APU Fuel Flow Control During Starting
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Solution Overview
Problem
Existing methods for controlling fuel flow in gas turbine engines during starting, such as auxiliary power units, often result in fuel flow discontinuities and instability due to predetermined and static look-up tables, leading to issues like combustor instability and failure to reach full speed.
Innovation Solution
A method that monitors the acceleration of the gas turbine engine and calculates a fuel flow rate based on actual acceleration, using a dynamic NDOT look-up table to adjust fuel flow rates, ensuring coordinated engine speed and fuel delivery for sustained combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If predetermined static look-up tables are used for fuel flow control, then the control system is simple, but fuel flow discontinuities and combustor instability occur
Solution Approach 1:
The patent applies dynamics by transitioning from static predetermined look-up tables to dynamic real-time acceleration monitoring. The system continuously measures actual acceleration and adjusts fuel flow rates dynamically based on current engine state, ensuring coordinated fuel delivery with engine speed changes during starting.
Solution Approach 2:
The patent implements feedback by monitoring actual engine acceleration in real-time and using this information to adjust fuel flow rates. The controller continuously compares actual acceleration with expected acceleration and modifies fuel delivery accordingly, creating a closed-loop control system that prevents fuel flow discontinuities.
2Reliability
If acceleration monitoring and dynamic fuel flow adjustment are implemented, then fuel flow stability improves, but control system complexity increases
Solution Approach 1:
The system applies self-service by using the engine's own acceleration characteristics to determine fuel flow requirements. The controller monitors acceleration that naturally occurs during starting and uses this self-generated information to adjust fuel delivery, eliminating the need for complex external control mechanisms.
Solution Approach 2:
The patent changes the control parameter from static predetermined values to dynamic real-time acceleration measurements. By using actual acceleration as the controlling parameter, the system adapts fuel flow rates to match the actual engine state, improving combustor stability while keeping the control logic relatively simple.
Data Source
AI summary
A method for controlling fuel flow to a gas turbine engine during starting includes monitoring acceleration of the gas turbine engine to determine actual acceleration value, and calculating a fuel flow rate for a setpoint acceleration using the actual acceleration value as a factor. The method further includes commanding the calculated fuel flow for the setpoint acceleration to the gas turbine engine.