06.or.pt.047/hjd evaluation of the suitability to ... - europa - 2013... · additionally, the...

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TNO report 06.OR.PT.047/HJD

Evaluation of the suitability to European conditions of the WNTE control zone concept as set out in the OCE GTR Performed under the Framework Service Contract No.

Date April 27, 2007 Author(s) Henk Dekker, Iddo Riemersma - TNO

Stefan Hausberger, Martin Rexeis - TUG Patrik Soltic - EMPA Heinz Steven - TUEV Nord

Assignor European Commission DG Enterprise Project number 033.13362/01.04 Classification report Title Abstract Report text Appendices Number of pages 208 Number of appendices All rights reserved. No part of this report may be reproduced and/or published in any form by print, photoprint, microfilm or any other means without the previous written permission from TNO.

All information which is classified according to Dutch regulations shall be treated by the recipient in the same way as classified information of corresponding value in his own country. No part of this information will be disclosed to any third party.

In case this report was drafted on instructions, the rights and obligations of contracting parties are subject to either the Standard Conditions for Research Instructions given to TNO, or the relevant agreement concluded between the contracting parties. Submitting the report for inspection to parties who have a direct interest is permitted.

© 2008 TNO

TNO report | 06.OR.PT.047/HJD | 4 | 177 / 208

5 Review of WNTE temperature and altitude boundaries

5.1 Proposed Ambient Condition Range

In the current WNTE proposal the WNTE emission limits apply in certain ambient conditions (temperature, humidity, altitude). For operating conditions outside of these boundaries, either the WNTE limits do not apply, or correction factors for PM and NOx have to be used, depending on the actual conditions and the ambient conditions option selected at the time of certification or type-approval of an engine.

In the latest draft GTR, References [OCE WD10, 2006], the following ambient conditions are proposed:

5.1.1 Ambient Humidity WNTE NOx limits apply without correction factors for the humidity range of 7.14 g/kg up to 10.71 g/kg (probably also the PM limits, the proposed definition is ambiguous). For ambient conditions below 7.14 g/kg, the NOx emissions shall be corrected to the level of 7.14 g/kg and for ambient conditions above 10.71 g/kg, the NOx emissions shall be corrected to the level of 10.71 g/kg.

5.1.2 Ambient Temperature The proposed minimum temperature is 12 °C. Below 12 °C, NO x and PM emissions apply only with correction factors the manufacturer has to determine. For the upper temperature limit, two options are proposed. The first option gives an upper temperature level of 35 °C. Above 35 °C, NO x and PM emissions apply only with correction factors. The second option gives a function for the maximum temperature (T=-0.00464 °C/m · A + 37.8 °C, A=altitude in m). Above this temperat ure, WNTE does not apply.

5.1.3 Altitude The maximum altitude is proposed to be 1680 meters above sea-level. In higher altitudes, WNTE does not apply.

5.1.4 Comments • In the draft GTR [OCE WD10, 2006], some definitions have to be

reconsidered. In section 5.1.3.4, ambient conditions are defined where the use of an AECS is not allowed (1600 m, 2…35°C). The se conditions are different from the ambient conditions mentioned above. The reasonability of this difference has to be checked.

• From a physical point of view, the altitude is not a meaningful parameter. The definition of an ambient pressure range would be correct. If the altitude-definition should remain, the coordinate system has to be defined (e.g. the World Geodetic System 1984, WGS84).

5.2 Ambient Conditions across Europe

To assess if the proposed conditions limits cover a large part of the ambient conditions in Europe, Europe's weather data was analysed. "Global Surface


Summary of Day" data, available from the U.S. NOAA website (www.ncdc.noaa.gov), was used. This data set contains summary data (e.g. average temperature, minimum and maximum temperature, humidity) for over 8000 stations worldwide.

5.2.1 Weather Stations In order to evaluate the European weather, weather data from European countries was selected. Additionally, the latitude range was limited to 34 °…71°, the longitude range was limited to -24°… 32°, and only weather st ations with an altitude below 2000 meters above sea level were considered. This resulted in about 1800 European weather stations. Figure 5.1 depicts the positions of these stations and Figure 5.2 depicts the frequency of their altitudes. About 85% of the weather stations are located at altitudes below 200 m.

Figure 5.1 Positions of the weather stations

-20 -10 0 10 20 3035

40

45

50

55

60

65

70

longitude [°]

latit

ude

[°]

altit

ude

[m.a

.s.l.

