Shock Wave Boundary Layer Interaction in Profile Cascades Representing Rotor Bladings of the Last Stage of Large Output Steam Turbines

Abstract

This paper is mainly focused on selected interaction phenomena occurring in the root, middle and tip section of the last stage rotor blading consisting of titanium blades Doosan Skoda 1375mm (54") and steel blades Doosan Skoda 1220mm (48"). Measurements and CFD simulations of the flow in selected sections along the blading radius show different types of interaction. Typically for the parts of the blade closer to the hub, only interaction of internal branch of exit shock wave with the suction side boundary layer takes place. At the blade tip where the flow is supersonic at both inlet and outlet, interaction of internal branch of inlet shock wave with the pressure side boundary layer occurs. The "reflected", additional shock wave arising from this interaction affect the flow field close to the suction side of the adjacent profile. The structure of interaction often depends on the flow conditions (nominal conditions and off-design conditions of flow, incl. different inlet flow angles).

Effect of inlet turbulence on compressible flow through the tip-section turbine blade cascade with supersonic inlet

“…At higher inlet Mach number this inlet shock wave is to that extent curved that it pasts the suction side of the previous blade and propagates downstream, see Luxa et al [18].…”

Numerical simulations of the 2D supersonic flow through the tip-section turbine blade cascade with a flat profile

“…The used blade configuration leads to considerable changes of the flow structure changes in the blade cascade at a small change of inlet flow conditions. The flow structure is affected mainly by the interaction of the exit shock wave with the shear layer on the suction side of the adjacent blade and by the interaction of the inlet shock wave upstream the blade leading edge with the shear layer on the pressure side of preceding blade, see Luxa et al [8].…”