Effect of cooling hole structure on the steam cooling performance of the solid components (including the rotor blades, roots and wheel discs) in intermediate pressure turbine stages for an ultra-supercritical steam turbine was numerically investigated using the hybrid method of flow field calculation and conjugated heat transfer. Numerical solutions were carried out for four cooling hole structures, which includes a designed structure and three modified structures. Numerical results presented and compared the steam flow patterns in the disc cavities and temperature distributions in the rotating components for all cooling hole structures. Reducing through flow area of the cooling hole at the bottom of the blade root results in a significant strengthen in the preventing ability to hot main stream ingress of the cooling steam, as well as an increase in the cooling regions of the blade root and wheel disc. Furthermore, the overall solid temperature and temperature gradient can be efficiently reduced by modifying the cooling hole structure. Numerical results also reveal that it is possible to prevent the hot main steam ingress and increase cooling performance by modifying the steam cooling hole structure, which optimizes the flow pattern and flow rate distribution of the cooling steam.

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