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입구 및 출구 형상 변화에 따른 촉매 삽입형 머플러 내부의 유동 해석
안태현(Tae Hyun An),이승엽(Seung Yeop Lee),박윤범(Yun Beom Park),김만영(Man Young Kim) 한국자동차공학회 2013 한국 자동차공학회논문집 Vol.21 No.5
Lack of the space in many diesel vehicles make it difficult to design and install the catalytic muffler to reduce emissions. For this reason, inlet part of the catalytic muffler is made of L-type which has lower flow uniformity than conventional I-type, and catalytic muffler has complex internal structure by various insertions, which affect the flow uniformity and pressure drop of the systems. In this work, the flow characteristics such as flow uniformity and pressure drop have been numerically investigated by changing such various geometries as inlet shape, porosity, and outlet shape inside the muffler with the three-dimensional turbulent incompressible flow solver. Total 4 different cases are considered in order to find optimal configurations of the catalytic muffler in view of high flow uniformity and low pressure drop. The results show that Case 2 which has no induction cone and outlet perforated pipe has higher uniformity index and lower pressure drop than others considered in this work.
디젤 배기관에 분사된 우레아 수용액의 분무 거동 및 유동특성에 관한 연구
안태현(Tae Hyun An),김홍석(Hong Suk Kim),박윤범(Yun Beom Park),김만영(Man Young Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
To satisfy the NOx regulations which are being strengthened, the selective catalytic reduction (SCR) system based on urea water solution is an effective technique to reduce nitrogen oxides (NOx) emitted from diesel engines. However, a mobile SCR system is restricted to a short distance between the exhaust pipe and the SCR catalyst entrance. For this reason, this device has some issues associated with the ammonia slip phenomenon which is occurred by shortage evaporation and thermolysis time, and that makes it difficult to achieve uniform distribution on the injected urea. Therefore, in this work, the numerical study was performed by changing various parameters such as injector angle, exhaust gas temperature, and application of mixer to enhance evaporation and mixing of urea water solution with mixer application and injector angle between urea and exhaust gases. The mixer was located between injector and SCR catalyst entrance, and the injector angle changes from 30° to 60°. It can be observed that various parameters such as the angle of the injector and application of mixer significantly affect the evaporation and mixing of urea water solution with exhaust gases, and therefore, optimization of these parameters are required. Finally, it can be found that the cases adopted mixer with an injector angle of 30 or 60° showed the best performance in terms of the maximum NH3 concentration and uniformity, and suggested useful guidelines to achieve the optimum design of a urea-SCR injection system for improving DeNOx performance and reducing ammonia slip.
디젤 배기관에 분사된 우레아 수용액의 분무 거동 및 유동 특성에 관한 연구
안태현(Tae Hyun An),김만영(Man Young Kim) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.1
Urea-SCR 시스템은 주로 열해리와 증발시간의 부족으로 인해 발생하는 암모니아 슬립 현상과 관련된 몇 가지 문제점들을 가지고 있으며, 이러한 문제점들은 분사된 요소수용액의 불균일한 분포를 초래한다. 따라서 본 연구에서는, 배기가스와 요소수용액 사이의 증발 및 혼합특성을 강화시키기 위해 인젝터 장착 각도 그리고 믹서의 장착 및 설치 각도와 같은 다양한 매개변수들을 바꾸며 전산해석 연구를 수행하였다. 그 결과, 이와 같은 매개변수들이 배기가스와 요소수용액의 증발 및 혼합특성에 상당한 영향을 미친다는 것을 알 수 있었으며, 이 매개변수들의 최적화가 요구된다. 또한, 본 논문은 Urea-SCR 분사 시스템의 DeNOx 성능을 증가시키고 암모니아 슬립을 감소시키기 위한 최적 설계 시 유용한 기준을 제안할 것이다. A urea-SCR system suffers from some issues associated with the ammonia slip phenomenon, which mainly occurs because of the shortage of evaporation and thermolysis time, and this makes it difficult to achieve an uniform distribution of injected urea. A numerical study was therefore performed by changing such various parameters as installed injector angle and application and angle of mixer to enhance evaporation and the mixing of urea water solution with exhaust gases. As a result, various parameters were found to affect the evaporation and mixing characteristics between exhaust gas and urea water solution, and their optimization is required. Finally, useful guidelines were suggested to achieve the optimum design of a urea-SCR injection system for improving the DeNOx performance and reducing ammonia slip.
