Device and method for measuring flow characteristic parameters of porous medium

Abstract

The present invention discloses a device and a method for measuring the flow characteristic parameters of a porous medium. The measuring device includes a porous medium fixing device, a small container tank and a large container tank. The porous medium fixing device has a sealed accommodating cavity with both ends penetrating, and the porous medium is arranged in the sealed accommodating cavity. Both ends of the sealed accommodating cavity are respectively connected to the small container tank and the large container tank through on-off valves; a first pressure sensor for measuring pressure is provided on the small container tank, and a second pressure sensor for measuring pressure is provided on the large container tank; different gas sources and / or different vacuum generators are respectively connected to the small container tank and the large container tank, so as to generate a pressure difference between the two container tanks, and make the gas in the small container tank flow to the large container tank. The measurement operation of the present invention is simple and convenient, and the time consumption is short. The permeability coefficient and the inertia coefficient of the porous medium can be measured simultaneously.

Description

Technical Field

[0001] The present invention relates to the measurement of flow characteristic parameters of porous media, and particularly to a device and method for measuring flow characteristic parameters of porous media. Background Art

[0002] Porous media (such as metal aluminum foam materials, titanium alloy porous materials, stainless steel porous materials, nickel alloy porous materials, etc.) have a large number of tiny pores and are often used as throttling elements in the pneumatic field. A throttling element can cause a pressure drop in a pipeline, so it is extremely important to master the flow characteristics of porous media. The relationship between the pressure drop and the flow velocity of the gas flowing inside the porous medium is expressed by the Darcy-Forchheimer law at low flow velocities and by the Forchheimer law when the flow velocity becomes larger. The permeability coefficient and the inertia coefficient are important parameters of the two laws during the internal flow process and need to be obtained through a certain flow measurement method. Most of the existing measurement devices and methods are for measuring the permeability coefficient of porous media, such as CN212228680U, CN106932327A, etc., and do not involve the measurement of the inertia coefficient; moreover, the permeability coefficient measurement method is based on steady-state measurement, which takes a long time and consumes a large amount of gas. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to propose a device and method that can simultaneously and quickly measure the permeability coefficient and the inertia coefficient of porous media.

[0004] Technical Solution: A device for measuring flow characteristic parameters of porous media includes a porous medium fixing device, a small container tank, and a large container tank. The porous medium fixing device has a sealed accommodation cavity that penetrates through both ends. The porous medium is arranged in the sealed accommodation cavity, and both ends of the sealed accommodation cavity are respectively connected to the small container tank and the large container tank through on-off valves; a first pressure sensor for pressure measurement is provided on the small container tank, and a second pressure sensor for pressure measurement is provided on the large container tank; different gas sources and / or different vacuum generators are respectively connected to the small container tank and the large container tank to generate a pressure difference between the two container tanks, so that the gas in the small container tank flows towards the large container tank.

[0005] Further, the volume of the large container tank is 10 to 15 times that of the small container tank.

[0006] Further, the porous medium fixing device includes a hollow rubber and two end caps. The inner cavity of the hollow rubber and the holes reserved on the two end caps together form the sealed accommodation cavity; the porous medium is wrapped in the hollow rubber, and the two end caps squeeze the hollow rubber to achieve sealing.

[0007] A method for measuring flow characteristic parameters of porous media uses the above-mentioned device for measuring flow characteristic parameters of porous media;

[0008] The method includes:

[0009] (1) Calculate the pressure balance point inside the two container tanks when the gas stops flowing after the small container tank and the large container tank are connected.

[0010]

[0011] Where P represents the pressure at equilibrium of the two container tanks, P1 represents the initial pressure of the small container tank, V1 represents the volume of the small container tank, P2 represents the initial pressure of the large container tank, and V2 represents the volume of the large container tank.

[0012] (2) Supply gas using the gas source connected to the small container tank, and supply gas / extract gas using the gas source or vacuum generator connected to the large container tank, so that the two container tanks reach the set pressure, and the initial pressure of the small container tank is much higher than the initial pressure of the large container tank.

