Gas flow device for calibrating critical flow venturi nozzle

Abstract

The utility model relates to a gas flow device for calibrating a critical flow venturi nozzle. The gas flow device comprises a gas storage tank; a critical flow venturi nozzle to be measured; the valve body is provided with a first connector, a second connector, a third connector and a switcher, the switcher can open or close the second connector and the third connector at the same time, meanwhile, the controller controls the timer to conduct timing, the time when gas enters the standard detection container is obtained, and the actual flow of the nozzle can be obtained according to calculation; the outflow coefficient of the nozzle is obtained according to the actual flow and the theoretical flow of the nozzle, so that the actual flow of the critical flow venturi nozzle applied to other environments is calibrated; the standard detection container comprises a plurality of temperature sensors arranged in a shell, the plurality of temperature sensors are uniformly arranged at intervals and can measure a relatively uniform temperature value of the standard detection container, and the fan can stir gas in the standard detection container through rotation, so that the temperature in the standard container is further uniform, and the detection accuracy is improved. And the influence caused by temperature errors is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of flow meter calibration, in particular to a gas flow device for calibrating a critical flow Venturi nozzle. Background Art

[0002] In recent years, with the global shortage of energy resources and the development of science and technology manufacturing industry towards high-precision and cutting-edge fields, the requirements for high-precision flow testing and its measurement technology are getting higher and higher. Critical flow Venturi nozzles are widely used in industrial production, environmental protection, aerospace, automotive engineering, energy industry, medical equipment and other fields due to their simple structure, no moving parts, high flow measurement accuracy, and good long-term stability.

[0003] Working principle of critical flow venturi nozzle: When the gas flows through the nozzle, the flow rate of the gas gradually increases due to the gradual decrease of the inlet aperture, and the pressure of the gas gradually decreases. When the gas reaches the throat, if the pressure difference between the upstream and downstream increases to a certain value (that is, it reaches the critical pressure ratio), the flow rate of the gas will reach the speed of sound, which is called the critical flow state. In the critical flow state, if the upstream pressure (stagnation pressure) remains unchanged and the downstream pressure (back pressure) is reduced, the flow rate of the gas will remain unchanged, that is, it will no longer be affected by the downstream pressure. This is because when the gas flow rate reaches the speed of sound, the interaction force between gas molecules makes it impossible for the gas to accelerate further. In the critical flow state, the mass flow rate of the gas through the nozzle is constant, and it is only related to the upstream pressure (stagnation pressure) and the thermodynamic properties of the gas (such as gas constant, specific heat ratio, etc.), but not to the downstream pressure.

[0004] Since the theoretical flow rate of each critical flow Venturi nozzle can be calculated by its parameters, there is often some error between the theoretical flow rate and the actual flow rate passing through the nozzle. The measurement accuracy of the actual flow rate of the nozzle is very important. However, the calibration device for critical flow Venturi nozzles on the market is complex in structure and low in precision, resulting in varying degrees of measurement errors when critical flow Venturi nozzles are used in different industries.

[0005] Therefore, it is necessary to improve the prior art to overcome the above defects in the prior art. Utility Model Content

[0006] In view of this, the embodiment of the present application provides a gas flow device for calibrating a critical flow venturi nozzle to solve at least one problem in the background technology, including:

[0007] gas tank;

[0008] The critical flow venturi nozzle to be measured is connected to the gas storage tank, and a first stop valve, a first pressure measuring device, and a first temperature measuring device are sequentially arranged between the critical flow venturi nozzle to be measured and the gas storage tank;

[0009] The valve body has a first interface, a second interface, a third interface and a switch, wherein the switch can open or close the first interface, the second interface and the third interface at the same time, the first interface is connected to the critical flow venturi nozzle to be measured, and a second pressure measuring device is further arranged between the first interface and the critical flow venturi nozzle to be measured;

[0010] A standard detection container, the inlet end of which is connected to the second interface, comprises a shell and a temperature sensor and a fan arranged in the shell;

[0011] A signal component, comprising a photoelectric pulse signal converter connected to the third interface and a timer connected to the photoelectric pulse signal converter;

[0012] A controller, connected to the photoelectric pulse signal converter, the timer and the temperature sensor respectively;

[0013] A pressure sensor, connected to the standard test container and the controller respectively, capable of detecting the pressure in the standard test container and feeding back to the controller;

[0014] A vacuum pump is connected to the outlet end of the standard detection container, and a second stop valve is also provided between the vacuum pump and the standard detection container.

