Correlations for the discharge coefficient of rotating orifices based on the incidence angle

Abstract

The flow through rotating orifices is of interest to the designer of machines incorporating such features. The designer often requires a set of correlations which can be used to check out preliminary designs and converge on a solution prior to attempting detailed and expansive analysis. The correlations given in this paper are based on the incidence angle, i, of the flow into the orifice and they allow the discharge coefficient for rotating orifices to be estimated for as many conditions and geometries as possible. The approach adopted is to group the parameters that affect the discharge coefficient to i = 0° (Reynolds number, orifice chamfer and radius, L/d ratio, pressure ratio, and pumping effect) and i ≠ 0° (rotation of the disc, preswirl, cross-flow, and the angle of inclination of the orifice). The effect of each parameter on the discharge coefficient can easily be observed when using this method. Furthermore, the method can predict the discharge coefficient for systems that have various parameters that are combined together. There is a good agreement between the correlations and the experimental results and the available data on rotating orifices in the open literature. The correlations also agree with various combinations run in computational fluid dynamics (CFD). The approach adopted in this paper, which is based on the incidence angle, can assist designers to find the combination of geometric and flow parameters that gives the best discharge coefficient for rotating orifices.