System and method for measuring density of mixed gas in normal temperature range

Abstract

The invention relates to a system and method for measuring the density of mixed gas in a normal temperature range. The system comprises a gas cylinder, a pressure reducing valve, a connecting pipe, a mass flow controller, a gas mixing cavity, a gas mixing vacuum valve, an inflation cavity, an inflation vacuum valve, a positive pressure meter, a full-scale vacuum gauge, a temperature sensor and a molecular pump set. The measuring system provided by the invention is high in reliability, accurate in measurement, simple in experimental process and easy to operate. The experimental principle is based on an ideal gas equation and a Dalton partial pressure law, and errors caused by gas mass and volume measurement are avoided. Meanwhile, the density of mixed gas in different proportions can be measured, and the specific requirements of a user are met. The positive pressure meter and the full-scale vacuum gauge are matched for use, so that wide-area density measurement of mixed gas in a range from negative pressure to positive pressure is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of density measurement in the measurement of thermophysical properties of mixed gases, and specifically to a density measurement system and method for mixed gases in the normal temperature range. Background Art

[0002] Density is one of the basic thermophysical parameters of gaseous working media, which directly affects the accurate calculation of fluid dynamics, thermodynamics, and mass transfer processes. The changes in its component ratio, temperature, and pressure will all lead to non-linear changes in density, thereby affecting the performance evaluation and optimization of the system. Experiments are an important way to obtain fluid thermophysical property data, and thermophysical property experiments have become a basic method for determining certain basic physical constants and establishing metrological standards.

[0003] In scenarios such as basic theoretical research, simulation, industrial product development and optimization, the mixing of multiple gases is often involved. Accurately measuring the density of mixed gases plays an important role in optimizing industrial design, ensuring experimental accuracy, and improving simulation accuracy. Summary of the Invention

[0004] Based on the above technical problems, the purpose of the present invention is to provide a measurement system for mixed gas density experiments in the normal temperature range. Based on the ideal gas equation and Dalton's law of partial pressures, by measuring the air pressure and temperature, the measurement of the density of mixed gases is realized.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A density measurement system for mixed gases in the normal temperature range, the system includes:

[0007] A first gas cylinder, a second gas cylinder, a first pressure reducing valve, a second pressure reducing valve, a first connecting pipe, a second connecting pipe, a first mass flow controller, a second mass flow controller, a gas mixing cavity, a first gas mixing vacuum valve, a second gas mixing vacuum valve, an inflation cavity, a first inflation vacuum valve, a second inflation vacuum valve, a third inflation vacuum valve, a fourth inflation vacuum valve, a positive pressure gauge, a full-range vacuum gauge, a temperature sensor, a molecular pump set;

[0008] Among them, the outlet ends of the first gas cylinder and the second gas cylinder are respectively fixed with a first pressure reducing valve and a second pressure reducing valve. The outlet ends of the first pressure reducing valve and the second pressure reducing valve are fixedly connected with a first connecting pipe and a second connecting pipe. One ends of the first connecting pipe and the second connecting pipe are respectively installed with a first mass flow controller and a second mass flow controller. One ends of the first mass flow controller and the second mass flow controller are fixedly connected with a first mixing vacuum valve and a second mixing vacuum valve. The molecular pump group is fixedly connected with a third inflation vacuum valve. The front part of the inflation cavity is fixedly connected with a temperature sensor, and both side parts are fixedly connected with a positive pressure gauge and the full-range vacuum gauge through a first inflation vacuum valve and a second inflation vacuum valve.

[0009] As a further technical solution of the present invention, a flange interface is provided on the wall surface of the inflation cavity, and the first inflation vacuum valve, the second inflation vacuum valve, the third inflation vacuum valve, and the fourth inflation vacuum valve are connected to the inflation cavity through the flange interface.

[0010] As a further technical solution of the present invention, the mixing cavity is actually a KF25 three-way joint, the two ends of which are connected to the first mixing vacuum valve and the second mixing vacuum valve, and the remaining end is connected to the fourth inflation vacuum valve.

[0011] As a further technical solution of the present invention, the temperature sensor is a PT100 thermal resistance temperature sensor, with a measuring range of -70~200°C and an accuracy of Class A 0.1%.

[0012] As a further technical solution of the present invention, the lower limit of the pressure measured by the full-range vacuum gauge is 1×10 -9 hPa, the measuring range of the positive pressure gauge is 2MPa, the accuracy is 0.2%, and the absolute pressure is measured.

[0013] As a further technical solution of the present invention, the mass flow controller has a measuring range of 0-200 SCCM, the repeatability accuracy is less than 0.2%, and it can work under a working pressure difference of 0.5~5 Mpa.

[0014] As a further technical solution of the present invention, the molecular pump group has a high pumping speed of 260 l / s and can provide a limit pressure lower than 10 -7 hPa.

