Experimental research on aerodynamic performance of variable geometry low pressure turbine

To explore aerodynamic design plan of variable geometry turbine, the nozzle and rotor are designed to aft-loading blades, furthermore, rotor also is designed with negative incidence angle. The large diffused meridional flowpath is adopted in turbine to enhance output power. Test results are presented for the designed variable geometry turbine with nozzles different rotating angles. Comparisons are made between design and experimental results. The turbine mass flow ratio, efficiency, reaction and Mach number characteristics were studied at different nozzle rotating angles. At design condition, the relative corrected mass flow ratio of basic turbine is about 1.006, which meets design requirement. The basic turbine efficiency is 4.5% lower than design, the reason is also discussed. With nozzle opened or closed, the turbine mass flow ratio varies obviously, however, variation of efficiency is small, which will bring great benefits to the engine. Moreover, variation of efficiency is relatively flat with expansion ratio, which indicates the negative incidence angle and aft-loading blade design have obvious advantages to variable geometry turbine.