SIMULATION STUDY ON THERMAL MANAGEMENT STRATEGY TO ACHIEVE 99 % SCR EFFICIENCY OF A HEAVY-DUTY DIESEL ENGINE OVER A TRANSIENT CYCLE

Taejoong Wang,Jung Ho Kim 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.4

In this study, NOx conversion characteristics of a urea selective catalytic reduction (SCR) system equipped on a heavy-duty diesel engine were evaluated through engine dynamometer bench tests over a scheduled world harmonized transient cycle (WHTC). Also, based on transient SCR simulations, the thermal management strategy to improve SCR NOx conversion efficiency was investigated. As a result, it was found that a selective increase in exhaust temperature at low temperature period would be a useful measure to increase SCR efficiency on WHTC mode. From the baseline SCR efficiency of around 98 % on WHTC mode, the current simulation results have shown that around 99 % level of SCR efficiency would be achievable by increasing exhaust temperatures with modifying diesel exhaust fluid (DEF) dosage. Another valuable contribution of this study is that the design guidelines for controlling exhaust temperature and DEF injection to obtain a target NOx conversion efficiency are presented for SCR systems of heavy-duty diesel engines on transient operating conditions.

Optimum design for intake and exhaust system of a heavy-duty diesel engine by using DFSS methodology

Taejoong Wang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

In this study, an optimum design for intake and exhaust system of a heavy-duty diesel engine was conducted by using the well-known design for six sigma (DFSS) methodology. As a result of this work, the NOx emission regulation has been successfully satisfied while minimizing the fuel consumption. On the basis of this DFSS work, the design robustness of the engine system was also enhanced. Hence, it is expected that the final design proposal would reduce the variability in brake thermal efficiency (BTE) that could be caused by the harsh environment and the system aging. Especially, this work has successfully raised the amount of exhaust gas recirculation (EGR) up to the target level by adopting the venturi tubes in the intake and exhaust lines. In this study, engine cycle simulation technique was employed to assess the effect of the various design parameters and the final design proposal was verified through a real engine test. The current optimum design work has considered four control factors such as the size of turbocharger, the diameter of intake and exhaust venturi pipes, and the efficiency of EGR cooler. Here, an L9 orthogonal array was employed to efficiently choose the best design proposal among 81 design combinations (i.e., four independent control factors which individually have three different levels).

EFFECT OF HYDROTHERMAL AGING OVER A COMMERCIAL DOC ON NO2 PRODUCTION AND SUBSEQUENT SCR EFFICIENCY

Taejoong Wang 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.6

In this study, the effect of hydrothermal aging over a commercial diesel oxidation catalyst (DOC) on deterioration in nitrogen dioxide (NO2) production activity has been experimentally investigated based on a micro-reactor DOC experiment. Through this experimental result, the NO2 to nitrogen oxides (NOx) ratio at DOC outlet has been mathematically expressed as a function of DOC temperature according to various aging conditions. The current study reveals that the catalyst aging temperature is a more dominant factor than the aging duration in terms of the decrease in NO2 production performance through DOC. The DOC sample hydrothermally aged for 25 h at 750 °C has displayed the lowest NO2 to NOx ratio compared to the samples aged for 25 ~ 100 h at 650 °C. Also, in this study, the impact of hydrothermal aging of a DOC on the selective catalytic reduction (SCR) efficiency in a ‘DOC + SCR’ aftertreatment system was predicted by using transient SCR simulations. To validate the SCR simulation, this study has conducted a dynamometer test of a non-road heavy-duty diesel engine with employing a commercial ‘DOC + SCR’ system on the exhaust line. The current study has quantitatively estimated the effect of the variation in NO2 to NOx ratio due to the hydrothermal aging of DOC on the NOx removal efficiency of SCR.

COMBUSTION SYSTEM DESIGN OF A GENSET DIESEL ENGINE BY USING DFSS METHODOLOGY

Taejoong Wang,Seungkwon Hwang 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.3

In this study, an optimum design for the combustion system of a genset diesel engine was conducted by using Design for Six Sigma (DFSS) methodology. As a result of this study, the best combination of design parameters to minimize the fuel consumption of the genset diesel engine was selected while meeting the requirements of NOx emission and peak firing pressure (PFP) limit. Compared to the initial design, the final design proposal has achieved 2.5 % and 1.6 % improvement in brake specific fuel consumption (BSFC) at switchable operating conditions, i.e., both 1500 and 1800 rpm. On the basis of this DFSS work, the design robustness was also enhanced. Hence, it is expected that the final design proposal would reduce the variability in fuel economy that could be caused by harsh environment and system aging. In this study, engine cycle simulation technique was employed to assess the effects of various design parameters on the performances of the genset diesel engine. The current optimum design work has considered four control factors such as turbocharger size, air temperature at charge air cooler (CAC) outlet, compression ratio, and fuel injection duration. Here, an L9 orthogonal array was used to efficiently choose the best design proposal among 81 design combinations (i.e., four independent control factors which individually have three different levels).

