ROTATIONAL AND SHOWER HEAD COOLING HOLE EFFECTS ON LEADING-EDGE JET IMPINGEMENT HEATTRANSFER

摘要

Jet Impingement and shower head cooling are critical cooling techniques used to maintain turbine blades at operational temperatures. Jet impingement is extremely effective at removing large amounts of heat from the target surface, the inner blade wall, through stagnation point heat transfer. Shower head cooling produces a cooling film around the exterior of the blade, in return reducing external heat transfer. For validation studies and design predictions, the modeling of rotational effects is critical and has been a challenge for eddy viscosity turbulence models. The current work consisted of investigating the jet impingement effectiveness with rotational effects for two different cooling flow rates at various rotational speeds. The analysis was conducted using STAR CCM+ with the three equation Lag Elliptic Blending K-Epsilon eddy viscosity turbulence model. The blade used was NASA/General Electrics E~3 row 1 blade. The model consisted of a quarter of the blade-span to reduce computational expense and only one jet was analyzed. A flow field analysis was performed on the free jet region to analyze the potential core velocity and turbulent kinetic energy profiles. Nusselt Number spanwise distribution and external blade temperature profiles were also evaluated. The investigation showed that rotational effects produce turbulent kinetic energy within the jet's potential core. Maximum Nusselt Number was achieved when Coriolis forces were equivalent to centrifugal forces. A mathematical expression for the previous statement is the tangential component of jet velocity is equal to one half of the product of rotational speed with radius from engine centerline, v_j(^e)_θ = (Ωr)(^e)_θ/2.