Abstract
Jet impingement is used to efficiently cool gas turbine blades and other engine components. However, jet-to-jet interactions result in the accumulation of crossflow as the spent air migrates downstream, which usually causes a decay in the Nusselt number and reduces the overall cooling performance. In this study, several crossflow mitigation techniques are investigated by attaching small and easy-to-manufactured crossflow diverters to protect jet cores from upstream crossflows and, therefore, enhance heat transfer performance. Three diverter shapes of cylindrical, rectangular, and ribbed type are studied within a 25-jet array under laminar and turbulent flow regimes (Rej of 2,500–10,000). Three-dimensional Navier-Stokes (N-S) equations are solved under the k-ɛ turbulence model following a mesh sensitivity study. Diverter heights of 25%, 50%, and 75%, as a percentage of jet-to-target spacing denoted as quarter-length (QL), half-length (HL), and three-quarter-length (TQL), respectively, are considered with a constant heat flux condition. Results show an increase in average Nusselt number values from 6.6% to 12% achieved by a TQL cylindrical-shaped diverter. However, the associated friction factor is also increased by 9.9%–24.3% on average compared to the baseline model. Nevertheless, the heat transfer performance parameter (η) is introduced to quantify the desired gain in Nu and the cost in the pressure loss. Consequently, results show a net enhancement of up to 5.2%, 3.1%, and 3.8% for cylindrical, rectangular, and ribbed-type diverters, respectively.
