Composite Heat Source for Smoking Articles
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Solution Overview
Problem
Existing smoking article heat sources face challenges in producing sufficient heat for aerosol generation while being compact, ignitable, and minimizing undesirable combustion gases and mechanical stress, with issues of heat conductivity and structural integrity.
Innovation Solution
A composite heat source comprising a porous non-combustible ceramic matrix embedding combustible fuel, where the ceramic matrix controls strength, combustion kinetics, and thermal conductivity, and includes catalysts for gas decomposition, ensuring efficient heat transfer and mechanical robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the heat source is made small to fit within a smoking article, then it can be incorporated in a compact smoking article, but it may not produce enough heat for effective aerosol generation
Solution Approach 1:
The patent uses a composite heat source consisting of combustible fuel particles embedded in a porous ceramic matrix. This composite structure allows the heat source to maintain a compact size while achieving sufficient heat generation capability through the synergistic combination of fuel (for combustion) and ceramic matrix (for structural integrity and controlled porosity).
Solution Approach 2:
The porous ceramic matrix provides a three-dimensional network that supports a high loading of combustible fuel particles while maintaining structural integrity. The porosity enables adequate oxygen diffusion to sustain combustion throughout the entire volume of the compact heat source, allowing small size without sacrificing heat generation capability.
2Loss of energy
If the thermal conductivity of the heat source is increased to improve heat transfer to the aerosol-generating material, then heat transfer efficiency improves, but heat is conducted away from the burning zone causing premature self-extinguishment
Solution Approach 1:
The porous ceramic matrix provides a compromise between thermal conductivity and combustion stability. The porous structure allows sufficient heat transfer to the aerosol-generating material through the pore channels while the ceramic material itself has relatively low thermal conductivity, preventing excessive heat loss from the burning zone and maintaining combustion stability.
Solution Approach 2:
The heat source exhibits local quality variations with the ceramic matrix providing thermal insulation around the burning fuel particles while still allowing heat transfer pathways to the aerosol-generating material. This localized thermal management ensures that each fuel particle maintains its combustion while collectively transferring heat efficiently.
3Strength
If the heat source is made with high structural strength to withstand mechanical stresses, then it can withstand dropping and handling, but it may become difficult to ignite and may require higher ignition temperatures
Solution Approach 1:
The porous ceramic matrix provides mechanical strength and structural integrity to withstand handling and dropping, while the porosity allows easy penetration by the ignition flame and rapid heating of the combustible fuel particles. The porous structure enables the ignition flame to access fuel particles throughout the volume without requiring excessive ignition energy.
Solution Approach 2:
The combustible fuel particles are pre-distributed throughout the porous ceramic matrix during manufacturing, ensuring that ignition points are readily available throughout the structure. This preliminary distribution of fuel ensures easy ignition while maintaining structural strength, as the fuel-ceramic composite can be formed with adequate mechanical properties before use.
4Duration of action of moving object
If the heat source burns with limited air to extend combustion duration, then combustion duration increases, but carbon monoxide and nitrogen oxides are produced
Solution Approach 1:
The porous ceramic matrix provides controlled oxygen diffusion pathways that allow sustained combustion over extended duration while maintaining adequate oxygen supply to minimize incomplete combustion products. The pore structure regulates air-fuel mixing, enabling complete combustion even with limited overall air intake, thereby reducing carbon monoxide and nitrogen oxide formation.
Solution Approach 2:
The patent controls the combustion process by adjusting parameters such as pore size distribution, porosity level, and fuel particle characteristics to optimize the balance between combustion duration and emission levels. By carefully selecting and controlling these parameters, the heat source achieves extended burn time while maintaining low emissions of undesirable gases.
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 composite heat source effectively generates heat for aerosol production, is ignitable with minimal carbon monoxide and nitrogen oxides, and maintains structural integrity, providing a stable and efficient smoking experience.
Implementation Method 1
the thermal conductivity of the heat source should be at a level that, in use, allows effective heat transfer to the aerosol-generating material
Implementation Method 2
the combustible heat source of the smoking article is lit and volatile compounds are released from the aerosol-generating material by heat transfer from the combustible heat source
Implementation Method 3
a composite heat source capable of catalysing the decomposition of one or more potentially undesirable gases produced during combustion thereof
Data Source
AI summary
A composite heat source for use in a smoking article is provided, including a non-combustible porous ceramic matrix; and a particulate combustible fuel embedded within the non-combustible porous ceramic matrix. The non-combustible porous ceramic matrix is formed from one or more particulate materials having a median D50 particle size at least five times less than the median D50 particle size of the particulate combustible fuel. Preferably, the non-combustible porous ceramic matrix includes one or more transition metal oxides.