Device for measuring pressure difference between two-phase flow inlet and outlet of vertical pipeline

Abstract

The utility model relates to the technical field of two-phase flow pressure difference measurement, in particular to a device for measuring the pressure difference between a two-phase flow inlet and a two-phase flow outlet of a vertical pipeline, which mainly comprises a first pressure gauge, a second pressure gauge, a third pressure gauge and a fourth pressure gauge, the second pressure gauge is arranged between the static pressure box and the first pressure gauge and used for measuring the pressure value and correcting the initial inlet pressure value to obtain an actual inlet pressure value; the third pressure gauge is respectively connected with the pipeline and the static pressure box and is used for measuring pressure values of nitrogen with different pressures and an initial outlet pressure value of the liquid to be measured; and the fourth pressure gauge is arranged between the static pressure box and the third pressure gauge and is used for measuring the pressure value and correcting the outlet pressure initial value to obtain an actual outlet pressure value. Therefore, the problem that unnecessary pressure guide pipe heating interference is introduced in an existing measurement mode, so that the two-phase flow void fraction of the vertical pipeline is changed, and uncertain system errors are additionally introduced is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of two-phase flow pressure difference measurement, in particular to a device for measuring the pressure difference between an inlet and outlet of a two-phase flow in a vertical pipeline. Background Art

[0002] like Figure 1 As shown, at present, the inlet and outlet pressures of vertical pipelines are generally measured by differential pressure transmitters. Differential pressure transmitters are a measuring instrument specially used to measure pressure differences. They have the advantage of high precision and are generally used to measure the pressure loss of two-phase flow in horizontal pipelines.

[0003] Compared with horizontal pipelines, the flow pressure difference of vertical pipelines is more complicated, generally consisting of three parts, namely: the pressure loss DP caused by friction resistance f , the pressure difference DP generated by the liquid gravity g and accelerated pressure drop DP a Generally, for two-phase flow, especially two-phase flow with low dryness (cavitation rate), the pressure difference DP generated by gravity g It accounts for a very important part, or even the main part, of the total pressure difference DP. Figure 1 The method requires ensuring that there is no liquid column in the upper and lower pressure pipes, otherwise the liquid column will produce additional pressure difference due to gravity, resulting in huge errors in the measurement results.

[0004] In order to avoid this problem, researchers usually heat the upper and lower pressure pipes. Under heating conditions, once the liquid column exists, it will quickly absorb heat and vaporize, thus ensuring that the pressure pipes are full of gas. This method cleverly avoids the influence of the liquid column in the pressure pipe, but there are also the following three problems:

[0005] First, the pressure-inducing pipe itself has a certain diameter. If the pipe to be measured is of the same diameter as the pressure-inducing pipe, the presence of the pressure-inducing pipe will cause the flow field to change compared to the case without the pressure-inducing pipe. That is, the measuring device itself interferes with the internal flow characteristics of the object being measured. The closer the diameter of the pressure-inducing pipe is to the diameter of the measuring pipe, the greater the interference. This error is a systematic error and is difficult to correct and eliminate theoretically.

[0006] Second, the method of heating the lead-in pipe by wrapping a heating wire around it to ensure the evaporation of the liquid will bring additional heat flow. Once the system is in a stable operating state, the heating wire needs to continue to heat the lead-in pipe, and this part of the heat will eventually be transferred to the flowing fluid. As a result, the measurement method will affect the operating state of the object being measured.

[0007] Third, the pressure-inducing tube is not a transparent tube, so it is difficult to observe the liquid state inside the pressure-inducing tube, and the heat of the heating wire outside the pressure-inducing tube is not easy to control. Too little heating will cause the liquid to affect the pressure difference measurement accuracy, and too much heating will cause excessive additional heat input. According to the analysis of the second item, it will eventually affect the measurement of heat flux density and affect the flow and heat transfer characteristics in the vertical tube. Summary of the invention

[0008] The utility model provides a device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline, so as to solve the problem that the existing measurement method introduces unnecessary interference of heating of the pressure-inducing pipe, causes the cavitation rate of the two-phase flow in the vertical pipeline to change, causes system error and reduces the measurement accuracy.

