Implementing the differential pressure porous orifice flowmeter

Orifice plate flowmeter is a typical differential pressure flowmeter, which mainly measures the flow rate in the pipeline by detecting the pressure difference before and after the orifice plate. Due to its simple structural design, no moving parts, reliability and durability, and convenient installation and maintenance, it has been widely used in industry. In current industrial production, orifice flow meters are commonly used for measuring the flow rates of gases, liquids, and water vapor. However, due to the friction effect and boundary layer separation phenomenon when the fluid flows through the orifice plate, the standard orifice plate flowmeter faces problems of large pressure loss and low measurement accuracy. In addition, due to the sensitivity of the standard orifice flowmeter to changes in upstream fluid state, it is mainly suitable for fully developed flow and usually requires a long upstream straight pipeline, which also limits its use to some extent. In order to improve the performance of orifice flow meters, porous orifice flow meters are increasingly being applied in industry.
In 2004, the Marshall Aeronautics Flight Center, a subsidiary of NASA, proposed a new type of differential pressure porous orifice flowmeter, which was applied in rocket design. This new type of flowmeter has a symmetrical porous structure, which not only inherits the advantages of a standard orifice plate flowmeter with simple structure and no moving parts, but also can balance and adjust the flow field, reduce eddy currents, reduce dead zone effects, and reduce the loss of fluid kinetic energy.
Compared to standard orifice flow meters, porous orifice flow meters have superior performance, requiring fewer upstream pipelines, low energy consumption, and can provide more accurate fluid flow measurement. However, the uncertainty of the arrangement of porous pores and the complex geometric features make its structural design and optimization extremely complex, which greatly limits its application. In order to better design porous orifice flow meters, scholars at home and abroad have conducted extensive research and achieved certain results. Ma et al. conducted experimental research on the flow coefficient, pressure loss, and anti vortex performance of porous orifice plates as a new type of throttling device. Zhao et al. proposed a classification scheme for porous plates and conducted experimental simulations. Malavasi et al. tested the effects of pore number, size, thickness, and Reynolds number on the pressure drop of porous orifice plates.
Huang et al. conducted experiments on a specific porous pore plate and compared it with a standard pore plate. Singh et al. used computational fluid dynamics simulations to study the flow state of porous orifice plates. Ma Youfu et al. used numerical methods to study the influence of the number of pores and thickness on the pressure loss coefficient of porous plates. Mehmood et al. used central composite design and computational fluid dynamics to evaluate the effects of pore number, diameter ratio, and plate thickness on pressure loss coefficient. The results show that the pressure loss coefficient is a strong function of the diameter ratio, and the flow coefficient improves with the increase of the number of holes. Chen Hong et al. used numerical methods to study the effect of orifice plate chamfer on the working performance of balanced low-temperature flow meters. They found that appropriately setting the front chamfer can effectively improve the working performance of the flow meter. The impact of chamfering on the performance of the flowmeter is relatively small after opening.
Although scholars at home and abroad have conducted extensive theoretical and experimental research on porous orifice plates in recent years, there is currently no universal design and usage standard for porous orifice plate flowmeters. The main purpose of this study is to investigate the influence of structural parameters of porous orifice plates on the performance of orifice flow meters. Firstly, by comparing with standard flow meters of the same size and specification, the flow field characteristics of porous flow meters were analyzed. Then, CFD analysis was performed on 16 porous plates with the same plate thickness and diameter ratio, different number of pores (N=3, 4, 5, 6), and gap ratio (Cr=0.4, 0.5, 0.6, 0.7). The main performance parameters, including pressure loss coefficient, flow coefficient, and pressure recovery length, were used to analyze the influence of pore number and pore distribution on the performance of porous orifice plate flow meters. The research results can provide reference for the structural design and optimization of porous orifice flow meters.