]

0

200

400

600

800

1000

1200

1400

1600

1800

2000


0 200 400 600 800 1000 1200 1400 1600 1800 20000

500

1000

1500

2000

2500

3000

3500

station altitude [m.a.s.l.]

num

ber

of s

tatio

ns

Figure 5.2 Altitude frequency of the weather stations

For the evaluation, the weather data from the year 2005 (January 1st to December 31st) was used. All in all, about 630.000 data points were analysed per analysed parameter.

5.2.2 Time Series of Average Temperature and Humidity Figure 5.3 and Figure 5.4 depicts the average respectively the maximum daily temperature data of all weather stations. Averaged over all days and all weather stations, the average temperature is 9.6 °C. The ma ximum/minimum daily temperature is 4.1 °C above/below the average daily temperature. As Figure 5.3 indicates, the average daily temperatures of Europe's weather stations measure very often temperatures below the lower WNTE limit.


Figure 5.3 Average daily temperatures of all weather stations

Figure 5.4 Maximum daily temperatures of all weather stations

As Figure 5.3 indicates, the average daily temperatures of Europe's weather stations measure very often temperatures below the lower WNTE limit. The average temperatures are very rarely above 35°C (temperatur e option A). The following table lists the exceedance percentage for the whole year 2005 and for all considered European stations. The numbers show clearly, that both options for the upper temperature limit cover the European situation by nearly 100% so that from a European point of view, both options are equivalent.

Table 5.1: Percentage of measurements of all stations for the whole year 2005 above the maximum temperature (options A and B)

Max. temperature Option A

Max. temperature Option B

Average daily temperature 0.001% 0.0005% Maximum daily temperature 0.165% 0.096%

proposed zone

for WNTE

limits w/o

corrections

proposed zone

for WNTE

limits w/o

corrections


Figure 5.5 depicts the average daily humidity data of all weather stations. The data is discussed in more detail in the following sections.

Figure 5.5 Average daily humidity of all weather stations

5.2.3 Temperature/Humidity-Distribution of the Weather Conditions This section presents the distribution of the humidity and temperature. In order to make a classification of the ambient condition data according to the WNTE proposal option A, the conditions are divided in the 9 zones as shown in Figure 5.6.

Figure 5.6 Classification of the weather data

5.2.3.1 Average Daily Temperature versus Average Daily Humidity Figure 5.7 depicts the average measured humidity versus temperature of the whole year 2005 and for all stations. The influence of the saturation vapour pressure curve of water on the absolute humidity is clearly visible; no air/water vapour mixture can lie in the "cold&wet zone".

proposed zone

for WNTE

limits w/o

corrections


Figure 5.7 Average daily humidity versus average daily temperature (year 2005 data)

Figure 5.8 depicts the frequency distribution of the data. Averaged over all weather stations and the whole year 2005, the average temperature and humidity lied only during 20.4% of time in the proposed WNTE zone. Very often, the weather is colder and drier or the temperature lies within the WNTE zone but the humidity is higher than 10.71 g/kg. Looking at the average daily temperatures, the proposed upper temperature limit of 35°C is high enough.

0 5 10 15-10

0

10

20

30

40

50

Fre

quen

cy (

%)

humidity [g/kg]

aver

age

tem

pera

ture

[°C

]

1

2

3

4

5

6

7

8

9

Figure 5.8 Frequency distribution of the average daily temperature / average daily humidity (year 2005)

5.2.3.2 Maximum Daily Temperature versus Average Daily Humidity

WNTE

zone

dry

zone

wet

zone

cold

zone

hot zone hot&dry zone hot&wet zone

cold&dry

zone

cold&wet

zone

WNTE

zone

(total 20.4%)

dry

zone

(total 2.5%)

wet

zone

(total 18.5%)

cold

zone

(total 11.4%)

hot zone

(total 0%)

hot&dry zone

(total 0%)

hot&wet zone

(total 0%)

cold&dry

zone

(total

cold&wet

zone

(total 0%)


Unfortunately, the data base used does not include minimum/maximum humidity data but only daily average humidity data. Therefore, Figure 5.9 depicts the frequency distribution of the maximum daily temperatures (usually around noon) versus the average daily humidity. Looking at maximum daily temperatures, there are still only very few events above 35°C. During t he hottest daily conditions, on the overall average, 28.2% of the conditions fall in the proposed WNTE ambient conditions zone.