[0015] Optionally, in the above-mentioned gas flow device for calibrating a critical flow Venturi nozzle, the gas storage tank has a first preset pressure, and the first preset pressure is 0.4 MPa.

[0016] Optionally, in the above-mentioned gas flow device for calibrating a critical flow Venturi nozzle, at least two temperature sensors are provided, and at least two of the temperature sensors are evenly distributed in the housing.

[0017] Optionally, in the above-mentioned gas flow device for calibrating a critical flow Venturi nozzle, the standard detection container has a second preset pressure, and the second preset pressure ranges from 500Pa to 1000Pa.

[0018] Compared with the prior art, the present application has the following beneficial effects: by sequentially connecting a gas storage tank, a critical flow Venturi nozzle to be measured, a valve body, a standard detection container, a signal component and a controller connected to the signal component, and the valve body includes a first interface, a second interface, a third interface and a switch, the switch can simultaneously open or close the second interface and the third interface, and when the second interface and the third interface are simultaneously opened or closed, the controller controls the timer to time, and obtains the time when the gas enters the standard detection container, and the gas flow in the standard detection container can be obtained according to the calculation, that is, the actual flow through the critical flow Venturi nozzle to be measured, and the outflow coefficient of the critical flow Venturi nozzle can be obtained according to the actual flow and the theoretical flow through the critical flow Venturi nozzle to be measured, so as to calibrate the actual flow of the critical flow Venturi nozzle applied in other environments; and the standard detection container includes a plurality of temperature sensors arranged in the shell, and the plurality of temperature sensors are evenly spaced, so that a relatively uniform temperature value of the standard detection container can be measured, and the influence of the temperature error on the standard detection container can be reduced, and the fan can further uniformize the temperature in the standard container by rotating and stirring the gas in the standard detection container, and further reduce the influence of the temperature error. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a gas flow device for calibrating a critical flow Venturi nozzle as shown in the present application. DETAILED DESCRIPTION

[0020] The exemplary embodiments disclosed in the present application will be described in more detail below. In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features well known in the art are not described; that is, all features of the actual embodiments are not described here, and known functions and structures are not described in detail.

[0021] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present application necessarily has the first element, component, region, layer or part.

[0022] Spatially relative terms such as "under", "beneath", "below", "under", "over", "above", etc., may be used herein for convenience of description to describe the relationship of one element or feature to other elements or features shown in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation shown in the figures.

[0023] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "a", "an" and " / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0024] In order to thoroughly understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below, but in addition to these detailed descriptions, the present application may also have other implementation methods.

[0025] Please refer to Figure 1As shown, the present application discloses a gas flow device for calibrating a critical flow Venturi nozzle, which is used to calibrate the critical flow Venturi nozzle 5. It can also be understood that the device can measure the discharge coefficient of the critical flow Venturi nozzle 5, thereby facilitating the calibration of the actual flow of subsequent different fluids passing through the nozzle 5.

[0026] The device includes a gas storage tank 1, a critical flow venturi nozzle 5 to be measured, a valve body 6, a standard detection container 11, a signal component, a controller 9, a vacuum pump 15 and a second stop valve 14 arranged between the standard detection container 11 and the vacuum pump 15, which are connected in sequence. Among them, gas is stored in the gas storage tank 1, and the gas storage tank 1 has a first preset pressure, and the first preset pressure is 0.4MPa. In this embodiment, the gas in the gas storage tank 1 is air. In other embodiments, the gas in the gas storage tank 1 can also be other gases, such as nitrogen, argon, etc., and the type of calibration gas source is not specifically limited here, depending on the actual situation. The signal component includes a photoelectric pulse signal converter 7 connected to the third interface and a timer 8 connected to the photoelectric pulse signal converter 7; the controller 9 is connected to the photoelectric pulse signal converter 7, the timer 8 and the temperature sensor 12 respectively.

