Contribution of Tip Shroud Cavity to Loss Generation in the Main Flow of a Low Pressure Turbine Using Steady and Unsteady Numerical Approach
Abstract A lot of studies on turbomachinery main flow optimisation have been performed in order to reach current efficiencies. To go further in the study of aerodynamic losses sources, a better understanding of technological effects is required. Tip shroud cavities in low pressure turbine is an example. Indeed, the by-pass flow causes additional pressure losses. In addition, interactions between main flow and cavity flows, as well as the re-entering flow, cause mixing losses and modifications of flow angle. This paper investigates the contribution of tip shroud cavities in a low pressure turbine stage on the overall performance and flow structures. The ability of a steady simulation to predict this kind of flow by comparison with time-resolved results is poorly documented in the literature, and is an objective of this paper. Computations are compared with experimental data from low speed turbine test rig. Entropy production shows that a large amount of additional losses comes from the cavities themselves whichever the steady or unsteady treatment of the simulation. Additional losses generated in the rotor are more dependent on the presence of the shroud or not than the unsteady feature of the simulations.