EFFECT OF THE UPSTREAM SHROUD PURGE FLOW ON THE COOLING PERFORMANCES OF TURBINE BLADE TIP

Researches on the turbine blade tip cooling mainly focus on the arrangement of the film holes in the blade tip and the shroud. In fact, the purge flow located upstream of the turbine blade leading edge also influences the cooling of the turbine blade tip region. In present study, the effects of purge flow on the cooling performance and flow field around the blade tip were investigated by numerical simulation using 3-D steady RANS approach with the k-ω turbulence model. The first-stage high-pressure turbine blade of GE-E³ was employed in present work. Three parameters of the purge flow were investigated, which were the inlet angle of the purge flow (30°, 60° and 90°), the relative position between the leading edge of the blade and the purge flow (10 %, 25 % and 40 % of the vane-blade distance), and the mass flow rate of the coolant (1 %, 1.5 % and 2 % of the main flow rate). The results indicate that the presence of the shroud purge flow has a significant influence on the film cooling of blade tip. As the inlet angle increases, higher vertical velocity reduces the lift-off of cooling jet, leading to worse tip cooling performance. However as the distance increases, the cooling performance improves. As the coolant flow rate increases, the cooling performance gets better.