Heatable Sensor Combustion Air Flow Determination
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Solution Overview
Problem
Existing methods for determining the flow rate of combustion air in heaters are not robust, leading to potential shifts in the combustion air ratio, which can cause flashbacks or difficulties in ignition, especially in modulating heaters and hydrogen-powered devices, and often require additional sensors or complex calibration processes.
Innovation Solution
A method using at least two resistance values from an electrically heatable temperature sensor, subjected to different powers, to determine the flow rate of combustion air, allowing for robust regulation of the combustion air ratio without significant structural changes to the heater, and enabling verification of previously determined mass flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional temperature sensors are arranged in a measuring tube to determine mass flow, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The existing temperature sensor in the burner serves dual purposes: it detects flame temperature for combustion control and simultaneously determines combustion air mass flow through resistance measurements. This eliminates the need for separate flow measurement sensors, resolving the contradiction between improved measurement precision and reduced device complexity.
Solution Approach 2:
The temperature sensor is made multi-functional by utilizing its resistance characteristics to perform both temperature detection and flow rate determination. By measuring resistance at different power levels and applying thermal model calculations, the same sensor provides multiple measurement capabilities without adding hardware complexity.
2Measurement precision
If a glow plug is energized and adjusted to a nominal point to determine heat dissipation as a measure of combustion air mass flow, then measurement precision is improved, but the method cannot be applied to modulating heaters
Solution Approach 1:
The measurement method transitions from static calibration at a nominal point to dynamic measurements during actual operation. By continuously measuring resistance values at different power levels during heater operation, the system adapts to varying load conditions and can accurately determine mass flow in modulating heaters across their entire operating range, not just at a fixed nominal point.
Solution Approach 2:
The method utilizes changes in electrical resistance parameters of the temperature sensor under different power conditions to determine mass flow. By measuring resistance at multiple power levels and using thermal model calculations, the system captures dynamic operating conditions rather than relying on a single calibrated nominal point, enabling versatility across modulating operations.
3Measurement precision
If the temperature sensor is subjected to different power levels to record resistance values, then combustion air flow rate determination accuracy is improved, but energy consumption increases
Solution Approach 1:
The temperature sensor is subjected to different power levels in a periodic or sequential manner rather than continuously. Resistance measurements are taken at different power levels at specific measurement intervals, allowing accurate flow rate determination while minimizing additional energy consumption compared to continuous high-power operation. The system alternates between measurement phases and normal operation phases.
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 ensures reliable and safe operation of heaters by accurately determining the combustion air flow rate, preventing flashbacks and improving operational reliability, particularly in modulating and hydrogen-powered systems, without the need for additional sensors or complex calibration.
Implementation Method 1
at least two (electrical) resistance values of at least one temperature sensor are recorded, wherein the at least one temperature sensor is subjected to a different power when the at least two resistance values are recorded
Implementation Method 2
at least one electrically heatable temperature sensor arranged such that a temperature of a flame of the heater can be detected
Data Source
Figure 1
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Figure 4~5
AI summary
A method is proposed for determining the flow rate of combustion air in a heating appliance (1), wherein the heating appliance (1) comprises a burner (3) to which a mixture of fuel gas and combustion air is supplied via a mixture channel (11) by means of a conveying device (2), and at least one heatable temperature sensor (13) arranged such that the temperature of a flame of the heating appliance (1) can be detected. The method allows: - at least two resistance values (24, 25) of at least one temperature sensor (13) to be detected, wherein the at least one temperature sensor (13) is subjected to different power levels when detecting the at least two resistance values (24, 25), and - a flow rate of combustion air to be determined by evaluating the at least two resistance values (24, 25).Furthermore, a method for operating a heating device (1), a computer program, a heating device (1) and a use of two resistance values are specified.