Abstract: The composition, working principle and application range of HKU ultrasonic flowmeter are systematically expounded, the advantages and disadvantages of various flowmeters are compared, and the errors of HKU ultrasonic flowmeter are analyzed in detail. The calibration and application of flowmeter are briefly introduced The scope of the current research and application has a guiding role. Key words: HKU ultrasonic flowmeter principle calibration measurement error analysis application 1 composition and working principle HKU ultrasonic flowmeter by the ultrasonic transducer, electronic conversion lines, flow display system consists of three parts. Ultrasonic transducers made of cast iron lead-acid piezoelectric elements transmit and receive acoustic waves using piezoelectric effects and measure the fluid volume flow by detecting the effect of the fluid on the ultrasonic beam (or ultrasonic pulse). HKU ultrasonic flowmeter principle: the voice signal transmitted through the pipeline flow medium, the transmission speed of the media flow speed. The transmission time of the acoustic signal between the two sensors depends on the flow rate of the medium in the pipe. An acoustic signal travels upstream longer than it passes downstream. This time difference dt is proportional to the flow rate vf of the medium in the pipe. As shown in Figure 1. Currently used HKU ultrasonic flowmeter system mainly has the following two kinds of working principle: 1.1 speed method [1] Pipeline flow velocity vf obtained by the following formula: vf = (L / 2cosβ) [dt / (t1t2)] (1) Where: t1, t2 represent the acoustic signal through the upstream and downstream time; dt is the acoustic signal through the upstream and downstream of the time difference; L is the acoustic signal through the path length; β represents the tube axis and the angle between the L. 1.2 Ring System (Sing-around System) [2] If you compare the frequency difference between two pulse trains in two different directions, this pulse difference is also proportional to the velocity of the fluid. This is the fundamental frequency representation of the flow rate, independent of the speed of sound in the fluid. The theoretical basis of the above two algorithms for fluid velocity is the same, and the theoretical values ​​of fluid velocity vf are basically the same. The use of different secondary instruments set different flow coefficient can display the volume flow. 2 Features [3] (1) Suitable for high-precision measurement of a variety of pipe flow, the larger the flow and diameter, the higher the accuracy; (2) measuring range (range ratio) is very wide, usually 1: 40 ~ 1: 160, the maximum can reach 1: 300; (3) high repeatability, can achieve two-way flow measurement; (4) flowmeter body pressure loss, accurate measurement of pulsatile flow; (5) energy saving, can greatly reduce the cost of long-distance pipeline pressurization; (6) Not affected by sediment or moisture, no moving parts; (7) The required straight pipe length upstream and downstream is shorter (upstream 10D, downstream 3D); (8) No wear and tear, showing zero drift phenomenon, offset error is small; (9) dynamic measurement of a wide range; (10) Unaffected by changes in eddy current and velocity profile; (11) Unaffected by pressure, temperature, molecular weight, changes in gas composition; (12) No need to repeat the calibration. 3 flow meter performance comparison Table 1 for the flow meter performance comparison table. 4 application 4.1 Metering fluid volume flow When used as a flowmeter, the flow range is very wide, can be measured bi-directionally, for high viscosity, or even a small flow of fluid can be measured. At the same time, its maintenance costs are lower. It has no mechanical parts in the pipeline, is not affected by other media, do not need to adjust and control, do not need to stop production operation. However, the accuracy of the HKU ultrasonic flowmeter depends on the characteristics of the medium. Its compensation technique is necessary. To simplify the compensation factor f, a straight tube of 10 times its diameter and a straight tube of 5 times its downstream diameter must be retained upstream of the pipeline. For certain installation conditions and fluid properties under conditions to determine an actual flow coefficient compensation. 1. Knee wraps Helps smoothe aches and muscle pains
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