Method for measuring flow rate of ventilator using nozzles of different sizes

Abstract

The application provides a method for measuring flow of different size nozzles of a ventilator, in order to meet the test of complete performance curve of a small ventilator which has a relatively wide flow range, a small pressure rise and often needs to run in a small flow range, two nozzles with different throat diameters are used to test the performance curve of a ventilator respectively, then the test results of the two curves are considered together to fit a complete aerodynamic performance curve. The method can overcome the defects of the prior art, i.e. the single fixed diameter nozzle flow measuring device cannot meet the test requirements of the same ventilator with a wide flow range, and the test precision is difficult to meet the application requirements.

Description

Technical Field

[0001] This invention relates to the field of ventilation fan performance testing technology, and specifically to a method for measuring the flow rate of a ventilation fan using nozzles of different sizes. Background Technology

[0002] Industrial ventilators typically achieve an energy efficiency ratio of over 80% and are widely used in metallurgy, petrochemicals, wind tunnels, aerospace, and other industrial fields. Aerodynamic performance testing of ventilators follows the standard GB / T1236-2017, "Performance Testing of Standardized Air Ducts for Industrial Ventilators." In the laboratory, the commonly used flow measurement device is the end-face nozzle, i.e., an inlet conical or arc-shaped nozzle with different throat diameters. When the nozzle throat diameter d ≤ 500 mm, the Reynolds number range corresponding to its composite flow coefficient is: 20000 < Re < 200000.

[0003] Once the fan is manufactured, its aerodynamic performance is determined. Based on its design flow rate, and in accordance with the GB / T1236-2017 standard, a suitable end-face nozzle is selected for performance testing. Under normal circumstances, a complete performance curve test from maximum flow rate to minimum flow rate can be completed.

[0004] For small ventilators with a wide flow range, small pressure rise, and frequent operation in low flow ranges, a single fixed-diameter nozzle flow measurement device cannot meet the testing requirements due to the large range of flow variation. Furthermore, the test accuracy is difficult to achieve the application requirements. Selecting a single end-face nozzle may result in a Reynolds number exceeding its application range. In this case, because the nozzle loss accounts for a large proportion of the total fan pressure, the accuracy of the measurement results is severely affected. If the Reynolds number exceeds the upper limit, the measurement error at the maximum flow point increases; if it exceeds the lower limit, the measurement error at the minimum flow point increases.

[0005] Because the testing standards for ventilation fans have strict requirements for measurement error, the single fixed-diameter nozzle flow measurement device used in the testing standards cannot simultaneously meet the error requirements of the maximum and minimum flow points for small ventilation fans with a relatively wide flow range. Therefore, its reliability cannot meet the requirements of on-site ventilation fan applications.

[0006] Currently, the main types of tests for model-level flow measurement of ventilation fans are as follows:

[0007] Flow measurement and throttling elements are installed in the pipeline, such as classic Venturi tubes, Venturi nozzles, in-pipe nozzles, orifice plates, etc., to test the thermal performance parameters before and after the pipeline and obtain the flow rate value.

[0008] For inlet and outlet air tests and inlet air tests, inlet end face nozzles (or inlet collectors) are often used, installed on the inlet pipe, and the flow rate is obtained by testing the thermal performance parameters before and after the inlet end face nozzle. For outlet air tests, outlet cone valves or butterfly valves are often used, installed on the outlet pipe, and the flow rate is obtained by testing the thermal performance parameters before and after the outlet cone valve or butterfly valve.

[0009] According to standards, various types of flow measurement devices and methods have their applicable ranges. For example, the classic Venturi tube is easily affected by roughness and Reynolds number limitations; the nozzle inside the pipe is easily affected by pipe diameter and Reynolds number limitations. These factors will lead to a relatively small range of flow measurement variation. For fixed test benches, when developing new model machines to meet the requirements of a wide flow range, small pressure rise, and frequent operation in the small flow range of small fans, a single fixed diameter nozzle flow measurement device cannot meet the test requirements of a wide flow variation range for the same fan, and the test accuracy is difficult to meet the application requirements. Summary of the Invention

[0010] Therefore, the present invention provides a method for measuring the flow rate of a ventilator using nozzles of different sizes, which can overcome the shortcomings of the prior art where a single fixed-diameter nozzle flow measurement device cannot meet the testing requirements of a wide range of flow rate variations for small ventilators that often need to operate in a low flow rate range, and the test accuracy is difficult to meet the application requirements.

