Lydia Wermer

Giovanni DiCristina

Jinyu Yang

Serang Kwon

Nozomu Kato

Haechang Jung

Daegi Yeom

Beomhui Lee

Jieun Kang

Jeongje Park

Juwon Park

Sooyeon Lee

Jeongah Lim

Jincheol Park

Gunho Lee

Jiwan Seo

Changbin Oh

Chanwoo Lee

Yuechao (Wolcho) Wang

Kyeongchan Choi

Sumin Lee

Influence of wall heat loss on emission characteristics of NH3/CH4/ air premixed flame in a model gas-turbine combustor

Life cycle assessment and techno-economic analysis of naphtha cracking electrification using plasma for carbon neutrality

Optimizing global reaction models for ammonia combustion using Genetic Algorithms

Developing a Surrogate n-Hexane Pyrolysis Reactor Model through Artificial Neural Networks Learning

Plasma-modified biochar for energy and environmental sustainability

Shortened​ ​Flowfield​ ​Design​ ​for​ ​Streamline-Traced​ ​Intakes

Advances in battery thermal management for electric vehicles: A comprehensive review of hybrid PCM-metal foam and immersion cooling technologies

Energy, exergy, and exergoeconomic analyses of plastic waste-to-energy integrated gasification combined cycles with heat recovery at a gasifier

Thermodynamic evaluation of integrated plasma gasification combined cycle with plastic waste feedstock

Developing a versatile detail mechanism for NH3 combustion

Rectangular-to-elliptical shape transition intakes with various leading-edge for performance enhancement

Off-design characteristics of a scoop-type streamline-tracing scramjet inlet

Atmospheric-pressure microwave plasma reforming of ethane-carbon dioxide mixtures

Estimation of the Global Equivalence Ratio of a Swirl Combustor from a Small Number of Absorption Spectra Using Machine Learning

Estimation​ ​of​ ​forest​ ​biomass​ ​from​ ​aerial​ ​photographs​ ​using​ ​Mask​ ​R-CNN​ ​and​ ​Bayesian​ ​regression

Machine learning-based prediction fo swirl combustor operation from flame imaging

Nonviable carbon neutrality with plastic waste-to-energy

Boundary layer suction timing and location effects on unstarting flows in a model scramjet

Simultaneous measurement of carbon emission and gas temperature via laser-induced breakdown spectroscopy coupled with machine learning

Aerial imaging-based fuel information acquisition for wildfire research in Northeastern South Korea

Feasibility of non-thermal plasma gasification for a waste-to-energy power plant

Spatiotemporally resolved measurements of electric field around a piezoelectric transformer using electric-field induced second harmonic (E-FISH) generation

Design and implementation of a portable, large-scale wind tunnel for wildfire research

Flame spread predictions using an empirical B-number model and stagnation point flow

Fast-acting boundary-layer suction control of unstarting flows in an ethylene-fueled dual-mode scramjet

Forced convection fire spread along wooden dowel array

Flame spread behavior characterization of discrete fuel array under a forced flow

Flame dynamics under various backpressures in a model scramjet with and without a cavity flameholder

Spark and flame kernel interaction with dual-pulse laser-induced spark ignition in a lean premixed methane–air flow

Hand-generated piezoelectric mechanical-to-electrical energy conversion plasma

Fast-acting boundary-layer suction to control unstarting and unstarted flows

Time-resolved characterization of a free plasma jet formed off the surface of a piezoelectric crystal

Plasma and flow induced by single-and dual-pulse laser-induced breakdown in stationary air

Visualization of scoop inlet-circular isolator flows

Ignition enhancement by dual-pulse laser-induced spark ignition in a lean premixed methane-air flow

Residence time distribution measurements for model flows based on laser-induced breakdown spectroscopy

Laser-induced breakdown thermometry via time-of-arrival measurements of associated acoustic waves

Unstart phenomena induced by flow choking in scramjet inlet-isolators

Spatiotemporal evolution of the plasma from dual-pulsed laser-induced breakdown in atmospheric air

Optical emission spectroscopic studies on atmospheric electrodeless microwave plasma in carbon dioxide-hydrogen mixture

Formation of nitrogen oxides from atmospheric electrodeless microwave plasmas in nitrogen–oxygen mixtures

Experimental and numerical studies on carbon dioxide decomposition in atmospheric electrodeless microwave plasmas

Flow Field and Scalar Measurements in a Series of Turbulent Partially-Premixed Dimethyl Ether/Air Jet Flames

