Principle and structure of wedge flowmeter

Measuring principle
Wedge flowmeter is based on Bernoulli formula, which uses the principle that the fluid obeys the law of energy conservation in the flow process, that is, the sum of kinetic energy and static pressure energy is unchanged, and the fluid flow is measured based on the pressure difference generated when it passes through the circular wedge block that plays the role of throttling. The wedge flow orifice is made of two flat plates (generally stainless steel), which are welded together at the critical angle, and then inserted into the groove. The differential pressure outlet pipe is located at the equal distance on both sides of the center of the wedge. When the fluid flows through the V-shaped throttle block, the flow area decreases, the flow rate increases, and the static pressure decreases, resulting in a static pressure difference. Since the square root of the pressure difference is proportional to the flow, the flow in the pipeline can be obtained by measuring the pressure difference.

Structure and basic characteristics
1. Basic structure of wedge flowmeter
The wedge flowmeter is simple in structure, and its structure is between the round orifice plate, nozzle and 1/4 round orifice plate. While taking into account the advantages of the above types of flowmeter, it also has good adaptability.
2. Main features
(1) Dirty fluid is easy to pass through, and dirt is not easy to attach and deposit, which improves the accuracy of measurement, prolongs the use and maintenance period, and is suitable for measurement of various media such as metallurgy, chemical industry, and environmental protection.
(2) The requirements for the sharpness of the orifice plate inlet are improved, and the measurement accuracy is improved.
(3) It is suitable for high viscosity medium and widely used.
(4) Wide range ratio, usually more than 10 ∶ 1; The measurement accuracy is high, up to ± (0.5~1)% FS.
(5) Pressure loss is smaller than orifice plate
The included angle of wedge orifice is generally 60 °~90 °. If the included angle is 0 °, it becomes a round hole plate. The smaller the included angle is, the greater the static pressure difference will be, and the pressure loss will increase accordingly. As the wedge-shaped orifice is inverted triangle, this shape has the role of guiding, and the fluid can smoothly transition when flowing. Compared with orifice plate, wedge orifice plate produces less pressure loss. It is a comparison of the pressure loss generated by wedge orifice and sharp orifice.
(6) Wedge shaped orifice plate has the advantages of round hole plate
When the fluid contains impurities or solids, it is easy to flow through the lower part of the wedge-shaped orifice plate and will not deposit around the orifice plate, that is, the wedge-shaped orifice plate has a self-cleaning effect.
(7) Suitable for low Reynolds number RD flow measurement
The standard orifice plate and venturi should not be measured at low Reynolds number. The flow coefficient of the standard orifice tends to be stable when the Reynolds number is above 4000. At low Reynolds number, the flow coefficient will change with the change of Reynolds number. When Reynolds number is less than 1800, the relationship between flow rate and differential pressure will deviate from the basic square root, which will obviously affect the measurement accuracy. The wedge-shaped orifice is a V-shaped throttling element with a good linearity of flow coefficient, a smooth curve at the nozzle inlet, and no stagnation zone. Reynolds number has little influence on it. When Reynolds number is less than 500, the accuracy and flow coefficient of wedge flowmeter have little change; The Reynolds number is between 400 and 10000 for flow measurement, and the error is less than ± 3%. Curve of Reynolds number and flow coefficient of wedge orifice
(8) Easy to install and use
Compared with orifice plate, both ends of wedge flowmeter can be connected with process pipe by flange, which is convenient for installation, small for daily maintenance and relatively low for operation cost.


Post time: 27-10-22