BETA-RATIO, AXISYMMETRICAL FLOW DISTORTION AND SWIRL EFFECTS UPON ORIFICE FLOW METERS

The objective of this study is to measure the response of the orifice meter to known upstream flow field disturbances generated by a concent ric tube flow conditioner and a vane-type swirl generator. These distu rbances are characterized by measuring the axial and tangential veloci ty profiles at the upstream flange tap with no orifice plate present. Two different flow rates are examined which correspond to Reynolds num bers of 91 100 and 120 000 in a 50.8 mm diameter pipe. Eight orifice p lates with beta 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 met er to the disturbance is characterized by measuring the axial wall pre ssure distribution near the orifice plate and the discharge coefficien t. These data show that a nondimensionalized pressure does not change with varying axisymmetric flow distortions. However, the pressure dist ribution is very dependent upon the swirl. The axial momentum distribu tion is quantified by calculating the second-order moment of axial mom entum (R(2)[u]) from the velocity profile data. Swirl is quantified by determining the centripetal acceleration flux of the flow (Psi), also from the velocity profile data. Surface fits indicating the variation of discharge coefficient as a function of beta ratio and R(2)[u] Or P si are developed.