[0013] Operate the switch valve to make the gas in the small container tank flow into the large container tank; the measured pressure value of the first pressure sensor is P a , and the measured value of the second pressure sensor is P b ;

[0014] According to the gas state equation and the pressure change curves of the two container tanks, ignoring the influence of temperature, solve the mass flow rate G1 of the gas flowing out of the small container tank and the mass flow rate G2 of the gas flowing into the large container tank respectively.

[0015]

[0016] Where G1 represents the mass flow rate of the gas flowing out of the small container tank, and T1 represents the internal temperature of the small container tank.

[0017]

[0018] Where G2 represents the mass flow rate of the gas flowing into the large container tank, and T2 represents the internal temperature of the large container tank.

[0019] (3) When the pressure difference across the porous medium is 0 - 2 kPa, calculate the permeability coefficient K.

[0020] Calculate the pressure difference at each point within the pressure difference range of 0 - 2 kPa according to the pressure balance point. The calculation formula for the permeability coefficient K is:

[0021]

[0022] Where K represents the permeability coefficient, μ represents the air viscosity, L represents the length of the porous medium, and R represents the gas constant. represents the porosity of the porous medium, A represents the surface area of the porous medium, and P N represents different pressure points within the pressure difference range of 0 - 2 kPa.

[0023] (4) When the pressure difference across the porous medium is 10 - 300 kPa, calculate the inertial coefficient β;

[0024] Taking into account the influence of temperature and pressure changes in both containers, within the pressure difference range of 10 kPa < P a - P b < 300 kPa, first, take the ratio of G1 and G2 corresponding to multiple identical pressure difference moments, and the curve of the obtained ratio varying with the pressure difference is:

[0025]

[0026] where ΔP is the pressure difference across the porous medium; a, b, z are the fitting coefficients of the ratio curve;

[0027] Then smooth f(ΔP) to obtain the curve f’(ΔP) as the new ratio curve of G1(ΔP) / G2(ΔP);

[0028] Finally, use G2(ΔP)·f’(ΔP) as the mass flow rate G3 for calculating the inertial coefficient β within the pressure difference range of 10 - 300 kPa;

[0029] The calculation formula for the inertial coefficient β:

[0030]

[0031] Furthermore, when is satisfied, it is considered that the pressure difference across the porous medium is within 0 - 2 kPa.

[0032] A method for measuring the flow characteristic parameters of a porous medium, using the above device for measuring the flow characteristic parameters of a porous medium;

[0033] The method includes:

[0034] (1) Calculate the pressure balance point inside the two containers when the gas stops flowing after the small container and the large container are connected;

[0035]

[0036] where P represents the pressure at which the two containers are balanced, P1 represents the initial pressure of the small container, V1 represents the volume of the small container, P2 represents the initial pressure of the large container, and V2 represents the volume of the large container;

[0037] (2) Use the vacuum generator connected to the small container to evacuate the gas, and use the vacuum generator connected to the large container to evacuate the gas, so that the two containers reach the set pressure, and the initial pressure of the small container is much higher than the initial pressure of the large container;

[0038] Operate the switch valve to make the gas in the small container tank flow into the large container tank; the pressure measurement value of the first pressure sensor is P a , and the measurement value of the second pressure sensor is P b ;

[0039] According to the gas state equation and the pressure change curves of the two container tanks, ignoring the influence of temperature, respectively solve the gas mass flow rate G1 flowing out of the small container tank and the gas mass flow rate G2 flowing into the large container tank;

[0040]

[0041] Among them, G1 represents the gas mass flow rate flowing out of the small container tank, and T1 represents the internal temperature of the small container tank;

[0042]

[0043] Among them, G2 represents the gas mass flow rate flowing into the large container tank, and T2 represents the internal temperature of the large container tank;

[0044] (3) When the pressure difference at both ends of the porous medium is 0 - 2 kPa, calculate the permeability coefficient K;

[0045] According to the pressure balance point, calculate the pressure difference at each point within the pressure difference range of 0 - 2 kPa. The calculation formula for the permeability coefficient K is:

[0046]

[0047] Among them, K represents the permeability coefficient, μ represents the air viscosity, L represents the length of the porous medium, R represents the gas constant, represents the porosity of the porous medium, A represents the surface area of the porous medium, P N represents different pressure difference points within the pressure difference range of 0 - 2 kPa;

