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희박 예혼합 저선회 연소기에서 화염부상높이에 관한 고찰
정황희(Hwanghui Jeong),이복직(Bok Jik Lee),한민석(Minseok Han),이기만(Keeman Lee) 한국연소학회 2018 한국연소학회지 Vol.23 No.3
Experiments were carried out to study the flame liftoff height(FLH) and flame stabilization at the fuel-lean region in CH₄/Air premixed flames of a low-swirl combustor. The burner used in this study had a nozzle diameter of 28 mm, a combustion chamber with an expansion area ratio of 7.0, a swirler with a swirl angle of 37°, and a turbulence generator with a porosity of 28.7%. The experiments were performed for equivalence ratios ranging from 0.53 to 0.8 and inlet velocities from 2.3 to 4.6 m/s. The CH* chemiluminescence images were acquired using ICCD camera to measure the FLH. As a result, at the equivalent ratios ranging from 0.8 to 0.6, the FLH increased as the equivalence ratio decreased, which is reasonable as the laminar flame speed decreases along with the decreasing equivalence ratio. At equivalence ratios smaller than 0.6, however, the FLH was reduced despite the reduction in equivalent ratio. At the same equivalent ratio, the FLH decreased at elevated inlet velocities, which was again counterintuitive. According to the results with the absence of a chamber wall, the flame stabilization was observed to be highly dependent on the existence of the outer recirculation zone.
정황희(Hwanghui Jeong),이기만(Keeman Lee) 한국추진공학회 2016 한국추진공학회지 Vol.20 No.4
This study aims to confirm the characteristics of low swirl combustion at our low swirl model combustor. To do it, it is experimentally conducted by evaluating the flame shape, stability region and emissions according to the swirl angle. The most significant feature of low swirl combustion is a occurrence of lifted flame. Such lifted flames happen to combine exquisitely propagating feature of premixed flame with diverging flow. This feature of lifted flame was confirmed through a velocity flow field and visualized the flame in this model combustor. The visualized flame was classified according to the thermal power and equivalence ratio. The variation study in swirl angles showed that the lean flammable limit could be extended only by swirl angles. Also, as the swirl angle increased, it was confirmed that the NOx and CO emissions were decreased due to the mixing enhancement and shorter resident time.
정황희(Hwanghui Jeong),김재열(Jae Yeol Kim),신재렬(Jae-Ryul Shin) 한국추진공학회 2020 한국추진공학회지 Vol.24 No.3
Before we develop LVAFoam, a CFD software for launch vehicle analysis, we conducted a survey on other CFD softwares. We looked at in-house code and commercial CFD software of other countries that were used as a simulation of launch vehicle’s combustor, turbopump and external flow. This research included in-house code solvers, developed by NASA, Mississippi State University, DLR, Bertin Technologies, CNES, CERFACS, and JAXA as well as commercial CFD software from FLUENT, CFX, Advance/FrontFlow/red, GASP, CRUNCH CFD, CFD-ACE+, FINE™/Turbo, STAR-CCM+. The simulation cases of launch vehicle analysis from each commercial softwares and introduction of the LVAFoam were presented.
정황희(Hwanghui Jeong),심근선(Keunseon Sim),이기만(Keeman Lee) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.5
본 연구는 저선회 연소기 주 특징인 부상된 화염의 속도장 특성을 조사한 내용이다. 저선회 연소기는 다공판과 약한 스월러를 통해 균일한 확대 유동장이 생성된다. 이러한 정류된 약 선회유동은 예혼합 화염의 전파 특징과 결합되면서 항상 일정한 높이의 부상화염이 발생하게 된다. 저선회 연소의 기본 연구 관계로 변수인 스월 각도는 37°, 출구 길이는 33.5 mm, 다공판 기공률은 29.6%로 고정하였다. 저선회 연소의 중요한 특징인 균일한 유동장은 PIV와 열선유속계 및 피토튜브를 이용하여 확인하였으며, 측정 장치에 따라 절대 값에서 다소 차이를 보였으나 각 속도별 분포된 경향은 비슷함을 보였다. A study investigated the velocity field characteristics of lifted flame in low-swirl combustor. The diverging flow is generated through the swirler and perforated plate of low-swirl combustor. This swirling flow and the propagating feature of premixed combustion happen the lifted flames. In the study, the parameter was fixed such that the swirl angle is 37°, the length of the outlet is 33.5 mm, the porosity of the perforated plate is 29.6%. There were measured using PIV velocimetry, hot-wire anemometer and Pitot tube to confirm that a uniform velocity field of low swirl combustion as an important features was found by experiments. The each measurement results show that absolute values was a little different but its trend was similar.