CN103644947B - Gas micro-flow measuring device - Google Patents

Abstract

The invention discloses a gas micro-flow measurement device, which comprises an inlet stabilizing container, a micro-nano channel or device to be measured, a double-channel volume indicating unit, an outlet stabilizing container and an image position recording unit. The pressure in the stabilizing container passes through the The flow valve and the air supply flowmeter cooperate to carry out continuous high-resolution adjustment; then use one channel of the dual-channel volume indicating unit to establish a stable flow in the micro-nano channel or device under test with the inlet and outlet pressure-stabilizing containers; after that Switch to another channel of the preset droplet, and track the droplet movement through the image position recording unit composed of a microscope objective lens and a CCD camera, the measurement device has the advantages of high measurement accuracy and resolution and easy implementation of the exhaust device .

Description

A gas micro flow measuring device

technical field

The invention relates to a measurement device, which belongs to the field of measurement technology, in particular to a gas micro-flow measurement device, which is used for experimental measurement of gas flow in micro-nano-scale channels or components.

Background technique

At present, the manufacturing and application of MEMS has become the frontier of high-tech development. Some scales in this field have entered the category of nanotechnology. The flow of gas in micro-nano machinery can enter the slip flow area or even the transition area. Due to the influence of rarefaction and compression effects, its dynamics and thermodynamic properties are very different from those of conventional flow. Although a lot of work has been done on the micro-scale flow characteristics, the understanding of its flow mechanism is far from mature. Some studies The conclusions have not yet been unified. Therefore, it is necessary to develop a measurement device for micro-flow gas flow, no matter from the research point of view or based on the detection of micro-nano devices in the industrial field.

Theoretically, for a complete gas, the mass flow rate of the time-varying system is determined by the volume, pressure, and temperature changes. If the temperature is controlled to be approximately constant during the measurement process and its influence is ignored, the measurement of a small mass flow rate can be transformed into the measurement of a constant volume. Pressure change or volume change under constant pressure, due to the influence of air leakage and the poor accuracy and real-time performance of indirect pressure measurement under low pressure, it is difficult to measure small pressure changes, and it is also difficult to measure small volume changes under constant pressure .

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a gas micro-flow measurement device with high measurement accuracy and resolution and is easy to implement, so as to meet the needs of gas flow measurement in the field of micro-nano machinery. The present invention is based on the following technical solutions Achieved: a gas micro-flow measurement device, including an inlet pressure stabilization system 1, a measured micro-nano channel or device 2, a volume indicator unit, an outlet pressure stabilization system 4, a vacuum pumping system 13 and an image recording unit 5, wherein the inlet The voltage stabilizing system 1, the measured micro-nano channel or device 2, the volume indicating unit and the outlet stabilizing container 4 are sequentially connected in series to form a closed system, which is characterized in that: the volume indicating unit is a dual-channel volume indicating unit 3, The dual-channel volume indicator unit 3 is formed by parallel connection of two channels, one of which is connected in series with the fifth valve 21, the first calibration pipe 22 and the sixth valve 23 by a conduit, and the other channel is connected by a conduit to the sixth valve in sequence. Seven valves 27, the second calibration pipe 25 and the eighth valve 24 are connected in series, and the liquid droplet 26 is injected into the first calibration pipe 22 or the second calibration pipe 25, and the image recording unit 5 is arranged at the injection droplet 26 Before calibrating the tube, the motion of the droplet 26 is tracked.

Preferably, the inlet pressure stabilization system includes using a conduit to connect the first valve 8 and the inlet container 7 in sequence, and one port of the inlet container 7 is connected to the first throttle valve 10 and the third valve in sequence using a conduit. 12. The inlet container 7 is fixedly connected to the first pressure sensor 11 and the inlet container interface 6 respectively; the outlet pressure stabilizing system 4 includes connecting the second valve 18 and the outlet container 19 in sequence by using a conduit, and the outlet One interface of the container 7 is connected by a conduit and connected to the second throttle valve 16 and the fourth valve 14 in sequence, and the second pressure sensor 15 and the outlet container interface 20 are fixedly connected to the outlet container 19 respectively. The inlet pressure stabilization system 1 The third valve 12 and the fourth valve 14 of the outlet stabilizing system 4 are respectively connected with the vacuum pumping system 13; the first valve 8 of the inlet stabilizing system 1 and the second valve 18 of the outlet stabilizing system 4 are respectively connected The first air supply flowmeter 9 and the second air supply flowmeter 17 are adjusted by the cooperation of the first throttle valve 10 and the second throttle valve 16 with the first air supply flowmeter 9 and the second air supply flowmeter 17 internal pressure.

Further preferably, the image recording unit 5 is composed of a microscope objective lens 28 and a CCD camera 29 .

