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PM Emissions Reductions with Alternative Fuels

Prem Lobo

Sustainable Aviation Fuels Forum – FORUM-AE WorkshopMadrid, Spain

21 October 2014

Motivation• Growth in commercial air traffic, rising costs of fuel, an increasing desire to

enhance the security of energy supply and potential environmental benefitsenhance the security of energy supply, and potential environmental benefits have driven feasibility and viability assessment studies of alternative renewable fuels for commercial aviation applications.

Brent Crude Oil Spot Prices 1990 – 2040 (2012 $/barrel)

Source: Boeing Current Market Outlook 2013-2033

Source: US EIA Annual Energy Outlook 2014

Aircraft Engine PM Emissions

Source: Whitefield, P.D. et al., 2008, ACRP Report 9, Transportation Research Board, Washington, D.C.

• PM emissions from aircraft engines are typically presented as the number or mass of PM per kg of fuel burned, or number- and mass-based emission indicesp g ,

– EIn: number-based emission index (#/kg fuel burned)– EIm: mass-based emission index (mg/kg fuel burned)

Alternative Fuels for Aviation• Synthesis from coal (CTL), natural gas (GTL), and biomass

(BTL) via the Fischer Tropsch (F T) process(BTL) via the Fischer-Tropsch (F-T) process• Transesterification of triglycerides to yield fatty acid methyl

esters (FAME)• Hydroprocessing of biomass oils to yield Hydoprocessed

Esters and Fatty Acid (HEFA) fuels • These fuels have very low (negligible) fuel aromatic and• These fuels have very low (negligible) fuel aromatic and

sulfur content

• Specifications for aviation turbine fuels are established by ASTM and the UK MOD– September 2009: ASTM D7566 (Standard Specification for AviationSeptember 2009: ASTM D7566 (Standard Specification for Aviation

Turbine Fuel Containing Synthesized Hydrocarbons)– July 2011: ASTM D7566 allows up to a 50/50 blend of biomass

based components with conventional jet fuelbased components with conventional jet fuel– June 2014: ASTM D7566 allows up to a 10% blend of renewable

Synthesized Iso-Paraffinic (SIP) fuel with conventional jet fuel

Alternative Fuels for Aviation

• Commercial flights with alternative fuels g

– A number of trial demonstration flights with differentA number of trial demonstration flights with different airlines using various blend ratios of alternative fuels from different sources and conventional jet fuel

– Lufthansa’s burnFAIR program (2011)• A321 flew Hamburg Frankfurt sector with 50:50 mix of biofuel• A321 flew Hamburg-Frankfurt sector with 50:50 mix of biofuel

and conventional jet fuel• 1200 flights over a six month period

– KLM’s JFK Green lane program (2013)• B777-200 flew Amsterdam – JFK – Amsterdam sector on• B777-200 flew Amsterdam – JFK – Amsterdam sector on

biofuel mix (UCO and Camelina oil) and conventional jet fuel

Sampling protocol

• Extractive sampling was performed– Exit plane (within 1m downstream)

CFM56‐2C1

p ( )– Near field (10-30m downstream)– Far field (145m downstream)

• PM sample was diluted by a factor of 10 at the probe tip with dry N2

• Sample transferred to instruments ~25m away– Sample lines were not heated

Engine Exit Plane - nvPM Size DistributionsCFM56‐7BNov 2007i iliGE Engine Test Facility

PM size distributions are log normal. PM mean diameter increases with engine power condition.

Source: Lobo et al., Environ. Sci. Technol. 2011, 45, 10744–10749

g pSignificant differences observed between Jet A-1 and 100% FT fuels.

Engine Exit Plane – nvPM number and mass

CFM56‐7BNov 2007Nov 2007

GE Engine Test Facility

Measured reductions in PM were largest at idle, and smallest at ,maximum rated thrust.