0 5 10 15-10

0

10

20

30

40

50

Fre

quen

cy (

%)

humidity [g/kg]

max

imum

tem

pera

ture

[°C

]

0

1

2

3

4

5

6

7

Figure 5.9 Frequency distribution of the maximum daily temperature / average daily humidity

(year 2005)

5.2.3.3 Minimum daily temperature versus Average Daily Humidity Looking at the minimum daily temperature (usually during late night) versus average humidity of the year 2005, the situation is depicted in Figure 5.10.

WNTE

zone

(total 28.2%)

dry

zone

(total 11.3%)

wet

zone

(total 18.2%)

cold

zone

(total 3.5%)

hot zone

(total 0%)

hot&dry zone

(total 0%)

hot&wet zone

(total 0.3%)

cold&dry

zone

(total

cold&wet

zone

(total 0%)


0 5 10 15-10

0

10

20

30

40

50

Fre

quen

cy (

%)

humidity [g/kg]

min

imum

tem

pera

ture

[°C

]

0

1

2

3

4

5

Figure 5.10 Frequency distribution of the minimum daily temperature / average daily humidity (year 2005)

5.2.3.4 Influence of a Widening of the Proposed Humidity/Temperature Range Looking at the results presented in the sections 5.2.3.1 to 5.2.3.3 it is clear, that the proposed WNTE ambient conditions zone (12…35°C, 7.1 4…10.71 g/kg) covers the European weather conditions very insufficiently. Behind this conclusion is the assumption that the weather stations analysed represent the positions and densities of the heavy duty traffic. If a substantial part of real European ambient conditions should be covered without the use of correction factors, the minimum temperature and the ambient humidity range should be widened. From a European point of view, there is no motivation to increase the maximum temperature limit, but a decrease of the minimum temperature limit and a widening of the humidity range would be necessary to cover a substantial part of real European weather conditions. To estimate the influence of a wider ambient conditions zone, the weather data was analysed for lower minimum temperature limits as well as for wider humidity limits. Figure 5.11 presents the nomenclature used.

WNTE

zone

(total 6.6%)

dry

zone

(total 0.5%)

wet

zone

(total 16.1%)

cold

zone

(total 25.2%)

hot zone

(total 0%)

hot&dry zone

(total 0%)

hot&wet zone

(total 0%)

cold&dry

zone

(total

cold&wet

zone

(total 2.3%)


Figure 5.11 Nomenclature for the wider zone investigation

Figure 5.12, Figure 5.13 and Figure 5.14 depict the influence on the European coverage over the year 2005 for lower minimum zone temperatures and increased humidity ranges for the average, for the minimum and for the maximum daily temperatures of all weather stations.

minimum zone temperature [°C]

delta

hum

idity

ran

ge [

g/kg

]

80

70

60

50

40

30

contour label: coverage of average 2005 daily conditions (%)

0 2 4 6 8 10 120

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Figure 5.12 Influence of the ambient conditions range on the European average conditions coverage

current proposal



delta

hum

idity

ran

ge [

g/kg

]

70

60

50

40

30

20

10

contour label: coverage of minimum 2005 daily conditions (%)

0 2 4 6 8 10 120

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Figure 5.13 Influence of the ambient conditions range on the European minimum conditions coverage


delta

hum

idity

ran

ge [

g/kg

] 80

70

60

50

40

30

contour label: coverage of maximum 2005 daily conditions (%)

0 2 4 6 8 10 120

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Figure 5.14 Influence of the ambient conditions range on the European maximum conditions coverage

If the minimum zone temperature would be lowered to 5°C and the humidity range would be widened by 3 g/kg to 4.14…13.71 g/kg, about 65 % of the average European conditions could be covered (instead of 20% with the current proposal of 12 °C and 7.14…10.71 g/kg). ACEA presented the "EU normal operating conditions" at the 9th WWH meeting [OCE WD23, 2005]. In this work, the vehicle-kilometre-frequencies of ambient temperatures, and altitudes in the EU15 countries were analyzed. The ambient humidity was not analyzed. The study showed that 90% of vehicle kilometres are driven at altitudes below 1000 m.a.s.l., less than 1% of vehicle kilometres are driven above 25°C and about 10% of vehicle kilometres are driven below 2°C. These findings point out that minimum temperature is a key point for the European situation; the data corresponds well with the data presented above.

