METHOD FOR MEASURING VOLUME FLOW IN VORTEX FLOWMETERS Russian patent published in 2020 - IPC G01F1/32 

FIELD: measuring equipment.

SUBSTANCE: invention relates to measurement equipment and can be used in vortex counters of flow meters for measurement of volume flow using Karman vortices. Method of measuring volume flow in vortex flowmeters involves creating in a measuring channel of a counter a regular sequence of vortices, recording each vortex in the form of an electric pulse, measuring current values of pulse repetition frequency f, as well as temperature and pressure of substance, calculation by indirect method of current value of kinematic viscosity of substance ν: for liquid – by temperature, for gas or steam – by temperature and pressure. Volumetric flow rate Q is calculated in accordance with the expression Q=f·C/Sh, using the measured vortex frequency f, the constant C coefficient, which is equal to the geometric constant of the measurement channel and the calculated current value of the Strouhal number Sh based on the linearized expression of the dependence of the number Sh on the inverse value of the dimensionless numbers Ro, which allows to expand range and increase accuracy of flow rate measurement. Coefficients a and b for the linearized dependence Sh (1/Ro) are determined by the method of least squares during calibration of the vortex flow meter based on specified reference points of flow rate. Volume W of the leaked substance is defined as the product of the sum of pulses recorded during the measurement period by the pulse weight, W=ΣN·P_P, wherein the pulse weight supplied to the flow meter output can have any given fixed value equal to the substance volume. Using the linearized expression for the Strouhal Sh number of the form Sh=a+b/Ro as linear dependence of the number Sh on the inverse value of the dimensionless number Ro, the coefficients a and b of which are calculated using the least squares method, enables to expand the measurement range for the vortex flowmeters for given measurement error. It also makes it possible to avoid calculation of the current value Sh through the approximating dependence of the number Sh of the Strouhal through the Reynolds number – Sh (Re), which introduces additional errors into the flow measurement due to determination of the number Re through the additional approximating function Re(Ro), thus providing higher measurement accuracy . Calculation of flow rate, performed using parameters of medium (dimensionless number Ro), frequency f of vortices and geometrical constants of measuring channel (number C), allows to leave in calculations from weight coefficient, unequal in general case ratio C/Sh, which makes it possible to use any weight of the pulse arriving at the output of the vortex flow meter, equal to the volume of the last substance, and to expand the measurement range.

EFFECT: high measurement accuracy while widening the operational capabilities of the vortex flow meter.

1 cl, 4 dwg