autoignition of tetralin, a naphthenic and aromatic hydrocarbon found
in jet and diesel fuels and a hydrogen donor with potential as an
endothermic fuel and for use in heavy crude oil upgrading processes,
has been studied in shock-tube experiments. Measurements of ignition
delay times for tetralin/air mixtures at equivalence ratios of 0.5
and 1.0 were made in stationary reflected shock-heated gases at nominal
pressures around 13 and 37–39 bar and temperatures from 978
to 1277 K, conditions relevant to practical combustion devices, such
as internal combustion engines and jet engine gas turbine combustors.
The dependence of the ignition delay time upon the temperature, equivalence
ratio, and pressure in the examined condition space can be described
with a simple four-parameter correlation. Measurements compared the
recent kinetic model by Dagaut et al. (
Energy Fuels20132715761585) to good a priori agreement between
the model and experiment. Comparisons between the present autoignition
measurements for tetralin and previous results for decalin, toluene,
and cyclohexane illustrate the relative reactivity for compounds containing
aromatic, naphthenic, and combined structures.
Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant droplets of ethanol laden with varying (0–3%) weight percentages of 40–60 nm aluminum nanoparticles (nAl). High-resolution droplet images were collected as a function of time for the determination of D-square law evaporation rates. Results show an asymptotic decrease in droplet evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol, a reduction greater than can be explained by reduction in the vapor pressure of an ideal nanofluid mixture by Raoult’s law. It is hypothesized that the reduction in evaporation rate could be due to two phenomena: 1) the reduction in the ethanol volume fraction available for evaporation due to an interfacial layer on the immersed nanoparticle surface and 2) the aggregation of nanoparticles within the droplet and at the droplet surface, reducing the liquid diffusion rate to the surface and the liquid volume fraction at the surface available for evaporation.
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