Dual-pulse laser-induced spark ignition and flame propagation of a methane diffusion jet flame

Unstart phenomena induced by mass addition and heat release in a model scramjet

Schlieren imaging investigation of successive laser-induced breakdowns in atmospheric-pressure air

Nanosecond-pulsed discharge plasma splitting of carbon dioxide

Imaging measurements and LES-CMC modeling of a partially-premixed turbulent Dimethyl Ether/air jet flame

Experiments and simulations of one atmospheric lossy dielectric barrier Townsend discharge

A study of laser-induced breakdown plasma using successive laser pulses in atmospheric pressure air and premixed ethane-air mixtures

Dielectric barrier discharge-induced vortex generation with discharge-actuated boundary layer bleed

A study of flow induced by laser induced breakdown-enhanced dielectric barrier discharges in air

Plasma Actuator Control of a Lifted Ethane Turbulent Jet Diffusion Flame

Studies on the stability limit extension of premixed and jet diffusion flames of methane, ethane, and propane using nanosecond repetitive pulsed discharge plasmas

Surface discharge plasma actuator driven by a pulsed 13.56 MHz-5 kHz voltage waveform

Induced flow and optical emission generated by a pulsed 13.56 MHz-5 kHz plasma actuator

Dielectric barrier discharge induced boundary layer suction

The manipulation of an unstarting supersonic flow by plasma actuator

Visualizing supersonic inlet duct unstart using planar laser Rayleigh scattering

The influence of boundary layers on supersonic inlet flow unstart induced by mass injection

Dielectric barrier discharge control of a turbulent boundary layer in a supersonic flow

Plasma assisted flame ignition of supersonic flows over a flat wall

Flame liftoff height dependence on geometrically modified bluff bodies in a vitiated flow

Seong Kyun Im

A review of recent research outcomes in downstream flow choking-driven unstart is presented. Unstart is a flow phenomenon at the inlet that severely reduces the air mass flow rate through the engine, causing a loss of thrust and considerable transient mechanical loading. Therefore, unstart in a scramjet engine crucially affects the design and the operation range of hypersonic vehicles. Downstream flow choking is known to be one of the major mechanisms inducing inlet unstart, as confirmed by recent scramjet-powered flight tests. The current paper examines recent research progress in identifying flow choking mechanisms that trigger unstart. Three different flow choking mechanisms are discussed: flow blockage, mass addition, and heat release from combustion reactions. Current research outcomes on the characteristic of unstarting flows, such as transient and quasi-steady motions, are reviewed for each flow …

A nanosecond pulsed plasma discharge located between two fuel jets is used to ignite and hold jet flames in supersonic crossflows, without the use of additional devices (e.g., cavities or backsteps) for flame holding. The fuel injection nozzles and discharge electrodes are mounted flush with the surface of the flat wall adjacent to the freestream flow. The nonequilibrium plasma is produced by repetitive pulses of 15kV peak voltage, 10ns pulse width and 50kHz repetition rate. Sonic or subsonic fuel jets (hydrogen and ethylene) are injected into a pure oxygen freestream of Mach numbers Ma=1.7–2.4. The shockwave/flow structures induced by the fuel jets and the OH radical distribution resulting from combustion are characterized by Schlieren photography and planar laser induced fluorescence imaging, respectively. A configuration combining an upstream subsonic oblique jet and a downstream sonic transverse jet is …

A transverse jet is injected into a supersonic model inlet flow to induce unstart. Planar laser Rayleigh scattering from condensed CO 2 particles is used to visualize flow dynamics during the unstart process, while in some cases, wall pressure traces are simultaneously recorded. Studies conducted over a range of inlet configurations reveal that the presence of turbulent wall boundary layers strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers in asymmetric wall boundary layer conditions prompt the formation of unstart shocks; in symmetric boundary conditions lead to the propagation of pseudo-shocks; and in both cases facilitate fast inlet unstart, when compared with thin, laminar boundary layers. Incident shockwaves and associated reflections are found to affect the speed of pressure disturbances. These disturbances, which induce boundary layer separation, are found to …

