Gas-liquid two-phase flow instantaneous pressure surface measuring method and measuring instrument

Abstract

The invention relates to the technical field of pressure measurement, in particular to a gas-liquid two-phase flow instantaneous pressure surface measurement method and a gas-liquid two-phase flow instantaneous pressure surface measurement instrument. The invention discloses a gas-liquid two-phase flow instantaneous pressure surface measurement method. The method comprises the following steps: acquiring bubble state information of a gas-liquid two-phase flow region; establishing a corresponding relationship between the bubble state information and the pressure in the bubble; obtaining a mapping relation between the bubble state information and the bubble external liquid phase pressure according to the balance condition of the bubble internal pressure and the corresponding relation; and introducing the bubble state information into the mapping relation and the corresponding relation to obtain bubble internal and external instantaneous pressure. According to the method, the bubble internal pressure and the bubble external liquid phase pressure are obtained by calculating the bubble state information of the gas-liquid two-phase flow area, so that the interference of a measuring device on a local flow field when the internal pressure field of the gas-liquid two-phase flow system is obtained through the measuring device is avoided, and the measuring result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure measurement, and in particular to a method and a measuring instrument for measuring the instantaneous pressure surface of a gas-liquid two-phase flow. Background Art

[0002] At present, pressure measurement methods can be divided into two categories: mechanical and electrical. Mechanical pressure gauges use the force of fluid on sensitive elements to sense pressure. The main types are: liquid column type, elastic type, load type, etc. Liquid column pressure gauges measure by balancing the pressure generated by a liquid column of a certain height with the measured pressure. Elastic pressure gauges use the principle of elastic elements of various shapes to deform under pressure for measurement. They can be divided into spring tube pressure gauges, diaphragm pressure gauges, diaphragm box pressure gauges and bellows pressure gauges. Load pressure measuring instruments are often called load pressure gauges. They are made directly according to the definition of pressure. Common ones include piston pressure gauges, float pressure gauges and bell pressure gauges. Electrical pressure measuring instruments use the physical properties of metals or semiconductors to directly convert pressure into voltage, current signals or frequency signals for output, or convert the deformation of elastic bodies into voltage and current signals for output through resistance strain gauges. Representative products include piezoelectric, piezoresistive, vibration frequency, capacitive and strain gauges.

[0003] Due to the characteristics of the pressure field distribution inside the gas-liquid two-phase flow system, the application of traditional measurement methods is difficult. The specific analysis is as follows:

[0004] (1) The pressure change in the gas-liquid two-phase flow field mainly occurs in the local area with bubbles. From the perspective of geometric size, the geometric characteristic size of the bubble (less than 1 mm) is small, which is comparable to or even smaller than the geometric size of the pressure sensitive element. Ordinary pressure sensors are no longer applicable.

[0005] (2) From the perspective of the liquid vaporization principle and the temporal and spatial distribution of bubbles, when the liquid vaporizes, bubbles will be generated on the wall or in the flow field. The distribution in space and time has a certain randomness. Fixed pressure measurement points are difficult to capture the distribution changes of the pressure field in space and time.

[0006] (3) The pressure field changes in the gas-liquid two-phase flow field are surface distributions, and traditional pressure measurement methods are difficult to achieve surface measurement. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method and a measuring instrument for measuring the instantaneous pressure surface of a gas-liquid two-phase flow.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for measuring the instantaneous pressure surface of gas-liquid two-phase flow, comprising the following steps:

[0009] Obtain bubble state information in the gas-liquid two-phase flow region;

[0010] Establishing a corresponding relationship between the bubble state information and the pressure inside the bubble;

[0011] According to the equilibrium condition of the pressure inside the bubble and the corresponding relationship, a mapping relationship between the bubble state information and the liquid phase pressure outside the bubble is obtained;

[0012] The bubble state information is introduced into the mapping relationship and the corresponding relationship to obtain the pressure inside the bubble and the liquid phase pressure outside the bubble.

