Electrical Mobility Measurements of

Agglomerate Particulate Matter

Jim DunsheeMS Thesis Defense

November 11th, 2015

Slide 2

Historical Perspective: Particle Uncertainty

“…but how many particles are really present under any conditions, and how the number varies, we have at present very little idea.”

- John Aitken, 1888

SOURCES: Aitken, 1888; Wellcome Library; Seinfeld & Pandis, 2006

≥10 microns (µm)visible to the human eye

Slide 3

Particulate Matter (PM)

IMAGE SOURCE: ciese.org

“A complex mixture of extremely small particles and liquid droplets” (US EPA)

PM10 PM2.5

Slide 4

PM & Health

• Class 1 Carcinogen• No evidence of safe exposure level

(World Health Organization, 2013)

IMAGE SOURCE: alencorp.com (Everything You Need to Know About Airborne Particulate Matter)

Slide 5

Particle Size Distribution

Low

← N

umbe

r → H

igh

Small ← Particle Diameter → Large

Slide 6

Diesel PM Size Distribution

IMAGE SOURCE: Kittelson,, 1998

Slide 7

Spark vs. Compression Ignition Engine Emissions

IMAGE SOURCE: dieselnet.com

SI engine with catalyst

Diesel engine (100%)

Rela

tive

Emiss

ions

(%)

Slide 8

Engine Cycles

Gasoline - Otto Cycle• Spark Ignition (SI)• Homogeneous combustion• Burns “rich”

• Air-fuel ratio < stoichiometric

Diesel - Diesel Cycle• Compression Ignition (CI)• Heterogeneous combustion• Burns “lean”

• Air-fuel ratio > stoichiometric

IMAGE SOURCE: Reactive Flow Modeling Laboratory (rfml.kaust.edu.sa)

Slide 9

Diesel PM/NOx TradeoffDiffusion Flame Combustion

Oxidation• Decreases soot (PM)• Increases NOx

SOURCES: Kittelson & Kraft, 2014; Dec, 1997

Slide 10

Diesel PM Formation

IMAGE SOURCES: Khalek, 2006; Twigg & Phillips, 2009

ElementalCarbon (EC)

OrganicCarbon (OC)

Slide 11

PM Formation by Particle Size

IMAGE SOURCE: Guarieiro & Guarieiro, 2015

Re-entrainmentEngine wear

Slide 12

Diesel Properties

Medium petroleum distillates: C8 – C21

Ultra-Low Sulfur Diesel (ULSD):Naturally occurring sulfur (a lubrication agent)reduced to 15ppm = less soot formation

~75% Alkanes ~25%

May result in toxicaromatic emissions

IMAGE SOURCE: criticalfueltech.com

Slide 13

Biodiesel PropertiesFatty Acid Methyl Esters (FAMEs)

Potential to reduce PM:• Oxygen content of molecule (complete combustion/soot oxidation)• Absence of sulfur• Absence of aromatic compounds

(Lapuerta et al., 2007)

IMAGE SOURCE: biofuelsystems.com/biodiesel-chemistry

Slide 14

Biodiesel PM PropertiesChung et al., 2008 (diesel generator):Irregular compact particles with more organic carbon relative to ULSD

SOURCE: Chung et al., 2008

Diesel

Biodiesel

Slide 15

PM MeasurementThe Gravimetric Method

Operational Definition:“mass collected on a filter” under specified conditions(Swanson et al., 2012)

MassVolumeUnits: Mass Concentration (µg/m³) =

Issues: 1) Temporal Resolution

requires time to collect sample2) Measurement Error

low modern vehicle emission rates

Diesel PM Emission Standards

Slide 16SOURCES: (a) Twigg & Phillips, 2009; (b) Vouitsis et al., 2003

(b) US and EU diesel PM emission limits for heavy-duty vehicles from 1992-2010

(a) EU legislated diesel PM emission limits for passenger cars from 1983-2010

Slide 17

Gravimetric Accuracy

SOURCE: Vouitsis et al., 2003; ACEA report 99000524

Note: emission rates and standards for heavy-duty engines

Slide 18

New Method: IPSD (Integrated Particle Size Distribution)

Basic procedure1. Measure particle size

distribution (PSD) by number

2. Assume spherical particles to calculate volume

3. Apply size dependent density values to calculate mass

m = ρVmass = density x volume

Low

← N

umbe

r →Hi

gh

= rV=

43 π r

3

IMAGE SOURCES: vironova.com, rkm.com.au

Method formalized by Liu et al. (2009)

• Light-duty vehicles (gas & diesel)• Empirically based particle effective density values• Good correlation (R² = 0.79) between IPSD and

Gravimetric• Systematic bias (MassIPSD = 0.63 x MassGrav)