[0009] The utility model provides a device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline, comprising:

[0010] A static pressure box, the static pressure box is connected to a target high-pressure gas cylinder to obtain nitrogen at multiple different pressures;

[0011] a first pressure gauge, one end of which is connected to the inlet end of the target vertical pipeline, a first valve is arranged between the first pressure gauge and the target vertical pipeline, and the other end of the first pressure gauge is connected to the static pressure box to respectively measure the first pressure value of nitrogen at different pressures and the initial inlet pressure value of the liquid to be measured;

[0012] a second pressure gauge, wherein the second pressure gauge is disposed between the static pressure box and the first pressure gauge, and a second valve is disposed between the second pressure gauge and the first pressure gauge to measure a second pressure value of nitrogen with different pressures to determine an inlet horizontal installation error of the first pressure gauge, and the inlet horizontal installation error is used to correct the initial inlet pressure value to obtain an inlet pressure value;

[0013] a third pressure gauge, one end of which is connected to the outlet end of the target vertical pipeline, a third valve is provided between the third pressure gauge and the target vertical pipeline, and the other end of which is connected to the static pressure box to measure third pressure values ​​of nitrogen gas at different pressures and an initial value of the outlet pressure of the liquid to be measured;

[0014] A fourth pressure gauge is arranged between the static pressure box and the third pressure gauge, and a fourth valve is arranged between the fourth pressure gauge and the third pressure gauge to measure a fourth pressure value of nitrogen at different pressures to determine an outlet horizontal installation error of the third pressure gauge, and the outlet horizontal installation error is used to correct the initial value of the outlet pressure to obtain an outlet pressure value.

[0015] Optionally, the first pressure gauge is fixed between the inlet end of the target vertical pipeline and the static pressure box through a first drainage tube, and the first pressure gauge is perpendicular to the target vertical pipeline and the static pressure box; the third pressure gauge is fixed between the outlet end of the target vertical pipeline and the static pressure box through a second drainage tube, and the third pressure gauge is perpendicular to the target vertical pipeline and the static pressure box.

[0016] Optionally, the first valve and the second valve are arranged on the first drainage tube, and the third valve and the fourth valve are arranged on the second drainage tube.

[0017] Optionally, the first drainage tube and the second drainage tube are made of the same material and have the same size.

[0018] Optionally, the second pressure gauge is disposed on the first drainage tube, and the second pressure gauge is installed vertically.

[0019] Optionally, the fourth pressure gauge is disposed on the second drainage pipe, and the fourth pressure gauge is installed vertically.

[0020] Optionally, the distance between the second pressure gauge and the first pressure gauge is the same as the distance between the fourth pressure gauge and the third pressure gauge.

[0021] Optionally, the first pressure gauge, the second pressure gauge, the third pressure gauge and the fourth pressure gauge are at least one of an electronic diffused silicon pressure gauge or a mechanical pointer pressure gauge.

[0022] The utility model proposes a measuring device for the inlet and outlet pressure difference of two-phase flow in a vertical pipeline. Since the pressure-inlet pipe of the horizontally installed pressure gauge is completely horizontal with the ground, there is no height difference between the position of the pressure gauge and the position of the measuring point. Even if there is liquid, the gravity pressure difference is 0, there is no systematic error, and the accuracy of the measurement result is improved; with the introduction of the measuring device, the volume of the pressure-inlet pipe is shortened by more than 98%, which is almost negligible and has basically no effect on the flow field; there is no need to use an electric heating wire, no additional energy input, and does not affect the dryness and cavitation rate of the liquid to be measured; the measuring device is simple and does not affect the flow field itself, which is of great significance for improving the measurement accuracy of the inlet and outlet pressure difference of the two-phase flow flowing in the vertical pipe.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will become apparent from the following description or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 It is a structural schematic diagram of an existing vertical pipeline two-phase flow pressure difference measuring device;

[0026] Figure 2 The present invention is a schematic structural diagram of a device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline provided by the present invention.

[0027] Description of reference numerals:

[0028] 201 - static pressure box, 202 - first pressure gauge, 203 - second pressure gauge, 204 - third pressure gauge, 205 - fourth pressure gauge, 206 - first valve, 207 - second valve, 208 - third valve and 209 - fourth valve. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0030] The following describes a device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to an embodiment of the utility model with reference to the accompanying drawings. With respect to the existing device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline mentioned in the background technology center, the volume of the pressure pipe cannot be ignored, which will interfere with the flow field. The electric heating wire generates gas when heated, which affects the state of the measured object such as the dryness and cavitation rate. There is a liquid column in the pressure pipe, which brings about system errors and affects the measurement accuracy. The utility model provides a new device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline. In the device, the volume of the pressure pipe is shortened, the liquid column can be ignored, and no electric heating wire is required. Thus, the problem that the existing measurement method introduces unnecessary heating interference of the pressure pipe, which causes the cavitation rate of the two-phase flow in the vertical pipeline to change, causing system errors and reducing the measurement accuracy is solved.

