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정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Diesel oxidation catalyst (DOC) is a widely used device to reduce harmful species of exhaust gas with less engine back pressure. A one-dimensional model simulating the oxidation of CO, HC and NO was developed to predict the state of gaseous emission exiting a DOC. The model formulation is based on the constraint of conservation of mass, species and energy inside DOC. Kinetics of CO, HC and NO were modeled assuming global reaction using inhibition factor. Steady-state experimental data covering a wide range of operating conditions calibrates the model parameters. The results showed good agreement with the experimental data in a test window of 200℃~500℃ for temperature and 0.1㎥/s~0.7㎥/s for volumetric flowrate.
정승채(Seung-chai Jung),박종선(Jong-sun Park),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
Prediction of diesel particulate filtration necessitates appropriate models for pressure drop and particulate matter (PM) collection, and the models are not frequently deterministic, thus must be closed with certain parameters of much smaller scales typically determined experimentally. Included are soot cake permeability, soot cake density, soot density in filter wall, and percolation constant. Aiming at elucidating these essential parameters, the present study attempts the enhancement of DPF filtration model with non-linear description of soot cake regression, The model is properly validated with single channel DPF measurements. Effects of these parameters on the pressure drop, a direct measure of filtration quality, are estimates in a parametric manner and discussed in terms of filtration velocity. Conclusively, the extent of percolation constant is controlling pressure drops, and soot density in the filter wall is relatively important in deep-bed filtration regime. Filtration quality of the deep-bed mode is relatively less sensitive to particle size than soot cake regime.
열, 첨가제, 촉매에 의한 DPF내 포집된 입자상 물질 재생 모델링
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
DPF reduce particulate emission by physically trapping the particles and the collected PM has to be periodically or continuously removed from the filter by a regeneration process. One of the major issue for DPF system is developing a safe and effective regeneration strategy. In the present study, PM oxidation by heat, fuel additive and catalyzed filter was studied. One-dimensional mathematical models describing regeneration and filtration process were developed. These models can produce spatio-temporal evolution of filter temperature, pressure drop and mass of PM remained in the filter during regeneration. Models are calibrated by measured data and simulation results showed good agreement.
단일 채널 DPF의 PM 포집 모델링 및 모델 파라미터의 민감도 해석
정승채(Seung-chai Jung),박종선(Jong-sun Park),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.6
Prediction of diesel particulate filtration is typically made by virtue of modeling of particulate matter (PM) collection. The model is closed with filtration parameters reflecting all small scale phenomena associated with PM trapping, and these parameters are to be traced back by inversely analyzing large-scale empirical data-the pressure drop histories. Included are soot cake permeability, soot cake density, soot density in the porous filter wall, and percolation constant. In the present study, a series of single channel DPF experiment is conducted, pressure histories are inversely analyzed, and the essential filtration parameters are deducted by DPF filtration model formulated with non-linear description of soot cake regression. Sensitivity analyses of model parameters are also made. Results showed that filtration transients are significantly altered by the extent of percolation constant, and the soot density in the porous filter wall is controlling the filtration qualities in deep-bed filtration regime. In addition, effect of soot particle size on filtration quality is distinct in a period of soot cake regime.
NH₃-SCR 방법에 의한 디젤기관의 NOx 저감과정의 모델링 및 NO₂/NOx, NH₃/NO비에 따른 저감효율 변화 해석
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2008 한국 자동차공학회논문집 Vol.16 No.3
A mathematical modeling of NOx reduction in NH₃-SCR process is conducted. The present deterministic model solves one-dimensional conservation equations of mass and species concentrations for channel flows and the catalytic reaction. NO and NO₂ reactions by the vanadium catalyst in the presence of NH3 are calculated with the rate expressions of Langmuir-Hinshelwood scheme. The modeling was validated with extensive empirical data regarding NOx reduction efficiency. Analysis of De-NOx sensitivity conducted with regard to oxygen and water yielded highly accurate prediction over a wide range of NO₂/NOx ratios from 0 to 1 in a temperature range of 200℃~550℃. The NOx reduction largely depends on NO₂/NOx ratio at temperatures lower than 300℃. NO reduction efficiency is significantly augmented with increasing in NH₃/NO ratio at higher temperatures, whereas rather insensitive to the NH₃/NO ratio at lower temperatures.
