Exhaust Emissions from In-Use General Aviation Aircraft (2016)

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79 The carbon content of aircraft fuel is essential in calculating accurate emission indices. The usual carbon content used in aircraft emissions work is 3160 g CO2/kg fuel, which assumes a hydrogen/carbon ratio, or a, of 1.9. Although carbon content is appropriate for kerosene-based Jet A fuel, it is not necessarily appropriate for AVGAS 100LL. FOCA uses a carbon content of 3118 g CO2/kg fuel (a = 2.086) based on hydrocarbon information from the fuel supplier Chevron (FOCA 2007b). Table K-1 lists the manufacturer’s information available for the AVGAS 100LL fuel present at one of the test airports. No carbon content information was available. To verify the carbon content of the AVGAS used in these engine tests, two fuel tests were done on collected samples. Under-wing samples (directly from the aircraft’s fuel reservoir) were taken from each tested aircraft, and additional samples were taken from each airport’s fuel dispensaries. However, carbon content testing was performed on only two samples due to the high cost of testing. The two samples sent for testing were 1. FBO Mix: A mix of equal volumes of fuel from three separate FBOs, 2. High Aromatics: An under-wing sample from an aircraft showing high amounts of aromatics in the fuel. Two standardized tests from the American Society for Testing and Materials (ASTM) were requested: 1. ASTM D5291: Determination of Carbon and Hydrogen in Petroleum Products and Lubricants and 2. ASTM D5769: Benzene, Toluene and Total Aromatics in Finished Gasoline by GCMS Results are shown in Table K-2. The fuel from the mix of FBOs has a somewhat lower car- bon content than either the Jet A (3.0% lower) or the FOCA AVGAS results (3.4% lower). The high-aromatics fuel sample is similarly lower in carbon content. The research team use 3067 g/kg fuel as the carbon content of AVGAS 100LL in all results presented in this report and 3160 g/kg fuel for Jet A. This comparison of carbon contents shows only small differences between samples that should not significantly affect the calculated emission indices: errors in EIs are less than ~3.4%. Although differences in carbon content between different fuels are small, the differences in aromatics may be large. The ASTM D5769 method used in the detection of aromatics cannot detect levels below 10%, and so the difference between the FBO mix sample and the high aromatic sample may be anywhere between 4.5% and 14.5%. The presence of aromatics, specifically toluene, in a subset of fuel samples is investigated in more detail in the section on fuel additives. A P P E N D I X K Carbon Content of AVGAS 100 LL

80 Exhaust Emissions from In-Use General Aviation Aircraft Table K-2. Carbon content of aircraft fuel. Specificaon Jet A AVGAS 100LL FOCA AVGAS 100LL FBO Mix AVGAS 100LL high aromacs mass % H (m/m) 13.8% 8.03% 16.3% 14.9% (H/C rao) 1.901 1.857 2.320 2.086 Fuel C (g/kg Fuel) 862.4 865.2 837.0 851.0 Fuel CO2 (g/kg Fuel) 3160 3170 3067 3118 Aromacs (v/v) <10% 14.50% Table K-1. Manufacturer’s specification sheet for AVGAS 100LL. Min ValueShell AVGAS Specificaon Max Value Knock Rang, Lean Mixture (Motor Method) Octane Number 99.5 Knock Rang, Rich Mixture (Supercharge Method) Performance Number 130 Freezing Point C 58 Disllaon end point °C 170 Reid Vapour Pressure @ 38 °C kPa 49 38 Sulphur content %m 0.05 Tetraethyl lead content g Pb/L Avgas 100 0.85 Avgas 100LL 0.56 Colour Avgas 100 Avgas 100LL Green Blue

81 A P P E N D I X L An important task in computing an airport’s emissions burden is to map the aircraft to emissions data available in various databases. In Table L-1, the hypothetical airport used for the sensitivity analysis is mapped to engines from 1. The set of experimentally sampled planes 2. Data available in EDMS/AEDT The comments column explains how these mappings and substitutions were done. Hypothetical Airport Engine Mapping (continued on next page) Table L-1. Hypothetical fleet matched with sampled engines. Hypothecal Fleet Sampled Engine Model EDMS/AEDT Match Comments Category Aircra Make Aircra Model Engine Family Aircra Make Aircra Model Engine Model SEP CESSNA 172 O 320 O 320 Cessna 172 O 320 Exact match with Hypothecal Fleet and sampled aircra/engine. CESSNA 182 O 470 O 470 Cessna 182 IO 360 B No O 470 in EDMS; chose IO 360 because (only opon for Cessna 182) similar horsepower (hp). CESSNA 150 O 200 O 200 Cessna 150 O 200 Exact match with Hypothecal Fleet and sampled aircra/engine. PIPER PA 28 O 320 O 320 Piper PA 28 O 320 Exact match with Hypothecal Fleet and sampled aircra/engine. CESSNA 172 O 300 Cessna 172 O 320 No O 300 in EDMS; chose O 320 because similar hp. PIPER PA 28 O&VO 360 O 360 Piper PA 28 IO 360 B No O 360 in EDMS; chose IO 360 because similar hp. CIRRUS DESIGN CORP SR22 IO 550 IO 550 Cirrus Design Corp SR22 TIO 540 J2B2 No IO 550 in EDMS; chose TIO 540 J2B2 because (only opon for SR 22) similar hp. MOONEY M20 IO 360 IO 360 Cessna 337 IO 360 B Exact Engine match; matched to Cessna 337 because M20 engine hp too high and Cessna 337 has correct engine and is similar aircra.