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Influences of Biocomponents (RME) on Emissions of a Diesel Engine with SCR
Authors: Czerwinski, Jan1; Stepien, Zbigniew2; Oleksiak, Stanislaw2; Otto, Andersen3
1University of Applied Sciences, Biel-Bienne, Switzerland (AFHB),
2Oil and Gas Institute, Krakow, Poland (INIG)
3Western Norway Research Institute, Sogndal, Norway (Vestforsk)
ABSTRACT
SCR*) (selective catalytic reduction) is regarded as the most efficient deNOx-system. In combination
with a Diesel particle filter (DPF) it represents a very important step towards zero emission Diesel
fleet.
The present paper informs about the results obtained with SCR and with blend fuels containing
different share of RME (B7, B20, B30 and B100). The investigations were performed according to
the procedures of the international network project VERTdePN. Also a combined system
(DPF+SCR) was included in the investigations.
Beside the legally limited exhaust emission components some non-legislated like NO2, N2O, NH3
and nanoparticles were measured at stationary and dynamic engine operation.
The most important findings are:
•the increased share of RME w/o aftertreatment causes an increase of NOx by higher engine load
and reduction of CO and HC; at transient operation (ETC) these tendencies are less pronounced
and only B100 shows an increase of NOx,
•with SCR alone there are no differences of NOx and of NOx reduction rate (KNOX) with
increasing RME portion; there is lowering of CO and HC,
•with DPF+SCR KNOX-values are slightly higher, than with SCR alone, due to the production of
NO2 in the catalytic DPF (upstream of SCR),
•there is excellent count filtration efficiency of DPF, up to 99.9% ; with SCR alone there is
usually a small reduction of nanoparticles concentrations (in the range of 10-20%, similar like
an usual oxidation catalyst).
In general it can be said, that some relationships of results, which are remarked at stationary
operation can disappear or even be inverted at transient operation. This is to explain with the
running chemical reactions in the aftertreatment system, which meet quite different changing
conditions (p, T and composition) during the transients.
INTRODUCTION
The removal of NOx from the lean exhaust gases of Diesel engines (also lean-burn gasoline engines)
is an important challenge. Selective catalytic reduction (SCR) uses a supplementary substance –
reduction agent – which in presence of catalysts produces useful reactions transforming NO x in N2
and H2O.
The preferred reduction agent for toxicological and safety reasons is the water solution of urea
(AdBlue), which due to reaction with water (hydrolysis) and due to thermal decomposition
(thermolysis) produces ammonia NH3, which is the real reduction substance.
+) Abbreviations see at the end of paper
A classical SCR deNOx system consists of 4 catalytic parts:
1
•precatalyst converting NO to NO2 (with the aim of 50/50 proportion)
•injection of AdBlue (with the intention of best distribution and evaporation in the exhaust
gas flow)
•hydrolysis catalyst (production of NH3)
•selective catalyst (several deNOx reactions)
•oxidation catalyst (minimizing of NH3 slip).
The main deNOx-reactions between NH3, NO and NO2 are widely mentioned in the literature [1, 2,
3, 4]. They have different speeds according to the temperatures of gas and catalysts, space velocity
and stoichiometry. All these influences cause a complex situation of reactions during the transient
engine operation.
Additionally to that there are temperature windows for catalysts and cut off the AdBlue-injection at
low exhaust gas temperatures to prevent the deposits of residues.
Several side reactions and secondary substances are present. An objective is to minimize the tail
pipe emissions of: ammonia NH3, nitrous oxide N2O, isocyanic acid HNCO and ammonium nitrate
NH4 NO3 (also known as secondary nanoparticles).
The combination of particle filtration (DPF) and of the most efficient deNOx technology (SCR) is
widely considered as the best solution, up to date, to minimize the emissions of Diesel engines.
For the use of biocomponents the limiting of impurities and phosphorus in biofuels according to the
present standards is an obligatory prerequisite for successful operation.
The present paper shows some results of research of SCR-and (DPF+SCR)-systems with different
rates of biocomponents (RME). The tests were performed at the Laboratories for IC-Engines and
Exhaust Emission Control of the University of Applied Sciences Biel, Switzerland (AFHB) in
collaboration with the BIODEG project partners.