The unstart phenomena in a model scramjet with a free stream Mach number of 4.5 were investigated at an arc-heated hypersonic wind tunnel. High-speed schlieren imaging and high resonance frequency pressure measurements were used to capture the flow features during the unstart process. Three unstart conditions were tested: (i) a low-enthalpy free stream with mass loading, (ii) a high-enthalpy free stream with mass loading and (iii) a high-enthalpy free stream with mass loading and heat release. It was revealed that the unstart threshold and the time from the onset to the completion of unstart depended strongly on the mass loading rate and the heat exchange. The negative heat addition (cooling) significantly increased the threshold of mass flow rate triggering unstart. The decrement of the mass flow rate threshold for unstart was observed in the presence of heat release by combustion. The observed …

Planar laser Rayleigh scattering (PLRS) from condensed CO 2 particles is used to visualize flow structure in a Mach 5 wind tunnel undergoing unstart. Detailed flow features such as laminar/turbulent boundary layers and shockwaves are readily illustrated by the technique. A downstream transverse air jet, inducing flow unchoking downstream of the jet, is injected into the free stream flow of the tunnel, resulting in tunnel unstart. Time sequential PLRS images reveal that the boundary layer growth/separation on a surface with a thick turbulent boundary layer, initiated by the jet injection, propagates upstream and produces an oblique unstart shock. The tunnel unstarts upon the arrival of the shock at the inlet. In contrast, earlier flow separation on the opposite surface, initially supporting a thin laminar boundary layer, is observed when a jet induced bow shock strikes that surface. The resulting disturbance to this boundary …

One of the major challenges currently facing electric vehicles (EVs) is the effective thermal management of their battery packs, which significantly impacts both battery performance and longevity. Temperature control is a critical parameter for ensuring efficient battery thermal management systems (BTMS), making the development of effective real-time heat dissipation technologies essential. Presently, most EVs utilize indirect liquid-cooling systems, which effectively reduce battery temperatures but are limited by issues such as high pumping power requirements and non-uniform temperature distribution, necessitating further research and optimization. This study examines the limitations of conventional liquid and air-cooling approaches while exploring the development potential of phase change materials (PCM) enhanced with metal foam, integrated with liquid-cooling as a promising alternative. Additionally, the …

We demonstrate effective manipulation of a turbulent boundary layer at Mach 4.7 conditions using a surface dielectric barrier discharge (DBD) actuator. The freestream conditions of low static pressure (1 kPa) and temperature (60 K) are conducive to the visualization of flow features using Rayleigh scattering from condensed CO 2 particles. The boundary layer thinning is observed when spanwise momentum is induced by the low power (6.8 W), low frequency (28 kHz) single actuator pair oriented parallel to the freestream flow.

This paper reports on the study of repetitive nanosecond-pulsed discharge splitting of carbon dioxide (CO 2 ) for the production of CO. Gas chromatography is used to analyze the composition of the reformed gas when CO 2 is exposed to high-voltage (15 kV) very short (10 ns) electrical discharges that deposit as much as 0.4 mJ of energy at a rate of 30 kHz. Conversion rate and energy efficiency are obtained while the discharge pressure is varied between 2.4 and 5.1 atm. At the tested conditions, the maximum conversion rate and energy efficiency are found to be 7.3% and 11.5%, respectively. The energy efficiency drops slightly with increased pressure because of the decreased electric field and electron energy per molecule. An energy balance analysis of a set of CO 2 plasma reactions reveals that the dominant dissociation pathway under these conditions passes through the excitation of CO 2 (10.5 eV) followed by …

Two successive focused laser pulses are employed to experimentally simulate laser-induced breakdown plasmas at high repetition rates. We find that energy absorption of the second laser pulse by the plasma produced by the first laser pulse is enhanced slightly when the time interval between the pulses is shorter than several tens of nanoseconds but falls to almost zero when the time interval is between a few hundreds of nanoseconds and several tens of microseconds. This behavior is attributed to gas heating by the first breakdown event. In premixed ethane–air mixtures, we identify another strong reduction in the second laser pulse absorption when this pulse coincides with the heat released by combustion, typically milliseconds after the first laser pulse. The fuel–air equivalence ratio ( ϕ ) and base flow speed are also varied in this study. The results show that the window of reduced absorption coinciding with …

Successive laser-induced breakdowns in atmospheric pressure air and premixed ethane–air mixtures

This paper examines the stabilization of premixed and jet diffusion flames of methane, ethane, and propane by nanosecond repetitive pulsed plasma discharges. Combustion products are measured using gas chromatography while laser-induced breakdown spectroscopy (LIBS) is used to characterize the local equivalence ratios. We find that in premixed flames, although plasma-assisted flame holding takes place under fuel-lean conditions, propagation of combustion occurs at/or above the known lean flammability limits. In jet diffusion flames, the flames are found to be anchored best to the discharge at jet speeds that are much higher than the normal blow-off speed when the discharge is placed where the local fuel–air equivalence ratio is in a limited flammable regime.

