Gas Turbine Combustion Instability Control via Frequency Detuning
Solution Overview
Problem
Gas turbines experience unwanted vibrations in hot gas path components due to in-phase, coherent combustion tones, which existing methods manage by limiting combustor operating range, leading to inefficiencies and potential wear.
Innovation Solution
A system and method that detects combustion instability frequency, coherence, phase, and amplitude, and adjusts parameters such as fuel flow and temperature to reduce vibrations, decoupling combustion dynamics and coherence, thereby reducing vibratory responses in downstream components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If combustor tuning is used to limit the amplitude of combustion dynamics in a particular frequency band, then unwanted vibrations in downstream components are reduced, but the operating range of the combustor is unnecessarily limited
Solution Approach 1:
The system dynamically adjusts combustor operating parameters (such as fuel flow rate, air flow rate, or equivalence ratio) to shift the combustion instability frequency away from the natural frequency of downstream components. This frequency detuning approach reduces coherent vibrations without requiring restrictive combustor tuning that would limit the operating range, thereby resolving the contradiction between vibration reduction and operational flexibility
Solution Approach 2:
The system implements active feedback control by continuously monitoring combustion dynamics characteristics (frequency, coherence, amplitude) and adjusting combustor parameters in real-time to maintain frequency separation from downstream component natural frequencies. This dynamic adaptation allows the combustor to operate across a wide range of conditions while actively preventing harmful vibrations, thus preserving operating range while reducing unwanted vibrations
2Object-affected harmful factors
If the frequency of combustion dynamics in one or more combustors is driven away from that of other combustors, then coherence and modal coupling are reduced, but additional control complexity is introduced
Solution Approach 1:
The system modifies combustor operating parameters (fuel flow, air flow, or equivalence ratio) to actively control and separate the combustion instability frequencies of different combustors. By dynamically adjusting these parameters, the system reduces coherence and modal coupling between combustors, preventing harmful coherent vibrations while managing control complexity through parameter-based control strategies
Data Source
AI summary
A system for operating a gas turbine includes a controller configured to execute logic stored in a memory that causes the controller to determine two or more of a frequency, a coherence, a phase, and an amplitude, of a combustion instability; to compare two of more of the frequency, the coherence, the phase, and the amplitude of the combustion instability to a respective predetermined limit; and to adjust at least one parameter of the gas turbine if two or more of the frequency, the coherence, the phase, and the amplitude of the combustion instability are actionable relative to their respective predetermined limits. A related method of operating the gas turbine is also disclosed.