Improvement of a Film-Cooled Blade by Application of the Conjugate Calculation Technique

The conjugate calculation technique has been used for the three-dimensional thermal load prediction of a film-cooled test blade of a modern gas turbine. Thus, it becomes possible to take into account the interaction of internal flows, external flow, and heat transfer without the prescription of heat transfer coefficients. The numerical models consist of all internal flow passages and cooling hole rows including shaped holes. Based on the results, deficiencies of the test configuration close to the leading edge region and in the blade tip region have been detected, which lead to hot spots and surface areas of high thermal load. These regions of high thermal load have been confirmed by thermal index paint measurements in good agreement to the conjugate calculation results. Based on the experimental and numerical results, recommendations for the improvement of the blade cooling were derived and an improved blade cooling configuration has been designed. The conjugate calculation results as well as new measurement data show that the changes in the cooling design have been successful with respect to cooling performance. Regions of high thermal load have vanished and effective cooling is reached for all critical parts of the test blade.