[0048] (4) When the pressure difference at both ends of the porous medium is 10 - 100 kPa, calculate the inertial coefficient β;

[0049] Taking into account the influence of the temperature and pressure changes of the two container tanks, within the pressure difference range of 10 kPa < P a -P b < 100 kPa, first process the ratio of G1 and G2 corresponding to multiple moments of the same pressure difference. The curve of the obtained ratio changing with the pressure difference is

[0050]

[0051] Among them, ΔP is the pressure difference at both ends of the porous medium; a, b, z are the fitting coefficients of the ratio curve;

[0052] Smoothing f(ΔP) again to obtain the curve f’(ΔP) as the new ratio curve of G1(ΔP) / G2(ΔP);

[0053] Finally, using G2(ΔP)·f’(ΔP) as the mass flow rate G3 for calculating the inertia coefficient β within the pressure difference range of 10 - 100 kPa;

[0054] Calculation formula for the inertia coefficient β:

[0055]

[0056] Furthermore, when is satisfied, it is considered that the pressure difference at both ends of the porous medium is within 0 - 2 kPa.

[0057] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0058] (1) The measurement operation is simple and convenient, time-consuming is short, and the permeability coefficient and inertia coefficient of the porous medium can be measured simultaneously through one experiment;

[0059] (2) By using two container tanks for inflation / air extraction, the adjustment of different pressure test conditions at both ends of the porous medium can be realized;

[0060] (3) By combining a large and a small container tank, after processing the mass flow rates of the gas flowing in and out of the small and large container tanks, the mass flow rate of the gas passing through the porous medium is obtained more accurately. Brief description of the drawings

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required to be used in the embodiments of the present invention. Obviously, the following described drawings are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0062] Figure 1 It is a schematic structural diagram of a porous medium flow characteristic parameter measurement device in Embodiment 1 of the present application;

[0063] Figure 2 It is a schematic structural diagram of a porous medium fixing device in an embodiment of the present application

[0064] Figure 3 It is Figure 2 The A - A cross-sectional view of;

[0065] Figure 4 It is a graph showing the change of the pressure of two container tanks with time in Embodiment 1 of the present application;

[0066] Figure 5It is a schematic structural diagram of the porous medium flow characteristic parameter measurement device in the second embodiment of the present application;

[0067] Figure 6 It is a graph showing the change of the pressure of two container tanks over time in the second embodiment of the present application;

[0068] Figure 7 It is a schematic structural diagram of the porous medium flow characteristic parameter measurement device in the third embodiment of the present application;

[0069] Figure 8 It is a graph showing the change of the pressure of two container tanks over time in the third embodiment of the present application;

[0070] Figure 9 It is a schematic diagram showing the relationship between the flow rate and the pressure difference of two container tanks in the embodiment of the present application;

[0071] Figure 10 It is a schematic diagram for dividing the pressure difference area for calculating the permeability coefficient and the inertia coefficient;

[0072] Figure 11 It is a flow chart of the method for measuring the porous medium flow characteristic parameters in the embodiment of the present application;

[0073] Reference numerals: 1, porous medium fixing device; 1-1, end cover; 1-2, hollow rubber; 1-3, porous medium; 2, first switching valve; 3, small container tank; 4, second switching valve; 5, first gas source; 6, PC; 7, first pressure sensor; 8, 16-bit A / D acquisition board; 9, second pressure sensor; 10, third switching valve; 11, second gas source; 12, large container tank; 13, fourth switching valve; 14, first muffler; 15, first vacuum generator; 16, first pressure reducing valve; 17, second pressure reducing valve; 18, second vacuum generator; 19, second muffler. Detailed implementation manners

[0074] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are not all the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0075] Embodiment 1

[0076] Figure 1 Shown is a schematic structural diagram of the porous medium flow characteristic parameter measurement device provided in Embodiment 1 of the present application. The measurement device includes a porous medium fixing device 1, a small container tank 3, a large container tank 12, a PC 6, and a 16-bit A / D acquisition board 8.

