Mixer Box Duct Segmentation for Exhaust Gas Mixing
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Solution Overview
Problem
Existing mixer boxes for combustion engine exhaust gas fail to achieve efficient mixing of liquid additives due to inadequate droplet break-up and turbulence, leading to longer reaction times and less effective catalyst performance.
Innovation Solution
A compact mixer box design with a duct system featuring multiple duct sections and re-mixing chambers, where liquid is injected into a turbulent gas flow within the mixer box, creating enhanced turbulence and efficient mixing through parallel flows and sharp turns, eliminating the need for external injection devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional mixing box design is used, then the structure is simple, but the mixing efficiency is insufficient and reaction time is long
Solution Approach 1:
The duct system is divided into multiple duct portions (first duct portion with outer and inner walls, second duct portion surrounded by the first) creating separate flow paths. This segmentation allows parallel gas flows and multiple mixing zones, significantly improving mixing efficiency while managing complexity through modular duct sections
Solution Approach 2:
The second duct portion is nested within the first duct portion, with the outer wall of the second duct portion surrounded by the inner wall of the first duct portion. This nested configuration creates concentric flow paths that maximize mixing contact area within a compact volume, improving productivity without proportionally increasing device complexity
2Productivity
If liquid injection is performed in calm flow, then injection is simple, but droplet break-up is insufficient
Solution Approach 1:
The liquid injection means is positioned to inject liquid into the second duct portion where turbulent flow has already been established by the parallel flows from the first duct portion. This preliminary creation of turbulence before injection point ensures immediate and effective droplet break-up, improving productivity while the fixed injection positioning simplifies operation control
3Productivity
If longer piping is used to achieve mixing, then mixing is more complete, but the system becomes less compact
Solution Approach 1:
The invention transitions from linear sequential mixing to three-dimensional concentric mixing by nesting the second duct portion within the first duct portion. This dimensional arrangement creates multiple mixing interfaces simultaneously, achieving complete mixing in a compact volume rather than requiring long linear piping
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 achieves efficient mixing of fluid droplets into exhaust gas, reducing reaction time and enabling effective catalyst performance, such as in SCR systems, while maintaining a compact layout and minimizing heat loss.
Implementation Method 1
Mixing and vaporization and/or decomposition of a liquid into a gas stream are dependent on droplet break-up, turbulence in the gas flow and temperature
Implementation Method 2
Mixing and vaporization and/or decomposition of a liquid into a gas stream are dependent on droplet break-up, turbulence in the gas flow and temperature
Implementation Method 3
The injection thereby takes place at a location where the flow is turbulent. It is particularly efficient for the mixing that turbulence is present already where the liquid is injected
Implementation Method 4
Mixing and vaporization and/or decomposition of a liquid into a gas stream are dependent on droplet break-up, turbulence in the gas flow and temperature
Implementation Method 5
Mixing and vaporization and/or decomposition of a liquid into a gas stream are dependent on droplet break-up, turbulence in the gas flow and temperature
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Mixer box for mixing, vaporization and decomposition of a liquid additive to the exhaust gas flow from a combustion engine, comprising a gas inlet (108), a gas outlet (109) and internal duct means establishing a gas flow path (A-H, a-h) from the gas inlet (108) to the gas outlet (109). The duct means includes a first duct portion (107) having an outer wall (171) and an inner wall (161), which is surrounded by the outer wall (171), such that the gas flow path through said first duct portion (107) is established inbetween. The first duct portion (107) is provided with at least two partitions (121-124) extending between the outer wall (171) and the inner wall (161), which seperate the first duct portion (107) into at least two duct sections (101a, 101b, 102a, 102b) of which at least one is an upstream duct section (101a, 101b) and at least one is a downstream duct section (102a, 102b).