current proposal

current proposal


5.2.4 Geographical Distribution of the Weather Conditions So far, only overall European data was discussed. In this section, the data is presented in a geographical sense to indicate, which regions are well and which regions are badly covered with the current ambient condition zone proposal. As Figure 5.15 shows, northern- and central European countries lie very often outside of the proposed WNTE zone in the cold and dry zone. Southern European countries lie very often in the wet zone. It can be concluded that:

• a lower minimum range temperature and a lower minimum range humidity would include the northern- and central European countries better

• a higher maximum range humidity would include the southern European countries better

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

hot&dry: T > 35°C & humidity < 7.14 g/kg

total :0.00016%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

hot: T > 35°C & humidity 7.14...10.71 g/kg

total :0.00016%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

hot&wet: T > 35°C & humidity > 10.71 g/kg

total :0.0016%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

dry: T 12...35°C & humidity < 7.14 g/kg

total :2.56%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

in WNTE ambient boundaries

total :20.4%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

wet: T 12...35°C & humidity > 10.71 g/kg

total :18.5%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

cold&dry: T < 12°C & humidity < 7.14 g/kg

total :47.2%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

cold: T < 12°C & humidity 7.14...10.71 g/kg

total :11.4%

latit

ude

[°]

0

20

40

60

80

100

-20 -10 0 10 20 30

40

50

60

70

Fre

quen

cy (

%)

longitude [°]

cold&wet: T < 12°C & humidity > 10.71 g/kg

total :0%

latit

ude

[°]

0

20

40

60

80

100

Figure 5.15 Geographical distributions of the average daily temperatures in the different temperature/humidity zones across Europe

5.3 Influence of Ambient Conditions on the Gaseous Emissions of a Euro III Vehicle

In order to quantify the influence of the ambient conditions on the real-world emissions, measurements performed with a Euro III truck-trailer driven across the Swiss Alps were analysed.

5.3.1 Description of the PEMS Experiment Setup


The measurements were performed by EMPA in August 2003 using a PEMS device. No particle emissions were measured. A detailed report [Soltic, 2004] of the measurements can be downloaded from www.empa.ch/orm. The vehicle had a turbocharged Euro III engine with a displacement of 12.1 litres, a nominal power of 309 kW and a nominal torque of 2000 Nm. A robotised manual transmission was used to minimise the influence of the driver's gear changing habit. Figure 5.16 depicts the setup of the vehicle.

Figure 5.16 Setup of the vehicle

For the European road freight transport across the Alps, the following alp-crossing transitions are the most important (source: Swiss Federal Office for Spatial Development, www.are.admin.ch)

1. Brenner (Austria), 31.5 million net tons in 2004, peak altitude 1375 m 2. Frejus (France), 18.6 million net tons in 2004, peak altitude 1312 m 3. Gotthard (Switzerland), 9.9 million net tons in 2004, peak altitude 1175 m

The PEMS experiments presented here were performed on the Gotthard tunnel route (Zürich-Gotthard-Bellinzona-Gotthard-Zürich) crossing the Alps twice (total trip length approx. 400 km). The vehicle was loaded to its maximum allowed mass of 40 tons.

5.3.2 Ambient Conditions during the PEMS Experiment This trip did not exceed the proposed maximum WNTE altitude of 1680 m, but the influence of the ambient temperature and humidity on the emissions could be studied. The experiment discussed here was performed on a very hot summer day (August 7, 2003). Figure 5.17 depicts the ambient temperature and the air temperature after the vehicle's intercooler for the trip. Additionally, the proposed options (A) and (B) for the maximum temperature are plotted. Option (A) foresees an introduction of an emission correction if the maximum temperature of 35°C is exceeded. Option (B) excludes emissions above the maximum temperature (which is a function of the altitude). As it can be seen, the maximum temperature was exceeded during about one third of the time, independently which maximum temperature option is applied.


Figure 5.17 Temperature profiles for the whole trip twice across the Alps

Figure 5.18 depicts the measured humidity profile. The humidity was very often above the proposed upper limit of 10.71 g/kg.

Figure 5.18 Humidity profiles for the whole trip twice across the Alps

Figure 5.19 depicts the resulting frequency distribution of the ambient temperature and the ambient humidity. As it can be seen, the ambient conditions are quite well distributed in the proposed WNTE zone and in the zones with higher temperatures and/or higher humidity’s.

