Separate Flow Path Gas-Air Mixing Device for Boiler Turn-Down
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Solution Overview
Problem
Existing gas-air mixing devices for gas boilers face limitations in turn-down ratio, leading to instability and efficiency issues, particularly in condensing boilers, due to high oxygen concentration and heat loss, and are hindered by the impossibility of infinitely increasing gas supply pressure and the expense of high-speed blowers.
Innovation Solution
A separate flow path gas-air mixing device with a pneumatic valve system, featuring a drive unit with vertically moving valve bodies and an air flow path branching apparatus, allows for independent control of gas and air flow paths, reducing excess air and minimizing flow noise, and eliminates the need for a blower speed controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gas supply pressure is increased to improve turn-down ratio, then turn-down ratio is improved, but it is impossible to infinitely increase supply pressure
Solution Approach 1:
The gas supply system is segmented into multiple independent flow paths (first gas flow path and second gas flow path) with separate control valves. This allows the system to achieve a wide turn-down ratio by selectively opening/closing paths and adjusting individual valve openings, rather than relying on extreme pressure changes. The segmentation enables fine-grained control of gas flow across a wide range.
Solution Approach 2:
The system uses dynamic control of multiple valves (main valve, first auxiliary valve, second auxiliary valve) to achieve variable gas flow rates. By coordinating the opening/closing and opening degrees of these valves, the system can dynamically adjust the total gas flow to achieve any desired output level within the turn-down ratio range, without requiring extreme pressure changes.
2Reliability
If air supply is increased to maintain stable combustion, then combustion stability is improved, but excess air causes heat loss and reduced thermal efficiency
Solution Approach 1:
The air supply system is divided into separate flow paths corresponding to different gas flow paths, with each air path providing localized air supply to its corresponding gas stream. This allows precise matching of air-to-gas ratios in each zone, ensuring adequate oxygen for complete combustion while minimizing excess air that would cause heat loss. The local quality principle enables independent optimization of combustion efficiency in each flow path.
3Device complexity
If single flow path is used to simplify structure, then device complexity is reduced, but turn-down ratio control precision deteriorates
Solution Approach 1:
The single flow path is segmented into multiple parallel flow paths, each with its own control valve. This segmentation transforms a simple but imprecise single-valve system into a multi-valve system that achieves superior control precision. The segmented structure allows independent adjustment of each path's flow rate, enabling fine-grained control of the total gas flow and achieving high precision across the entire turn-down ratio range.
4Productivity
If high-speed blower is used to increase air supply capability, then air supply capability is improved, but device cost and complexity increase
Solution Approach 1:
The air supply capability is enhanced not by using a single high-speed blower, but by segmenting the air supply into multiple independent paths that can be activated selectively. This allows the system to provide high total air flow when needed (by opening all air paths) while maintaining simple operation at lower loads. The segmented approach achieves high productivity without requiring an oversized, complex, or expensive high-speed blower system.
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 configuration achieves a higher turn-down ratio while maintaining thermal efficiency, reducing excess air issues, and simplifying the device structure, allowing for compact design and reduced flow loss.
Implementation Method 1
gas flows into an air supply tube by differential pressure between gas pressure of a gas supply tube and air pressure of the air supply tube
Implementation Method 2
two valve bodies connected to a rod that moves vertically up and down by magnetic force of an electromagnet
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
According to the present invention, a gas-air mixing device used in a gas boiler includes: a gas supply tube branched into a first gas flow path and a second gas flow path; an air supply tube branched into a first air flow path and a second air flow path by means of an air-flow-path branching apparatus; a pressure valve which is connected to the inlet side of the gas supply tube in order to adjust the supply rate of gas being supplied to the gas supply tube; and a drive unit in which two valve bodies are connected to a rod that moves vertically up and down due to the magnetic force of an electromagnet; and the air-flow-path branching apparatus is formed to have a slot that connects to either the first air flow path or the second air flow path, and has a joining part which the rod can pass through in a position corresponding to the slot.