[0031] Specifically, Figure 2 The utility model provides a structural schematic diagram of a device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline.

[0032] like Figure 2 As shown, the measuring device 20 for the inlet and outlet pressure difference of two-phase flow in a vertical pipeline includes: a static pressure box 201, a first pressure gauge 202, a second pressure gauge 203, a third pressure gauge 204 and a fourth pressure gauge 205.

[0033] It should be noted that since different pressure gauges may have zero point differences and measurement inconsistencies (for example, for a standard pressure of 1 MPa, different pressure gauges may have errors and the pressure gauge readings need to be corrected), a high-precision piston pressure calibration instrument must be used before installation to calibrate the first pressure gauge 202, the second pressure gauge 203, the third pressure gauge 204 and the fourth pressure gauge 205 respectively, to obtain correction curves of the four pressure gauges relative to the standard pressure, thereby ensuring the measurement accuracy of the pressure gauges themselves.

[0034] Among them, the static pressure box 201 is connected to the target high-pressure gas cylinder to obtain nitrogen of multiple different pressures. One end of the first pressure gauge 202 is connected to the inlet end of the target vertical pipeline, and a first valve 206 is set between the first pressure gauge 202 and the target vertical pipeline. The other end of the first pressure gauge 202 is connected to the static pressure box 201 to respectively measure the first pressure value of nitrogen of different pressures and the initial inlet pressure value of the liquid to be measured. The second pressure gauge 203 is set between the static pressure box 201 and the first pressure gauge 202, and a second valve 207 is set between the second pressure gauge 203 and the first pressure gauge 202 to measure the second pressure value of nitrogen of different pressures to determine the inlet horizontal installation error of the first pressure gauge 202, and use the inlet horizontal installation error to correct the initial inlet pressure value to obtain the inlet pressure value. One end of the third pressure gauge 204 is connected to the outlet end of the target vertical pipeline, a third valve 208 is arranged between the third pressure gauge 204 and the target vertical pipeline, and the other end of the third pressure gauge 204 is connected to the static pressure box 201 to measure the third pressure value of nitrogen gas at different pressures and the initial value of the outlet pressure of the liquid to be measured. The fourth pressure gauge 205 is arranged between the static pressure box 201 and the third pressure gauge 204, and a fourth valve 209 is arranged between the fourth pressure gauge 205 and the third pressure gauge 204 to measure the fourth pressure value of nitrogen gas at different pressures to determine the outlet horizontal installation error of the third pressure gauge, and use the outlet horizontal installation error to correct the initial value of the outlet pressure to obtain the outlet pressure value.

[0035] In the actual implementation process, the static pressure box 201 is connected to a preset high-pressure gas cylinder, and a pressure reducing valve is provided between the preset high-pressure gas cylinder and the static pressure box 201. The pressure of the static pressure box 201 is controlled by the pressure reducing valve, so that the static pressure box 201 can obtain nitrogen of multiple different pressures from the preset high-pressure gas cylinder.

[0036] It should be noted that the first pressure gauge 202, the second pressure gauge 203, the third pressure gauge 204 and the fourth pressure gauge 205 can be made of electronic diffused silicon pressure sensors, mechanical pointer pressure gauges, etc. Among them, the error caused by the installation direction of the electronic diffused silicon pressure sensor is small and can be ignored. Therefore, in actual operation, it is recommended to use electronic diffused silicon pressure sensors, and mechanical pointer pressure gauges are not recommended, because horizontal installation will cause large installation errors to the measurement results of the mechanical pointer pressure gauge due to the gravity of the pointer. However, those skilled in the art can make targeted choices based on actual conditions, and no specific limitations are made here.

[0037] In some embodiments, the first pressure gauge 202 is fixed between the inlet end of the target vertical pipeline and the static pressure box 201 through a first pressure-conducting pipe, and is perpendicular to the target vertical pipeline and the static pressure box 201; the third pressure gauge 204 is fixed between the outlet end of the target vertical pipeline and the static pressure box 201 through a second pressure-conducting pipe, and is perpendicular to the target vertical pipeline and the static pressure box 201.