NH₃-SCR 방법에 의한 디젤 배기 내 De-NO<SUB>x</SUB> 과정에서의 DOC에 의한 영향과 저감 성능 변화
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2008 한국 자동차공학회논문집 Vol.16 No.5
Diesel NO<SUB>x</SUB>, reduction by NH₃-SCR in conjunction with the effective oxidation precatalyst was analytically investigated. Physicochemical processes in regard to NH₃-SCR NO<SUB>x</SUB> reduction and catalytic NO-NO₂ conversion are formulated with detailed descriptions on the commanding reactions. A unified model is correctly validated with experimental data in terms of extents of NO<SUB>x</SUB> reduction by SCR and NO-NO₂ conversion by DOC. The present deterministic model based on the rate expressions of Langmuir-Hinshelwood reaction scheme finds a conversion extent directly. A series of numerical experiments concomitant with parametric analysis of the NO<SUB>x</SUB> reduction was conducted. NO<SUB>x</SUB> reduction is promoted in proportion to DOC volume ar lower temperatures and an opposite holds at lower space velocity and intermediate temperatures. NO<SUB>x</SUB> conversion is weakly correlated to the space velocity and the DOC volume at higher exhaust temperature. In DOC-SCR system, the NO<SUB>x</SUB> reduction efficiency depends on the NH₃/NO<SUB>x</SUB> ratio.
DOC-DPF-SCR 시스템에 의한 디젤 배기 내 NO<SUB>x</SUB>, 입자상 물질 저감 과정의 일관 모델링 및 성능 예측
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2008 한국 자동차공학회논문집 Vol.16 No.4
Computer methods with simplified mathematical models in conjunction with empirical model parameters can be efficiently practiced into an optimization of a diesel aftertreatment system. Components of prime interests are diesel particulate filter, diesel oxidation catalyst and de-NO<SUB>x</SUB> catalytic converter. de-NO<SUB>x</SUB>, de-PM, and de-HC processes in each part are individually modeled, formulated and then combined into an integrated analysis procedure for a unified simulation of the diesel emission aftertreatment. The model is empirically tuned and validated with comprehensive engine and laboratory data. The effects of emission species and space velocity on the NO<SUB>x</SUB> and soot reductions are parametrically investigated. A lowered NO₂/NO<SUB>x</SUB> ratio due to PM oxidation in DPF contributes to promote the NO<SUB>x</SUB> reduction by SCR at intermediate gas temperatures. NO<SUB>x</SUB> reduction is inert to the PM oxidation at high temperatures. Rate of PM trapping strongly depends on temperature and NO<SUB>x</SUB> concentration.
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Particulate filter system has been developed to cope with tight diesel PM emission regulations. One of the major issue for DPF system is building a safe and effective regeneration strategy. In the present study, NO₂-assisted regeneration method using DOC was studied. A one-dimensional DOC model simulating oxidation of chemical species was developed to predict the gaseous emission downstream of DOC, especially NO₂ concentration. And this model was incorporated with one-dimensional DPF model simulating particle filtration, pressure drop and PM oxidation to predict filtration and regeneration performance of DOC+DPF system. Mathematical models were calibrated with the controlling parameters obtained from DOC+DPF test.
DPF의 PM 포집효율 예측을 위한 다양한 다공성 매질 유동장 모델 해석
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.1
In the present study a detailed examination of various porous media models for predicting filtration efficiency and pressure drop of diesel particulate filter (DPF), such as sphere-in-cell and constricted tube models, are attempted. In order for demonstrating their validities of correct estimation on permeability, geometry of property configurations common in commercial cordierite DPFs are correlated to the porous media flow models, and validations of predicted filtration efficiencies due to the use of different unit collectors are made with experiments. The result shows that the porosity, pore size and permeability of cordierite DPF can be successfully correlated by Kuwabara flow field with correction factor of 0.6. The unit collector efficiency predicted by sphere-in-cell model agrees very well with measurements in accumulation mode, whereas that by constricted tube model with significant prediction error.
NH₃-SCR 방법에 의한 디젤 배기 내 De-NO<SUB>x</SUB> 과정에서의 DOC에 의한 영향과 거감 성능 변화 해석
정승채(Seung-chai Jung),윤웅섭(Woong-sup Yoon) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A positive influence of oxidation precatalyst on the NOx reduction by NH₃-SCR was analytically investigated. Physicochemical processes in regard to NOx reduction by NH₃-SCR and NO-NO₂ conversion by the oxidation catalyst are formulated with proper models for individual physics. A unified model is correctly validated with experimental data in terms of NOx reduction efficiency for SCR and NO-NO₂ conversion efficiency for DOC. The model equipped with rate expressions of Langmuir-Hinshelwood type reaction scheme is deterministic and finds a conversion extent directly. A series of numerical experiments were carried out and parametric analysis of the NOx reduction was conducted. NOx reduction is expedited in proportion to DOC volume at lower temperatures, whereas deactivated with increasing DOC volume when the space velocity is lower at intermediate temperature regime. At intermediate temperatures, NOx conversion is proportionally increasing with the space velocity. NOx conversion is a weak function of the space velocity and DOC volume at higher exhaust temperatures. In DOC-SCR system, the NOx reduction efficiency is gradually increasing with NH₃/NOx ratios.