Development of an Integrated Lifting Strut and Outlet Guide Vane in a Compressor Transition Duct

Abstract To meet future environmental and economic targets aero gas turbines will require the development of new core engine technologies. In a multistage intermediate-pressure compressor an efficiency benefit may be gained by reducing reaction in the rear stages and allowing swirl to persist at the exit. However, this swirl must subsequently be removed within the compressor transition duct, situated between the intermediate and high-pressure compressor spools, to present the downstream compressor with suitable inlet conditions. This paper develops a validated numerical methodology and a design for a lifting strut integrated into the outlet guide vane row. This is applied to a transition duct representative of future, very high-pressure ratio, ultra-high bypass ratio turbofans. To mask the strut pressure field from the upstream rotor a three-dimensional cyclic stagger/camber of the outlet guide vanes is employed, matched to the complex pressure field incorporating both transverse and cyclic pressure gradients. The design was experimentally assessed on a fully annular test facility incorporating a 1½ stage axial compressor upstream of the transition duct. The results confirmed that the integrated design was successful (1) in removing residual swirl in preparation for the downstream compressor stage, (2) mitigating the strut potential field effects on the rotor and (3) permitting a potential reduction in overall system length.