Premixing Apparatus Valve Timing Control
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Solution Overview
Problem
The existing premixing apparatus experiences issues with flame failure or poor combustion when switching from a small-capacity to a large-capacity state due to the interlocking mechanism maintaining the changeover valve closed until the butterfly valve rotates by a predetermined angle, leading to an excessively air-rich air-fuel mixture.
Innovation Solution
The premixing apparatus employs a butterfly valve rotated by a stepping motor with a higher driving frequency until the butterfly valve reaches a predetermined angle, and then reduces frequency to ensure the butterfly and changeover valves can be fully opened, preventing excessive air-rich states and ensuring stable combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the changeover valve is maintained closed until the butterfly valve rotates by a predetermined angle, then the air-fuel mixture can be prevented from becoming excessively gas-rich, but the air-fuel mixture becomes excessively air-rich leading to flame failure
Solution Approach 1:
The patent applies dynamics by making the interlocking mechanism dynamic rather than static. The changeover valve is held closed only during the initial rotation phase of the butterfly valve (0 to predetermined angle), and then opens automatically when the butterfly valve exceeds this angle. This dynamic control ensures the air-fuel mixture doesn't become excessively air-rich after the initial phase, preventing flame failure while maintaining combustion stability.
Solution Approach 2:
The interlocking mechanism performs preliminary action by pre-holding the changeover valve closed during the initial butterfly valve rotation. This preliminary closure prevents excessive air-rich conditions during the critical transition phase, and then releases this constraint when appropriate, allowing both valves to open together in the subsequent phase.
2Reliability
If the butterfly valve rotates slowly from closed to opened posture, then the air-fuel mixture composition can be controlled, but the transition takes longer time and combustion stability deteriorates
Solution Approach 1:
The system performs preliminary action by quickly rotating the butterfly valve through the initial phase (0 to predetermined angle) while the changeover valve remains closed. This preliminary quick rotation establishes the proper timing foundation, after which both valves open together in a coordinated manner, achieving both speed and control.
Solution Approach 2:
The patent implements dynamic control by changing the rotation speed of the butterfly valve at different phases. The valve rotates quickly during the initial phase when the changeover valve is closed, then transitions to a coordinated opening phase. This dynamic speed adjustment reduces total transition time while maintaining combustion stability.
3Productivity
If both valves open simultaneously from closed position, then the transition is quick, but the air-fuel mixture becomes excessively air-rich causing flame failure
Solution Approach 1:
The interlocking mechanism performs preliminary action by holding the changeover valve closed during the initial butterfly valve rotation. This preliminary timing control prevents both valves from opening simultaneously, instead creating a staged opening sequence that avoids excessive air-rich conditions while maintaining quick transition.
Solution Approach 2:
The system applies dynamics by making the valve opening sequence dynamic rather than simultaneous. The changeover valve is held closed during the initial phase and only opens when the butterfly valve exceeds the predetermined angle. This dynamic timing control achieves both speed and prevention of flame failure.
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 quickly passes the excessively air-rich state, preventing flame failure and maintaining optimal combustion by ensuring the air-fuel mixture remains balanced, thus avoiding poor combustion.
Implementation Method 1
a driving frequency of the stepping motor is made higher, until the butterfly valve has rotated from the closed posture toward the opening side by a predetermined set angle, than the driving frequency during the time at which the butterfly valve rotates from the set angle to the opened posture
Implementation Method 2
a cam 93 attached to an end portion of the shaft 71 of the butterfly valve 7
Implementation Method 3
a return spring 94 to urge the changeover valve 8, through the connector member 91, upward toward the opening side
Implementation Method 4
a cushion spring 95 interposed between the connector member 91 and the pressing member 92
Implementation Method 5
a premixing apparatus for mixing fuel gas with air to supply thus obtained air-fuel mixture to a burner through a fan
Data Source
AI summary
A premixing apparatus in which a downstream end of a gas supply passage is connected to a gas suction section disposed in an air supply passage on an upstream side of a fan, is provided with: a butterfly valve driven by a stepping motor, for changing over, between high and low, a ventilation resistance in that section of the air supply passage which is on an upstream side of the gas suction section; a changeover valve for changing over, between high and low, a ventilation resistance in that section of the gas supply passage which is on an upstream side of a flow control valve; and an interlocking mechanism which opens or closes the changeover valve in interlocking with the rotation of the butterfly valve and which maintains the changeover valve in a closed state until the butterfly valve has rotated from the closed posture toward the opening side by a predetermined angle. Flame failure and poor combustion are prevented at the time of changing over the butterfly valve and the changeover valve from closed posture to opened posture.When the butterfly valve is rotated from the closed posture into the opened posture, a driving frequency of the stepping motor is made higher, until the butterfly valve has rotated from the closed posture toward the opening side by a predetermined set angle, than the driving frequency during the subsequent operation of the butterfly valve.