Optimization of fir-tree-type turbine blade roots using photoelasticity

[摘要] ENGLISH ABSTRACT: The large variety of turbo-machinery blade root geometries inuse 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 surveyon the subject provided guidelines but very little real data to work from. An initial optimization was carried out using aformula developed by Heywood to determine loaded projection fillet stresses. The method was found to produce unsatisfactoryresults, 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 andthe 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 whichpredicts the fillet stress concentration factor for a given rootgeometry is presented. The effect of expanding the single tangoptimum to a three tang root was examined.

[发布机构] Stellenbosch University