Hi, engineering control small housekeeper come today to bring us the measuring principle of vortex flowmeters, the working principle of vortex flowmeter is set in the fluid spiral body, body side alternately happens to have the rules of the vortex, downstream asymmetric vortex column in spiral body is arranged, produce certain frequency, through the formula of (St to strouhal number, as the dimensionless number, associated with spiral body and Reynolds number; V as the velocity of flow; D to happen right against the face width; D for the nominal diameter) can be concluded that the velocity,

Generally speaking, vortex street flowmeter output signals (frequency) is not affected by changes of fluid physical properties, and component, is refers to the instrument coefficient only involved in the body shape and size as well as the Reynolds number vortex, its advantages are: simple structure and firm, easy installation and maintenance; Suitable for many kinds of fluid, liquid, gas, steam and partially miscible phase all apply; Accuracy is higher, generally around +/- 1% R; Wide flow range and can reach 10:1 or those days or more; Small head loss; No zero drift; The price is relatively cheap; Defect is: not suitable for low Reynolds number Re <20000, with high viscosity, low flow velocity, the use of small diameter limit; On the environment of the demand is higher, should try to put an end to the places where the vibration, and the straight pipe upstream side need to have a longer; Less meter coefficient is low, the greater the diameter, the signal resolution is reduced, so the caliber shoulds not be too big, generally applied to DN15 ~ DN300mm,

1. The advantages of

Vortex flow meter has simple structure and firm, easy installation and maintenance (compared with the throttle differential pressure flowmeter, without guide tube and three valve group, etc., to reduce leakage, plugging and freezing, etc.),

Apply fluid types, such as liquid, gas, steam and partially miscible fluids,

Teach high precision (and differential pressure type, float-type flowmeter comparison), is commonly measured values of pressure loss of the (plus or minus 1% to plus or minus 2%) small (about 1/4 to 1/2) for orifice flowmeter, the output is proportional to the flow of the pulse signal, apply to the total measurement, no zero drift; Within a certain Reynolds number, the output frequency signal from the fluid physical properties (density, viscosity, and the influence of components, namely the meter coefficient only involved in the body shape size of the pipe and spiral, only need to check in a typical medium and are suitable for all kinds of medium,

2, the limitation of

Vortex flow meter is not suitable for measuring low Reynolds number (ReD 2 x 104 or higher), so in high viscosity, low flow rate, small case application is restricted,

Vortex separation velocity distribution stability of distortion and the influence of the rotational flow, should according to different forms of upstream side enough to choke a configuration long straight section (rectifier), or installing flow regulator can draw lessons from the throttle differential pressure flowmeter commonly straight pipe length required to install, compared with the turbine meter instrument coefficient is low, low resolution, less the greater the diameter, tube flowmeter for 12 below, filled with average instrument in the pulsating flow, mixed phase flow, the lack of theoretical research and practical experience,

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