The Role of Laminar-Turbulent Transition in Gas Turbine Engines

Abstract

A critical study of laminar-turbulent transition phenomena and its role in aerodynamics and heat transfer in modern and future gas turbine engines is presented. In order to develop a coherent view of the subject, a current look at transition phenomena from both a theoretical and experimental standpoint are provided and a comprehensive state-of-the-art account of transitional phenomena in the engine’s throughflow components given. The impact of transitional flow on engine design is discussed and suggestions for future research and developmental work provided.

Growth of boundary-layer streaks due to free-stream turbulence

“…Although we have not conducted measurements in the transition region and therefore we have not computed the exact location of the beginning of the transition process, our last measurement location was upstream of predicted transition locations, i.e., Re θ,tr =169.5, obtained through the widely used correlation formula Re θ,tr = 400T u(%) −5/8 [34] and Re θ,tr =188.5, found by use of Re θ,tr = 460T u(%) −0.65 [19]. Figure 2.…”

“…The high-frequency disturbances therefore remain confined in the outer portion of the shear layer. As the breakdown mechanism is still unclear, prediction of transition subjected to free-stream turbulence for aeronautical and turbomachinery applications relies heavily on empirical models based mainly on experimental data [35,34,1].…”

High-resolution PIV measurements of a transitional shock wave–boundary layer interaction

“…Since turbulent interactions are more often found in flight conditions (Babinsky and Harvey 2011), most researchers have focussed their attention to this particular type of interaction. However, at high altitudes and thus low Reynolds numbers, it is not unlikely that parts of the boundary layer in, for instance, a jet engine are still in a laminar/transitional state (Mayle 1991).…”

Large eddy simulation of compressible transitional cascade flows

“…The boundary layer on the blade in such a turbine thus becomes transitional and unsteadiness of the cascade flows becomes evident. At the same time, the boundary layers are affected by the strong free-stream turbulence with about 5-20% intensity that originates in the combustion chamber or wakes of the upstream blade rows [1].…”