The 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. ( Dagaut P. Ristori A. Frassoldati A. Raravelli T. Dayma G. Ranzi E. Dagaut P. Ristori A. Frassoldati A. Raravelli T. Dayma G. Ranzi E. 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.

No abstract

No abstract

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.