Emissions from Alternate Aviation Fuels and their Environmental Impact

Track II: Transportation and BiofuelsIncludes audio file (19 min.)The anticipated growth in commercial air traffic, rising fuel costs, and an increasing desire to reduce reliance on fossil fuels produced in politically unstable regions, has driven research into alternate renewable fuels, either from biomass (Biofuels) or synthesis from coal, natural gas and other renewable feedstocks (Fischer-Tropsch (FT) fuels). Industry and government has recently sponsored (Dec 07, Jan 09) two engine emission tests led in part by the Missouri S&T team. The tests focused on burning alternative and conventional fuels and associated blends in CFM56-type commercial gas turbine engines. The CFM56 engine type is the most common engine in the global commercial fleet powering greater than 70% of the US domestic fleet. The purpose of these emission tests was to quantify any differences in particulate matter (PM) and hazardous air pollutants (HAP) emissions observed between the different fuels, and assess the environmental impacts that may result from these differences. The PM measurements indicate that, especially for the 100% F-T fuel, PM number and mass are diminished at all powers relative to conventional fuels. Some significant differences in hydro-carbon speciation were also observed for the 100% F-T fuel. Differences were less pronounce for the blends. This paper will present a concise summary of the results of these measurement campaigns along with an assessment of any associated environmental impact changes, focusing mainly on airport local air quality and the global atmosphere

Overview on the Aircraft Particle Emissions Experiment

Conducted at the NASA Dryden Flight Research Center during April 2004, the Aircraft Particle Emissions Experiment systematically investigated the gas-phase and particle emissions from a CFM56-2C1 engine on NASA\u27s DC-8 aircraft as functions of engine power, fuel composition, and exhaust-plume age. Emissions parameters were measured at 11 engine power settings ranging from idle to maximum thrust, in samples collected 1, 10, and 30 m downstream of the exhaust plane as the aircraft burned three fuels with different aromatic and sulfur contents. The 1- and 10-m sampling rakes contained multiple gas and particle inlet probes to facilitate a study of the spatial variation of emissions across the engine exhaust plane. Gas-phase emission indices measured at 1 m were in good agreement with the engine certification data as well as with predictions provided by the engine company. However, at low power settings, trace-species emissions were observed to be highly dependent on ambient conditions and engine temperature. Nonvolatile particles emitted by the engine exhibited a log-normal size distribution that peaked between 15 and 40 nm, depending on engine power. Samples collected 30 m downstream of the engine exit plane exhibited a prominent nucleation mode, indicating that secondary aerosols composed of sulfuric acid and lowvolatility organic species formed rapidly within the plume as it expanded and cooled. Black carbon emissions were a minimum at approach and a maximum at climb and takeoff engine power settings. Black carbon dominated total mass emissions at high thrust, whereas volatile particles contributed an equal or perhaps greater fraction at low- to midpower settings. Although variations in fuel aromatic content had no discernible impact on particle emissions, volatile particle number and mass concentrations in aged exhaust plumes were highly sensitive to the fuel sulfur content

Commercial Aircraft Engine Emissions Characterization of In-Use Aircraft At Hartsfield-Jackson Atlanta International Airport

The emissions from in-use commercial aircraft engines have been analyzed for selected gas-phase species and particulate characteristics using continuous extractive sampling 1-2 min downwind from operational taxi- and runways at Hartsfield-Jackson Atlanta International Airport. Using the aircraft tail numbers, 376 plumes were associated with specific engine models. In general, for takeoff plumes, the measured NOx emission index is lower (~18%) than that predicted by engine certification data corrected for ambient conditions. These results are an in-service observation of the practice of “reduced thrust takeoff”. The CO emission index observed in ground idle plumes was greater (up to 100%) than predicted by engine certification data for the 7% thrust condition. Significant differences are observed in the emissions of black carbon and particle number among different engine models/technologies. The presence of a mode at ~65 nm (mobility diameter) associated with takeoff plumes and a smaller mode at ~25 nm associated with idle plumes has been observed. An anticorrelation between particle mass loading and particle number concentration is observed

Evolution of Carbonaceous Aerosol and Aerosol Precursor Emissions Through a Jet Engine

This study conducted during the summers of 2000 and 2001 represents the first measurement and model intercomparison that tracks detailed gaseous and aerosol emissions through a gas turbine engine. Its primary objective was to determine the impacts of engine operational state on the evolution of carbonaceous aerosol and aerosol precursors. Emissions measurements were performed at the exit of a combustor and at the exit of a full engine for a gas turbine engine typical of the in-service, commercial aircraft fleet. Measurements were compared to model simulations of changes in gaseous chemistry. As predicted by the model simulations, results show no significant modifications to the aerosol distribution along the postcombustor flowpath. The oxidation of NO to HONO was measured. Trends with engine power setting and sulfur loading were at the level of estimated uncertainty limits. Simulations of the fluid and chemical processes through the turbine and exhaust nozzle correctly captured HONO trends and matched experimental data within measurement uncertainty. This suggests that the employed modeling approach is valid for HONO chemistry, and more generally, because HONO results from NO oxidation via the hydroxyl radical, indicates the importance of OH-driven oxidation through the engine. These results indicate that the chemical and physical processes occurring in the turbine are important in determining aircraft engine emission

Determination of the Emissions from an Aircraft Auxiliary Power Unit (APU) During the Alternative Aviation Fuel Experiment (AAFEX)

The emissions from a Garrett-AiResearch (now Honeywell)Model GTCP85-98CK auxiliary power unit (APU) were determined as part of the National Aeronautics and Space Administration\u27s (NASA\u27s) Alternative Aviation Fuel Experiment (AAFEX) using both JP-8 and a coal-derived Fischer Tropsch fuel (FT-2). Measurements were conducted by multiple research organizations for sulfur dioxide (SO2), total hydrocarbons (THC), carbonmonoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), speciated gas-phase emissions, particulatematter (PM)mass and number, black carbon, and speciated PM. In addition, particle size distribution (PSD), number-based geometric mean particle diameter (GMD), and smoke number were also determined from the data collected. The results of the research showed PM mass emission indices (EIs) in the range of 20 to 700 mg/kg fuel and PM number EIs ranging from 0.5 x1015 to 5 x1015 particles/kg fuel depending on engine load and fuel type. In addition, significant reductions in both the SO2 and PMEIs were observed for the use of the FT fuel. These reductions were on the order of~90%for SO2 and particlemass EIs and~60%for the particle number EI, with similar decreases observed for black carbon. Also, the size of the particles generated by JP-8 combustion are noticeably larger than those emitted by the APU burning the FT fuel with the geometric mean diameters ranging from 20 to 50 nm depending on engine load and fuel type. Finally, both particle-bound sulfate and organics were reduced during FT-2 combustion. The PM sulfatewas reduced by nearly 100% due to lack of sulfur in the fuel, with the PM organics reduced by a factor of ~5 as compared with JP-8