On the Aerothermal Flow Field in a Transonic HP Turbine Stage with a Multi-Profile LP Stator Vane

Abstract

The quest for higher performances and durability of modern aero-engines requires the understanding of the complex aero-thermal flow experienced in a multi-row environment. In particular, the high and low pressure turbine components have a great impact into the engine overall performance, and improvements in the turbine efficiencies can only be achieved through detailed research on the three-dimensional unsteady aerodynamics and heat transfer. The present thesis presents an experimental study of the aerothermodynamics in one and a half turbine stage, focusing on: the aero-thermal flow in the overtip region of a transonic highly loaded high pressure (HP) rotor, and the aerodynamics and heat transfer of an innovative low pressure (LP) stator with a multi-profile configuration placed downstream of the high pressure turbine, within an s-shaped duct.

Advanced instrumentation and measurement techniques were used and developed to perform the experimental investigation in a short-duration turbine test rig where both high spatial and time accuracy is indispensable. The flow field at the rotor shroud was investigated with simultaneous measurements of heat transfer, static pressure and blade tip clearance by using fast response pressure, wall temperature and capacitance probes. Through repeat experiments at the same turbine operating point, the time-averaged and time-resolved adiabatic wall temperature and convective heat transfer coefficient were evaluated.

In the frame of new engine architectures, a novel stator for an LP turbine is proposed with a multi-splitter layout that represents a new design solution towards compact, lighter and performing aero-engine turbomachinery. It contains small aero-vanes and large structural aerodynamic airfoils which are used to support the engine shaft and house service devices. The research focuses on the experimental investigation of the global performance, aerodynamics and thermodynamics of this novel HP-LP vane layout. The turbine was