Beneficial effects of the present invention: the throttle valve and the mass flowmeter are used to adjust the pressure at both ends of the micro-nanoscale channel or device 2. Since the gas supply flowmeter has continuous high-resolution adjustment capabilities, the pressure control is more stable, which is conducive to improving Measurement accuracy; using a symmetrical dual-channel volume indicator unit, liquid droplets can be preset in one channel, reducing the impact of adding liquid droplets on the stable gas flow during measurement; while the position of the liquid drop is linear in the calculation of pressure and time The data can eliminate the influence of the conversion between channels on the measurement, which is conducive to improving the measurement accuracy; the microscope objective lens used in the image recording unit improves the resolution of the droplet position, and the real-time recording of the CCD camera makes data pickup more convenient and accurate , It is also beneficial to improve the resolution and accuracy of the measurement.

Description of drawings

Below in conjunction with accompanying drawing, technical scheme of the present invention will be further described:

Figure 1 Schematic diagram of the composition of the gas micro-flow measurement device;

Figure 2 is a schematic diagram of the composition of the inlet and outlet pressure-stabilizing vessels;

Figure 3 is a schematic diagram of the composition of the dual-channel volume display unit;

Figure 4 is a schematic diagram of the composition of the image recording unit;

In the figure: 1. Inlet pressure-stabilizing container; 2. Micro-nano channel or device; 3. Dual-channel volume indicator unit; 4. Outlet pressure-stabilizing container; 5. Image recording unit; 6. Inlet container interface; 7. Inlet container; 8 , the first valve; 9, the first air supply flow meter; 10, the first throttle valve; 11, the first pressure sensor; 12, the third valve; 13, the vacuum pumping system; 14, the fourth valve; 15, The second pressure sensor; 16, the second throttle valve; 17, the second air supply flowmeter; 18, the second valve; 19, the outlet container; 20, the outlet container interface; 21, the fifth valve; 22, the first calibration 23, the sixth valve; 24, the eighth valve; 25, the first calibration tube; 26, the liquid droplet; 27, the seventh valve; 28, the microscope objective lens; 29, the CCD camera.

detailed description

A gas micro-flow measurement device as shown in Figure 1, including an inlet stabilizing container 1, a micro-nano channel or device 2 to be tested, a dual-channel volume indicating unit 3, an outlet stabilizing system 4, a vacuum pumping system 13 and an image Recording unit 5, wherein the inlet stabilizing system 1 is measured micro-nano channel or device 2, the dual-channel volume indicating unit 3, and the outlet stabilizing container 4 are sequentially connected in series to form a closed gas flow space; as shown in Figure 2, the The inlet pressure stabilizing system 1 includes connecting the first valve 8 and the inlet container 7 sequentially with a conduit, and one interface of the inlet container 7 is connected with the first throttle valve 10, the third valve 12 and the main station in sequence through a conduit. The inlet container 7 is fixedly connected to the first pressure sensor 11 and the inlet container interface 6 respectively; the outlet pressure stabilization system 4 includes using a conduit to connect the second valve 18 and the outlet container 19 in sequence, and the outlet container 7 One interface is connected with a conduit and connected to the second throttle valve 16 and the fourth valve 14 in sequence, and the second pressure sensor 15 and the outlet container interface 20 are respectively fixedly connected to the outlet container 19, and the first valve 8 of the inlet pressure stabilization system 1 Connect the first air supply flowmeter 9 and the second air supply flowmeter 17 with the second valve 18 of the outlet stabilizing system 4, the supply air flowmeter can be continuously adjusted and has high resolution; the inlet stabilizing system The third valve 12 in 1 and the fourth valve 14 of the outlet pressure stabilization system 4 are respectively connected to the vacuum pumping system 13; as shown in Figure 3, the dual-channel volume indicating unit 3 is formed by parallel connection of two channels, wherein One channel is formed by connecting the fifth valve 21, the first calibration pipe 22 and the sixth valve 23 in series by the conduit in sequence, and the other channel is formed by connecting the seventh valve 27, the second calibration pipe 25 and the eighth valve 24 in series by the conduit in sequence , the second calibration tube 25 is injected with liquid droplets 26, the two channels of the dual-channel volume indicating unit 3 should have the same geometric size, the inner diameter should be selected according to the measurement range and should have high precision and consistency, the two channels The inlet and outlet of the system are connected in parallel through a tee. Among the two symmetrical channels, one is used to adjust the measurement system to a stable state; the other presets liquid droplets. After the system is stable, the volume change is measured by switching the valve; as shown in the figure 4, the image recording unit 5 is arranged at the corresponding position of the second calibration tube 25, and is composed of a microscopic objective lens 28 and a CCD camera. The CCD camera should select high-speed and high-pixel products, and the magnification of the microscopic objective lens should be the same as The pixels of the CCD camera are matched and selected to record and track the motion of the droplet 26 .

After the system is connected, in order to ensure the airtightness of the system, the leak detection of the connected system should be carried out. The leak rate should be less than 10 ^{- 9} Pam ³ /s; The valve 8 and the second valve 18 are always closed, the fifth valve 21, the sixth valve 23, the eighth valve 24, and the seventh valve 27 are always open. After starting the vacuum pumping system 13, open the third valve 12 and the fourth valve in sequence 14. The first throttle valve 10 and the second throttle valve 16. The ultimate vacuum of the system should reach 1×10 ^-3 Pa.

