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조화진동 난류 예혼합 화염의 운동학: DNS 기반 수소 혼소 화염
김강환(Kanghwan Kim),김용제(Yong Jea Kim),신동혁(Dong-hyuk Shin) 한국연소학회 2022 KOSCOSYMPOSIUM논문집 Vol.2022 No.5
This paper uses direct numerical simulation (DNS) to characterize the kinematics of ensemble-averaged flame position in harmonically oscillating turbulent premixed flames. The flames are stabilized on a harmonically oscillating flame holder. The fuel consists of methane and hydrogen at volume ratio 10:3, and is mixed with air at the stoichiometric ratio. The flame with 4% turbulence intensity is simulated for 20 forcing periods for ensemble averaging. Instantaneous flame positions are extracted from iso-contours of a fixed temperature of 1178 K, which represents the reaction zone. The instantaneous flame positions are then averaged over the same phase of the forcing period. The turbulent flame speed and ensemble-averaged flame position. The turbulent flame speed shows strong linear correlation with the ensemble-averaged flame curvature, if time delays are applied. The ensemble-averaged tangential velocities and normal velocities are shown to correlate with the spatial derivative of the ensemble-averaged flame position with exponential functional shapes.
저압 환경에서의 공력시험을 위한 폐쇄형 소형 풍동의 설계 파라미터 분석 및 전산 해석
김강환(Kanghwan Kim),신지철(Jichul Shin) 한국전산유체공학회 2019 한국전산유체공학회지 Vol.24 No.3
Design parameters for wind tunnel facility aimed for low pressure aerodynamic testings was investigated by two dimensional numerical simulation using a Fluent software. The number of corner vanes before the contraction part showed the most noticeable changes in the flow uniformity at the test section. With 20 corner vanes, span-wise symmetry became worse as the length ratio of the contraction part decreased, while the velocity distribution exhibited the best uniformity when the length ratio was 40%. As the diverging angle of the divergent part after the fan decreased from 3 degree to 2 degree, the flow uniformity was degraded. It turned out that a density change due to the altitude change does not affect the boundary layer profile.