Aerothermal Performance of Shroudless Turbine Blade Tips with Relative Casing Movement Effects

Qualitatively different heat transfer characteristics between a transonic blade tip and a subsonic one have recently been discovered. High-resolution experimental data can be acquired for blade-tip heat transfer research using a high-speed linear cascade. A combined experimental and computational fluid dynamics study on several high-pressure turbine blade-tip configurations is conducted to understand the flow physics in both stationary and moving casing setups. Extensive tests measuring aerodynamic loss and heat transfer have been performed on a stationary squealer tip at engine-representative aerodynamic conditions. A systematic validation of the computational fluid dynamics solver (Rolls–Royce, plc. HYDRA code) is introduced, showing good agreement with the experimental data obtained. Relative casing movement effects are then evaluated for two tip configurations at three different tip gaps. The moving casing is shown to affect the aerothermal performance considerably; the trends are consistently captured for the large and medium tip gaps, both in the stationary and moving casing instances. Presented results confirm that, even with a moving casing, the blade tips remain transonic. It is also shown that the heat transfer is not only dependent on the tip gap size but also the tip-geometry configuration. The squealer cavity is subsonic regardless of the tip gap size, whereas the local flow state over a flat tip is much more responsive to tip gap size

Nonlinear Time and Frequency Domain Methods for Multirow Aeromechanical Analysis

An unsteady Navier–Stokes solution system for aeromechanical analysis of multiple blade row configurations is presented. A distinctive feature of the solver is that unified numerical methods and boundary condition treatments are consistently used for both a nonlinear time-domain solution mode and a frequency-domain one. This not only enables a wider range of physical aeromechanical problems to be tackled, but also provides a consistent basis for validating different computational models, identifying and understanding their relative merits and adequate working ranges. An emphasis of the present work is on a highly efficient frequency-domain method for multirow aeromechanical analysis. With a new interface treatment, propagations and reflections of pressure waves between adjacent blade rows are modeled within a domain consisting of only a single passage in each blade row. The computational model and methods are firstly described. Then, extensive validations of the frequency-domain method against both experimental data and the nonlinear time-domain solutions are described. Finally, the computational analysis and demonstration of the intrarow reflection effects on the rotor aerodynamic damping are presented