Long-throat-and-neck venturi tube moisture flow measurement method based on flowing density

The invention relates to a long-throat-and-neck venturi tube moisture flow measurement method based on the flowing density. The method comprises the steps of calculating the gas phase flow initial value; calculating the gas phase flow velocity; calculating the gas phase Froude number; calculating the efflux coefficient; calculating the L-M parameter; calculating the dryness initial value; calculating the cross sectional gas containing rate; obtaining the virtual height; calculating out the differential pressure when a gas phase flows through a venturi tube separately; calculating and obtaining the two-phase mixed mass flow rate; calculating the flowing density of a two-phase flow; calculating out the gas containing rate per volume; calculating out the new gas containing rate per mass and the new cross sectional gas containing rate, judging whether convergence is conducted or not, and if not, treating the cross sectional gas containing rate which is calculated out as the initial value for recalculation; calcul