Aircraft Engine Start Fuel Control With Flow Reduction Limiting
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Solution Overview
Problem
Existing methods for controlling fuel flow to aircraft engines during start are inadequate in preventing engine flameout due to rapid reductions in fuel flow, which can lead to unstable combustion and reduced engine performance.
Innovation Solution
A system and method that includes an engine controller to modulate fuel flow using a limiting factor, applying a closed loop fuel schedule to prevent excessive reductions in fuel flow, thereby maintaining stable combustion during engine start.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fuel flow is reduced following light-off, then combustion stability is improved, but engine flameout occurs due to excessive fuel reduction
Solution Approach 1:
The system uses a closed-loop control mechanism where the engine controller continuously monitors engine parameters and adjusts fuel flow commands in real-time. Following light-off, the controller reduces fuel flow to improve combustion stability but applies a limiting factor that prevents excessive reduction, thereby avoiding flameout while maintaining stable combustion.
Solution Approach 2:
The system dynamically changes the fuel flow rate parameter following light-off by applying a limiting factor. This parameter modification allows the fuel flow to be reduced from high levels to stable operating levels while preventing it from dropping below the minimum required to sustain combustion, thus resolving the contradiction between stability improvement and flameout prevention.
2Stability of the object's composition
If closed loop fuel control is applied, then fuel flow stability is improved, but system complexity increases
Solution Approach 1:
The patent implements a closed-loop fuel control system where the engine controller receives feedback from engine sensors and automatically adjusts fuel flow commands. This feedback mechanism improves fuel flow stability during start sequences while the automation of the control process minimizes the operational complexity burden on the operator.
Solution Approach 2:
The engine controller autonomously manages fuel flow adjustments during start sequences without requiring manual intervention. The system self-regulates by comparing actual engine parameters against target values and automatically applying the limiting factor to fuel flow commands, thereby improving stability while keeping the user interface simple.
Data Source
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AI summary
A method and system for controlling fuel flow to an aircraft engine during start are provided. Following light-off, an actual value of at least one engine operating parameter is obtained (404). Based on a difference between the actual value and a target value (406), a first command is generated (408) to cause fuel flow to be provided to the engine's combustor according to a computed fuel flow rate defined by a fuel schedule of the engine. When the computed fuel flow rate is within a fuel flow rate limit (410), the first command is output (420). Otherwise, a limiting factor (412) is applied to the computed fuel flow rate to limit a reduction in fuel flow to the combustor and a limited fuel flow rate is obtained (414), and a second command (416) is output to cause fuel flow to be provided to the combustor according to the limited fuel flow rate.