The Application of Ultra High Lift Blading in the BR715 LP Turbine

Abstract

The original LP turbine of the BR715 engine featured “High Lift” blading, which achieved a 20-percent reduction in aerofoil numbers compared to blading with conventional levels of lift, reported in Cobley et al. (1997). This paper describes the design and test of a re-bladed LP turbine with new “Ultra High Lift” aerofoils, achieving a further reduction of approximately 11 percent in aerofoil count and significant reductions in turbine weight. The design is based on the successful cascade experiments of Howell et al. (2000) and Brunner et al. (2000). Unsteady wake-boundary layer interaction on these low-Reynolds-number aerofoils is of particular importance in their successful application. Test results show the LP turbine performance to be in line with expectation. Measured aerofoil pressure distributions are presented and compared with the design intent. Changes in the turbine characteristics relative to the original design are interpreted by making reference to the detailed differences in the two aerofoil design styles.

Toward the Expansion of Low-Pressure-Turbine Airfoil Design Space

“…More engine-specific, high-lift work was presented by Haselbach et al [18] regarding the application of high lift to the BR715 LPT. The authors reported an increase in the measured performance differential between take-off and cruise conditions which was attributed to increased endwall losses.…”

“…Both the steady and unsteady flow behavior of this blade row have been investigated by several research groups (eg. [18]- [22], [24] [25]). The application of flow control to this airfoil has also been investigated.…”

An assessment of the laminar kinetic energy concept for the prediction of high-lift, low-Reynolds number cascade flows

“…In the multistage engine environment, the unsteady wake-induced transition plays a key role in reducing the separation effects up to a level compatible with acceptably low losses. Many studies demonstrate how high-lift [1,2] and ultra-high-lift [3,4] airfoils can be operated with loss control by taking advantage of wake-induced transition in LPT low-Reynolds, number flows. The study of wake-induced transition in LP turbines has thus led to improvements in performance of presentgeneration turbomachinery [5,6].…”

The Transition Mechanism of Highly-Loaded LP Turbine Blades

“…The advent of "Ultra High Lift" blades reported by Haselbach et al. [6] lead to a further reduction in the number of blades of 11%. However, such increases in blade loading were only possible when accompanied by the extensive experimental validation of Brunner et al [7], Howell et al [4] & [8].…”