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NOx-Conversion Comparison of a SCR-Catalyst Using a Novel Biomimetic Effervescent Injector on a Heavy-Duty Engine

Larsson, Peter LU ; Ravenhill, Paul and Tunestål, Per LU (2019)
Abstract
NOx pollution from diesel engines has been stated as causing
over 10 000 pre-mature deaths annually and predictions are showing
that this level will increase [1]. In order to decrease this growing
global problem, exhaust after-treatment systems for diesel engines
have to be improved, this is especially so for vehicles carrying freight
as their use of diesel engines is expected to carry on into the future
[2].
The most common way to reduce diesel engine NOx out
emissions is to use SCR. SCR operates by injecting aqueous Urea
solution, 32.5% by volume (AUS-32), that evaporates prior the
catalytic surface of the SCR-catalyst. Due to a catalytic reaction
within the catalyst, NOx is converted nominally... (More)
NOx pollution from diesel engines has been stated as causing
over 10 000 pre-mature deaths annually and predictions are showing
that this level will increase [1]. In order to decrease this growing
global problem, exhaust after-treatment systems for diesel engines
have to be improved, this is especially so for vehicles carrying freight
as their use of diesel engines is expected to carry on into the future
[2].
The most common way to reduce diesel engine NOx out
emissions is to use SCR. SCR operates by injecting aqueous Urea
solution, 32.5% by volume (AUS-32), that evaporates prior the
catalytic surface of the SCR-catalyst. Due to a catalytic reaction
within the catalyst, NOx is converted nominally into Nitrogen and
Water.
Currently, the evaporative process is enhanced by aggressive
mixer plates and long flow paths. The mixer plates create extra
exhaust back pressure and cool the exhaust gases, which decreases
engine and catalyst efficiency, resulting in overall poor NOx
conversion (<40%) and higher CO2 production under real life drive
cycle conditions.
To achieve future emission legislation targets, SCR efficiency
has to be improved, especially under low catalyst temperature
conditions. It should also be noted that Ammonia slip has to be
avoided as it is now legislated against [3].
In this study a novel biomimetic effervescent aqueous urea
injector, its design inspired by the natural spray phenomenon of the
Bombardier Beetle, is used to compare against a market-leading
aqueous urea doser in comparable exhaust conditions with and
without aggressive mixer plates being installed.
The novel biomimetic effervescent injector operates by
increasing the temperature of the Urea solution inside a constant
volume chamber to its saturated vapour pressure. At the required time
of injection an electromagnetically controlled outlet valve opens
exposing the now superheated fluid to lower pressure conditions, this
results in a hot, effervescent spray being ejected which rapidly breaks
up into very fine droplets (<20um) projected at high velocity (60m/s)
into the exhaust stream targeted at the face of the SCR catalyst.
The novel biomimetic effervescent injector shows great
potential with a significant higher NOx conversion rate and lower
ammonia slip compared to the market-leading doser on a heavy-duty
engine. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
host publication
International Powertrains, Fuels & Lubricant meeting
pages
7 pages
publisher
SAE International
external identifiers
  • scopus:85060543725
DOI
10.4271/2019-01-0047
language
English
LU publication?
yes
id
c010d1d6-ee8f-47fb-97e2-81c76480f2e3
date added to LUP
2018-12-14 14:30:58
date last changed
2019-02-27 05:09:59
@inproceedings{c010d1d6-ee8f-47fb-97e2-81c76480f2e3,
  abstract     = {NOx pollution from diesel engines has been stated as causing<br>
over 10 000 pre-mature deaths annually and predictions are showing<br>
that this level will increase [1]. In order to decrease this growing<br>
global problem, exhaust after-treatment systems for diesel engines<br>
have to be improved, this is especially so for vehicles carrying freight<br>
as their use of diesel engines is expected to carry on into the future<br>
[2].<br>
The most common way to reduce diesel engine NOx out<br>
emissions is to use SCR. SCR operates by injecting aqueous Urea<br>
solution, 32.5% by volume (AUS-32), that evaporates prior the<br>
catalytic surface of the SCR-catalyst. Due to a catalytic reaction<br>
within the catalyst, NOx is converted nominally into Nitrogen and<br>
Water.<br>
Currently, the evaporative process is enhanced by aggressive<br>
mixer plates and long flow paths. The mixer plates create extra<br>
exhaust back pressure and cool the exhaust gases, which decreases<br>
engine and catalyst efficiency, resulting in overall poor NOx<br>
conversion (&lt;40%) and higher CO2 production under real life drive<br>
cycle conditions.<br>
To achieve future emission legislation targets, SCR efficiency<br>
has to be improved, especially under low catalyst temperature<br>
conditions. It should also be noted that Ammonia slip has to be<br>
avoided as it is now legislated against [3].<br>
In this study a novel biomimetic effervescent aqueous urea<br>
injector, its design inspired by the natural spray phenomenon of the<br>
Bombardier Beetle, is used to compare against a market-leading<br>
aqueous urea doser in comparable exhaust conditions with and<br>
without aggressive mixer plates being installed.<br>
The novel biomimetic effervescent injector operates by<br>
increasing the temperature of the Urea solution inside a constant<br>
volume chamber to its saturated vapour pressure. At the required time<br>
of injection an electromagnetically controlled outlet valve opens<br>
exposing the now superheated fluid to lower pressure conditions, this<br>
results in a hot, effervescent spray being ejected which rapidly breaks<br>
up into very fine droplets (&lt;20um) projected at high velocity (60m/s)<br>
into the exhaust stream targeted at the face of the SCR catalyst.<br>
The novel biomimetic effervescent injector shows great<br>
potential with a significant higher NOx conversion rate and lower<br>
ammonia slip compared to the market-leading doser on a heavy-duty<br>
engine.},
  author       = {Larsson, Peter and Ravenhill, Paul and Tunestål, Per},
  language     = {eng},
  pages        = {7},
  publisher    = {SAE International},
  title        = {NOx-Conversion Comparison of a SCR-Catalyst Using a Novel Biomimetic Effervescent Injector on a Heavy-Duty Engine},
  url          = {http://dx.doi.org/10.4271/2019-01-0047},
  year         = {2019},
}