Unsteady wake-induced boundary layer transition in high lift LP turbines
- Univ. of Cambridge (United Kingdom). Whittle Lab.
The development of the unsteady suction side boundary layer of a highly loaded LP turbine blade has been investigated in a rectilinear cascade experiment. Upstream rotor wakes were simulated with a moving-bar wake generator. A variety of cases with different wake-passing frequencies, different wake strength, and different Reynolds numbers were tested. Boundary layer surveys have been obtained with a single hot-wire probe. Wall shear stress has been investigated with surface-mounted hot-film gages. Losses have been measured. The suction surface boundary layer development of a modern highly loaded LP turbine blade is shown to be dominated by effects associated with unsteady wake-passing. Whereas without wakes the boundary layer features a large separation bubble at a typical cruise Reynolds number, the bubble was largely suppressed if subjected to unsteady wake-passing at a typical frequency and wake strength. Transitional paths and becalmed regions, induced by the wake, dominated the boundary layer development. The becalmed regions inhibited transition and separation and are shown to reduce the loss of the wake-affected boundary layer. An optimum wake-passing frequency exists at cruise Reynolds numbers. For a selected wake-passing frequency and wake strength, the profile loss is almost independent of Reynolds number. This demonstrates a potential to design highly loaded LP turbine profiles without suffering large losses at low Reynolds numbers.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 290072
- Report Number(s):
- CONF-960608--
- Journal Information:
- Journal of Turbomachinery, Journal Name: Journal of Turbomachinery Journal Issue: 1 Vol. 120; ISSN JOTUEI; ISSN 0889-504X
- Country of Publication:
- United States
- Language:
- English
Similar Records
An investigation of boundary layer development in a multistage LP turbine
Development of blade profiles for low-pressure turbine applications