Impact of alternative fuels on emissions characteristics of a gas turbine engine - part 1: gaseous and particulate matter emissions.

Growing concern over emissions from increased airport operations has resulted in a need to assess the impact of aviation related activities on local air quality in and around airports, and to develop strategies to mitigate these effects. One such strategy being investigated is the use of alternative fuels in aircraft engines and auxiliary power units (APUs) as a means to diversify fuel supplies and reduce emissions. This paper summarizes the results of a study to characterize the emissions of an APU, a small gas turbine engine, burning conventional Jet A-1, a fully synthetic jet fuel, and other alternative fuels with varying compositions. Gas phase emissions were measured at the engine exit plane while PM emissions were recorded at the exit plane as well as 10 m downstream of the engine. Five percent reduction in NO(x) emissions and 5-10% reduction in CO emissions were observed for the alternative fuels. Significant reductions in PM emissions at the engine exit plane were achieved with the alternative fuels. However, as the exhaust plume expanded and cooled, organic species were found to condense on the PM. This increase in organic PM elevated the PM mass but had little impact on PM number.

Polycyclic aromatic hydrocarbon emissions from the combustion of alternative fuels in a gas turbine engine.

We report on the particulate-bound polycyclic aromatic hydrocarbons (PAH) in the exhaust of a test-bed gas turbine engine when powered by Jet A-1 aviation fuel and a number of alternative fuels: Sasol fully synthetic jet fuel (FSJF), Shell gas-to-liquid (GTL) kerosene, and Jet A-1/GTL 50:50 blended kerosene. The concentration of PAH compounds in the exhaust emissions vary greatly between fuels. Combustion of FSJF produces the greatest total concentration of PAH compounds while combustion of GTL produces the least. However, when PAHs in the exhaust sample are measured in terms of the regulatory marker compound benzo[a]pyrene, then all of the alternative fuels emit a lower concentration of PAH in comparison to Jet A-1. Emissions from the combustion of Jet A-1/GTL blended kerosene were found to have a disproportionately low concentration of PAHs and appear to inherit a greater proportion of the GTL emission characteristics than would be expected from volume fraction alone. The data imply the presence of a nonlinear relation between fuel blend composition and the emission of PAH compounds. For each of the fuels, the speciation of PAH compounds present in the exhaust emissions were found to be remarkably similar (R(2) = 0.94-0.62), and the results do provide evidence to support the premise that PAH speciation is to some extent indicative of the emission source. In contrast, no correlation was found between the PAH species present in the fuel with those subsequently emitted in the exhaust. The results strongly suggests that local air quality measured in terms of the particulate-bound PAH burden could be significantly improved by the use of GTL kerosene either blended with or in place of Jet A-1 kerosene.

Comparison of PM emissions from a commercial jet engine burning conventional, biomass, and Fischer-Tropsch fuels.

Rising fuel costs, an increasing desire to enhance security of energy supply, and potential environmental benefits have driven research into alternative renewable fuels for commercial aviation applications. This paper reports the results of the first measurements of particulate matter (PM) emissions from a CFM56-7B commercial jet engine burning conventional and alternative biomass- and, Fischer-Tropsch (F-T)-based fuels. PM emissions reductions are observed with all fuels and blends when compared to the emissions from a reference conventional fuel, Jet A1, and are attributed to fuel properties associated with the fuels and blends studied. Although the alternative fuel candidates studied in this campaign offer the potential for large PM emissions reductions, with the exception of the 50% blend of F-T fuel, they do not meet current standards for aviation fuel and thus cannot be considered as certified replacement fuels. Over the ICAO Landing Takeoff Cycle, which is intended to simulate aircraft engine operations that affect local air quality, the overall PM number-based emissions for the 50% blend of F-T fuel were reduced by 34 ± 7%, and the mass-based emissions were reduced by 39 ± 7%.

Quantification of F(2)-isoprostane isomers in cultured human lung epithelial cells after silica oxide and metal oxide nanoparticle treatment by liquid chromatography/tandem mass spectrometry.

