Optimized performance and application of the hotte

Optimization performance and application of porous balance flowmeter

throttling flowmeter is usually called differential pressure flowmeter. So far, it is still widely used in water conservancy, petroleum, chemical industry and other industries because of its standardized manufacturing process, mature application technology and wide application range, accounting for more than 50% of the total number of meters used. However, at the same time, many deficiencies such as low measurement accuracy, small range ratio, long distance between upstream and downstream straight pipe sections, and large permanent pressure loss after throttling devices are also increasingly apparent

with the continuous development of new instrument measurement and manufacturing technology, in order to meet the higher requirements of various process control for the measurement accuracy and performance of throttling flowmeter, a new generation of throttling flowmeter with revolutionary performance breakthrough, namely porous balance flowmeter, was born. At the beginning of its birth, the porous balance flowmeter was first applied to the liquid oxygen flow measurement of the main engine of the space shuttle by the Marshall Aerospace Flight Center of NASA, and then it was known and developed by more industries because of its superior measurement and use performance

working principle

the porous balance flowmeter follows the composition form of the traditional orifice flowmeter, which is composed of throttling device, pressure pipeline transmitting differential pressure signal and differential pressure gauge used for measuring signal. And ingeniously combine the structural form and performance characteristics of the porous rectifier with the traditional single orifice throttle orifice to form a new type of porous throttle rectifier, which is used to replace the original single orifice orifice as a throttle element installed on the fluid pipeline. The size and distribution of each orifice on the porous throttle rectifier are calculated by specific formulas and measured data, so it is called function orifice. During flow detection, the measured medium is rectified while passing through the porous throttling rectifier to reduce the eddy current behind the throttling device and form a relatively stable turbulent flow, so that the pressure pipeline can obtain a relatively stable differential pressure signal, and further calculate the volume flow, mass flow and other flow parameters required by the process through Bernoulli equation

performance optimization of porous balance flowmeter

based on the traditional orifice flowmeter, the porous balance flowmeter changes the composition form of its orifice, which greatly optimizes the service performance by [strain gauge], elastic elements and some accessories (compensation elements, protective covers, wiring sockets, loading parts)

1) balance the flow field and improve the measurement accuracy

the throttling device of the traditional orifice flowmeter is only equipped with a circular orifice, and the junction of the throttling element and the pipe wall is at right angles. When the fluid passes through the orifice, there will be a large area of "dead zone" on both sides of the orifice, resulting in lasting vortex flow, which will consume a lot of kinetic energy of the fluid. At the same time, the fluid fluctuation and noise caused by the chaotic vortex will also reduce the linearity and accuracy of the measurement, and a longer straight pipe section is required to restore the normal pressure and flow field of the fluid. The throttling device of the porous balance flowmeter combines the rectification principle of the porous rectifier. Through the use of precise calculation, the porous throttling rectifier can minimize the dead zone effect, avoid the generation of eddy current, balance the flow field, reduce the signal fluctuation caused by eddy current, and improve the accuracy of the data at the pressure taking point, so as to improve the detection accuracy from ± 1% - ± 2% of the traditional orifice flowmeter to ± 0.3%, ± 0.5%, It can be better applied to occasions with high flow measurement accuracy requirements, such as energy measurement, trade accounting, etc

2) reduce the permanent pressure loss and shorten the installation distance of the straight pipe section

the throttling device of the porous balance flowmeter adopts a symmetrical flow hole layout "meter, which improves the efficiency of fluid passing, reduces the formation of vortex to the greatest extent, and reduces the turbulent friction and kinetic energy loss caused by fluid passing through the throttling device. Compared with the traditional orifice flowmeter, it can obtain a more accurate differential pressure signal, It also reduces the permanent pressure loss of 1/3-1/2. At the same time, the fast and stable recovery of fluid pressure after the throttling device can shorten the distance between the upstream and downstream straight pipe sections required for the installation of the flowmeter. Generally, it only needs 0.5d-2d to install the straight pipe section upstream and downstream of the porous balance flowmeter, which is 1/7 or even shorter than the straight pipe section required by the traditional orifice flowmeter, which greatly saves the pipeline materials and installation investment cost of fluid measurement, and this advantage has also been widely recognized by various industries

3) wide range ratio and better stability

the special porous throttling device of porous balance flowmeter greatly improves the fluid measurement range ratio. The experimental data of an American institution shows that the range ratio of conventional measurement of porous balance flowmeter can reach 7:1-10:1. If the function hole calculation parameters are selected appropriately, the range ratio can reach 30:1 or even higher, which is 13 Motor: the data of imported AC servo motor is 2-7 times higher than that of traditional orifice flowmeter. Moreover, the flow coefficient of traditional orifice flowmeter generally tends to stabilize when the Reynolds number is higher than 4000, and is greatly affected when the Reynolds number is low. However, there is basically no detention zone in the pipeline of porous balance flowmeter, and its flow coefficient is little affected by Reynolds number. Even under the measurement condition of low Reynolds number, the accuracy of porous balance flowmeter can still be guaranteed, which fundamentally improves the stability of measurement accuracy in flow detection

application of porous balance flowmeter

porous balance flowmeter is not only suitable for use under common working conditions, but also has been well used in flow measurement under some special working conditions

