US-EPA_NEDC_comparison

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US-EPA_NEDC_comparison Powered By Docstoc
					Comparison of the fuel consumption measured over EU
and US legislated cycles

Zissis Samaras, Savas Geivanidis
Laboratory of Applied Thermodynamics, Aristotle University of Thessaloniki

PO Box 458, GR - 541 24, Thessaloniki, Greece
Tel: (+30) 2310 996014, Fax: (+30) 2310 996019, Web: http://lat.eng.auth.gr




Preface
This study was initiated by an email sent by Mr. Karl-Heinz Zierock requesting comments on
a presentation given by Feng An and Amanda Sauer at the IEA/UNEP Workshop on
Automobile CO2 Reduction and Fuel Economy Improvement Policies. Subject of this
presentation was the Comparison of Automotive Fuel Efficiency and GHG Emission
Standards around the world. Conversion factors to CAFE-equivalent MPG and EU-equivalent
CO2 emission rate of g/km were provided in slide 14 of this presentation. In the following
paper these values were compared against real measurement data on driving cycles derived
from a draft version of the ARTEMIS database [1] as well as simulated cycle data from the
vehicle model ADVISOR [2].
Measurement data source
As already mentioned, the ARTEMIS measurement data were used for the comparison. The
ARTEMIS database consists of data gathered during the homonymous project [1] as well as
the OSCAR [3] and the PARTICULATES [4] research project. In addition to these it includes
data from the older MEET project [5]. It should be noted that this database was accessed in its
draft version which was close though to finalization.

Database processing
The ARTEMIS database included measurement data of certain vehicles under all cycles of
interest (UDC, EUDC, US FTP-1, US FTP-2, US FTP-3 and US Highway). In case more than
one measurement on a specific cycle was available, the average was calculated in order to
reduce measurement scatter and obtain comparative results. Using the data of the above
subcycles, the CO2 emissions of the main cycles were estimated as follows [6]:




                                             4059 UDC[g/km] 6955 EUDC[g/km]
                              NEDC[ g / km] 
                                                        4059  6955

                        140
                                             UDC                        EUDC
                                            0-780 s                   780-1180 s
                        120

                        100
          speed, km/h




                        80

                        60

                        40

                        20

                         0
                              0      200     400        600     800      1000      1200
                                                      time, s

                                               Figure 1: NEDC
                   0.43             1 FTP2[g/km] 
                         FTP1[g/km]              0.57 FTP3[g/km]
US _ FTP[ g / km] 
                                      0.43   .57
                                            1 0




                   Figure 2: US FTP driving cycle




                     0.43 FTP1[g/km]  .57 
                                        0    FTP2[g/km]
          US _ City 
                                  0.43  .57
                                        0




                   Figure 3: US City driving cycle
                            Figure 4: US Highway driving cycle




                             0.55 US_City[g/km]  .45 
                                                  0      US_highway[g/km]
              CAFE[ g / km] 
                                              0.55  .45
                                                    0




Vehicle simulation
Two vehicle models were used in ADVISOR for the simulation of the driving cycles. The
gasoline vehicle was a Saturn 1.9 while the diesel vehicle was a VW Golf TDi 1.9 l. All
subcycles were simulated separately and combined according to the above presented
equations to provide the final cycle results. Start conditions (cold-hot) were chosen according
to the legislation.
Results and discussion
The correlations between the EU and US legislated cycles as they came up from the
ARTEMIS database processing are being presented in Figure 5 to Figure 8:




    CO2 correlation between NEDC and FTP (Gasoline vehicles)                   CO2 correlation between NEDC and FTP (Gasoline vehicles)

                          350                                                                          600
                                    y = 0.99x + 3.17
                          300            2                                                             500
                                        R = 0.91




                                                                               CO2 over FTP [g/mile]
    CO2 over FTP [g/km]




                          250
                                                                                                       400
                          200
                                                                                                       300
                          150
                                                                                                                                     y = 1.59x + 5.09
                                                                                                       200                                2
                          100                                                                                                            R = 0.91

                           50                                                                          100

                            0                                                                            0
                                0   50   100    150    200   250   300   350                                 0   100    200    300    400     500       600
                                          CO2 over NEDC [g/km]                                                         CO2 over NEDC [g/km]


                            Figure 5: Correlation of CO2 measured over FTP NEDC (gasoline vehicles)




            CO2 correlation between NEDC and FTP (Diesel vehicles)                     CO2 correlation between NEDC and FTP (Diesel vehicles)

                          350                                                                          600
                                    y = 1.01x + 1.84
                          300            2                                                             500
                                       R = 0.96
                                                                               CO2 over FTP [g/mile]
    CO2 over FTP [g/km]




                          250
                                                                                                       400
                          200
                                                                                                       300
                          150
                                                                                                                                     y = 1.63x + 2.96
                                                                                                       200                                2
                          100                                                                                                            R = 0.96

                           50                                                                          100

                            0                                                                            0
                                0   50   100    150    200   250   300   350                                 0   100    200    300    400     500       600
                                          CO2 over NEDC [g/km]                                                         CO2 over NEDC [g/km]


                                Figure 6: Correlation of CO2 measured over FTP NEDC (diesel vehicles)
   CO2 correlation between NEDC and CAFE (Gasoline vehicles)                    CO2 correlation between NEDC and CAFE (Gasoline vehicles)

                           350                                                                            600

                           300                                                                            500




                                                                                 CO2 over CAFE [g/mile]
    CO2 over CAFE [g/km]




