CN114624307B - Gas sensor cavity based on hydrodynamics - Google Patents
Gas sensor cavity based on hydrodynamics Download PDFInfo
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- CN114624307B CN114624307B CN202011447488.4A CN202011447488A CN114624307B CN 114624307 B CN114624307 B CN 114624307B CN 202011447488 A CN202011447488 A CN 202011447488A CN 114624307 B CN114624307 B CN 114624307B
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
- G01N27/4141—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS specially adapted for gases
Abstract
The utility model provides a gas sensor cavity based on hydrodynamics, includes casing, diverging device, lower casing, go up casing, diverging device, lower casing suit in proper order and constitute the inside hollow gas sensor cavity of ladder type, the middle part of going up the casing sets up the air inlet, the lateral wall and the bottom of casing set up a plurality of ventholes respectively down, the sensor is placed to the bottom of casing down, diverging device is located the cavity of inside between last casing and the lower casing, is located lower casing upper end, goes up inside the casing, set up a plurality of grooves on the diverging device lateral wall. The chamber fully considers structural symmetry, realizes uniform speed of the sensor array surface through exquisite design, ensures uniform concentration distribution of the sensor surface, simultaneously maximally reduces gas dead zones, and solves the response problem of the sensor.
Description
Technical Field
The invention belongs to the technical field of gas sensors, and particularly relates to a gas sensor chamber based on fluid mechanics.
Background
Chemical gas sensors can mimic human olfaction to effect detection and resolution of gases, and performance parameters characterizing such gas sensors include response time, response size, sensitivity, recovery time, and the like. There are many means to improve these properties, such as nanomaterials, doping, reducing chamber volume, etc. Along with the development of bionics, more and more focuses are focused on the design of an electronic nose, and compared with a traditional chemical gas sensor, the electronic nose has smaller volume, stronger analysis capability and better performance. Modifications to the electronic nose include optimizing sensor arrays, pattern recognition algorithms, signal preprocessing procedures, chamber structure optimization, and the like. At present, aiming at the structural optimization of an electronic nasal cavity chamber, research results exist, for example, chang Zhiyong et al simulate turbinates in the nasal cavity of a person by adopting axisymmetric multi-stage partition plates to split test gas, and the sensitivity of a sensor is improved. See: chang Z, sun Y, zhang Y, et al Bionic optimization design of electronic nose chamber for oil and gasdetection [ J ]. Journal of Bionic Engineering, 2018, 15 (3): 533-544 Annano et al designed a U-shaped small volume chamber, shortening the response time and recovery time of a Graphene Field Effect Transistor (GFET) sensor to water vapor, and improving the sensitivity of the sensor. See: annano F E, bouchet G, perrier P, et al Hydrodynamic evaluation of gas testing chamber: formulation, experiment [ J ]. Sensors and Actuators B: chemical, 2019, 290: 598-606. Thus, the gas sensor chamber structure has a significant impact on the test performance of the sensor, which affects the flow field distribution of the gas therein, while changes in the flow field affect the distribution of the gas concentration field. Reasonable gas sensor chambers should ensure uniform flow fields and concentration fields on the surface of the sensor array, and large-volume chambers generally form a large amount of dead zones in the chambers, so that the response of the sensor to test gas is slow, the recovery time of the response is prolonged, the performance of the sensor is extremely unfavorable, and the dead zones can prolong the response time and the recovery time, so that the miniaturized chamber is more advantageous. Currently, computational Fluid Dynamics (CFD) has become a powerful tool for optimizing gas sensor chambers.
Disclosure of Invention
The invention aims to solve the technical problem of providing a gas sensor chamber based on hydrodynamics aiming at the defects in the prior art, realizes uniform speed of the sensor array surface through exquisite design so as to ensure uniform concentration distribution of the sensor surface, simultaneously maximally reduces gas dead zone, and solves the response problem of a sensor.
The following technical scheme is adopted to solve the technical problems of the invention.
The utility model provides a gas sensor cavity based on hydrodynamics, includes casing, diverging device, lower casing, go up casing, diverging device, lower casing suit in proper order and constitute the inside hollow gas sensor cavity of ladder type, the middle part of going up the casing sets up the air inlet, the lateral wall and the bottom of casing set up a plurality of ventholes respectively down, the sensor is placed to the bottom of casing down, diverging device is located the cavity of inside between last casing and the lower casing, is located lower casing upper end, goes up inside the casing, set up a plurality of open slots on the diverging device lateral wall.
The side wall of the lower shell is provided with a plurality of air outlet holes I, the bottom of the lower shell is provided with a plurality of air outlet holes II, the air outlet holes II are arranged in a hexagonal honeycomb shape, and the sensor is located at the center of the hexagon.
The bottom of lower casing comprises lower casing I and lower casing II, the bottom of lower casing II sets up venthole II, the intermediate position installation diverging device of lower casing I.
The total height of the cavity inner cavity of the gas sensor cavity is 16mm, the bottom radius is 42mm, the inlet diameter is 16mm, and the minimum wall thickness is 3mm.
