Fuel Split Control for Gas Turbine Flame Stability
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Solution Overview
Problem
Gas turbine engines experience flame failure during rapid load reductions due to pilot fuel flow becoming too lean, as existing methods rely on temperature measurements that lag in determining fuel split changes.
Innovation Solution
A method to control fuel split by monitoring the rate of change in fuel demand, adding additional pilot fuel during rapid load reductions to prevent flame failure, and adjusting this additional pilot fuel flow based on the rate of change, ensuring the pilot fuel flow remains sufficient for stability without exceeding emissions thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If pilot fuel flow is reduced during load reduction to optimize emissions, then emissions are minimized, but flame stability deteriorates causing flame failure
Solution Approach 1:
The control system performs preliminary action by detecting the rate of change in fuel demand before the actual load reduction completes. When a rapid decrease in fuel demand is detected, the system proactively increases the pilot fuel flow split above what would normally be required, preventing flame failure before it can occur. This anticipatory adjustment resolves the contradiction by maintaining flame stability while still allowing emissions to be optimized once the load reduction stabilizes.
2Measurement precision
If temperature measurements are used to determine fuel split changes, then control accuracy is maintained, but response time increases causing flame failure during rapid load changes
Solution Approach 1:
The system applies preliminary action by using the rate of change of fuel demand as an early indicator of upcoming load changes. This allows the control system to anticipate required fuel split adjustments before temperature measurements would indicate the need for change. By acting on the rate of change signal first, the system overcomes the time lag inherent in temperature-based control while maintaining accuracy through subsequent temperature feedback.
Solution Approach 2:
The control system employs feedback by continuously monitoring both the rate of change in fuel demand and the actual temperature measurements. The feedback loop compares the anticipated fuel split needs (based on rate of change) with actual temperature conditions, allowing the system to adjust the pilot fuel flow dynamically. This dual-feedback approach maintains measurement precision while reducing response time delays.
3Reliability
If additional pilot fuel is added during rapid load reduction to prevent flame failure, then flame stability is maintained, but emissions increase
Solution Approach 1:
The system applies dynamics by making the pilot fuel flow split adjustable and time-dependent rather than fixed. During rapid load reductions, the pilot fuel split dynamically increases to maintain flame stability. Once the load reduction stabilizes and the rate of change decreases, the pilot fuel split dynamically adjusts back to its optimized level for minimal emissions. This dynamic adjustment resolves the contradiction by allowing temporary emissions increase only when absolutely necessary for flame stability.
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
This approach prevents flame failure during rapid load changes by ensuring adequate pilot fuel is introduced early, maintaining flame stability while minimizing emissions by optimizing pilot fuel flow.
Implementation Method 1
Fuel is injected into the combustor where it is mixed with the compressed air from the compressor and burnt
Implementation Method 2
Fuel is injected into the combustor where it is mixed with the compressed air from the compressor and burnt
Data Source
AI summary
A method of controlling a fuel split of a pilot fuel flow and a main fuel flow in a gas turbine combustor during a load reduction is provided. The rate of change of fuel flow demand is monitored and an additional pilot fuel flow is added. The amount of additional pilot fuel flow depends on the rate of the change in fuel flow demand.