Temporal Evolution of Heavy-Ion Spectra in Solar Energetic Particle Events

Solar energetic particles (SEPs) are released into the heliosphere by solar flares and coronal mass ejections (CMEs). They are mostly protons, with smaller amounts of heavy ions from helium to iron, and lesser amounts of species heavier than iron. The spectra of heavy ions have been previously studied mostly by using the fluence of the particles in an event-integrated spectrum in a small number of spectral snapshots. In this article, we ana- lyze the temporal evolution of the heavy-ion spectra using two large SEP events (27 January 2012 and 7 January 2014) from the Solar TErrestrial Relations Observatory (STEREO) era using Advanced Composition Explorer (ACE) Solar Isotope Spectrometer (SIS) and Ultra Low Energy Isotope Spectrometer (ULEIS), Energetic Particles: Acceleration, Composition and Transport (EPACT) onboard Wind, and the STEREO-A (Ahead) and -B (Behind) Low- Energy Telescope (LET) and Suprathermal Ion Telescope (SIT) instruments, taking a large number of snapshots covering the temporal evolution of the event. We find large differences in the spectra of the ions after the main flux enhancement in terms of the grouping of similar species, but also in terms of the location of the instruments. Although it is somewhat less no- ticeable than in the case of the temporal evolution of protons (Doran and Dalla, Solar Phys. 291, 2071, 2016), we observe a wave-like pattern travelling through the heavy ion spectra from the highest energies to the lowest, creating an “arch” structure that later straightens into a power law after 18 to 24 hours

Combustor with fuel preparation chambers

An annular combustor having fuel preparation chambers mounted in the dome of the combustor. The fuel preparation chamber comprises an annular wall extending axially from an inlet to an exit that defines a mixing chamber. Mounted to the inlet are an air swirler and a fuel atomizer. The air swirler provides swirled air to the mixing chamber while the atomizer provides a fuel spray. On the downstream side of the exit, the fuel preparation chamber has an inwardly extending conical wall that compresses the swirling mixture of fuel and air exiting the mixing chamber

Experimental Studies of Cavity and Core Flow Interactions With Application to Ultra-Compact Combustors

Reducing the weight and decreasing pressure losses of aviation gas turbine engines improves the thrust-to-weight ratio and improves efficiency. In ultra-compact combustors (UCC), engine length is reduced and pressure losses are decreased by merging a combustor with adjacent components using a systems engineering approach. High-pressure turbine inlet vanes can be placed in a combustor to form a UCC. In this work, experiments were performed to understand the performance and associated physics within a UCC. Experiments were performed using a combustor operating at pressures in the range of 520–1030 kPa (75–150 psia) and inlet temperature equal to 480–620 K (865 R–1120 R). The primary reaction zone is in a single trapped-vortex cavity where the equivalence ratio was varied from 0.7 to 1.8. Combustion efficiencies and NO[subscript x] emissions were measured and exit temperature profiles were obtained for various air loadings, cavity equivalence ratios, and configurations with and without representative turbine inlet vanes. A combined diffuser-flameholder (CDF) was used to study the interaction of cavity and core flows. Discrete jets of air immediately above the cavity result in the highest combustion efficiencies. The air jets reinforce the vortex structure within the cavity, as confirmed through coherent structure velocimetry of high-speed images. The combustor exit temperature profile is peaked away from the cavity when a CDF is used. Testing of a CDF with vanes showed that combustion efficiencies greater than 99.5% are possible for 0.8 ≤ Φ[subscript cavity] ≤ 1.8. Temperature profiles at the exit of the UCC with vanes agreed within 10% of the average value. Exit-averaged emission indices of NO[subscript x] ranged from 3.5 to 6.5 g/kg[subscript fuel] for all test conditions. Increasing the air loading enabled greater mass flow rates of fuel with equivalent combustion efficiencies. This corresponds to increased vortex strength within the cavity due to the greater momentum of the air driver jets

Model validation image data for breakup of a liquid jet in crossflow: part I

We have applied three different imaging diagnostics: particle imaging velocimetry, high-speed shadowgraphy, and ballistic imaging, to observe the breakup of a liquid jet in a crossflow of air under a variety of conditions. The experimental system was designed to provide well-controlled conditions with minimal amounts of turbulence in the liquid jet and the gaseous crossflow. A variety of Weber numbers and momentum flux ratios were studied in order to provide a sizable data set for the validation of computational models. This paper briefly describes the three spray imaging techniques, outlines the results obtained to-date, and tabulates image statistics for each of ten spray conditions at varying distances from the spray nozzle orifice. The end result is a first installment in what will become a comprehensive model validation data set for jets in crossflow for use by computational fluid dynamics modelers

FLAME STRUCTURE OF VITIATED FUEL-RICH INVERSE DIFFUSION FLAMES IN A CROSS-FLOW (Postprint) Combustion Branch Turbine Engine Division Spectral Energies LLC STINFO COPY AIR FORCE RESEARCH LABORATORY PROPULSION DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information AFRL/RZTC SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-RZ-WP-TP-2011-2163 DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited. ABSTRACT Fuel-rich streaks or dissociated combustion products exiting from gas turbine combustors may react with jets of turbine vane cooling air. These fuel-rich vitiated inverse diffusion flames can potentially cause structural failure of turbine vanes due to the excessive heat fluxes. In this study OH planar laser induced fluorescence measurements are conducted in fuel-rich vitiated flows advecting over a flat plate with a row of cooling holes normal to the surface. Vitiated conditions are generated by burning propane at equivalence ratios between 1.1 and 1.4 in a well-stirred reactor located upstream of the test section. The structures of the flames (i.e., spatially-resolved species measurements) are compared for different equivalence ratios and blowing ratios. It is observed that the flames generated by the cooling air are inherently unsteady, with the standard deviation of the flame tip location varying by as much as 35%. The distance downstream of the slot where the flame tip was observed varies by 20% or less (with respect to the average) for a factor of 20 increase in the blowing ratio. The separation between the flame and the wall is similar for blowing ratios between 1 and 5, but increases for a blowing ratio of 10. Changing the equivalence ratio of the vitiated flow has little effect on the location where flames are observed. Fuel-rich streaks or dissociated combustion products exiting from gas turbine combustors may react with jets of turbine vane cooling air. These fuel-rich vitiated inverse diffusion flames can potentially cause structural failure of turbine vanes due to the excessive heat fluxes. In this study OH planar laser induced fluorescence measurements are conducted in fuel-rich vitiated flows advecting over a flat plate with a row of cooling holes normal to the surface. Vitiated conditions are generated by burning propane at equivalence ratios between 1.1 and 1.4 in a well-stirred reactor located upstream of the test section. The structures of the flames (i.e. spatially-resolved species measurements) are compared for different equivalence ratios and blowing ratios. It is observed that the flames generated by the cooling air are inherently unsteady, with the standard deviation of the flame tip location varying by as much as 35%. The distance downstream of the slot where the flame tip was observed varies by 20% or less (with respect to the average) for a factor of 20 increase in the blowing ratio. The separation between the flame and the wall is similar for blowing ratios between 1 and 5, but increases for a blowing ratio of 10. Changing the equivalence ratio of the vitiated flow has little effect on the location where flames are observed