The radius of the flow dividing device is 30mm, and the height of the flow dividing device is 7mm.
The side wall of the lower shell is uniformly provided with 12 circular air outlet holes I communicated with the cavity, and the diameter of each air outlet hole I is 6mm.
The side wall of the flow dividing device is provided with 12 open grooves, the width of each open groove is 4mm, and the height of each open groove is 4mm.
The diameter of the air outlet hole II is 4mm, and the distance between the circle centers of two adjacent air outlet holes II is 5mm.
The number of sensors that the lower housing can house is 18.
The chamber of the present invention fully considers structural symmetry, which is beneficial for the response of the sensor. The gas substance concentration on the surface of each group of sensor array is very uniform through exquisite design, so that the uniform distribution of the concentration on the surface of the sensor is ensured, meanwhile, the dead zone of the gas is reduced maximally, the response problem of the sensor is solved, and the chamber is used in a gas sensor testing system and is used for improving the testing performance of a gas sensor. The chamber of the invention has very small volume and small dead volume of gas, can be used for placing a plurality of sensors to form an array, and can be used as the chamber of the electronic nose.
The height of the chamber is only 2cm, and the radius of the bottom end of the chamber is 4.5cm. The low-height design can shorten the time for the test gas to reach the sensor and accelerate the response of the sensor; while a large bottom surface is capable of receiving a greater number of sensors. Based on this low height, large cross-section design, a flow divider is installed inside the chamber in order to ensure even dispersion of the incoming gas. Therefore, the chamber not only ensures that the gas can reach the sensor surface quickly because of the low-height chamber, but also can be uniformly dispersed on the sensor surface because of the flow dividing device, and simultaneously, a large number of sensors can be placed. The bottom air outlets of the chambers are arranged in a hexagonal mode, and each sensor is surrounded by surrounding air outlets, so that the uniformity of a flow field above the sensor can be enhanced, and the gas can be rapidly discharged after the gas and the sensor are fully acted and are desorbed. The arrangement of the openings in the side walls of the chamber is also symmetrical, mainly to ensure the gas evacuation around the outer sensor. The design of the air outlet ensures the symmetry and uniformity of the flow field, reduces dead zones and accelerates the discharge of air. The flow dividing device of the chamber consists of an open slot of the side wall and a round hole at the bottom, and the open slot of the side wall corresponds to the position of the air outlet of the side wall of the chamber. The round hole at the bottom corresponds to the position of the sensor. This design ensures uniform and symmetrical flow splitting.
Drawings
FIG. 1 is a schematic view of the external structure of a chamber according to the present invention;
FIG. 2 is a schematic view of the internal structure of the chamber of the present invention;
FIG. 3 is a front view of the chamber without the flow splitting device of the present invention;
FIG. 4 is a schematic view showing the distribution of the air outlet holes at the bottom of the lower shell of the present invention;
FIG. 5 is a schematic view of the vent holes in the side wall of the lower housing of the present invention;
FIG. 6 is a schematic cross-sectional view of a shunt device of the present invention;
FIG. 7 is a side view of the shunt device of the present invention;
FIG. 8 is a schematic diagram of a sensor position distribution according to the present invention;
FIG. 9 is a velocity profile of a YZ section of the chamber of the present invention;
FIG. 10 is a velocity profile of a chamber XZ cross section of the present invention;
FIG. 11 is a graph showing the velocity profile of a sensor surface in accordance with the present invention
FIG. 12 is a graph of the YZ profile concentration profile of the chamber of the present invention;
FIG. 13 is a graph of the concentration profile of a chamber XZ in accordance with the present invention;
FIG. 14 is a graph showing the concentration profile of a sensor surface according to the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The gas sensor chamber based on hydrodynamics, as shown in fig. 1, 2, 4 and 5, comprises an upper shell 1, a flow dividing device 2 and a lower shell 6, as shown in fig. 3, wherein the upper shell 1, the flow dividing device 2 and the lower shell 6 are sequentially sleeved to form a stepped gas sensor chamber with a hollow inside, the middle part of the upper shell 1 is provided with an air inlet 5, the diameter of the air inlet 5 is 16mm, the total height of the chamber inner cavity of the gas sensor chamber is 16mm, the bottom radius is 42mm, and the minimum wall thickness is 3mm. The bottom of lower casing 6 comprises lower casing I3 and lower casing II 4, and open the bottom of lower casing II 4 has a plurality of ventholes II 8, and the diameter of venthole II 8 is 4mm, and as shown in FIG. 6, the distance between two adjacent ventholes II 8 is 5mm, and venthole II 8 is hexagonal and is the cellular setting, and the sensor is located the hexagon center, as shown in FIG. 8, two sets of sensors can be arranged to lower casing 6 bottom, and wherein inlayer 6 is a set of, and outer 12 is a set of, and the number that can place the sensor is 18. Each sensor has a side length of 10mm and a height of 5mm. Two binding posts are arranged near each sensor, and the diameter of a preformed hole of each binding post is 2mm. The side wall of the lower shell 6 is uniformly provided with 12 circular air outlet holes I7 communicated with the cavity, wherein the diameter of the air outlet holes I7 is 6mm. The flow dividing device 2 is located in the cavity inside between the upper shell 1 and the lower shell 6, is located at the upper end of the lower shell 6, and is located inside the upper shell 1, as shown in fig. 7, the radius of the flow dividing device 2 is 30mm, the height is 7mm, 12 open slots 9 are formed in the side wall of the flow dividing device 2, wherein the width of each open slot 9 is 4mm, and the height is 4mm.
