2. Preliminary results of the OEMs HDV PN-PEMS validation study
B. Giechaskiel
Sci. Lab Manager,
13 Nov 2017, Ispra, Italy

3. Update on HDV PN-PEMS validation program
Introduction
Experimental
Preliminary results
Next steps
Note: preliminary results as testing is on-going

4. Introduction PN-PEMS Call of interest (22 Oct 2015)
PN-PEMS Technical specifications (based on LDV) (Nov 2015)
JRC main evaluation (Feb – June 2016)
JRC second evaluation (Sept. 2016) / pre-validation
JRC report EUR EN
JRC recommendations and wishlist (Dec 2016)
OEMs validation program (Feb 2017+)

5. Introduction (JRC wishlist)
Lab testing
At least PMP (+10nm desirable) and one PEMS
EFM desirable (to compare vs fuel+air)
On-road testing
At least 2 PEMS on-road
Additional tests
CNG vehicles
High percentage biofuels
Cracked DPF that the emissions are just above the limit

6. OEMs validation exercise
First discussions end of Oct 2016
Final discussions mid Feb 2017
Tests started end Feb 2017
Tests finished end of September
Telco 14 Nov status update
Extra tests in November (two OEMs)

7. Objectives Results of Golden instruments vs PMP lab
to each other (lab, on-road)
Results of rest PN-PEMS
vs Golden PEMS (lab, on-road)
Results of (valid) on-road tests if only one PEMS (for conformity factors).
Database and final analysis (JRC)
Open point: EMROAD

8. PN emissions

9. OEM
period
PEMS#2
PEMS#3
PEMS#1
PEMS#4
Comments
OEM1
Feb-Mar
Y1, Y2
DPF, CNG, lab & on-road
OEM2
April Y2 Y1
OEM3
July -
DPF on road
OEM4
issues
CNG on road
OEM5
September Y3
CNG lab & on-road
JRC
Y3 proto
CNG lab
CPC DC DC
CPC

10. Example experimental set-up
From the draft Guide PN- PEMS. Typical setup
Due to short heated lines of PN-PEMS it was decided to add an additional 4m sampling line (heated at 120oC)
Additional residence time +3 sec

11. Golden instrument(s) PN-PEMS #2 (CPC) PN-PEMS #3 (DC)
Additional sampling (heated) line and splitter to the two instruments

12. PN-PEMS principles of operation
Diffusion Charger
or catalytic stripper
Condensation
Particle
Counter
Particle size has an effect on the signal
wick
PMP system (reference) from 23 nm

13. Technical requirements for PN-PEMS
Theoretical differences to PMP

14. Initial PN-PEMS theoretical uncertainty
A 50% difference to “Reference” PMP is expected
Two PEMS close to each other should be within 60% assuming similar particle losses

15. Effect of extra heated line
Additional sampling line resulted in 25-30% lower concentrations probably due to diffusion and thermophoretic losses
Dilution close to the tailpipe is recommended
Directly at tailpipe
With heated line

16. Effect of heated line Results confirmed at a second OEM:
PN-PEMS #2
Results confirmed at a second OEM:
The sampling line introduced 25-30% particle losses
NO correction was applied at the results
Texh: 400100oC25%

17. EFM uncertainty
For a few cases (3 labs) test bed data were available (fuel+air)
The mean difference to the EFM was better than 3% in all cases

18. Sub-23nm particles (CNG) at JRC
Testing at JRC with PMP systems having evaporation tube (ET) or catalytic stripper (CS)
High sub-23nm fraction
No evident artifact with ET

19. Tests at JRC
The PEMS systems at the tailpipe were within 16% of the CS system or 29% of the PMP.
No indications of artifacts for any of the PEMS systems (both with CS)

20. PN-PEMS #2 (validation)
The first unit had issues during first engine lab testing (CPC measuring 0 after a point)
The second unit showed very good results within 30%
Better setup could have resulted in better agreement

21. PN-PEMS #2 (validation)
Lab soot (propane diffusion flame) showed similar results: Differences within 30%
However concerns were raised for CPC wick drift (needs confirmation)
Nevertheless, there was an alarm from the instrument (pulse height)

22. PN-PEMS #3 (validation)
Both units had issues (ET) during on-road tests
Nevertheless with a PMP efficiency the results were close to the PMP reference
The second unit showed very good results within 50%, overestimating

