The Additive Nature of Film Cooling From Rows of Holes

Abstract

A method of superposition which predicts the cumulative effect of film cooling has been described in the literature by Sellers. This method predicts the magnitude and extent of film cooling downstream of multiple injection stations by accounting for the effectiveness level from each upstream station individually. Sellers compared the method with results from multiple slots and good agreement was demonstrated. Because of the simplicity of the method it was proposed as a method to predict the cumulative effect of film cooling from rows of holes. To substantiate this, experiments were conducted with film cooling schemes on flat plates and airfoils. The results of these experiments demonstrate that the method is satisfactory for design of film cooled airfoils in the required range of geometries and coolant flows.

Heat Transfer in Film-Cooled Turbine Blades

“…Lander et al (1972) measured film cooling effectiveness in a cascade so as to include realistic geometry and flow conditions including free stream turbulence. Musaka et al (1975) confirmed the additive nature of the effectiveness of multiple rows of film cooling holes. Blair and Lander (1975) presented some techniques for measuring film cooling effectiveness.…”

Numerical Simulation of Single, Double, and Multiple Row Film Cooling Effectiveness and Heat Transfer

“…One of the most significant tests of the film cooling models contained herein is to apply it in conjunction with linear superposition to predict adiabatic wall effectiveness. This test was carried (12). Note that the 2-row data and the 4-row data for each M are plotted together for convenience.…”

A Computer Model for Gas Turbine Blade Cooling Analysis

“…T f = T r (1-n) + nT CF (12) The internal convective heat transfer coefficient (hi) for the central region of the blade is calculated using conventional correlations for forced convection through a smooth duct [9], rib-roughened duct [10], pinfin duct [9], and impingement cooling onto the inside surface of the leading edge [11]. The external heat transfer coefficients are calculated based on two physical models.…”

“…The second model assumes that downflow of the leading dege region of the blade, the heat transfer coefficient may be approximated by flow over a flat plate [9], instead of the actual air foil shape. For the film cooling efficiency (n), the additive method proposed by Muska, Fish, and Suo [12] is used for the calculation. Solution of this system (five equations, 6-10, and five unknowns) of equations has been included in the computer model as a subroutine which calculates for the blade outer and inner surface temperature in the pressure and suction side, coolant outlet temperature for a discrete duct element for any section of the blade, except the leading edge.…”