Fuel Supply Device Calorific Value Control
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Solution Overview
Problem
Existing fuel supplying devices face challenges in maintaining the optimal mixing ratio of air and oxygen in a mixed gas based on the calorific value of the fuel gas, especially when there are changes in the composition of the fuel gas, leading to potential incomplete combustion.
Innovation Solution
A fuel supplying device equipped with a thermal mass flow rate sensor, calculation units, and flow rate adjusting devices that calculate and adjust the calorific flow rate of the fuel gas to match a control target value, and correct the air and oxygen flow rates based on the calculated ratio of the calorific value per unit volume, ensuring optimal mixing ratios regardless of fuel gas composition changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the air and oxygen supply rates are controlled based on the mass flow of fuel gas measured by a thermal mass flowmeter, then the fuel gas supply can be controlled precisely, but when there is a change in the composition of the fuel gas, the density of the fuel gas varies, causing the air and oxygen mixing ratio to vary and resulting in incomplete combustion
Solution Approach 1:
The invention changes the control parameter from mass flow rate to volumetric flow rate. By measuring the volumetric flow rate of fuel gas and calculating the calorific value per unit volume, the system adjusts air and oxygen supply based on volumetric rather than mass basis. This parameter change compensates for density variations caused by composition changes, maintaining reliable combustion.
Solution Approach 2:
The invention implements feedback control by measuring the actual calorific value per unit volume of the fuel gas, comparing it with a reference value, and using the ratio to correct the air and oxygen flow rates. This closed-loop feedback ensures that mixing ratios remain optimal even when fuel gas composition varies.
2Ease of operation
If the air and oxygen mixing ratio is adjusted based on mass flow control, then the control system is simple to operate, but it cannot adapt to changes in fuel gas composition, leading to suboptimal combustion
Solution Approach 1:
The system maintains ease of operation by automating the transition from mass flow control to volumetric flow rate control. The control device automatically calculates volumetric flow rate from mass flow measurements and applies composition-based corrections, providing adaptability without requiring manual intervention or complex user input.
Solution Approach 2:
The control system performs self-adjustment by automatically detecting fuel gas composition characteristics, calculating the appropriate air and oxygen mixing ratios, and adjusting the supply rates without external intervention. This self-service capability provides both simplicity and adaptability.
3Measurement precision
If separate measurements of fuel gas, air, and oxygen mass flows are performed for A/F control and O2/F control, then the control precision is improved, but the device complexity increases
Solution Approach 1:
The invention makes the thermal mass flowmeter serve multiple functions: it measures both the mass flow rate and, through temperature differential analysis, the calorific value per unit volume of the fuel gas. This multi-functionality eliminates the need for separate composition analysis devices while maintaining control precision.
Solution Approach 2:
The invention combines the mass flow measurement function and the composition analysis function into a single thermal mass flowmeter system. By merging these functions, the system achieves precise control without increasing device complexity.
Data Source
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AI summary
A fuel supply device supplies, to a combustion device, a mixed gas in which air and/or oxygen are mixed into a fuel gas. The fuel supply device includes: a flow rate control module (10) disposed on a supply line (10a) for the fuel gas; and flow rate control modules (20, 30) disposed on supply lines (20a, 30a) of the air and/or the oxygen. The flow rate control module (10) includes: a thermal mass flow rate sensor (3); a first calculation unit (6) that calculates the thermal flow rate (Fc) of the fuel gas from the output of the thermal mass flow rate sensor (3); a control computing unit (5) that controls the flow rate of the fuel gas via a flow rate regulating valve (2) according to the calculated thermal flow rate (Fc); a second calculation unit (7) that calculates the calculated calorific value (Qv) per unit volume of the fuel gas; and a computing unit (8) that computes the ratio (Qv/Qs) of the calculated calorific value relative to the reference calorific value (Qs) per unit volume of the fuel gas in a reference state. The ratio (Qv/Qs) is used for the control of the flow rates of the air and/or oxygen by the flow rate control modules (20, 30).