Gas-Air Mixing Device Segmentation for Combustor Turn-Down Ratio
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Solution Overview
Problem
Existing gas-air mixing devices for combustors, such as boilers and water heaters, face limitations in achieving a high turn-down ratio due to the relationship between gas consumption and differential pressure, leading to frequent on/off cycles and reduced durability, especially with pneumatic modulating gas valves where increasing differential pressure is impractical.
Innovation Solution
A gas-air mixing device with separate and divided gas and air supply paths, utilizing a latch solenoid valve with a plunger and valve body to control the flow of gas and air, allowing for increased turn-down ratio by selectively opening or closing these paths based on output mode, reducing the stroke length and manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If differential pressure is increased to double fluid flow rate, then gas consumption is improved, but differential pressure ratio becomes impractically high (9:1 for 3:1 turn-down ratio, 100:1 for 10:1 turn-down ratio)
Solution Approach 1:
The gas supply path is divided into multiple sections with separate opening/closing means. Instead of controlling gas flow through differential pressure alone, the system segments the gas supply into multiple controllable paths, allowing independent regulation of gas flow without requiring impractically high differential pressure ratios. This enables achieving high turn-down ratios without the pressure constraints that limit conventional single-path systems.
2Quantity of substance
If pneumatic modulating gas valve is used to control gas supply, then gas consumption is regulated, but the system becomes complex and cannot achieve high turn-down ratio due to pressure constraints
Solution Approach 1:
The system divides the gas supply into multiple sections, each with its own opening/closing means, replacing the need for a complex pneumatic modulating gas valve. This segmentation approach simplifies the overall system by using multiple simple on/off controls instead of one complex continuous modulation valve, while achieving better turn-down ratio performance.
Solution Approach 2:
The patent introduces a mixing chamber as an intermediary element where gas from multiple sections mixes with air before reaching the burner. This mixing chamber serves as a mediator that allows independent control of multiple gas sections while achieving the desired mixed gas flow, simplifying the control architecture compared to using a pneumatic modulating valve throughout the system.
3Productivity
If frequent On/Off cycles occur at small load volume, then turn-down ratio is small, but temperature control stability deteriorates and durability decreases
Solution Approach 1:
By dividing the gas supply into multiple sections that can be independently controlled, the system can maintain stable combustion at low loads by activating only the necessary sections rather than cycling the entire system on and off. This segmentation enables finer control of minimum gas consumption, improving temperature stability and reducing wear from frequent cycling.
Solution Approach 2:
The system dynamically adjusts gas flow by selectively opening or closing different gas supply sections based on load requirements. This dynamic control allows the system to maintain optimal combustion conditions across a wide range of loads, preventing the frequent On/Off cycling that occurs with fixed-capacity systems and thereby improving both reliability and durability.
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 solution enhances the turn-down ratio, enabling finer heat control and reduced temperature variation, improves durability with a simpler and more maintainable design, and minimizes manufacturing and maintenance costs by using identical flow directions for air and gas.
Implementation Method 1
an opening/closing means for blocking the flow of gas and air by closing the second air supply part and the second gas supply part when in low-output mode, and for opening the second air supply part and the second gas supply part to allow gas and air flow when in a high-output mode
Implementation Method 2
mixing gas and air with mixing ratio of combustion optimum state and supplying this mixture (air+gas) to a burner port for combustion
Data Source
AI summary
Provided is a gas-air mixing device for a combustor which effectively controls the amount of gas and air supplied to a burner provided in a combustor, thus improving the turn-down ratio which leads to increased convenience for using hot water and heat and enhanced durability of the burner. The gas-air mixing device for a combustor comprises: a housing, connected on one side to a turbo fan; a discharge part disposed on one side of the housing and in contact with the turbo fan; first and second air supply parts, provided on the other side of the discharge part and separated by a first partition; first gas supply part, divided by a second partition, and a second gas supply part having a protruding part; and an opening/closing means for controlling the flow of gas and air by opening or closing the second air supply part and the second gas supply part.