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  • 1
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    In situ observations in aircraft exhaust plumes in the lower stratosphere at midlatitudes (1995)
    American Geophysical Union
    Details
    Publication Date: 1995-01-01
    Print ISSN: 0148-0227
    Electronic ISSN: 2156-2202
    Topics: Geosciences
    Published by American Geophysical Union
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    PAPER CURRENT
  • 2
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    In situ observations in aircraft exhaust plumes in the lower stratosphere at midlatitudes (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Instrumentation on the NASA ER-2 high-altitude aircraft has been used to observe engine exhaust from the same aircraft while operating in the lower stratosphere. Encounters with the exhaust plume occurred approximately 10 min after emission with spatial scales near 2 km and durations of up to 10 s. Measurements include total reactive nitrogen, NO(y), the component species NO and NO2, CO2, H2O, CO, N2O, condensation nuclei, and meteorological parameters. The integrated amounts of CO2 and H2O during the encounters are consistent with the stoichiometry of fuel combustion (1:1 molar). Emission indices (EI) for NO(x) (= NO + NO2), CO, and N2O are calculated using simultaneous measurements of CO2. EI values for NO(x) near 4 g/(kg fuel) are in good agreement with values scaled from limited ground-based tests of the ER-2 engine. Non-NO(x) species comprise less than about 20% of emitted reactive nitrogen, consistent with model evaluations. In addition to demonstrating the feasibility of aircraft plume detection, these results increase confidence in the projection of emissions from current and proposed supersonic aircraft fleets and hence in the assessment of potential long-term changes in the atmosphere.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 100; D2; p. 3065-3074
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    In situ observations in aircraft exhaust plumes in the lower stratosphere at mid-latitudes (1994)
    In:  CASI
    Details
    Publication Date: 2009-11-16
    Description: The effect of NO(x) (NO + NO2) from aircraft engine exhaust on ozone and climate is of increasing concern as a result of anticipated growth in the world's subsonic aircraft fleet and new international efforts to build a supersonic transport (SST). Knowledge of NO(x) emissions currently relies on limited ground based testing of combustors and engines and on scaling relations to extrapolate emission values to upper atmosphere conditions. Direct observations made in the engine exhaust plume of the NASA ER-2 high altitude aircraft cruising at subsonic speeds in the lower midlatitude stratosphere are presented. Results demonstrate the technical feasibility of detecting aircraft plumes within minutes after emission with sufficient completeness and precision to calculate emission indices for reactive nitrogen and other species. Furthermore, the combined results increase confidence in using ground based observations to assess the atmospheric impact of some aircraft emissions.
    Keywords: ENVIRONMENT POLLUTION
    Type: DLR, Impact of Emissions From Aircraft and Spacecraft Upon the Atmosphere; p 321-322
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    The NASA broad specification fuels combustion technology program at Pratt and Whitney (1984)
    In:  CASI
    Details
    Publication Date: 2006-04-09
    Description: The technology required to accommodate the use of broadened properties fuels in commercial aircraft engine combustors with minimum impact on the emissions, performance, durability and engine operational characteristics is discussed. Emphasis was placed on defining the potential for reducing the fuel sensitivity of the reference combustion system through design refinements and the introduction of more advanced technology combustors. To this end the tests conducted included the evaluation of variations of three different combustor concepts representing progressively more advanced technology levels. It was demonstrated that reduced fuel hydrogen content has adverse impacts on current single stage combustors; the best opportunities for reducing the fuel sensitivity of these combustors are through improved fuel injectors and advanced liner cooling and structural concepts and that the advanced technology staged and variable geometry combustor concepts have inherent operational flexibility that can be exploited to accommodate changes in fuel composition. Also, advanced technology combustor concepts were evaluated. A variable geometry combustor capable of airflow modulation during operation and a new concept which is a further evolution of the Vorbix combustor are discussed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NASA. Lewis Research Center Assessment of Alternative Aircraft Fuels; p 99-110
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Broad Specification Fuels Combustion Technology Program, Phase 2 (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental evaluation of two advanced technology combustor concepts was conducted to evolve and assess their capability for operation on broadened properties fuels. The concepts were based on the results of Phase 1 of the Broad Specification Fuel Combustor Technology Program which indicated that combustors with variable geometry or staged combustion zones had a flexibility of operation that could facilitate operation on these fuels. Emphasis in defining these concepts included the use of single pipe as opposed to duplex or staged fuels systems to avoid the risk of coking associated with the reduction in thermal stability expected in broadened properties fuels. The first concept was a variable geometry combustor in which the airflow into the primary zone could be altered through valves on the front while the second was an outgrowth of the staged Vorbix combustor, evolved under the NASA/P&W ECCP and EEE programs incorporating simplified fuel and air introduction. The results of the investigation, which involved the use of Experimental Referee Broad Specification (ERBS) fuel, indicated that in the form initially conceived, both of these combustor concepts were deficient in performance relative to many of the program goals for performance emissions. However, variations of both combustors were evaluated that incorporated features to simulate conceptual enhancement to demonstrate the long range potential of the combustor. In both cases, significant improvements relative to the program goals were observed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: NASA-CR-191066 , NAS 1.26:191066