Incineration, pyrolysis, and gasification during plastic waste treatment are inevitable to reduce the volume of landfilled plastic waste and recover energy; however, they cause severe carbon emissions. We show that the current practices of plastic waste-to-energy will significantly impact carbon neutrality. Various energy recovery systems, such as combined power cycles and fuel cells, were modeled to evaluate the power generated and CO2 emitted from treating the current and projected plastic waste by 2050. The CO2 emissions from plastic waste-to-energy systems are higher than those from current fossil fuel-based power systems per unit of power generated, even after considering the contribution of carbon capture and storage. Power generation using plastic waste will significantly increase by 2050, and therefore, we suggest technologies required for achieving carbon neutrality.

The manipulation of an unstarting supersonic flow is demonstrated using a dielectric barrier discharge (DBD). Experiments are carried out in a Mach 4.7 model inlet flow. Flow features, such as boundary layers and shockwaves at low freestream static pressure (1 kPa) and temperature (60 K) are visualized with Rayleigh scattering from condensed CO 2 particles. Flow unstart, initiated by mass injection, is studied for three model inlet flow configurations, distinguished by the initial conditions (untripped or tripped, plasma actuated or not) of the boundary layers. Unstart in the presence of thick, tripped boundary layers is characterized by the formation of an oblique unstart shock just upstream of a separating and propagating boundary layer. The presence of plasma actuation of this tripped boundary layer seems to arrest the boundary layer separation and leads to the formation of a quasi-stationary pseudo-shock …

An experimental investigation was performed to study the ignition and flame propagation behaviors of a methane diffusion jet flame (Re = 5500) when dual pulse laser-induced spark discharges were introduced in a mixing layer. Time intervals ( dt ) of 50 ns, 100 µs, and 600 µs between two laser pulses were tested, and the results were compared to a single pulse discharge case with the same total laser energy (60 mJ). The laser-induced breakdown was introduced to the mixing layer at 9.5 jet diameters downstream from the jet exit. The chemical delay time scale under the flow condition was approximately 350 µs ( t cd ). The disturbances in density fields generated by laser-induced breakdowns and chemical reactions were visualized using a high-speed schlieren imaging technique. The visualization at stationary air showed that interactions between two laser-induced breakdowns increased the surface area of hot …

Turbulent dimethyl ether (DME) jet flames provide a canonical flame geometry for studying turbulence–flame interactions in oxygenated fuels and for developing predictive models of these interactions. The development of accurate models for DME/air flames would establish a foundation for studies of more complex oxygenated fuels. We present a joint experimental and computational investigation of the velocity field and OH and CH 2 O distributions in a piloted, partially-premixed turbulent DME/air jet flame with a jet exit Reynolds number, Re D , of 29,300. The turbulent DME/air flame is analogous to the well-studied, partially-premixed methane/air jet flame, Sandia Flame D , with identical stoichiometric mixture fraction, ξ st = 0.35, and bulk jet exit velocity, V bulk = 45.9 m/s. Measurements include particle image velocimetry (PIV) and simultaneous CH 2 O and OH laser-induced fluorescence (LIF) imaging. Simulations are …

Imaging measurements and LES-CMC modeling of a partially-premixed turbulent dimethyl ether/air jet flame

Fast Schlieren imaging was performed to visualize the interactions between previously produced laser breakdown and a subsequent laser pulse. A pair of laser pulses was used to generate successive breakdowns in the quiescent standard air, and the interval between the pulses was varied from 50 ns to 100 μ s to experimentally simulate various laser repetition rates. The incident laser energies ranged from 5 mJ to 31 mJ, and the energy absorbed by the breakdown of the second laser pulse was quantified by measuring the energies before and after the breakdown. The results indicate that the second laser pulse coupled to the background gas and produced a second laser breakdown only when the pulse interval was shorter than 250 ns or longer than 15 μ s. For the shorter pulse intervals, the second breakdown occurred at the edge of the first breakdown region along the laser beam path, and its effect on the …

