply modify or replace them.

Based on the above description, those skilled in the art should have a clear understanding of the gas concentration measuring device and method of the present disclosure.

In summary, the present disclosure provides a gas concentration measurement device and method, which have high measurement accuracy, can be calibrated, have good repeatability, can adapt to changes in test environmental factors, and can be used to analyze whether the gas concentration To meet the needs, it has a wide range of application prospects.

It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., only refer to the directions of the drawings, not used to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are denoted by the same or similar reference numbers. Conventional structures or constructions will be omitted when it may lead to obscuring the understanding of the present disclosure.

Moreover, the shapes and sizes of the components in the figures do not reflect the actual size and proportion, 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 known to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained from the teachings of the present disclosure. Specifically, all numbers used in the specification and claims to indicate compositional contents, reaction conditions, etc., should be understood as being modified by the word "about" in all cases. In general, the meaning expressed is meant to include a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, and a change of ±1% in some embodiments. Example ±0.5% variation.

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 ordinal numbers such as "first", "second", "third", etc. used in the description and the claims are used to modify the corresponding elements, which themselves do not mean that the elements have any ordinal numbers, nor do they Representing the order of a certain element and another element, or the order in the manufacturing method, the use of these ordinal numbers is only used to clearly distinguish an element with a certain name from another element with the same name.

Furthermore, unless the steps are specifically described or must occur sequentially, the order of the above steps is not limited to those listed above, and may be varied or rearranged according to the desired design. And the above embodiments can be mixed and matched with each other or with other embodiments based on the consideration of design and reliability, that is, the technical features in different embodiments can be freely combined to form more embodiments.

Those skilled in the art will understand that the modules in the device in the embodiment can be adaptively changed and arranged in one or more devices different from the embodiment. The modules or units or components in the embodiments may be combined into one module or unit or component, and further they may be divided into multiple sub-modules or sub-units or sub-assemblies. All features disclosed in this specification, including the accompanying claims, abstract and drawings, and any method or apparatus so disclosed, may be disclosed in any combination, unless at least some of such features and/or procedures or elements are mutually exclusive. All processes or units are combined. 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 a unit claim enumerating several means, several of these means can be embodied by one and the same item of hardware.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included within the protection 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 tube_LFEIs 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 Q_VIs 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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