Journal of Thermal Science Vol.23, No.1 (2014) 112 Received: September 2013 Francesca SATTA, Daniele SIMONI: Assistant Professors; Marina UBALDI, Pietro ZUNINO: Professors www.springerlink.com DOI: 10.1007/s11630-014-0671-0 Article ID: 1003-2169(2014)01-0001-12 Aerodynamic Loading Distribution Effects on the Overall Performance of Ul- tra-High-Lift LP Turbine Cascades M. Berrino 1 , F. Satta 1 , D. Simoni 1 , M. Ubaldi 1 , P. Zunino 1 , F. Bertini 2 1. DIME – Università degli Studi di Genova, Via Montallegro 1, I-16145 Genova, Italy 2. Avio S.p.A., Viale I Maggio 56, I-10040 Rivalta (TO) - Italy © Science Press and Institute of Engineering Thermophysics, CAS and Springer-Verlag Berlin Heidelberg 2014 The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both profile and secondary losses in the aero-engine LP turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading (Zw=1.03), has been compared with two Ultra-High-Lift profiles with the same Zweifel number (Zw=1.3 for both cascades), but different velocity peak positions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been experimentally in- vestigated for Reynolds numbers in the range 70000<Re<300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency f + =0.62 on both profile and secondary flow losses for the three different cascade designs have been studied. Total pressure and velocity distributions have been measured by means of a miniaturized 5-hole probe in a tangential plane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic performance of the blade cascades in terms of profile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When operating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest profile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are present. Keywords: Low-Pressure Turbine, Ultra-High-Lift Profiles, Profile Losses, Secondary Losses, Mid-Loaded Blade Cascades, Aft-Loaded Blade Cascades. Introduction Viscous effects acting on the flow developing within turbine rows are the main source for both profile and secondary flow losses in the case of subsonic flow [1]. Profile losses are generated within the boundary layers growing along the blade surfaces, whereas secondary losses are induced by the vortical structures originating in the endwall proximity (i.e. passage and horse shoe vor- tices). Profile losses are mainly due to the suction side bound- ary layer, especially at the low Reynolds number condi- tion characterizing the cruise phase of Low-Pressure- Turbine (LPT) blades, which can be affected by bound-