Gas Burner Modulation Range Extension via Combustion Quality Feedback
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Solution Overview
Problem
Existing gas burner control methods are not accurate enough below 20% of maximum fan speed, as tolerances in the pneumatic controller's behavior and changes over time affect combustion quality, limiting the modulation range to 1:5, and calibration is unreliable outside a specific subrange near full-load operation.
Innovation Solution
The method uses a combustion quality sensor to detect tolerances and changes in the pneumatic controller's behavior, adjusting the gas throttle setting based on a pre-learned or adaptive compensation curve to maintain combustion quality across a broader modulation range, up to 1:8 or 1:10, by dividing the modulation range into subranges and monitoring combustion quality at intermediate fan speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the modulation range is extended below 20% fan speed, then the control range is improved, but the combustion quality deteriorates due to pneumatic controller tolerances
Solution Approach 1:
The system performs a preliminary calibration phase before normal operation to establish a compensation curve that accounts for pneumatic controller tolerances. During this calibration phase, the system measures actual combustion quality at various fan speeds and creates a lookup table or compensation curve that will be used to adjust gas flow settings during normal operation, thereby pre-compensating for the tolerances that would otherwise degrade combustion quality at low fan speeds.
Solution Approach 2:
The system implements a feedback mechanism where a sensor continuously monitors combustion quality (such as flame ionization current) and feeds this information back to the control system. The control system compares the actual combustion quality against target values and automatically adjusts the gas flow rate through the mixing device to maintain optimal combustion, thereby compensating for pneumatic controller tolerances in real-time and maintaining reliable combustion quality across the extended modulation range.
2Adaptability or versatility
If calibration is performed outside the 50%-100% fan speed subrange, then the calibration applicability is improved, but the calibration reliability deteriorates
Solution Approach 1:
The system performs a preliminary calibration phase before normal operation to establish a compensation curve that accounts for pneumatic controller tolerances. During this calibration phase, the system measures actual combustion quality at various fan speeds and creates a lookup table or compensation curve that will be used to adjust gas flow settings during normal operation, thereby pre-compensating for the tolerances that would otherwise degrade combustion quality at low fan speeds.
Solution Approach 2:
The system transitions from a static calibration approach (fixed calibration points) to a dynamic calibration approach where the system adaptively determines calibration points based on actual system behavior. The control system can dynamically adjust fan speed settings during calibration and use interpolation between calibration points to maintain accuracy across the full modulation range, rather than relying on fixed calibration subranges.
3Device complexity
If the mixing ratio is kept constant over the modulation range, then the control simplicity is improved, but the combustion quality control deteriorates at low fan speeds
Solution Approach 1:
The system performs a preliminary calibration phase before normal operation to establish a compensation curve that accounts for pneumatic controller tolerances. During this calibration phase, the system measures actual combustion quality at various fan speeds and creates a lookup table or compensation curve that will be used to adjust gas flow settings during normal operation, thereby pre-compensating for the tolerances that would otherwise degrade combustion quality at low fan speeds.
Solution Approach 2:
The system dynamically changes the mixing ratio parameter based on fan speed. Instead of maintaining a constant mixing ratio, the control system adjusts the gas flow rate relative to air flow rate according to the operating point. At low fan speeds, the system applies compensation factors derived from calibration data to maintain optimal combustion, while at higher fan speeds the mixing ratio returns to standard values, thereby maintaining combustion quality across the full modulation range without requiring complex real-time calculations.
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
This approach allows for accurate and fast control of the gas burner across a broader modulation range, compensating for tolerances and behavioral changes in the pneumatic controller, ensuring reliable operation over the entire modulation range and extending the control range to 1:8 or 1:10.
Implementation Method 1
a flame ionization sensor (13)
Data Source
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AI summary
Method for operating a gas burner, wherein during burner-on phases a defined gas/air mixture having a defined mixing ratio of gas and air is provided to a burner chamber (11) of the gas burner for combusting the defined gas/air mixture within the burner chamber (11). Said defined gas/air mixture is provided by a mixing device (23) mixing an air flow provided by an air duct (15) with a gas flow provided by a gas duct (16). Said air flow flowing is provided by fan (14) in such a way that the fan speed of the fan (14) depends on a desired burner load of the gas burner, wherein the fan speed range of the fan (14) defines a modulation range of the gas burner. Said mixing ratio of gas and air of the gas/air mixture is controlled over the modulation range of the gas burner by a pneumatic controller (24) on basis of a pressure difference between the gas pressure of the gas flow in the gas pipe (16) and a reference pressure, wherein either the air pressure of the air flow in the air duct (15) or the ambient pressure is used as reference pressure, and wherein the pressure difference between the gas pressure and the reference pressure is determined and controlled pneumatically. During burner on phases the combustion quality is monitored on basis of a signal provided by a combustion quality sensor like a flame ionization sensor (13) or an exhaust gas sensor (26). The signal provided by the combustion quality sensor is used to detect tolerances of the pneumatic controller (24) and/or a potentially changing behaviour of the pneumatic controller (24) by checking if the combustion quality is inside or outside a defined combustion quality range; wherein when the combustion quality is inside the defined combustion quality range, the mixing ratio of gas and air of the gas/air mixture is kept constant; and wherein when the combustion quality is outside the defined combustion quality range, the mixing ratio of gas and air of the gas/air mixture is changed by adjusting a setting of a gas throttle (17) positioned within the gas duct (16). Influences of tolerances of the pneumatic controller (24) and/or of a potentially changing behaviour of the pneumatic controller (24) become compensated such that the modulation range can be extended to lower loads.