Peter Vass's PhD Thesis

In high pressure gas turbine stages, a source of significant losses is the leakage flow in the gap between the tip of the unshrouded rotor and the casing, called the tip clearance. In addition to that, the inlet temperature - which in modern high pressure turbines exceeds the melting point of the blade material – can cause serious damage, especially on the tip of the rotor blade, where cooling is rather difficult.
An adequately designed tip geometry is supposed to reduce the mass flow through the tip gap, and thus the losses and the heat transfer in the discussed region. The presented numerical study concerns a thorough aero-thermal investigation of tip leakage flows, applying the finite volume method on complete three dimensional models of a rotor blade, with four distinct tip configurations and film cooling. Three out of the four investigated geometries represent different tip design solutions; the fourth one portrays a typical eroded turbine blade tip geometry, after many hours of service.
The crucial point of the work was the grid generation, which is one of the most time-consuming phases of such projects. For this purpose, a scriptbased semi-automatized method was developed, with which the meshing session was significantly speeded up. The study also provides a comparison between the different geometries from the aerothermodynamic point of view, including the analysis of the losses and of the cooling effectiveness.

Jury :
Professeur Tony ARTS, promoteur (UCL)
Professeur Grégoire WINCKELMANS, promoteur (UCL)
Professeur Jean-François REMACLE, président (UCL)
Professeur Philippe CHATELAIN, secrétaire (UCL)
Professeur Patrick RAMBAUD (Institut von Karman, Belgique)
Professeur Pierre GINIBRE (SNECMA-Groupe Safran, France)