여재익 교수

We compare two-dimensional model results with measurements for the thermal, chemical, and mechanical behavior in a thermal explosion experiment. Confined high explosives (HEs) are heated at a rate of 1°C∕h until an explosion is observed. The heating, ignition, and deflagration phases are modeled using an Arbitrarily Lagrangian-Eulerian code (ALE3D) that can handle a wide range of time scales that vary from a structural to a dynamic hydrotime scale. During the preignition phase, quasistatic mecha

In recent times, there is a growing interest in the development of electrically controlled solid propellants (ECSPs) because they offer various advantages over conventional solid propellants. However, the fundamental understanding on the complex reaction mechanism of decomposition/combustion of these ECSPs is still limited. The present study attempts to expand the knowledge on thermal decomposition mechanisms of ECSPs based on lithium perchlorate (LP) oxidizer and poly vinyl alcohol (PVA) binder

The interaction of a high-power pulsed-laser beam with metal targets in air from a 1.06 μm, 5 ns, 3 J/pulse, Nd:YAG pulsed laser is investigated together with hydrodynamic theories of laser-supported blast wave and multimaterial reactive Euler equations. The high-speed blast wave generated by the laser ablation of metal reaches a maximum velocity of several thousand meters per second. The apparently similar flow conditions to those of reactive shock wave allow one to apply the equations of motio

Simultaneous laser ignition and spectroscopy is a scheme that enables rapid determination of the local equivalence ratio and condensed fuel concentration during a reaction in a two phase spray flame. In parallel with laser ignition, the equivalence ratio and droplet characteristics such as the concentration, size, and distribution of spray combustion are simultaneously obtained for a feedback control system. The plasma characteristics of fuel droplets are evaluated initially by shadowgraph, and

In the numerical simulation of transient reacting flow, standard explicit calculation is prohibitively expensive because of the small time steps needed to address the stiffness of a governing differential system. To circumvent this, new hybrid implicit‐explicit methods proposed treat the stiffness, whereas the underlying time-step control is governed by the Courant stability criterion. Because the coefficients of both explicit and implicit operations are entirely determined by solving the necess

We present a numerical investigation of gaseous deflagration-to-detonation transition (DDT) triggered by a shock in a multi-bend geometry. The ethylene-air mixture filled rigid tube with obstacles is considered for understanding the effects of complex confinement and initial flame size on DDT. Our calculations show generation of hot spots by flame and strong shock interactions, and flame propagation is either restrained or accelerated due to the wall obstacles of both straight and bent tubes. Th

Two-dimensional mapping of the laser-induced breakdown spectroscopy (LIBS) signal of chemical species information in liquefied petroleum gas (LPG) and electrolytic oxy-hydrogen (EOH) flames was performed with in situ flame diagnostics. Base LIBS signals averaged from measurements at wavelengths of 320 nm to 350 nm describe the density information of a flame. The CN LIBS signal provides the concentration of fuel, while the H/O signal represents the fuel/air equivalence ratio. Here, we demonstrate

Ultrahigh capacity lithium-ion batteries (LIBs) with prudent safety measures are key to future transportation. The undesirable thermal events such as thermal runaway (TR) in LIBs can pose a direct risk to battery life and the consumers. In the present study, a set of new TR criteria are established by closely inspecting the relation between the rate of heat generation and dissipation to anticipate the TR at an early stage. From the proposed criteria, three alarming temperatures prior to TR are i