A NUMERICAL ANALYSIS OF CROSS-FLOW REINFORCED IMPINGEMENT COOLING WITH A U-SHAPED FLOW-GUIDE ON THE HOLE PLATE

Abstract

Impingement cooling offers an efficient usage of cooling air in order to obtain high heat transfer rates. In this study a U-shaped turbulator is installed downstream of the jet hole. This arrangement uses the cross-flow to reinforce the jet by guiding it into the adjacent jet and thus increasing its effective jet Reynolds number. Compared to a smooth channel configuration, the Nusselt number on the target can be increased by 5-16% without a significant change in the pressure loss. This is a purely aerodynamic effect and is not caused by increasing the area of the heat exchanging surface. The geometry represents a generic impingement cooling configuration with a row of nine inline impingement jets. All jets are influenced by a self-induced cross-flow. The jet-to-plate spacing as well as jet pitch are set to 5D and the curved U-shape ribs are installed downstream of the jet on the hole plate. The RANS simulations are performed with the SST turbulence model. The effects of different jet-to-plate spacing, jet Reynolds number as well as rib height, position and shape are investigated numerically. The effectiveness of the U-shaped turbulator is discussed in combination with additional turbulators (from the literature). This paper concludes with a recommended set of rib and impingement parameters for the usage of the U-shaped turbulator in gas turbine cooling designs. A discussion of the manufacturability by Selective Laser Melting is included