Variable Stator Vane Rigging for Gas Turbine Calibration
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Solution Overview
Problem
Existing variable stator vane systems in gas turbine engines face challenges in accurately calibrating and adjusting the angle of incidence, leading to aerodynamic inefficiencies and flow separation at low operational speeds and pressures, due to insufficient precision in previous calibration methods and potential drift from original settings caused by component wear.
Innovation Solution
A method involving a unison ring with radially offset rigging holes, aligned with corresponding holes in the casing, allows for precise adjustment of the angle of incidence by inserting a pin through aligned holes, enabling accurate calibration and adjustment of the variable stator vanes, and the use of a drive bar to connect the unison ring to an actuator for circumferential movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If variable stator vanes are used to maintain aerodynamic stability at low speeds, then compressor stability is improved, but manufacturing precision and calibration accuracy become critical challenges
Solution Approach 1:
A rigging pin is introduced as an intermediary component to precisely align and fix the circumferential position of the unison ring relative to the casing. The pin passes through aligned rigging holes in both components, serving as a mechanical mediator that ensures accurate calibration of the variable stator vanes' angle of incidence, thereby resolving the calibration accuracy challenge while maintaining compressor stability
Solution Approach 2:
The unison ring and casing are designed with self-aligning rigging holes that guide the rigging pin into precise circumferential alignment. This self-service mechanism allows the components to automatically achieve accurate positioning through their geometric features, reducing dependence on external calibration equipment and improving manufacturing precision
2Manufacturing precision
If the unison ring is rigidly fixed to prevent position drift, then calibration accuracy is improved, but adjustability for maintenance and wear compensation is lost
Solution Approach 1:
The system transitions from a static rigid connection to a dynamic adjustable connection. The rigging pin can be inserted to fix the unison ring position for accurate calibration, and later removed to allow repositioning and adjustment. This dynamic approach enables the system to switch between fixed (for accuracy) and adjustable (for maintenance) states, resolving the contradiction between calibration accuracy and adaptability
3Adaptability or versatility
If multiple rigging holes are provided for adjustment options, then adaptability is improved, but device complexity increases
Solution Approach 1:
The adjustment mechanism is segmented into discrete circumferential positions represented by multiple rigging holes. Instead of providing continuous adjustment capability, the system divides the adjustment range into specific discrete positions, reducing complexity while maintaining sufficient adaptability for calibration and wear compensation
Data Source
AI summary
A variable vane mechanism for adjusting the angle of stator vanes in a gas turbine engine is provided. The mechanism includes a circumferentially extending unison ring that is driven circumferentially around a casing by an actuator. The unison ring is connected to the stator vanes via levers such that the angle of the vanes changes with circumferential movement of the unison ring. The unison ring and the casing are each provided with at least one rigging hole in order to set the initial angle of the vanes. At least one of the unison ring and the casing are each provided with at least two rigging holes, so that the initial angle of the vanes can be adjusted by selecting different combinations of rigging holes. This may allow accumulations in tolerances to be compensated for and/or may allow the engine to be tested at different initial vane angles.