Method for testing uniformity of static mixer

Abstract

The invention discloses a method for testing the uniformity of a static mixer, which comprises the following steps of: S1, constructing a test system: selecting at least one test section on a downstream pipeline of a static mixer to be tested along the axial direction, and configuring a sampling pipe array comprising a plurality of spatial sampling points on the section; s2, implementing a multi-working-condition dynamic test: controlling the mixed gas to flow through a mixer and a downstream pipeline in at least three different preset flow working conditions, and synchronously collecting real-time gas samples of all sampling points in the sampling pipe array under each stable flow working condition; s3, data acquisition and processing: analyzing the gas sample acquired at each sampling point to obtain the instantaneous volume concentration of the target component, and generating a space concentration distribution data set corresponding to the test section under each flow working condition; and S4, uniformity calculation: calculating a quantitative index reflecting the concentration uniformity of the cross section, and integrating the uniformity indexes under all test flow working conditions.

Description

Technical Field

[0001] This invention relates to the field of gas mixing technology, and more specifically to a method for testing the uniformity of a static mixer. Background Technology

[0002] Static mixers are widely used in chemical, energy, and environmental protection fields to achieve efficient mixing of two or more fluids. Mixing uniformity is the core indicator for evaluating their performance. Currently, for applications requiring strict mixing uniformity, such as natural gas blending with hydrogen, testing is typically conducted using single-location sampling or limited-point sampling from downstream pipelines. This method has the following problems: 1. Insufficient sampling representativeness: A single or small number of sampling points cannot fully reflect the concentration distribution on the pipe cross-section, which may lead to misjudgment of uniformity.

[0003] 2. Flow field interference: Improper sampling point location (such as near pipe fittings or bends) or the sampling structure itself may interfere with the flow field inside the pipeline, affecting the authenticity of the sampled gas.

[0004] 3. Low testing efficiency: Multi-condition testing requires manual switching and multiple sampling, which is cumbersome and makes it difficult to achieve automation and continuous monitoring.

[0005] 4. Poor data integration: Test data is scattered and lacks systematic analysis and visualization, which is not conducive to the comprehensive evaluation and optimization of mixer performance.

[0006] While existing standards (such as the draft national standard for gas-hydrogen blending devices) set forth basic requirements for uniformity testing, they do not specify concrete, efficient, and reliable testing methods and dedicated equipment. Therefore, developing a method and apparatus capable of comprehensively, accurately, and efficiently testing the uniformity of static mixers has significant engineering value and market demand. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method for testing the uniformity of a static mixer, which aims to overcome at least one related technical problem existing in the background art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for testing the uniformity of a static mixer includes the following steps: S1. Constructing the test system: On the downstream pipe of the static mixer under test, select at least one test section along the axial direction, and configure a sampling tube array containing multiple spatial sampling points on the section. S2. Implement multi-condition dynamic testing: Control the mixed gas to flow through the mixer and downstream pipeline at at least three different preset flow conditions, and simultaneously collect real-time gas samples from all sampling points in the sampling tube array under each stable flow condition. S3. Data Acquisition and Processing: Analyze the gas samples collected at each sampling point to obtain the instantaneous volume concentration of the target components and generate a dataset of spatial concentration distribution corresponding to the test section under each flow condition. S4. Uniformity Calculation: Based on the spatial concentration distribution dataset obtained in step S3, calculate the quantitative index reflecting the uniformity of the concentration in the cross section, and combine the uniformity index under all test flow conditions to make a grade evaluation of the overall mixing performance of the static mixer.

[0009] The technical solution of this application elevates discrete testing operations to a systematic and process-oriented dynamic evaluation method, ensuring the comprehensiveness of the tests and the reliability of the results. Through the framework of "multi-section-multi-condition-synchronous analysis," the actual performance of the mixer under different operating conditions can be more realistically reflected.

[0010] To ensure that the sampling section is located in a fully developed turbulent region, in an optional implementation, in step S1, the test section is located at a distance of not less than 10 times the pipe diameter (10D) downstream of the static mixer outlet.

[0011] In one optional implementation, in step S1, the sampling tube array includes a flange and several independent sampling tubes. The flange is installed on the side of the tee joint opposite to the upstream straight section of the pipe. One end of the sampling tube passes through the flange and the tee and extends into the upstream straight section of the pipe.