[0013] Preferably, the bubble state information includes bubble temperature and bubble volume in the gas-liquid two-phase flow region;

[0014] Establishing a corresponding relationship between the bubble state information and the pressure inside the bubble includes:

[0015] The corresponding relationship among the bubble temperature, the bubble volume and the pressure inside the bubble is established.

[0016] Preferably, the bubble volume is calculated by the bubble radius;

[0017] The establishing the corresponding relationship among the bubble temperature, the bubble volume and the pressure inside the bubble comprises:

[0018] Obtain the initial state equation of the bubble;

[0019] The initial state equation is transformed to obtain the corresponding relationship among the bubble temperature, the bubble radius, the pressure inside the bubble and the gas mass.

[0020] Preferably, if the gas properties of the bubbles deviate from the gas properties of the ideal gas by more than a preset range, the van der Waals equation of state is used as the initial state equation.

[0021] Preferably, the step of obtaining the bubble state information in the gas-liquid two-phase flow region includes:

[0022] Acquiring image information of the gas-liquid two-phase flow region using an image capture device;

[0023] Acquire the bubble temperature and the bubble radius from the image information;

[0024] The bubble volume is calculated using the bubble radius.

[0025] Preferably, obtaining the mapping relationship between the bubble state information and the liquid phase pressure outside the bubble according to the equilibrium condition of the pressure inside the bubble and the corresponding relationship includes:

[0026] Obtaining a calculated relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble;

[0027] According to the calculation relationship and the corresponding relationship, a mapping relationship between the liquid phase pressure outside the bubble and the bubble temperature and the bubble volume is obtained.

[0028] Preferably, the step of obtaining the calculation relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble comprises:

[0029] The calculation equation between the pressure inside the bubble and the pressure of the liquid phase outside the bubble is established according to a nonlinear partial differential equation, and the calculation relationship is obtained in combination with the correction of the non-equilibrium state.

[0030] A gas-liquid two-phase flow instantaneous pressure surface measuring instrument, comprising an illumination light source, an experimental flow field device and an image capturing device;

[0031] The illumination light source is located directly above the experimental flow field device, and the image capture device is located directly below the experimental flow field device;

[0032] The experimental flow field device is in a transparent state;

[0033] The image capture device is used to capture image information of the gas-liquid two-phase flow region in the experimental flow field device;

[0034] The illumination light source is used to provide illumination for the gas-liquid two-phase flow region in the experimental flow field device.

[0035] Preferably, the image capturing device comprises: an infrared thermal imager and a high-speed camera.

[0036] Preferably, it also includes a data acquisition device;

[0037] The data acquisition device is connected to the image capturing device for acquiring the image information.

[0038] The implementation of the present invention has the following beneficial effects:

[0039] The present invention calculates the bubble internal pressure and the liquid phase pressure outside the bubble after the bubble state information in the gas-liquid two-phase flow area, thereby avoiding the interference of the measuring device on the local flow field when obtaining the internal pressure field of the gas-liquid two-phase flow system through the measuring device, and making the measurement result more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0041] Figure 1 A flow chart of a method for measuring the instantaneous pressure surface of a gas-liquid two-phase flow in one embodiment;

[0042] Figure 2 Schematic diagram of a gas-liquid two-phase flow instantaneous pressure surface measuring instrument in one embodiment. DETAILED DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0044] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0045] The embodiment of the present invention provides a method for measuring the instantaneous pressure surface of a gas-liquid two-phase flow, such as Figure 1 As shown, the following steps are included:

[0046] Obtain bubble state information in the gas-liquid two-phase flow region.

[0047] Optionally, the bubble state information includes one or more of the mass, volume and temperature of the gas in the bubble.

[0048] Establish the corresponding relationship between the bubble state information and the pressure inside the bubble.

[0049] It can be understood that the gas in the bubble follows certain state equations and process equations, and there is a definite relationship. Therefore, when the bubble state information of the gas in the bubble under a certain state is known, the internal pressure is obtained according to the corresponding state equation.

