Prediction of the becalmed region for LP turbine profile design

Journal Article · Thu Oct 01 04:00:00 EDT 1998 · Journal of Turbomachinery

DOI:https://doi.org/10.1115/1.2841797· OSTI ID:316089

Schulte, V ^[1]; Hodson, H P ^[2]

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1. BMW Rolls-Royce GmbH, Dahlewitz (Germany)
2. Cambridge Univ. (United Kingdom). Whittle Lab.

Recent attention has focused on the so-called ``becalmed region`` that is observed inside the boundary layers of turbomachinery blading and is associated with the process of wake-induced transition. Significant reductions of profile loss have been shown for high lift LP turbine blades at low Reynolds numbers due to the effects of the becalmed region on the diffusing flow at the rear of the suction surface. In this paper the nature and the significance of the becalmed region are examined using experimental observations and computational studies. It is shown that the becalmed region may be modeled using the unsteady laminar boundary layer equations. Therefore, it is predictable independent of the transition or turbulence models employed. The effect of the becalmed region on the transition process is modeled using a spot-based intermittency transition model. An unsteady differential boundary layer code was used to simulate a deterministic experiment involving an isolated turbulent spot numerically. The predictability of the becalmed region means that the rate of entropy production can be calculated in that region. It is found to be of the order of that in a laminar boundary layer. It is for this reason and because the becalmed region may be encroached upon by pursuing turbulent flows that for attached boundary layers, wake-induced transition cannot significantly reduce the profile loss. However, the becalmed region is less prone to separation than a conventional laminar boundary layer. Therefore, the becalmed region may be exploited in order to prevent boundary layer separation and the increase in loss that this entails. It is shown that it should now be possible to design efficient high lift LP turbine blades.

• Sponsoring Organization: USDOE
• OSTI ID: 316089
• Report Number(s): CONF-970604--
• Journal Information: Journal of Turbomachinery, Journal Name: Journal of Turbomachinery Journal Issue: 4 Vol. 120; ISSN JOTUEI; ISSN 0889-504X
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
AERODYNAMICS
CALCULATION METHODS
DESIGN
GAS FLOW
GAS TURBINES