PhD Thesis. Department of Mechanical Engineering at theRuhr-University Bochum, 2010. ISSN 1434-8454. Also: DLR-FB-2010-33.
Year of publication: 2010
In this work a method for reducing tip clearance flow losses at compressor rotors by a waved endwall contouring is presented. The approach is demonstrated at a simple optimization example.
The aerodynamic effects of the endwall contouring on the tip clearance flow and vortex are shown and discussed. The interaction between the axial velocity component and the waved endwall contouring produces a pressure field, which crucially modifies the formation and development of the tip clearance vortex. With the one-dimensional incompressible Rankine vortex model an analytical theory for axisymmetric endwall contouring is developed. The influence of swirl ratio, inflow Mach number and tip clearance height on how the endwall contouring physically works is explained and discussed on the basis of this theory.
Additional examples show the optimized endwall contouring for higher inlet Mach numbers and for a coupled optimization of a blade tip profile with the endwall contouring. Finally the results of the coupled optimization approach are successfully applied in a comprehensive CFD simulation of a Siemens gas turbine.