High Altitude Emissions

An overview of emissions related research being conducted as part of the Fundamental Aeronautics Supersonics Project is presented. The overview includes project objectives, milestones, and descriptions of major research areas. The overview also includes information on the emissions research being conducted under NASA Research Announcements. Technical challenges include: 1) Environmental impact of supersonic cruise emissions is greater due to higher flight altitudes which makes emissions reduction increasingly important. 2) Accurate prediction tools to enable combustor designs that reduce emissions at supersonic cruise are needed as well as intelligent systems to minimize emissions. 3) Combustor operating conditions at supersonic cruise are different than at subsonic cruise since inlet fuel and air temperatures are considerably increased

Current Status of Superheat Spray Modeling With NCC

An understanding of liquid fuel behavior at superheat conditions is identified to be a topic of importance in the design of modern supersonic engines. As a part of the NASA's supersonics project office initiative on high altitude emissions, we have undertaken an effort to assess the accuracy of various existing CFD models used in the modeling of superheated sprays. As a part of this investigation, we have completed the implementation of a modeling approach into the national combustion code (NCC), and then applied it to investigate the following three cases: (1) the validation of a flashing jet generated by the sudden release of pressurized R134A from a cylindrical nozzle, (2) the differences between two superheat vaporization models were studied based on both hot and cold flow calculations of a Parker-Hannifin pressure swirl atomizer, (3) the spray characteristics generated by a single-element LDI (Lean Direct Injector) experiment were studied to investigate the differences between superheat and non-superheat conditions. Further details can be found in the paper

Alternative Aviation Fuel Experiment II (AAFEX II) Overview

No abstract availabl

Biofuel Blending Reduces Aircraft Engine Particle Emissions at Cruise Conditions

Aviation aerosol emissions have a disproportionately large climatic impact because they are emitted high in the relatively pristine upper troposphere where they can form linear contrails and influence cirrus clouds. Research aircraft from NASA, DLR, and NRC Canada made airborne measurements of gaseous and aerosol composition and contrail microphysical properties behind the NASA DC-8 aircraft at cruise altitudes. The DC-8 CFM-56-2C engines burned traditional medium-sulfur Jet A fuel as well as a low-sulfur Jet A fuel and a 50:50 biofuel blend. Substantial, two-to-three-fold emissions reductions are found for both particle number and mass emissions across the range of cruise thrust operating conditions. These observations provide direct and compelling evidence for the beneficial impacts of biojet fuel blending under real-world conditions

Multilevel Spiral Axicon for High-Order Bessel–Gauss Beams Generation

This paper presents an efficient method to generate high-order Bessel–Gauss beams carrying orbital angular momentum (OAM) by using a thin and compact optical element such as a multilevel spiral axicon. This approach represents an excellent alternative for diffraction-free OAM beam generation instead of complex methods based on a doublet formed by a physical spiral phase plate and zero-order axicon, phase holograms loaded on spatial light modulators (SLMs), or the interferometric method. Here, we present the fabrication process for axicons with 16 and 32 levels, characterized by high mode conversion efficiency and good transmission for visible light (λ = 633 nm wavelength). The Bessel vortex states generated with the proposed diffractive optical elements (DOEs) can be exploited as a very useful resource for optical and quantum communication in free-space channels or in optical fibers

Biofuel blending reduces particle emissions from aircraft engines at cruise conditions

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate1. The magnitude of air-traffic-related aerosol–cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC‐8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change

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

Gaseous and Particulate Emissions Results of the NASA Alternative Aviation Fuel Experiment (AAFEX)

The Aircraft Alternative Fuels Emissions eXperiment (AAFEX) was conducted at National Aeronautic and Space Administration (NASA) Dryden Flight Research Center (DFRC) Aircraft Operations Facility (DAOF) in Palmdale, California, during January and February 2009. The purpose was to systematically investigate the effect of alternative fuels on both gas-phase and particle emissions from a CFM56-2C1 engine on NASA\u27s DC-8 aircraft parked on the ground as functions of engine power, fuel composition, and exhaust plume age. Emissions parameters were measured at 6 engine power settings, ranging from idle to maximum thrust, in samples collected at 1, 30, and 145 meters (m) downstream of the exhaust plane as the aircraft burned three pure fuels and two fuel blends. The fuels included JP-8, two fuels produced using the Fischer-Tropsch process and 50/50 blends by volume of the F-T fuels with JP-8. The 1 m sampling rakes contained multiple gas and particle inlet probes and could also be traversed in order to measure the spatial variation of emissions across the engine exhaust plane. The #2 inboard engine on the left side always burned JP-8 while the #3 inboard right side engine was fueled with the various fuels and fuel blends. In addition, emissions from the Auxiliary Power Unit (APU) were also evaluated with both JP-8 and one pure F-T fuel. Both gaseous and particulate emissions are presented. Results show that the synthetic fuels reduced pollutant emissions while having relatively little effect on engine operation or performance