Some results with the combined exhaust aftertreatment systems with the market fuel and
information about the VERdePN project, which focuses on the quality testing of aftertreatment
systems for retrofitting are given in [5].
NanoMet
SMPS
TESTED ENGINE, FUELS, LUBRICANT
Test engine
Manufacturer: Iveco, Torino Italy
Type: F1C Euro 3
Displacement: 3.00 Liters
RPM: max. 4200 rpm
Rated power: 100 kW @ 3500 rpm
Model: 4 cylinder in-line
Combustion process: direct injection
Injection system Bosch Common Rail 1600 bar
Supercharging: Turbocharger with intercooling
Emission control: none
Development period: until 2000 (Euro 3)
Fig. 1 shows the engine and the apparatus for nanoparticle
analytics SMPS and NanoMet in the laboratory for IC-engines, University of Applied Sciences,
Biel-Bienne.
2
Fig. 1: IVECO engine F1C and
equipment for nanoparticle
measurements in the engine
room
Fuels
Following base fuels were used for the research (Table 1):
•Shell Formula Diesel fuel Swiss market summer quality (10 ppm S) according to SN EN 590
•Rapeseed Oil Methyl Ester RME from Flamol, Berne, CH
ρ
(20°C) Hu Air min
[
kg/dm
3
][
MJ / kg
][
kg
A
/ kg
F
]
Diesel 0.832 42.7 14.52
RME 7 0.835 42.3 14.38
RME 20 0.842 41.55 14.1
RME 30 0.846 40.98 13.89
RME 100 0.88 37.2 12.49
Table 1: Fuel properties as per EU-standards Table 2: Principal parameters of the blend fuels
and further analysis of the test fuels
Table 1 represents the most important data of the fuels according to the standards and the analysis
certificates.
It can be remarked, that there are differences of density, heat value, stoichiometric air requirement and
boiling range, which have influences on the engine operation and especially on the full load
parameters. These changing fuel parameters were taken into account by the evaluation of
measurements.
The resulting fuel parameters for the blend fuels are represented in Table 2.
MEASURING SET-UP AND INSTRUMENTATION
Engine dynamometer and standard test equipment
Fig. 2 represents the special systems installed on the engine, or in its periphery for analysis of the
regulated and unregulated emissions.
Laboratory equipment employed:
•Dynamic test bench Kristl & Seibt with force transducer HBM T10F
•Volatile components:
-Horiba exhaust gas measurement devices
Type: VIA-510 for CO2, CO, HCIR, O2,
Type: CLA-510 for NO, NOx (this standard hot analyser with one reactor is marked in
this report as “1 CLD”)
-Amluk exhaust gas measurement device Type:
FID 2010 for HCFID,
•FTIR (Fourier Transform Infrared) Spectrometer (AVL SESAM) with the possibility of
simultaneous, time-resolved measurement of approx. 30 emission components – among those
validated are: NO, NO2, NOx, NH3, N2O.
- 3 -
* measured
values
Particle size analysis
To estimate the filtration efficiency of the DPF, as well
as to detect the possible production of secondary
nanoparticles, the particle size and number distributions
were analysed with following apparatus, Fig. 1:
•SMPS – Scanning Mobility Particle Sizer, TSI
(DMA TSI 3071, CPC TSI 3025 A)
•NanoMet – System consisting of:
- PAS – Photoelectric Aerosol Sensor
(EcoChem PAS 2000) indicates the
carbonaceous total surface of the aerosol
- DC – Diffusion Charging Sensor
(Matter Eng. LQ1-DC) indicates the
totale surface of the aerosol
independently of the chemical
properties
- MD19 tunable minidiluter
(Matter Eng. MD19-2E)
The nanoparticle results represented in this paper are
obtained with sampling at tail pipe with MD19 and with
thermoconditioner (300 °C).
The nanoparticulate measurements were performed at
constant engine speed (warm) with SMPS and NanoMet.
During the dynamic engine operation NanoMet and CPC
were used.
TEST PROCEDURES
According to the different objectives of the project
several test procedures were used.
After analyzing the backpressure of the system at
stationary operation in the entire engine operation map it
was decided to limit the operation range. In this limited
engine map (LEM) different steps-tests were defined. In
the present work a 7 steps-test at 2200 rpm was used,
Fig. 3.
Fig. 3 shows the limited engine map and the 7 points
steps-test.
