Reduction of Bleed Valve Bandwidth Requirements for Control of Rotating Stall using Continuous Air Injection

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Simon Yeung and Richard M. Murray
1997 Conference on Control Applications

This paper describes a technique for reducing the actuator rate requirement in active control of rotating stall and surge on compressors. Actuation of the compressor characteristic, via the use of continuous air injection at the rotor face in a single-stage, low speed axial compressor, has been experimentally verified to provide a method of reducing the actuator rate requirement of bleed valve control of rotating stall. With a compressor rotor frequency of 100 Hz, active control of stall with a high speed bleed valve is achieved only when the compressor characteristic is actuated. Furthermore, the experiments show that the bleed valve rate requirement is reduced from approximately 145 Hz to below 10 Hz when the amount of compressor characteristic actuation is increased. Theoretical tools based on a low order model (1-3 states) and simulations based on a reduced order distributed model (37 states) have been developed to estimate the gain and rate requirements of the bleed controller. All of the analytical formulas and simulations share the same qualitative trends with respect to the second and third derivatives of the compressor characteristic function evaluated at the peak, and the experiments. The agreement implies that bleed valve control of rotating stall depends crucially on the rate limit of the bleed valve which in turn depends on both the stable and the unstable part of the compressor characteristic. Actuation of the compressor characteristic is concluded to be a valuable tool in circumventing the rate limitation of bleed valves for control of stall. By combining the compressor characteristic identification tools and the analytic relations, insights for designing a compressor-bleed pair are provided.