[0012] In one optional implementation, in step S1, the number of sampling tubes is 6, and the arrangement is a "1 center point + 5 radial points" pattern, that is, one sampling tube is located at the center of the pipe cross-section, and the other five sampling tubes are located at 1 / 3 of the radius of the pipe cross-section. This arrangement optimizes spatial coverage without excessively increasing complexity.

[0013] In one optional embodiment, the five radial sampling tubes are arranged at azimuth angles of 90°, 135°, 180°, 270°, and 315° along the circumferential direction, respectively. This improves the flexibility and accuracy of the detection.

[0014] In one alternative embodiment, each sampling tube includes an inner sampling tube and an outer protective sleeve fitted over it; the inner sampling tube is a stainless steel capillary tube with an outer diameter not exceeding Φ6mm, used to guide the gas sample.

[0015] In one optional embodiment, the outer protective sleeve is a stainless steel tube with an outer diameter of no more than Φ12mm, and its length extends into the tee but does not exceed it, in order to shield the main airflow from disturbing the capillary sampling.

[0016] In one optional implementation, in step S2, the at least three different preset flow rate conditions are 20%, 50%, and 80% of the design flow rate of the mixing device, respectively. This covers three typical operating conditions—low, medium, and high—and allows for a systematic evaluation of the mixer's mixing performance at different flow rates.

[0017] In one optional implementation, in step S4, the quantitative index is the relative error or standard deviation of the target component concentration at each sampling point; the comprehensive evaluation is: when the index does not exceed the preset threshold under all test conditions, the mixer is judged to be of qualified mixing uniformity.

[0018] In an optional implementation, the method further includes step S5: establishing a performance graph: associating the uniformity index obtained in step S4 under each flow condition with the corresponding flow value, and drawing a "flow-mixing uniformity" performance relationship graph of the static mixer.

[0019] The beneficial effects that the static mixer uniformity test method disclosed in this application may bring include, but are not limited to: 1. Establish a systematic and standardized dynamic testing and evaluation system: Integrate traditional, scattered, and isolated testing operations into a standard process of "system construction - dynamic testing - data processing", ensuring the standardization, repeatability, and comparability of test results, and providing the industry with a unified performance evaluation method.

[0020] 2. Comprehensive and accurate reflection of mixer performance: By setting up a spatial sampling array in the stable flow field region (outside 10D) and conducting tests covering various typical operating conditions (low, medium, and high), the actual mixing capacity of the mixer under different operating conditions can be systematically evaluated, and the test results are comprehensive, accurate, and reliable.

[0021] 3. Significantly improves test accuracy and data representativeness: The optimized sampling point layout of "1 center point + 5 radial points" achieves effective spatial coverage of the pipe cross-section with the most economical number of sampling tubes. In particular, the asymmetrical angle layout can sensitively capture potential concentration unevenness and improve the spatial representativeness of the sampling data.

[0022] 4. Effectively avoid sampling distortion and ensure data authenticity: By setting the sampling point at the end of the straight section of the pipe, 50mm beyond the welding point of the tee, and using a double-layer sleeve sampling pipe structure, the interference of pipe fitting turbulence and high-speed airflow pulsation on the sampling is effectively isolated. Attached Figure Description

[0023] Figure 1 This is a flowchart of the test method for the uniformity of static mixers in this application.

[0024] Figure 2 This is a schematic diagram of a sampling tube array according to an embodiment of this application.

[0025] Figure 3 This is a left view of the sampling tube array according to an embodiment of this application.

[0026] The labels in the diagram are as follows: 1-Tee, 2-Inner sampling tube, 3-Outer protective sleeve, 4-Flange, 5-Valve. Detailed Implementation

[0027] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0028] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0029] like Figure 1-3 As shown, a method for testing the uniformity of a static mixer includes the following steps: S1. Constructing the test system: On the downstream pipe of the static mixer under test, select at least one test section along the axial direction, and configure a sampling tube array containing multiple spatial sampling points on the section. S2. Implement multi-condition dynamic testing: Control the mixed gas to flow through the mixer and downstream pipeline at at least three different preset flow conditions, and simultaneously collect real-time gas samples from all sampling points in the sampling tube array under each stable flow condition. S3. Data Acquisition and Processing: Analyze the gas samples collected at each sampling point to obtain the instantaneous volume concentration of the target components and generate a dataset of spatial concentration distribution corresponding to the test section under each flow condition. S4. Uniformity Calculation: Based on the spatial concentration distribution dataset obtained in step S3, calculate the quantitative index reflecting the uniformity of the concentration in the cross section, and combine the uniformity index under all test flow conditions to make a grade evaluation of the overall mixing performance of the static mixer.