[0050] According to the equilibrium condition and corresponding relationship of the pressure inside the bubble, the mapping relationship between the bubble state information and the liquid phase pressure outside the bubble is obtained.

[0051] Specifically, the bubble evolution process is regarded as a quasi-static process. Then the pressure inside the bubble in the initial state p g0 The pressure of the liquid outside the bubble p l The relationship can be expressed as:

[0052]

[0053] Where σ is the surface tension of the liquid, Δp 0 is the residual pressure that drives the bubble to grow. 0 is the initial radius of the bubble; p g0 represents the pressure inside the bubble in the initial state, p l is the liquid pressure outside the bubble.

[0054] The bubble state information is introduced into the mapping relationship and the corresponding relationship to obtain the pressure inside the bubble and the liquid phase pressure outside the bubble.

[0055] The present invention calculates the pressure inside the bubble and the liquid phase pressure outside the bubble after the bubble state information in the gas-liquid two-phase flow area, avoiding the interference of the measuring device on the local flow field when obtaining the internal pressure field of the gas-liquid two-phase flow system through the measuring device, making the measurement result more accurate. At the same time, the bubbles are distributed on the entire pressure surface of the pressure field in the gas-liquid two-phase flow field, and the calculation through the bubble state information can realize the measurement in the dimension of the surface.

[0056] In some executable embodiments, the bubble state information includes bubble temperature and bubble volume in the gas-liquid two-phase flow region.

[0057] Establish the corresponding relationship between the bubble state information and the pressure inside the bubble, including:

[0058] The corresponding relationship among bubble temperature, bubble volume and pressure inside the bubble is established.

[0059] Specifically, the gas in the bubble follows certain state equations and process equations, and there is a definite PVT (pressure-volume-temperature) relationship.

[0060] In some executable embodiments, the bubble volume is calculated by the bubble radius.

[0061] Establish the corresponding relationship between bubble temperature, bubble volume and pressure inside the bubble, including:

[0062] Get the initial state equation of the bubble.

[0063] Specifically, the initial state equation is as follows:

[0064] p g0 V 0 =mR g T 0 (2)

[0065] In the formula, p g0 Indicates the pressure inside the bubble in the initial state; V 0 represents the volume of the bubble; m represents the mass of the gas in the bubble; T 0 represents the initial temperature of the bubble; R g represents the gas constant.

[0066] The initial state equation is transformed to obtain the corresponding relationship among bubble temperature, bubble radius, pressure inside the bubble and gas mass.

[0067] Specifically, the gas mass formula is obtained after transformation:

[0068]

[0069] In the formula, p g0 Indicates the pressure inside the bubble in the initial state; V 0 represents the volume of the bubble; m represents the mass of the gas in the bubble; T 0 represents the initial temperature of the bubble; R g represents the gas constant.

[0070] Furthermore, assuming that the bubble shape is spherical, the corresponding relationship between the bubble temperature, bubble radius, bubble internal pressure and gas mass is as follows:

[0071]

[0072] In the formula, p g represents the pressure inside the bubble; T represents the temperature of the bubble; r represents the radius of the bubble; m represents the mass of the gas inside the bubble; R g represents the gas constant.

[0073] In some executable embodiments, if the gas properties of the bubbles deviate from the gas properties of the ideal gas by more than a preset range, the van der Waals equation of state is used as the initial state equation.

[0074] Furthermore, this can be achieved by measuring the pressure, volume and temperature of the bubble gas and calculating the compressibility coefficient Z. The compressibility coefficient Z is defined as the ratio of the experimental value of the actual gas to the ideal gas state equation. If the deviation of the value of Z from 1 exceeds a preset deviation range (e.g., 5%), it is considered that the deviation of the gas properties of the bubble from the ideal gas properties exceeds the preset range.

[0075] Specifically, the general formula of the initial state equation of the van der Waals state equation is as follows:

[0076] p g =f(T,r) (5)

[0077] In the formula, p g represents the pressure inside the bubble; T represents the temperature of the bubble; r represents the radius of the bubble; f(T,r) represents the van der Waals state function.