Slide 19

Li et al. (2014) : IPSD Study

Slide 20

Problem With PSD Measurements (EEPS)

Discrepancies reported between

Engine Exhaust Particle Sizer (EEPS or FMPS)and Scanning Mobility Particle Sizer (SMPS)for agglomerate particles (e.g., diesel soot)(Kaminski et al., 2013; Quiros et al., 2014; Zimmerman et al., 2014)

Slide 21

SMPS (Scanning Mobility Particle Sizer)

IMAGE SOURCES: Guha et al., 2012; redwoodareahospital.org

Considered the “gold standard” particle sizing/counting system

Slide 22

SMPS: Bipolar Diffusion ChargingRoughly independent of particle morphology

Note: Particle charging efficiency drops dramatically below 20nm for Boltzmann distribution (shown). Fuchs charging theory is better for Dp < ~50nm.

Charge distribution forms over time (Hinds, 1999):

< -3 -3 -2 -1 0 +1 +2 +3 > +30.01 0.007 0.3 99.3 0.30.02 0.104 5.2 89.6 5.20.05 0.411 0.6 19.3 60.2 19.3 0.60.1 0.672 0.3 4.4 24.1 42.6 24.1 4.4 0.30.2 1.00 0.3 2.3 9.6 22.6 30.1 22.6 9.6 2.3 0.30.5 1.64 4.6 6.8 12.1 17.0 19.0 17.0 12.1 6.8 4.61.0 2.34 11.8 8.1 10.7 12.7 13.5 12.7 10.7 8.1 11.82.0 3.33 20.1 7.4 8.5 9.3 9.5 9.3 8.5 7.4 20.15.0 5.28 29.8 5.4 5.8 6.0 6.0 6.0 5.8 5.4 29.8

10.0 7.47 35.4 4.0 4.2 4.2 4.3 4.2 4.2 4.0 35.4

Percentage of particles carrying theindicated number of charges

Dp

(µm)

AverageNo. of

Charges

IMAGE SOURCE: palas.de/en/product/kr8557

Slide 23

EEPS (Engine Exhaust/Fast Mobility Particle Sizer)

Unipolar charger:

SOURCES: Krinke & Zerrath, 2011; TSI, 2015

Slide 24

EEPS: Unipolar Diffusion Charging

Default calibration underestimatescharge for agglomerates

IMAGE SOURCE: TSI, 2015

TSI Solution:New, empirically based, EEPS data inversion matrices

Problem:EEPS unipolar charge distributioncalibrated for spheres (emery oil)

turbocharged, 4 cylinder, 4.5L, 75kW, Tier 3 diesel engine fueled with BP6 diesel fuel with a sulfur content of 6ppm

Slide 25

New EEPS Matrix Development by TSI

SOURCE: TSI, 2015

Slide 26

New EEPS Matrices: Soot & Compact

Instrument matrix calibrated for soot Comparison of current matrices at 420nm and 42nm electrometer columns

Slide 27

Soot Matrix Results: Heavy-duty Engine

IMAGE SOURCE: TSI, 2015

Low Load:

High Load:

Number Volume

Slide 28

Soot Matrix Results: Light-duty Engine

IMAGE SOURCE: TSI, 2015

GM A20DTH 2.0L light duty turbo charged diesel engine

Slide 29

GMD Agreement with Soot Matrix

No longer underestimates largeragglomerate particles (Dp > ~100nm)

IMAGE SOURCE: TSI, 2015

1) How accurate are new EEPS matrices for various vehicle exhaust particles?a) Biodiesel - unique morphology/chemical composition?b) Transient drive-cycle

2) Do new EEPS matrices improve mass estimates with IPSD method?a) IPSD vs. Gravimetricb) Transient events (e.g., cold-start)

Slide 30

Research Questions?

Slide 31

Current Study

Experiments/Dataset 1: EEPS Evaluation

Experiments/Dataset 2: Cold-start EmissionsEEPS measurements for first 30sec of engine

start at10, 15, and 25°C (nominally)

Slide 32

Data Collection Sequence

Event Setting Duration

Instrument Blank (preIB) Instrument on HEPA filter ≥10minTunnel Blank (preTB) Dilution System On ≥10minEngine Idle Engine On 7.5minEngine Warm-up 3300rpm, 40 or 60% Throttle 7.5minTest Cycle Various ~90minEngine Cool-down (Idle) Engine On 7.5minTunnel Blank (postTB) Dilution System On ≥10minInstrument Blank (postIB) Instrument on HEPA filter ≥10min

Test Cycles1) Steady State (75% engine load)2) Transient (60min) + 3x10min Steady State Phases

