A Test Case for the Numerical Investigation of Wake Passing Effects on a Highly Loaded LP Turbine Cascade Blade

Abstract

The paper presents a compilation of experimental data on the effects of wake-induced transition on a highly loaded LP turbine cascade intended to be used for further numerical work. Although the underlying physics is not yet completely understood, the benefits of wake passing are already known and employed in the design process of modern gas turbines. For further optimizations, the next step seems to be now to enable numerical simulations detailed enough to capture the major effects while being as uncomplicated as possible at the same time to be cost-effective. The experimental results constituted in this systematic investigation are available for download and should serve as a basic data set for future calculations with different turbulence and transition models, thereby shedding some light on the complexity and modeling required for a suitable numerical treatment of the wake-induced transition process. The data introduced in this test case was acquired using a turbine cascade called T106D-EIZ with increased blade pitch compared to design point conditions in order to achieve a higher loading. A large separation bubble forms on the suction side and allows to study boundary layer development in great detail. The upstream blade row was simulated by a moving bar type wake generator. The measurements comprise hot wire data of the bar wake characteristics in the cascade inlet plane (velocity deficit and turbulence level), boundary layer surveys with surface-mounted hot films sensors and a hot wire probe at various locations and measurements of the total pressure loss coefficient. Unsteady pressure transducers are embedded into the suction side of a cascade blade and in a wake rake to resolve the local pressure distributions over time. They yield quantitative values easily comparable to the output of numerical simulations. The objective of this paper is to enable and to invite interested researchers to validate their code on the data set. From the extensive test program, a very limited number of operating points have been selected to focus the work. The standardized data files include a “reference” case with an exit Reynolds number of 200.000 and an exit Mach number of 0.4 as well as two points with higher Mach or lower Reynolds number for constant wake passing frequencies and background turbulence levels.