Abstract
1.1. This investigation covers many aspects of flow measurement but is primarily devoted to the study of the performance of non-concentric orifice plates. The work can be grouped info three distinct categories:- (a) Further experiments on existing devices; (b) Introduction and development of new designs (c) Analysis of the effects of non-concentric location. 1.2. New experiments on existing devices comprise tests on eccentric and segmental orifice plates with the object of extending the range of useful application and resolving problems arising out of differences in design. Due, in some measure, to this additional work the eccentric orifice plate is now the most comprehensively researched non-concentric device; it can be used with confidence within the recommended range and will be incorporated into the National Standard. 1.3. Although some of the uncertainties ascribed to the segmental orifice have been resolved in this work, by an extensive investigation, its overall performance remains disappointing and the device is likely to be superceded by new designs. 1.4. Two new designs, the elliptic and the semi-circular, have been introduced by the writer and the development work on these orifice plates constitutes the central core of this thesis. The object of this programme was to create an orifice which would combine the reliability of the eccentric orifice with a clear passage for entrained solids provided by the segmental device. From this standpoint the semi-circular orifice which has characteristics very similar to the segmental device, has not been a success. 1.5. In pleasing contrast the performance of the elliptic orifice has exceeded all expectations. Amongst its many merits are a completely free passage for entrained solids, good repeatability of flow indication and a range of accurate flew measurement even wider than that for the standard, concentric orifice. 1.6. The experimental programme, designed to analyse the influence of eccentric location on the performance of orifice plates, has been restricted to devices with circular apertures. A variable eccentric orifice has been designed which allowed a comprehensive survey to be made from a concentric to a fully eccentric position, for different area ratios, using only one orifice. ln practical terms, this investigation yielded useful results on errors connected with faulty installation of standard orifices, which would suggest that some of the relevant data specified in the new International Standard are incorrect. 1.7. New analysis of the effect of pipe roughness, asymmetrical velocity profiles and orifice eccentricity are combined in support of the theory on the correlation of upstream velocity distribution and discharge coefficient values of orifice plates.