The feasibility of non-thermal plasma gasification of municipal solid waste (MSW) was investigated by modeling waste-to-energy (WtE) power plants, such as an incineration power-plant cycle and integrated plasma gasification combined cycles (IPGCCs) with thermal and non-thermal plasma gasification. The energy analysis delineated operation conditions of non-thermal plasma gasification, which would improve the energy efficiency of the existing IPGCCs. The sensitivity analysis of the energy efficiency showed that cold gas efficiency (CGE), which is the ratio of the heating value of the syngas to the heating value of MSW, is more important than the power consumption of the plasma source for the energy efficiency. From the exergy analysis, it was revealed that the largest exergy loss of the IPGCC was at the plasma gasification, regardless of the type of plasma source. The total exergy loss of IPGCC could be …

The forced flow driven flame spread behavior along an array of discrete wooden fuel elements was experimentally investigated, which could be an important step to understanding the flow-flame interactions that govern fire spread. Fuel arrays with five different spacings (0.75, 0.875. 1.00, 1.125, and 1.25 cm) were subject to flow speeds ranging from 2.2 to 4.3 m/s at approximately 0.2 m/s intervals. For spacing-flow speed conditions tested in the current study, the flame spread behavior was categorized into three different regimes, continuous, discrete, and quenching, and the regimes were presented in a flammability map. Visual analysis of top and side view video data were used to describe the changing flame behavior and increasing discretization of the overall flame structure as the flow speed increases. An analysis of the fluid mechanics and heat transfer conditions revealed a correlation between the Stanton …

Electrodeless microwave plasmas were produced in nitrogen–oxygen mixtures at atmospheric pressure to investigate the formation of nitrogen oxides (NO x) from the plasma. The oxygen content in the mixtures is varied in the range of 1%–3%, and the total flowrate is varied in the range of 25–45 slpm while the microwave power is fixed at 2 kW. The rotational and vibrational temperatures of the plasma are measured based on plasma optical emission spectroscopy, and the amount of NO x is measured using a NO x analyzer far downstream from the plasma. The temperatures at the plasma region reach∼ 6700 K, and little difference is observed between the rotational and vibrational temperatures as a result of fast vibrational–translational relaxation. Moreover, these temperatures are found to be independent of the flowrate. As the flowrate decreases and the oxygen content in the mixture increases, the level of NO x …

Electrodeless microwave plasmas in carbon dioxide at atmospheric pressure have been studied for carbon dioxide decomposition. Plasma optical emission spectroscopy has been conducted to measure ro-vibrational temperatures of the plasma. It is found that the temperature reaches 6200 K at the plasma center and there is little difference between the trans-rotational and vibrational temperatures. Kinetic simulations considering the trans-rotational, vibrational, and electron temperatures separately are also conducted to investigate the details of the plasma decomposition of carbon dioxide. As observed in the measurements, the kinetic simulation demonstrated that the difference between the trans-rotational and vibrational temperatures is negligible, and all the carbon dioxide within the plasma is found to be decomposed into carbon monoxide and atomic oxygen, as a result of the extremely high temperatures of the …

Energy, exergy, and exergoeconomic analyses were performed for two plastic-integrated gasification combined cycle (plastic-IGCC) systems to evaluate the performance of the plastic waste-to-energy cycles. Plastic waste-to-energy is a promising plastic treatment method that can resolve both plastic waste and environmental issues. Thus, improving the efficiency and economy of plastic-IGCC has become crucial because energy is generated during plastic waste-to-energy treatment while treating waste. The difference between the two modeled cycles is the location of heat recovery from the high-temperature syngas. In Cases 1 and 2, heat from the syngas was recovered with a heat recovery steam generator and a gas heater, respectively, to increase the temperature of the air entering the gasifier. The maximum net efficiency for Case 2 increased by 8.2% (from 35.41% to 43.57%), unlike that of Case 1, without …

Energy, exergy, and exergoeconomic analyses of plastic waste-to-energy integrated gasification combined cycles with and without heat recovery at a gasifier

Gasdynamics and Reacting Flow Laboratory

교수님 소개

임성균

연구실 소개

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Influence of wall heat loss on emission characteristics of NH3/CH4/ air premixed flame in a model gas-turbine combustor

Life cycle assessment and techno-economic analysis of naphtha cracking electrification using plasma for carbon neutrality

Optimizing global reaction models for ammonia combustion using Genetic Algorithms

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

임성균

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Influence of wall heat loss on emission characteristics of NH3/CH4/ air premixed flame in a model gas-turbine combustor

Life cycle assessment and techno-economic analysis of naphtha cracking electrification using plasma for carbon neutrality

Optimizing global reaction models for ammonia combustion using Genetic Algorithms

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집