Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Microstructure. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Composition and Properties of Hot-Pressed SiC-AIN Solid Solutions

Abstract: High-density SiC-AIN compositions were fabricated from powder mixtures by hot-pressing in the 1700° to 2300°C temperature range. At 2100°C, a 2H solid solution was found from =35 to 100 wt% AlN. The single-phase solid solution samples had steep composition gradients of >10%/μm within the grains. Lattice parameters closely followed Vegard's law. For compositions with <35% AIN, multiphase assemblages were found. Increasing grain size was observed for increasing firing temperature for SiC and AIN. Grain size of the solid solutions was significantly smaller than for SiC or AIN fired to the same temperature. Microhardness values decreased linearly in the solid solution region with increasing AIN content. Flexural strengths of SiC and AIN decreased with increasing firing temperature and increasing grain size. The strengths of SiC, AIN, and the solid solutions were low for materials hot-pressed at 2100°C.

Stability limits of cavity-stabilized flames in supersonic flow

Abstract: Experiments were performed to examine the stability of hydrocarbon-fueled flames in cavity flameholders in supersonic airflows. Methane and ethylene were burned in two different cavity configurations having aft walls ramped at 22.5° and 90°. Air stagnation temperatures were 590 K at Mach 2 and 640 K at Mach 3. Lean blowout limits showed dependence on the air mass flowrates, cavity geometry, fuel injection scheme, Mach number, and fuel type. Large differences were noted between cavity floor and cavity ramp injection schemes. Visual observations, planar laser-induced fluorescence of nitric oxide, and shadowgraph imaging were used to investigate these phenomena. Cavity ramp injection provided better performance near the lean blowout limit, whereas injection from the cavity floor resulted in more stable flames near the rich limit. Ethylene flames have a wider range of stable operations than methane in all conditions. Lean blowout limits were not significantly different between the Mach 2 and Mach 3 cases at the lean limit; however, variation in Mach number had a measurable effect near the rich limit. Fuel flowrates at ignition were much greater than the lean blowout limit, but showed similar dependence on air mass flowrate.

Combustion enhancement via stabilized piecewise nonequilibrium gliding arc plasma discharge

Abstract: A new piecewise nonequilibrium gliding arc plasma discharge integrated with a counterflow flame burner was developed and validated to study the effect of a plasma discharge on the combustion enhancement of methane-air diffusion flames. The results showed that the new system provided a well-defined flame geometry for the understanding of the basic mechanism of the plasma-flame interaction. It was shown that with a plasma discharge of the airstream, up to a 220% increase in the extinction strain rate was possible at low-power inputs. The impacts of thermal and nonthermal mechanisms on the combustion enhancement was examined by direct comparison of measured temperature profiles via Rayleigh scattering thermometry and OH number density profiles via planar laser-induced fluorescence (calibrated with absorption) with detailed numerical simulations at elevated air temperatures and radical addition. It was shown that the predicted extinction limits and temperature and OH distributions of the diffusion flames, with only an increase in air temperature, agreed well with the experimental results. These results suggested that the effect of a stabilized piecewise nonequilibrium gliding arc plasma discharge of air at low air temperatures on a diffusion flame was dominated by thermal effects.