Beta ratio, axisymmetric flow distortion and swirl effects upon orifice flow meters

Abstract

The objective of this study is to measure the response of the orifice meter to known upstream flow field disturbances generated by a concentric tube flow conditioner and a vane-type swirl generator. These disturbances are characterized by measuring the axial and tangential velocity profiles at the upstream flange tap with no orifice plate present. Two different flow rates are examined which correspond to Reynolds numbers of 91 100 and 120000 in a 50.8 mm diameter pipe. Eight orifice plates with β ratios of 0.43, 0.45, 0.484, 0.55, 0.6, 0.65, 0.7 and 0.726 are studied at both flow rates. The response of each orifice meter to the disturbance is characterized by measuring the axial wall pressure distribution near the orifice plate and the discharge coefficient. These data show that a nondimensionalized pressure does not change with varying axisymmetric flow distortions. However, the pressure distribution is very dependent upon the swirl. The axial momentum distribution is quantified by calculating the second-order moment of axial momentum ( R 2[ u] from the velocity profile data. Swirl is quantified by determining the centripetal acceleration flux of the flow (ψ), also from the velocity profile data. Surface fits indicating the variation of discharge coefficient as a' function of β ratio and R 2[ u] or ψ are developed.