[0077] As Figure 2 AndFigure 3 As shown in the figure, the porous medium fixing device 1 includes a hollow rubber 1-2 and two end caps 1-1. The inner cavity of the hollow rubber 1-2 and the holes reserved on the two end caps 1-1 together form a sealed accommodating cavity that penetrates through both ends. The porous medium 1-3 is wrapped in the hollow rubber 1-2, and the two end caps 1-1 are connected by bolts to squeeze the hollow rubber 1-2 to achieve sealing.

[0078] The small container tank 3 and the large container tank 12 are two container tanks with known volumes. The volume of the large container tank 12 is 10 to 15 times that of the small container tank 3. One end of the sealed accommodating cavity is connected to the small container tank 3 through the first switching valve 2, and the other end is connected to the large container tank 12 through the fourth switching valve 13. A first pressure sensor 7 with a larger measuring range for pressure measurement is provided on the small container tank 3, and a second pressure sensor 9 with a smaller measuring range for pressure measurement is provided on the large container tank 12. The first pressure sensor 7 and the second pressure sensor 9 are respectively connected to the PC 6 through a 16-bit A / D acquisition board 8.

[0079] The small container tank 3 is connected to the first gas source 5 through the second switching valve 4, and the large container tank 12 is connected to the second gas source 11 through the third switching valve 10.

[0080] In the first embodiment, the measuring range of the first pressure sensor 7 is 0 to 300 kPa, and the measuring range of the second pressure sensor 9 is 0 to 100 kPa.

[0081] The following introduces the method for measuring the flow characteristic parameters of the porous medium using the measuring device described in the first embodiment. As Figure 11 shown, the method specifically includes the following steps:

[0082] (1) Calculate Figure 4 the pressure balance point in.

[0083] The pressure balance point can be derived according to the gas state equation. The initial ideal state equation of the gas in the small container tank 3 is:

[0084] P1V1 = m1RT1

[0085] where P1 represents the initial pressure of the small container tank 3, V1 represents the volume of the small container tank 3, m1 represents the initial gas mass of the small container tank 3, R represents the gas constant, and T1 represents the initial temperature of the small container tank 3.

[0086] The initial ideal state equation of the gas in the large container tank 12 is:

[0087] P2V2 = m2RT2

[0088] where P2 represents the initial pressure of the large container tank 12, V2 represents the volume of the large container tank 12, m2 represents the initial gas mass of the large container tank 12, and T2 represents the initial temperature of the large container tank 12.

[0089] The ideal gas state equation for the gas when the two containers are in equilibrium is:

[0090] P,(V1 + V2) = (m1 + m2)RT,

[0091] where P, represents the pressure when the two containers are in equilibrium, and T, represents the temperature when the two containers are in equilibrium.

[0092] Ignoring the temperature effect, the equilibrium pressure value can be obtained:

[0093]

[0094] (2) Open the second switching valve 4 and the third switching valve 10, and use the first gas source 5 and the second gas source 11 to supply gas to the small container 3 and the large container 12 respectively, so that the two containers reach the set pressure. It is required that the initial pressure of the small container 3 is much higher than that of the large container 12, and the pressures of the large and small containers are required not to exceed the measurement ranges of the corresponding pressure sensors.

[0095] When the two gas sources stop supplying gas, open the first switching valve 2 and the fourth switching valve 13 at both ends of the porous medium fixing device 1. The gas in the small container 3 flows into the large container 12. The first pressure sensor 7 and the second pressure sensor 9 respectively record the pressure changes of the small container 3 and the large container 12 on the PC 6 through the 16-bit A / D acquisition board 8. The pressure detected by the first pressure sensor 7 is P a , and the pressure detected by the second pressure sensor 12 is P b , and the pressure change curve is as Figure 8 shown.

[0096] According to the gas state equation and the pressure change curves of the two containers, under the assumption of ignoring the temperature effect, the mass flow rate of the gas flowing out of the small container 3 and the mass flow rate of the gas flowing into the large container 12 are solved respectively. The solution results are as Figure 9 shown.

[0097] The mass flow rate of the gas flowing out of the small container 3

[0098]

[0099] where G1 represents the mass flow rate of the gas flowing out of the small container 3, and T1 represents the internal temperature of the small container 3.

[0100] The mass flow rate of the gas flowing into the large container 12

[0101]

[0102] where G2 represents the mass flow rate of the gas flowing into the large container 12, and T2 represents the internal temperature of the large container 12.

