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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.
이석영(Sukyoung Lee),허강열(Kang Y. Huh) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This study describes the combustion characteristics of homogeneous charge of methane-air mixture with various initial pressure, equivalence ratio and ignition times of mixture in constant volume combustion chamber. The constant volume combustion chamber(CVCC) mostly has been studied by the experiments of visualization until now. So it is needed the numerical analysis of fluid and combustion characteristics in chamber by the more detail simulation. In this paper, the numerical analysis is tried to approach basically the homogeneous charge combustion phenomena under the various conditions, and the combustion phenomena in chamber is numerically analyzed by the commercial FIRE code. As a results, the combustion phenomena which were mean temperature, OH radical and reaction rate in chamber were investigated.
FIRE cede를 사용한 성층급기 연소현상에 관한 연구
이석영(Sukyoung Lee),허강열(Kang Y. Huh) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The direct-injection stratified-charge(D1SC) engine is considered to be a promising alternative to conventional spark ignition engines. It has, however, an unfavorable feature of high unburned hydrocarbon emission levels, especially during light load operations. The researches about constant volume combustion chamber(CVCC) mostly have been the experiments by visualization or the simpler numerical analysis until now. So it is needed the analysis of fluid and combustion characteristics in chamber by detail simulation. In this paper, this analysis is approaching basically the stratified charge combustion phenomena with 3 types of rich, homogeneous and lean mixture injection through the experiment and numerical analysis. And the combustion phenomena in chamber is numerically analyzed by the commercial code FIRE. The calculated results show the combustion phenomena which are mean temperature, OH radical and reaction rate, etc. in chamber.
CO₂ 재순환에 의한 순산소 연소와 공기 연소의 화염 특성 비교
이승환(Seung Hwan Lee),허강열(Kang Y. Huh) 한국연소학회 2008 한국연소학회지 Vol.13 No.3
Steady Laminar Flamelet Model (SLFM) calculation is performed to compare the turbulent combustion characteristics of air combustion and oxy-combustion with CO₂ recirculation. Radiative heat loss is considered by the optically thin limit assumption. For more realistic simulation the first-order conditional moment closure (CMC) model applied to SANDIA PILOTED FLAME D again for the oxidants of air and mixture of O₂ and CO₂. The chemical kinetic mechanism for methane is GRI Mech 3.0. Results show that oxy flames are much more stable than air flames, while camparable stability is maintained with 65% CO₂ recirculation. The comparable peak temperature is maintained with 80% CO₂ recirculation. Higher the temperature, higher the fractions of intermediate species, CO and OH, due to dissociation.
HCCI 연소 모사를 위한 n-heptane 상세 및 축소 반응 메커니즘 비교/검증에 대한 연구
이영재(Young J. Lee),허강열(Kang Y. Huh) 한국연소학회 2008 KOSCOSYMPOSIUM논문집 Vol.- No.-
In this paper detailed and reduced chemical kinetic reaction mechanisms of n-heptane are investigated to understand the complexities of HCCI combustion. The detailed, skeletal and reduced n-heptane kinetic mechanisms are tested for comparison of ignition delays, PSR solution and mole fraction profiles of some radicals. The locally deterministic approach is employed to consider spatial inhomogeneities in an HCCI engine by the KIVA A and CHEMKIN package. Results show some discrepancy between measured and calculated pressures with estimated residual fractions.
영역조건평균에 기초한 난류예혼합 화염 전파 속도식 유도 및 검증
이동규(Dongkyu Lee),허강열(Kang Y. Huh) 한국연소학회 2008 한국연소학회지 Vol.13 No.1
An analytical expression for the turbulent burning velocity is derived from the asymptotic zone conditional transport equation at the leading edge. It is given as a sum of laminar and turbulent contributions, the latter of which is given as a product of turbulent diffusivity in unburned gas and inverse scale of wrinkling at the leading edge. It was previously shown that the inverse scale is equal to four times the maximum flame surface density in the wrinkled flamelet regime [1]. The linear behavior between UT and u′ shows deviation with the inverse scale decreasing due to the effect of a finite flamelet thickness at higher turbulent intensities. DNS results show that UT/S<SUP>0</SUP>Lu may be given as a function of two dimensionless parameters, u'/S<SUP>0</SUP>Lu and and lt/δF which may be transformed into another relationship in terms of u'/S<SUP>0</SUP>Lu and Ka. A larger lt/δF or a smaller Ka leads to a smaller scale of wrinkling, hence a larger turbulent burning velocity in the limited range of u'/S<SUP>0</SUP>Lu. Good agreement is achieved between the analytical expression and the turbulent burning velocities from DNS in both wrinkled and thickened-wrinkled flame regimes.