Volumetric aeration concentration meter calibration device

Abstract

A volumetric aeration concentration meter calibration device comprises a vertically-placed cylindrical mixing barrel, and is further provided with a screw pump, a pump water inlet pipe, a pump water outlet pipe, a jet device and a feeding pipe, and the mixing barrel, the pump water inlet pipe, the screw pump, the pump water outlet pipe, the jet device and the feeding pipe are sequentially connected to form a water circulation loop; an isolation pipe is arranged at the bottom of the mixing cylinder; an air inlet of the jet device is connected with an air inlet pipe, and the air inlet pipe is provided with an adjusting valve used for adjusting the air inlet amount; a graduated scale is arranged on the side face of the mixing barrel and used for measuring the height of the liquid level in the mixing barrel. According to the invention, the aeration water flow with uniform aeration concentration can be generated, the calibration range is wide, and the error source of the calibration value is simple, so that the high-reliability calibration of the aeration concentration meter can be realized.

Description

Technical Field

[0001] This invention belongs to the field of instrument calibration and verification, and specifically relates to a calibration device for a volumetric gas-entrained concentration meter. Background Technology

[0002] Aeration concentration, or gas volume percentage, is a key hydraulic parameter in aerated water flow. In prototype observations and hydraulic model tests of water conservancy projects, resistance-type aeration concentration meters are the primary equipment for measuring this parameter. As a measuring instrument, aeration concentration meters must be calibrated regularly to ensure the accuracy of their measurement results.

[0003] Early calibration methods, limited by technological constraints, primarily relied on Maxwell's theoretical formulas, simulating different gas doping concentrations by adjusting the resistance of a standard resistor. This method was essentially an indirect calculation rather than a direct comparative calibration, resulting in poor accuracy and significant systematic errors in measurement results between different instruments.

[0004] In recent years, comparative calibration methods have gradually developed. In 2019, the China Institute of Water Resources and Hydropower Research designed an aeration concentration calibration device (patent number: ZL201921021352.X), which prepares standard water flows with different aeration concentrations by adjusting the air and water flow rates respectively. However, this method suffers from problems such as uneven spatial distribution of aeration concentration and complex sources of error, affecting the reliability of the calibration results. To solve these problems, the institute proposed a new calibration method and facility in 2023 (patent number: ZL202310584139.4). This facility uses a vertical cylinder, a bubble disc at the bottom of the cylinder, and an air compressor to generate aerated water flow, and calculates the aeration concentration by measuring the change in water level height inside the cylinder before and after aeration. This device has a simple structure and can obtain a relatively uniform aerated water flow. However, its main drawback is the limited calibration range; the upper limit of the standard value for aeration concentration is low, typically only 20%~30%, which is insufficient to meet the calibration requirements of instruments measuring high aeration concentrations, thus limiting its application scope.

[0005] Therefore, there is an urgent need in the field for a gas concentration meter calibration device that can simultaneously achieve uniform gas mixing, simple error sources, and a wide calibration range. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a volumetric gas-entrained concentration meter calibration device. This device can generate a gas-entrained water flow with uniform gas concentration, has a wide calibration range, and the source of error in the calibration value is simple, thereby achieving highly reliable calibration of the gas-entrained concentration meter.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A calibration device for a volumetric gas-entrained concentration meter includes a vertically placed cylindrical mixing cylinder. The lower part of the mixing cylinder is connected to a pump inlet pipe and a feeding pipe. A screw pump, a pump outlet pipe, and an ejector are also provided between the pump inlet pipe and the feeding pipe. The mixing cylinder, the pump inlet pipe, the screw pump, the pump outlet pipe, the ejector, and the feeding pipe are sequentially connected to form a water circulation loop. An isolation pipe is provided at the bottom of the mixing cylinder. The outlet of the feeding pipe is located inside the isolation pipe, and the inlet of the pump inlet pipe is located outside the isolation pipe. An air inlet pipe is connected to the air inlet of the ejector, and a regulating valve for adjusting the air intake is provided on the air inlet pipe. A scale is provided on the side of the mixing cylinder for measuring the liquid level inside the mixing cylinder.

[0008] Furthermore, the scale is fixed vertically along the wall of the mixing cylinder.

[0009] Furthermore, a water valve is installed on the pump inlet pipe.

[0010] Furthermore, the jet injector is located directly below the mixing cylinder.

[0011] The advantages and beneficial effects of this invention are as follows: The jet injector, also known as a Venturi mixer or water jet injector, can automatically draw in air, resulting in highly uniform water-air mixing. In this invention, the drawn-in air is broken into microbubbles by the jet injector and mixed with the water flow. After circulation and balancing, the aerated water flow forms a highly uniform aerated concentration distribution within the mixing cylinder, ensuring the uniformity of the calibration environment. This invention uses a screw pump capable of conveying a two-phase water-air flow to circulate the water-air mixture within the mixing cylinder into the jet injector, allowing the aerated water flow to continuously circulate and aerate, thereby achieving a high aerated concentration, with an upper limit of 80%, ensuring a wide calibration range for the aerated concentration. This invention has a simple structure. By observing the water level in the mixing cylinder before and after aeration, the volume of the un-aerated water (denoted as V1) and the volume of the aerated water flow (denoted as V2) can be obtained. The aeration concentration (denoted as C) can then be calculated using the formula: C = (V2-V1) / V2. This aeration concentration value is the calibration value used for calibrating the aeration concentration meter. The accuracy of the calibration value mainly depends on the measurement accuracy of the volume values ​​of the un-aerated water and the aerated water flow. The source of error is singular and clear. Therefore, the source of error in the calibration value of this invention is simple and easy to trace. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the planar structure of the present invention.

[0013] The labels in the diagram are as follows: 1-mixing cylinder, 2-scale, 3-isolation pipe, 4-pump inlet pipe, 5-feeding pipe, 6-water valve, 7-air inlet pipe, 8-regulating valve, 9-ejector, 10-pump outlet pipe, 11-screw pump. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] like Figure 1 As shown, the present invention provides a volumetric gas-mixing concentration meter calibration device, which mainly consists of a mixing cylinder 1, a scale 2, an ejector 9, a regulating valve 8, a screw pump 11, and other components.

[0016] The mixing cylinder 1 is a vertically placed transparent acrylic cylinder with an inner diameter of 70 mm and a height of 1.6 m. A scale 2 is vertically installed on the cylinder wall of the mixing cylinder 1. The scale 2 is a self-adhesive carbon steel scale strip with a total length of 1.5 m, and the zero mark (measurement starting point) of the scale 2 is located on the bottom surface of the mixing cylinder 1. The cross-section of the mixing cylinder 1 remains constant to ensure a strict linear relationship between the liquid level and volume.

[0017] The lower part of the mixing cylinder 1 is connected to a pump inlet pipe 4 and a feed pipe 5. Between the pump inlet pipe 4 and the feed pipe 5, there is also a screw pump 11, a pump outlet pipe 10, and an ejector 9. All three pipes use 25mm inner diameter silicone steel wire hoses. A water valve 6, a stainless steel double-pagoda ball valve, is installed on the pump inlet pipe 4. The outlet end of the pump inlet pipe 4 is connected to the screw pump 11, which is a 1100W, 25mm diameter stainless steel manual screw self-priming pump. The outlet end of the pump outlet pipe 10 is connected to the ejector 9, which is located directly below the mixing cylinder 1 and is connected to the inlet end of the feed pipe 5. The mixing cylinder 1, pump inlet pipe 4, screw pump 11, pump outlet pipe 10, jet ejector 9 and feed pipe 5 are connected in sequence to form a water circulation loop. Under the power of the screw pump 11, the air-mixed water in the mixing cylinder 1 flows out from the pump inlet pipe 4 and flows back to the mixing cylinder 1 from the feed pipe 5.

[0018] The mixing cylinder 1 has an isolation pipe 3 at its bottom, which is an acrylic tube with an inner diameter of 40 mm and a height of 100 mm. The outlet of the feed pipe 5, located on the bottom surface of the mixing cylinder 1, is inside the isolation pipe 3, while the inlet of the pump inlet pipe 4, located on the lower side of the mixing cylinder 1, is outside the isolation pipe 3. The isolation pipe 3 serves to prevent short-circuiting of the water flow, that is, to prevent the water flowing out of the feed pipe 5 from entering the pump inlet pipe 4 directly without mixing with the water flow inside the mixing cylinder 1.

