[Objective

]

The cooling performance of conventional cylindrical film holes decreases dramatically under high blowing ratio conditions. The cooling characteristics of cylindrical film cooling holes can be improved by innovative design of the hole shape. [Methods

]

The method of Reynolds-averaged Navier-Stokes Equations(RANS) is applied for numerical analysis of cooling performance of step-shaped holes

and the results are then compared with that of the cylindrical hole. [Results

]

The results show that the cooling effectiveness of the step-shaped hole is better than that of the cylindrical hole

especially under high blowing ratio conditions. The cooling effectiveness of the step-shaped hole is improved by more than 100% under the condition that R

B

=1.0 or R

B

=1.5

relative to the cooling

effectiveness of the cylindrical hole. Additionally

the heat transfer coefficient of the step-shaped film cooling hole is smaller than that of the cylindrical hole

which is beneficial to restrain the heat load of the objective cooling wall. For the analysis of the geometry parameters effects

the cooling effectiveness of the step-shaped hole firstly decreases and then increases with the increase of length ratio R

L

and continuously increases with the increase of the diameter ratio R

D

. For the leading edge cooling of the rotor blade

the cooling effectiveness of the step-shaped holes on the blade body surface and blade tip surface is increased by 17.5% and 17.0% respectively compared with that of the cylindrical holes. When the step-shaped holes are applied

the maximum temperatures of the blade body surface and blade tip surface are reduced by 24.7 K and 14.1 K

respectively. Compared to cylindrical film cooling holes

the cooling performances of the blade body near the leading edge and in the mid-chord region on the pressure side are improved by the application of the step-shaped holes on the leading edge. For the blade tip

the adiabatic cooling effectiveness of the step-shaped holes in the shoulder region of the suction side and the middle region of the pressure side is superior to that of the cylindrical holes. The application of step-shaped holes makes the cooling effectiveness distribution of the blade body surface and blade tip surface more uniform

and significantly or the cooling effectiveness of the leading edge of the rotor blade without increasing manufacturing complexity and reducing blade strength. [Conclusion

]

The results can provide guidance for the application of step-shaped holes for the design of cooling structures of the gas turbine blades.