                                     y = 0.87x + 4.45
                           250            2
                                         R = 0.89                                                         400
                           200
                                                                                                          300
                           150
                                                                                                                                        y = 1.40x + 7.16
                                                                                                          200                                2
                           100                                                                                                             R = 0.89

                            50                                                                            100

                             0                                                                              0
                                 0   50   100    150    200   250   300   350                                   0   100    200    300    400      500      600
                                           CO2 over NEDC [g/km]                                                           CO2 over NEDC [g/km]


                            Figure 7: Correlation of CO2 measured over CAFE NEDC (gasoline vehicles)




    CO2 correlation between NEDC and CAFE (Diesel vehicles)                       CO2 correlation between NEDC and CAFE (Diesel vehicles)

                           350                                                                            600

                           300                                                                            500
                                                                                 CO2 over CAFE [g/mile]
    CO2 over CAFE [g/km]




                                     y = 0.90x + 4.56
                           250            2
                                        R = 0.98                                                          400
                           200
                                                                                                          300
                           150
                                                                                                                                        y = 1.44x + 7.33
                                                                                                          200                                2
                           100                                                                                                              R = 0.98

                            50                                                                            100

                             0                                                                              0
                                 0   50   100    150    200   250   300   350                                   0   100    200    300    400      500      600
                                           CO2 over NEDC [g/km]                                                           CO2 over NEDC [g/km]


                             Figure 8: Correlation of CO2 measured over CAFE NEDC (diesel vehicles)


A good linear fit was observed in all cases. In particular the comparison of FTP (expressed in
g/km) against the NEDC showed an almost one to one relationship.
The comparison of conversion factors as produced by the ARTEMIS datatabase processing,
the ADVISOR simulation and Feng An et al. is presented in Figure 9 and Figure 10.
                                                        1.05
                           1.2




                                                                                                                   1.04
                                                                                                     1.02
                                        1.00
US EPA cycles/NEDC ratio




                                                                                                                                  0.92


                                                                                                                                                 0.90
                                                                                     0.89
                                                                      0.89
                           0.8



                           0.4



                           0.0
                                                        gasoline                                                     diesel
                                               FTP [g/km]/NEDC [g/km]                          FTP [g/km]/NEDC [g/km]
                                               (meas. data)                                    (ADVISOR)
                                               CAFE [g/km]/NEDC [g/km]                         CAFE [g/km]/NEDC [g/km]
                                               (meas. data)                                    (ADVISOR)

                                       Figure 9: FTP over NEDC ratio (common unit: g/km)




                           2.0
                                                 1.69




                                                                                                            1.68
                                                                                                   1.65
                                      1.62
US EPA cycles/NEDC ratio




                                                                                                                                         1.481

                                                                                                                                                   1.445
                                                                                       1.438
                                                                             1.435
                                                               1.44




                           1.6
                                                                                                                          1.230


                           1.2

                           0.8

                           0.4

                           0.0
                                                        gasoline                                                     diesel
                            FTP [g/mile]/NEDC [g/km]                    FTP [g/mile]/NEDC [g/km]            CAFE [g/mile]/NEDC [g/km]
                            (meas. data)                                (ADVISOR)                           (Feng An et al.)
                            CAFE [g/mile]/NEDC [g/km]                   CAFE [g/mile]/NEDC [g/km]
                            (meas. data)                                (ADVISOR)

                           Figure 10: FTP over NEDC ratio (NEDC in g/km, US EPA cycles in g/mile)
As it can be seen in Figure 10, there is a very good agreement between the three data sources
as regards the gasoline vehicles. On the other hand the CAFE/NEDC ratio proposed by Feng
An et al. is about 17% lower than the one produced by the ARTEMIS database processing.
This difference is being confirmed by the ADVISOR simulation as well. This can be
attributed though to the definition of conversion factors in the ARTEMIS - ADVISOR
estimation. As it can be seen in slide 14 of the presentation, the EU (diesel) conversion factor
is 15% lower than the EU (gasoline) conversion factor, which is confirmed by the rest of the
conversion factors as well. This probably means that the conversion factors have as reference
the gasoline CO2 emissions. If this is the case, CO2 emissions of diesel vehicles are converted
to gasoline-based CO2 emissions under the assumption that the CO2 emissions of diesel
vehicles are 15% lower than the CO2 emissions of gasoline vehicles.
List of figures
Figure 1: NEDC .....................................................................................................................2
Figure 2: US FTP driving cycle ..............................................................................................3
Figure 3: US City driving cycle ..............................................................................................3
Figure 4: US Highway driving cycle ......................................................................................4
Figure 5: Correlation of CO2 measured over FTP NEDC (gasoline vehicles) ..........................5
Figure 6: Correlation of CO2 measured over FTP NEDC (diesel vehicles)..............................5
Figure 7: Correlation of CO2 measured over CAFE NEDC (gasoline vehicles).......................6
Figure 8: Correlation of CO2 measured over CAFE NEDC (diesel vehicles)...........................6
Figure 9: Comparison of FTP over NEDC ratio (common unit: g/km) ....................................7
Figure 10: Comparison of FTP over NEDC ratio (NEDC in g/km, US EPA cycles in g/mile).7



References


1. http://www.trl.co.uk/artemis/
2. http://www.ctts.nrel.gov/analysis/advisor.html
3. http://www.eu-oscar.org/
4. http://vergina.eng.auth.gr/mech/lat/particulates/
5. http://www.inrets.fr/infos/cost319/#Heading3
6. http://www.dieselnet.com/standards/cycles/

				
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