Angled Injector and Mixer Design for SCR Exhaust Systems
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Solution Overview
Problem
In non-stationary applications like vehicle exhaust systems, the insufficient evaporation and mixing of liquid reductants with exhaust gases in SCR systems lead to residue deposition on catalysts, causing degradation due to geometric constraints.
Innovation Solution
An exhaust system design featuring an angled injector and a combination of a flap mixer and a helical mixer to enhance the evaporation and mixing of liquid reductants with exhaust gases before reaching the catalyst, reducing the size of droplets and minimizing deposition on the catalyst and walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the liquid reductant is injected into the exhaust gases, then the NOx reduction function is achieved, but the liquid reductant is not sufficiently evaporated and mixed before reaching the catalyst, causing residue deposition and catalyst degradation
Solution Approach 1:
The mixing region is divided into multiple stages with separate mixing devices (first mixing device with flaps, second mixing device with helical elements) arranged in sequence. Each device performs a specific mixing function, collectively achieving thorough mixing of liquid reductant with exhaust gases before the catalyst, thereby preventing residue deposition while maintaining catalyst performance.
Solution Approach 2:
The injection axis is angled relative to the longitudinal axis of the mixing region, introducing a dimensional component that enhances spray dispersion. Combined with the multi-stage mixing devices, this angular injection creates three-dimensional mixing that improves evaporation and reduces deposition on the catalyst.
2Manufacturing precision
If a fine spray injector is used to improve mixing, then the mixing quality improves, but the injector cost increases
Solution Approach 1:
The mixing devices are positioned to perform the mixing action immediately after injection, before the spray reaches the catalyst. The first mixing device with flaps and the second mixing device with helical elements create turbulence and enhance evaporation in advance, allowing the use of coarser sprays from simpler, less expensive injectors while still achieving adequate mixing quality.
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 ensures sufficient mixing and evaporation of reductants, reducing residue deposition and enabling the use of coarser sprays, thereby lowering injector costs and improving NOx conversion efficiency.
Implementation Method 1
The liquid reductant as it is evaporated and/or mixed with the exhaust gases can react with the nitrogen oxide (NOx) component of the exhaust gases
Implementation Method 2
insufficient rate of evaporation and mixing of the injected liquid reductant with the exhaust gases
Implementation Method 3
a first mixing device arranged within the exhaust passage downstream of the injector within the mixing region, said first mixing device including a plurality of flaps, wherein said plurality of flaps are inclined relative to the longitudinal axis
Implementation Method 4
The liquid reductant as it is evaporated and/or mixed with the exhaust gases can react with the nitrogen oxide (NOx) component of the exhaust gases to form water vapor and nitrogen gas
Data Source
AI summary
An exhaust system for an internal combustion engine for a vehicle is provided. The system comprises an exhaust passage with an angled injector and a plurality of mixing devices.