- Depicted in Slide 37

Slide 33

Experimental Setup

Engine exhaust

Dry, filtered air

Key:

DifferentialPressure Gage

Temp. ControlSetpoint (°C)

2 stagediluter

Diluted SampleDilution Ratio ~80:1

Engine drive cycle and dilution system developed by by Tyler Feralio (image credit)

Engine:Volkswagen 1.9L SDi (similar to Euro II LDD)• 4 Cylinders• No aftertreatment devices

Slide 34

Fuel Properties

SOURCE: GC-MS analysis conducted by John Kasumba

ULSD (0.81g/cm³) Soybean Biodiesel (0.86g/cm³)

Slide 35

Density Distribution

Slide 36

Quality Assurance: SMPS & Filters

SMPS (units: #/cm³)

90min Filter Blanks (Tunnel)N 5

Avg 4 µg/m³StDev 2.4

Minimum value from tests:35.5 µg/m³

Reported as: MEAN [95% One-sided Upper Confidence Limit]

Slide 37

QA: EEPS Dataset 1 – Box Plots

Slide 38

QA: EEPS Dataset 1 – Detection Limit

EEPS pre-test instrument blank data

Slide 39

ULSD Steady State PSDsLog-log plot Semi-log plot

Slide 40

ULSD Modal Fit Parameters

Slide 41

Xue et al. (2015): Generator on ULSD

SOURCE: Xue et al., 2015

Slide 42

ULSD PM Mass Data

Slide 43

Soot vs. Default: Transient Cycle w/ ULSD

Slide 44

ULSD Transient Phase: Fractional Contributions

Slide 45

ULSD Steady State: Fractional Contributions

Slide 46

Betha & Balasubramanian (2011): ULSD Particle Fractionation

Idle 30% 70% 100%Engine Load (%)

100%

80%

60%

40%

20%

0%

Parti

cle

Num

ber F

racti

on (%

)

Nanoparticles(>50nm)Ultrafine(50-100nm)Fine(>100nm)

FMPS data (i.e., Default EEPS matrix) for diesel generator exhaust

SOURCE: Betha & Balasubramanian, 2011

Slide 47

Biodiesel Steady State PSDsLog-log plot Semi-log plot

Slide 48

Biodiesel Modal Fit Parameters

Slide 49

Xue et al. (2015): Generator on Biodiesel

SOURCE: Xue et al., 2015

Slide 50

Biodiesel PM TrendGravimetric PM data by biodiesel blend for the light-duty diesel engine from this study (dashed line & blue data points)

General trend reported by EPA (2002) - solid line and black data points

Giakoumis et al. (2012)

Majority of data for EPA (2002) & Giakoumis et al. (2012) for heavy-duty diesel engines

Bielaczyc et al. (2009)data for a LDD engine

Slide 51

Biodiesel PM Mass Data

Slide 52

EEPS Report CardKeySP: Satisfactory ProgressUP: Unsatisfactory Progress

IMAGE SOURCE: diplomabuy.com

Slide 53

QA: EEPS Dataset 2 – Box Plots

Slide 54

QA: EEPS Dataset 2 – Detection Limit

EEPS pre-test instrument blank data

Slide 55

ULSD Cold-start Emissions

Slide 56

Cold-start: Fractional Contributions

Slide 57

Sakunthalai et al. (2014): ULSD Cold-starts

Cambustion Differential Mobility Spectrometer (DMS500) data for LDD engine exhaust

SOURCE: Sakunthalai et al., 2014

• EEPS Soot Matrix• Good agreement for ULSD (SMPS and Filter)• Applied to cold-start emissions

• Biodiesel Exhaust Particles• Not characterized well by EEPS

• Poor agreement with SMPS and Filter

Slide 58

Conclusions

• Biodiesel exhaust particle effective density

• Additional EEPS matrices• Or user calibration

• EEPS evaluation for biodiesel blends

• EC/OC analysis by engine load• Compared to particle size fractionation trend

Slide 59

Future Work

UVM Transportation Air Quality LabBritt HolménTyler Feralio

John KasumbaKaren Sentoff

Yao Tan

Acknowledgements

Thank You

Questions & Answers

Betha, Raghu, and Rajasekhar Balasubramanian. "Particulate emissions from a stationary engine fueled with ultra-low-sulfur diesel and waste-cooking-oil-derived biodiesel." Journal of the Air & Waste Management Association 61.10 (2011): 1063-1069.

Bielaczyc, Piotr, and Andrzej Szczotka. A study of RME-based biodiesel blend influence on performance, reliability and emissions from modern light-duty diesel engines. No. 2008-01-1398. SAE Technical Paper, 2008.

