Method for driving a valve for regulating the flow rate of fuel gas towards a burner, in particular for condensation boilers having high power modulation
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Solution Overview
Problem
Conventional modulating valves in condensation boilers face limitations in achieving a wide range of power modulation, particularly in delivering controlled minimum gas flow rates, which is insufficient for high power modulation and adapting to different types of gases, due to the limitations of Venturi mixers and electronic control systems.
Innovation Solution
A method for driving a modulating valve that uses a PWM current signal with a specific frequency and duty cycle to modulate the gas flow rate, allowing for controlled delivery of gas flow rates below the conventional minimum, thereby extending the range of modulation by intermittently delivering gas and ensuring stable combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional modulating valve with continuous current control is used, then the valve structure is simple and control is straightforward, but the range of gas flow rate modulation is limited and cannot achieve high power modulation ratios
Solution Approach 1:
The patent applies periodic pulse-width modulation (PWM) signals to control the modulating valve. Instead of using continuous current control, the system uses periodic square-wave signals with varying duty cycles to drive the valve actuator. This periodic action enables the valve to achieve a wider range of gas flow rate modulation (up to 1:15 or higher) while maintaining a relatively simple valve structure and control system.
2Adaptability or versatility
If the minimum gas flow rate is reduced to extend modulation range, then high power modulation is achieved, but combustion stability becomes difficult to maintain
Solution Approach 1:
The PWM control system maintains combustion stability at low gas flow rates by using periodic pulsing action. The duty cycle is adjusted to deliver gas in controlled pulses rather than continuous flow, ensuring that the minimum gas flow rate remains sufficient for stable combustion while still achieving high power modulation ratios. The periodic nature of the control signal helps maintain flame stability even when the average gas flow rate is very low.
Solution Approach 2:
The system incorporates feedback from flame detection sensors to monitor combustion stability. When the gas flow rate is reduced to extend the modulation range, the feedback mechanism detects changes in flame characteristics and adjusts the PWM duty cycle accordingly to maintain stable combustion. This closed-loop control ensures that combustion stability is preserved across the entire modulation range.
3Measurement precision
If electronic control with sensor feedback is implemented, then closed-loop combustion control is achieved, but the cost of sensor devices and control electronics increases
Solution Approach 1:
The patent implements closed-loop combustion control using flame detection sensors that provide feedback to the control system. The sensors detect combustion quality parameters such as flame presence, intensity, and stability, and this information is fed back to adjust the PWM control signals to the modulating valve. This feedback mechanism enables precise combustion control while maintaining cost-effectiveness by using straightforward sensor and control electronics architecture.
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 method enables a wider range of modulation in minimum gas flow rates, improving the ability to adapt to different gases and ensuring efficient and stable combustion, while maintaining cost-effectiveness by not requiring substantial modifications to the valve or control hardware.
Implementation Method 1
the operating means is directly associated with the closure member (1b) so as to move it in a controlled manner in relation to the valve seat (1a)... an electrical actuator, and more specifically of an electromagnetic actuator
Implementation Method 2
A method for driving a modulating valve that uses a PWM current signal with a specific frequency and duty cycle to modulate the gas flow rate
Data Source
AI summary
A method for modulating a valve regulating the flow rate of gas towards a burner is presented. The valve with the associated closure member configured to operate with a predetermined characteristic curve, the flow rate delivered being proportionally related to the strength of a first current signal sent to the modulator such that the flow rate can be modulated, using the proportionality, within a range of modulation between a maximum flow rate and a minimum flow rate. To deliver controlled gas flow rates that are below the minimum flow rate, the modulator is driven with a second PWM voltage signal capable of generating a particular second PWM current signal, to move the closure member of the valve according to the second signal. First and second time intervals correspond to successive durations of high signal and low signal, respectively, the sum being equal to a period of the second signal.