Premix Burner Segmented Nozzles for Combustion Stability

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Solution Overview

Problem

Premix burners face challenges in maintaining stable combustion, particularly at low combustion loads, leading to misfire and backfire issues due to fluctuations in the fuel-to-air ratio and flow rates, which can result in defects and damage to the burner and processed objects.

Innovation Solution

The premix burner design incorporates fluidically isolated first and second premixed gas passages, allowing for separate adjustment of flow rates and compositions to the nozzles, ensuring consistent flame maintenance and suppression of misfire and backfire by using a nozzle with an ignition rod and another without, thereby stabilizing combustion across varying loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the flow rate of premixed gas is reduced to operate at low combustion load, then energy consumption decreases, but backfire occurs where flame enters the fuel flow passage

Engineering Contradiction:

Improveenergy consumptionVSAvoidcombustion stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The combustion nozzles are divided into two distinct groups: first combustion nozzles with smaller cross-sectional areas for stable pilot flame operation, and second combustion nozzles with larger cross-sectional areas for high-load operation. This segmentation allows the system to maintain reliable combustion at low loads through the specialized first nozzles while avoiding backfire conditions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different combustion nozzles are given different local properties - the first combustion nozzles have smaller cross-sectional areas specifically optimized for low-flow conditions and pilot flame stability, while second combustion nozzles have larger areas for high-flow conditions. This local differentiation ensures each nozzle type operates optimally in its designated flow range

Inventive Principle:

Principle #3Local quality

2Reliability

If the cross-sectional area of combustion nozzle is reduced to increase flow velocity and prevent backfire, then misfire is suppressed, but the burner cannot operate efficiently at low combustion loads

Engineering Contradiction:

Improvecombustion stabilityVSAvoidcombustion load range

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The combustion system is segmented into first combustion nozzles with smaller cross-sectional areas for stable pilot flame operation at low loads, and second combustion nozzles with larger cross-sectional areas for high-load operation. This segmentation allows the system to maintain reliable combustion at low loads through the specialized first nozzles while avoiding backfire conditions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between different nozzle configurations based on combustion load conditions. The control unit activates only the first combustion nozzles during low-load operation, and activates both first and second combustion nozzles during high-load operation, optimizing performance across the entire operating range

Inventive Principle:

Principle #15Dynamics

3Reliability

If the flow velocity of premixed gas is increased to match or exceed flame propagation velocity to prevent backfire, then misfire is suppressed, but combustion becomes unstable at low loads

Engineering Contradiction:

Improvemisfire suppressionVSAvoidfuel-air ratio stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The first combustion nozzles with smaller cross-sectional areas are prepared in advance to provide stable pilot flame operation at low loads before the main combustion starts. This preliminary stable combustion source prevents misfire conditions from developing when the overall system operates at low combustion loads

Inventive Principle:

Principle #10Preliminary action

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 effectively maintains stable combustion and suppresses misfire and backfire, ensuring reliable operation and reducing defects and damage, even at low combustion loads, by allowing independent control of flow rates and compositions to the nozzles.

Implementation Method 1

Spark occurs at the tip of the ignition rod and ignites the premixed gas to form a flame at the outlet side of the combustion nozzle

Methodology Applied

Scientific EffectSpark: Electric Spark

Implementation Method 2

the flow velocity of the premixed gas flowing through the pipe is equal to or higher than flame propagation velocity in order to prevent backfire

Methodology Applied

Scientific EffectFlame propagation: Combustion

Data Source

PatentEP3647660B1Premix burner and heat treatment facility for metal plate

Publication Date: 2022.12.07 PRIMETALS TECHNOLOGIES JAPAN LTD

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AI summary

A premix burner for combusting premixed gas containing fuel and air mixed in advance includes a plurality of combustion nozzles including a first nozzle having an ignition rod disposed therein and a second nozzle other than the first nozzle, a first premixed gas passage for supplying the premixed gas to the first nozzle, and a second premixed gas passage for supplying the premixed gas to the second nozzle. The first premixed gas passage and the second premixed gas passage are fluidically isolated from each other.