超声流量计 7. Ultrasonic flowmeter
An ultrasonic flowmeter suitable for natural gas storage transfer measurement; low transmission efficiency of ultrasonic waves at the solid-gas interface; it is difficult to mount an ultrasonic transducer (probe) outside the channel to transmit sufficient sound energy from the pipe wall; there is currently no external clamp Mounted gas ultrasonic flowmeter.
20 世纪 80 年代初，大部分由测量短管和插入管壁换能器组成一体的形式出现，由于测量精度较低，过去未能在价格昂贵的天然气贸易结算计量领域占有一席之地，近年则出现多种型号精度较高的气体超声流量计。 Gas ultrasonic flowmeters began in the early 1980s. Most of them consist of measuring tubes and transducers inserted into the tube wall. Due to the low measurement accuracy, they have not been used in the field of expensive natural gas trade settlement measurement in the past. Occupy a place, in recent years, a variety of models of high accuracy gas ultrasonic flowmeters have appeared.
The ultrasonic flowmeter uses the physical properties of ultrasonic waves with different propagation speed in different liquids to identify the type of liquid in the pipeline while measuring the flow rate.
For example, in Europe, an ultrasonic flowmeter is often used to measure the flow rate when the ship is unloaded into the warehouse, and at the same time, it is judged whether the liquid being transported is oil or the bottom water of the tanker.
（直接时差法、时差法、相位差法和频差法）；束偏移法；普勒法；间滤法及噪声法等。 According to the principle of signal detection, ultrasonic flowmeters can be divided into the propagation velocity difference method (direct time difference method, time difference method, phase difference method, and frequency difference method); beam shift method; Pooler method; indirect filtering method and noise method, etc. .
Ultrasonic flowmeters are the same as electromagnetic flowmeters. Because the flow channel of the instrument is not provided with any obstructions, they are all unobstructed flowmeters. They are a type of flowmeter suitable for solving difficult problems in flow measurement, especially in large-caliber flow measurement. The advantage is one of a class of flowmeters that has developed rapidly in recent years.
The advantages of ultrasonic flowmeters are: non-contact measurement; no flow obstruction measurement and no pressure loss; non-conductive liquids can be measured, which is a complement to the electromagnetic flowmeter without obstruction measurement.
Disadvantages of ultrasonic flowmeters are: the time-of-flight ultrasonic flowmeter can only be used to clean liquids and gases; the Doppler ultrasonic flowmeter can only be used to measure liquids containing a certain amount of suspended particles and bubbles; the Doppler ultrasonic The measurement accuracy of the flow meter is not high.
科里奥利流量计 8. Coriolis flowmeter
The Coriolis flowmeter uses the phase difference of the vibration frequency of the measuring tube to be proportional to the mass flow rate to measure the flow rate, and uses the function relationship between the resonance frequency of the measuring tube and the density of the medium in the tube to determine the density.
qm 和密度ρ衍生得出体积流量 qv ；若被测液体是两种有一定密度差的混合液体，还可经密度演算得出一种液体在混合液中的浓度。 Coriolis flowmeter also derives volume flow rate qv from two basic parameters: mass flow rate qm and density ρ ; if the measured liquid is two mixed liquids with a certain density difference, a liquid can also be obtained through density calculation. Concentration in the mixture.
Due to the different measuring principles of different flowmeters, the uses of flowmeters are not the same, so far no one flowmeter is universal.
Each type of flowmeter is always limited in use due to the limitations of its measuring principle, its ability to adapt to the type of measurement medium, the characteristics of the measurement medium and the characteristics of flow changes, and the ability to adapt to environmental conditions.
Because of this, while new flowmeters continue to appear, some traditional flowmeters with a long application history are still widely used.