Gas Turbine Combustion Hum Stability Control
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Solution Overview
Problem
Gas turbines experience combustion oscillations, or 'combustor hum,' which lead to mechanical and thermal stress, potentially causing damage and requiring reduced power output to avoid, due to the difficulty in maintaining a safe distance from self-excited combustion oscillation limits that shift with environmental changes.
Innovation Solution
A method to analyze the tendency of a combustion chamber to hum by detecting thermoacoustic and oscillation variables, determining resonance amplitudes, calculating a stability parameter, and using threshold values to quantify the hum tendency, allowing for timely intervention to prevent excessive vibrations and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the gas turbine is operated at high turbine inlet temperature to achieve high thermal efficiency, then the thermal efficiency is improved, but the combustion chamber tends to hum and combustion oscillations occur
Solution Approach 1:
The system performs preliminary detection of thermoacoustic variables and calculates stability parameters before combustion oscillations fully develop. By identifying early signs of hum tendency through spectrum analysis and resonance amplitude ratios, the control system can take preventive action to adjust operating parameters, thereby maintaining high thermal efficiency while preventing combustion chamber instability.
Solution Approach 2:
The system continuously monitors thermoacoustic variables, calculates stability parameters in real-time, and feeds this information back to the control system. This feedback mechanism enables dynamic adjustment of turbine inlet temperature and fuel supply to maintain stable combustion operation at high thermal efficiency, preventing the development of combustion oscillations.
2Reliability
If the gas turbine output power is reduced with high load gradient to relieve combustion oscillations, then the combustion chamber stability is improved, but the gas turbine productivity is reduced
Solution Approach 1:
The system detects early signs of combustion oscillation development through stability parameter analysis before the oscillations reach damaging levels. By taking preliminary control actions at this early stage, the system can maintain gas turbine output power while preventing full-scale combustion oscillations, thereby avoiding the need for drastic load reduction.
Solution Approach 2:
The real-time feedback of stability parameters enables continuous monitoring of combustion chamber conditions. The control system uses this feedback to make gradual, controlled adjustments to fuel supply and air flow that maintain combustion stability while preserving gas turbine productivity, avoiding the need for high load gradient reductions.
3Reliability
If the gas turbine is operated at a sufficient distance from the limit of self-excited combustion oscillations to prevent hum, then the combustion chamber stability is improved, but the upper power range of the gas turbine must be excluded
Solution Approach 1:
The system dynamically adjusts the safe operating distance from the combustion oscillation limit based on real-time detection of environmental conditions and combustion chamber state. By adapting the stability margin dynamically rather than maintaining a fixed conservative distance, the system can operate in the upper power range while still preventing combustion oscillations under varying environmental conditions.
Solution Approach 2:
The system changes operating parameters such as turbine inlet temperature, fuel supply rate, and air flow based on detected stability parameters and environmental conditions. This enables the gas turbine to operate closer to the combustion oscillation limit in favorable conditions (expanding usable power range) while maintaining adequate safety margins when environmental conditions favor oscillation development.
4Adaptability or versatility
If the limit of self-excited combustion oscillations shifts due to changing environmental conditions, then the adaptability to environmental changes is improved, but the safe operating range must be reduced to account for the most unfavorable conditions
Solution Approach 1:
The system continuously monitors environmental conditions and adjusts operating parameters accordingly. When environmental conditions change and shift the combustion oscillation limit, the system modifies turbine inlet temperature, fuel supply, and air flow parameters to maintain stable operation. This enables the gas turbine to adapt to environmental changes while maintaining an expanded usable power range, rather than operating with a reduced margin to account for all possible unfavorable conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous operation of the gas turbine by reducing output power when approaching the hum limit, preventing damage and maintaining high power output while minimizing shutdowns, by using the stability parameter to control the gas turbine's operation and adjust parameters like compressor air mass flow and fuel temperature.
Implementation Method 1
detecting a thermoacoustic variable of the combustion chamber gas volume and/or an oscillation variable of the combustion chamber structure
Implementation Method 2
identifying a first resonance and a second resonance of the parameter using the spectrum; determining the amplitude value of the first resonance and the amplitude value of the second resonance
Implementation Method 3
Combustion oscillations can occur during the combustion of a combustion air/fuel mixture in a combustion chamber
Implementation Method 4
there are periodic correlated fluctuations in the combustion conversion and the static pressure in the combustion chamber, with the combustion oscillations being based on an interaction between the combustion air/fuel mixture flowing in the combustion chamber and the instantaneous combustion conversion in the flame
Data Source
Figure 1~2
Figure 3~4
AI summary
The method involves identifying resonances of a characteristic variable by a spectrum, and determining amplitude values of the resonances. A stability parameter (9) is calculated as a function of the values. A lower distance value and/or upper distance value, on which the stability parameter lies above a lower threshold value and/or below an upper threshold value, are determined. The threshold values are selected such that the parameter lies on one of the threshold values if a combustion chamber is operated in an operating state with a humming tendency higher than a permissible value. Independent claims are also included for the following: (1) a method for operating a gas turbine (2) a control device for controlling operation of a gas turbine.