Fuel Gas Flow Rate Control Device for Calorific Value Stabilization
Solution Overview
Problem
Existing flow rate controlling devices for fuel gases struggle to maintain a constant calorific value during changes in fuel gas composition, leading to incomplete combustion due to variations in air and oxygen mixing ratios.
Innovation Solution
A flow rate controlling device that calculates and stabilizes the calorific flow rate of fuel gases by using thermal mass flow sensors and a calculation unit to adjust the valve opening based on the calorific value per unit volume, ensuring a uniform calorific value supply regardless of fuel gas composition changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the fuel gas supply is controlled based on mass flow measurement, then the fuel gas flow rate can be measured, but the calorific value cannot be maintained constant when fuel gas composition changes
Solution Approach 1:
The patent changes the control parameter from mass flow rate to calorific flow rate. By measuring mass flow rate and multiplying by calorific value per unit volume, the system directly controls the energy content of the fuel gas supply, maintaining constant calorific value even when composition changes
Solution Approach 2:
The patent implements feedback control by continuously measuring the calorific flow rate and adjusting the fuel gas supply to maintain the desired calorific value. The system uses the measured calorific value and mass flow rate to calculate actual calorific flow rate and adjusts accordingly
2Productivity
If air and oxygen mixing ratios are adjusted based on mass flow, then the fuel gas supply can be controlled, but incomplete combustion occurs when fuel gas composition varies
Solution Approach 1:
The system uses feedback control to continuously monitor calorific flow rate and adjust air and oxygen supply accordingly. This ensures complete combustion by maintaining proper mixing ratios based on actual energy content rather than just mass flow
Solution Approach 2:
The patent changes the control approach from mass-based to energy-based control. By using calorific flow rate as the control parameter, the system automatically adjusts air and oxygen mixing ratios to match the actual fuel gas composition, ensuring complete combustion
3Measurement precision
If thermal mass flowmeters are used to measure fuel gas supply, then mass flow can be measured, but density variations affect air and oxygen mixing ratios
Solution Approach 1:
The patent transforms the control parameter from mass flow rate to calorific flow rate by multiplying mass flow rate with calorific value per unit volume. This parameter change eliminates the need to separately compensate for density variations, simplifying the control operation
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
The device effectively stabilizes the fuel gas supply at a constant calorific value, ensuring complete combustion by adjusting the air and oxygen ratios, even with varying fuel gas compositions, and simplifies combustion control calculations.
Implementation Method 1
a thermal mass flow sensor that measures a mass flow rate of the fuel gas
Implementation Method 2
calculates a calorific flow rate, defined as a product of a volumetric flow rate of a fuel gas and a calorific value per unit volume of the fuel gas
Data Source
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AI summary
A flow rate control device includes: a fuel gas supply channel (11) having a flow rate adjusting valve (2); a thermal type mass flow rate sensor (3) arranged in the supply channel (11); a calculation unit (6) which calculates a thermal quantity flow rate (Fc) of the fuel gas defined by a product of a volume flow rate (Fv) of the fuel gas and a heat generation quantity (Qv) per unit volume of the fuel gas according to an output from the thermal type sensor (3); and a flow rate control unit (5) which controls the open degree of the flow rate adjusting valve (2) according to a difference between a control target value (Fo) for controlling the thermal quantity flow rate (Fc) and the thermal quantity flow rate (Fc) calculated by the calculation unit (6).