Thermal Flow Sensor Gas Combustion Parameter Determination
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Solution Overview
Problem
Existing methods for determining combustion parameters of gas mixtures, such as natural gases, are either complex and expensive or prone to inaccuracies, as they often require direct burning of the gas or sophisticated equipment for measurement.
Innovation Solution
A method utilizing a thermal flow sensor to measure oscillations in a gas flow through a variable volume chamber, allowing for the calculation of volumetric flow rate and subsequently determining combustion parameters like calorific value and Wobbe index without the need for direct gas burning or complex equipment, by measuring heat transfer and heat capacity parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gas chromatography is used to determine combustion parameters, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical measurement systems (gas chromatography) with a thermal flow sensor-based system. The thermal flow sensor measures mass flow rate, and combined with volumetric flow rate measurement, combustion parameters are calculated through mathematical relationships rather than direct chemical analysis, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces thermal flow sensor measurements as an intermediary method. Instead of directly analyzing gas composition through chromatography, the system uses thermal flow characteristics (mass flow rate) combined with volumetric flow rate to derive combustion parameters, simplifying the measurement pathway.
2Measurement precision
If direct burning or calorimetric analysis is used to measure combustion parameters, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent replaces direct burning and calorimetric analysis with a non-combustion-based thermal flow measurement system. By measuring mass flow rate through thermal flow sensor characteristics and combining it with volumetric flow rate, the system calculates combustion parameters without requiring actual gas combustion, thereby improving ease of operation while maintaining precision.
3Measurement precision
If thermal flow sensor with pressure difference measurement is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential measurement function from complex pressure difference measurement systems. By utilizing the thermal flow sensor's inherent ability to measure mass flow rate through its thermal characteristics, the system eliminates the need for separate pressure difference measurement across flow restrictors, reducing device complexity while maintaining measurement precision.
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 provides a simple, cost-effective, and accurate method for determining combustion parameters, suitable for retrofitting existing volumetric gas sensors, and can be used in conjunction with any bellows-type gas counter, offering precise predictions of combustion behavior.
Implementation Method 1
detecting an oscillation signal by a thermal flow sensor, the oscillation signal being indicative of the oscillations of the gas flow
Implementation Method 2
gas being alternatingly admitted into the chamber and being subsequently again expelled from the chamber, the alternate admission and expulsion causing oscillations of the gas flow
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
In a method for determining a combustion parameter (Hρ0) of a gas in a gas flow, a flow velocity or volumetric flow rate (dV/dt) of the gas in the gas flow is determined. In addition, a thermal flow sensor is exposed to the gas flow. A heat transfer parameter (λ0) and a heat capacity parameter (cp0ρ0) of the gas are calculated from an output of the thermal flow sensor and from the flow velocity or volumetric flow rate. The combustion parameter of the gas is then calculated from the heat transfer parameter and the heat capacity parameter.