[0015] As a further technical solution of the present invention, the first mixing vacuum valve, the second mixing vacuum valve, and the inflation vacuum valve are all angle valves and are all sealed through sealing rings.

[0016] Another object of the present invention is to provide a method for measuring the density of a mixed gas in the normal temperature range. The measuring method is implemented based on the above-mentioned measuring system for the density of a mixed gas in the normal temperature range, and the method includes the following steps:

[0017] Step (1): Before using the measurement system, first perform leak detection. After ensuring that the leak rate of the system meets the requirements, open the second inflation vacuum valve, the third inflation vacuum valve, and the fourth inflation vacuum valve. Open the first mixing vacuum valve and the second mixing vacuum valve. After starting the molecular pump group to evacuate the system to the background vacuum, close the third inflation vacuum valve.

[0018] Step (2): By setting the first mass flow controller and the second mass flow controller, after setting the composition ratio of the mixed gas, introduce the gas. Obtain the molar mass Mgas of the mixed gas through weighted average. First, use a full-range vacuum gauge to measure the pressure below atmospheric pressure, denoted as P1. The gas will be evenly mixed in the mixing cavity and then introduced into the inflation cavity, causing the pressure in the cavity to continuously increase.

[0019] Step (3): When the pressure value is close to atmospheric pressure (101325 Pa), close the second inflation vacuum valve, open the first inflation vacuum valve, and start using a positive pressure gauge to record the pressure P2 above atmospheric pressure. After filling to the required pressure, close the third inflation vacuum valve and the fourth inflation vacuum valve, close the first decompression valve and the second decompression valve. After the pressure value stabilizes, terminate the recording.

[0020] Step (4): During the entire inflation process, each pressure corresponds to a mixed gas density value. From the ideal gas formula:

[0021] ;

[0022] where ρ is the density of the mixed gas; P is the pressure of the mixed gas, that is, P1 or P2; R is the universal gas constant, and T is the ambient temperature (room temperature). Obtain the mixed gas density values within the entire measurement pressure range at room temperature through the ideal gas formula.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) In the present invention, based on the ideal gas equation and Dalton's law of partial pressures, by measuring the air pressure and temperature, the measurement of the density of the mixed gas is realized, thus avoiding the errors caused by the measurement of gas mass and volume.

[0025] (2) In the present invention, by adjusting the mass flow controller, the density of mixed gases with different ratios can be measured to meet the specific requirements of users.

[0026] (3) In the present invention, the molecular pump group can be used to pump out the redundant gases in the measurement system, reducing the errors caused by the purity of the working medium in the measurement system.

[0027] (4) In the present invention, the combined use of the positive pressure gauge and the full-range vacuum gauge can measure from 1×10-9 A mixed gas from hPa to 2 MPa has good accuracy throughout the entire pressure range. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of a mixed gas density measurement system in a normal temperature range.

[0029] The labels in the figure are explained as follows: 1 - positive pressure gauge, 2 - full range vacuum gauge, 3 - first inflation vacuum valve, 4 - second inflation vacuum valve, 5 - temperature sensor, 6 - inflation cavity, 7 - third inflation vacuum valve, 8 - molecular pump group, 10 - fourth inflation vacuum valve, 11 - gas mixing device, 12 - first gas mixing vacuum valve, 13 - first mass flow controller, 14 - first connecting pipe, 15 - first pressure reducing valve, 16 - first gas cylinder, 17 - second gas mixing vacuum valve, 18 - second mass flow controller, 19 - second connecting pipe, 20 - second pressure reducing valve, 21 - second gas cylinder.

[0030] Figure 2 It is a data result graph obtained from the actual system demonstration in a specific embodiment. Detailed Embodiment

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] Please refer to Figure 1 , the present invention provides a mixed gas density measurement system in a normal temperature range, and the system includes:

[0033] The first gas cylinder 16, the second gas cylinder 21, the first pressure reducing valve 15, the second pressure reducing valve 20, the first connecting pipe 14, the second connecting pipe 19, the first mass flow controller 13, the second mass flow controller 18, the gas mixing cavity 11, the first gas mixing vacuum valve 12, the second gas mixing vacuum valve 17, the inflation cavity 6, the first inflation vacuum valve 3, the second inflation vacuum valve 4, the third inflation vacuum valve 7, the fourth inflation vacuum valve 10, the positive pressure gauge 1, the full range vacuum gauge 2, the temperature sensor 5, the molecular pump group 8;