F(2)-isoprostanes are lipid peroxidation products of arachidonic acid in cell membrane and are reliable biomarkers for oxidative stress and cell membrane damage. Nanomaterials are widely used as raw materials in many industries and will have high potentials to be used in life science and medical fields. However, the human health impact of nanoparticles has caused people's great concern. Unfortunately, the mechanisms of cytotoxicity of many nanoparticles are not well defined. By measuring the levels of F(2)-isoprostane isomers in cultured cells after nanoparticle exposure, the information can be used to explain whether the cytotoxicity of nanoparticles is caused by lipid peroxidation and to investigate the biological pathways. In this study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to separate and quantify F(2)-isoprostane isomers in nanoparticle-treated human lung cancer cells. Silica oxide (15nm) and other four metal oxide nanoparticles including Fe(2)O(3) (30nm), Al(2)O(3) (13nm), TiO(2) (40nm) and ZnO (70nm) are chosen in this study. The isotope forms of F(2)-isoprostane isomers, 8-iso-PGF(2alpha)-d(4) and PGF(2alpha)-d(4), were used as internal standard (IS). After human lung epithelial cells were exposed to different nanoparticles for 24h, F(2)-isoprostanes were extracted by a single step solid phase extraction with Oasis HLB cartridge. For the first time, six F(2)-isoprostane isomers were tentatively identified and quantified in human lung epithelial cells. The levels of F(2)-isoprostane isomers in the cells increased after the treatment with nanoparticles. For SiO(2), Fe(2)O(3), and ZnO nanoparticles, F(2)-isoprostane isomers increasing are consistent with nanoparticles' cytotoxicity data. For Al(2)O(3) and TiO(2) nanoparticles, F(2)-isoprostane isomers levels increased even before nanoparticles showed significant cytotoxicity at 100microg/mL concentration in 24h. Based on our best knowledge, this is the first study on the F(2)-isoprostane isomers corresponding to nanoparticles' exposure in vitro. Our study demonstrates that SiO(2) (15nm) nanoparticle showed the highest degree of lipid peroxidation and cell membrane damage among the studied nanoparticles.

N-acetylcysteineamide (NACA) prevents inflammation and oxidative stress in animals exposed to diesel engine exhaust.

Diesel exhaust particles (DEPs), a by-product of diesel engine exhaust (DEE), are one of the major components of air borne particulate matter (PM) in the urban environment. DEPs are composed of soot, polycyclic aromatic hydrocarbons (PAHs), redox active semi-quinones, and transition metals, which are known to produce pro-oxidative and pro-inflammatory effects, thereby leading to oxidative stress-induced damage in the lungs. The objective of this study was to determine if N-acetylcysteineamide (NACA), a novel thiol antioxidant, confers protection to animals exposed to DEPs from oxidative stress-induced damage to the lung. To study this, male C57BL/6 mice, pretreated with either NACA (250mg/kg body weight) or saline, were exposed to DEPs (15mg/m(3)) or filtered air (1.5-3h/day) for nine consecutive days. The animals were sacrificed 24h after the last exposure. NACA-treated animals exposed to DEP had significant decreases in the number of macrophages and the amount of mucus plug formation in the lungs, as compared to the DEP-only exposed animals. In addition, DEP-exposed animals, pretreated with NACA, also experienced significantly lower oxidative stress than the untreated group, as indicated by the glutathione (GSH), and malondialdehyde (MDA) levels and catalase (CAT) activity. Further, DEP-induced toxicity in the lungs was reversed in NACA-treated animals, as indicated by the lactate dehydrogenase levels. Taken together, these data suggest that the thiol-antioxidant, NACA, can protect the lungs from DEP-induced inflammation and oxidative stress related damage.

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 (approximately 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 approximately 65 nm (mobility diameter) associated with takeoff plumes and a smaller mode at approximately 25 nm associated with idle plumes has been observed. An anticorrelation between particle mass loading and particle number concentration is observed.