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% 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% 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. Abbreviations BLboundary layer HL High Lift Mn Mach-number Re Reynolds-number Sr Strouhal-number Sr=f*l/Cax UHL Ultra High Lift Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 06/16/2015 Terms of Use: http://asme.org/terms

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

“…The absolute flow angle uncertainty varied between 0.2 and 0. 3 . Relative uncertainties on isentropic Mach number ranged between 0.4 per cent-1.2 per cent.…”

“…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].…”

Experimental and Numerical Investigations of Wake Passing Effects Upon Aerodynamic Performance of a LP Turbine Linear Cascade With Variable Solidity

“…Recently incoming wakes from the preceding blades and vanes are now being regarded as one of the promising remedies to avoid the loss increase induced by the separation or separation bubble. Accordingly, a lot of studies have been made to investigate the interaction of the incoming wakes with the separation bubble on the suction surface of LPT blades and some efforts among them successfully developed blade profiles and bladings for achieving ultra high lift (for example, Hodson et al [1], Halstead et al [2], Shulte and Hodson [3], Howell et al [4], Cardamone et al [5], Haselbach et al [6], Kalitzin et al [7], Stieger and Hodson [8] and Brear and Hodson [9]). Furthermore, a number of numerical works dealing with wake /blade interaction have been also published to date, using RANS [10], LES [11,12] or DNS [7,13].…”

Computational Study of the Impact of Unsteadiness on the Aerodynamic Performance of a Variable-Speed Power Turbine

“…At a given aerodynamic loading level, the loss levels in steady flows were found to be substantially (e.g., 20 percent) higher than when subjected to wake passing; further, the loss increase with Reynolds number lapse (sensitivity) was mitigated to some degree (Ref. 16). The impact of wake vorticity on the transitional blade and endwall flows was beyond the scope of the low-Re  turbulence models used in the present study work (Ref.…”