A numerical investigation is performed to illustrate the mutual interaction between coolant jet issuing from shaped film cooling hole and cascade primary flow as well as the resulting film cooling performance under rotational condition. Four various film-hole geometries are utilized for comparison, including the conventional cylindrical hole, fan-shaped hole, converging slot-hole and diffused slot-hole. Results show that a strong radial flow is induced toward blade tip on the pressure side due to the rotational effect, thus affecting the interaction mechanism between the coolant jet and primary flow. In general, rotational effects on film cooling are behaved as two aspects. On one hand, it makes the coolant jet deflect toward blade tip, resulting in lateral film coverage improvement in the region adjacent to the film holes for the cylindrical hole and fan-shaped hole relative to the stationary condition. On the other hand, it weakens the flow momentum of coolant jet along the streamwise direction, causing degradation of local film cooling effectiveness far from the hole-exit except for the zone near blade tip. The shaped-hole performs favorable film cooling enhancement, especially under higher blowing ratio. Relative to the stationary case, film cooling improvement by the film-hole exit shaping is degraded a little under the rotational condition. Among the presented shaped-holes, the converging slot-hole achieves the highest film cooling effectiveness and the diffused slot-hole is the next under the same blowing ratio.
2017 by The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan