Conjugate heat transfer modeling of a turbine vane endwall with thermal barrier coatings

Abstract

Advanced cooling techniques involving internal enhanced heat transfer and external film cooling and thermal barrier coatings (TBCs) are employed for gas turbine hot components to reduce metal temperatures and to extend their lifetime. A deeper understanding of the interaction mechanism of these thermal protection methods and the conjugate thermal behaviours of the turbine parts provides valuable guideline for the design stage. In this study, a conjugate heat transfer model of a turbine vane endwall with internal impingement and external film cooling is constructed to document the effects of TBCs on the overall cooling effectiveness using numerical simulations. Experiments on the same model with no TBCs are performed to validate the computational methods. Round and crater holes due to the inclusion of TBCs are investigated as well to address how film-cooling configurations affect the aero-thermal performance of the endwall. Results show that the TBCs have a profound effect in reducing the endwall metal temperatures for both cases. The TBC thermal protection for the endwall is shown to be more significant than the effect of increasing coolant mass flow rate. Although the crater holes have better film cooling performance than the traditional round holes, a slight decrement of overall cooling effectiveness is found for the crater configuration due to more endwall metal surfaces directly exposed to external mainstream flows. Energy loss coefficients at the vane passage exit show a relevant negative impact of adding TBCs on the cascade aerodynamic performance, particularly for the round hole case.

Research on the flow field and film cooling effectiveness of the endwall with swirling film cooling

“…Many pioneers had conducted a large quantity of experiments and numerical calculations on the internal impingement and external film cooling cascaded endwall. First of all, Yang et al 19,20 performed experiments and numerical simulations of the conjugate heat transfer characteristics and cooling effectiveness of the internal jet impingement and external film cooling cascade endwall. They conducted a detailed comparison and analysis of the influence of mass flow ratios and Reynolds numbers for the cooling mechanisms.…”