[0103] (3) Within Figure 10 the indicated small pressure difference ΔPa (0 - 2 kPa) range, calculate the permeability coefficient K based on the mass flow rate of the gas passing through the porous medium.

[0104] Since the accuracy of the first pressure sensor 7 is low (large range, low accuracy) and G1 is inaccurate, G2 is used as the gas mass flow rate of the gas passing through the porous medium for calculating the permeability coefficient K.

[0105] When is satisfied, it can be considered that the pressure difference at both ends of the porous medium 1 - 3 is within the small pressure difference range of 0 - 2 kPa.

[0106] Calculate the pressure difference at each point within the small pressure difference range according to the pressure balance point. The calculation formula for the permeability coefficient K is:

[0107]

[0108] where K represents the permeability coefficient, μ represents the air viscosity, R represents the gas constant, L represents the length of the porous medium, represents the porosity of the porous medium, A represents the surface area of the porous medium, P N represents different pressure points within the pressure difference range of 0 - 2 kPa;

[0109] (4) In Figure 10 the indicated large pressure difference ΔPb (10 - 300 kPa) range, calculate the inertia coefficient β based on the mass flow rate of the gas passing through the porous medium.

[0110] Since the volume of the large container tank 12 is relatively large, during gas flow, the temperature change is small and the pressure change is small. The small pressure change makes the pressure curve measured by the second pressure sensor 9 relatively smooth, but the change range of this pressure curve is small, which will lead to inaccurate calculation of G2. While the volume of the small container tank 3 is small, and the temperature and pressure change greatly. The large pressure change makes the pressure curve measured by the first pressure sensor 7 rough, and due to the large temperature change, G1 is even more inaccurate compared to G2. Therefore, considering the influence of temperature and pressure changes comprehensively, within the large pressure difference range of 10 kPa < P a - P b < 300 kPa, first process the ratio of G1 and G2 corresponding to multiple identical pressure difference moments. The obtained ratio curve varying with the pressure difference is

[0111]

[0112] where ΔP is the pressure difference at both ends of the porous medium; a, b, z are the fitting coefficients of the ratio curve;

[0113] Then smooth f(ΔP) to obtain the curve f’(ΔP) as the ratio curve of G1(ΔP) / G2(ΔP).

[0114] Finally, use G2(ΔP)·f’(ΔP) as the mass flow rate for calculating the inertia coefficient β in the large pressure difference range, and denote this mass flow rate as G3.

[0115] The inertia coefficient β is calculated according to the following formula:

[0116]

[0117] Embodiment 2

[0118] Figure 5 The figure shows a schematic structural diagram of a porous medium flow characteristic parameter measurement device provided by Embodiment 2 of the present application. On the basis of Embodiment 1, a first vacuum generator 15 and a first pressure reducing valve 16 are added between the third switching valve 10 and the second gas source 11, and a first muffler 14 is connected to the first vacuum generator 15. The first vacuum generator 15 is used to generate negative pressure in the large container tank 12.

[0119] In this Embodiment 2, the range of the first pressure sensor 7 is 0 - 300 kPa, and the range of the second pressure sensor 9 is -100 - 0 kPa.

[0120] Figure 6 The figure shows the pressure change curves of the two container tanks in Embodiment 2.

[0121] When measuring, in step (2) of Embodiment 1, after generating positive pressure inside the small container tank 3 and negative pressure inside the large container tank 12, then perform the operations of the subsequent steps in Embodiment 1, and the subsequent steps are the same as those in Embodiment 1.

[0122] Embodiment 3

[0123] Figure 7 The figure shows a schematic structural diagram of a porous medium flow characteristic parameter measurement device provided by Embodiment 3 of the present application. On the basis of Embodiment 2, a second pressure reducing valve 17 and a second vacuum generator 18 are added between the second switching valve 4 and the first gas source 5, and a second muffler 19 is connected to the second vacuum generator 18. The second vacuum generator 18 is used to generate negative pressure in the small container tank 3.

[0124] In this Embodiment 3, the first pressure sensor 7 is a pressure sensor with a range of -100 - 0 kPa, and the second pressure sensor 9 has a range of -100 - -50 kPa.