These operating points were chosen in such way that the urea switch-on was included in the test
(between 20 % and 30 % load).
- 4 -
Fig. 2: Engine dynamometer and test equipment
Fig. 3: Limited engine map of the IVECO
F1C engine and 7 points test for SCR-
investigations
The denomination of the OP’s from other measuring series was not changed in order to keep
comparability with other projects and new OP’s were named by adding a letter 3a, 3b, 3c).
For a more detailed investigation of the tested system different sampling positions (SP) were used (see
Fig. 2):
SP 0 sampling engine out w/o aftertreatment system (same as SP1)
SP 1 sampling engine out with aftertreatment system
SP 2 sampling engine after DPF (before urea dosing) with aftertreatment system
SP 3 sampling engine at tailpipe with aftertreatment system
The dynamic testing was performed with the ETC
(European Transient Cycle), which in this work
was defined on the basis of the non limited engine
operation map (NEM), Fig. 4.
The tests have shown that the backpressure at
dynamic operation is generally lower, as at
stationary operation and therefore the dynamic
tests were performed with ETC adapted to the
entire engine operation map. Fig. 4: Torque and speed in ETC IVECO
F1C.
The tests were driven after a warm-up phase, when the engine
coolant temperature and lube oil temperature reached their stationary values (stationary points tests).
Before the start of each dynamic cycle the same procedure of conditioning was used to fix as well as
possible the thermal conditions of the exhaust gas aftertreatment system.
This conditioning was: 5 min pt. 1 and 0.5 min idling.
The test program consisted of:
•test procedures: steps-tests at 2200 rpm and ETC (NEM);
•aftertreatment systems: without, with (DPF+SCR), with SCR only;
•fuels: Diesel (ULSD), B7, B20, B30 and B100.
TESTED SYSTEMS SCR and (DPF+SCR)
The combined exhaust gas aftertreatment system (DPF+SCR) was installed on the IVECO research
engine in the ICE-laboratory in Biel, CH.
This system is designed for dynamic on-road applications.
The filters and catalysts are exchangeable moduls, for SCR alone the DPF modulus was removed.
The investigated combination is: a coated Cordierite DPF upstream and Vanadium-based SCR catalyst
downstream of the urea injection point (see scheme Fig. 2).
Additionally to the elements in the engine exhaust system an Ad Blue-tank and Ad Blue injection unit
with pump, sensors and electronic control were installed in the laboratory.
There are following sensors, which enable the open-loop control of urea dosing:
•2× Temperature sensors (PT200)
•1× AdBlue level sensor
•1× Mass Air Flow sensor
•2× NOx sensors (upstream and downstream DPF)
- 5 -
Optional: 1× NOx sensor downstream SCR catalysts for monitoring of performance.
Urea dosing and control unit has an open loop control.
Optional: GPRS Flight recorder enables:
•data logging of system performance, state and alarms on a remote server/database
•changing and checking of configuration parameters of urea dosing unit via internet.
The SCR-system, which was investigated in the present work is without mixer
(only mixing tube 1.0 m).
The DPF has a VERT-conform filtration quality, in average for NP filtration efficiency FE > 99%.
RESULTS
Variations of fuel
Fig. 5 – the increased share of RME w/o aftertreatment causes in steps-tests: increase of NOx by higher
engine load, reduction of CO and HC (here always HCFID) and slight lowering of texh (not represented)
It is to remark that all part load operating points
are driven exactly at the same torque and speed.
The full load point OP 1 in contrary has always
the same speed but the torque results from
different heat values of the used fuels. That
means the results at OP 1 are overlapped by the
effect of different torque.
At transient operation in ETC, Fig.6, these
tendencies are present, but less pronounced,
than at stationary steps-tests.
