SKLU series Vortex flowmeter

The SKLU series vortex street flowmeter mainly uses in the industry pipeline medium fluid the flow measurement, like gas, liquid, vapor and so on many kinds of medium. Its characteristic is the pressure loss is small, the measuring range scope is big, the precision is high, when survey operating mode rate of volume flow nearly not parameter and so on fluid density, pressure, temperature, viscosity influences. Not movable machine parts, therefore the reliability is high, maintains the quantity to be small. The measuring appliance parameter can the long-term stability. The vortex street flowmeter uses the piezoelectricity stress type sensor, the reliability is high, may in - 20℃~+250℃ the operating temperature scope works. Has the mock standard signal, also has the digital pulse signal output, easy and number system necessary uses and so on computer, is one kind quite advanced, the ideal flow instrument.

Vortex street flowmeter principle
Establishes the triangle columnar order whirlpool in the fluid to have the body, has the body both sides from the whirlpool to produce alternately has the rule whirlpool, this kind of whirlpool is called the Carmen whirlpool, if the figure to the right shows, turns on lathe the vortex street to have the body downstream in the whirlpool to arrange asymmetrically.
Supposes the whirlpool the occurrence frequency is f, was measured that the medium mean velocity of stream is, the whirlpool has the body to welcome the flow surface width is d, shows the body latus rectum is D, then obtains the following relationship:

　f=SrU1/d=SrU/md 　　　　　　　　　　　　　　　　　　　　(1)
In the formula U1--The whirlpool has the body both sides mean velocity of stream, m/s;
　　　　 Sr--Strouhal number;
　　　　 m--Of the whirlpool has ratio of the body both sides arch area and the pipeline cross-section area
　　　　　　　　

　In the pipeline rate of volume flow qv is
　　　　　　　　　　　　 qv=πD2U/4=πD2mdf/4Sr 　　　　　　　　　　　　　　　　(2)
　　　　　　　　　　　　 K=f/qv= [πD2md/4Sr] - 1 　　　　　　　　　　　　　　　　 (3)
In the formula K--Flowmeter's scaling factor, the pulse counts /m3 (P/m3).
　　 K besides has the body, pipeline's geometry size with the whirlpool related, but also concerns with the Strouhal number. The Strouhal number is the zero dimension parameter, it has the build shape and the Reynolds number with the whirlpool related, shown in Figure 2 for the circle columnar whirlpool has body's Strouhal number and the pipeline Reynolds number relational graph. The figure shows, in ReD=2×104~7×106 the scope, Sr may regard as the constant, this is the measuring appliance normal work scope. When survey gas flow amount, the VSF current capacity formula is

　　　　　　　　　　 　　　　　　　　　　　　　　　　 (4)

Figure 2 Strouhal number and Reynolds number relations curve

In the formula qVn, qV--Respectively is under the standard state (0oC or 20oC,101.325kPa) and under the operating mode rate of volume flow, m3/h; 
　　 Pn, P--Respectively is under the standard state and the operating mode absolute pressure, Pa;
　　 Tn, T--Respectively is under the standard state and the operating mode thermodynamic temperature, K;
　　 Zn, Z--Respectively be under standard state under and operating mode gas loading coefficient. 
　　 Is obvious by the above equation, the VSF output's pulse frequency signal not the fluid nature and the component change's influence, namely the scaling factor only has in certain Reynolds number scope with the whirlpool the body and pipeline's shape size and so on concerns. But must examine the mass flow as the flowmeter in the mass balance and in the energy measurement, by now flowmeter's output signal should simultaneously monitor the rate of volume flow and the fluid density, the fluid nature and the component has the immediate influence to the flow measurement.

　　The vortex street flowmeter is carries on the solid surrounding boundary rate of fluid flow survey based on the Carmen whirlpool principle the new flowmeter. Because it has the good medium adaptiveness, does not need the temperature pressure compensation then direct measurement steam, the air, the gas, the water, the liquid operating mode rate of volume flow, provides the temperature, the pressure transmitter to be possible the surveyor's beacon situation rate of volume flow and the mass flow, is the throttle type flowmeter's ideal substitution product.