Browsing by Author "Hettasch, Georg"
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- ItemOptimization of fir-tree-type turbine blade roots using photoelasticity(Stellenbosch : University of Stellenbosch, 1992-12) Hettasch, Georg; Endres, W.; Wettstein, H.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The large variety of turbo-machinery blade root geometries in use in industry prompted the question if a optimum geometry could be found. An optimum blade root was defined as a root with a practical geometry which, when loaded, returns the minimum fillet stress concentration factor. A literature survey on the subject provided guidelines but very little real data to work from. An initial optimization was carried out using a formula developed by Heywood to determine loaded projection fillet stresses. The method was found to produce unsatisfactory results, prompting a photoelastic investigation. This experimental optimization was conducted in two stages. A single tang defined load stage and a single tang in-rotor stage which modeled the practical situation. The defined load stage was undertaken in three phases. The first phase was a preliminary investigation, the second phase was a parameter optimization and the third phase was a geometric optimization based on a material utilization optimization. This material optimization approach produced good results. From these experiments a practical optimum geometry was defined. A mathematical model which predicts the fillet stress concentration factor for a given root geometry is presented. The effect of expanding the single tang optimum to a three tang root was examined.