Impact of alternative fuels on the PM emissions characteristics of gas turbine engines

The growth in the commercial aviation sector has raised concerns about the impact of emissions from aircraft operations on local and regional air quality, climate change, and health-related effects. The lack of Particulate Matter (PM) emissions data from gas turbine engines coupled with the increasing interest in the use of alternative fuels as a potential emissions mitigation strategy are the motivating factors behind this thesis. A total of seven peer-reviewed archival journal publications form the basis of this work. It commences with two field studies that were performed at the Oakland International Airport and the Hartsfield-Jackson Atlanta International Airport to measure the characteristics of aircraft engine specific PM emissions at the engine exit plane and in the near field as the exhaust plume expands and cools. Having characterised the PM emissions from various aircraft gas turbine engine types, the significant impact that alternative fuels can have on the PM emissions characteristics was explored and the results were correlated with fuel properties. A new robust and standardised methodology for the measurement of non-volatile PM emissions is described, and its reproducibility against other systems is demonstrated. Finally this standardized system was used in a detailed examination of the impact of fuel composition on the characteristics of the emitted non-volatile PM from a gas turbine engine. These publications and the resulting data improved the characterisation and quantification of PM emissions for a wide variety of gas turbine engines burning conventional and alternative fuels. PM emissions from aircraft gas turbine engines at airports were found to have bimodal size distributions, consisting of a nucleation mode with volatile PM and an accumulation mode with volatile PM condensed on the surface of non-volatile PM. Fuel properties were found to have a significant impact on the production of PM. The reductions in PM emissions with alternative fuels were best correlated with fuel hydrogen content. The data and analysis from these publications will be used to improve/validate current environmental impact predictive tools with real world aircraft gas turbine engine specific PM emissions inputs and develop effective emissions mitigation strategies

PM Emission From a Commercial Jet Engine -- Project APEX

Project APEX (Aircraft Particle Emissions eXperiment) was a multi-agency commercial aircraft emission characterization and technology demonstration experiment. Its objective was to characterize particle and trace gas precursor species in the emissions from a NASA DC-8 aircraft with General Electric CFM56-2C1 engines at the engine exit plane as well as selected down stream locations. This was to advance the understanding of particle emissions and their evolution in the atmosphere from a current in-service turbofan engine. The test was conducted at the NASA Dryden Flight Research Center at Edwards Air Force Base California during April 15-30, 2004. Participants included the National Aeronautics and Space Administration, Environmental Protection Agency, Federal Aviation Administration, Department of Defense, the aviation industry (General Electric, Pratt and Whitney, and Boeing), and the research community (Aerodyne Research Inc., Massachusetts Institute of Technology, Process Metrix, University of California-Riverside, and University of Missouri-Rolla)

Influence of Ambient Temperature on the PM Emissions from a Gas Turbine Engine

During Project AAFEX, PM emissions measurements were conducted on a CFM56-2C1 gas turbine engine in January 2009 in Palmdale CA. The engine was mounted on a NASA DC-8 aircraft, which was parked on the runway, and emission samples were extracted at the engine exit plane (1m), in the near field (30m), and in the advected plume (145m). The engine was operated at several power levels, and burned several fuels: JP-8, a Fischer-Tropsch fuel derived from natural gas (FT1), and a second Fischer-Tropsch fuel derived from gasified coal (FT2). In addition to these fuels, 50:50 blends of the Fischer-Tropsch fuels and JP-8 were also studied. Wide variations in ambient temperature, especially between early morning and late afternoon were experienced during the campaign. This report summarizes and describes the results of AAFEX, in terms of the influence of ambient temperature on total PM emissions at the exit plane of a CFM56-2C1 engine

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

Systematic experimental comparison of particle filtration efficiency test methods for commercial respirators and face masks

Respirators, medical masks, and barrier face coverings all filter airborne particles using similar physical principles. However, they are tested for certification using a variety of standardized test methods, creating challenges for the comparison of differently certified products. We have performed systematic experiments to quantify and understand the differences between standardized test methods for N95 respirators (NIOSH TEB-APR-STP-0059 under US 42 CFR 84), medical face masks (ASTM F2299/F2100), and COVID-19-related barrier face coverings (ASTM F3502-21). Our experiments demonstrate the role of face velocity, particle properties (mean size, size variability, electric charge, density, and shape), measurement techniques, and environmental preconditioning. The measured filtration efficiency was most sensitive to changes in face velocity and particle charge. Relative to the NIOSH method, users of the ASTM F2299/F2100 method have commonly used non-neutralized (highly charged) aerosols as well as smaller face velocities, each of which may result in approximately 10% higher measured filtration efficiencies. In the NIOSH method, environmental conditioning at elevated humidity increased filtration efficiency in some commercial samples while decreasing it in others, indicating that measurement should be performed both with and without conditioning. More generally, our results provide an experimental basis for the comparison of respirators certified under various international methods, including FFP2, KN95, P2, Korea 1st Class, and DS2.Comment: 34 pages, 8 figures, 3 table

Typical and Atypical Morphology of Non-volatile Particles from a Diesel and Natural Gas Marine Engine

