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OpenFOAM을 이용한 난류연소현상 해석 및 내연기관에의 적용
한가람(Karam Han),임성한(Seonghan Im),허강열(Kang Y. Huh) 한국연소학회 2010 KOSCOSYMPOSIUM논문집 Vol.- No.41
OpenFOAM(Open Field Operation And Manipulation) is based on the object oriented language and has been developed as an alternative to commercial CFD tools for industrial application. The advantages of open source CFD allow users to create a more extensive and customized code according to users needs, whereas the commercial tools have difficulty to add or modify any user defined code. To perform IC engine simulation an automatic mesh motion algorithm is built into OpenFOAM. OpenFOAM also provides users with many solvers such as heat transfer and multi phase flow with combustion. In this study simulation of sydney bluff-body HM1 flame, IC engines and gas turbine combustion were performed by OpenFOAM to analyze the turbulent combustion problems. The PaSR(Partially Stirred Reactor) model was applied for a CI engine and gas turbine, while the b-Ξmodel was applied for an SI engine. Results were compared with measurements for some typical test cases.
허강열(Kang Y. Huh) 한국가시화정보학회 2005 한국가시화정보학회지 Vol.3 No.2
내연기관 연소는 난류유동, 분무, 연소, 열전달의 복합적인 현상으로서 열역학적 해석이 주류를 이루어 왔으나 컴퓨터의 발전에 따라 효율 개선과 공해 저감을 목표로 전산유체해석 기법이 적극적으로 도입되고 있다. 내연 기관 연소의 근간을 형성하는 난류 연소 모델링의 기본 개념으로서 가솔린엔진에서의 예혼합연소와 디젤엔진에서의 확산연소에 대한 영역조건평균(zone conditional averaging) 모델과 조건평균닫힘(conditional moment closure) 모델에 대해 설명하였으며 NOx와 soot 예측에 대한 적용과 엔진응용 사례를 소개하였다.
김리나(Lina Kim),유광희(Kwang-Hee Yoo),김종찬(Jong-Chan Kim),성홍계(Hong-Gye Sung) 한국추진공학회 2012 한국추진공학회 학술대회논문집 Vol.2012 No.11
환형 연소기 내에서의 난류 반응 유동을 해석하고 유동 특성을 도출하기 위해 3차원 large-eddy simulation(LES)를 수행하였다. 연소실 내 복잡한 반응성 유동의 화염모사를 위해 level-set flamelet approach를 적용하였으며 proper orthogonal decomposition(POD)을 이용하여 압력 진동 분석을 수행하여 Fast Fourier transform(FFT) 결과와 비교하였다. 계산 모델로서 GEAE사의 LM6000 환형 연소기를 이용하였으며 작동 조건은 실험결과에 근거하였다. 연소실 내에서 난류 유동의 중요한 특징인 vortex breakdown과 연소가스의 팽창으로 인한 중심 재순환 영역, 코너 재순환 영역 등을 관찰하였고, 스월 유동과 연소로 인해 연소기 내부에서 형성되는 속도 성분을 실험값과 비교하였다. POD분석을 통하여 압력 변동 분포와 유동의 지배적인 POD 모드들을 확인하였다. To simulate the flame dynamics in an annular combustor with single swirl injector, a 3D large-eddy simulation(LES) and a level-set flamelet turbulent combustion model have been implemented. Proper Orthogonal Decomposition(POD) analysis has been also used to identify acoustic modal analysis. The LM6000 developed by GEAE has been used as the combustor of concern and boundary conditions are based on experimental data. The strong central toroidal recirculation zone that was induced by the volume of the combustion gas to dilate immediately and the vortex breakdown that occurred continuously through the procession of the vortex with decreasing strength, are observed. The velocity components of the simulation results in the combustor have been compared with corresponding experimental data. Additionally, several dominant modes developed by the turbulent dynamics of the swirl flows were observed.
