Comparison of soot issued from diesel and naphtha combustion

April 2016

Christophe CHAILLOU – Aramco (France)

Alexandre BOUET – Nicolas RANKOVIC – Aramco (France)

Arnaud FROBERT – Florence DUFFOUR – Loic De Francqueville – IFP Energies nouvelles

CLEERS 2016

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INTRODUCTIONht

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METHODOLOGY RESULTS CONCLUSION

• Criteria pollutants and global CO2 emissions are major issues!

• Globally fuel-engine technologies could substantially reduce CO2 as well as local pollution in the transport sector

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Working together to find the global optimal solution is the key driver to improve overall CO2 and pollutants

Oil Industry

Legislator

Lowering CO2 & pollutants

Car manufacturer

Fuel specifications (sulphur content, PAH, benzene …)

Less processed fuels

Engine & ATS efficiency

Adapting fuel characteristics (Octane, Cetane …) & engine design (fuel injection, combustion system, after-treatment …)

CO2 & pollutants

Define roadmap & objectives

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INTRODUCTION METHODOLOGY RESULTS CONCLUSIONProject Global ObjectiveCo-develop a Compression Ignition engine for light duty vehicle application fed by an “easier-to-manufacture” fuel like Naphtha-based fuel

2013

2014 2016

2017FUEL ENGINE MATCHING DESIGN

CALIBRATIONSingle cylinder

Multi cylinder

Optical diagnosis

3D Simulation

Fuel Design

OPTIMAL ENGINE

After Treatment System (ATS) investigation

2015

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION3 major benefits for using straight run naphtha fuel in a CI engine

Less processed fuel = CO2 gain for Well to tank (refinery)

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION3 major benefits for using straight run naphtha fuel in a CI engine

Less processed fuel = CO2 gain for Well to tank (refinery)

4.5 % theoretical CO2 saving due to higher H/C ratio & LHV = CO2for tank to Wheel (engine)

Potential of Naphtha-like Fuel on an Existing Modern Compression Ignition Engine. Paper 2015-01-1813. Alexandre Bouet, Aramco Research & Innovation France

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION3 major benefits for using straight run naphtha fuel in a CI engine

Less processed fuel = CO2 gain for Well to tank (refinery)

4,5 % theoretical CO2 saving due to higher H/C ratio & LHV = CO2for tank to Wheel (engine)

Due to longer ignition delay, mixing phase is longer and allows to expect

CO2 saving due to less swirl requirement with lower heat losses and air filling improvement

Reduction of NOx & smoke

http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/m9r.html

Soot investigation was performed to lift risks & evaluate naphtha impact on ATS & specially on Diesel Particulate Filter (DPF)

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Risk assessment

Soot oxidation temperature & rates

Define temperature target

Fuel Borne Catalyst (FBC) impact

Soot reactivity during uncontrolled regeneration

Soot + DPF pressure drop characteristics

To estimate loaded soot for

• Diagnosis

• Regeneration management

• Avoid clogged DPF

INTRODUCTION METHODOLOGY RESULTS CONCLUSION

https://fr.wikipedia.org/wiki/Oxyde_de_fer

http://adetuning.co.uk/tag/dpf-removal/

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Bench equipment

PSA DV6D EURO5 1.6l diesel engine

Close coupled DOC + DPF (uncoated, 6’’, 2.5 l)

DPF with upstream, 13 internal and downstream thermocouples (TC)

Gas bench analyser

Pressure drop sensor

Fuel

Diesel + bio content (FAME = 5%)

Straight-run naphtha (Cetane Number = 35)

Fuel Borne Catalyst

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FBC: what is it?

Organo metallic fuel soluble catalyst

Platinum and/or cerium or iron

In-use dosing rates of 4 - 60 ppm

Can reduce engine out particulate emissions

Can reduce soot oxidation temperatures in DPF’s by ~100°C reduction of DOC PGM load & diesel/oil dilution thanks to lower post-injection quantities

FBC used in this study

Type of FBC: soluble iron oxide

Dosing rate: 6 ppm

Vehicle system: injection of few droplets directly in the fuel tank after each refuelling

INTRODUCTION METHODOLOGY RESULTS CONCLUSION

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INTRODUCTION METHODOLOGY RESULTS CONCLUSIONLaboratory equipment

TGA

Thermo gravimetric Analysis

High precision mass measurement (~ 3 mg of soot) during a Temperature Programmed Oxidation (TPO)

Allow to know soot oxidation temperature & CO/CO2emissions

Conditions

Mettler-Toledo Thermo balance DSC-1 coupled with IR spectrometer

Feed gas: ambient air

Gas flow: 25 ml/min

Temperature: increases from 20 to 800°C at 10°C/min

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

TEM

Transmission Electron Microscopy

Allow to characterize soot morphology, particle size & nodules structure

Ana01/Ana02 are the areas of interest

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Temporal evolution analysis of

the regeneration

Example with naphtha w & w/o FBC at 550°C

DPF pressure drop decrease is faster with FBC

CO emissions correlated with soot oxidation kinetic

DPF pressure drop & CO emissions consistent with soot combustion

Solid line = pure naphthaDashed line = naphtha + FBC

Load soot ~ 15 gNaphtha burned soot = 3.8 gNaphtha + FBC burned soot = 14.6 g

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Oxidation rates @ engine test bench

Without FBC

3 different upstream DPF

temperatures: 550, 600 and 650°C

At 550°C, Diesel fuel oxidation

rate around 0.4.10-3 g/g0/s

consistent with literature (M. N.