[0027] In an optional embodiment, the valve body 6 has a first interface, a second interface, a third interface and a switch. Among them, the first interface is connected to the critical flow Venturi nozzle 5 to be measured, the second interface is connected to the inlet end of the standard detection container 11, and the third interface is connected to the signal component. The switch can open or close the second interface and the third interface at the same time, so that the signal component can receive the signal at the same time when the second interface is opened or closed, and after transmitting the signal to the controller 9, the controller 9 controls the opening and closing of the timer 8, and then calculates the actual flow through the critical flow Venturi nozzle 5 to be measured through the time when the gas enters the standard detection container 11 and other relevant data. In this embodiment, the valve body 6 is an electric three-way valve that can be switched at high speed and has controllable valve opening, so as to ensure that the critical flow Venturi nozzle 5 is always in a critical state during the switching process of the valve body 6 and can accurately measure the intake time.

[0028] In an optional embodiment, a first stop valve 2, a first pressure measuring device 3, and a first temperature measuring device 4 are sequentially arranged between the critical flow venturi nozzle 5 to be measured and the gas storage tank 1. The first pressure measuring device 3 is used to measure the upstream pressure of the critical flow venturi nozzle 5 to be measured, and the first temperature measuring device 4 is used to measure the upstream temperature of the critical flow venturi nozzle 5 to be measured.

[0029] In an optional embodiment, a second pressure measuring device 16 is further provided between the first interface and the critical flow Venturi nozzle 5 to be measured. The second pressure measuring device 16 is used to measure the downstream pressure of the critical flow Venturi nozzle 5 to be measured, so as to monitor whether the critical flow Venturi nozzle 5 to be measured has reached the stagnation pressure and stagnation temperature.

[0030] In an optional embodiment, the standard detection container 11 includes a shell and a temperature sensor 12 and a fan 13 arranged in the shell. Among them, at least two temperature sensors 12 are provided, and at least two temperature sensors 12 are evenly distributed in the shell. The temperature sensor 12 is used to detect the temperature in the standard detection container 11, and the fan 13 is used to rotate and stir the gas in the standard detection container 11 so that the temperature at various locations in the standard detection container 11 is more uniform. In this embodiment, four temperature sensors 12 are evenly spaced to detect the temperature at various locations in the standard detection container 11. When measuring, the average value of the temperature values ​​at the four locations can be taken as the actual temperature in the standard detection container 11 to reduce the error caused by different temperatures at various locations. It should be noted that in this embodiment, the standard detection container 11 is a container of known volume.

[0031] In an optional embodiment, the standard detection container 11 has a second preset pressure, and the second preset pressure ranges from 500Pa to 1000Pa.

[0032] In an optional embodiment, the device further includes a pressure sensor 10 connected to the standard detection container 11 and the controller 9 respectively. The pressure sensor 10 can detect the pressure in the standard detection container 11 and feed back to the controller 9 .

[0033] In summary, the working process of the gas flow device for calibrating the critical flow Venturi nozzle is:

[0034] (1) Turn on the controller and observe whether the timer, temperature sensor, pressure sensor and other instruments are working properly.

[0035] (2) Open the second stop valve, close the first stop valve and the valve body, start the vacuum pump, and extract the air in the standard test container. When the pressure in the standard test container drops to a second preset pressure value between 500Pa and 1000Pa, close the second stop valve and turn off the vacuum pump.

[0036] (3) Observe whether the state of the air in the standard test container is stable. If the change in the average temperature of the standard test container within a few minutes is small enough and tends to be constant, it means that the state of the air in the standard test container is stable.

[0037] (4) When the state of the air in the standard test container is stable, record the values ​​of the temperature sensor and pressure sensor at this time to obtain the temperature T of the gas in the standard test container before air intake. i and pressure p i .

[0038] (5) Open the first stop valve and the valve body to connect the gas storage tank to the inlet of the standard test container. At the same time, the third interface of the valve body is also opened, and the photoelectric pulse signal converter sends an electrical signal to the controller, which controls the timer to count.

[0039] (6) The air in the air storage tank flows into the standard test container through the critical flow Venturi nozzle to be tested, and the pressure in the standard test container gradually increases. When the ratio of the downstream pressure (the display value of the second pressure measuring device) to the upstream pressure (the display value of the first pressure measuring device) of the critical flow Venturi nozzle to be tested is close to the critical pressure ratio but there is still a margin, the first stop valve and the valve body are closed to stop the air from flowing into the standard test container. At the same time, the third interface is closed, and the photoelectric pulse signal converter sends an electrical signal to the controller. The controller controls the timer to stop timing and obtains the inflation time t.