[0030] To transform fragmented and isolated testing operations into a repeatable and comparable systematic evaluation process, and to achieve a comprehensive characterization of mixer performance, this invention summarizes the testing process into four logically rigorous steps: "system construction—dynamic testing—data processing—comprehensive evaluation." This framework ensures the standardization of testing, reveals the mixer's performance under different operating conditions through multi-condition dynamic testing, and overcomes the limitations of single-point and single-condition testing.

[0031] First, a sampling array is installed downstream of the mixer according to standards, forming a complete testing system. Then, the process flow rate is sequentially adjusted to each preset operating point (e.g., 20%, 50%, 80% of design flow rate). After each operating point stabilizes, all sampling points are automatically or manually triggered for synchronous or rapid sequential sampling and analysis. Data measured by analytical instruments (e.g., mass spectrometer, hydrogen analyzer) is transmitted to the processing unit in real time, forming a spatial concentration matrix for each operating point. Finally, the processing unit calculates the uniformity index based on this matrix and compares the index for each operating point with preset thresholds, thereby providing a comprehensive performance evaluation (e.g., qualified / unqualified).

[0032] In some embodiments, in order to ensure that the flow field at the sampling point is fully developed and stable, and to avoid interference from the strong velocity and concentration gradients near the mixer outlet, thereby obtaining true data that can represent the final mixing state, the present invention sets the test section 10D downstream.

[0033] After the fluid exits the mixer, it needs to travel a certain distance to eliminate initial disturbances and reach a stable state where turbulence is fully developed. 10D is the minimum empirical distance to meet this requirement. Sampling at this location results in a stable concentration distribution, and the measurement results are representative and repeatable.

[0034] In some embodiments, in step S1, the sampling tube array includes a flange and several independent sampling tubes. The flange is installed on the side of the tee joint opposite to the upstream straight section of the pipe. One end of the sampling tube passes through the flange and the tee and extends into the upstream straight section of the pipe.

[0035] All sampling points of the array are located on the straight section of the pipe upstream of the tee 1 structure, and the axial distance between the nearest sampling point and the welding point of the tee 1 is not less than 50mm.

[0036] To further eliminate the disturbance of the local flow field at the sampling point by pipe fittings and to provide a clear and uniform sampling termination boundary, while facilitating the installation and operation of the testing device, this invention deploys the sampling array on a straight section of pipe, with the upstream area of ​​the end tee 1 as the boundary, maintaining a safe distance of 50 mm. This ensures that the gas sample taken comes entirely from a direct current field unaffected by the tee 1 structure, and is a well-flowing mixed gas.

[0037] Tee 1, as a standard component of the piping system, is installed at the end of a straight section of pipe. The weld point between Tee 1 and the straight section of pipe forms a clear geometric boundary. Sampling points are required to be located at least 50mm upstream of the tee to avoid the weld heat-affected zone and any potential pre-swirling or separation zones within Tee 1.

[0038] Preferably, in step S1, the number of sampling tubes is 6, and the arrangement is "1 center point + 5 radial points", that is, one sampling tube is located at the center of the pipe cross-section, and the other five sampling tubes are located at 1 / 3 of the radius of the pipe cross-section. This arrangement optimizes spatial coverage without excessively increasing complexity.

[0039] To achieve the most representative spatial coverage of the concentration distribution across a circular pipe cross-section with the most economical number of sampling tubes, while also considering the measurement sensitivity of both the core and annular regions, this invention employs an optimized sampling point layout of "1 center point + 5 radial points." The center point monitors the core flow, while the five points located at one-third of the radius effectively capture the radial concentration gradient. This approach achieves the best balance between cost and accuracy.

