Measurement of Internal Heat Transfer Distribution of Highly-Loaded Gas Turbine Blade by Combined Experimental/Numerical Method

Department of Industrial Engineering, University of Florence, 50139, via S.Marta 3, Florence, Italy

^* e-mail: asif.ali@unifi.it

Abstract

To ensure a passable life span of gas turbine hot gas path components the measurement of metal surface temperature is paramount. Experimental analyses on internally cooled devices are often performed on simplified or scaled up geometries, which reduces the applicability of the results to the actual real hardware. A more reliable estimation of cooling performance could be obtained if the real engine component is directly studied. To achieve this goal, an experimental campaign is performed to investigate the internal heat transfer distribution of an industrial blade, cooled by means of an internal U-shaped channel. During the experiment the blade is heated to a known temperature, then a coolant is introduced through the internal channel to induce a thermal transient, during which the external surface temperature is measured with the help of an infrared camera. Then a transient thermal finite element simulation is performed with the same boundary and inlet conditions of the experiment. Based on the output of the simulation, the internal heat transfer distribution is updated until convergence between simulation output external temperature and the experimental temperature is achieved. In order to start the iterative procedure, a first attempt estimation of the internal heat transfer distribution is obtained with a lumped thermal capacitance model approach. Different experiments were performed with different mass flow rates and the results are compared with available literature data. The obtained results allow to observe detailed heat transfer phenomena, strongly bound to the relevant features of the actual real cooling system.