The principle and the working process of the invention are as follows: the chamber is arranged in a dynamic testing system of the gas sensor, a certain flow (10L/min) of gas to be tested enters from the gas inlet, is split by the splitting device, is uniformly dispersed on the surface of the sensor, and is completely discharged from the gas outlet after the surface is fully adsorbed and desorbed. The invention has the advantages of small volume of the chamber, uniform flow field on the surface of the sensor array, uniform concentration distribution and less air flow dead zone, and can well improve the testing performance of the air-sensitive sensor.
To achieve the object of the invention, the flow field and the concentration field inside the chamber are simulated by using two physical field interfaces of laminar flow and dilute mass transfer in COMSOL 5.5 software. The density of the gas in the simulation set was 1.13 kg/m 3 Dynamic viscosity of 1.78X10 -5 Pa.s, diffusion coefficient of 10 -5 m 2 And/s. The average inlet speed of the simulation setting is 0.83m/s, and the concentration flux of the inlet is 1 mol/(m) 2 S). And obtaining the speed and concentration distribution of the gas in the chamber by solving a laminar, incompressible and steady-state Navier-Stokes equation and a steady-state convection diffusion equation. . The continuity equation and momentum equation for controlling fluid flow are as follows:
wherein the method comprises the steps ofpWhere ρ is the fluid density, μ is the hydrodynamic viscosity,u i is a velocity vector.
The steady state convective diffusion equation for mass transfer is as follows:
wherein D is the diffusion coefficient and c is the substance concentration.
The simulation results are shown in fig. 9, 10, 11, 12, 13, and 14. As shown in fig. 9 and 10, the gas is split uniformly by the splitting device to the bottom sensor surface. As shown in fig. 11, the gas flow velocity distribution is the same across each set of sensor surfaces. As shown in fig. 12 and 13, as shown in fig. 14, there is a difference between the odor concentration in the center of the chamber and the odor concentration distribution around the chamber, but the concentration of the odor substance is uniformly dispersed on the surface of the sensors for each group of sensors.
Claims (7)
1. A fluid mechanics based gas sensor chamber characterized by: the gas sensor comprises an upper shell (1), a flow dividing device (2) and a lower shell (6), wherein the upper shell (1), the flow dividing device (2) and the lower shell (6) are sequentially sleeved to form a stepped hollow gas sensor cavity, an air inlet (5) is formed in the middle of the upper shell (1), a plurality of air outlets are respectively formed in the side wall and the bottom of the lower shell (6), a sensor is placed at the bottom of the lower shell (6), the flow dividing device (2) is located in a cavity inside between the upper shell (1) and the lower shell (6), the flow dividing device is located inside the upper shell (1) at the upper end of the lower shell (6), and a plurality of open slots (9) are formed in the side wall of the flow dividing device (2);
a plurality of air outlet holes I (7) are formed in the side wall of the lower shell (6), a plurality of air outlet holes II (8) are formed in the bottom of the lower shell (6), the air outlet holes II (8) are arranged in a hexagonal honeycomb shape, and the sensor is located in the center of the hexagon; the bottom of inferior valve body (6) comprises inferior valve body I (3) and inferior valve body II (4), the bottom of inferior valve body II (4) sets up venthole II (8), diverging device (2) are installed to the middle part of inferior valve body I (3), evenly arrange 12 circular shape ventholes I (7) and cavity intercommunication on the lateral wall of inferior valve body (6), it has 12 open slot (9) to open on diverging device (2) lateral wall.
2. A fluid mechanics based gas sensor chamber according to claim 1, characterized in that: the total height of the cavity inner cavity of the gas sensor cavity is 16mm, the bottom radius is 42mm, the minimum wall thickness is 3mm, and the diameter of the gas inlet (5) is 16mm.
3. A fluid mechanics based gas sensor chamber according to claim 1 or 2, characterized in that: the radius of the flow dividing device (2) is 30mm, and the height of the flow dividing device is 7mm.
4. A fluid mechanics based gas sensor chamber according to claim 3, characterized in that: the diameter of the air outlet hole I (7) is 6mm.
5. A fluid mechanics based gas sensor chamber according to claim 1 or 4, characterized in that: the width of the open groove (9) is 4mm, and the height is 4mm.
6. A fluid mechanics based gas sensor chamber according to claim 5, wherein: the diameter of each air outlet hole II (8) is 4mm, and the distance between the circle centers of two adjacent air outlet holes II (8) is 5mm.
7. A fluid mechanics based gas sensor chamber according to claim 6, wherein: the number of sensors that can be placed in the lower housing (6) is 18.
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2020
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