Manufacturing influences on pressure losses of channel fed holes

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by micro-channels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of hole diameter to channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalk, and channel Reynolds number. Results showed that the friction factors for the typically long channels in this study, were independent of the inlet and exit hole configurations tested. Results also showed that the non-dimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the range tested. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.