유동 섭동에 의한 난류예혼합화염의 열발생 모델에 관한 연구
조주형(Ju Hyeong Cho),백승욱(Seung Wook Baek) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.6
The unsteady heat release characteristics play a significant role in combustion instabilities observed in low emissions gas turbine combustors. Such combustion instabilities are often caused by coupling mechanisms between unsteady heat release rates and acoustic perturbations. A generalized model of the turbulent flame response to acoustic perturbations is analytically formulated by considering a distributed heat release along a curved mean flame front and using the flame's kinematic model that incorporates the turbulent flame development. The effects of the development of flame speed on the flame transfer functions are examined by calculating the transfer functions with a constant or developing flame speed. The flame transfer function due to velocity fluctuation shows that, when a developing flame speed is used, the transfer function magnitude decreases faster with Strouhal number than the results with a constant flame speed at low Strouhal numbers. The flame transfer function due to mixture ratio fluctuation, however, exhibits the opposite results: the transfer function magnitude with a developing flame speed increases faster than that with a constant flame speed at low Strouhal numbers. Oscillatory behaviors of both transfer function magnitudes are shown to be damped when a developing flame speed is used. Both transfer functions also show similar behaviors in the phase characteristics: The phases of both transfer functions with a developing flame speed increase more rapidly than those with a constant flame speed.
개선된 CMC 모델을 이용한 pHCCI 디젤 엔진의 연소 해석
서재엽(Jaeyeob Seo),허강열(Kang. Y. Huh) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
This work presents simulation of pHCCI mode diesel combustion by an improved conditional moment closure (CMC) model. The improved CMC model involves flammability limit, multiple flame structures and additional evaporation source terms in the equation for the mixture fraction variance. The evapoation source terms affect local beta function PDFs and conditional scalar dissipation rates (CSDR). An independent transport equation is solved for the fuel vapor of each flame group sequentially injected and evaporated in the cylinder. The conventional CMC model cannot properly consider pHCCI combustion with split injections which may result in a significant amount of lean mixtures. The flammability limits do not allow lean pre-mixtures below the specified limit to participate in combustion. Measured and calculated pressure traces are presented and compared for the test cases with various fuel mass and ratios between two injections. Further research is required for the wall film effect, as fuel injected at an earlier timing goes through significant collision with the wall.
A Heat Release Model of Turbulent Premixed Flame Response to Acoustic Perturbations
조주형(Ju Hyeong Cho),백승욱(Seung Wook Baek) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
The unsteady heat release characteristics play a significant role in combustion instabilities often observed in low emissions gas turbine combustors. Such combustion instabilities are often caused by coupling mechanisms between unsteady heat release rates and acoustic perturbations. A generalized model of the flame response to acoustic perturbations, including mixture ratio perturbations, is analytically formulated to extend the prior models by considering a distributed heat release along the mean flame front and using the flame’s kinematic model that incorporates the turbulent flame development. A specific example for the flame transfer function due to flame area fluctuation showed that, when a developing flame speed is used, the transfer function magnitude decreases faster at low Strouhal number and the transfer function phase increases more rapidly, as compared to the results with a constant flame speed. The results from both types of flame speed observe a well known n-τ model.
문희장,조성찬 한국항공대학교 항공우주산업기술연구소 2003 航空宇宙産業技術硏究所 硏究誌 Vol.13 No.-
Flame propagation is analysed with the use of simple statistical model in a one dimensional spherical coordinate. The objective of this study is the use of novel fuel which is decomposed in an inert gas atmosphere making the reaction with a single step chemical kinetics. DTBP(Di-Tert-Butyl-Peroxide) chemical kinetics is a potential candidate for the study of turbulent combustion since this fuel may be used in conjunction with the development of turbulent combustion models. It was found that the proposed model results approach that of experimental results of DTBP decomposition. The fact that its heat release is at a low level compared to other substances as hydrocarbon fuel, makes the modeling study with DTBP promising. Results of turbulent flame propagation speed by the numerical study under work show that the general trend of the flame propagation is achieved, however numerical results could not simulate the time increase rate of the turbulent flame speed found by experiments.
LES와 Level-set Flamelet 기법을 이용한 가스터빈 환형 연소기용 스월 분사기의 난류 연소 특성
김리나(Lina Kim),홍지석(Ji-Seok Hong),정원철(Won Cheol Jeong),유광희(Kwang-Hee Yoo),김종찬(Jong-Chan Kim),성홍계(Hong-Gye Sung) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.2
To investigate the flame dynamics in an annular combustor with single swirl injector, a 3D large-eddy simulation (LES) and a level-set flamelet turbulent combustion model have been implemented. The LM6000 developed by GEAE has been used as the combustor of concern and boundary conditions are based on experimental data. The strong central toroidal recirculation zone induced by the volume expansion of the combustion gas and the vortex breakdown continuously occurred through the procession of the vortex with decreasing strength, are observed.