[0040] For turbulent mixing within a circular pipe, a concentration gradient often exists radially. The area at one-third of the radius is a typical location where this gradient can be quite significant, making it a highly sensitive location for sampling. The center point serves as the benchmark for evaluating the mixing core effect.

[0041] Of course, it should be noted that the total number of sampling tubes can be increased or decreased depending on the pipe size and accuracy requirements, for example, 4 or 8. The radial position can also be selected as 1 / 2 radius or 2 / 3 radius. The layout can also be in the form of "1 center + multiple concentric rings", etc.

[0042] Each individual sampling tube is also equipped with a valve 5 that can control the opening and closing of the sampling tube individually, which facilitates the independent operation of each sampling tube. For example, gas can be collected into a sampling bag through the sampling tube and then analyzed using a chromatographic column.

[0043] In some embodiments, the five radial sampling tubes are arranged at azimuth angles of 90°, 135°, 180°, 270°, and 315° along the circumferential direction. To effectively detect non-axisymmetric concentration distributions that may be caused by asymmetric internal mixer structures or uneven airflow, and to improve the testing method's ability to capture common non-uniformity patterns, this invention sets the five radial sampling tubes to a specific asymmetric angular distribution (90°, 135°, 180°, 270°, and 315°). This is more revealing of the actual direction of concentration non-uniformity than a completely uniform distribution (e.g., one every 72°).

[0044] Many static mixers (such as helical vane mixers) generate specific asymmetric flow fields. This combination of angles covers the four main quadrants and common asymmetric directions (such as the 135°–315° axis), increasing the probability of detecting local concentration anomalies.

[0045] In some embodiments, each sampling tube includes an inner sampling tube 2 and an outer protective sleeve 3 sleeved thereon; the inner sampling tube 2 is a stainless steel capillary tube with an outer diameter of no more than Φ6mm, used to guide the gas sample; the outer protective sleeve 3 is a stainless steel tube with an outer diameter of no more than Φ12mm, whose length extends into the interior of the tee 1 but does not exceed it, used to shield the main airflow from disturbing the capillary sampling.

[0046] To address the issues of sampling tubes being prone to vibration and breakage in high-speed airflow, and sampling distortion caused by strong pulsations in the main airflow affecting the tube inlet flow field, this invention employs a double-layered sleeve structure with a thinner inner tube and a thicker outer tube for each sampling tube. The inner sampling tube 2 (Φ6) ensures response speed and accuracy; the outer protective sleeve 3 (Φ12) serves as a protective sleeve and fairing, its key function being mechanical reinforcement to prevent flow-induced vibration. Because the inner sampling tube 2 is relatively thin and located at the bend of T-junction 1, it is significantly affected by airflow; therefore, the outer protective sleeve 3 is installed at this location to ensure that the sampling tube is not disturbed by airflow.

[0047] The outer protective sleeve 3 is firmly fixed to the wall of the flange 4, and the inner sampling tube 2 is suspended inside the outer protective sleeve 3. The end of the outer tube does not extend beyond the tee 1 to avoid disturbing the sampling airflow.

[0048] In some embodiments, in step S2, the at least three different preset flow conditions are 20%, 50%, and 80% of the design flow of the mixing device, respectively.

[0049] To systematically evaluate the mixing performance of the mixer under low, medium, and high loads, especially to examine whether insufficient turbulence intensity leads to mixing deterioration at low flow rates, this invention selected three representative operating points—20% (low load), 50% (typical load), and 80% (high load)—for testing. This covers the main operating range of the equipment, and the test conclusions have greater engineering guidance value.

[0050] The mixing effect is strongly correlated with the fluid Reynolds number (Re), and Re is proportional to the flow rate. Testing these three operating points with a large range can examine the sensitivity of the mixer's performance to changes in flow rate.

[0051] In some embodiments, in step S4, the quantitative index is the relative error or standard deviation of the target component concentration at each sampling point; the comprehensive evaluation is: when the index does not exceed a preset threshold (e.g., 5%) under all test conditions, the mixer's mixing uniformity is deemed qualified.