1) high range specific flow measurement

in the pharmaceutical, chemical and other industries, steam is generally used as a heat medium in the heating or humidification section. Usually, due to the different heating and humidification quantities required in different seasons or different periods of the day, the steam flow of the steam main pipe fluctuates greatly during steam energy measurement, which is often far beyond the range of the 3:1 range ratio of the traditional orifice flowmeter. Similarly, the traditional orifice flowmeter cannot be applied to other similar situations that require large range specific flow measurement. The porous balance flowmeter can be used for flow measurement with a range ratio of 10:1 or even higher. Because of its high measurement accuracy and little influence by Reynolds number, it can carry out more accurate high range ratio flow detection or energy measurement

2) two way flow measurement

the throttling device of traditional orifice flowmeter only has an inclined angle at the downstream, while the throttling device of porous balance flowmeter adopts a completely symmetrical design at the upstream and downstream. This symmetrical structure makes it possible to use only one flow meter for two-way flow detection under some special working conditions that require two-way flow detection

3) short and straight pipe flow measurement

limited by the external objective conditions such as the size of the site and the size of the building, it is often impossible to reserve enough straight pipe installation distance for flow measurement when arranging the route of the process pipeline, thus affecting the measurement accuracy. Especially when flow measurement is carried out on process pipelines of special precious metals such as zirconium, Hastelloy, chromium molybdenum alloy steel, etc., the demand for long straight pipe section means that expensive construction can well transfer the stress between filler and resin. In this case, the distance between the upstream and downstream straight pipe sections of the porous balance flowmeter is only 0.5d-2d, which has obvious application advantages, which can not only save the laying cost of process pipes, installation supports, etc., but also meet the accuracy requirements in the flow measurement of short straight pipe sections. It is a more economical flow detection configuration

4) large diameter flow detection

in large diameter flow detection, porous balance flowmeter also has its irreplaceable unique advantages. By adjusting the size, number and distribution of the corresponding orifices through accurate calculation, large-diameter flow measurement can be carried out within a short pipeline distance, and there is no need to worry about the upstream and downstream straight pipe distance of 15d or even longer due to the large diameter of the pipeline. Especially in high temperature, low pressure and other harsh conditions, porous balance flowmeter can also ensure the stability of large-diameter flow measurement accuracy. At the same time, the redundant configuration of multiple pairs of pressure tapping holes can be used to ensure that the differential pressure signal is effectively transmitted and reduce the later maintenance, cleaning and operation costs of large-diameter flow detection

5) high temperature and very low temperature fluid measurement

due to the diversity of body and flange materials, the porous balance flowmeter has a wide range of working temperatures. Through the selection of different materials, the porous balance flowmeter can measure high-temperature fluid media with a temperature of 850 ℃ or even higher, and is also suitable for the flow measurement of extremely low-temperature fluids such as liquid nitrogen, liquid oxygen, liquid hydrogen, liquid argon, etc

6) selection of various pipeline connection methods

since the birth of porous balance flowmeter, in order to meet the pipeline connection requirements of various working conditions, a variety of connection methods have been gradually derived for selection. For example, the pipe flange connection can be used for most working conditions, the wafer connection can be used for large-diameter flow measurement, the welding connection suitable for high temperature and high pressure working conditions, and the double flange connection suitable for viscous, toxic, strongly corrosive liquid, dirt and dust gas medium flow measurement, etc. The shape of the throttling device also evolved from the circular pipe throttling device that was originally convenient for pipe connection to the square pipe throttling device, so that it can be more easily connected with various square pipes, and can be applied to the air supply and exhaust volume detection of air conditioning systems

7) integration

driven by the development trend of the integration of detection instruments, the porous balance flowmeter is also integrated into one, integrating the throttling elements, impulse pipelines, valve groups, differential pressure gauges and other instrument elements that need to be installed step by step, so as to reduce the installation steps and meet the needs of rapid installation and use under suitable working conditions

conclusion

the structural and technical innovation of porous balance flowmeter has well avoided the disadvantages caused by the defects of traditional differential pressure flowmeter. With the passage of time, the advantages of porous balance flowmeter gradually appear. Because of its unique performance characteristics and high and stable measurement accuracy, it has been successfully applied in various industries such as steel, petrochemical and so on. Especially in short-distance pipeline flow measurement, saving the cost of pipeline laying and reducing the loss of fluid pressure energy consumption, porous balance flowmeter has irreplaceable advantages. In the future, porous balance flowmeter will be used more widely as an economical measuring instrument