Conference paper

Head loss coefficient through sharp-edged orifices

Nowadays, high-head power plants could increase their installed power capacity for many reasons, e.g. dam heightening, increase of their peak power capacity or refurbishment with new turbines. Frequently, due to several considerations, e.g. topographical or economical limitations, the existing surge tank cannot be extended to keep previous safety levels and e_ciency. A valuable way to adapt these surge tanks is to place a throttle at their entrance like, for example, an ori_ce. The main e_ect of this adaptation is the introduction of head losses that reduce the extreme levels in the surge tank due to the mass oscillations resulting from a closure or opening of downstream discharge control. This research studies the inuence of the edge angle of a ASME-standard ori_ce on the head losses. This angle introduces an asymmetrical behavior and inuences head losses. Di_erent angles are tested from 0_ to the 67_ (biggest angle possible for this con_guration). The _rst step of this study is to determine experimentally the steady losses produced by ori_ce for several discharges. In the second step, a numerical model on ANSYS CFX is performed. Combining the two approaches, it is possible to understand and quantify the e_ect of the edge angle.

Related material