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디젤 분무 연소에서 혼합 분율 스케일링의 영향에 대한 연구
이용운(Yongun LEE),허강열(Kangyoel Huh),박경민(Kyungmin Park),김현옥(Hyunok Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study we present an improved model of turbulent spray combustion to improve accuracy of diesel combustion simulations. Additional source terms due to vaporization are implemented in KIVA with Conditional Moment Closure (CMC) model. Probability density function(PDF) and conditional scalar dissipation rate are scaled to consider limited ranges of mixture fraction by the saturation condition. The expression for the vaporization source term and scaling factors are based on recent direct numerical simulation (DNS) results on turbulent spary combustion. A heavy duty diesel engine is used with early injection timings to test the CMC model with scaled PDF and conditional scalar dissipation. Two and three times the mean mixture fraction are employed as the limiting range for scaling, while another suggestion is based on local PDF lower than an arbitrary small value. Parametric investigation is performed with respect to EGR (Exhaust Gas Recirculation) rate and injection timing. Measured pressure traces and NOx emissions are reasonably well reproduced in wide engine operating conditions.
디젤 엔진 연소 해석을 위한 개선된 난류 분무 연소 모델의 연구
이용운(Yongun Lee),허강열(Kang Y. Huh),김현옥(Hyunok Kim),박경민(Kyungmin Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
We present an improved model of turbulent spray combustion for a diesel engine in this study. The Conditional Moment Closure (CMC) routines are combined with KIVA to provide conditional flame structures to determine mean state variables, instead of mean reaction rates. An independent transport equation is solved for each flame group with equal mass of sequentially injected fuel group. Additional source terms due to evaporation are implemented in KIVA with scaled probability density function (PDF) and conditional scalar dissipation rates (CSDR). The expressions for vaporization source terms and scaling factors are based on recent direct numerical simulation (DNS) results. A heavy duty diesel engine is employed with early injection timings to test the improved CMC model. Soot modeling based on Lindstedt and Hiroyasu model is implemented in the KIVA code. Parametric investigation is performed with respect to EGR (Exhaust Gas Recirculation), injection timing and rpm. Measured pressure traces, NOx and soot emissions are reasonably reproduced in a wide range of engine operating conditions.
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.