Measurements on rotating blades using IR thermography

This paper presents an experimental and CFD numerical study of convective heat transfer and flow field characteristics in a rotating rotor cascade. Surface temperature distribution on a rotating heated blade was measured by means of infrared thermography, which proved highly advantageous over standard temperature sensors due to its completely non-intrusive nature. The experimental facility, IR thermography method, and the CFD numerical model that was made according to the actual test rig geometry and operating conditions, are described in detail. For the present study, tests were carried out in an iposonic flow regime at relatively low fluid temperatures, with the Rotational number varied and hot-to-cool air mass flow ratio and Reynolds number kept constant. Experimental and numerical results for the blade pressure side were found to be in good agreement. Analysis of the results focused on the influence of rotation and black paint thermal conductivity on heat transfer through the blade. The results, presented in terms of Nusselt number distribution along the blade midspan, show the influence of rotational number on convective heat transfer. Interpretation of numerical results showed that the black paint coating imposes additional thermal resistance to heat conduction, which can affect temperature distribution on the painted surfaces. With increasing rotational number and all other influential parameters kept constant, heat transfer intensifies, which is reflected in increased Nusselt numbers along the blade midspan.