1999 Turbomachinery Committee Best Paper Award - Development of advanced compressor airfoils for heavy-duty gas turbines - Part II: Experimental and theoretical analysis

In Part I of this paper a family of numerically optimized subsonic compress or airfoils for heavy-duty gas turbines, covering a wide range of flow prop erties, is presented. The objective of the optimization was to create profi les with a wide low loss incidence range. Therefore, design point and off-d esign performance had to be considered in an objective function. The specia l flow conditions in large-scale gas turbines have been taken into account by performing the numerical optimization procedure at high Reynolds numbers and high turbulence levels. The objective of Part II is to examine some of the characteristics describing the new airfoils, as well as to prove the r eliability of the design process and the flow solver applied. Therefore, so me characteristic members of the new airfoil series have been extensively i nvestigated in the cascade wind tunnel of DLR cologne. Experimental and num erical results show profile Mach number distributions, total pressure losse s, flow turning, and static pressure rise for the entire incidence range. T he design goal with low losses and especially a wide operating range could be confirmed, as well as a mild stall behavior. Boundary layer development, particularly near stall conditions, is discussed using surface flow visual ization and the results of boundary layer calculations. An additional exper imental study, using liquid crystal coating, provides necessary information on suction surface boundary-layer transition at high Reynolds numbers. Fin ally, results of Navier-Stokes simulations are presented that enlighten the total pressure loss development and flow turning behavior, especially at h igh incidence in relation to the results of the design tool. [S0889-504X(00 )02602-7].