Model-Based Fuel-Air Ratio Control for Gas Turbine Lean Blowout
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Solution Overview
Problem
Modern gas turbine engines face challenges in avoiding lean blowout, a condition where the fuel-air ratio in the combustor falls, causing the flame to be extinguished, which can lead to engine failure and reduced component lifetimes.
Innovation Solution
A model-based fuel-air ratio control system is implemented, which uses a predictive engine model to estimate the fuel-air ratio in real-time, comparing it to a predetermined limit to adjust fuel flow and prevent lean blowout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional indirect FAR management by limiting fuel-sensed combustor pressure ratio is used, then lean blowout is avoided, but manufacturing precision and real-time FAR control are compromised
Solution Approach 1:
The patent replaces indirect mechanical pressure ratio sensing with a model-based computational system that calculates FAR using thermodynamic equations and sensor data. This substitution enables direct FAR control while maintaining reliability, as the model provides precise real-time FAR estimation without relying on indirect pressure ratio limitations
Solution Approach 2:
The patent introduces a predictive engine model as an intermediary between raw sensor measurements and FAR control decisions. This model processes multiple sensor inputs (temperature, pressure, flow rates) through thermodynamic equations to generate accurate FAR estimates, enabling precise control while avoiding lean blowout conditions
2Manufacturing precision
If model-based predictive control is implemented for real-time FAR estimation, then FAR control precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal predictive engine model that serves multiple functions: estimating FAR, predicting combustor outlet temperature, and detecting off-design operating conditions. This multi-functionality reduces overall system complexity by consolidating control tasks into a single model framework rather than requiring separate systems for each function
Solution Approach 2:
The predictive engine model uses readily available sensor data from the engine's existing monitoring system to self-calculate FAR and control parameters. The model serves itself by processing its own input data through embedded thermodynamic equations, eliminating the need for additional dedicated sensors or complex external control systems
Data Source
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AI summary
A gas turbine engine comprises a compressor (30, 32) , a combustor (14), a turbine (34, 36), and an electronic engine control system (102). The compressor, combustor, and turbine are arranged in flow series. The electronic engine control system is configured to estimate combustor fuel-air ratio based on a realtime model-based estimate of combustor airflow, and commands engine actuators to correct for a difference between the estimated combustor fuel-air ratio and a limit fuel-air ratio selected to avoid lean blowout.