Discharge Coefficient of Turbine Cooling Holes: A Review

Abstract

Published information on the discharge coefficient of film cooling holes is classified in terms of the hole geometry, the external flow conditions at inlet and outlet, and the method of evaluation. This may be either theoretical or experimental. The information is reviewed primarily in the context of its use for evaluating discharge coefficients for conditions not directly covered by published data. It is shown that potential flow analyses can give acceptable accuracy for simple geometries with crossflows, while more complex cases require the use of correlated data, which may be incorporated in a range of predictive schemes. Deficiencies and inconsistencies in the published information are highlighted, and future developments are discussed.

Influence of turbulators in blade cooling passages on film hole discharge coefficients

“…Recent investigations [2] clearly showed, that in this special case the film hole Ca-values are also a function of the external flow. A summary of all the experimental, analytical and numerical work, which had been done until 1998, is published in [6]. In [5] the influence on Ca-values caused by the film hole orientation relative to the main flow direction in the coolant passage is described.…”

Cooling of a permanent magnet electric motor with a centrifugal impeller

“…A new analytical method was developed to provide results with simple calculations. Hay et al [14] presented a fundamental heat transfer correlations that could be used in motor thermal design. Lee et al [15] developed an algorithm for the thermal analysis of an open-type induction motor with forced cooling channels in the rotor and stator.…”

“…In the motors employed in household and industrial appliances, it is not practical to apply such cooling techniques due to the safety, maintenance, and cost reasons. To date, the majority of electric motors still employ air cooling [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The published efforts found in the literature on motor air cooling can be categorized into the following three classes: (1) theoretical effort on heat transfer analysis, (2) summary on design experience, and (3) research on cooling and heat transfer enhancement.…”

Velocity pick-up and discharge coefficient for round orifices with cross flow at inlet

“…For example, the discharge coefficient for flow through holes normal to a rotating shaft [4][5], compound-angle conical holes with cross-flow [6], axial orifices in a rotating disk [7], short orifices with radiused and chamfered inlet [8] are investigated recently. Hay et al [9] gave a review of discharge coefficient of turbine cooling holes and some methods correlating the discharge coefficients are reported by some researches [10][11][12]. In addition to discharge coefficients, some flow characteristics have been reported to explain orifice flow behaviour or describe specific phenomena.…”