0 50 100 150 200 250 300 350 40015

20

25

30

35

40

45

50

55Option A (Tmax=35°C): 34% of time with correctionOption B (Tmax=37.8-0.00464*altitude): 32% of time invalid measurements

driven distance [km]

tem

pera

ture

[°C

]

ambient temperature

temperature after intercooler

0 50 100 150 200 250 300 350 400

6

8

10

12

14

16

driven distance [km]

ambi

ent

hum

idity

[g/

kg]

above upper limit of 10.71 g/kg(NOx correction to 10.71 g/kg required)

below lower limit of 7.14 g/kg(NOx correction to 7.14 g/kg required)

42% of time without correction


Figure 5.19 Frequency distribution of humidity and temperature

5.3.3 Engine Operation in the Different Zones In order to gain information if and how the ambient conditions influence the gaseous emissions, the data was sorted:

1. according to the membership to the different ambient condition zones shown in Figure 5.19

2. according to the membership to the engine-map based WNTE window (applying no time restriction, applying the proposed 30s time restriction and applying a 10s time restriction)

As an example, Figure 5.20 depicts the frequency distributions of the engine operating points for all periods where the ambient conditions lie within the proposed zone of 12°C…35°C ambient temperature and 7.14…10.7 1 g/kg ambient humidity. The position of the average operating point ("AOP") is also marked. It is obvious, that the AOP for the case when no engine operating points are excluded lies at a lower speed and load than for the cases where the proposed WNTE window excludes engine operating points with low speed and load. However, the cases where only measurements within the WNTE window are considered show nearly the same "AOP", regardless if no time restriction, a 30s restriction or a 10s restriction was applied. This behaviour is obviously only true for this specific case with a high-loaded vehicle driving uphill for a long time where long high-load engine operation results. The experiment was long enough (over 6h) that enough data could be sampled for all cases. The frequency distributions and therewith the "AOP" for the other cases considered (wet zone, hot&wet zone, etc.) were very similar (the distributions are not shown for readability reasons) so that a good comparability of the emissions is given.

2 4 6 8 10 12 14 16 1820

25

30

35

40

45

Fre

quen

cy (

%)

ambient humidity [g/kg]

ambi

ent

tem

pera

ture

[°C

]

0

1

2

3

4

5

6

WWNNTTEE zzoonnee

((2288..77%%))

wweett zzoonnee ((3377..88%%))

hhoott&&wweett zzoonnee

((1199..22%%))

hhoott aanndd hhoott&&ddrryy zzoonnee

((1199..22%%))


Figure 5.20 Frequency distribution of the engine operating points within the proposed ambient conditions boundaries for different WNTE window options

5.3.4 Ambient Conditions- and Engine Map Restriction Influence on Brake Specific NOx Emissions Figure 5.21 shows the measured NOx emissions evaluated according to the different restrictions described in the sections above.

• The NOx Emissions showed a rather small influence on the WNTE engine map window residence time parameters. Even if the whole trip is evaluated (regardless if the operating point is in the WNTE window or not), the brake specific emissions are similar (although the AOP of the engine collective load is lower). The reason is the rather constant brake specific NOx emission behaviour over a broad engine map area.

• The NOx emissions were highest for the proposed temperature and humidity range and they showed to be a little lower for operation in the same humidity range at higher temperatures; one would not expect this. The reason for this behaviour is most likely that the vehicle drove faster during the highest ambient temperature periods and the intercooler performs better at higher vehicle speed.

A conclusion from this result is that the ambient temperature is not directly transferable to the temperature the cylinders aspirate and therefore a rather unsafe boundary parameter regarding on-road emissions

1000 1500 2000

0

500

1000

1500

2000

Fre

quen

cy (

%)

"AOP"

engine speed [rpm]

within ambient boundaries: 6264s=28.7%

g/kWh CO2g/kWh COg/kWh THCg/kWh NOx

6641.410.1435.63

brak

e to

rque

[N

m]

0

2

4

6

8

10

1000 1500 2000

0

500

1000

1500

2000

Fre

quen

cy (

%)

"AOP"

engine speed [rpm]

in WNTE window: 3293s=15.1%


6521.280.1055.43

brak

e to

rque

[N

m]

0

5

10

15

20

1000 1500 2000

0

500

1000

1500

2000

Fre

quen

cy (

%)