[0078] In some executable embodiments, obtaining bubble state information in a gas-liquid two-phase flow region includes:

[0079] The image information of the gas-liquid two-phase flow area is obtained using an image capture device.

[0080] Specifically, the image information includes bubble temperature image information and bubble volume image information.

[0081] In some scenarios, the bubble temperature image information is image information of an infrared image of the bubble, and the bubble volume image information is image information of the bubble recorded by a high-speed camera.

[0082] Optionally, the bubble volume image information is a photo of a bubble group with a reference object taken by a high-speed camera.

[0083] The bubble temperature and bubble radius are obtained from the image information.

[0084] Specifically, the bubble temperature is obtained from the bubble temperature image information, and the bubble radius is obtained from the bubble volume image information.

[0085] Furthermore, the radius of the bubbles in the bubble group photo may be measured by using a measuring device.

[0086] In some scenarios, the bubble temperature is consistent with the ambient temperature, and the bubble temperature is obtained by the ambient temperature.

[0087] The bubble volume is calculated using the bubble radius.

[0088] The present invention can obtain a real-time distribution image of the pressure field through infrared thermal imaging images and high-speed camera images at each moment. At the same time, by calculating the pressure of each bubble area in a surface, the present invention can display the pressure field distribution of a measurement surface in real time.

[0089] In some executable embodiments, according to the equilibrium condition and corresponding relationship of the pressure inside the bubble, a mapping relationship between the bubble state information and the liquid phase pressure outside the bubble is obtained, including:

[0090] Get the calculated relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble.

[0091] Specifically, the calculation formula is as follows:

[0092]

[0093] In the formula, σ is the surface tension of the liquid, Δp is the residual pressure that drives the bubble to grow. r is the bubble radius; p g represents the pressure inside the bubble, p l is the liquid pressure outside the bubble.

[0094] According to the calculation relationship and the corresponding relationship, the mapping relationship between the liquid phase pressure outside the bubble and the bubble temperature and bubble volume is obtained.

[0095] In some executable embodiments, obtaining a calculated relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble includes:

[0096] The calculation equation between the pressure inside the bubble and the pressure of the liquid phase outside the bubble is established according to the nonlinear partial differential equation, and the calculation relationship is obtained by combining the correction of the non-equilibrium state.

[0097] Specifically, the nonlinear partial differential equation is the Young-Laplace formula.

[0098] The calculation relationship of this embodiment is as follows:

[0099]

[0100] In the formula, p l Indicates the liquid pressure, p g represents the gas pressure; α p is the pressure correction coefficient, which is related to the viscosity of the fluid and can be calibrated by the test value before the formal test and the pressure of the known point; σ is the surface tension of the liquid, and r is the bubble radius.

[0101] A gas-liquid two-phase flow instantaneous pressure surface measuring instrument comprises an illumination light source, an experimental flow field device and an image capturing device.

[0102] The illumination light source is located directly above the experimental flow field device, and the image capturing device is located directly below the experimental flow field device.

[0103] The experimental flow field device is in a transparent state.

[0104] The image capture device is used to capture image information of the gas-liquid two-phase flow area in the experimental flow field device.

[0105] The illumination light source is used to provide illumination for the gas-liquid two-phase flow area in the experimental flow field device.

[0106] In some executable embodiments, the image capturing device includes: an infrared thermal imager and a high-speed camera.

[0107] In some executable embodiments, a data acquisition device is also included.

[0108] The data acquisition device is connected to the image capture device to obtain image information.

[0109] In one embodiment, Figure 2 As shown, in the figure, 1 is an illumination light source, 2 is an experimental flow field device, 3 is a data acquisition computer, 4 is an infrared thermal imager, and 5 is a high-speed camera.