[0034] Among them, the outlet ends of the first gas cylinder 16 and the second gas cylinder 21 are respectively fixed with a first pressure reducing valve 15 and a second pressure reducing valve 20. The outlet ends of the first pressure reducing valve 15 and the second pressure reducing valve 20 are fixedly connected with a first connecting pipe 14 and a second connecting pipe 19. One ends of the first connecting pipe 14 and the second connecting pipe 19 are respectively equipped with a first mass flow controller 13 and a second mass flow controller 18. One ends of the first mass flow controller 13 and the second mass flow controller 18 are fixedly connected with a first gas mixing vacuum valve 12 and a second gas mixing vacuum valve 17. The molecular pump group 8 is fixedly connected with a third gas charging vacuum valve 7. The front part of the gas charging cavity 6 is fixedly connected with a temperature sensor 5. The two side parts are fixedly connected with a positive pressure gauge 1 and the full-range vacuum gauge 2 through a first gas charging vacuum valve 3 and a second gas charging vacuum valve 4.

[0035] In order to reduce leakage, in the present invention, it is preferably that the wall surface of the gas charging cavity 6 is provided with a flange interface, and the first vacuum valve 3, the second vacuum valve 4, the third vacuum valve 7, and the fourth vacuum valve 10 are connected to the gas charging cavity 6 through the flange interface.

[0036] In order to fully mix the gases, in the present invention, it is preferably that the gas mixing cavity 11 is actually a KF25 three-way joint, the two ends of which are connected to the first gas mixing vacuum valve 12 and the second gas mixing vacuum valve 17, and the remaining one end is connected to the fourth gas charging vacuum valve 10.

[0037] In order to accurately measure the temperature, in the present invention, it is preferably that the temperature sensor 5 is a PT100 thermal resistance temperature sensor, with a measuring range of -70~200°C and an accuracy of Class A 0.1%.

[0038] In order to broaden the measuring pressure range, in the present invention, it is preferably that the lower limit of the measuring pressure of the full-range vacuum gauge 2 is 1×10 -9 hPa, the measuring range of the positive pressure gauge 1 is 2 MPa, and the accuracy is 0.2%, measuring the absolute pressure.

[0039] In order to enhance the sealing performance, in the present invention, it is preferably that the first gas mixing vacuum valve 12 and the second gas mixing vacuum valve 17 and the gas charging vacuum valves are all angle valves and are all sealed through sealing rings.

[0040] Another object of the present invention is to provide a method for measuring the density of a mixed gas at room temperature. The measuring method is implemented based on the above-mentioned measuring system for the density of a mixed gas at room temperature, and the method includes the following steps:

[0041] Step (1): Before using the measurement system, first perform leak detection. After ensuring that the system leak rate meets the requirements, open the second inflation vacuum valve 4, the third inflation vacuum valve 7, and the fourth inflation vacuum valve 10. Open the first gas mixing vacuum valve 12 and the second gas mixing vacuum valve 17. Start the molecular pump set 8 to pump the system to the background vacuum, and then close the third inflation vacuum valve 7;

[0042] Step (2): By setting the first mass flow controller 13 and the second mass flow controller 18, after setting the composition ratio of the mixed gas, introduce the gas. Obtain the molar mass Mgas of the mixed gas through weighted average. First, use the full-range vacuum gauge 2 to measure the pressure below atmospheric pressure, denoted as P1. The gas will be evenly mixed in the gas mixing cavity 11, and then introduced into the inflation cavity 6, causing the pressure in the cavity to continuously increase;

[0043] Step (3): When the pressure value is close to atmospheric pressure (101325 Pa), close the second inflation vacuum valve 4, open the first inflation vacuum valve 3, and start using the positive pressure gauge 1 to record the pressure P2 above atmospheric pressure. After filling to the required pressure, close the third inflation vacuum valve 7 and the fourth inflation vacuum valve 10, close the first pressure reducing valve 15 and the second pressure reducing valve 20. After the pressure value stabilizes, terminate the recording.

[0044] Step (4): During the entire inflation process, each pressure corresponds to a mixed gas density value. According to the ideal gas formula:

[0045] ;

[0046] where ρ is the density of the mixed gas; P is the pressure of the mixed gas, that is, P1 or P2; R is the universal gas constant, and T is the ambient temperature (room temperature). Obtain the mixed gas density values in the entire measurement pressure range at room temperature through the ideal gas formula.

[0047] The mixed gas density values obtained using this measurement system and method are relatively accurate, and the experimental process is not complicated, easy to operate, and can solve the problem of the accuracy of measuring the density of mixed gases in the prior art.

[0048] To better illustrate the effectiveness and superiority of the present invention, an actual test was conducted using a mixed gas of helium and neon as an example, and the obtained data results were summarized and analyzed. The specific details are as Figure 2 shown. During the test process, experiments were conducted on three mixed gas ratios of 1:1, 1:2, and 2:1. The experimental results of each ratio have a good linear relationship. At the same time, each fitting parameter exceeds 0.999, and the deviation degree of the data points from the fitting line is very small, which is sufficient to prove the practical application possibility of the present invention.

