Aero-thermal investigation of a multi-splitter axial turbine

Highlights: → Experimental heat transfer results in a multi-splitter low-pressure vane are reported. → Pneumatic taps and thin-film gauges are used in a short-duration rotating cascade. → Boundary layer status and transition are assessed at design and off-design conditions. → Good agreement with correlations for ducts allows detection of transition onset. → Time-resolved data explain the interaction of vanes with the upstream rotor. - Abstract: This paper reports the external convective heat transfer in an innovative low-pressure vane, designed with a multi-splitter configuration. Three aerodynamic airfoils are positioned in between larger structural vanes, replacing struts presently used in current aero-engines, which results in superior aerodynamic performance. Static pressure and heat flux measurements were carried out in the large compression tube facility of the von Karman Institute, using pneumatic taps and single-layered thin film gauges respectively. The steady and unsteady heat transfer distributions were obtained at representative conditions of modern aero-engines, with M2,is close to unity and a Reynolds number of approximately 106. This facility is specially suited to control the gas-to-wall temperature ratio that drives transition mechanisms. The heat transfer across the multi-splittered passages is confronted with correlations on ducts to further characterize the boundary layer status. The data will be used to guide code developers by verifying their boundary layer transition models, and designers by showing the areas of the vane where heat transfer is most sensitive to the off-design conditions.