Adiabatic and conjugate cooling effectiveness analysis of a new hybrid scheme

摘要

The adiabatic film cooling effectiveness and flow characteristics for a new hybrid scheme and a circular hole were investigated numerically. The new film cooling scheme is proposed for high temperature gas turbine engines in aerospace and electric power generation applications. The hybrid scheme included two consecutive film hole configurations with interior bending to direct the secondary flow in stream-wise direction. The film cooling performance with flow-field analysis for the hybrid scheme and the circular hole were investigated at blowing ratio of 0.5, 1.0 and 2.0 for 0.95 density ratios. The results showed that the hybrid scheme provided a superior local and average film cooling effectiveness performance that was enhanced for further increase in blowing ratio. Moreover, the new scheme enhanced the downstream overall area-average film cooling effectiveness compared to the circular film hole. Subsequently, film cooling and conjugate heat transfer were combined to investigate the cooling effectiveness of the hybrid scheme at Br = 0.5 and 1.0 for different flow arrangements, specifically: parallel flow and jet impingement with two different gap heights (0.8 d and 1.2 d). The hybrid scheme presented a high cooling effectiveness by combining film cooling and conjugate heat transfer. The jet impingement configuration enhanced the upstream flow circulation which has a significant effect on convective heat transfer. Furthermore, a large gap height with jet impingement enhanced the downstream cooling effectiveness compared to other conjugate and adiabatic cases studied. The conjugate configuration with large gap height provided the highest overall laterally averaged cooling effectiveness compared to other conjugate and adiabatic cases studied. As a result, the hybrid scheme is able to minimize the cooling flow rate significantly since it provided superior cooling effectiveness at a lesser secondary flow rate, thus increasing overall engine efficiency.