[0049] It should be noted that in this document, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or device that includes a series of elements not only includes those elements but also includes other elements not expressly listed, or elements that are inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "including an..." does not exclude the presence of additional identical elements in the process, method, article, or device that includes such element.

[0050] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A mixed gas density measurement system in a normal temperature range, characterized in that: The system comprises: A first gas cylinder, a second gas cylinder, a first pressure reducing valve, a second pressure reducing valve, a first connecting pipe, a second connecting pipe, a first mass flow controller, a second mass flow controller, a gas mixing cavity, a first gas mixing vacuum valve, a second gas mixing vacuum valve, an inflation cavity, a first inflation vacuum valve, a second inflation vacuum valve, a third inflation vacuum valve, a fourth inflation vacuum valve, a positive pressure gauge, a full-range vacuum gauge, a temperature sensor, and a molecular pump set; Among them, the first and second gas cylinders are respectively fixed with a first pressure reducing valve and a second pressure reducing valve at the gas outlet ends, the first and second pressure reducing valves are fixedly connected with a first connecting pipe and a second connecting pipe at the gas outlet ends, the first and second connecting pipes are respectively installed with a first mass flow controller and a second mass flow controller at one end, the first and second mass flow controllers are fixedly connected with a first gas mixing vacuum valve and a second gas mixing vacuum valve at one end, the molecular pump group is fixedly connected with a third inflation vacuum valve, the front part of the inflation cavity is fixedly connected with a temperature sensor, and the two sides are fixedly connected with a positive pressure gauge and the full-range vacuum gauge through the first and second inflation vacuum valves.

2. A mixed gas density measurement system in a normal temperature range according to claim 1, characterized in that: The wall surface of the inflation cavity is provided with a flange interface, and the first inflation vacuum valve, the second inflation vacuum valve, the third inflation vacuum valve, and the fourth inflation vacuum valve are connected to the inflation cavity via the flange interface.

3. A mixed gas density measurement system in a normal temperature range according to claim 1, characterized in that: The gas mixing cavity is actually a KF25 three-way valve, two ends of which are connected to the first gas mixing vacuum valve and the second gas mixing vacuum valve, and the remaining end is connected to the fourth inflation vacuum valve.

4. A mixed gas density measurement system in a normal temperature range according to claim 1, characterized in that: The temperature sensor is a PT100 thermal resistance temperature sensor with a measuring range of -70~200℃.

5. The mixed gas density measurement system in a normal temperature range according to claim 1, characterized in that: The lower limit of the full-scale vacuum gauge pressure measurement is 1×10 -9 hPa, and the range of the positive pressure gauge is 2MPa.

6. A mixed gas density measurement system in a normal temperature range according to claim 3, characterized in that: The first gas mixing vacuum valve, the second gas mixing vacuum valve and the inflation vacuum valve are all angle valves, and are all sealed by sealing rings.

7. A method for measuring the density of a mixed gas at room temperature, characterized in that: The measurement method is implemented based on a mixed gas density measurement system in a normal temperature range according to any one of claims 1 to 6, and the method comprises the following steps: Step (1): Before using the measurement system, first perform a leak test to ensure that the system leakage rate meets the requirements, then open the second gas-filling vacuum valve, the third gas-filling vacuum valve, the fourth gas-filling vacuum valve, the first gas-mixing vacuum valve and the second gas-mixing vacuum valve, start the molecular pump group to evacuate the system to the background vacuum, and then close the third gas-filling vacuum valve; Step (2): After setting the composition ratio of the mixed gas, the first mass flow controller and the second mass flow controller are set to introduce the gas, and the molar mass Mgas of the mixed gas is obtained by weighted average. First, a full-scale vacuum gauge is used to measure the pressure below the atmospheric pressure, which is recorded as P1. The gas will be evenly mixed in the mixed gas cavity, and then introduced into the inflation cavity, so that the pressure in the cavity continues to increase; Step (3): When the pressure value is close to atmospheric pressure, close the second inflation vacuum valve, open the first inflation vacuum valve, and start using a positive pressure gauge to record the pressure P2 above atmospheric pressure. After the pressure reaches the required pressure, close the third inflation vacuum valve and the fourth inflation vacuum valve, close the first pressure reducing valve and the second pressure reducing valve, and stop recording after the pressure value stabilizes. Step (4): During the entire inflation process, each pressure corresponds to a mixed gas density value, which is calculated from the ideal gas formula: ； Where ρ is the density of the mixed gas; P is the pressure of the mixed gas, that is, P1 or P2; R is the universal gas constant, and T is the ambient temperature. The ideal gas formula is used to obtain the density value of the mixed gas in the entire measurement pressure range at room temperature.

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