The current status and future of Coriolis mass flowmeter
Mass flow meters are now favored by users because they directly measure the mass flow of fluid in the pipeline, rather than measuring the volumetric flow and density of the fluid being measured, as calculated in the past, and then calculating it. In addition, its accuracy and stability are higher, the range ratio is larger, but its performance price ratio is too high. For manufacturers, this is a very profitable product, so the development, trial production and marketing of this product has been positive.
Principle
The principle of the Coriolis mass flowmeter is essentially to utilize the resonance characteristics of an elastomer: for the metal tube components of the fluid flow and the vibration without fluid flow (near the resonance region), the dynamic response characteristics are determined, and the resonance system is determined. The relationship between phase difference (time difference) and mass flow. The difference between the dynamic response characteristic of a metal tube element having a fluid flow and the dynamic response characteristic of a metal tube having no fluid flow is due to the Coriolis effect. The so-called Coriolis effect means that when the particle moves relative to one another in a rotating reference frame, an inertial force different from the usual centrifugal force acts on the particle. Its size and direction can be expressed by 2mvXw (formula). This was first discovered by the French scientist Coriolis. A flow meter constructed using an elastic element of the above principle is also referred to as a Kord's mass flow meter. Therefore, in order to theoretically analyze and develop the mass flowmeter, the difficulty is essentially to calculate the dynamic resonance characteristics of the elastic metal tube. This is mainly determined by the vibration analysis of the elastomer by the theory of solid mechanics. One of the existing literature reports is the dynamic response analysis of flexible tubes.
Some mechanical problems that need to be solved urgently
1.In theory, the accuracy of the Coriolis mass flowmeter is not affected by the operating conditions of the fluid being tested, but the actual situation is indeed affected by the various operating conditions of the fluid (although this effect is small) The reason is still unclear. The authors estimate that this is caused by the additional Korotkoff effect caused by the secondary eddy currents in the pipe of the primary element.
2.In principle, the mass flow meter can measure two-phase fluid, but in fact the measurement error is also large, which makes the industry unable to accept applications in this field, and is currently studying this problem further.
3.In addition, since the primary component is vibrating, it is greatly affected by the interference of external vibrations. This problem has attracted the attention of manufacturers and is under study. The author believes that this problem should be started from the design of anti-vibration components and circuits, but first of all, the frequency shift and frequency-locking should be analyzed to find suitable anti-vibration measures.
Material problemSince the metal tube is vibrated at the time of the primary sensor, it is considered that the tube can withstand the impact of fatigue and the ability to withstand corrosion under various environments. As we all know, the increased ability to resist fatigue damage is first to reduce the vibration amplitude of the metal tube, second to increase the wall thickness of the vibrating tube, and third, to select the appropriate metal material. At present, most of the 316L stainless steel is used. The more ideal metal material is Hastelloy alloy, which is NiCrMo alloy. Its ability to resist fatigue damage is stronger than 316L, especially in the case of practical chloride corrosion. Although titanium alloy is the best, it is too expensive.
Precision problemAt present, Western manufacturers claim that the Coriolis mass flowmeter can achieve an accuracy of 0.5% or even 0.2% or 0.1%. However, special care must be taken when using it. The accuracy in the low flow range generally does not reach the above accuracy value. In addition, the zero drift of the secondary instrument, especially after a period of use, does not reach the value given by the manufacturer.
VisionIt is estimated that there are about 150,000 mass flow meters in the world operating in various industrial sectors. At present, mass flow meters account for about 3%-5% of the total number of flow meters produced and sold in the West every year. However, because the high-tech added value of the mass flow meter is large, its profit can be as high as 70% or more, so Western companies have profited a lot.
Judging from the current development of flow metering in the world, there is no doubt that the Coriolis mass flow meter seems to quickly occupy a large market in the measurement field dominated by capacity metering. This is a very profitable product, and with the fierce competition in the market, its price/performance ratio will be reduced appropriately. But only when its price/performance ratio is greatly reduced can it be widely used in industry.
Principle
The principle of the Coriolis mass flowmeter is essentially to utilize the resonance characteristics of an elastomer: for the metal tube components of the fluid flow and the vibration without fluid flow (near the resonance region), the dynamic response characteristics are determined, and the resonance system is determined. The relationship between phase difference (time difference) and mass flow. The difference between the dynamic response characteristic of a metal tube element having a fluid flow and the dynamic response characteristic of a metal tube having no fluid flow is due to the Coriolis effect. The so-called Coriolis effect means that when the particle moves relative to one another in a rotating reference frame, an inertial force different from the usual centrifugal force acts on the particle. Its size and direction can be expressed by 2mvXw (formula). This was first discovered by the French scientist Coriolis. A flow meter constructed using an elastic element of the above principle is also referred to as a Kord's mass flow meter. Therefore, in order to theoretically analyze and develop the mass flowmeter, the difficulty is essentially to calculate the dynamic resonance characteristics of the elastic metal tube. This is mainly determined by the vibration analysis of the elastomer by the theory of solid mechanics. One of the existing literature reports is the dynamic response analysis of flexible tubes.
Some mechanical problems that need to be solved urgently
1.In theory, the accuracy of the Coriolis mass flowmeter is not affected by the operating conditions of the fluid being tested, but the actual situation is indeed affected by the various operating conditions of the fluid (although this effect is small) The reason is still unclear. The authors estimate that this is caused by the additional Korotkoff effect caused by the secondary eddy currents in the pipe of the primary element.
2.In principle, the mass flow meter can measure two-phase fluid, but in fact the measurement error is also large, which makes the industry unable to accept applications in this field, and is currently studying this problem further.
3.In addition, since the primary component is vibrating, it is greatly affected by the interference of external vibrations. This problem has attracted the attention of manufacturers and is under study. The author believes that this problem should be started from the design of anti-vibration components and circuits, but first of all, the frequency shift and frequency-locking should be analyzed to find suitable anti-vibration measures.
Material problemSince the metal tube is vibrated at the time of the primary sensor, it is considered that the tube can withstand the impact of fatigue and the ability to withstand corrosion under various environments. As we all know, the increased ability to resist fatigue damage is first to reduce the vibration amplitude of the metal tube, second to increase the wall thickness of the vibrating tube, and third, to select the appropriate metal material. At present, most of the 316L stainless steel is used. The more ideal metal material is Hastelloy alloy, which is NiCrMo alloy. Its ability to resist fatigue damage is stronger than 316L, especially in the case of practical chloride corrosion. Although titanium alloy is the best, it is too expensive.
Precision problemAt present, Western manufacturers claim that the Coriolis mass flowmeter can achieve an accuracy of 0.5% or even 0.2% or 0.1%. However, special care must be taken when using it. The accuracy in the low flow range generally does not reach the above accuracy value. In addition, the zero drift of the secondary instrument, especially after a period of use, does not reach the value given by the manufacturer.
VisionIt is estimated that there are about 150,000 mass flow meters in the world operating in various industrial sectors. At present, mass flow meters account for about 3%-5% of the total number of flow meters produced and sold in the West every year. However, because the high-tech added value of the mass flow meter is large, its profit can be as high as 70% or more, so Western companies have profited a lot.
Judging from the current development of flow metering in the world, there is no doubt that the Coriolis mass flow meter seems to quickly occupy a large market in the measurement field dominated by capacity metering. This is a very profitable product, and with the fierce competition in the market, its price/performance ratio will be reduced appropriately. But only when its price/performance ratio is greatly reduced can it be widely used in industry.
Welcome to visit our website to learn more information: www.aft-flowmeter.com
评论
发表评论