85
65
72
0
50
100
150
200
CO
[ppm]
B0
246
272
271
0
100
200
300
400
NOx 2CLD
[ppm]
17
12
6
0
5
10
15
20
HC FID
[ppm]
23
21
19
0
10
20
30
40
NO2 FTIR
[ppm]
B30
B100
Fig.5: Limited emissions in steps-test at 2200
rpm with different fuels w/o aftertreatement
Fig. 6: Emissions in ETC with different fuels
w/o aftertreatment
- 6 -
126
126
105
82
61
138
116
120
102
78
58
112
110
111
95
75
50
85
114
111
90
72
48
75
140
112
82
66
46
49
0
50
100
150
200
CO [ppm]
CO
26
23
19
18
16
10
26
22
18
16
16
9
24
20
17
16
13
11
26
21
18
18
15
12
18
14
11
11
7
7
0
10
20
30
40
50
HC FID [ppm]
B0 B7 B20 B30 B100
HC
161
202
295
429
609
663
166
206
294
425
618
687
165
208
299
438
608
633
164
212
323
459
639
712
139
216
341
433
637
690
0
200
400
600
800
1000
OP 3c
OP 3b
OP 3a
OP 3
OP 2
OP 1
NOx 2CLD [ppm]
NOx
With DPF+SCR the higher rate of RME provokes principally similar effects, which nevertheless are
superimposed by the exhaust gas aftertreatment.
Fig. 7 represents some non-legislated components in steps-test and Fig. 8 the emissions and NOx-
conversion rates in function of exhaust gas temperature with B0, B30 and B100.
The light-off of the catalysis in DPF starts already at OP 3c (texh8 180 – 200 °C) with elimination of CO
(not represented here), but the stronger deNOx effect starts at OP 3b (texh8 approx. 240 °C).
- 7 -
0
100
200
300
NOx [ppm]
tailpipe NOx
B0
B30
B100
0
10
20
30
40
50
NO2 [ppm]
tailpipe NO2
0
1
2
3
4
5
6
N2O [ppm]
tailpipe N2O
0
5
10
15
20
NH3 [ppm]
tailpipe NH3
B0
B100
B30
0
20
40
60
80
100
150 200 250 300 350 400 450
conversion NOx [ -]
exhaust temperature (t8) [°C]
KNOx (UDS)
2200 rpm
Fig.7: Unregulated emissions in steps-test at 2200
rpm with different fuels with DPF and
SCR; α=0.9
Fig.8: Comparison of emissions in steps-test
with DPF+SCR and B0, B30 and B100;
α=0.9; FTIR
- 8 -
0
17
15
0
5
20
24
0
0
0
25
31
0
10
20
30
40
NO2 (2CLD) [ppm]
NO2
0.0
0.0
7.5
3.1
2.5
10.0
0.0
0.0
1.1
8.3
2.0
9.0
1.4
2.1
0.2
1.6
6.3
0
3
6
9
12
15
OP3c
OP3b
OP3a
OP3
OP2
OP1
NH3 (FTIR) [ppm]
NH3
3.5
2.3
0.8
0.7
0.4
1.0
3.6
2.7
1.2
0.7
0.4
0.6
4.3
2.0
1.4
1.0
0.7
0.7
0
1
2
3
4
5
6
N2O (FTIR) [ppm]
B0 B3 0 B10 0
N2O
In the conditions, where NO2 is produced – in the middle range of exhaust gas temperature – RME
causes higher NO2 -values.
In the conditions where NH3 is produced RME causes lower NH3-values. The differences of NH3
nevertheless are very little and they can be interfered by some stochastic store-release-effects and
reactions in the SCR system. At full load, OP1, there is also the influence of lower torque with
increasing B-content. In spite of that the higher NOx-values at high- and full load with B100 are
confirmed.
Generally it can be stated, that there are little influences of the biocomponents in fuel on the emissions
with DPF+SCR.
Fig. 9 shows the results of interesting NOx-components in function of exhaust gas temperature with
BO, B30 and B100 for SCR alone.
In steps-tests there is no clear influence of RME portion on NOx. There is reduction of CO at higher
load and general reduction of HC (not represented here). There are very little influences on NO2 and
NH3.
The light-off of the SCR alone is with RME 100 at a slightly lower temperature, than with B0 and B30
(t 10-20 °C).
Except of that there are no other clear effects of the RME-content on the presented parameters.
