VIGV Offset Control for Engine Cabin Resonance
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Solution Overview
Problem
Current methods for reducing engine-induced aircraft cabin resonance in multi-engine aircraft, such as synchronizing engine spools, often rely on closed-loop N2 control or precision engine balancing, which can be costly and time-consuming, and may exhibit stability issues.
Innovation Solution
An open-loop N2 synchronization control system that uses flight and engine condition sensors to determine a core engine speed difference sensitivity value and apply a variable inlet guide vane offset to synchronize the core engine speeds of turbofan gas turbine engines without relying on closed-loop control or precision balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop N2 control is used to synchronize core engine speeds, then engine speed synchronization is improved, but system stability deteriorates
Solution Approach 1:
The patent replaces the closed-loop control system with an open-loop system that uses pre-calculated sensitivity values and lookup tables. Instead of continuously sensing and adjusting N2 speed through feedback control, the system uses flight condition sensors and engine operating condition sensors to index into pre-computed tables that provide VIGV offset values, eliminating the stability issues inherent in closed-loop control while achieving the same synchronization effect.
Solution Approach 2:
The patent performs preliminary calculations of N2 speed sensitivity to VIGV position changes across the entire operating range before flight. These sensitivity values are stored in lookup tables indexed by flight conditions and engine parameters. During flight, the system simply retrieves pre-computed values rather than performing real-time iterative control calculations, eliminating stability concerns while maintaining precision.
2Object-affected harmful factors
If precision engine balancing is performed prior to installation, then engine-induced resonance is reduced, but time consumption and cost increase
Solution Approach 1:
The patent changes the approach from physical engine balancing (mechanical parameter adjustment) to operational parameter control. By controlling the VIGV position offset based on flight conditions and sensitivity values, the system achieves resonance reduction through operational adjustments rather than physical modifications to the engine, eliminating time-consuming precision balancing procedures.
Solution Approach 2:
The system uses onboard sensors and pre-computed sensitivity data to automatically adjust VIGV positions for resonance reduction during flight operations. This self-adjusting capability eliminates the need for external precision balancing services, reducing both time and cost while achieving the same harmful factor reduction.
3Speed
If only N1 spool synchronization is implemented in multi-spool engines, then fan spool synchronization is achieved, but core spool (N2) desynchronization continues causing noise and vibration
Solution Approach 1:
The patent introduces the VIGV (variable inlet guide vane) as an intermediary control element to synchronize N2 speeds. By adjusting the VIGV position offset based on pre-computed sensitivity values and measured speed differences, the system indirectly controls core spool speed without requiring direct N2 sensing or complex control mechanisms, achieving both N1 and N2 synchronization simultaneously.
Data Source
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AI summary
A system method of reducing engine induced aircraft cabin resonance in an aircraft includes sensing a parameter representative of current aircraft flight conditions, and sensing a parameter representative of current engine operating conditions of at least one of a first turbofan gas turbine engines or a second turbofan gas turbine engine. In a control system, the parameter representative of current aircraft flight conditions and the parameter representative of current engine operating conditions are processed to supply a variable inlet guide vane (VIGV) offset value. The VIGV offset value is applied to a VIGV reference command associated with one of the first or second turbofan gas turbine engine, to thereby cause the VIGVs of one of the first or second turbofan gas turbine engine to move to a more closed position.