Aircraft Cabin Resonance Reduction via VIGV Offset Control
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Solution Overview
Problem
Current methods for reducing engine-induced aircraft cabin resonance in multi-engine aircraft, such as synchronizing engine speeds and precision balancing, often result in stability issues or are time-consuming and costly, particularly when dealing with multi-spool engines like turbofan gas turbines where high-pressure spool speeds remain non-synchronized.
Innovation Solution
An open-loop control system that senses the core engine speeds of multiple turbofan gas turbine engines, determines the speed difference, and adjusts the Variable Inlet Guide Vanes (VIGVs) to synchronize the core engine speeds by applying a VIGV offset value, effectively setting one engine as a 'master' and the other as a 'slave' to reduce resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed-loop control of N2 speed is used to synchronize both spools in multi-spool engines, then core engine speed synchronization is improved, but system stability deteriorates due to stability issues
Solution Approach 1:
The patent implements feedback control by sensing actual core engine speeds from both engines, comparing them to determine speed differences, and using this feedback to adjust the slave engine's VIGV position accordingly. This closed-loop feedback mechanism enables precise N2 synchronization while maintaining stability through proper feedback control design.
Solution Approach 2:
The patent changes the control parameter from direct N2 speed control to VIGV position control. By adjusting the VIGV offset value based on sensed N2 speed differences, the system indirectly controls core engine speed while avoiding the stability issues associated with direct closed-loop N2 control. This parameter transformation resolves the contradiction between synchronization precision and system stability.
2Object-affected harmful factors
If precision balancing of engines is performed prior to installation, then engine-induced resonance is reduced, but manufacturing time and cost increase
Solution Approach 1:
The patent performs preliminary speed synchronization of core engines using VIGV offset adjustment before the engines are installed in the aircraft. This preliminary action reduces resonance issues upfront, avoiding the need for time-consuming precision balancing operations after installation. The system achieves resonance reduction through operational adjustment rather than manufacturing-phase precision work.
Solution Approach 2:
The patent replaces mechanical precision balancing operations with an electronic control system that adjusts VIGV positions. Instead of physically balancing engine components through machining and assembly operations, the system uses electronic sensing and control to synchronize engine speeds, dramatically reducing the time and cost required while achieving the same resonance reduction effect.
3Ease of operation
If only fan spool (N1) speeds are synchronized in multi-spool engines, then ease of operation is improved, but noise and vibration from non-synchronized high pressure spools (N2) persist
Solution Approach 1:
The patent extends the synchronization function to cover both N1 and N2 spools using a universal control approach. The same control system that synchronizes fan spool speeds also synchronizes core engine speeds by adjusting VIGV positions. This multi-functional control system eliminates noise and vibration from both spool types while maintaining ease of operation through automated control.
Solution Approach 2:
The patent introduces the VIGV offset value as an intermediary control element to synchronize N2 speeds. Rather than directly controlling high-pressure spool speeds, the system uses VIGV position adjustment as an intermediary mechanism to indirectly control and synchronize core engine speeds. This intermediary approach maintains ease of operation while effectively eliminating noise and vibration.
Data Source
AI summary
A system and method of reducing engine induced aircraft cabin resonance includes sensing the core engine speed of a first turbofan gas turbine engine, and sensing the core engine speed of a second turbofan gas turbine engine. In a control system, the core engine speed of the first turbofan gas turbine engine and the core engine speed of the second turbofan gas turbine engine are processed to determine a core engine speed difference between the first and second turbofan gas turbine engines. The core engine speed difference is 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.