The reduction of cooling air for first stage turbine components plays a vital role in improving the performance of heavy-duty gas turbines. To achieve this goal detailed knowledge of the external heat loads is required as well as introducing novel technologies to reduce the cooling air consumption.

This paper gives an overview of the design considerations and validation for a technology upgrade of an Ansaldo Energia heavy-duty gas turbine first stage stator heat shield.

The heat transfer of the heat shield surface flow is influenced by the complex flow pattern that is created by the interaction of the rotating blade tip with the surface boundary layer, in the presence of leakage air and the wake of the upstream vane trailing edge. The present paper discusses results from CFD computations and laboratory experiments that investigate this interaction, as well as results from full scale engine tests. It is shown that both the wake of the upstream vane and the blade passing have a crucial influence on the heat transfer that needs to be considered during the design phase of the stator heat shield.

Furthermore, the implementation of a novel cooling concept with sequential impingement cooling from laboratory tests to engine ready technology is shown. A comparison of airflow measurements of the new heat shield with a conventional impingement design demonstrates a significant reduction in cooling air flow. Metal temperature measurements in full scale engine test with thermal paint, thermocouples and thermal crystals show similar metal temperatures compared to the conventional design.

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