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Vedha Nayagam
Glenn Research Center
54Publications
13H-index
543Citations
Publications 54
Newest
#1Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
#2Vedha Nayagam (Case Western Reserve University)H-Index: 13
Last.Vedha Nayagam (Case Western Reserve University)H-Index: 4
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#1Vedha NayagamH-Index: 13
#2Daniel L. DietrichH-Index: 13
Last.Forman A. WilliamsH-Index: 48
view all 3 authors...
Abstract A scaling analysis of burner-supported spherical-diffusion-flame extinction brought about by radiative heat loss is presented. The results are compared against earlier microgravity experimental data and unsteady numerical computations with detailed chemistry available in the literature, for normal and inverse flames. The flame diameter at extinction is shown to correlate well with the present model, in which the extinction radius scales with one-third power of gas flow rate times reacta...
#1Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
#2Vedha Nayagam (Case Western Reserve University)H-Index: 13
Last.Vedha Nayagam (Case Western Reserve University)H-Index: 4
view all 2 authors...
#1Vedha Nayagam (Case Western Reserve University)H-Index: 13
#2Vedha Nayagam (Case Western Reserve University)H-Index: 4
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
view all 3 authors...
Abstract Millimeter-size fuel droplets burning in microgravity show substantial thermal expansion at earlier times in their burning history. Here, we develop a simple model that accounts for thermal expansion of the liquid fuel and compare it against experimental measurements. The results show that excellent agreement with measured droplet-diameter histories throughout the hot-flame period of combustion is obtained when the effect of thermal expansion is included.
#1Vedha Nayagam (Case Western Reserve University)H-Index: 4
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
view all 4 authors...
Abstract Experimental observations are presented concerning radiative extinction of large n-alkane droplets in diluent-substituted environments at moderately varied pressures in microgravity onboard the International Space Station. The fuels considered are n-heptane, n-octane, and n-decane with carbon dioxide, helium, and xenon used as inerts, replacing nitrogen as diluents at varying amounts. It is shown that a simple scaling analysis, based on the assumptions that radiative extinction occurs w...
#1Vedha Nayagam (Case Western Reserve University)H-Index: 4
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
view all 3 authors...
Abstract Droplet combustion experiments carried out onboard the International Space Station, using pure fuels and fuel mixtures, have shown that quasi-steady burning can be sustained by a non-traditional flame configuration, namely a “cool flame” burning in the “partial-burning” regime where both fuel and oxygen leak through the low-temperature-controlled flame-sheet. Recent experiments involving large, bi-component fuel ( n -decane and hexanol, 50/50 by volume) droplets at elevated pressures sh...
#1Vedha Nayagam (Case Western Reserve University)H-Index: 4
#2Daniel L. Dietrich (Glenn Research Center)H-Index: 13
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
view all 3 authors...
A Burke–Schumann description of three different regimes of combustion of a fuel droplet in an oxidising atmosphere, namely the premixed-flame regime, the partial-burning regime and the diffusion-flame regime, is presented by treating the fuel and oxygen leakage fractions through the flame as known parameters. The analysis shows that the burning-rate constant, the flame-standoff ratio, and the flame temperature in these regimes can be obtained from the classical droplet-burning results by suitabl...
#1Daniel L. Dietrich (Glenn Research Center)H-Index: 13
#2R. CalabriaH-Index: 1
Last.Forman A. Williams (UCSD: University of California, San Diego)H-Index: 48
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ABSTRACTThis article presents the results of experiments conducted aboard the International Space Station involving the combustion of large bi-component droplets of decane and hexanol (50/50 by volume) in air ambients with ambient pressures between 0.05 and 0.30 MPa. The experiments showed the presence of sustained low-temperature or cool-flame burning following radiative extinction of large droplets at ambient pressures greater than or equal to 0.10 MPa. The droplet diameters at cool-flame exti...
#1K. Seshadri (UCSD: University of California, San Diego)H-Index: 28
#2N. Peters (RWTH Aachen University)H-Index: 56
Last.Guenter Paczko (RWTH Aachen University)H-Index: 2
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A skeletal chemical-kinetic mechanism for n-heptane cool flames is simplified to the maximum extent possible by introduction of steady-state approximations for intermediaries, following procedures employed previously in addressing two-stage ignition. A pair of ordinary differential equations in mixture-fraction space is thereby obtained, describing the quasi-steady structures of the temperature and heptylketohydroperoxide fields. Application of activation-energy asymptotics for the partial-burni...
#1Vedha NayagamH-Index: 13
#2Daniel L. DietrichH-Index: 13
Last.Forman A. WilliamsH-Index: 48
view all 3 authors...
A simplified model for droplet combustion in the partial-burning regime is applied to the cool-flame regime observed in droplet-burning experiments performed in the International Space Station with normal-alkanes fuels resulting in expressions for the quasi-steady droplet burning rate and for the flame standoff ratio. The simplified predictions are found to produce reasonable agreement with the experimentally measured values of burning-rate constants but not with their apparent dependencies on p...
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