Hyungsub Sim

This study investigates the low- and high-temperature ignition and combustion processes in a high-pressure spray flame of n-dodecane using simultaneous 50-kHz formaldehyde (HCHO) planar laser-induced fluorescence (PLIF) and 100-kHz schlieren imaging. The PLIF measurements were facilitated through the use of a pulse-burst-mode Nd:YAG laser, producing a 355-nm pulse-train with 300 pulses at 70 mJ/pulse, separated by 20-µs, in a 6-ms burst. The high-speed HCHO PLIF signal was imaged using a non-int

The present experiments focused on the response of burning gaseous fuel jets to prescribed transverse acoustic excitation as a means of exploring the coupling of reactive, acoustic, and flow processes relevant to combustion instabilities. Single reactive methane microjets were exposed to transverse resonant standing wave disturbances within an acoustic waveguide for which a range of amplitudes of excitation were applied. Temporal flame response to acoustic excitation was studied via simultaneous

The effect of nanoscale energetic aluminum (nAl) and inert silicon dioxide (nSiO2) particulate additives on ethanol droplet combustion was studied under atmospheric conditions. Three different types of droplet experiments were performed to study the influence of the experiment itself on combustion behavior. Simultaneous visible and intensified ultraviolet (UV) images were taken to determine the burning rate constant (K) as well as flame dynamics via OH* chemiluminescence imaging. The addition of

This experimental study explores the effects of acoustic excitation on burning droplets of liquid ethanol loaded with reactive aluminum nanoparticles (nAl). Continuously fed fuel droplet combustion and flame extinction (blowout) experiments were conducted in the vicinity of a pressure node (or velocity antinode) created in a closed acoustic waveguide, with a range of applied resonant forcing frequencies, pressure or velocity perturbation amplitudes, and particle loading concentrations. Simultane

The objective of this study is to numerically investigate the electron-phonon interactions and the nonequilibrium energy transfer in metal thin films irradiated by ultrashort pulse train lasers. In particular, the temporal and spatial variations in the optical properties during laser irradiation are discussed; the influence of the number of pulses per train and the pulse separation time are also examined. The present study uses the well-established two-temperature model to describe laser-solid i

Experiments and simulations were used to demonstrate that decorating functionalized graphene sheets (FGSs) with platinum nanoparticles (Pt@FGS) stabilized these particles. Addition of these particles to liquid hydrocarbon fuels was observed to significantly affect decomposition under supercritical conditions at a pressure of 4.75 MPa and temperatures from 753 to 803 K. The suspension of only 50 ppmw Pt@FGS in the fuel (equivalent to adding 10 ppmw Pt) enhanced fuel conversion rates (by up to 24%

As a particulate fuel additive, functionalized graphene sheets (FGS), with and without the decoration of nanoparticles, provide a means to form stable colloids with liquid hydrocarbons, act as in situ catalysts, and prevent attached nanoparticles from agglomerating or sintering during heating. Recent pyrolysis experiments and simulations have shown the synergetic effect of Pt and FGS structures accelerating fuel conversion and hydrogen formation. In this paper, the role of graphene-based additiv

Nonequilibrium energy transport and optical characteristics in thin gold film structures irradiated by a femtosecond pulse laser are examined numerically. With the use of a two-temperature model, the quantum effect is considered to determine various thermo-optical properties such as electron heat capacity, electron thermal conductivity, collision frequencies, reflectivity, and absorption rates. As a result, estimation on the electron temperature considering the quantum effect is in better agreem

Aluminum nanoparticles (ANPs) have attracted significant attention for combustion applications owing to their high energy density and reactivity. Surface coating has been proposed to overcome the limitations of ANPs, which are sintering and oxidizing at moderate temperatures; however, the thermal behavior of surface-coated ANPs remains unclear. In this study, reactive molecular dynamics simulations of ANP sintering and oxidation were performed to investigate the effectiveness of hydrocarbon surf