Fuel Jet A Jet A‐1 20% FAME / 40% FAME / 50% FT / 100%FT/80% Jet A‐1

/60% Jet A‐1

/50% Jet A‐1

Aromatic content (vol %)

12.3 18.5 14.8 11.1 9.25 < 0.2(vol %)

CFM56‐7B


Nov 2007GE Engine Test Facility

nvPM Emissions reductions over the LTO Cycle

The LTO Cycle isCFM56‐7BNov 2007• The LTO Cycle is

intended to simulate aircraft engine operations that affect local air quality

GE Engine Test Facility

that affect local air quality (aircraft operations below 3000 feet altitude)

• It comprises the following power settings: 7% (idle/taxi) 30%(idle/taxi) 30% (approach), 85% (climb-out), and 100% (takeoff).



Fuel JP8 HRJ/HEFA HRJ/HEFA + JP8

FT (CTL)

FT + THT

CFM56‐2C1Mar/Apr 2011

Aromatic content (vol %) 21.8 0.4 10.2 1.4 2.1

Mar/Apr 2011AAFEX II campaign

Significant reductions in PM number- and mass-based emission indices are observed for the alternative fuels compared to conventional JP8 fuel

Plume evolution – PM number and massArtouste Mk113 APU

Sep/Oct 2009Sheffield APU StudySheffield APU Study

Condensation of organic species is the dominant process occurring asthe exhaust plume expands and cools (measured 10m downstream).

Source: Lobo et al., Environ. Sci. Technol. 2012

Plume evolution – Soluble Mass Fraction

Fuel Sulfur contentcontent(ppm)

FT (CTL) 4

HRJ/HEFA 6

JP8 188

HRJ/HEFA + JP8

276

FT + THT 1083

CFM56 2C1CFM56‐2C1Mar/Apr 2011

AAFEX II

Soluble Mass Fraction (SMF) increases with fuel sulfur content and engine power condition, and decreases with particle diameter (measured 145m downstream)

New Regulatory Method for nvPM

• ICAO/CAEP is currently in the process of developing a regulatory standard for non olatile PM (n PM) n mber and mass basedstandard for non-volatile PM (nvPM) number and mass-based emissions

SAE E 31commitee has defined an Aerospace Information Report• SAE E-31commitee has defined an Aerospace Information Report (AIR) 6241 that details the sampling system for the measurement of nvPM number- and mass-based emissions from aircraft engines. – This standard methodology will be converted into an AerospaceThis standard methodology will be converted into an Aerospace

Recommend Practice (ARP) which will then be used by engine manufacturers in the certification of aircraft engines for nvPM emissions.

– The system is designed to operate in parallel with existing ICAO Annex 16 compliant combustion gas sampling systems currently used for16 compliant combustion gas sampling systems currently used for emissions certification from aircraft engines.

– It consists of three sections – collection, transfer, and measurement –connected in series.

– Three reference systems• North American mobile reference system, operated by Missouri University of

Science and Technology• EU mobile reference system operated by the SAMPLE III consortiumEU mobile reference system, operated by the SAMPLE III consortium• Swiss fixed reference system, operated by Empa

Components of AIR6241 system

Source: SAE Aerospace Information Report (AIR) 6241 “Procedure for the Continuous Sampling and Measurement of Non-Volatile Particle Emissions from Aircraft Turbine Engines”, 2013

Conclusions

• Potential for large non-volatile PM emissions reduction gat the exit plane of the exhaust nozzle should alternative aviation fuels with specific fuel properties be adopted by the commercial aviation sectorp y

• Both non-volatile and volatile emissions need to be id d h d l i PM i iconsidered when developing PM emissions

inventories, and are essential in understanding the impact of aircraft engines burning alternative fuelsp g g

• Future regulation of aircraft engine PM emissions must also take fuel properties such as aromatic content intoalso take fuel properties such as aromatic content into account

Acknowledgments

Portions of this work were funded through the Partnership for AiRg pTransportation for Noise and Emissions Reduction (PARTNER) – a FAA-

NASA-Transport Canada-US DoD-US EPA-sponsored Center of Excellence, under Cooperative Agreement Nos: 07-C-NE-UMR and 09-C-NE-MSTunder Cooperative Agreement Nos: 07 C NE UMR and 09 C NE MST

Opinions, findings, conclusions, and recommendations expressed in this p g ppresentation are those of the author and do not necessarily reflect the views

of PARTNER sponsoring organizations.

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