Optimization of a 180 Degree Bend for Internal Turbine Blade Cooling by Using the Ice-Formation Method: First Results

Abstract

This paper presents the first results of an approach for the optimization of a 180° bend used in internal cooling configuration of turbo-machinery components by applying the iceformation method. The iceformation method is based on a coupling between momentum and heat transfer and their interaction with a surface which consists of a solidified phase (ice layer). The investigated surface is cooled to temperatures below the freezing temperature of water and is therefore covered with an ice layer. Different cooling levels of the "parent surface" and different fluid flow velocities result in different contours of the ice layer which are determined from a local heat balance. The final shape of the ice layer at steady state conditions is determined by 2D optical measurement methods. The iceformation method provides a natural evolutionary approach to obtain contours that are optimized in terms of energy dissipation as have been shown in several studies by LaFleur [1–3]. The present study focuses on ice layer contours in a bend determined by experiments and classified with regards to thermal, flow, and geometrical constraints. In a further step, "good candidates" of the obtained surface contours can be parameterized and then used as starting geometries for numerical optimization by applying genetic algorithms in order to reduce pressure loss and to improve heat transfer performance. This procedure, using the iceformation method as a generator of new ideas, leads to larger solution ranges but also to "unusual results" and promising geometries compared to traditional optimization approaches. First results presented in this paper show those unusual and unexpected results in terms of ice layers shaping a separating web of a 180 degree bend by natural fluid flow. These ice layer contours even give a reduced pressure drop of 7% in this bend.