[0125] Figure 8 The figure shows the pressure change curves of the two container tanks in Embodiment 3.

[0126] When making measurements, in step (2) of the first embodiment, after the vacuum generators at both ends of the two container tanks generate negative pressure, the subsequent steps in the first embodiment are then carried out. In addition, the range of the large pressure difference region determined in the third embodiment is different from that of the embodiment. In the third embodiment, when calculating the inertia coefficient β, the large pressure difference range is determined as 10 kPa < P a -P b < 100 kPa. The other steps in the third embodiment are the same as those in the first embodiment.

[0127] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or replacement solutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An apparatus for measuring the flow characteristic parameters of a porous medium, characterized in that, It includes a porous medium fixing device (1), a small container tank (3) and a large container tank (12). The porous medium fixing device (1) has a sealed accommodation cavity that penetrates through both ends. A porous medium (1-3) is arranged in the sealed accommodation cavity. Both ends of the sealed accommodation cavity are respectively connected to the small container tank (3) and the large container tank (12) through on-off valves. A first pressure sensor (7) for pressure measurement is provided on the small container tank (3), and a second pressure sensor (9) for pressure measurement is provided on the large container tank (12). Different gas sources and / or different vacuum generators are respectively connected to the small container tank (3) and the large container tank (12) to generate a pressure difference between the two container tanks, so that the gas in the small container tank (3) flows into the large container tank (12).

2. The device for measuring the flow characteristic parameters of a porous medium according to claim 1, wherein The volume of the large container tank (12) is 10 to 15 times that of the small container tank (3).

3. The device for measuring the flow characteristic parameters of the porous medium according to claim 1, characterized in that, The porous medium fixing device (1) includes a hollow rubber (1-2) and two end caps (1-1). The inner cavity of the hollow rubber (1-2) and the holes reserved on the two end caps (1-1) together form a sealed accommodation cavity. The porous medium (1-3) is wrapped in the hollow rubber (1-2), and the two end caps (1-1) squeeze the hollow rubber (1-2) to achieve sealing.

4. A method for measuring the flow characteristic parameters of a porous medium, characterized in that, Use the device for measuring the flow characteristic parameters of the porous medium according to any one of claims 1 to 3; The method includes: (1) Calculate the pressure balance point inside the two container tanks when the gas stops flowing after the small container tank (3) and the large container tank (12) are connected; Where P’ represents the pressure when the two container tanks are balanced, P1 represents the initial pressure of the small container tank (3), V1 represents the volume of the small container tank (3), P2 represents the initial pressure of the large container tank (12), and V2 represents the volume of the large container tank (12); (2) Supply gas using the gas source connected to the small container tank (3), and supply gas or evacuate gas using the gas source or vacuum generator connected to the large container tank (12), so that the two container tanks reach the set pressure, and the initial pressure of the small container tank (3) is much higher than the initial pressure of the large container tank (12); Operate the switch valve to make the gas in the small container tank (3) flow into the large container tank (12); the pressure measurement value of the first pressure sensor (7) is P a , and the measurement value of the second pressure sensor (9) is P b ; According to the gas state equation and the pressure change curves of the two container tanks, when the influence of temperature is ignored, respectively solve the mass flow rate G1 of the gas flowing out of the small container tank (3) and the mass flow rate G2 of the gas flowing into the large container tank (12); Where G1 represents the mass flow rate of the gas flowing out of the small container tank (3), and T1 represents the internal temperature of the small container tank (3); Where G2 represents the mass flow rate of the gas flowing into the large container tank (12), and T2 represents the internal temperature of the large container tank (12); (3) When the pressure difference across the porous medium (1-3) is 0 to 2 kPa, calculate the permeability coefficient K; Calculate the pressure difference at each point within the pressure difference range of 0 to 2 kPa according to the pressure balance point. The calculation formula for the permeability coefficient K is: Where K represents the permeability coefficient, μ represents the air viscosity, R represents the gas constant, L represents the length of the porous medium (1-3), represents the porosity of the porous medium (1-3), A represents the surface area of the porous medium (1-3), P N represents different pressure points within the pressure difference range of 0 to 2 kPa; (4) When the pressure difference across the porous medium (1-3) is 10 to 300 kPa, calculate the inertia coefficient β; Taking into account the influence of temperature and pressure changes in both containers, within the differential pressure range of 10 kPa < P a - P b < 300 kPa, first, the ratio of G1 and G2 corresponding to multiple identical differential pressure moments is processed, and the curve of the obtained ratio changing with the differential pressure is as follows: Where ΔP is the pressure difference across the porous medium; a, b, z are the fitting coefficients of the ratio curve; Then smooth f(ΔP) to obtain the curve f’(ΔP) as the new ratio curve of G1(ΔP) / G2(ΔP); Finally, use G2(ΔP)·f’(ΔP) as the mass flow rate G3 for calculating the inertia coefficient β within the pressure difference range of 10 - 300 kPa. Calculation formula for the inertia coefficient β:

