SCR Mixing Pipe Layout for Additive Vaporization and Deposit Control
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Solution Overview
Problem
Existing systems for exhaust gas treatment in diesel engines face issues with the precipitation of additives before vaporization, leading to inefficient nitrogen oxide reduction in selective catalytic reduction devices.
Innovation Solution
A mixing device is installed upstream of the selective catalytic reduction device, featuring a tilted upper pipe segment and baffle/trapping plates to facilitate vaporization of additives by enhancing contact with exhaust gas heat and preventing precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a vertical overflow pipe is used to route exhaust gas, then the结构简单 (structure is simple), but liquid additive forms a liquid film that flows down and precipitates before vaporization
Solution Approach 1:
The patent introduces asymmetry by tilting the upper pipe segment at a specific angle (α) relative to the vertical direction. This asymmetric orientation prevents the liquid film from flowing straight down the pipe wall, instead causing it to accumulate and vaporize on the inner circumferential surface facing the blowing section, thereby resolving the precipitation problem while maintaining structural simplicity
Solution Approach 2:
The patent adds a dimensional element by inclining the pipe segment rather than keeping it purely vertical. This dimensional change in orientation creates a new vaporization zone on the pipe's inner surface, transforming the problem from a vertical flow issue to a controlled surface vaporization process
2Reliability
If the upper pipe segment is tilted to prevent liquid film flow, then additive precipitation is suppressed, but the device complexity increases
Solution Approach 1:
The patent applies local quality by tilting only the upper pipe segment while keeping the lower pipe segment vertical. This localized modification achieves the vaporization function where needed without unnecessarily complicating the entire pipe structure, balancing reliability improvement with device simplicity
Solution Approach 2:
The patent changes the orientation parameter of the upper pipe segment from vertical to inclined at angle α. This parameter modification fundamentally alters the liquid film behavior to enable vaporization, achieving improved reliability through a simple geometric parameter change rather than complex mechanical additions
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 device ensures effective vaporization of additives, reducing nitrogen oxides efficiently by suppressing precipitation and ensuring uniform mixing of ammonia in the exhaust gas.
Implementation Method 1
facilitate vaporization of additives by enhancing contact with exhaust gas heat
Implementation Method 2
an injector attached to the case, the injector injecting a liquid additive
Implementation Method 3
the upper pipe segment being tilted relative to the vertical direction so that the more the upper pipe segment goes vertically downward, the closer it gets to the blowing section
Implementation Method 4
ammonia needs to be produced by hydrolysis or thermal decomposition of the gaseous additive
Implementation Method 5
ammonia needs to be produced by hydrolysis or thermal decomposition of the gaseous additive
Data Source
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AI summary
To facilitate the vaporization of additives added upstream of a selective catalytic reduction device and to suppress their precipitation. A mixing device includes: a case surrounding a blowing section, through which an exhaust gas is blown out, of a filter or a catalyst; an upper pipe segment having an opening formed therein, the opening facing a direction facing the blowing section, the upper pipe segment being tilted relative to the vertical direction so that the more the upper pipe segment goes vertically downward, the closer it gets to the blowing section in a region facing the blowing section within the case; a lower pipe segment bent from a lower end of the upper pipe segment, the lower pipe segment being tilted relative to the vertical direction so that the more the lower pipe segment goes vertically downward, the further away it gets from the blowing section, the lower pipe segment extending out from the case and being connected to a selective catalytic reduction device; and an injector attached to the case, the injector injecting a liquid additive toward an area faced by the opening, the area being located outside the upper pipe segment in the case.