Premixing Flapper and Fin Structure for Stable Fuel-Air Ratios
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Solution Overview
Problem
Conventional premixing devices face issues with sudden changes in air flow speed and mixing ratios due to flapper mechanisms, leading to inappropriate fuel lean mixing ratios, increased part count, and high production costs.
Innovation Solution
A premixing device with a flapper that opens and closes both the flow path and fuel gas outlet, featuring fin parts to stabilize air flow and ensure appropriate mixing ratios, reducing the need for multiple flappers and simplifying the configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flapper is used to open and close the first flow path, then the turndown ratio is increased, but the air flow speed drops suddenly and the mixing ratio becomes unstable
Solution Approach 1:
A guide wall is introduced as an intermediary component between the flapper and the fuel gas outlet. The guide wall gradually redirects the air flow direction as the flapper opens, preventing sudden changes in flow path area. This mediator smooths the transition process, maintaining stable air flow speed and mixing ratio while still enabling the flapper to control flow path opening for turndown ratio improvement.
2Device complexity
If only one flapper is used to control the first flow path, then the device complexity is reduced, but fuel gas may flow out or backflow occurs from the first fuel gas outlet
Solution Approach 1:
The flapper is designed to perform multiple functions simultaneously: it controls both the first flow path opening and the first fuel gas outlet closure. By making the flapper universal for both flow control functions, the device complexity is reduced (only one flapper needed) while maintaining reliability through the coordinated action of the flapper and guide wall that prevents fuel gas leakage and backflow.
Solution Approach 2:
The guide wall acts as a mediator that coordinates the opening/closing actions between the flapper and fuel gas flow. As the flapper moves, the guide wall gradually redirects airflow, ensuring that fuel gas outlet closure keeps pace with flow path opening, preventing both leakage and backflow while using only one flapper.
3Stress or pressure
If the first flow path is closed by the flapper, then the negative pressure on the second fuel gas outlet is strengthened, but the mixing ratio may become fuel lean when the flapper opens
Solution Approach 1:
The guide wall serves as a mediator that gradually transitions the air flow direction as the flapper opens or closes. This prevents sudden changes in the effective flow path area, ensuring that negative pressure builds up or releases gradually. Consequently, fuel gas flow remains stable and the mixing ratio stays within the appropriate range, avoiding fuel lean conditions during flapper transitions.
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 maintains stable mixing ratios and increases turndown ratio while reducing production costs by preventing sudden air flow drops and backflow, ensuring consistent fuel gas supply.
Implementation Method 1
fuel gas flows out from the first fuel gas outlet and the second fuel gas outlet to the premixing flow path due to negative pressure acting on these outlets by the air flow
Implementation Method 2
a premixing flow path in a Venturi shape that has one end side opened to outside and the other end side connected to an air suction side of a fan
Implementation Method 3
the pair of fin parts forming a gap with respect to the first blade part through which air is capable of passing
Implementation Method 4
An opening degree of the flapper changes according to an air flow rate of the first flow path such that the opening degree is smaller in the case where the air flow rate is low than in the case where the air flow rate is high
Data Source
AI summary
A premixing device includes first and second fuel gas outlets through which fuel gas is capable of flowing out to first and second flow paths partitioned by a partition wall part of a premixing flow path, using a negative pressure generated by an air flow in the first and second flow paths. The premixing device further includes: a first blade part that is provided in the first flow path and includes the first fuel gas outlet provided facing a downstream side in an air flow direction; a flapper that has an opening degree changing according to an air flow rate and opens and closes both the first flow path and the first fuel gas outlet; and a pair of fin parts that protrude at the flapper to sandwich the first fuel gas outlet and the first blade part, and form a gap with respect to the first blade part.