Complementary Filter for Water-Fuel Ratio Control
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Solution Overview
Problem
Existing engine control systems face challenges in accurately managing the water-fuel ratio to balance carbon emissions reduction and stable combustor flame, particularly in varying fuel flow rates and valve positions.
Innovation Solution
A controller system that uses a complementary filter to create a compensated signal by lagging an error signal, combining it with a high-frequency fuel valve signal, and determining a water flow request based on a desired water-fuel ratio, allowing for precise control of water supply to maintain optimal engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flowmeter is used to measure fuel flow rate, then measurement precision is improved, but response bandwidth is limited and cannot track rapid valve position changes
Solution Approach 1:
The patent introduces an intermediary computational model that acts as a bridge between the flowmeter and valve position sensor. This model combines the low-frequency accurate flowmeter signal with the high-frequency valve position signal through signal processing (combining measured flow rate with modeled flow rate based on valve position), effectively transferring the high response bandwidth of the valve sensor to the flow measurement without requiring a more expensive high-bandwidth flowmeter.
2Speed
If valve position signal is used directly for water-fuel ratio control, then response speed is improved, but measurement accuracy deteriorates due to not reflecting actual fuel flow
Solution Approach 1:
The patent implements a feedback mechanism where the actual measured flow rate from the flowmeter is continuously compared with the modeled flow rate based on valve position. The difference (error signal) is processed and used to adjust the water-fuel ratio control, ensuring that the control system responds quickly to valve movements while maintaining accuracy by continuously correcting based on actual flow measurements.
3Object-generated harmful factors
If water-fuel ratio control is tightened to reduce emissions, then environmental performance is improved, but risk of combustor flameout increases due to insufficient fuel
Solution Approach 1:
The patent uses feedback from the complementary filter that continuously monitors the discrepancy between commanded fuel flow (based on valve position) and actual fuel flow (measured by flowmeter). This feedback ensures that water injection is precisely matched to actual fuel delivery, allowing aggressive emissions control by preventing both over-injection (which would cause flameout) and under-injection (which would allow excess emissions).
Solution Approach 2:
The patent applies preliminary action by using the complementary filter to predict and compensate for flow measurement lags before they cause problems. The filter proactively adjusts the water-fuel ratio control signal based on the phase lead compensation, preventing potential flameout conditions before they occur while maintaining strict emissions control.
Data Source
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AI summary
Systems and methods for use with water-fuel supply to industrial engines are provided. A method for controlling water supplied to an engine (12) may include using both a desired water-fuel ratio, and a compensated fuel flow. This compensated fuel flow may be calculated by a controller-implemented complementary filter (19), which may include receiving, by the controller (18), a first signal (42) and a second signal (44). The complementary filter (19) may subtract the second signal (44) from the first signal (42) to create an error signal (58), lag the error signal (58) to create a lagged error signal (60), and add the lagged error signal (60) to the second signal (44) to create a compensated signal (62). The controller (18) may calculate a water flow request using a desired water-fuel ratio and the compensated signal (62).