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Advanced composite combustor structural concepts program (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-174733 , NAS 1.26:174733 , PWA-5890-24
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    High-speed Civil Transport Aircraft Emissions (1992)
    In:  CASI
    Details
    Publication Date: 2014-09-23
    Description: Estimates are given for the emissions from a proposed high speed civil transport (HSCT). This advanced technology supersonic aircraft would fly in the lower stratosphere at a speed of roughly Mach 1.6 to 3.2 (470 to 950 m/sec or 920 to 1850 knots). Because it would fly in the stratosphere at an altitude in the range of 15 to 23 km commensurate with its design speed, its exhaust effluents could perturb the chemical balance in the upper atmosphere. The first step in determining the nature and magnitude of any chemical changes in the atmosphere resulting from these proposed aircraft is to identify and quantify the chemically important species they emit. Relevant earlier work is summarized, dating back to the Climatic Impact Assessment Program of the early 1970s and current propulsion research efforts. Estimates are provided of the chemical composition of an HSCT's exhaust, and these emission indices are presented. Other aircraft emissions that are not due to combustion processes are also summarized; these emissions are found to be much smaller than the exhaust emissions. Future advances in propulsion technology, in experimental measurement techniques, and in understanding upper atmospheric chemistry may affect these estimates of the amounts of trace exhaust species or their relative importance.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA, Washington, The Atmospheric Effects of Stratospheric Aircraft: A First Program Report; p 13-31
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    The broadened-specification fuels combustion technology program at Pratt and Whitney Aircraft (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The impact of the use of broadened specification fuels on combustor design was investigated. Particular emphasis was placed on establishing the viability of various combustor modifications to permit the use of broadened specification fuels while meeting exhaust emissions and performance specifications and maintaining acceptable combustor operational and durability characteristics. Three different combustor concepts will be evaluated. Various design modifications on the operating capability of each of the combustor concepts with experimental referee broadened specification Fuel. The modifications that were evaluated included perturbations of the combustor airflow schedules to alter local stoichiometry and residence time histories revisions to the fuel injectors, and variations in liner cooling including the use of thermal barrier coatings and/or advanced cooling concepts.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA. Lewis Res. Center Aircraft Res. and Technol. for Future Fuels; p 105-108
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Experimental study of cross flow mixing in cylindrical and rectangular ducts (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental investigation of non-reacting cross flow jet injection and mixing in cylindrical and rectangular ducts has been conducted with application to a low emissions combustor. Quantitative measurement of injectant concentration distributions perpendicular to the duct axis were obtained by planar digital imaging of the Mie-scattered light from an aerosol seed mixed with the injectant. The flowfield unmixedness was evaluated using (1) a mixing parameter derived from the ratio of the jet concentration fluctuations to the fully mixed concentration, and (2) probability density functions of the concentration distributions. Mixing rate was measured for 45 degree slant slot and round orifice injectors.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-187141 , E-7708 , NAS 1.26:187141
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Experimental Evaluation of a Low Emissions High Performance Duct Burner for Variable Cycle Engines (VCE) (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An evaluation was conducted with a three stage Vorbix duct burner to determine the performance and emissions characteristics of the concept and to refine the configuration to provide acceptable durability and operational characteristics for its use in the variable cycle engine (VCE) testbed program. The tests were conducted at representative takeoff, transonic climb, and supersonic cruise inlet conditions for the VSCE-502B study engine. The test stand, the emissions sampling and analysis equipment, and the supporting flow visualization rigs are described. The performance parameters including the fuel-air ratio, the combustion efficiency/exit temperature, thrust efficiency, and gaseous emissions calculations are defined. The test procedures are reviewed and the results are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-159694 , PWA-5513-32A
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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