ABSTRACT Non-volatile particle emissions from a marine engine fueled by either diesel or natural gas (NG) blended with diesel pilot gas were investigated via transmission electron microscopy (TEM). The most common particles (> 95% by number) were soot aggregates. These "typical" aggregates exhibited primary particle diameters of 20.7 ± 1.9 and 26.9 ± 1.7 for 100 nm aggregates when diesel and NG fuel were used, respectively. Highly non-uniform aggregates, with distinct groups of smaller and larger monomers, were visible in all of the samples but occurred most frequently with diesel fueling at high loads. The observed "atypical" particles included super-aggregates, small compact aggregates, spheres, mineral-like polyhedral particles, and fibers. Such particles, although rare (averaging 3% by number, as calculated by counting the number of particles for each type depicted in all of the collected images), were found in most of the samples and could have been produced by a variety of mechanisms. For instance, the spheres (approximately 300 nm in diameter) most likely arose from metals within the lubricating oil

Aircraft Engine Particulate Matter Emissions from Sustainable Aviation Fuels: Results from Ground-Based Measurements during the NASA/DLR Campaign ECLIF2/ND-MAX

The use of alternative jet fuels by commercial aviation has increased substantially in recent years. Beside the reduction of carbon dioxide emission, the use of sustainable aviation fuels (SAF) may have a positive impact on the reduction of particulate emissions. This study summarizes the results from a ground-based measurement activity conducted in January 2018 as part of the ECLIF2/ND-MAX campaign in Ramstein, Germany. Two fossil reference kerosenes and three different blends with the renewable fuel component HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) were burned in an A320 with V2527-A5 engines to investigate the effect of fuel naphthalene/aromatic content and the corresponding fuel hydrogen content on non-volatile particle number and mass emissions. Reductions up to 70% in non-volatile particle mass emission compared to the fossil reference fuel were observed at low power settings. The reduction trends to decrease with increasing power settings. The fuels showed a decrease in particle emission with increasing fuel hydrogen content. Consequently, a second fossil fuel with similar hydrogen content as one of the HEFA blends featured similar reduction factors in particle mass and number. Changes in the fuel naphthalene content had significant impact on the particle number emission. A comparison to in-flight emission data shows similar trends at cruise altitudes. The measurements highlight the importance of individual fuel components in regulating engine emissions, particularly at the low thrust settings typically employed during ground operations (e.g. during idle and taxi). Therefore, when selecting and mixing SAF blends to meet present fuel-certification standards, attention should be paid to minimizing complex aromatic content to achieve the greatest possible air quality and climate benefits

Aircraft engine particulate matter emissions from sustainable aviation fuels: Results from ground-based measurements during the NASA/DLR campaign ECLIF2/ND-MAX

The use of alternative jet fuels by commercial aviation has increased substantially in recent years. Beside the reduction of carbon dioxide emission, the use of sustainable aviation fuels (SAF) may have a positive impact on the reduction of particulate emissions. This study summarizes the results from a ground-based measurement activity conducted in January 2018 as part of the ECLIF2 ND-MAX campaign in Ramstein, Germany. Two fossil reference kerosenes and three different blends with the renewable fuel component HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) were burned in an A320 with V2527-A5 engines to investigate the effect of fuel naphthalene aromatic content and the corresponding fuel hydrogen content on nonvolatile particle number and mass emissions

Measurements of particle emissions and contrail ice particle properties behind a large passenger aircraft burning 100% sustainable aviation fuel in cruise

The use of sustainable aviation fuels (SAF) derived from biomass and waste materials can provide one approach to partially decarbonize air traffic relatively quickly and offers a pathway to mitigate the non-CO2 climate impacts from long-lived contrails on short time scales. Many SAFs naturally contain no or only low amounts of aromatic compounds which act as soot precursors during combustion. As soot particles serve as primary nucleus for contrail ice, lower soot emissions should result in lower contrail ice particle numbers. In the joint project ECLIF3 (Emissions and Climate Impact of alternative Fuels), DLR, Airbus, Rolls-Royce, Neste and other participants aimed to characterize emissions and contrail properties behind a modern passenger aircraft burning both conventional Jet A-1 fuel and HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) and a blend of HEFA-SPK and Jet A-1 on both engines on the ground and in flight. For the first time, flight tests in cruise using 100% HEFA-SPK on all engines were feasible in this framework. In two field campaigns in 2021 an Airbus A350-900 equipped with Rolls Royce Trent XWB-84 engines served as source aircraft. With the DLR Falcon 20E5 research aircraft we probed trace gases, volatile and non-volatile particles, and ice particle properties. The independent fuel tanks of the A350 permitted us to sample emissions from reference Jet A-1 and HEFA-SPK in similar meteorological conditions. Measurements of the exhaust closely behind the engine exit and up to several minutes behind the lead aircraft allowed us to characterize both, direct engine emissions depending on engine thrust conditions and the effects on contrail formation and properties. With respect to the Jet A-1 used here, we find a significant reduction in non-volatile particle emissions when burning HEFA-SPK; similar trends are seen in the ice particle numbers in the contrails. The results outline the importance of fuel composition (e.g. sulfur and aromatics content) on particle emissions and contrail formation. The analysis also shows the complexity of the contrail formation process and its dependence on fuel composition, engine thrust and meteorological conditions in the ambient atmosphere