"AOP"

engine speed [rpm]

in WNTE window and 30s rule: 2731s=12.5%


6560.8590.1015.49

brak

e to

rque

[N

m]

0

5

10

15

20

1000 1500 2000

0

500

1000

1500

2000

Fre

quen

cy (

%)

"AOP"

engine speed [rpm]

in WNTE window and 10s rule: 3052s=14%


6551.060.1045.45

br

ake

torq

ue [

Nm

]0

5

10

15

20


0

1

2

3

4

5

6

whole trip within WNTEengine map

window

within WNTEand 30'window


NO

x [g

/kW

h]

all ambient conditions

WNTE ambient conditionszone

wet zone

hot&wet zone

hot and hot&dry zone

Figure 5.21 Brake specific NOx emissions for the different ambient condition- and engine map

window membership cases

5.3.5 Ambient Conditions- and Engine Map Restriction Influence on Brake Specific THC Emissions Figure 5.22shows the measured THC emissions evaluated according to the different restrictions described in the sections 5.3.2 and 5.3.3.

• Regarding THC Emissions, all results are very similar, regardless if all events within the WNTE window are evaluated or if time restrictions are applied. THC emissions seem to behave “quasi-static”.

• The ambient conditions do not seem to have an important influence on the THC emissions.

• When the THC emissions outside the WNTE window are included, the THC emissions increase remarkably. The main reason is hat the engine showed rather high (lubricant-borne) THC emissions during phases when the vehicle was braked using the engine brake. Because the engine brake was used very heavily during the long downhill phases, these emissions played an important role in the overall emissions.


0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

whole trip withinWNTE

engine mapwindow

withinWNTE and30' window

withinWNTE and10' window

TH

C [

g/k

Wh

]



wet zone

hot&wet zone


Figure 5.22 Brake specific THC emissions for the different ambient condition- and engine map window membership cases

5.3.6 Ambient Conditions- and Engine Map Restriction Influence on Brake Specific CO Emissions During the on-road measurements, frequent calibration checks were performed. Whereas the other analysers worked very stable regarding time, barometric pressure and ambient humidity, the CO analyser did not. The CO analyser drift did not correlate with time, humidity or pressure. Therefore, the CO measurement results have to be regarded as rather unsafe and conclusions could not be drawn from the measured results.

5.3.7 Ambient Conditions- and Engine Map Restriction Influence on Brake Specific CO2 Emissions CO2 emissions are not in the focus of the WNTE approach. They are discussed here because concepts were suggested that do not rely on brake specific emissions but on CO2 (or fuel) specific emissions. It is well known that CO2 emissions of warmed-up engines behave “quasi-static”, i.e. the transient engine operation can be regarded as a sequence of static operating points. Therefore, the residence time restrictions within the WNTE zone do not show any influence on brake specific CO2 emissions (especially because the brake specific fuel consumption usually does not vary very much within the WNTE zone). CO2 Emissions of the engine investigated here are lowered with increased ambient temperature and increased humidity.


0

100

200

300

400

500

600

700

whole trip within WNTEengine map

window



CO

2 [g

/kW

h]



wet zone

hot&wet zone


Figure 5.23 Brake specific CO2 emissions for the different ambient condition- and engine map window membership cases

5.3.8 Ambient Conditions Influence on CO2 Specific NOx Emissions In Figure 5.24, the work- and CO2 specific NOx emissions are compared in a relative sense for the different ambient condition zones. It can clearly be seen, that this Euro III engine showed a reduced sensitivity on the ambient conditions when the NOx emissions are evaluated in a CO2 specific sense. The standard deviation over all cases is reduced from 7.1% to 3.4%.

within WNTE engine map and 30' window

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

all ambientconditions

WNTEambient

conditionszone

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Figure 5.24 Comparison of work- and CO2 specific NOx emissions


5.3.9 Ambient Conditions Influence on CO2 Specific THC Emissions In Figure 5.25, the work- and CO2 specific THC emissions are compared in a relative sense for the different ambient condition zones. It can also for THC clearly be seen, that this Euro III engine showed a reduced sensitivity on the ambient conditions when the THC emissions are evaluated in a CO2 specific sense. The standard deviation over all cases is reduced from 4.2% to 1.2%.

