In Clean Combustion & Energy Research lab, we are investigating the characteristics of laminar/turbulent reacting flows using direct numerical simulations (DNS), large eddy simulations (LES), and Reynolds-Averaged Navier-Stokes Simulations (RANS) to understand flame instability, turbulence/chemistry interaction, etc. An indepth understanding of fundamental characteristics of laminar/turbulent flames can help us develop next-generation IC engines, gas turbines (GT), and commercial boilers. We are also interested in hydrogen/ammonia/supercritical/plasma combustion to develop low carbon/high-efficient IC engines and GT combustors. Hydrogen and ammonia are carbon-free energy source such that they are now being applied to conventional GT combustors. Recently, a supercritical GT combustion emerges as a next-generation technology for power generation, and hence, we are investigating the characteristics of supercritical combustion at 250 bar or above. To reduce NOx emission, fuel-lean combustion is inevitable, which ultimately induces flame instabilities in the combustor. To control such flame instabilities, plasma-assisted combustion is also actively investigated. In addition, we are developing a CFD code for hydrogen production through ammonia cracking considering both gas-phase chemistry and surface chemistry.