How do ultrasonic flow meters cope with measurement challenges under complex working conditions?

In recent years, China's ultrasonic flow meters have developed rapidly. 

Due to their high accuracy, low pressure loss, wide range ratio and strong adaptability, they have become recognized as superior flow measurement solutions. 

At present, they have been successfully applied to domestic and foreign turbine condition monitoring, South-to-North Water Diversion, Xijiang Water Diversion and other projects. 

Based on the time difference method, ultrasonic meters cannot obtain the average surface velocity of the cross section, but can only obtain the linear average velocity of the sound 

wave signal on the propagation path, derive the relationship between the measured value and the theoretical value in the velocity profile distribution, and obtain the change law of the 

K coefficient and the Reynolds number.

In the actual field application environment, it is found that the most common working condition is that the ultrasonic flow meter is equipped with the same direction elbow structure upstream 

and downstream. After the fluid flows through the elbow, the downstream velocity profile distribution is distorted, and the measured area is in a non-ideal asymmetric state. 

When the sound wave path form and integral calculation cannot offset and compensate for this velocity offset, the accuracy of the ultrasonic flow meter will become very sensitive to this distribution, 

resulting in flow measurement distortion. Therefore, it is necessary to find a sound path arrangement method to solve the deviation caused by non-ideal installation environment and 

velocity distortion to calibration and practical application.

We simulated and tested the performance of multi-path ultrasonic flowmeter in the curved pipe environment, pointed out that the appropriate installation parameters and double-section 

measurement can reduce the influence of cross flow on measurement; we and others conducted theoretical and simulation research on the flow field of the curved pipe model 

and quantified many influencing factors of ultrasonic flowmeter error; Bao Min and others obtained the internal flow state and corresponding flow coefficient curve of the specific curved pipe 

through theoretical calculation and CFD technology; GB/T 35138-2017 "Liquid Ultrasonic Flowmeter for Measurement of Fluid Flow in Closed Pipes by Transit Time Method" and ASME PTC 18-2011 

"Specification for Performance Test of Turbines and Pump-Turbines", etc., pointed out that the multi-section multi-chord position distribution can improve the sensitivity of flow measurement to flow state 

distribution distortion and effectively eliminate or reduce the influence of vortex and cross flow. With the development of fluid simulation technology, CFD has gradually become a means of flow field 

analysis and structural optimization of ultrasonic instruments.

lnalsafe is a flow meter manufacturer www.lnalsafe.com.

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