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Figure 5.25 Comparison of work- and CO2 specific THC emissions

5.3.10 Comments and Conclusions on the PEMS Results The transalpine long-haul trip (6h 4‘) discussed here had no urban driving situations. The conclusions are not necessarily transferable to other vehicles in other driving situations. The more restrictions are made regarding residence time within the WNTE window, the more only few engine operating points are covered. For the trip discussed here, either full load operation (long uphill driving) or constant speed cruising operating points (e.g. at 90 km/h using cruise control) are dominant for the time-restricted WNTE evaluation. For the total of 6h 4’ measurement time, enough WNTE events are covered with the 30’ as well as with the 10’ rule. The emission values difference between these two residence time restrictions is rather small. This conclusion is obviously not true for vehicles measured in urban driving situations. Looking at CO2-specific NOx and THC emissions, the influence on ambient parameters is clearly reduced (further investigations are needed to validate this conclusion for other engine technologies and other pollutants as CO and PM)


5.4 Assessment of the Ambient Conditions Influence on Newer Engine Technologies

The engine technology discussed in section 5.3 was relatively simple. The engine had no exhaust gas recirculation (EGR), no exhaust gas after treatment system and relatively inflexible injection possibilities. As a result the emission behaviour of this technology is also relatively simple. Current engines (Euro IV & V) have either a NOx or a PM after treatment system with feed forward- or/and feedback control functions. Future technologies (Euro VI) will combine NOx and PM after treatment (EGR plus SCR plus a particle trap). Engines with controlled exhaust gas after treatment systems usually do not have simple emission behaviour anymore: the structure and the application of the control system dominate the emission behaviour, especially during transients. Therefore, no scientifically sound prediction on the emission behaviour of future technologies can be made. To do so, a representative sample of different technologies from different manufacturers will have to be experimentally investigated in the future. However, all engines that have an active NOx reduction after treatment system (SCR) have to guarantee an accurate urea dosing according to the actual engine-out NOx level. This level can either be estimated using the measured ambient conditions (temperature, pressure, humidity) and several engine states as an input or directly measured using a NOx sensor. Regarding NOx, it is therefore very likely that engines with SCR technology have a reduced sensitivity to ambient conditions. Especially for these new technologies with controlled after treatment systems it is questionable if any limitation or correction on the ambient conditions (besides of the ambient pressure) should be introduced.

5.5 Summary

In the current WNTE proposal the WNTE emission limits apply in certain ambient conditions (temperature, humidity, altitude). For operating conditions outside of these boundaries, either the WNTE limits do not apply, or correction factors for PM and NOx have to be used, depending on the actual conditions and the ambient conditions option selected at the time of certification or type-approval of an engine.

A review of the European situation shows that the proposed WNTE ambient conditions zone covers the altitudes well, but that the ambient temperature and humidity conditions are covered only weakly. Using the current definition (12…35°C, 7.14…10.71 g/kg), the European ambient co nditions are covered during only about 20% of the year without the use of correction factors.

If the minimum zone temperature would be lowered to 5°C and the humidity range would be widened by 3 g/kg to 4.14…13.71 g/kg, about 65 % of the average European conditions could be covered (instead of 20% with the current proposal of 12 °C and 7.14…10.71 g/kg).

The findings regarding the European temperature boundaries are very much in line with an earlier ACEA study [OCE WD23, 2005], which did not consider the ambient humidity.

The analysis of the year 2005 weather data shows, that the maximum temperature concepts for options A and B of the current proposal are equivalent from a European perspective. The maximum daily temperatures of all analyzed weather stations are above the maximum temperature defined by both options for far less than 1% of the time.


If a substantial part of real European ambient conditions should be covered without the use of correction factors, the minimum temperature and the ambient humidity range should be widened.

The current WNTE proposal counts emissions on a "per work" base (i.e. g/kWh) as normal type-approval regulations do for emissions measured on engine dynamometers. Because it is rather complicated to measure the engine work precisely on the road, there are good reasons to limit the emissions in a fuel- or CO2 specific manner. Looking at NOx and THC emissions of a Euro III engine measured in a vehicle with a PEMS system, the CO2 specific emissions clearly show a reduced sensitivity to the ambient conditions when compared with the brake specific emissions. This was not checked for other pollutants.

The ambient conditions have no direct connection to the emissions. The emissions for given ambient conditions can vary quite intensely, e.g. due to different intercooler efficiencies caused by different vehicle speeds in different road slopes.

