Composite Fuel Flow Demand for Gas Turbine Transient Control
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Solution Overview
Problem
Current FADEC systems in gas turbine engines face challenges in accurately determining fuel flow demand during transient operations due to the difficulty in merging rate-based and non-rate based signals, leading to complex logic and inconsistent performance.
Innovation Solution
A system and method that integrates a control initiated fuel flow demand based on an operator command and a tracking error, combining these with a composite fuel flow demand to improve fuel flow control, reducing the complexity of logic and enhancing performance during transient operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the engine controller merges rate-based tracking error with non-rate based operator command using complex logic, then the fuel flow demand determination becomes more accurate, but the device complexity and memory requirements increase
Solution Approach 1:
The patent introduces an intermediary variable called 'composite fuel flow demand' that serves as a bridge between the rate-based tracking error signal and the non-rate based operator command. This composite signal combines both inputs through a unified transfer function, eliminating the need for complex merging logic while maintaining accuracy in fuel flow demand determination during transient operations.
2Reliability
If additional memory and computational resources are allocated to handle both rate-based and non-rate based signals, then the transient operation performance improves, but the device complexity increases
Solution Approach 1:
The patent transforms the control approach by changing the parameter representation from separate rate-based and non-rate based signals to a unified composite fuel flow demand parameter. This parameter transformation allows the system to maintain high transient operation reliability while reducing memory and computational requirements, as the unified parameter can be processed through a single transfer function without requiring multiple separate processing paths.
3Measurement precision
If the controller uses integrated logic to combine tracking error and operator command, then the error and bandwidth performance improves, but the logic becomes susceptible to forgetting history and becoming confused
Solution Approach 1:
The patent extracts the historical information requirement from the complex merging logic and embeds it directly into the composite fuel flow demand parameter definition. By defining the composite parameter to inherently contain the integrated history of both tracking error and operator command through the transfer function, the system maintains superior error and bandwidth performance while eliminating the susceptibility to losing historical context that plagues complex adaptive logic.
Data Source
AI summary
A computer-implemented method for controlling a fuel flow to a gas turbine engine of an aircraft includes determining a control initiated fuel flow demand that is based, at least in part, on an operator command. In addition, the method includes determining a first rate of change of fuel flow demand based, at least in part, on a tracking error of the gas turbine engine that indicates a difference between a desired rotational speed and an actual rotational speed. The method also includes integrating the first rate of change of fuel flow demand to determine a tracking error fuel flow demand. In addition, the method includes summing the control initiated fuel flow demand and tracking error fuel flow demand to determine a composite fuel flow demand. The method also includes controlling a fuel flow to the gas turbine engine based, at least in part, on the composite fuel flow demand.