- 9 -
0
20
40
60
80
100
150 200 250 300 350 400 450
conversion NOx [ -]
exhaust temperature (t8, t9) [°C]
KNOx (UDS)
t8… DPF+S CR
SCR
t9... REF
2200 rpm
0
200
400
600
800
NOx [ppm]
tailpipe
NOx
REF
DPF+SCR
SCR
FTIR - Diesel
0
20
40
NO2 [ppm]
tailpipe NO2
0
1
2
3
4
5
N2O [ppm]
tailpipe N2O
0
5
10
15
NH3 [ppm]
tailpipe NH3
DPF+SCR
REF
SCR
Fig.9: Comparison of emissions in steps-tests
with SCR and B0, B30 and B100; α=0.9; FTIR
Fig.11: Comparison of emissions in steps-tests
with DPF+SCR and SCR, with the base
fuel; α=0.9; FTIR
0
1
2
3
4
5
N2O [ppm]
tailpipe N2O
0
200
400
600
800
NOx [ppm]
tailpipe NOx
B100 B0 B3 0
0
1
2
3
4
5
NO2 [ppm]
tailpipe NO2
0
5
10
15
20
NH3 [ppm]
tailpipe NH3
B0
B30
B100
0
20
40
60
80
100
150 200 250 300 350 400 450
conversion NOx [ -]
exhaust temperature (t8) [°C]
KNOx (UDS)
2200 rpm
In dynamic operation (ETC), Fig. 10, there are no differences of NOx, NO2 and NH3 and there is
lowering of CO and HC with higher RME content.
The influence of RME on NO2 with
DPF+SCR which was remarked at stationary
operation (more NO2 with more RME in
certain texh-range) is no more present or even
inversed at transient operation. Similarly for
NH3, which was reduced by RME (with
DPF+SCR) in stationary steps-tests and is not
reduced or even increased in the dynamic
test.
In general, it can be said, that some relationships of results, which are remarked at stationary operation
can disappear or even be inverted at transient operation. This is to explain with the running chemical
reactions in the aftertreatment system, which meet quite different changing conditions (p, T) during the
transients.
3
3
1
0
5
10
15
HC FID
[ppm]
100
80
81
0
50
100
150
200
CO
[ppm]
B0
69
73
72
0
100
200
300
NOx 2CLD
[ppm]
0
1
1
0
10
20
30
NO2 FTIR
[ppm]
B0
B30
B100
B30
B100
13.2
13.0
12.2
0
10
20
30
NH3 FTIR
[ppm]
Fig.10: Emissions in ETC with different
fuels with SCR
Different exhaust aftertreatment systems
Fig. 11 represents the nitric emissions in function of exhaust gas temperature, with Diesel base fuel, for
the three investigated variants:
•reference case (Ref.) without exhaust gas aftertreatment,
•combined aftertreatment system (DPF+SCR) and
•SCR alone.
With the catalyzed DPF there is a production of NO2 in the temperature range 250 °C – 350 °C. With
the combined system (DPF+SCR) there is a slight emission of N2O (up to 4 ppm) in the lowest
temperature range and there are lower NH3- values, than with SCR alone.
The increase of NOx conversion rate KNOX is with the combined system at a slightly lower temperature
(t 10-20 °C)
Fig. 12: summarizes the conversion rates KNOX resulting from datalogging with OEM-UDS-sensors
with B0, B30 and B100 in stationary steps-tests. The remarkable NOx-conversion takes place at OP 3b
and all higher operating points. With DPF+SCR KNOX-values are slightly higher due to the production
of NO2 in the catalytic DPF (upstream of SCR).
There are principally no significant differences of KNOX with different fuels, except of more reduction
of NOx with B100 at the lowest OP3c (easier light-off with B100).
Fig. 13 represents the average NOx, NO2 and NH3 values in ETC. It is to remark that for DPF+SCR
there are in average lower NOx, higher NO2 and lower NH3, than for SCR. The tendency of higher NOx
with RME (B100) is confirmed.
286
78
43
286
82
39
311
83
62
0
100
200
300
400
500
NOx [ppm]
B0
B30
B100
23
0
3
23
1
2
19
1
2
0
10
20
30
NO2 [ppm]
13
5
13
5
8
6
0
5
10
15
20
REF
SCR
DPF+SCR
NH3 [ppm]
zero
Fig.12: NOx conversion rates with different
exhaust aftertreatment systems at stationary
operation; α=0.9; UDS-sensors; 2200 rpm
Fig.13: Average values of NOx, NO2 and NH3 in
ETC with different fuels and aftertreatment
systems; α=0.9; FTIR
1
63
81
81
76
0
76
84
84
80
0
20
40
60
80
100
KNOx [%]
DPF & SCR
SCR
B0
1
67
80
78
76
0
73
81
83
78
0
20
40
60
80
100
KNOx [%]
B30
3
69
80
79
77
6
77
81
79
76
0
20
40
60
80
100
OP 3c
OP 3b
OP 3
OP 2
OP 1
KNOx [%]
B100
The reduction efficiencies in ETC with B0, B30
and B100 and with both investigated exhaust
aftertreatment systems are depicted in Fig. 14
(reduction efficiency RE and conversion rate Kx
are synonyms, they are calculated in this figure
from the FTIR-results SP0 and SP3. With the
combined system (DPF+SCR) there are clearly
higher RE for NOx and lower RE for NO2.
