Crossflow Effect on Heat Transfer and Flow Characteristics of Simplified Double Wall Cooling Structure

Abstract

Double wall cooling is regarded as one of the advanced cooling technologies of modern gas turbines, but its internal cooling is always confronted with crossflow effect. To reveal the conjugate heat transfer characteristics under different crossflow configurations, this paper utilized ANSYS CFX to numerically simulate a double wall cooling model with staggered impingement holes and film holes. CFX numerically solves steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations. Both the overall cooling and internal heat transfer performance of four different crossflow mass flow ratios (CMFR = 0, 0.25, 0.5, 0.75) under four impingement jet Reynolds numbers (Rej = 15,000, 25,000, 35,000, 45,000) are compared in detail. The calculated results show that the CMFR has significant influence on double wall cooling performance. The averaged blowing ratio increases with the increase of jet Reynolds number under the same crossflow configuration, and it decreases with the increase of CMFR under the same impingement jet Reynolds number. The area-averaged Nusselt number decreases with the increase of CMFR at the CMFR ranging from 0.25 to 0.75, but the area-averaged overall cooling effectiveness increases with the increase of CMFR since better film coverage plays a dominated role in the enhancement effect of double wall cooling. In addition, the influence of solid thermal conductivity is also taken into consideration. It is revealed that solid thermal conductivity has great influence on double wall cooling. Under all crossflow configurations, the overall cooling effectiveness increases with the increase of solid thermal conductivity, but the increase rate slows down with the increase of thermal conductivity.