It is expected, that future engines with controlled NOx and/or PM after treatment systems will have a reduced sensitivity on the ambient temperature and humidity. It is therefore worth to think about a widened ambient temperature and humidity zone without the need to use correction factors.


7 Glossary

BS Brake Specific BSFC Brake Specific Fuel Consumption CO Carbon monoxide ESC European Steady state engine test Cycle ETC European Transient engine test Cycle FC Fuel Consumption GTR Global Technical Regulation GVM Gross Vehicle Mass HC Hydrocarbons HDV Heavy Duty Vehicle IUC In Use Compliance masl Meters above sea level NOx Nitrogen Oxides NTE Not To Exceed OCE Off-Cycle Emissions PEMS Portable Emissions Measurement Systems PHEM Passenger car and Heavy duty vehicle Emissions Model PM Particulate Matter SCR Selective Catalytic Reduction TA Type Approval THC Total Hydrocarbons US-NTE US Not To Exceed - US legislation for the regulation of off-cycle

emissions of HDVs WHDC World-wide harmonised Heavy-Duty Certification WHSC World-wide harmonised Heavy-duty Steady state engine test Cycle WHTC World-wide harmonised Heavy-duty Transient engine test Cycle WNTE World-wide harmonised Not To Exceed regulation. In this report ‘WNTE’

always refers to the draft regulation for off-cycle emissions of HDV proposed by the UN/ECE


8 References

[OCE WD10, 2006] Draft GTR (Ver 5) from 4th Meeting of the Editorial Committee Extract_06.OR.PT.047_HJD 6 and 7 April 2006

[OCE WD23, 2005] EU normal operating conditions, ACEA presentation at the 9th OCE meeting (Geneva, 11-12 January 2005, Informal doc. 23, available at www.oica.net)

[Rexeis, 2005] Rexeis M, .Hausberger S, Riemersma I., et.al.: Heavy duty vehicle emissions; Final Report of WP 400 in ARTEMIS (Assessment and Reliability of Transport Emission Models and Inventory Systems); DGTREN Contract 1999-RD.10429; University of Technology, Graz; report no. : I 02/2005/Hb 20/2000 I680; 2005

[Hausberger, 2003] Hausberger S.: Simulation of Real World Vehicle Exhaust Emissions; VKM-THD Mitteilungen; Heft/Volume 82; Verlag der Technischen Universität Graz; ISBN 3-901351-74-4; Graz 2003

[Le Anh, 2005] Le Anh T., Hausberger S., Ajtay D., Weilenmann M..: Response times in instantaneous emission measurement; Final Report of WP 300 in ARTEMIS (Assessment and Reliability of Transport Emission Models and Inventory Systems); DGTREN Contract 1999-RD.10429; University of Technology, Graz; 2005

[Ajtay, 2005] Modal Pollutant Emissions Model of Diesel and Gasoline Engines; A dissertation submitted to the Swiss federal Institute of technology Zurich; Diss. ETH No. 16302; Zurich 2005

[Gautam, 2004] Gautam M. et.al.: Development of a Test Method to Measure Stationary and Portable Engine Emissions; CARB project 00-06, Department of Mechanicakl and Aerospace Engineering, West Virginia University; 2004

[Bach, 2002] Bach H., Weber A. Hausberger S., Rexeis M. et.al.: Optimierungspotentiale in der Entsorgungslogistik, im Auftrag des Bundesministeriums für Verkehr, Innovation und Technologie im Rahmen der Green Logistik Initiative; Wien, Juli 2002

[Soltic, 2004] Soltic P., Rütter J., Graf R., Hausberger S., Ziegler R.: On-Road Measurements, Test Bench Measurements and Emission Simulation for a Tractor-Semitrailer in Trans-Alpine Operation; EMPA Materials Science and Technology; Research report No. 200103; Dübendorf, Nov. 2004

[Steven, 2001] Development of a Worldwide Harmonised Heavy-duty Engine Emissions Test Cycle, Final Report, April 2001, TRANS/WP29/GRPE/2001/2, Informal document No. 2, GRPE 42nd session

[Steven, 2005] Comparison of in-use operation conditions with exhaust emission test condition, CEMT/CS/Env (2005)2/rev2

[Booker, 2006] Booker D., Gianelli R. and Hu J.: Road Testing of an On-board Particulate Matter Mass Measurement System, Poster at DEER conference, Detroit, Aug. 2006

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