Investigation of Internal Flow Mechanisms and Loss Characteristics in Novel Variable-Shape Turbine Blade

Variable geometry turbines (VGTs), as critical components of variable cycle engines, traditionally employ adjustable vane installation angles for off-design operation. However, significant deviations from design conditions induce substantial losses due to large angle-of-attack variations. This study proposes a novel adjustable design with a fixed leading edge and rotatable trailing segment, investigating flow dynamics and loss mechanisms under varying pivot positions and rotation angles via experimentally validated numerical simulations. Results demonstrate a maximum flow adjustment range of -36.1% to +21.7% within a rotation span of -15 ° to 30°. Positive rotations enhance flow rate by expanding throat area but trigger flow reduction beyond 30 ° due to throat contraction, with forward pivot positions amplifying flow sensitivity. Positive rotations increase profile losses through heightened separation bubble height and axial extension on suction surfaces, while narrowing high-loss regions via merging of trailing-edge shedding vortices (FV) and leakage vortices (LV). Conversely, intensified negative rotations expand passage vortex (PV) dominance and leakage proportion, exacerbating secondary flow losses. Rearward pivot positions delay separation onset, increasing separation bubble dimensions at +5 ° rotation. Positive rotations with rearward pivots enlarge high-total-pressure-loss zones and secondary turbulent kinetic energy through enhanced transverse adverse pressure gradients, whereas negative rotations suppress secondary flow diffusion by aligning PV and LV, reducing leakage and turbulence intensity. This work elucidates the internal flow mechanisms of the innovative design, providing theoretical foundations for optimizing wide-range VGTs.