Shallow Solid-Fuel Stove Air Preheating for Clean Combustion
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Solution Overview
Problem
Conventional solid fuel heating appliances face challenges in achieving high efficiency and reducing depth while maintaining optimal combustion, leading to soiling issues and increased material and energy costs, with existing solutions being complex and expensive.
Innovation Solution
A solid fuel heating appliance design featuring a combustion chamber with a preheating system that includes a sealed envelope with orifices of decreasing size to modulate preheated air flow, concentric with the burnt gas evacuation duct, and a heat exchanger to enhance air preheating and combustion efficiency, allowing for a reduced depth without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the depth of the stove is reduced to achieve a contemporary design with panoramic vision, then the aesthetic appeal and viewing access are improved, but the combustion efficiency deteriorates and soiling of the glass window increases
Solution Approach 1:
The patent implements a nested double-envelope duct system where the primary air preheating duct is concentrically positioned within the burnt gas evacuation duct. This nested configuration allows both ducts to occupy the same spatial envelope, enabling effective heat exchange between the hot exhaust gases and incoming primary air without increasing the overall depth of the stove. The inner duct carries combustion air while the outer duct evacuates burnt gases, creating an efficient thermal coupling within the constrained depth space.
Solution Approach 2:
The patent transitions from a traditional linear air supply path to a three-dimensional concentric dual-duct arrangement. By positioning the primary air duct inside the exhaust gas duct, the system utilizes radial and axial dimensions simultaneously, creating a volumetric heat exchange configuration rather than a simple linear path. This dimensional reorganization allows comprehensive heat transfer surface area within the limited depth space.
2Shape
If conventional combustion systems are used in a narrow shallow space, then the depth is reduced for contemporary design, but the combustion efficiency becomes very average and the window soils quickly
Solution Approach 1:
The patent applies preliminary heating action to the primary combustion air by passing it through the preheating duct where it absorbs heat from the exhaust gases before entering the combustion chamber. This preheating ensures that the air reaching the combustion zone is already at an optimal temperature, promoting complete combustion from the outset and minimizing the formation of soot and combustion residues that would otherwise deposit on the glass window.
Solution Approach 2:
The patent fundamentally changes the temperature parameter of the primary combustion air by implementing the heat exchange system. The incoming cold primary air is transformed into preheated air through thermal interaction with the exhaust gases in the concentric duct arrangement. This parameter change from cold to hot air directly impacts combustion quality, ensuring cleaner burning and reduced soiling of the glass surface.
3Object-affected harmful factors
If cold air is introduced into the combustion chamber to create an air curtain preventing deposit, then the glass soiling is reduced, but the combustion is disturbed and efficiency is not optimized
Solution Approach 1:
Instead of introducing cold air as an air curtain, the patent applies preliminary heating action to the primary combustion air through the concentric duct heat exchange system. The air is preheated before entering the combustion chamber, eliminating the need for cold air curtains while maintaining combustion efficiency. This preliminary thermal preparation ensures the air is at the correct temperature for optimal combustion throughout the process.
4Productivity
If double ducts for preheating primary air are arranged in back and side walls, then good combustion is promoted, but the depth of the stove cannot be reduced significantly
Solution Approach 1:
The patent resolves the depth constraint by nesting the primary air preheating duct inside the burnt gas evacuation duct. This concentric arrangement allows both ducts to share the same spatial envelope, effectively doubling the heat exchange functionality within the same depth space. The nested configuration eliminates the need for separate back and side wall duct arrangements, enabling shallow stove design while maintaining comprehensive air preheating capability.
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 achieves efficient combustion, reduces soiling, and allows for a more contemporary design with panoramic vision, using less material and energy while maintaining high efficiency, enabling the use of less expensive fuel types.
Implementation Method 1
a sealed envelope for preheating the combustion air conveying the latter into the combustion chamber
Implementation Method 2
preheating the primary air introduced by contact with the hot walls of the chamber
Implementation Method 3
preheated in secondary or even tertiary ducts
Implementation Method 4
solid fuel heating appliance comprising a combustion chamber
Implementation Method 5
modulate the flow of preheated air released into the chamber by enveloping the flame and combustion zone according to the natural conical shape of the latter
Data Source
Figure 1A
Figure 1B
Figure 2~3A
AI summary
A solid fuel heating apparatus (1) comprising a combustion chamber provided with a glass door (4) opening to the outside, an intake device (11) for the intake of outside combustion air into said chamber, an outlet duct for the burnt gases (2) and a sealed preheating enclosure for preheating the combustion air, conveying said air to the combustion chamber, connected at a first end to the intake device (11) and ending at a second end with a plurality of openings (9) releasing the air preheated by the preheating enclosure into the combustion chamber, characterised in that the preheating enclosure consists of a set of sealed heat exchanging pipes containing the combustion gases and the burnt gases (3, 8, 12, 15, 17, 18, 19), ending with the abovementioned openings (9), which are variable in size and are arranged in such a way as to modulate the flow of preheated air released into the chamber, enclosing the flame and combustion area in the natural conical shape of said chamber.