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FIRE를 이용한 디젤 엔진 연소, NOx 및 매연 모사 계산 및 검증
허강열(Kang. Y. Huh),이용운(Yongun Lee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
In this study parametric investigation is performed for a diesel engine with respect to EGR rate, injection timing. The engine is a heavy duty diesel engine operated with early injection timings to simulate an HCCI engine mode at a low rpm. The commercial code FIRE is employed for prediction of in-cylinder spray, combustion and production of NOx and soot emissions. Different sprays models including no breakup with a fixed SMD and Huh-Gosman model are tested for comparison with measurements. The Arrhenius type Shell ignition model is used with the standard set of constants for autoignition. The eddy dissipation model and characteristic time scale model are used for comparison during premixed and diffusion controlled combustion phases. Models for spray atomization and turbulent combustion involve some arbitrary constants, which require tuning for given specific cases. However results do not show much dependence on choice of the constants in reasonable ranges. Simulation results agree well with the measured data set for pressure traces, NOx and soot emissions for all 9 parametric 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.
허강열(Kang Y. Huh) 한국가시화정보학회 2004 한국가시화정보학회지 Vol.2 No.1
Conditional sampling measurement is required for conditional averages as well as unconditional Favre averages to resolve different flame structures of turbulent combustion. A Favre average can be obtained as an integral of conditional average and Favre PDF in terms of the mixture fraction, which is a preferred choice as a sampling variable in diffusion controlled turbulent combustion. MILD combustion data are presented as an example for a conditionally averaged data set and comparison with CMC calculation results.
직접 관계 그래프(DRG)를 이용한 디젤 연료의 상세 화학 반응 기구 축소화
이영재(Young J. Lee),허강열(Kang Y. Huh) 한국연소학회 2011 한국연소학회지 Vol.16 No.2
It is a challenging task to apply large detailed chemical mechanisms of fuel oxidation in simulation of complex combustion phenomena. There exist a few systematic methodologies to reduce detailed chemical mechanisms to smaller sizes involving less computational load. This research work concerns generation of a skeletal chemical mechanism by a directed relation graph with specified accuracy requirement. Two sequential stages for mechanism reduction are followed in a perfectly stirred reactor(PSR) for high temperature chemistry and to consider the autoignition delay time for low and high temperature chemistry. Reduction was performed for the detailed chemical mechanism of n-heptane consisting of 561 species and 2539 elementary reaction steps. Validation results show acceptable agreement for the autoignition delay time and the PSR calculation in wide parametric ranges of pressure, temperature and equivalence ratio.
OpenFOAM을 이용한 가스 터빈 운전 조건에서의 연소 특성 및 NOx 생성 경로 연구
정대로(Daero Joung),허강열(Kang Y. Huh) 한국연소학회 2011 KOSCOSYMPOSIUM논문집 Vol.- No.42
Numerical analysis was performed to investigate the NOx formation pathways on gas turbine conditions using OpenFOAM. Validation is done against measurement data for mean flow and scalar fields of Sydney swirl flame, SM1. The standard k-e model was employed to reproduce mean turbulent flow field and turbulence-chemistry interaction was modelled by partially stirred reactor approach with GRI 3.0 mechanism. In this study NOx formation pathways including Zeldovich, nitrous oxide and prompt were investigated for gas turbine conditions. Results were compared to the experimental data of high-pressure jet-stirred reactor operating on lean-premixed methane/air.
조건 평균 방법을 이용한 소형 고속 직분식 디젤 엔진의 난류 연소 3차원 모사 연구
한인석(Insuk Han),허강열(Kang Y.Huh),박남섭(Namseob Park) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Turbulent spray combustion in a direct injection diesel engine is investigated numerically by the first order Conditional Moment Closure (CMC) model. This model allows employment of detailed chemistry for simulation of autoignition, nonpremixed combustion and pollutant formation in a consistent manner. KIVA 3V and CHEMKIN 2 are used to solve the governing equations for flow field and chemistry. Simplified CMC equations are applied to with KIVA adopting a complicated moving grid system. Validation is performed against experimental pressure data for different injection conditions and engine speeds with discussions for obvious deviation in the early combustion phase with and without pilot injection.<br/>
복수 화염 구조와 조건 평균 방법을 이용한 디젤 엔진 연소 연구
한인석(Insuk Han),허강열(Kang Y. Huh) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Combustion of turbulent sprays in a direct injection diesel engine is modeled by the conditional moment closure (CMC) model. The CMC routines are combined with the KIVA code to provide conditional flame structures to determine the mean state variables, instead of the mean reaction rate. An independent transport equation is solved for each flam group with equal mass of sequentially evaporating fuel vapor. CMC calculation begins as the fuel mass for each flame group begins to evaporate with corresponding initialization conditions. Comparison is made with the measured pressure traces for two different direct injection diesel engines. Results show that the CMC model with multiple flame histories can successfully be applied to the ignition and mixing-controlled combustion phases of a diesel engine.
난류 예혼합 화염 선단부의 통계적 특성에 관한 수치적 연구
권재성(Jaesung Kwon),허강열(Kang Y. Huh) 한국연소학회 2013 한국연소학회지 Vol.18 No.1
Leading edge statistics are obtained by direct numerical simulation(DNS) of freely propagating incompressible and stagnating compressible turbulent premixed flames. Conditional averages of velocities in terms of reaction progress variable, c, and local flame surface density, Σf, are defined and compared through the flame brush. It holds asymptotically that 〈u〉f = 〈Sd〉f and 〈u〉u - 〈u〉b = Dt/Lω with the characteristic length scale of c variation, Lω. It also holds that 〈u〉b = 〈u〉f for a freely propagating flame under no mean strain rate. The turbulent burning velocity, ST, is determined by the conditional statistics at the leading edge under large activation energy.