[0011] To address the above problems, this invention provides a method for measuring flow rate using nozzles of different sizes for a ventilation fan, comprising:

[0012] Step 1: Based on the design parameters of the ventilator, obtain the first end face nozzle with a diameter of D1;

[0013] Step 2: Based on the "Performance Test of Standardized Ducts for Industrial Fans GB / T1236-2017" (hereinafter referred to as the standard) and the parameters of the first end face nozzle, test and calculate the composite coefficient and Reynolds number of each measurement point of the fan, and plot the first performance curve;

[0014] Step 3: Compare each measurement point of the first performance curve with the relationship curve between the composite coefficient and the Reynolds number specified in the standard;

[0015] a. If the Reynolds number corresponding to the maximum flow point of the ventilator exceeds the upper limit, the diameter of the first nozzle is increased to obtain a second end face nozzle with a diameter of D2, and then the aerodynamic performance test is performed to obtain a second performance curve, where D2>D1;

[0016] b. If the Reynolds number corresponding to a detection point before the minimum flow rate point of the ventilator exceeds the lower limit, then the diameter of the first nozzle is reduced to obtain a third end-face nozzle with a diameter of D3. Then, aerodynamic performance testing is performed to obtain a third performance curve, where D3... <D1;

[0017] Step 4: Fit the first performance curve with the second performance curve, or fit the first performance curve with the third performance curve, to form the complete aerodynamic performance curve of the ventilator.

[0018] In some implementations, the end-face nozzle is arc-shaped or conical.

[0019] In some embodiments, the curve fitting process in step four includes selecting the area near the high-efficiency point within the overlapping flow range of the two curves, using the same flow point as a reference point, taking different flow range curves measured by nozzles with different diameters, and fitting the two different flow range curves into a complete aerodynamic performance curve.

[0020] This invention provides a method for measuring the flow rate of a ventilation fan using nozzles of different sizes. By changing the end-face nozzles with different orifice ratios, it enables performance testing of small ventilation fans with a relatively wide flow range, small pressure rise, and frequent operation in the low flow range. While meeting testing standards, it satisfies both the maximum and minimum flow rate testing requirements, while also meeting the accuracy or design requirements of the testing standards. Attached Figure Description

[0021] Figure 1 The fitted flow-pressure performance curve of the ventilation fan is shown in the embodiment of the present invention, which is a method for measuring the flow rate of a ventilation fan using nozzles of different sizes.

[0022] Figure 2 The graph shows the relationship between the composite coefficient and the Reynolds number in GB / T1236-2017, which describes the method for measuring the flow rate of a ventilator using nozzles of different sizes, according to an embodiment of the present invention.

[0023] Figure 3 Performance testing of a large-nozzle axial flow fan using a method for measuring flow rate with nozzles of different sizes, as described in an embodiment of the present invention.

[0024] Figure 4 The flow-pressure performance curve of the large nozzle in the method for measuring flow rate of a ventilator using nozzles of different sizes, as described in this embodiment of the invention;

[0025] Figure 5 This invention relates to a method for measuring the flow rate of a ventilator using nozzles of different sizes, specifically a performance test of a small-nozzle axial flow ventilator.

[0026] Figure 6The flow-pressure performance curves measured by the small nozzle of the method for measuring the flow rate of a ventilator using nozzles of different sizes, as described in this embodiment of the invention. Detailed Implementation

[0027] See also Figures 1 to 6 As shown, according to an embodiment of the present invention, a method for measuring the flow rate of a ventilator using nozzles of different sizes is provided, comprising:

[0028] Step 1: Based on the design parameters of the ventilator, obtain the first end face nozzle with a diameter of D1.