After the system reaches the ultimate vacuum, close the seventh valve 27, then open the first valve 8 and the second valve 18, fill the system with experimental gas through the gas supply flowmeter 9 and the gas supply flowmeter 17, and then adjust the gas supply Flow meter 9, air supply flow meter 17 and first throttle valve 10, the opening degree of second throttle valve 16 control the pressure in inlet stabilized pressure system 1 and outlet stabilized pressure system 4 to reach and stabilize at the experimental pressure, at this moment , the gas flows from the inlet stabilizing system 1 through the micro-nano channel or device 2 and flows into the outlet container 7 through the channel where the first calibration tube 22 is located; after reaching a stable pressure, the liquid droplet begins to be preset; at this time, the volume indication of the dual channel In the unit 3, only the seventh valve 27 is closed, and the fifth valve 21, the sixth valve 23, and the eighth valve 24 are all open. Inject liquid droplet 26 in the second calibration tube 25 by syringe, because the seventh valve 27 is closed, droplet 26 can keep static state in the second calibration tube 25; Install and calibration start in microscope objective lens 28 and CCD camera 29 Finally, close the fifth valve 21 and open the seventh valve 27 at the same time, the droplet will gradually start to move, and the CCD camera will record the moving position and time information of the droplet. The eighth valve 24 can be closed on the approach of the liquid drop to prevent it from entering the outlet container 19 .

After the measurement, data processing is carried out, and the data of the linear relationship between the position of the droplet and the time is taken, and the micro flow rate of the gas is calculated according to formula 1;

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; m</span>}\frac{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; RT</span>}}\mathrm{<span\; class="notranslate">\; A</span>}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;L</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them: Q _m ——gas flow rate, unit: Kg/s;

p——the pressure of the gas in the outlet pressure-stabilizing vessel, unit: Pa;

M - molar mass of the gas to be measured, unit: Kg/mol;

R——molar gas constant, unit: 8.31441J/mol K;

T——temperature, unit: K;

A——The cross-sectional area of the channel calibration tube of the volume indicating unit, unit: m ² ;

ΔL——The droplet movement distance converted according to the calibration standard, the magnification of the microscope objective lens and the CCD pixel, unit, m;

Δt——the time elapsed by the droplet movement ΔL distance, s;

To sum up, it can be seen that the gas micro-flow measuring device provided by the present invention has positive effects of high measurement accuracy and resolution, and the minimum mass flow rate measured by the device can reach 1×10- ¹¹ Kg/s.

The specific implementation methods in the present invention are written in a progressive manner, mainly emphasizing the differences in the various implementations, and the similar parts can be referred to each other.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and can also be made without departing from the gist of the present invention within the scope of knowledge of those of ordinary skill in the art. Variations.

Claims (2)

1. A gas micro-flow measurement device, including an inlet pressure stabilization system (1), a measured micro-nano channel or a measured micro-nano device (2), a volume indicating unit, an outlet pressure stabilization system (4), and a vacuum pumping system (13) and image recording unit (5), wherein the inlet voltage stabilization system (1), the measured micro-nano channel or the measured micro-nano device (2), the volume indicating unit and the outlet voltage stabilization system (4) are connected in series in sequence Form a closed system, characterized in that: the volume indicating unit is a double-channel volume indicating unit (3), and the double-channel volume indicating unit (3) is composed of two channels connected in parallel, one of which is connected to the second channel in turn by a catheter Five valves (21), the first calibration pipe (22) and the sixth valve (23) are connected in series, and another channel is connected to the seventh valve (27), the second calibration pipe (25) and the eighth valve ( 24) formed in series, inject liquid droplets (26) into the first calibration tube (22) or the second calibration tube (25), and the image recording unit (5) is arranged in front of the calibration tube injecting the liquid droplets (26) , record and track the movement of the droplet (26); the inlet pressure stabilization system includes a first valve (8) and an inlet container (7) connected in sequence by a conduit, and an interface of the inlet container (7) utilizes The conduit is connected to the first throttle valve (10) and the third valve (12) in sequence, and the inlet container (7) is fixedly connected to the first pressure sensor (11) and the inlet container interface (6); The outlet pressure stabilization system (4) includes a second valve (18) and an outlet container (19) that are sequentially connected by a conduit, and one port of the outlet container (19) is connected with a conduit and connected to the second throttling valve in sequence. Valve (16), the fourth valve (14), the outlet container (19) is fixedly connected with the second pressure sensor (15) and the outlet container interface (20); the third valve ( 12) and the fourth valve (14) of the outlet stabilizing system (4) are respectively connected with the vacuum pumping system (13); the first valve (8) of the inlet stabilizing system (1) is fixedly connected with the first supply Air flow meter (9); the second valve (18) of the outlet pressure stabilization system (4) is fixedly connected with the second air supply flow meter (17). 2. A gas micro-flow measurement device according to claim 1, characterized in that: said image recording unit (5) is composed of a microscope objective lens (28) and a CCD camera (29).