Film cooling characteristics of trench hole were measured using a transient liquid crystal full-surface measurement technique.The influence of momentum flux ratio (I=0.5

1

2

4) and trench depth (s=0.5 D

0.75D

D;D stands for film hole diameter) were studied comparison between trench hole and cylindrical hole was conducted.The results show that the trench suppresses coolant jet separation

and the trench hole provides greater lateral film coverage compared with the cylindrical hole.An optimum trench depth is s=0.75 D.With a further increase in momentum flux ratio

the cooling effectiveness levels start to plateau

so increased coolant would not be warranted because only a slight increase in film cooling effectiveness would occur.