[0052] To transform spatial concentration distribution data into intuitive and quantifiable performance indicators and establish clear pass / fail criteria, this invention uses relative error or standard deviation as a uniformity quantification indicator and sets a unified threshold (e.g., 5%) as a comprehensive evaluation standard. This makes performance evaluation objective, clear, easy to implement, and comparable.

[0053] Relative error (the percentage deviation of each point's concentration from the average concentration) or standard deviation is a classic statistic for measuring the dispersion of data and can effectively characterize the uniformity of concentration. Preset thresholds (such as 5%) are derived from relevant standards or engineering experience and represent a quantitative reflection of performance requirements.

[0054] The method further includes step S5, establishing a performance graph: associating the uniformity index under each flow condition obtained in step S4 with the corresponding flow value, and drawing a "flow-mixing uniformity" performance relationship graph of the static mixer.

[0055] In order to transform the test results of discrete operating points into a continuous and visualized equipment performance model, so that users can quickly query the expected uniformity of the mixer under any operating condition and provide graphical tools for operation optimization and selection, this invention adds the step of establishing a "flow-mixing uniformity" performance graph.

[0056] Plotting flow rate on the x-axis and calculated uniformity indicators (such as standard deviation) on the y-axis, the test results for each operating condition are plotted as points. A trend line can be formed through curve fitting, thus creating a unique performance spectrum for the mixer. The spectrum can be a two-dimensional curve or a data table containing more parameters (such as pressure and blending ratio).

[0057] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for testing the uniformity of a static mixer, characterized in that, Includes the following steps: S1. Constructing the test system: On the downstream pipe of the static mixer under test, select at least one test section along the axial direction, and configure a sampling tube array containing multiple spatial sampling points on the section. S2. Implement multi-condition dynamic testing: Control the mixed gas to flow through the mixer and downstream pipeline at at least three different preset flow conditions, and simultaneously collect real-time gas samples from all sampling points in the sampling tube array under each stable flow condition. S3. Data Acquisition and Processing: Analyze the gas samples collected at each sampling point to obtain the instantaneous volume concentration of the target components and generate a dataset of spatial concentration distribution corresponding to the test section under each flow condition. S4. Uniformity Calculation: Based on the spatial concentration distribution dataset obtained in step S3, calculate the quantitative index reflecting the uniformity of the concentration in the cross section, and combine the uniformity index under all test flow conditions to make a grade evaluation of the overall mixing performance of the static mixer.

2. The method according to claim 1, characterized in that, In step S1, the test section is located at a distance of not less than 10 times the pipe diameter downstream of the static mixer outlet.

3. The method according to claim 2, characterized in that, In step S1, the sampling tube array includes a flange and several independent sampling tubes. The flange is installed on the side of the tee joint opposite to the upstream straight section of the pipe. One end of the sampling tube passes through the flange and the tee and extends into the upstream straight section of the pipe.

4. The method according to claim 3, characterized in that, In step S1, there are 6 sampling tubes, and the arrangement is "1 center point + 5 radial points", that is, one sampling tube is located at the center of the pipe cross-section, and the other five sampling tubes are located at 1 / 3 of the radius of the pipe cross-section.

5. The method according to claim 4, characterized in that, The five radial sampling tubes are arranged at azimuth angles of 90°, 135°, 180°, 270° and 315° along the circumference.

6. The method according to claim 3, characterized in that, Each of the sampling tubes includes an inner sampling tube and an outer protective sleeve; the inner sampling tube is a stainless steel capillary tube used to guide the gas sample.

7. The method according to claim 6, characterized in that, The outer protective sleeve is a stainless steel tube, extending into the tee but not exceeding it, used to shield the main airflow from disturbing the capillary sampling.

8. The method according to claim 1, characterized in that, In step S2, the at least three different preset flow conditions are 20%, 50%, and 80% of the design flow of the mixing device.

9. The method according to claim 1, characterized in that, In step S4, the quantitative index is the relative error or standard deviation of the target component concentration at each sampling point; the comprehensive evaluation is: when the index does not exceed the preset threshold under all test conditions, the mixer is judged to be of qualified mixing uniformity.

10. The method according to claim 1, characterized in that, The method further includes step S5, establishing a performance graph: associating the uniformity index under each flow condition obtained in step S4 with the corresponding flow value, and drawing a "flow-mixing uniformity" performance relationship graph of the static mixer.

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