Numerical investigation of periodicity in adjustable guide vane sector cascade via clearance control

The adjustable guide vanes of variable-geometry turbines regulate flow capacity by rotating to change the blade installation angle, inevitably resulting in end gaps. To clarify the impact of tip clearances on both sides of an adjustable guide vane sector cascade on the periodicity of the flow passage, this study conducts a series of numerical simulations. The effects of the presence or absence of these gaps on flow periodicity and aerodynamic performance are analyzed. Using a specific turbine guide vane model, the study simulates different operating conditions by adjusting the blade angular displacement. It compares the periodic distribution of exit flow angle, total pressure loss coefficient, Mach number, mass flow rate, and aerodynamic torque in the central passage to quantitatively assess the effect of gaps on flow periodicity. The results indicate that eliminating the gaps significantly improves flow field stability and passage periodicity. This study reveals the mechanism by which gaps on both sides of the adjustable guide vane cascade disrupt flow periodicity, providing valuable insights for experimental design.