AVL TechDay 2013
JRC, Ispra
PN to PM Correlation
Michael Arndt, AVL-List GmbH, Graz
OUTLINE
Overview about particle formation, losses and dynamics
Relation between PM and PN: How do they fit together?
PM and soot mass vs. PN – Discussion of examples
Conclusions
PARTICLE LOSSES AND DYNAMICS
EFFECT OF AGGLOMERATION
Effect of agglomeration on particle number concentration (K=10-15 m3/s).
•
•
•
Concentration remains almost constant at low initial concentrations (<10^7 p/cm3)
A concentration of 10^8 p/cm3 for 50 nm particles decreases by ~23% in 3 s, and the particle diameter
increases by ~4.6 nm.
Agglomeration is not important for post-DPF applications
PM & PN FORMATION AND DYNAMICS
SAMPLING POSITION EFFECT ON PN AND SIZE
DISTRIBUTION
PM
3
Full dilution tunnel
Dilution air
conditioning
2
1.
2.5E+08
2.
Tailpipe
End
anaconda
-3
Heater
dN/dlogDp [cm ]
2.0E+08
3.
Sampling
1.5E+08
3
CVS 12m /min
1.0E+08
3
CVS 6 m /min
5.0E+07
120 kmh
Vehicle
exhaust
gas
0.0E+00
10
100
1000
Mobility Diameter [nm]
1
Measurements with a hot FPS (Dekati) + SMPS (TSI)
Isella et al. 2008, JAS, 39, 737
CORRELATION BETWEEN PN AND TOTOAL PM
No correlation
Grey solid symbols are data from the PMP light duty interlaboratory exercise with the light duty golden instrument
(Rotating disk type from Matter Eng.). Colored open symbols
are data with APCs at various laboratories. Each point is a
different vehicle or a different fuel (exception for D (DPF) PMP,
which is the golden vehicle, all labs results are given).
D=Diesel, DPF=Diesel Particulate Filter, MPI=Multi Point
Injection, G-DI=Gasoline Direct Injection, LPG=Liquefied
Petroleum Gas.
No correlation
Comparison of the PN with the regulated PM emissions for
different heavy duty engine technologies. Grey solid
symbols are data from the PMP heavy duty inter-laboratory
exercise with the heavy duty Golden instrument (SPCS
prototype). Colored open symbols are measurements with
APCs at JRC and AVL. Each point is a different engine or
test cycle. DOC=Diesel Oxidation Catalyst, DPF=Diesel
Particulate Filter, SCR=Selective Catalytic Reduction for
NOx.
Giechaskiel et al. 2010, MST, in press.
CORRELATION BETWEEN PN AND TOTOAL PM
•
•
Correlation is given for quite high PM values.
At high PM usually a quite high non-volatile fraction (soot) is found. increases by ~4.6 nm.
CORRELATION BETWEEN PN AND BC
BC measurement correlates quite well to PN (PMP), because in many cases soot is the main
contributor to PN after removing volatiles in the VPR
SOOT MASS (MSS) VS. PARTICLE NUMBER (APC)
@ GDI SINGLE CYLINDER RESEARCH ENGINE
5000000
4500000
8.0E+07
20
4000000
3500000
2500000
415S soot conc mg/m3
MSS soot conc mg/m3
APC #/cm3
16
7.0E+07
6.0E+07
2000000
14
1000 rpm
2000 rpm
1000000
12
4000 rpm
Higher load at the same speed
Higher speed
slightly bigger particles
5.0E+07
smaller particles
500000
0
10
4.0E+07
0
10
20
30
8
40
50
60
70
80
90
100
Alpha [%]
3.0E+07
6
2.0E+07
4
1.0E+07
2
0
0
500
1000
1500
2000
2500
t [s]
Raw exhaust sampling on a „dirty“ GDI engine
3000
3500
4000
4500
0.0E+00
5000
PNC [#/cm3]
1500000
soot [mg/m3]
APC:MSS
18
3000000
MICRO SOOT SENSOR VS. PARTICLE COUNTER
MICRO SOOT SENSOR VS. PARTICLE COUNTER
MICRO SOOT SENSOR VS. PARTICLE COUNTER
MICRO SOOT SENSOR VS. PARTICLE COUNTER
10
Soot mass [mg//km]
1
0.1
Detection Limit of 483
0.01
0.001
1.0E+08
1.0E+09
1.0E+10
1.0E+11
1.0E+12
1.0E+13
Particle number [#/km]
Comparison between soot mass and particle number on NEDC
1.0E+14
CONCLUSIONS
There is an obvious relationship between PN and PM
There seems to be an even better correlation between soot and PN (PMP)
When the MSS is sampling from the tailpipe with dilution ratios between 2
and 5, it is sensitive enough to measure the soot mass when PN is at the
certification limit
When the MSS doesn‘t see any soot at all, the engine will quote likely not fail
certification according to PMP
For transient cycles the PN can be roughly calculated from soot mass
concentration, the available data suggest a conversion factor of
~3x10^12p/mg
CONCLUSIONS
But...
PM to PN correlation is only stable when agglomeration rate is low. As a
consequence particle counting on raw exhaust only makes sense for small
PN concetration
Semi-volatile particles, which are not removed completely by a VPR, will
make any PM-PN correlation difficult
Alternative fuels may lead to different correlations due to the chemical nature
of particles as well as different size distributions
Aftertreatment devices like SCR will also influence the correlation
SOME FINAL WORDS
If all different measurment technologies
for particles would correlate, we would
need only one instrument...
... which would be bad for instrument
manufcturers like AVL!
AVL TechDay 2013
JRC, Ispra