Chung, A., A. A. Lall, and S. E. Paulson. "Particulate emissions by a small non-road diesel engine: Biodiesel and diesel characterization and mass measurements using the extended idealized aggregates theory." Atmospheric Environment 42.9 (2008): 2129-2140.

Dec, John E. A conceptual model of di diesel combustion based on laser-sheet imaging*. No. 970873. SAE technical paper, 1997.

EPA, “A comprehensive analysis of biodiesel impacts on exhaust emissions (EPA420-P-02-001)." United States Environmental Protection Agency (2002).

Giakoumis, Evangelos G., et al. "Exhaust emissions of diesel engines operating under transient conditions with biodiesel fuel blends." Progress in Energy and Combustion Science 38.5 (2012): 691-715.

Guarieiro, Lílian Lefol Nani and Aline Lefol Nani Guarieiro (2015). Impact of the Biofuels Burning on Particle Emissions from the Vehicular Exhaust, Biofuels - Status and Perspective, Prof. Krzysztof Biernat (Ed.), ISBN: 978-953-51-2177-0, InTech, DOI: 10.5772/60110.

Guha, Suvajyoti, et al. "Electrospray–differential mobility analysis of bionanoparticles." Trends in biotechnology 30.5 (2012): 291-300.

Hinds WC. Aerosol Technology: Properties, Behavior, and Measurement of Airborne Particles, 2nd edn. John Wiley & Sons, Inc, New York, 1999.

Holmén, B. A.; Feralio, T.; Dunshee, J.; Sentoff, K. Tailpipe Emissions and Engine Performance of a Light-Duty Diesel Engine Operating on Petro- and Bio-diesel Fuel Blends. 2014.

Kaminski H, Kuhlbusch TAJ, Rath S, Götz U, Sprenger M, Wels D, Polloczek J, Bachmann V, Dziurowitz N, Kiesling HJ, et al. Comparability of mobility particle sizers and diffusion chargers. Journal of Aerosol Science. 2013;57:156-178

Khalek, Imad A. "The particulars of diesel particle emissions." Technology Today 27.1 (2006): 2-5.

Kittelson DB. “Engines and nanoparticles: a review.” J. Aerosol Sci.1998; 29: 575–88.

Kittelson, David, and Markus KRAFT. "Particle Formation and Models in Internal Combustion Engines." United Kingdom: University of Cambridge (2014).

Slide 62

References (1 of 2)

Krinke, Thomas and Axel Zerrath. “EEPS/FMPS: From Raw Data to Size Distribution.” Presentation (Sep. 2011).

Lapuerta, Magin, Octavio Armas, and Jose Rodriguez-Fernandez. "Effect of biodiesel fuels on diesel engine emissions." Progress in energy and combustion science 34.2 (2008): 198-223.

Li, Yang, et al. Determination of Suspended Exhaust PM Mass for Light-Duty Vehicles. No. 2014-01-1594. SAE Technical Paper, 2014.

Liu, Z. Gerald, et al. "Comparison of strategies for the measurement of mass emissions from diesel engines emitting ultra-low levels of particulate matter." Aerosol Science and Technology 43.11 (2009): 1142-1152.

Park, Kihong, et al. "Relationship between particle mass and mobility for diesel exhaust particles." Environmental science & technology 37.3 (2003): 577-583.

Quiros, David C., et al. "Particle effective density and mass during steady-state operation of GDI, PFI, and diesel passenger cars." Journal of Aerosol Science (2014).

Sakunthalai, Ramadhas Arumugam, et al. Impact of Cold Ambient Conditions on Cold Start and Idle Emissions from Diesel Engines. No. 2014-01-2715. SAE Technical Paper, 2014.

Seinfeld J. H. and Pandis S. N. (1998) Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, 1st edition, J. Wiley, New York.

TSI (2015). Updated inversion matrices for engine exhaust particle sizer (EEPS) spectrometer model 3090.

Twigg, Martyn V., and Paul R. Phillips. "Cleaning the air we breathe-Controlling diesel particulate emissions from passenger cars." Platinum Metals Review53.1 (2009): 27-34.

Vouitsis, Elias, Leonidas Ntziachristos, and Zissis Samaras. "Particulate matter mass measurements for low emitting diesel powered vehicles: what's next?." Progress in Energy and Combustion Science 29.6 (2003): 635-672.

Xue, Jian, et al. "Comparison of vehicle exhaust particle size distributions measured by SMPS and EEPS during steady-state conditions." Aerosol Science and Technology 49.10 (2015): 984-996.

Zimmerman, Naomi, et al. "Comparison of three nanoparticle sizing instruments: The influence of particle morphology." Atmospheric Environment86 (2014): 140-147.

Slide 63

References (2 of 2)