LDV Real Driving Emissions: - Evaluation of PEMS data based on the Moving Averaging Window and a composite severity indicator

Transcription

1 LDV Real Driving Emissions: - Evaluation of PEMS data based on the Moving Averaging Window and a composite severity indicator - Principles and tools - 19th of February 2013, Audio/Web meeting Pierre Bonnel, Martin Weiss - European Commission DG - Joint Research Centre (JRC) - IET - Institute for Energy and Transport

2 Contents Steps of the data evaluation Moving averaging window CO2 composite severity indicator Data requirements PEMS Data Evaluation Tool Simplified EMROAD interface Reporting template Outline of future evaluation work

3 Steps of the data analysis Step 1 - Mark the data segments (Cold start, hot, DPF regeneration). Emissions for cold start and DPF regeneration events are calculated separately. Step 2 - Moving averaging window calculations, based on the vehicle CO2 emissions [kg] over the REFERENCE CYCLE, calculating window emissions in [g/km] Step 3 Building the vehicle CO2 characteristic curve and checking the windows CO2 emissions (in g/km) against the acceptable values defining normal driving

4 Step 1 - Marking cold start & DPF Regen Resulting data for MAW analysis Cold Start DPF Regen Vehicle Speed [km/h] MAW ANALYSIS YES [1] / NO [0] DPF REGEN YES / NO COLD START YES / NO

5 Step 2 Moving Averaging Window Moving averaging window calculations, based on the vehicle CO2 emissions [kg] over the REFERENCE CYCLE, calculating window emissions in [g/km] Baseline Reference Cycle: WLTC Investigations shall be carried our for other reference quantities (e.g. time, distance) and/or multiples of the WLTC value

6 Window CO2 Emissions [g/km] -- Vehicle Speed [km/h] Step 2: Moving averaging window calculations Vehicle Speed [km/h] MAW CO2 [g/km] MAW NOx [g/km]

7 CO2 Step 3: Identification of normal driving using MAW CO2 [g/km] Example based on 3 PEMS routes and using the NEDC CO2 values as reference Uphill mountain driving (Severe to very severe!) Urban driving area CO2 centered on ECE15 value Upper and lower CO2 at ±20% Extra-urban driving area CO2 centered on EUDC value Upper and lower CO2 at ±20% Downhill mountain driving 0 (Soft to very soft!) Window Average Speed [km/h]

8 CO2 [g/km] Step 3 - Vehicle CO2 Characteristic Curve Defining normal/severe driving using: - Speed classes, using the vehicle CO2 emissions [g/km] on the WLTC, in each speed class - Vehicle CO2 curve fitting the WLTC phase values - Lower and upper bounds not necessarily at constant distance (only for the illustration). - Lower and upper bounds at ± x1% (normal) and ± x2% (severe) from the curve Low Speed Medium Speed High Speed Upper bound 2 Extra-high Speed Upper bound 1 Vehicle CO2 curve Lower bound 1 Lower bound 2 Average Speed

9 Data Requirements PEMS test data, including the mandatory test parameters (See PEMS testing guidance document Engine torque and speed not needed) Vehicle CO2 emissions over: The entire WLTC (Baseline reference value for MAW) The phases of the WLTC (Vehicle characteristic curve)

10 Data processing tool Simplified EMROAD interface (calculation step 2)

11 Data processing tool Use of standard PEMS data files Data screening must be conducted separately Simplified EMROAD interface to input calculation parameters Output to the standard EMROAD workbook Specific worksheet created to report the RDE-LDV results Calculation in 3-steps 1. PEMS file selection and upload 2. Input calculation settings 3. Calculation and reporting

12 Data processing tool RDE Pass-Fail Results Worksheet - Input Data Reference Quantity = CO2 Reference Value [kg] WHTC Low Speed CO2 [kg] WHTC Medium Speed CO2 [kg] WHTC High Speed CO2 [kg] WHTC Extra High Speed CO2 [kg] Ref. Curve Coefficient 1 Ref. Curve Coefficient 2 Ref. Curve Coefficient 3 Ref. Curve Coefficient 4 Tolerance Normal Driving [% ] Tolerance Severe Driving [% ]

13 Data processing tool RDE Pass-Fail Results Worksheet Main Results (Normal Driving Same Layout for Severe Driving or other MAW categories) NORMAL DRIVING Low Speed Medium Speed High Speed Extra High Speed NORMAL / WEIGHTED Number of Windows % of Total Averaging Windows CO_AVG - CO_MIN - CO_MAX - CO_90% CUMULATIVE PERCENTILE - NOx_AVG NOx_MIN NOx_MAX NOx_90% CUMULATIVE PERCENTILE PN_AVG PN_MIN PN_MAX PN_90% CUMULATIVE PERCENTILE

14 Annexes

15 Composite driving severity indicator? For RCG testing, the driving severity is dictated only by the acceleration characteristics of the cycle (currently through RPA) For PEMS testing, the driving severity is dictated by a series of elements (acceleration, road grade, vehicle payload, head wind, driver, traffic, ) occurring simultaneously or not Difficulty for the PEMS data evaluation: To develop a set of appropriate indicators to define severe windows; To understand which elements contribute to the severity and to what extent.

16 CO2 emissions as driving severity indicator? Simple physics: Fuel consumption and therefore CO2 are influenced by: Speed Acceleration (based on RPA or better) Idling Road grade Vehicle payload High distance-specific CO2 emissions (fuel consumption ) should be a good indicator of severe vehicle use.

17 Data flagging strategy Possible status for the different elements Element Possible status A: Vehicle condition 1: Hot 2: Cold B: After treatment 1. DPF Functional 2. Regenerating C: Driving 1. Normal 2. Severe (*Based on a composite indicator, refer to the following slides) Comments: Cold vehicle (A2) and DPF regeneration (B2) (normally) do not occur simultaneously DPF Regeneration (B2) not always present Hot normal driving (A1 + C1) represents the largest part of a test (time or distance wise)

18 Data segmentation strategy Mark the following test segments and calculate the emissions: Cold vehicle (A2) After-treatment (B2) Using the remaining unmarked data, perform the moving averaging window calculations: for each window, the composite (CO2) severity indicator is calculated to determine whether the windows belong to normal (C1) or severe driving (C2)

19 CO2 [g/km] Vehicle CO2 characteristic Curve: Alternative concept Defining normal driving using: - Speed classes, using the vehicle CO2 emissions type approval, in each speed class - Intervals in each speed class - Lower and upper bounds in for the normal CO2 range in each speed class Very-Low Speed (PEMS only) Low Speed Upper bound MS CO2 for the medium speed range Lower bound MS Medium Speed High Speed Extra-high Speed Average Speed

20 Further remarks (1) Using vehicle specific values for MAW: important to obtain similar levels of averaging Averaging scale shall remain in the order of the averaging scale used for the type approval cycle or cycle phases. Objective setting: The different data categories (cold start, DPF regeneration, normal and severe driving) can be given different NTE limits and/or weighing factors. Link between the high values of the CO2 indicator and the characteristics of the corresponding driving situations to be documented in the further development the procedure

21 Further remarks (2) Requirements for the trip composition will be needed, expressed in % of the different speed classes A sufficient number of windows should be needed in the different speed classes A minimum percentage of windows could be used to define a valid test (i.e. valid route and driving characteristics) An idling indicator seems required to complement the CO2 indicator