Active Aerodynamic Control of Multi-Stage Axial Compressor Instability and Surge by Dynamically Adjusting the Stator Blades

Abstract

A method of active aerodynamic control and prevention of axial compressor instability and surge is presented. The method is based on dynamically adjusting the stator blades to the compressor interstage unsteady aerodynamics. While concentrating on the active aerodynamic control and prevention of stall, it does not deal with control specific procedures and algorithms. Using a row-by-row dynamic prediction procedure, the dynamic state of the compressor is determined by the blade flow deflection, which is represented by a time dependent modified diffusion factor. For the case that an adverse dynamic operation condition causes the diffusion factor to exceed certain thresholds, the stator blades are adjusted by changing their stagger angle, thus shifting the surge limit beyond its design point. As a result, the compressor can operate at much lower mass flow rates than the steady state performance map allows. The active aerodynamic control method is applied to a single-spool, two shaft power generation gas turbine engine with a multistage compressor. Two complete dynamic engine simulation computations are performed. In the course of the first simulation, the stator-row stagger angles are kept at their design point and the compressor is forced into an unstable operating mode. In the second simulation, under the same adverse engine operation conditions, the stator blade rows are dynamically adjusted thus preventing the inception of instability and surge.