The

This paper presents the results of an experimental investigation into the thermal and aerodynamic behavior of coolant ejection at the leading edge of a highly loaded nozzle vane cascade. The leading-edge cooling scheme features four rows of cylindrical holes in a staggered configuration (showerhead). Pressure Sensitive Paints (PSP) technique was used to get the adiabatic film cooling effectiveness distribution, while Particle Image Velocimetry (PIV) and flow visualizations were used to investigate the mixing process taking place between coolant and main flow. PSP tests were conducted by using N2 (Density Ratio DR=1.0) as coolant at variable blowing ratio (BR=2.0-4.0). Further tests were run by using CO2 (DR=1.5) at matching BR and momentum flux ratio (I) in order to investigate the effects of density ratio. The BR = 3.0 injection case was selected for the PIV investigation. Thermal and flow field data consistently show a shift in the position of stagnation line towards the suction side. Jet liftoff close to stagnation and a strong jet to jet as well as jet to mainstream interaction were also observed, resulting in a complex 3D flow characterized by high turbulence levels with a high degree of anisotropy. No coherent structures were detected, supporting the random nature of mixing process.

The present contribution is focused on heat transfer measurements on internal cooling channels of a high pressure gas turbine blade in static and rotating conditions.A

The contribution describes part of the work carried out on a wider research project aimed to set up a new tool to study rotational effects on the heat transfer distribution inside realistic cooling passages for gas turbine blades. Transient thermochromic liquid crystals (TLC) measurement technique is chosen in order to obtain spatially resolved heat transfer data. This obliges to perform the transient measurements with a cold temperature step on the coolant flow, in order to replicate correctly the buoyancy effects induced by rotation. This target is achieved by a new facility which components and working principle have been the subject of previous contributions. In the present paper, the progresses made in the development of the data processing methodology are described at first. Successively, a first step into the demanding rig and methodology validation process is commented by exploiting the results of a wide test campaign on a simple cooling channel geometry. KEYWORDS Internal cooling, rotation, liquid crystals, transient, gas turbine NOMENCLATURE Bo buoyancy parameter Ro rotation number cmat Plexiglas specific heat capacity e rib height Dh hydraulic diameter T0 initial temperature h heat transfer coefficient Tb bulk flow temperature H channel height Tw wall temperature K thermal conductivity Ub bulk flow velocity L channel length W channel width Nu Nusselt number ρ air density Nu0 reference Nusselt µ air dynamic viscosity P rib pitch Θ non-dimensional temperature R evaluation radius Ω rotational speed Re Reynolds number mat refers to material properties Ro rotation number air refers to air properties

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