Calculation Methods Impact on Real Driving Emissions Particulate Number Emission Evaluation: Moving Average Window in China vs. Raw Mileage Averaged in Europe
2022-01-0694
03/29/2022
- Content
- In the Real Driving Emissions (RDE) tests, Particulate Number (PN) emission is specifically restricted with a limit as product of the Conformity Factor (CF) and WLTC PN limit 6.0E11 #/km. The CF value is defined as 1.5 in the Europe 6d and 2.1 in the China 6b. Besides the tighter CF value in Europe, the calculation methods that are employed to evaluate the RDE PN emission are also different, i.e. Moving Averaged Window (MAW) according to the China 6b and Raw Mileage Averaged (RMA) according to the Europe 6d RDE package 4. In our previous studies, the “MAW” method was found to be less stringent than the “RMA” method generally, because the window-based “MAW” method could under-estimate the high PN emission generated in the cold start [1]. In fact, for the “MAW” method, the cold start emissions are less counted compared to emissions from the middle of the RDE test. Meanwhile, the weight of each window is impacted by CO2 emission. Such natures of the window-based method make it indirect to reveal the actual emitted particles during the RDE test. Since China 6b RDE adopts the “MAW” method the present study provides for a more detailed analysis of RDE emission results based on this method. The “MAW” method will be applied to different driving profiles and operating conditions, which meet the general RDE test requirements, yet result in different overall particle number emissions. Special focus will be directed towards the initial vehicle operation after the cold start, for example the vehicle lift off timing and initial acceleration. The results will show that the calculation methods can greatly impact the RDE PN emission evaluation. Emphasis to details in the test procedure is required to appropriately protect the application and avoid underestimating the RDE emissions under realistic operating scenarios.
- Citation
- Liu, H., Li, C., Tao, T., Liu, Y. et al., "Calculation Methods Impact on Real Driving Emissions Particulate Number Emission Evaluation: Moving Average Window in China vs. Raw Mileage Averaged in Europe," SAE Technical Paper 2022-01-0694, 2022, .