5. The method for measuring the flow characteristic parameters of a porous medium according to claim 4, characterized in that When is satisfied, the pressure difference across the porous medium (1-3) is considered to be within 0 to 2 kPa.

6. A method for measuring the flow characteristic parameters of a porous medium, characterized in that, Adopt the device for measuring the flow characteristic parameters of the porous medium described in any one of claims 1 to 3. The method includes: (1) Calculate the pressure balance point inside the two container tanks when the gas stops flowing after the small container tank (3) and the large container tank (12) are connected. Where P’ represents the pressure at equilibrium of the two container tanks, P1 represents the initial pressure of the small container tank (3), V1 represents the volume of the small container tank (3), P2 represents the initial pressure of the large container tank (12), and V2 represents the volume of the large container tank (12). (2) Use the vacuum generator connected to the small container tank (3) to evacuate the gas, and use the vacuum generator connected to the large container tank (12) to evacuate the gas, so that the two container tanks reach the set pressure, and the initial pressure of the small container tank (3) is much higher than the initial pressure of the large container tank (12). Operate the switching valve to make the gas in the small container tank (3) flow into the large container tank (12); the measured pressure value of the first pressure sensor (7) is P a , and the measured value of the second pressure sensor (9) is P b ; According to the gas state equation and the pressure change curves of the two container tanks, and ignoring the influence of temperature, respectively solve the mass flow rate G1 of the gas flowing out of the small container tank (3) and the mass flow rate G2 of the gas flowing into the large container tank (12). Where G1 represents the mass flow rate of the gas flowing out of the small container tank (3), and T1 represents the internal temperature of the small container tank (3). Where G2 represents the mass flow rate of the gas flowing into the large container tank (12), and T2 represents the internal temperature of the large container tank (12). (3) When the pressure difference across the porous medium (1 - 3) is 0 - 2 kPa, calculate the permeability coefficient K. Calculate the pressure difference at each point within the pressure difference range of 0 - 2 kPa according to the pressure balance point. The calculation formula for the permeability coefficient K is: where K represents the permeability coefficient, μ represents the air viscosity, R represents the gas constant, L represents the length of the porous medium (1-3), represents the porosity of the porous medium (1-3), A represents the surface area of the porous medium (1-3), P N represents different pressure points within the pressure difference range of 0 to 2 kPa; (4) When the pressure difference across the porous medium (1 - 3) is 10 - 100 kPa, calculate the inertia coefficient β. Taking into account the influence of temperature and pressure changes in both containers, within the differential pressure range of 10 kPa < P a - P b < 100 kPa, first, the ratio of G1 and G2 corresponding to multiple identical differential pressure moments is processed, and the curve of the obtained ratio changing with the differential pressure is Where ΔP is the pressure difference across the porous medium; a, b, z are the fitting coefficients of the ratio curve. Then perform a smoothing process on f(ΔP) to obtain the curve f’(ΔP) as the new ratio curve of G1(ΔP) / G2(ΔP). Finally, use G2(ΔP)·f’(ΔP) as the mass flow rate G3 for calculating the inertia coefficient β within the pressure difference range of 10 - 100 kPa. Calculation formula for the inertia coefficient β:

7. The method for measuring the flow characteristic parameters of a porous medium according to claim 6, wherein When is satisfied, the pressure difference across the porous medium (1-3) is considered to be within 0 to 2 kPa.

Images