56kW Off-road 디젤엔진의 Tier 4 Final NOx 배기규제를 만족시키기 위한 SCR De-NOx 성능 향상에 관한 수치해석 연구
안태현(Tae Hyun An),고건영(Gun Yung Go),김만영(Man Young Kim),김홍석(Hongsuk Kim),강정호(Jeong-Ho Kang),정학섭(Hak Sup Jung) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
Diesel engine is being used widely in many industrial fields, as it provides merits in the aspects of higher thermal efficiency and less CO₂ emission. Due to environmental problems caused by toxic exhaust emissions occurred from diesel engines, however, the regulations on off-road diesel engines are being strengthened from Tier 4 interim to Tier 4 final, and it is impossible to meet the emission regulations without post-processing technology such as SCR. Therefore, this study has been conducted to improve De-NOx performance of SCR catalyst during non-road transient cycle mode. In this study, the characteristic of the emission gases with LOT curve, DOC/DPF, and ANR was analyzed. Finally, it can be found that above-mentioned various parameters significantly affect the De-NOx performance of SCR catalyst, then optimization of these parameters to meet the Tier 4 Final emission regulation are required.
Urea-SCR 시스템에서 배기관 내 요소수용액의 증발 및 혼합특성에 관한 수치해석 연구
안태현(Tae Hyun An),이승엽(Seung Yeop Lee),김만영(Man Young Kim),이지근(Jee Keun Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Urea water solution is sprayed into the hot exhaust stream through installed injector in the exhaust pipe, and injected urea water solution experiences thermal decomposition into NH₃, and finally reduces NO<SUB>x</SUB>. For this reason, to optimize the urea dosing system, thermal decomposition and mixing characteristics of urea water solution into NH3 have been studied to design optimum sizes and geometries of the mixing chamber in the selective catalytic reduction (SCR) system because this device has some issues associated with the ammonia slip which is occurred by shortage of evaporation and thermolysis time, and that makes it difficult to achieve uniform distribution of the injected urea in front of the catalyst. Therefore, in this study, the effects of the injector angle on the NH₃ concentration distribution at the end face of the exhaust pipe which is at the front face of the SCR catalyst have been examined with detailed three-dimensional turbulent flow of the compressible, reacting, and unsteady state to retain optimum flow characteristics of urea-SCR system. Finally, it can be found that the case with an injector angle of 15° showed the best performance in terms of the maximum NH₃ concentration and uniformity, and suggested useful guidelines to achieve the optimum design of a urea-SCR injection system for improving DeNO<SUB>x</SUB> performance and reducing ammonia slip.
냉각수 및 전기 가열 방식에 따른 요소수 해동 특성에 관한 수치해석 연구
안태현(Tae Hyun An),이승엽(Seung Yeop Lee),이천환(Chun Hwan Lee),박윤범(Yun Beom Park),김만영(Man Young Kim) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.5-1
Urea-SCR system which converts nitrogen oxides into nitrogen and water in the presence of a reducing agent becomes major exhaust gas aftertreatment system for NOx reduction among other systems. To regard its vehicle application, an urea solution is chosen at its eutectic composition(32.5wt% urea). An important advantage of this eutectic composition is that its melting point(-11.7 ℃ ) is low to avoid solidification in cold environments. The solution to inspect vehicle applications must be provided to the injection system in the liquid state. Particular in case of low ambient temperature levels, the storage tanks must be heated separately, to ensure a sufficient amount of liquid during start up schedule. In this study, therefore, numerical investigation of three dimensional unsteady heating problem was analyzed to understand the melting processes and heat transfer characteristics such as liquid volume fraction, temperature distributions, and temperature profiles in urea solution with coolant and electric heater models by using the commercial software Fluent 6.3. The results show that phase transition of urea solution from the storage tank interface to the center was carried. Also, the melting performance to apply the electric heater is higher than the coolant heater has the efficiency. A liquid urea rate per same area is 0.0122cc/mm<SUP>2</SUP>, and that is the most melted thing in the EH2 model.
효과적인 Ammonium Carbonate 승화를 위한 반응기 유동해석
정명희(Myeong Hee Jeong),안태현(Tae Hyun An),김만영(Man Young Kim),김홍석(Hongsuk Kim) 한국자동차공학회 2013 한국자동차공학회 학술대회 및 전시회 Vol.2013 No.11
Due to reinforced environmental regulations on vehicle emissions, Urea-based SCR(Selective Catalytic Reduction) that supplies SCR with a reductant by using urea water solution is used in order to reduce Nitrogen oxides (NOx) in the exhaust gas of the engine. But it has a number of issues at low temperatures, including freezing below - 12 ℃, solid deposit formation in the exhaust, and difficulties in supplying SCR with a reductant at exhaust temperatures below 200 ℃. On the other hand, ammonium carbonate, one of ammonia storage materials, has the low thermal decomposition temperature, so it generate the ammonia gas from the solid to the vapor at an exhaust temperatures below 200 ℃. Consequently, in this study, we did a numerical study for various figuration reactors heat and fluid flow by using exhaust gas heat to sublimate ammonium carbonate in the form of cartridges effectively.