Aerodynamic Performance Analysis of a Novel Geometry-variable Turbine Guide Vane with a Fixed Angle of Attack

A geometry-variable turbine technology effectively improves overall thermal-cycle performance of gas turbine engines under multiple operating conditions. The conventional variable turbine technology is rotating the entire vane airfoil to adjust airflow through the turbine passage. In such a way, the inlet angle of attack, however, is changed as well, which induces flow separation over the vane pressure or suction surfaces and thus results in aerodynamic penalty. To avoid excessive aerodynamic losses caused by the variable geometry, a one-way, adjustable geometry of low-pressure turbine guide vanes (flap-type adjustable guide vane) with a fixed angle of attack is proposed. The front portion of the vane is fixed, while the rear portion is rotated together with a rotating shaft, generating a gap between the front and the rear portions as well as a rotating gap at the upper and lower endwalls. This study explores the effects of shape parameters and closure angles on the aerodynamic performance of the vane passages. Results reveal that the newly-proposed configuration is superior to the conventional scheme in aerodynamic performance. At a closure angle of 7.3°, though the mass-flowaveraged total pressure losses at the vane outlet increases, the overall turbine-stage efficiency is higher relative to the conventional configuration. Within the structural parameters explored in this study, a maximum mass flow adjustment range of 20.48 % can be achieved.