[0029] Step 2: Based on the "Standardized Air Duct Performance Test for Industrial Ventilation Fans GB / T1236-2017" (hereinafter referred to as the standard) and the parameters of the first end face nozzle, test and calculate the composite coefficient and Reynolds number of each measurement point of the ventilation fan, and plot the first performance curve.

[0030] Step 3: Compare each measurement point of the first performance curve with the relationship curve between the composite coefficient and the Reynolds number specified in the standard:

[0031] a. If the Reynolds number corresponding to the maximum flow point of the ventilator exceeds the upper limit, the diameter of the first nozzle is increased to obtain a second end-face nozzle with a diameter of D2, and then the aerodynamic performance is tested to obtain a second performance curve, where D2>D1.

[0032] b. If the Reynolds number corresponding to a detection point before the minimum flow rate point of the ventilator exceeds the lower limit, then the diameter of the first nozzle is reduced to obtain a third end-face nozzle with a diameter of D3. Then, aerodynamic performance testing is performed to obtain a third performance curve, where D3... <D1。

[0033] Step 4: Fit the first performance curve with the second performance curve, or fit the first performance curve with the third performance curve, to form the complete aerodynamic performance curve of the ventilator.

[0034] Specifically, step three also includes determining that if the Reynolds number corresponding to the maximum flow rate point and the minimum flow rate point both exceed the range specified in the standard, the first end face nozzle diameter is incorrectly calculated and needs to be recalculated before proceeding with subsequent steps.

[0035] In one specific embodiment, the end-face nozzle is arc-shaped or conical.

[0036] Specifically, the end face nozzle includes a first end face nozzle, a second end face nozzle, and a third end face nozzle.

[0037] In a specific embodiment, the curve fitting process in step four includes selecting the area near the high-efficiency point within the overlapping flow range of the two curves, using the same flow point as a reference point, taking different flow range curves measured by nozzles with different diameters, and fitting the two different flow range curves into a complete aerodynamic performance curve.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for measuring flow rate of a ventilator using nozzles of different sizes, characterized in that, include: Step 1: Based on the design parameters of the ventilator, obtain the first end face nozzle with a diameter of D1; Step 2: Based on the "Standardized Air Duct Performance Test for Industrial Ventilation Fans GB / T1236-2017" and the parameters of the first end face nozzle, test and calculate the composite coefficient and Reynolds number of each measurement point of the ventilation fan, and plot the first performance curve. Specifically, the first performance curve is the flow and pressure performance curve plotted with the first end face nozzle with diameter D1. Step 3: Compare the measurement points of the first performance curve with the relationship curve between the composite coefficient and Reynolds number specified in the "Performance Test of Standardized Air Ducts for Industrial Ventilation Fans GB / T1236-2017"; If the Reynolds number corresponding to the maximum flow point of the ventilator exceeds the upper limit, the diameter of the first end face nozzle is increased to obtain a second end face nozzle with a diameter of D2. Then, the aerodynamic performance test is performed to obtain a second performance curve. The second performance curve is specifically a flow-pressure performance curve plotted with the second end face nozzle with a diameter of D2, where D2>D1. If the Reynolds number corresponding to a detection point before the minimum flow rate point of the ventilator exceeds the lower limit, the diameter of the first end-face nozzle is reduced to obtain a third end-face nozzle with a diameter of D3. Then, aerodynamic performance testing is performed to obtain a third performance curve. Specifically, the third performance curve is a flow-pressure performance curve plotted with the third end-face nozzle having a diameter of D3, where D3... <D1; Step 4: Fit the first performance curve with the second performance curve, or fit the first performance curve with the third performance curve, to form the complete aerodynamic performance curve of the ventilator.

2. The method for measuring flow rate of a ventilator using nozzles of different sizes according to claim 1, characterized in that, The end-face nozzle is either arc-shaped or conical.

3. The method for measuring flow rate of a ventilator using nozzles of different sizes according to claim 1, characterized in that, The fourth step, curve fitting, involves selecting the area near the high-efficiency point within the overlapping flow range of the two curves, using the same flow point as a reference point, taking different flow range curves measured by nozzles with different diameters, and fitting the two different flow range curves into a complete aerodynamic performance curve.

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