Multi-Stage Exhaust Mixer for Urea Swirling and Cross-Flow
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Solution Overview
Problem
Current mixers in exhaust systems of internal combustion engines fail to achieve sufficient mixing of urea with exhaust gases, leading to incomplete chemical reactions and urea accumulation, which affects emission reduction efficiency and can cause system clogging.
Innovation Solution
A multi-stage mixer that converts exhaust gas flow into non-uniform, swirling, and cross-flow characteristics through a conical swirl generator, flow centralizer, and cross-flow generator, ensuring thorough mixing and preventing urea accumulation by sweeping away droplets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple structure mixers are used, then device complexity is reduced, but mixing performance is insufficient
Solution Approach 1:
The mixer is divided into three distinct stages: a first stage with a conical swirl generator that creates rotational flow, a second stage with a flow centralizer that directs flow toward the center, and a third stage with a cross-flow generator that creates cross-flow patterns. This segmentation allows each stage to perform a specific mixing function, achieving thorough mixing while maintaining a relatively simple overall structure.
2Reliability
If complex structure mixers are used, then mixing performance is improved, but system pressure loss increases and liquid crystal accumulation occurs
Solution Approach 1:
The mixer creates dynamic, time-varying flow patterns through its three-stage design. The conical swirl generator produces rotational flow that evolves over time, the flow centralizer dynamically directs flow toward the center, and the cross-flow generator creates unsteady cross-flow patterns. These dynamic flow characteristics enhance mixing efficiency while preventing liquid crystal accumulation through continuous flow variation, and the streamlined design minimizes pressure loss.
3Device complexity
If single flow structure is used, then device simplicity is maintained, but mixing efficiency is insufficient
Solution Approach 1:
The mixer transitions the flow through multiple dimensional characteristics: the first stage creates rotational/directional flow with the conical swirl generator, the second stage adds radial flow toward the center with the flow centralizer, and the third stage introduces cross-flow patterns perpendicular to the main flow direction. This multi-dimensional flow approach dramatically improves mixing efficiency by engaging fluid elements from multiple directions simultaneously.
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 multi-stage mixer extends the reaction time for urea, ensuring complete disintegration and efficient chemical reaction while preventing urea crystallization and accumulation, thereby enhancing emission reduction and system performance.
Implementation Method 1
a conical swirl generator (2), which converts the exhaust flow into a swirling flow
Implementation Method 2
a flow centralizer (3), which directs and accelerates the swirling flow towards the pipe center and forms a cross-flow
Implementation Method 3
a cross-flow generator (4), which forms a non-uniform flow structure with both swirling and unsteady flow characteristics
Implementation Method 4
Urea is sprayed into the exhaust system and enters into a hydrolysis and thermolysis reaction with the exhaust gas and ammonia is formed as a result of said reaction
Implementation Method 5
Urea is sprayed into the exhaust system and enters into a hydrolysis and thermolysis reaction with the exhaust gas
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a multi-stage mixer (1) placed in a pipe (B) found in an exhaust system for mixing the exhaust and urea (U) flow in three stages so as to convert the same into a non-uniform flow structure (D) that proceeds in both swirling and unsteady manner with swirl or reverse swirl flow characteristic (G) and cross-flow characteristics (C).