Fluid heating system with combustion trim learning
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Solution Overview
Problem
Current combustion control methods for boilers and furnaces do not account for various factors such as venting draft, fuel quality, and modulation percentage/firing rate, leading to sub-optimal combustion and failure to correct control based on these factors, especially when sensors like O2 sensors fail.
Innovation Solution
Implementing learned feedback control loops that adapt combustion control using multiple feedback loops to account for various operating conditions and factors, including air-fuel ratio, NOx concentration, and flame characteristics, with a controller system that includes sensors and an electronic processor to continuously adjust and correct combustion even when sensors fail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If continuous combustion control is implemented, then combustion can be regulated at all operating conditions, but sub-optimal combustion occurs at specific modulation percentages because the control fails to account for factors like venting draft and venting restriction
Solution Approach 1:
The control system is segmented into multiple independent feedback loops, each addressing specific combustion parameters (O2 concentration, NOx concentration, CO concentration, combustion oscillation, flame characteristics, burner temperature). This segmentation allows each loop to independently optimize its parameter without interfering with others, resolving the contradiction by enabling both continuous regulation and parameter-specific optimization at all modulation percentages
Solution Approach 2:
Multiple feedback loops continuously monitor and adjust combustion parameters based on real-time sensor data. The O2 feedback loop maintains proper air-fuel ratio, the NOx feedback loop controls emissions, and the CO feedback loop ensures complete combustion. This comprehensive feedback mechanism enables the system to adapt to changing conditions while maintaining optimal combustion at all operating points, including specific modulation percentages that were previously problematic
2Measurement precision
If O2 sensors are used for feedback control, then air-fuel ratio can be controlled, but the sensors have finite life and are prone to faults and failures
Solution Approach 1:
The system implements redundant sensing and multiple feedback loops that can compensate for sensor failures. By establishing multiple independent control pathways (NOx loop, CO loop, combustion oscillation loop) before any single sensor fails, the system cushions against the potential failure of O2 sensors. This ensures continuous optimal combustion control even when O2 sensors are no longer functional
Solution Approach 2:
The control system can switch between different measurement parameters and control strategies based on sensor availability. If O2 sensors fail, the system can rely on alternative parameters such as NOx concentration, CO concentration, combustion oscillation characteristics, or flame analysis to maintain proper air-fuel ratio control. This parameter flexibility maintains measurement precision and control reliability regardless of sensor status
3Adaptability or versatility
If multiple feedback loops are implemented to control various combustion parameters, then combustion can be optimized under different operating conditions, but the system complexity increases
Solution Approach 1:
The controller is designed as a universal platform that handles multiple feedback loops and control functions through standardized processing architecture. The same controller hardware and software framework manage O2 control, NOx control, CO control, combustion oscillation suppression, and flame monitoring, eliminating the need for separate dedicated controllers for each function. This multi-functionality reduces overall system complexity while maintaining high adaptability
Solution Approach 2:
Multiple feedback control functions are merged into a single integrated controller that processes signals from various sensors (O2, NOx, CO, flame sensors) and coordinates control actions across all combustion parameters simultaneously. This consolidation reduces the number of separate control devices, simplifies system architecture, and enables the controller to manage the complexity of multiple feedback loops through unified processing logic
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures optimal and efficient combustion control by adapting to changing conditions and maintaining proper control even when sensors like O2 sensors are no longer functional, ensuring continued system performance and efficiency.
Implementation Method 1
a first feedback control loop that uses an O2 sensor to maintain a proper air-fuel ratio
Implementation Method 2
a second feedback control loop that maintains a NOx concentration below a threshold level
Implementation Method 3
a third feedback control loop that maintains a CO concentration below a threshold level
Implementation Method 4
a flame rectification/flame signal
Implementation Method 5
a flame flicker/flame signal frequency
Implementation Method 6
combustion of a combination boiler
Data Source
AI summary
A fluid heating system including a burner unit is operated based on feedback control loops. The fluid heating system comprises a burner unit configured to heat a fluid, a sensor configured to sense a characteristic of the appliance, and a controller coupled to the burner unit and the sensor. The controller includes an electronic processor and a memory. The controller is configured to receive a first signal corresponding to the characteristic from the sensor, determine, based on the first signal, a first feedback loop control, control combustion of the burner unit based on the first feedback loop control, determine, based on the first feedback loop control, a second feedback loop control, and control combustion of the burner unit based on the second feedback loop control.