Ess and al, MTZ, 2015)

Slightly lower oxidation rates

(15%) for naphtha that could be

attributed to the oxygenated

species presents in Diesel fuel (B5)

Without FBC, naphtha slightly lower oxidation rates than Diesel (bio content?)

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

FBC consideration

FBC / soot ratio is function

Dosing rate

Engine out emission

FBC / soot ratio impact

Soot oxidation rates

FBC / soot ratio results

Around 500°C, to compensate a reduction of FBC / soot ratio from 0.3 to 0.2, an increase of 10°C is required

FBC / soot ratio impact oxidation rates

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Oxidation rate @ engine test bench

With FBC

3 different upstream DPF temperatures investigated: 450, 500 and 550°C

Same FBC/soot ratio needs to be considered

Above 500°C, Diesel has a higher soot oxidation rate

Naphtha + FBC demonstrates slightly lower oxidation rates than Diesel + FBC above 500°C

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Oxidation rate @ lab

Without FBC

Consistency for both measurement (mass & CO/CO2)

Maximum oxidation rates at a lower temperature for Diesel compared to naphtha

With FBC

FBC allows to reduce regeneration temperature by ~100°C for the same oxidation rate

Maximum oxidation rates at the same temperature for Diesel and naphtha but with a different FBC/soot ratio: 0.27 for Diesel and 0.35 for naphtha

Lower soot reactivity for naphtha fuel

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Comparison of engine bench and lab measurement

Despite different processes of measurement …

Isothermal Oxidation for engine bench tests

Temperature Programmed Oxidation for lab tests

… results are consistent between both methods

High level of consistency between bench and lab measurement to determine oxidation rate

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Soot Mass Limit (SML) validation

To avoid DPF cracks, maximal thermal gradient reached during an uncontrolled regeneration process for a DPF is checked

To determine soot mass limit in order to respect supplier constraints

TEM

PERA

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(°C

)

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Soot Mass Limit (SML) determination

3 different levels of soot load: 6, 7 &

8 g/l

FBC/soot ratio different between

diesel (0.18) and naphtha (0.3) due to

lower engine out particles emission

Higher temperature peak and higher

internal thermal gradient for naphtha

based soot due to higher FBC/soot

ratio at the same soot loading level

Maximum soot load needs to be lowered for naphtha from 7 g/l 6.25 g/l

… but lower engine out particles emission

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Pressure drop investigation

Pressure drop measurement

allows to estimate soot load

(for DPF automotive

application) and to determine

DPF status (cracked, nominal,

loaded or clogged)

Pressure drop = f (DPF status,

exhaust volume flow rate,

soot load, ash load)

https://www.dieselnet.com/tech/images/dpf/sys/p_monitor.png

https://www.dieselnet.com/tech/images/dpf/sys/p_monitor.png

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Tests

Tests performed with same ash level (< 0.3 g/l)

Diesel test has higher ash level

Results

A slightly higher pressure drop is observed for diesel (this could be considered as the same pressure drop level between both fuel soot)

INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Naphtha & diesel soot have similar pressure drop characteristics

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION• Samples analyzed

Diesel Soot Naphtha Soot Naphtha+FBC soot

Naphtha & diesel soot have similar characteristics (clusters & primary particles size)

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• Comparison between naphtha and GDI (Gasoline Direct Injection) soot

INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Naphtha soot

Primary particles structure

Clusters with nearly constantdiameter of primary particles (6-45 nm)

GDI soot*

Graphitized and amorphous clusters coexist

Diameter very scattered: 10 - 70 nm for graphitized particles 50 – 100 nm for amorphous

particles

Naphtha & GDI soot have different characteristics (amorphous clusters & primary particles size)

* Zinola et al., SIA Paper 2013

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INTRODUCTION METHODOLOGY RESULTS CONCLUSION

Naphtha soot

Sootparticles aggregates

Clusters with nearly constantdiameter of primary particles

GDI soot

Clusters with various sizes of primary particles

Clusters with small primary particles

Clusters with large primary particles

• Comparison between naphtha and GDI soot

Naphtha & GDI soot have different characteristics (absence of large primary particles for naphtha soot)

* Zinola et al., SIA Paper 2013

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Fuel-engine investigations performed with gasoline-like fuel

(naphtha)

DPF risk assessment & soot comparison with a production DPF +

FBC system

Slightly lower soot oxidation rates for naphtha probably due to absence of bio content

Lower soot mass limit for naphtha due to higher FBC/soot ratio

Soot pressure drop is similar for both fuels

Soot structure is similar between diesel and naphtha fuel

Naphtha fuel, in a compression ignition engine, can be used with a production ATS & DPF. Design rules and standards can be kept from Diesel powertrain applications

INTRODUCTION METHODOLOGY RESULTS CONCLUSION

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Acknowledgement for

Arnaud Frobert (IFPEn)Samuel Doreau (IFPEn), Alexandre Bouet (Aramco) and Nicolas Rankovic (Aramco)

Florence Duffour (IFPEn) and Loic De Francqueville (IFPEn)

Comparison of soot issued from diesel and naphtha combustionINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTIONSlide Number 27