[0019] The ejector 9 is an SSQ-200 type acrylic water jet ejector with a maximum water flow rate of 2.6 cubic meters per hour. The air intake of the ejector 9 is connected to an 8 mm inner diameter air inlet pipe 7 via a reducing connector. An adjusting valve 8, a WL24H-320P micro-adjustment needle valve, is installed on the air inlet pipe 7 to precisely adjust and control the air flow rate. When the screw pump 11 starts, the water in the mixing cylinder 1 circulates. Due to the water flow, the ejector 9 generates suction, drawing air into it through the air inlet pipe 7 and mixing it with the water to create an aerated water flow.

[0020] In this embodiment, the working steps of the present invention are as follows.

[0021] Step 1: Close water valve 6 and regulating valve 8. Take a certain volume (denoted as V1) of tap water. Measure V1 using a measuring cylinder. Pour the tap water of volume V1 into mixing cylinder 1. Divide the volume V1 by the cross-sectional area S of mixing cylinder 1 to obtain the water depth in mixing cylinder 1 corresponding to volume V1. This water depth is denoted as L1, i.e., L1 = V1 / S.

[0022] Step 2: Fully open water valve 6 and start screw pump 11. The water in mixing cylinder 1 circulates through screw pump 11 and ejector 9. At this time, regulating valve 8 is closed, and no air enters ejector 9. The water in mixing cylinder 1 circulates in multiple components, and the water level in mixing cylinder 1 drops. After the water level stabilizes, read the liquid level from scale 2 and record it as h0.

[0023] Step 3: Open the regulating valve 8, maintaining its opening at a certain position. Air is automatically drawn into the ejector 9, forming an aerated water flow. This aerated water flow circulates and continuously aerates within the device. Once the water-to-air volume ratio within the device reaches equilibrium, the aeration concentration stabilizes, and the liquid level of the water-air mixture in the mixing cylinder 1 no longer changes. At this point, read the liquid level height from the scale 2 and record it as h1. Calculate the change in liquid level height in the mixing cylinder 1 before and after aeration, and record it as h1. ,Right now: = h1 - h0.

[0024] Step 4, the volume of the incorporated gas is denoted as V. 气 , there is: V 气 = ×S; Let the volume of the aerated water flow be V2, then: V2 = L1 + V 气 =( L1+ )×S; Finally, the gas doping concentration C is calculated: C = / ( L1+ This is called the calibration value.

[0025] Step 5: Place the probe of the gas concentration meter to be calibrated in the middle of the water-air mixture in the mixing cylinder, obtain the measured value of the gas concentration meter, compare this measured value with the calibration value, calculate the error of the measured value, and complete one comparison.

[0026] Step 6: Change the opening of regulating valve 8 to alter the air flow rate into ejector 9, thereby changing the gas concentration in mixing cylinder 1. Water valve 6 can also be used for assistance; by changing its opening, the pumping flow rate of screw pump 11 changes, which in turn alters the inlet and outlet pressure difference and air flow rate of ejector 9, thus changing the gas concentration. Repeat steps 3 to 5 to compare the measured values ​​with the calibrated values ​​at different gas concentrations. Analyze these comparison results to complete the calibration of this gas concentration meter.

[0027] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A calibration device for a volumetric gas-mixing concentration meter, comprising a vertically placed cylindrical mixing cylinder, characterized in that, The lower part of the mixing cylinder is connected to a pump inlet pipe and a feeding pipe. A screw pump, a pump outlet pipe, and an ejector are also provided between the pump inlet pipe and the feeding pipe. The mixing cylinder, the pump inlet pipe, the screw pump, the pump outlet pipe, the ejector, and the feeding pipe are connected in sequence to form a water circulation loop. An isolation pipe is provided at the bottom of the mixing cylinder. The outlet of the feeding pipe is located inside the isolation pipe, and the inlet of the pump inlet pipe is located outside the isolation pipe. The air inlet of the ejector is connected to an air inlet pipe, and an adjustment valve for adjusting the air intake is provided on the air inlet pipe. A scale is provided on the side of the mixing cylinder for measuring the liquid level inside the mixing cylinder.

2. The calibration device for a volumetric gas-infused concentration meter according to claim 1, characterized in that, The scale is fixed vertically along the wall of the mixing cylinder.

3. The calibration device for a volumetric gas-infused concentration meter according to claim 1, characterized in that, A water valve is installed on the pump inlet pipe.

4. The calibration device for a volumetric gas-infused concentration meter according to claim 1, characterized in that, The jet injector is located directly below the mixing cylinder.

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