Asymmetric compressor air extraction method

Abstract

A method to mistune rotating stall aerodynamics by preventing the formation of coherent unsteady loads. Compressor air is extracted in an asymmetric circumferential pattern. The asymmetric bleed pattern disrupts the rotating stall cell rotational pattern, preventing the formation of a coherent aerodynamic excitation.

Description

BACKGROUND OF THE INVENTION[0001]Power generation industrial axial flow gas turbines are designed to optimally operate at a fixed rotational speed and output. In addition, traditional axial flow industrial gas turbine compressors have limited variable stage geometry and air extractions. These three factors, fixed speed operation, limited variable stage geometry and limited extractions lead to significant off-design aerodynamic conditions during start-up and shutdown operations. Rotating stall occurs in axial flow compressors during these off-design operations.[0002]Rotating stall manifests itself as local stall cells that rotate at about half the wheel speed. These cells provide coherent unsteady aerodynamic loads on both the rotor and stator blades. As the rotor changes speed, the stall cell count changes thereby setting up different nodal diameters. The vibratory response on the rotor and stator blades from the rotating stall aerodynamic loads may lead to increased sensitivity of ...

AI Technical Summary

Benefits of technology

"The invention improves the durability of compressor blades by reducing the coherent aerodynamic forces created by rotating stall. This is achieved by mistuning the rotating stall aerodynamics to prevent the formation of coherent unsteady loads. The invention can be implemented by controlling air flow in a compressor by extracting flow at a series of asymmetric positions or by actuating extraction of compressor air to act against flow disturbances."

Problems solved by technology

In addition, traditional axial flow industrial gas turbine compressors have limited variable stage geometry and air extractions.

These three factors, fixed speed operation, limited variable stage geometry and limited extractions lead to significant off-design aerodynamic conditions during start-up and shutdown operations.

Rotating stall occurs in axial flow compressors during these off-design operations.

The vibratory response on the rotor and stator blades from the rotating stall aerodynamic loads may lead to increased sensitivity of normal blade damage and premature failures.

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