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Design and optimization of an efficient internal air system of a gas turbine requires thorough understanding of the flow and heat transfer in rotating disc cavities. The present study is devoted to numerical modelling of flow and heat transfer in IntroductionImprovements in material properties of gas turbine components and the use of cooling air allow engines to operate at higher pressure ratios and higher gas temperatures thus yielding higher thermal efficiency. The reliance on cooling air makes the secondary air system one of the most critical sections of a gas turbine. The optimum design of these systems maximizes the engine performance and life, and varies depending on the applications (power turbines or jet engines), models and manufacturers. Rotating disc cavities are an important element of engine cooling air systems. As in the review by Owen & Wilson [1] these disc cavities are broadly classified into rotor-stator, co-rotating

The present study focuses on the effect of nozzle exit inclination on the mixing characteristics of Mach 2.17 overexpanded jets at the NPR 5, NPR 6 and NPR 7, using commercial software package ANSYS Fluent. The convergent-divergent nozzles, investigated are circular nozzle and bevel nozzle with bevel angle 300, and bevel angel 450. The nozzles are constructed with equal throat-to-exit area ratio, in order to maintain uniform Mach number at the nozzle exit. From the results, it was found that, the bevelled nozzles effectively reduce the jet core as much as 46%, indicating enhanced jet mixing. It was also observed that at lower NPR, i.e., at NPR 5, the Bevel30 nozzle is found superior over Bevel45 and circular nozzle and at the intermediate NPR, both of the Bevel30 and Bevel45 nozzle reduces the jet core with the same rate. However, at highest NPR of the present study, the Bevel45 nozzle exhibits the highest mixing enhancement. An early axis switching is seen for the Bevel30 jet at NPR 5 and for the Bevel45 jet at NPR 7.

Design and optimization of an efficient internal air system of a gas turbine requires thorough understanding of the flow and heat transfer in rotating disc cavities. The present study is devoted to numerical modelling of flow and heat transfer in IntroductionImprovements in material properties of gas turbine components and the use of cooling air allow engines to operate at higher pressure ratios and higher gas temperatures thus yielding higher thermal efficiency. The reliance on cooling air makes the secondary air system one of the most critical sections of a gas turbine. The optimum design of these systems maximizes the engine performance and life, and varies depending on the applications (power turbines or jet engines), models and manufacturers. Rotating disc cavities are an important element of engine cooling air systems. As in the review by Owen & Wilson [1] these disc cavities are broadly classified into rotor-stator, co-rotating