Vehicle Exhaust Urea Mixer Segmentation Design
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Solution Overview
Problem
Existing after-treatment systems for vehicle exhaust gases face challenges in achieving efficient mixing of urea with exhaust gases, leading to potential crystallization and decreased reaction efficiency due to temperature and pressure drop issues, while also being bulky and costly.
Innovation Solution
A compact after-treatment system design with a urea mixer that divides the exhaust gas flow into two paths, one for mixing urea injection and another for heat exchange, ensuring efficient mixing and temperature maintenance, using a 5-bar dosing module and heat exchanger to prevent ammonia crystal formation and reduce pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a long linear mixing conduit is used to ensure correct mixing of urea and exhaust gases, then mixing efficiency is improved, but system encumbrance and volume increase
Solution Approach 1:
The mixing process is segmented into two independent paths: one path (first flow) is dedicated to urea injection and initial mixing, while the other path (second flow) is dedicated to heat exchange. These segmented flows are then recombined to achieve complete mixing, allowing the system to avoid a single long mixing conduit and reduce overall system volume.
Solution Approach 2:
The system transitions from a single-dimensional long linear mixing conduit to a multi-dimensional compact structure where two separate flow paths operate in parallel and then converge. This dimensional reorganization allows efficient mixing to occur in a compact three-dimensional space rather than requiring extended linear distance.
2Volume of moving object
If urea is injected at higher pressure to use shorter mixing conduits, then system compactness is improved, but dosing module cost and complexity increase
Solution Approach 1:
The system uses the kinetic energy and flow dynamics of the exhaust gas itself to facilitate mixing, rather than relying on high-pressure urea injection. The exhaust flow provides the necessary energy for mixing through the segmented paths and recombination, making the dosing module simpler and less prone to breakage.
3Manufacturing precision
If a long mixing conduit is used to ensure proper mixing, then mixing completeness is improved, but temperature drop of exhaust gases increases
Solution Approach 1:
By segmenting the flow into two parallel paths, the system allows heat exchange to occur independently in one path while mixing occurs in the other. When the paths recombine, the thermal energy from the heat exchange path transfers to the mixing path, maintaining temperature despite the mixing process.
Solution Approach 2:
The heat exchange path performs preliminary heating of the urea-containing flow before the final mixing stage. This preliminary thermal preparation ensures that when mixing occurs, the temperature is already maintained at levels suitable for preventing ammonia crystal formation.
4Manufacturing precision
If a long mixing conduit is used to achieve correct mixing, then mixing efficiency is improved, but pressure drop between inlet and outlet increases
Solution Approach 1:
Segmenting the flow into two parallel paths reduces the length and resistance of each individual path compared to a single long conduit. The recombination of these shorter paths achieves the same mixing efficiency while reducing overall pressure drop through the system.
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 system achieves efficient mixing of urea with exhaust gases, reducing ammonia crystal formation, maintaining reaction efficiency, and minimizing system size and cost, while maintaining acceptable pressure drop, thus enhancing the overall performance and compactness of the after-treatment system.
Implementation Method 1
a heat exchanger (41) arranged inside said mixer (12) and configured to heat said first flow (F1) with said second flow (F2)
Implementation Method 2
a mixer (12) arranged between said DOC (11) and said catalysts module (13) and configured to mix said urea solution with said exhaust gases
Data Source
Figure 1
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Figure 3
AI summary
After treatment system, ATS, (9) for a vehicle (1) comprising, fluidly connected in series, an inlet (7), a urea mixer (12) and an outlet (8), the inlet (7) being fluidly connected to an output of an engine of the vehicle (1) and the outlet (8) being fluidly connected to an outlet tube (6) of said vehicle (1), the intention being related in that ATS (9) comprises a mixer (12) provided with an dosing module (30), an inner element (31) and an outer element (32), the inner element (31) being configured so that a first flow (F1) of exhaust gas flow (F) flowing from inlet (7) into the mixer (12) flows into an inner volume (38) defined by the inner element (31) and the outer element (32) being configured so that a second flow (F2) flows in a volume (40) defined between inner element (31) and outer element (32), first and second flows (F1, F2) rejoining together in a mixing chamber (50) fluidly connected to volume (40) and to inner volume (38) downstream with respect inner and outer elements (31, 32).