[0040] (7) When the state of the air in the standard test container is stable, record the values ​​of the temperature sensor and pressure sensor at this time to obtain the temperature T of the gas in the standard test container after air intake. f and pressure p f .

[0041] (8) The actual mass flow rate of the critical flow Venturi nozzle under test is obtained according to the following formula:

[0042]

[0043] Where: q m —The actual mass flow rate of the critical flow Venturi nozzle being measured;

[0044] V—the volume of the standard test container at 293.15K;

[0045] t—the filling time of the standard test container;

[0046] p i —The absolute pressure of the air in the standard test container before filling;

[0047] T i —The absolute temperature of the air in the standard test container before filling;

[0048] p f —The absolute pressure of the air in the standard test container after inflation;

[0049] T f —The absolute temperature of the air in the standard test container after filling;

[0050] P n —absolute pressure of air under standard conditions;

[0051] T n — Temperature of air under standard conditions;

[0052] z i —Gas compressibility coefficient of the air in the standard test container before filling;

[0053] z f —Gas compressibility coefficient of the air in the standard test container after inflation;

[0054] z n —Gas compressibility coefficient of air under standard conditions;

[0055] ρ n —density of air under standard conditions;

[0056] △m—additional mass;

[0057] △t—opening and closing time of valve body;

[0058] α—standard test container material linear expansion coefficient;

[0059] θ—The wall temperature of the standard test container.

[0060] (9) Calculate the theoretical mass flow rate through the critical flow Venturi nozzle under test according to the theoretical calculation formula:

[0061]

[0062] Where: q is the theoretical mass flow rate of the critical flow Venturi nozzle under test;

[0063] A * —Cross-sectional area of ​​the critical flow Venturi nozzle throat under test;

[0064] c * —Critical flow function of the medium passing through the critical flow Venturi nozzle under test;

[0065] p 0 —absolute stagnation pressure upstream of the critical flow Venturi nozzle being measured;

[0066] T 0 —Stagnation temperature upstream of the critical flow Venturi nozzle being measured;

[0067] R—universal gas constant;

[0068] M r —Relative molecular mass of the gas.

[0069] (10) Calculate the discharge coefficient of the critical flow Venturi nozzle under test:

[0070]

[0071] Where: c is the discharge coefficient of the critical flow Venturi nozzle being tested.

[0072] (11) The actual flow rate of other fluids flowing out of the critical flow Venturi nozzle is calculated using this coefficient.

[0073] The above is only a specific implementation of the present application, and any other improvements made based on the concept of the present application are deemed to be within the protection scope of the present application.

Claims

1. A gas flow device for calibrating a critical flow Venturi nozzle, characterized in that: include: gas tank; The critical flow venturi nozzle to be measured is connected to the gas storage tank, and a first stop valve, a first pressure measuring device, and a first temperature measuring device are sequentially arranged between the critical flow venturi nozzle to be measured and the gas storage tank; The valve body has a first interface, a second interface, a third interface and a switch, wherein the switch can open or close the second interface and the third interface at the same time, wherein the first interface is connected to the critical flow venturi nozzle to be measured, and a second pressure measuring device is further provided between the first interface and the critical flow venturi nozzle to be measured; A standard detection container, the inlet end of which is connected to the second interface, comprises a shell and a temperature sensor and a fan arranged in the shell; A signal component, comprising a photoelectric pulse signal converter connected to the third interface and a timer connected to the photoelectric pulse signal converter; A controller, connected to the photoelectric pulse signal converter, the timer and the temperature sensor respectively; A pressure sensor, connected to the standard test container and the controller respectively, capable of detecting the pressure in the standard test container and feeding back to the controller; A vacuum pump is connected to the outlet end of the standard detection container, and a second stop valve is also provided between the vacuum pump and the standard detection container.

2. A gas flow device for calibrating a critical flow Venturi nozzle according to claim 1, characterized in that: The gas storage tank has a first preset pressure, which is 0.4 MPa.

3. A gas flow device for calibrating a critical flow Venturi nozzle according to claim 1, characterized in that: At least two temperature sensors are provided, and at least two temperature sensors are evenly distributed in the shell.

4. A gas flow device for calibrating a critical flow Venturi nozzle according to claim 1, characterized in that: The standard detection container has a second preset pressure, and the second preset pressure ranges from 500Pa to 1000Pa.

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