Improving the Film Cooling of a Rotor Blade Platform

This paper shows the results of an experimental activity developed in cooperation between Ansaldo Energia and the Department of Engineering and Applied Science of Bergamo University with the aim of assessing the impact of newly designed holes on the thermal protection of a rotor blade platform. The original rotor blade platform featured 10 cylindrical holes located along the blade pressure side. Moreover, the channel front side was cooled exploiting the seal purge flow exiting the stator to rotor interface gap. The front mid channel, and particularly the region around the inter-platform gap, remained uncooled. To protect this region two sets of cylindrical holes were designed and manufactured on a 7 blade cascade model for experimental verification. Aerodynamic and thermal tests were carried out at low Mach number. To evaluate the interaction of injected flow with secondary flows a 5hole probe was traversed downstream of the trailing edge plane. The thermal behavior was analyzed by using Thermochromic Liquid Crystals technique, so to obtain film cooling effectiveness distributions. The 7-hole configuration coupled with a low blowing ratio of about 1.0 provided the best thermal protection without any impact on the aerodynamic performance.