모노리스 NH₃-SCR 반응기 내에서의 NH₃ 흡·탈착 특성에 대한 연구

왕태중(Taejoong Wang),백승욱(Seungwook Baek),정명근(Myunggeun Jung),길정기(Jeongki Kil),여권구(Gwonkoo Yeo) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1

Transient kinetics of NH₃ adsorption/desorption and of SCR (selective catalytic reduction) of NO with NH₃ were studied over vanadium based catalysts, such as V₂O_5/TiO₂ and V₂O_5-WO₃/TiO₂. In the present catalytic reaction process, NO adsorption is neglected while NH₃ is strongly chemisorbed on the catalytic surface. Accordingly. it is ruled out the possibility of a reaction between strongly adsorbed NH₃ and NO species in line with the hypothesis of an Eley-Rideal mechanism. The present kinetic model assumes; (1) non-activated NH₃ adsorption, (2) Temkin-type NH₃ coverage dependence of the desorption energy, (3) non-linear dependence of the SCR reaction rate on the NH₃ surface coverage. Thus, the surface heterogeneity for adsorption/desorption of NH₃ is taken into account in this model. The present study extends the pure chemical kinetic model based on a powdered-phase catalytic system to the chemico-physical one applicable to a realistic monolith reactor.

모노리스 NH₃-SCR 반응기 내에서의 NH₃ 흡ㆍ탈착 특성에 대한 연구

왕태중(Taejoong Wang),백승욱(Seungwook Baek),정명근(Myunggeun Jung),여권구(Gwonkoo Yeo) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.3

고압에서의 분무의 증발 및 연소 현상에 관한 연구

왕태중(Taejoong Wang),백승욱(Seungwook Baek) 한국연소학회 2002 KOSCOSYMPOSIUM논문집 Vol.- No.-

EURO-VI 대응 상용 디젤자동차의 후처리시스템 적용 기술

김득상(Duksang Kim),왕태중(Taejoong Wang) 한국자동차공학회 2013 오토저널 Vol.35 No.9

위에서 소개한 바와 같이 EURO-VI 배기규제 이후로부터는 승용 소형자동차와 상용 대형 디젤자동차의 배기규제 수준은 거의 동등 수준으로 유지될 것으로 예상되고 있다. 승용과 상용 모두 이러한 지속적인 배기규제 강화는 매우 높은 수준의 기술적 도전과 직면하는 것이며, 특히 상용 자동차의 경우 차량의 운전특성 및 소비자의 요구가치가 승용차와 다른 점이 많으므로 보다 다양한 관점에서 기술적 대안을 검토해야 할 필요성이 높다. 향후 본격적인 온실가스 규제 및 CO2 규제가 발효되면 그동안 소비자 가치로 인식되어 온 연비가 적극적인 규제 대상이 될 것으로 보이며, 이에 따라 연비 향상 기술이 배기규제 만족을 위한 필수 기술로 인식될 것으로 보인다. 즉, 엔진의 연소 및 후처리기술의 지속적인 발전과 더불어, 배기열 회수기술 및 Turbo-compounding과 같은 연비개선 기술이 점차 일반화될 가능성이 높으며, 이러한 기술의 도입 및 적용은 기존의 연소시스템 및 후처리시스템과 통합적으로 관리, 운용되어야만 배기 및 연비규제에 동시에 대응 가능한 기술로 정착될 수 있을 것으로 보인다. 또한 Off-highway 장비인 건설장비, 굴삭기, 비도로용 트럭, 발전기 및 선박에 이르는 다양한 Heavy-Duty 장비에도 EURO-VI 동등 수준의 배기규제 강화가 지속적으로 논의되고 있으며, 이에 대한 적극적인 기술 개발이 꾸준히 이루어져야 할 것으로 생각한다.

Stage V 규제 만족을 위한 디젤 엔진 기술 전망

김득상(Duk Sang Kim),왕태중(Taejoong Wang) 한국자동차공학회 2017 오토저널 Vol.39 No.10

Design of combustion bowl geometry to meet final Tier 4 of 11 L non-road heavy-duty diesel engine with multi-dimensional combustion simulation

Sangyul Lee,Jongyoon Lee,Seungkwon Hwang,Taejoong Wang,Youngbok Lee 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

To comply with the new non-road emission standards, final Tier 4, two big strategies have been applied to the 11 L heavy-duty diesel engine. The first strategy is to apply Exhaust gas recirculation and selectivity catalytic reduction system to meet the NOx limitation. The other one is to apply low swirl ratio (for higher volumetric efficiency) and multi-hole nozzle, a high pressure direct injection, and an optimized combustion system in order to reduce PM emission. Both strategies put a focus on the optimization of combustion system. In this study, a ULPC bowl concept applied in the previous works has been successfully verified in 11 L heavy-duty diesel engine with wellvalidated 3D combustion simulation, and the ULPC bowl shape has been geometrically optimized. A rough 0D calculation is used to calculate the fuel split ratio of the various ULPC bowl shapes. In the rated-power operating condition of the final Tier 4 engine which is deduced by 1D cyclic simulation, the optimal fuel split ratio of the injected fuel has been verified. Also, additional geometric optimization has been achieved without changing the optimal fuel split ratio. From these results, soot has been reduced by about 30% with ULPC optimum bowl shape against the Tier 3 re-entrant bowl shape.