There is no clear influence of biocomponent
content on the reduction efficiency (except of a
slight monotone tendency of lowering RE for
NO2 with SCR alone).
72.7
85.0
100
87.0
71.3
86.4
95.7
91.3
73.3
80.1
94.7
89.5
0
20
40
60
80
100
120
140
160
SCR
DPF+SCR
SCR
DPF+SCR
B0
B30
B100
RE NOx [%] RE NO2 [%]
Regarding the comparison of the two aftertreatment systems it can be summarized that:
•there are advantages of catalytic activity and production of NO2 upstream of SCR in the combined
system,
•the combined system has a slightly better conversion of NOx and a lower production of ammonia
NH3; there is an easier light off at slightly lower texh,
•there are no influences of biocomponents on the NOx-reduction efficiencies.
Several other non-legislated components have been measured with FTIR, among others: isocyanic acid,
hydrocyanic acid and formaldehydes. All these components have very low absolute values in the range
of some “ppms” and are not further represented in this paper.
The combined system (DPF+SCR) shows in most cases the tendency to minimize these components.
(Nano) Particles Emissions
The particle filter of the combined system had the filtration efficiency, which fulfilled the actual VERT
quality requirements (PCFE > 99 %). I was interesting to state if there are some influences of
biocomponents on the filtration resp. reduction efficiency of NP’s of the combined system (DPF+SCR)
and how is the influence of SCR alone on NP’s ?
Fig. 15 shows the SMPS particle size distribution spectra without and with SCR at OP1 with B0, B30
and B100. There is a reduction of NP count concentration due to increasing B-content. This is in
accordance with the other research results which generally state lower PM emissions with FAME’s at
full load (higher O2-content in fuel, lower accumulation mode).
The penetration nevertheless stays similar for all fuel variants at approx. 90 %. This small reduction of
nanoparticles concentration represents the diffusion losses in the mixing tube and in the SCR catalyst.
Penetration is a parameter representing the portion of particulates passing through the aftertreatment
device; it is a ratio of down – to upstream concentrations.
Penetration = 1 – filtration efficiency.
Further comparisons of trapping efficiencies in stationary and dynamic engine operation (OP1 and
ETC) are given in Table 3. The filtration efficiencies are estimated according to three parameters:
integrated particle counts in the size range 20-300 nm or CPC for dynamic operation – PCFE ; DC-
signal – DCFE; particle mass – PMFE.
Fig.14: Comparisons of
reduction efficiencies
in ETC; α=0.9; FTIR
ETC*
)
B0 B30 B100 average average
-12.50 22.01 14.81 8.11 12.05
99.66 97.06 81.02 92.58 98.95
ETC*
)
B0 B30 B100 average average
-13.12 21.79 14.20 7.62 9.05
99.67 96.80 77.71 91.39 98.52
B0 B30 B100 average
-0.65 9.51 80.07 29.65
93.25 90.73 90.17 91.38
*
)
for ETC: CPC FE
Counts 20-300 nm
Aerosol summary surface
Particle mass
PMFE [%]
SCR
DPF+SCR
OP1
OP1
OP1
DCFE [%]
SCR
DPF+SCR
SCR
DPF+SCR
PCFE [%]
not
not
not not
not
not
not
not
not
not not
not
not
not
not
not
not
not
not
not
not
Fig.15: SMPS-PSD spectra with B0, B30 and
B100 and SCR; α= 0.9; 2200 rpm/100 % load
Tab. 3: Trapping efficiencies in stationary and
dynamic operation; 2200 rpm / 100 % and ETC
With DPF+SCR and B0 there is an excellent filtration rate of 99.66 %. At this OP urea injection after
DPF is active. This trapping efficiency decreases with growing RME portion: 97.06 % with B30 and
81.02 % with B100. This tendency is confirmed by DCFE and partly by PMFE.
