Talk given when receiving the award for the best exploratory research on behalf of the Institute of Environment and Sustainability.

1. Institute for Environment and Sustainability 1
Joint Research Centre (JRC)
Modelling of diesel-engine exhaust
nanoparticle dynamics
L. Isella, B. Giechaskiel, Y. Drossinos
IES - Institute for Environment and Sustainability
Ispra, Italy
http://ies.jrc.ec.europa.eu
http://www.jrc.ec.europa.eu

2. Motivation and Goals
Institute for Environment and Sustainability
• Diesel-generated nanoparticles raise concerns about their effects on
human health and environment.
• Legislation regulating diesel-vehicle particulate mass emissions
(EURO1,2,3,4,etc. . . ), but particle number distributions may be a
better metric (especially for health effects).
• Evaluate effect of sampling and experimental conditions on
measured particle number distributions emitted from light/heavy duty
vehicles ⇒ PMP.
• Exploratory research as an experimental and theoretical study of the
dynamics of non-volatile (PMP) particles emitted from diesel
light-duty vehicles (emphasis on nanoparticle agglomeration).
• Experiments performed at the Vehicle Emission LAboratories
(VELA) at Ispra.

3. Experimental set-up
Institute for Environment and Sustainability
• Temperature and particle number distribution measurements along
whole experimental manifold (not only at legislated position).

4. Vela Laboratory
Institute for Environment and Sustainability

5. Experimental number distributions
Institute for Environment and Sustainability
6 × 107 1.2 × 108 1.8 × 108 2.4 × 108
inlet
outlet
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lognormal fit
dN dlogdagg [cm−3]
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0
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20 50 100 200 500
dagg [nm]
• Lognormal number distribution (EURO3 vehicle, 120Km/h)
(log dagg − log µ)2
N∞
dN fit = √ exp − d log dagg .
2 log2 σ
2π log σ
• Compact way of representing the data: N∞ , µ and σ unambiguously
describe the experimental data.

6. Aerosol in a Tube
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z = Um τ
Diffusional
ExhaustCarrier Agglomeration losses (vdif)
Flow
Kij
Monomers
Um
R
Thermophoretic
∆T
losses (vth)
• Four different aerosol processes: agglomeration, diffusion,
thermophoresis and convection.
• 1D model neglecting turbulence-induced local particle density
inhomogeneities.
• nq (flux-averaged axial aggregate concentration of size dq [q-mer])
along tube as function of residence time τ
q−mer creation q−mer removal
dnq (τ ) 2(vdif + vth ) 1
=− Kij ni (τ )nj (τ ) −nq (τ ) Kiq ni (τ ) .
nq (τ ) +
dτ R 2
i+j=q i
diffusion and thermophoresis
agglomeration

7. Time-Scales and Approximations
Institute for Environment and Sustainability
103 s, τth
• Time-scales for each process: τagg 2s, τdif 30s and
2s.
τconv
1.4 × 108
Simulation
q
Outlet measurement
q
q
q
Residence time for
1.18 × 108
q
a 6.5m long transfer tube
q
q
N[cm−3]
q
q
q
q
9.6 × 107
q
q
q
q
q
q
Final concentration for a q
q
6.5m long transfer tube (LAT) q
q
q
Final concentration for a
7.4 × 107
9m long transfer tube
(VELA)
0.0 0.5 1.0 1.5 2.0
τ[s]
• Effect of the transfer tube length on number concentration: important
for experiment reproducibility.
• Transfer tube length should be regulated.
• Different τagg ∝ 1/N∞ (0) for a light-duty Euro4-5 diesel engine.

8. Langevin Equation
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m1
Random kicks from air molecules
Brownian motion and nanoparticle diffusion (fluctuation) W
Push monomer through air
Friction (dissipation) β1
Interaction force F between monomers
• 3D system of interacting monomers, each obeying
m1¨i = Fi −m1 β1 ri + Wi (t) .
˙
r
force friction noise

9. Aggregate Morphologies
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10. Final Remarks
Institute for Environment and Sustainability
• Exploratory research beneficial to on-site experimental activities
(VELA).
• Strengthening of JRC scientific reputation by addressing topical
issues in diesel-vehicle particulate emissions.
• Recommendation for policy makers ⇒ transfer tube length to be
regulated.
• Debate whether to regulate light/heavy duty emitted diesel particle
number distributions in the future ⇒ timeliness of the exploratory
research.