Solid Fuel Combustor With Direct Secondary Heat Transfer for Lower NOx
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Solution Overview
Problem
Existing combustors inefficiently return secondary combustion heat to the fuel, leading to unstable combustion and increased NOx and smoke generation due to incomplete combustion, particularly when dealing with various types and sizes of solid fuels.
Innovation Solution
A combustor design that switches the combustion gas path to directly transfer secondary combustion heat to the fuel through conduction and radiation, using a primary combustion chamber with a thermally conductive wall and a secondary combustion chamber with a fireproof insulating material, along with an air supply system that optimizes air distribution to reduce NOx generation and ensure complete combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary combustion heat is transferred to supply air through heat exchanger, then combustion stability is improved, but thermal decomposition efficiency of fuel decreases
Solution Approach 1:
The patent uses the primary combustion chamber wall as an intermediary medium to transfer heat from secondary combustion gas to fuel. The wall acts as a thermal conductor that enables direct heating of fuel without requiring heat exchanger-mediated air preheating, thus resolving the contradiction between combustion stability and thermal decomposition efficiency
Solution Approach 2:
The patent extracts the heat transfer path from the conventional air preheating route and redirects it directly to the fuel. By removing the intermediate step of heating supply air through heat exchanger, the system enables direct thermal decomposition of fuel while maintaining combustion stability through optimized air supply
2Duration of action of moving object
If secondary combustion heat is concentrated on primary combustion region, then fuel combustion time is extended, but uniform combustion reaction is disrupted
Solution Approach 1:
The patent applies different thermal conditions to different regions: the primary combustion chamber wall receives concentrated heat for extended combustion, while the secondary combustion chamber provides additional heat for uniform reaction. This spatial differentiation of heat quality resolves the contradiction between combustion duration and uniformity
3Reliability
If excessive air is supplied to maintain combustion, then combustion stability is improved, but NOx generation increases
Solution Approach 1:
The patent performs preliminary heating of fuel through the primary combustion chamber wall before main combustion occurs. This pre-heating reduces the amount of air needed during active combustion to maintain stability, thereby reducing NOx generation while preserving combustion reliability
Solution Approach 2:
The patent changes the temperature parameter distribution by directing secondary combustion heat through the chamber wall to the fuel. This parameter optimization allows stable combustion at lower overall air supply levels, reducing NOx formation conditions
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 design stabilizes combustion, reduces NOx and smoke generation, and maintains efficient thermal decomposition of fuels regardless of their type, form, or moisture content, while optimizing air supply to achieve complete combustion and increased heat output in a compact device.
Implementation Method 1
secondary combustion heat is transferred by conduction and radiation through the primary combustion chamber wall to a fuel in a primary combustion region
Implementation Method 2
secondary combustion heat is transferred by conduction and radiation through the primary combustion chamber wall to a fuel in a primary combustion region
Implementation Method 3
supply air supplied through the pipe is heated and energy is supplied to firewood in contact with the pipe by thermal conduction
Implementation Method 4
supply air supplied through the pipe is heated and energy is supplied to firewood in contact with the pipe by thermal conduction and radiation
Data Source
AI summary
A solid fuel combustion device includes: a fuel supply device including a firewood feed pipe or another fuel supplier; a primary combustion chamber coupled to the fuel supply device; a secondary combustion chamber including a wall formed of a fireproof material and having a structure in which a space is formed at a side of the combustion gas outlet of the primary combustion chamber to induce primary combustion gas to be secondarily expanded and combusted; and an air supply system including at least one air supply device in an entire combustion path formed in the primary combustion chamber and the secondary combustion chamber.