[0110] In an executable embodiment, the gas state equation is an ideal gas state equation, the temperature field information of the flow field is obtained by infrared thermal imaging 4, and the geometric information of the bubble is obtained by a high-speed camera 5. The steps of the method are as follows:

[0111] At the initial moment of bubble formation, the temperature of the bubble is obtained by the infrared thermal imager, the bubble radius is obtained by the high-speed camera, and the bubble volume is calculated;

[0112] The mass of the gas in the bubble is calculated from the bubble volume and temperature according to the gas state equation;

[0113] During the evolution of the bubble, the bubble temperature is obtained at each state point by infrared thermal imager, and the radius is obtained by high-speed camera to calculate the volume;

[0114] The pressure inside the bubble is calculated from the bubble volume, temperature and mass according to the gas state equation;

[0115] According to the force balance condition inside and outside the bubble in the flow field, the local pressure of the liquid phase outside the bubble is calculated.

[0116] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A method for measuring the instantaneous pressure surface of gas-liquid two-phase flow, characterized in that: The following steps are involved: Obtain bubble state information in the gas-liquid two-phase flow region; Establishing a corresponding relationship between the bubble state information and the pressure inside the bubble; According to the equilibrium condition of the pressure inside the bubble and the corresponding relationship, a mapping relationship between the bubble state information and the liquid phase pressure outside the bubble is obtained; The bubble state information is introduced into the mapping relationship and the corresponding relationship to obtain the pressure inside the bubble and the liquid phase pressure outside the bubble.

2. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 1, characterized in that: The bubble state information includes bubble temperature and bubble volume in the gas-liquid two-phase flow region; Establishing a corresponding relationship between the bubble state information and the pressure inside the bubble includes: The corresponding relationship among the bubble temperature, the bubble volume and the pressure inside the bubble is established.

3. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 2, characterized in that: The bubble volume is calculated by the bubble radius; The establishing the corresponding relationship among the bubble temperature, the bubble volume and the pressure inside the bubble comprises: Obtain the initial state equation of the bubble; The initial state equation is changed to obtain the corresponding relationship among the bubble temperature, the bubble radius, the pressure inside the bubble and the gas mass.

4. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 3, characterized in that: If the gas properties of the bubbles deviate from the gas properties of the ideal gas by more than a preset range, the van der Waals state equation is used as the initial state equation.

5. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 3, characterized in that: The step of obtaining bubble state information in the gas-liquid two-phase flow region includes: Acquiring image information of the gas-liquid two-phase flow region using an image capture device; Acquire the bubble temperature and the bubble radius from the image information; The bubble volume is calculated using the bubble radius.

6. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 2, characterized in that: The step of obtaining a mapping relationship between the bubble state information and the liquid phase pressure outside the bubble according to the equilibrium condition of the pressure inside the bubble and the corresponding relationship includes: Obtaining a calculated relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble; According to the calculation relationship and the corresponding relationship, a mapping relationship between the liquid phase pressure outside the bubble and the bubble temperature and the bubble volume is obtained.

7. The method for measuring the instantaneous pressure surface of gas-liquid two-phase flow according to claim 6, characterized in that: The step of obtaining a calculation relationship between the pressure inside the bubble and the pressure of the liquid phase outside the bubble comprises: The calculation equation between the pressure inside the bubble and the pressure of the liquid phase outside the bubble is established according to a nonlinear partial differential equation, and the calculation relationship is obtained in combination with the correction of the non-equilibrium state.

8. A gas-liquid two-phase flow instantaneous pressure surface measuring instrument, characterized in that: Includes lighting source, experimental flow field device and image capture equipment; The illumination light source is located directly above the experimental flow field device, and the image capture device is located directly below the experimental flow field device; The experimental flow field device is in a transparent state; The image capture device is used to capture image information of the gas-liquid two-phase flow region in the experimental flow field device; The illumination light source is used to provide illumination for the gas-liquid two-phase flow region in the experimental flow field device.

9. The gas-liquid two-phase flow instantaneous pressure surface measuring instrument according to claim 8, characterized in that: The image capturing device includes: an infrared thermal imager and a high-speed camera.

10. The gas-liquid two-phase flow instantaneous pressure surface measuring instrument according to claim 9, characterized in that: It also includes data acquisition equipment; The data acquisition device is connected to the image capturing device for acquiring the image information.

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