The increase of NP-emission after the system (SP3) is surely not attributed to any failure of DPF, but to
the effects of condensation and creation of secondary NP’s after the DPF. These effects can be due to
the high exhaust gas temperature (production of sulfates, evaporation of higher boiling HC) and to the
inter-action of the gas after DPF with the injected Ad Blue and with the SCR-system. The secondary
NP after SCR were found in 19 and they are subject of further investigations. It is probable that both:
physical interaction (enabling a more intense condensation of substances) and chemical interaction
(new products entering in the aerosol) take place. About a more detailed knowledge in this respect
further research is necessary.
For SCR alone the reduction rates of nanoparticles at OP1 (stationary operation) have fluctuating
values.
The negative value with B0 signifies an increase of NP and PM emission. With B100 there is
exceptional reduction of particle mass (PM), which is not confirmed by the nanoparticles results (PC
and DC). This picture leads to a supposition of stochastic store-release effects, a problem, which is
difficult accessible for investigations, but has to be kept in mind during the further research.
The average trapping efficiencies in dynamic operation (ETC) depict well the tendencies given by
stationary operation.
The most important findings of this section are:
•excellent particle reduction in the (DPF+SCR) system at part load and increase of nanoparticles
penetration with growing RME portion (interaction of biocomponents and secondary NP),
•little particle reduction rates with SCR alone, in the range of 10 %; hypothesis of store-release-
effects with SCR.
0.0E+0
1.5E+7
3.0E+7
4.5E+7
6.0E+7
concentration
dW/dlogDp [cm -3]
B0 REF
B30 REF
B100 REF
REF
0.0E+0
1.5E+7
3.0E+7
4.5E+7
6.0E+7
concentration
dW/dlogDp [cm -3]
B0 SCR
B30 SCR
B100 SCR
with SCR
0.0001
0.001
0.01
0.1
1
10 100 1000
penetration
diameter [nm]
B0
B30
B100
penetration
•
CONCLUSIONS
From the present tests performed at stationary engine operation in steps-tests and at dynamic engine
operation in ETC several results can be remarked. The most important are:
for RME content
•the increased share of RME w/o aftertreatment causes an increase of NOx by higher engine load and
reduction of CO and HC; at transient operation (ETC) these tendencies are less pronounced and
only B100 shows an increase of NOx,
•with DPF+SCR in the stationary conditions, where NO2 is produced RME causes higher NO2 –
values and in the conditions, where NH3 is produced RME causes lower NH3 –values,
•in dynamic tests (ETC) with DPF+SCR only higher NOx-emissions with RME 100 are to remark,
CO and HC are for all fuels at zero level (catalytic conversion),
•with SCR alone there are no differences of NOx and of NOx reduction rate (KNOX) with increasing
RME portion; there is lowering of CO and HC,
•in dynamic tests (ETC) with SCR there are no differences of NOx and there is lowering of CO and
HC with RME,
•there are generally no influences of RME-portion in fuel on the conversion values KNOX and KNO2,
•the light-off of the SCR alone is with RME 100 at a slightly lower temperature, than with B0 and
B30 (t 10-20 °C).
for exhaust aftertreatment system
•with DPF+SCR KNOX-values are slightly higher, than with SCR alone, due to the production of NO2
in the catalytic DPF (upstream of SCR),
•with DPF+SCR the CO- and HC-emissions are mostly eliminated,
•with DPF+SCR in certain range of the exhaust temperature there are higher NO2-values than with
SCR alone; these NO2-values are further increased with RME,
•with DPF+SCR the NH3-emissions are lower than for SCR,
•the reduction efficiencies in ETC with the combined system DPF+SCR, are for NOx higher and for
NO2 lower.
for nanoparticle emissions
•without aftertreatment and with increasing RME-share the maximum of the count concentration of
the PSD moves to smaller sizes and it decreases at full load,
•with DPF+SCR there is excellent filtration efficiency of DPF, up to 99.96 %,
•at stationary full load operation with DPF+SCR and with RME 100 there is an intense production
of secondary nanoparticles from the SCR part; this effect lowers remarkably the overall NP-
reduction efficiency; it is almost not visible at dynamic operation,
•with SCR alone there is usually a small reduction of nanoparticles concentrations (in the range of
10-20 %) losses in the mixing tube and in the two in line SCR catalysts; in dynamic operation this
reduction is smaller (below 10 %),
•with SCR at full load there is a slight increase of NP-counts due to the secondary NP-production,
•certain results with SCR show surprisingly high variations of reduction rates; this is explained with
the emitting dispersion during certain measuring series and has to be regarded in further research.
