The fluid extracted from the holes of the pipe wall is adopted for gas-liquid two-phase flow rate metering to avoid the blockage in the traditional sampling method. The pipe wall with four 2.5 mm diameter sampling holes and a spin generating element mounted upstream for modifying the inlet flow pattern are set up to improve the representative of the sampled fluid. The stratified flow

slug flow and asymmetry annular flow upstream become symmetry annular flow with uniform film thickness after the spin generating element. The liquid extraction ratio is only determined by the diameter and number of the sampling holes and independent of gas and liquid flow rate of the main pipe

and the gas extraction ratio is mainly controlled by the liquid flow rate of the main flow loop. The experiments have been carried out at a 40 mm diameter air-water two-phase flow loop

and the results indicate the liquid extraction ratio near 0.049. The maximum errors of the liquid and gas flow rate measurement approach to 6.8% and 8.9%

respectively.