The invention discloses a rectification-technology-based method for measuring a wet
natural gas flow rate by combining
ultrasound with a target flowmeter. A measuring
system includes an
inverted U-shaped measuring pipeline, a
nozzle rectification
machine, an
ultrasound flowmeter, the target flowmeter, a
pressure sensor, a temperature sensor and the like. The
nozzle rectification
machine, the
ultrasound flowmeter and the target flowmeter are mounted at the descending side of a U-shaped measuring
pipe. Wet gas flows through the
nozzle rectification
machine and is adjusted into approximate homogeneous phase flow; when ultrasonic is propagated, the ultrasonic flowmeter which works in a
transit time mode measures the apparent volume flow rate of the wet gas; in combination with the apparent volume flow rate measured by the ultrasonic flowmeter, the target flowmeter measures the
apparent density of the wet gas; under the conditions that gas-phase components of the wet gas are known, the
liquid phase is incompressible and the liquid-
phase density is known, according to pressure and temperature parameters, the gas-
phase density can be calculated; finally, according to the apparent volume flow rate and
apparent density of the wet gas, the liquid-
phase density and the gas-phase density, a liquid-
phase volume fraction, a liquid-
phase volume fraction, a liquid-
phase volume flow rate, a liquid-phase
mass flow rate, a gas-phase volume flow rate and a gas-phase
mass flow rate are calculated, and therefore the online non-separation measurement of the wet
natural gas flow rate is achieved.