Gas turbines and jet engines consist of a network of connected cavities beside the main gas path called the secondary air system. These cavities, which are often surrounded by stationary and high angular speed rotating walls are exposed to varying pressure and temperature levels of air or oil contaminated air and are connected to each other by orifices or restrictors. It is vital to control the secondary flow to enable a reliable and efficient engine design, which meets component durability with a minimum of parasitic air consumption. It is essential to understand the flow physics as well as network interdependency in order to minimize the flow consumption and yet meeting engine operating requirements, as well as practical parts component design or manufacturing needs. In this connection, computer network codes containing model conceptions, which can accurately predict orifice flows, are essential. In an effort to provide usable further insight into flows across restrictors, such as orifices, this publication compares test results and orifice loss calculation models from the open literature with the aid of transformation laws and contour plots. The influence of different geometric features is incorporated into a model for the calculation of discharge coefficients. This publication is an extract of the underlying widespread and more detailed ASME paper (Huening, 2008, “Comparison of Discharge Coefficient Measurements and Correlations for Several Orifice Designs With Cross-Flow and Rotation Around Several Axes,” ASME Paper No. GT2008-50976). Minor errors, noticed during adapting, are corrected.

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