The emitting dispersion can originate from some memory effects (store-release) of the entire
system (engine + exhaust system). The measuring dispersion for nanoparticles is excluded by
conformity of results obtained with different measuring methods.
In general it can be said, that some relationships of results, which are remarked at stationary operation
can disappear or even be inverted at transient operation. This is to explain with the running chemical
reactions in the aftertreatment system, which meet quite different changing conditions (p, T) during the
transients.
LITERATURE
[1] Willems, F.; Cloudt, R.; van den Eijnden, E.; van Genderen, M.; Verbeek, R.; de Jager, B.;
Boomsma, W.; van den Heuvel, I.: Is Closed-Loop SCR Control Required to Meet Future
Emission Targets? SAE Techn. Paper 2007-01-1574
[2] Hosoya, M.; Kawada, Y.; Sato, S.; Shimoda, M.: The Study of NOx and PM Reduction Using
Urea Selective Catalytic Reduction System for Heavy Duty Diesel Engine. SAE Techn.
Paper 2007-01-1576
[3] Görsmann, C.: Retrofit SCRT® – A retrofit system for the simultaneous reduction of carbon
monoxide, hydrocarbon, soot particulate and oxides of nitrogen emissions from commercial
vehicles, 4. FAD – Konferenz, Dresden, Nov. 2006, p. 155.
[4] Girard, J-W.; Cavataio, G.; Lamber, Ch. K.: The Influence of Ammonia Slip Catalysts on
Ammonia, N2O and NOx Emissions for Diesel Engines. SAE Techn. Paper 2007-01-1572
[5] Czerwinski, J.; Zimmerli, Y.; Mayer, A.; Heeb, N.; Lemaire, J.; D’Urbano, G.; Bunge, R.; Testing
of Combined DPF+SCR Systems for HD-retrofitting VERTdePN. SAE Techn.
Paper 2009-01-0284.
ABBREVIATIONS
AFHB Abgasprüfstelle FH Biel, CH
Air min stoichiometric air requirement
Bxx blend fuel with biocomponent
share xx%
CFPP cold filter plugging point
CLD chemoluminescence detector
CNC condensation nuclei counter
CPC condensation particle counter
DC Diffusion Charging Sensor
DCFE diffusion charge filtration
efficiency
dePN de Particles + deNOx
DMA differential mobility analyzer
DPF Diesel Particle Filter
ECU electronic control unit
EMPA Eidgenössische Material Prüf- und
Forschungsanstalt
EPA Environmental Protection Agency
ETC European Transient Cycle
FE filtration efficiency
FID flame ionization detector
FL full load
FTIR Fourrier Transform Infrared
Spectrometer
HD heavy duty
Hu lower calorific value
ICE internal combustion engines
Kxconversion rate of “x”
LDS Laser Diode Spectrometer
(for NH3)
LEM limited engine map
MD19 heated minidiluter
NanoMet NanoMet nanoparticle summary
surface analyser (PAS + DC + MD19)
NEM nonlimited engine map
NP nanoparticles < 999 nm (SMPS range)
OEM original equipment manufacturer
OP operating point
PAS Photoelectric Aerosol Sensor
PC particle counts
PCFE particle counts filtration efficiency
PM particulate matter, particle mass
PMFE particle mass filtration efficiency
PSD particle size distribution
RE reduction efficiency
RME rapeseed oil methyl ester
SCR selective catalytic reduction
SMPS Scanning Mobility Particle Sizer
SPsampling position
TC thermoconditioner. Total Carbon
TTM Technik Thermische Maschinen
ULSD ultra low sulfur Diesel
VERT Verification of Emission
Reduction Technologies
VERTdePN VERT DPF + VERT deNOx
αfeed factor of urea dosing;
ratio: urea injected / urea stoichio-
metric; calculated by the ECU.