23. PN-PEMS #1 & #4 Limited data:
PN-PEMS #1 overestimating around 50% (1 lab)
PN-PEMS #4 underestimating around 20% (1 lab)

24. PEMS #3 vs PEMS #2 (lab) Lab data Differences -50% to +50%
Mean difference 5% at levels >1x10^11 p/kWh
Higher relative differences at levels <1x10^11 p/kWh

25. PEMS #3 vs PEMS #2 (on-road)
On-road data (with lab)
Mean on-road differences around +50% at levels >1x10^11 p/kWh
Partly due to PN-PEMS #2 underestimation
PEMS #3 seems to overestimate emissions

26. PEMS #1 vs PEMS #2 Lab and on-road:
Differences around 50% at the critical range >3x10^11 p/kWh
Higher difference at lower concentrations
Partly due to underestimation of PEMS #3
Generally PEMS #1 overestimating

27. Real time signals (CNG, lab)
Level: 8.5x10^11 p/kWh, differences <15%

28. Real time signal (ED95, lab)
Level: 6x10^10 p/kWh, differences +25% and +85%

29. Real time signal (DPF, on-road)
Cold start 2x10^11 p/kWh, difference <20%

30. Real time signals (DPF, lab)
Emission level: 3x10^11 p/kWh
High background of PEMS with diffusion chargers

31. Real time signals (DPF, lab)
Emission level: 6x10^11 p/kWh, +/-30%

32. Emission levels (DPF) Lab tests WHTC
Overall: 14% cold WHTC and 86% hot WHTC
On-road tests
Integrated emissions (no EMROAD)
Cold: First 1200s
Overall: 14% cold and 86% average urban, rural, motorway

33. Emission levels (CNG) Lab tests WHTC
Overall: 14% cold WHTC and 86% hot WHTC
On-road tests
Integrated emissions (no EMROAD)
Cold: First 1200s
Overall: 14% cold and 86% average urban, rural, motorway

34. Overview
The HDV PN-PEMS OEMs validation phase took place from February until October 2017 (tbc)
5 OEMs participated until end of October 2017 (tbc)
8 DPF, 5 CNG engines/vehicles
1 golden PN-PEMS was circulated (second had issues)
PN-PEMS from 4 instrument manufacturers were tested (8 units)
Tests included comparisons of PN-PEMS with PMP systems in the lab and with PN-PEMS on the road

35. Preliminary conclusions
PMP robustness
The PMP procedure (evaporation tube and 23 nm CPC, dilution 100x10) gave similar results with a system with catalytic stripper for a CNG vehicle.
The sub-23 nm fraction was similar between evaporation tube and catalytic stripper indicating no artifacts.
The results confirm previous JRC findings
This campaign confirmed that there might be many cases where the sub-23 nm fraction is high and consequently the cut-off curve of the PEMS system is important

36. Preliminary conclusions
Sources of uncertainty for PN-PEMS
Exhaust flow rate from EFM <3%
Additional sampling line to the golden instruments introduced 30% losses that were not corrected (and wouldn’t happen in commercial systems)
Sub-23 nm particles seem to influence more diffusion chargers
Initial issues of the Golden instruments probably affected the initial results

37. Preliminary conclusions
Laboratory tests (vs PMP reference)
The golden instrument (CPC based) was within 30% with engine or soot generator aerosol for a wide range of emission levels
The second golden instrument (DC based) was within -50% and +50% for emission levels >1x10^11 p/kWh
A limited number of tests with other PN-PEMS showed similar behavior: a CPC based PEMS was within 30%, a DC based within 50%
Second by second comparisons showed excellent agreement with the reference of CPC based PEMS
DC based PEMS sometimes show higher spikes and higher background levels

38. Preliminary conclusions
On-road tests
The on-road tests didn’t reveal any additional issues not previously seen in the laboratory
The relative differences of PEMS were similar on the road as in the lab
The relative differences between PEMS were slightly higher than expected
The reason was that one system was overestimating the emissions and the others underestimating

39. Next steps
Clarification how OEMs and vehicles will appear. Is the amount of info regarding engines enough (no category N3 etc or engine capacity)?
Further confirmation of received data and calculations and how they will be included in the report (i.e. short summary report with results to be sent to each OEM)
Update with future additional tests
Draft report early 2018?

40. Any questions?
You can find me