[0038] In the actual execution process, the inlet end of the target vertical pipeline is connected to the static pressure box 201 through the first pressure-leading pipe, the first pressure gauge 202 is arranged on the first pressure-leading pipe, and the first valve 206 and the second valve 207 are respectively arranged on both sides of the first pressure gauge 202, so as to ensure that the process of correcting the first pressure gauge 202 is independent of measuring the initial inlet pressure value of the liquid to be tested, and the first pressure value and the initial inlet pressure value of nitrogen under different pressures are measured respectively; the inlet end of the target vertical pipeline is also connected to the static pressure box 201 through the second pressure-leading pipe, the third pressure gauge 204 is arranged on the second pressure-leading pipe, and the third valve 208 and the fourth valve 209 are respectively arranged on both sides of the third pressure gauge 204, so as to ensure that the process of correcting the third pressure gauge 204 is independent of measuring the initial outlet pressure value of the liquid to be tested, and the third pressure value and the initial outlet pressure value of nitrogen under different pressures are measured respectively.

[0039] It should be noted that the materials and dimensions of the first pressure-inducing tube and the second pressure-inducing tube must be the same to ensure that the measured pressure value is not affected.

[0040] In some embodiments, the second pressure gauge 203 is arranged on the first pressure pipe, and the second pressure gauge 203 is installed vertically, that is, parallel to the flow pipe; the fourth pressure gauge 205 is arranged on the second pressure pipe, and the fourth pressure gauge 205 is installed vertically, that is, parallel to the flow pipe.

[0041] In the actual implementation process, the standard method of using the pressure gauge is to install it vertically. Therefore, the horizontal installation of the first pressure gauge 202 and the third pressure gauge 204 will inevitably cause certain errors. Therefore, the embodiment of the utility model vertically sets the second pressure gauge 203 on the first pressure-conducting pipe, and the second pressure gauge 203 is located between the second valve 207 and the static pressure box 201, so as to measure the true inlet pressure value of nitrogen at different pressures, that is, the second pressure value, and use the second pressure value to judge the inlet horizontal installation error value carried by the first pressure value measured by the first pressure gauge 202; the embodiment of the utility model vertically sets the fourth pressure gauge 205 on the second pressure-conducting pipe, and the fourth pressure gauge 205 is located between the fourth valve 209 and the static pressure box 201, so as to measure the true outlet pressure value of nitrogen at different pressures, that is, the fourth pressure value, and use the fourth pressure value to judge the outlet horizontal installation error value carried by the third pressure value measured by the third pressure gauge 204.

[0042] Further, after determining the error values ​​of the first pressure gauge 202 and the third pressure gauge 204, the first valve 206 and the third valve 208 that were closed during the correction of the first pressure gauge 202 and the third pressure gauge 204 are opened, and the opened second valve 207 and the fourth valve 209 are closed, and the two-phase flow inlet and outlet pressure difference measurement process is started, the liquid to be measured is introduced into the target vertical pipeline, the first pressure gauge 202 measures the initial inlet pressure value, the third pressure gauge 204 measures the initial outlet pressure value, the initial inlet pressure value is corrected by the inlet horizontal installation error to obtain the actual inlet pressure value, the initial outlet pressure value is corrected according to the outlet horizontal installation error to obtain the actual outlet pressure value, and finally the inlet and outlet pressure difference of the liquid to be measured can be obtained according to the actual outlet pressure value and the actual inlet pressure value.

[0043] In some embodiments, the distance between the second pressure gauge 203 and the plenum tank 201 is the same as the distance between the fourth pressure gauge 205 and the plenum tank 201 .

[0044] It can be understood that the distance between the second pressure gauge 203 and the static pressure box 201 is the same as the distance between the fourth pressure gauge 205 and the static pressure box 201, which can ensure that the measured gas capacity is the same and the measurement time is equal, thereby achieving a higher accuracy of the measured pressure value.

[0045] The working principle of the device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline proposed by the utility model is described in detail below.

[0046] Close the first valve 206 and the third valve 208, open the second valve 207 and the fourth valve 209, and pass nitrogen of multiple different pressures from the static pressure box 201 to the first pressure gauge 202, the second pressure gauge 203, the third pressure gauge 204 and the fourth pressure gauge 205, and the four pressure gauges respectively obtain the first pressure value, the second pressure value, the third pressure value and the fourth pressure value under the nitrogen of different pressures, and determine the inlet horizontal installation error of the first pressure gauge 202 according to the first pressure value and the second pressure value, and determine the outlet horizontal installation error of the third pressure gauge 204 according to the third pressure value and the fourth pressure value;

[0047] Open the first valve 206 and the third valve 208, close the second valve 207 and the fourth valve 209, and introduce the liquid to be tested into the target vertical pipeline. The first pressure gauge 202 measures the initial inlet pressure value, and the third pressure gauge 204 measures the initial outlet pressure value. The initial inlet pressure value is corrected using the inlet horizontal installation error to generate an actual inlet pressure value. The initial outlet pressure value is corrected using the outlet horizontal installation error to generate an actual outlet pressure value. The actual outlet pressure value is subtracted from the actual inlet pressure value to obtain the inlet and outlet pressure difference of the liquid to be tested.

