Heating Appliance Air-Fuel Ratio Verification via Flow Change
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling combustion in hydrogen-powered heating appliances are unreliable due to sensor drift and environmental factors, leading to potential flame flashback, decreased energy efficiency, and unburned fuel in the exhaust, without providing effective detection of sensor drift.
Innovation Solution
A method involving continuous measurement of combustion air and fuel gas flow rates to calculate a virtual combustion air ratio, using a control unit to adjust the gas valve and ensure a stable air-fuel mixture, with optional flame monitoring and sensor redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors or optical sensors are used to measure combustion parameters for control, then combustion control is possible, but sensor drift occurs leading to gradual change in combustion air ratio and critical conditions
Solution Approach 1:
The patent extracts the combustion air ratio determination from sensor-based measurement and replaces it with calculation based on fundamental flow measurements. The combustion air ratio lambda is calculated from the ratio of combustion air mass flow to fuel mass flow, eliminating dependence on drift-prone temperature or optical sensors while maintaining combustion control capability
Solution Approach 2:
The patent introduces mass flow measurements of combustion air and fuel as intermediary variables. Instead of directly measuring combustion parameters with drift-prone sensors, the system measures the mass flows of the individual components (air and fuel) and calculates the combustion air ratio from these measurements, providing a stable and reliable control basis
2Ease of operation
If combustion air ratio is controlled using sensor signals, then combustion regulation is achieved, but geometric tolerances and environmental effects cause shift in combustion air ratio
Solution Approach 1:
The patent implements feedback control by continuously measuring the actual combustion air ratio through mass flow measurements and comparing it with the target ratio. The control system adjusts the combustion air mass flow based on this feedback to maintain the desired combustion air ratio, compensating for geometric tolerances and environmental effects
Solution Approach 2:
The patent replaces mechanical/sensor-based combustion parameter measurement with a calculation-based approach using mass flow measurements. The combustion air ratio is determined through mathematical calculation from measured mass flows rather than through physical sensors subject to environmental influences
3Adaptability or versatility
If hydrogen is used as fuel with ionization current measurement, then combustion control is attempted, but measurement is unreliable
Solution Approach 1:
The patent extracts the combustion air ratio determination from ionization current measurement and replaces it with direct mass flow measurement and calculation. This eliminates the unreliable ionization current measurement method while maintaining hydrogen fuel compatibility through accurate mass flow-based control
Solution Approach 2:
The patent changes the measurement parameter from ionization current to mass flow. By measuring the mass flow of combustion air and fuel directly and calculating the combustion air ratio from these parameters, the system achieves reliable combustion control with hydrogen fuel without depending on ionization current measurement
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for operating a heating appliance (1) is proposed, comprising a conveying device (2) for conveying a combustion mixture of fuel gas and combustion air to a burner (3) and a gas valve (5) for controlling a flow rate of fuel gas, wherein the method comprises at least the following steps: a) detecting a volume flow rate V̇Air(t0) of combustion air (17) supplied to the burner (3) at a time t0 (18), b) opening or closing the gas valve (5), c) detecting the volume flow rate V̇Air(t) of combustion air at a time t (19) after opening or closing the gas valve (5) in step b), d) determining a ratio R(t) with - Rt=V˙AirtV˙Airt0 when the gas valve (5) was opened in step b) and with - Rt=V˙Airt0V˙Airt when the gas valve (5) was closed in step b). The procedure allows for checking/verifying a combustion air ratio assumed and set by the combustion control system.Optionally, the combustion air ratio can be adjusted. Furthermore, a heating unit (1), a control and regulating unit (7), and a computer program are proposed.