Exhaust Gas Mixing Device with Flow Deflection Edges
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Solution Overview
Problem
Existing mixing devices for catalytic removal of nitrogen oxides from exhaust gases are inefficient due to the need for lengthy mixing sections, sensitivity to flow conditions, and potential for ammonia slip, which can lead to clogging and require additional measures to prevent deposits and ensure homogeneous mixing.
Innovation Solution
A compact mixing device with flow separation edges that deflect the exhaust gas flow at least twice, generating turbulence for improved mixing and reducing the required mixing distance, while preventing deposits through efficient vaporization and minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional static mixers or long mixing sections are used, then homogeneous mixing of reactant with exhaust gas is achieved, but the device becomes large and requires significant space
Solution Approach 1:
The patent employs dynamic flow deflection using angled deflectors (18, 19) that actively redirect the exhaust gas stream multiple times (at least twice by 180°) through sub-channels (14, 15). This dynamic approach to flow management creates intense mixing in a compact space, replacing the need for long static mixing sections while achieving homogeneous distribution of the reactant (urea or ammonia) with the exhaust gas.
2Productivity
If liquid reactant is injected directly into hot exhaust gas, then mixing is accelerated, but solid deposits form on surfaces
Solution Approach 1:
The mixing device is segmented into multiple sub-channels (13, 14, 15) separated by partition plates (18, 19). The liquid reactant is injected into the first sub-channel (13), and through the segmented path with multiple 180° deflections, the liquid is rapidly atomized and vaporized before contacting any surfaces. This segmentation prevents deposit formation by ensuring complete vaporization occurs within the flow path rather than on solid surfaces.
Solution Approach 2:
The patent utilizes the high temperature parameter of the exhaust gas (typically 150-600°C) to rapidly vaporize the injected liquid reactant. The thermal energy parameter is harnessed to transform the liquid phase reactant into vapor phase within the mixing device, preventing condensation and subsequent deposit formation on downstream surfaces.
3Reliability
If multiple reactors are arranged in the exhaust system, then complete gas purification is achieved, but system complexity and space requirements increase
Solution Approach 1:
The patent combines the mixing function and the reactive species injection function into a single integrated mixing device structure. The deflectors and sub-channels are designed to simultaneously achieve homogeneous mixing and proper reactant distribution to the SCR catalyst. This merging of functions reduces the number of separate components needed while maintaining purification efficiency.
4Ease of operation
If flow straighteners or additional pipe lengths are added, then even flow conditions are achieved, but device length and complexity increase
Solution Approach 1:
Instead of using static flow straighteners that require additional length, the patent employs dynamic flow deflection through angled deflectors (18, 19) that actively redirect the flow multiple times. This dynamic approach to flow conditioning achieves uniform flow distribution across the SCR catalyst in a much more compact configuration, eliminating the need for additional pipe lengths or complex flow straightening devices.
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 enables efficient, compact, and adaptable mixing of reactants with exhaust gases, reducing ammonia slip and clogging risks, and facilitating effective nitrogen oxide removal with reduced system complexity and space requirements.
Implementation Method 1
deflect the exhaust gas flow at least twice by 180° each time at a flow separation edge... generating turbulence for improved mixing
Implementation Method 2
the reactant evaporates within the mixing section and has to be decomposed into NH3
Implementation Method 3
the reactive species NH3 is also formed from the urea by a hydrolysis reaction
Implementation Method 4
The liquid droplets must then be sufficiently vaporized and mixed with the exhaust gas before they hit a surface. The liquid must be finely atomized.
Implementation Method 5
deflect the exhaust gas flow at least twice by 180° each time at a flow separation edge
Data Source
Figure 1~3b
Figure 4~5b
Figure 6a~7b
AI summary
The device (200) has eccentrically arranged separating plates for limiting outer, middle and inner partial channels (202, 205, 208). A gaseous or fluid reaction medium is homogeneously distributed in exhaust gas flow, where the gas flow is supplied to a diesel particle filter or selective catalytic reduction-reactor for catalytic removal of nitrogen oxide from the gas flow according to a selective catalytic reduction-process. A deflection point (204) is formed in an inner side of the mixing device for deflecting the gas flow, and connects the channels with one another.