[0048] The device for measuring the pressure difference between the inlet and outlet of two-phase flow in a vertical pipeline proposed by the utility model has the following beneficial effects:

[0049] (1) Since the pressure pipe of the horizontally installed pressure gauge is completely horizontal with the ground, there is no height difference between the pressure gauge and the measuring point. Even if there is liquid, the gravity pressure difference is 0, and there is no systematic error, which improves the accuracy of the measurement results.

[0050] (2) With the introduction of this measuring device, the volume of the pressure lead pipe is shortened by more than 98%, which is almost negligible and has little effect on the flow field;

[0051] (3) No need to use electric heating wire, no additional energy input, and no impact on the dryness and cavitation rate of the liquid to be tested;

[0052] (4) The measuring device is simple and does not affect the flow field itself, which is of great significance for improving the measurement accuracy of the inlet and outlet pressure difference of two-phase flow in a vertical pipe.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0054] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A device for measuring the pressure difference between the inlet and outlet of a two-phase flow in a vertical pipeline, characterized in that: include: A static pressure box, the static pressure box is connected to a target high-pressure gas cylinder to obtain nitrogen at multiple different pressures; a first pressure gauge, one end of which is connected to the inlet end of the target vertical pipeline, a first valve is arranged between the first pressure gauge and the target vertical pipeline, and the other end of the first pressure gauge is connected to the static pressure box to respectively measure the first pressure value of nitrogen at different pressures and the initial inlet pressure value of the liquid to be measured; a second pressure gauge, wherein the second pressure gauge is disposed between the static pressure box and the first pressure gauge, and a second valve is disposed between the second pressure gauge and the first pressure gauge to measure a second pressure value of nitrogen with different pressures to determine an inlet horizontal installation error of the first pressure gauge, and the inlet horizontal installation error is used to correct the initial inlet pressure value to obtain an inlet pressure value; a third pressure gauge, one end of which is connected to the outlet end of the target vertical pipeline, a third valve is provided between the third pressure gauge and the target vertical pipeline, and the other end of which is connected to the static pressure box to measure third pressure values ​​of nitrogen gas at different pressures and an initial value of the outlet pressure of the liquid to be measured; A fourth pressure gauge is arranged between the static pressure box and the third pressure gauge, and a fourth valve is arranged between the fourth pressure gauge and the third pressure gauge to measure a fourth pressure value of nitrogen at different pressures to determine an outlet horizontal installation error of the third pressure gauge, and the outlet horizontal installation error is used to correct the initial value of the outlet pressure to obtain an outlet pressure value.

2. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 1, characterized in that: The first pressure gauge is fixed between the inlet end of the target vertical pipeline and the static pressure box through a first drainage pipe, and the first pressure gauge is perpendicular to the target vertical pipeline and the static pressure box; The third pressure gauge is fixed between the outlet end of the target vertical pipeline and the static pressure box through the second drainage pipe, and the third pressure gauge is perpendicular to the target vertical pipeline and the static pressure box.

3. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 2, characterized in that: The first valve and the second valve are arranged on the first drainage tube, and the third valve and the fourth valve are arranged on the second drainage tube.

4. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 2, characterized in that: The first drainage tube and the second drainage tube are made of the same material and have the same size.

5. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 2, characterized in that: The second pressure gauge is disposed on the first drainage pipe, and the second pressure gauge is installed vertically.

6. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 5, characterized in that: The fourth pressure gauge is disposed on the second drainage pipe, and the fourth pressure gauge is installed vertically.

7. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 6, characterized in that: The distance between the second pressure gauge and the first pressure gauge is the same as the distance between the fourth pressure gauge and the third pressure gauge.

8. The device for measuring the inlet and outlet pressure difference of two-phase flow in a vertical pipeline according to claim 1, characterized in that: The first pressure gauge, the second pressure gauge, the third pressure gauge and the fourth pressure gauge are at least one of an electronic diffused silicon pressure gauge and a mechanical pointer pressure gauge.

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