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촉매삽입형 Urea-SCR 머플러 다공튜브 형상변화에 따른 NOx 저감 특성에 관한 연구
문남수(Namsoo Moon),이상규(Sangkyoo Lee),고상철(Sangchul Ko),이지근(Jeekeun Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.12
Urea-SCR 머플러 시스템 입구와 촉매 전단에 설치된 다공튜브는 우레아 수용액 분무의 균일분포, SCR 촉매 활용도 증대 및 암모니아 슬립을 방지하기 위해 사용되고 있다. 다공튜브의 오리피스 면적비 변화가 머플러 챔버 내부유동 특성에 끼치는 영향이 상용 소프트웨어를 이용하여 해석적으로 조사되었다. 다공튜브 오리피스 면적비 변화는 촉매 전단에 설치된 챔버 내부의 벌크 선회유동 형성과 촉매전단 속도분포의 균일도 지수에 큰 영향을 끼침을 보였다. 해석결과를 검증하기 위해 엔진실험이 ESC 및 ETC 모드에서 수행되었다. 엔진 실험결과 다공튜브 길이방향으로 보다 많은 유량이 흐르는 모델이 가장 높은 NOx 저감 효율을 나타냈으며, 이것은 높은 균일도지수 및 강한 선회유동을 나타내는 해석 결과와 일치됨을 알 수 있었다. A multi-perforated tube is generally installed between the muffler inlet and in front of selective catalytic reduction (SCR) catalysts in the integrated urea-SCR muffler system in order to disperse the urea-water solution spray uniformly and to make better use of the SCR catalyst, which would result in an increase nitrogen oxide (NOx) reduction efficiency and a decrease in the ammonia slip. The effects of the multi-perforated tube orifice area ratios on the internal flow characteristics were investigated analytically by using a general-purpose commercial software package. From the results, it was clarified that the multi-perforated tube geometry sensitively affected the generation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst. To verify the analytical results, engine tests were carried out in the ESC and ETC modes. Results of these tests indicated that the larger flow model in the longitudinal direction showed the highest NOx reduction efficiency, which was a good agreement with the analytical results.
열선유속계와 동적배기유동모사장치를 이용한 배기계 유동 및 유동균일도 해석에 관한 연구
전대일(Daeil Jeon),이강영(Gangyung Lee),황인구(In Goo Hwang),박심수(Simsoo Park) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The CCC (Closed-coupled Catalyst Converter) is important for emission regulations that become stringent, and its distribution has an effect on that. The CCC manifold has complex flow caused by the pulsating flows that are emitted by the exhaust ports. It makes the flow distribution is not uniform. To improve the ability and durability of catalyst, the flow distribution has to be uniform. So measurement of flow distribution is needed. It can be done with computational fluid dynamics. However, such simulations must be verified with experimental data. In this study, conventional manifold of a 4-cylinder engine (with 900 cell CCC system) was performed to investigate the flow characteristic and distribution of exhaust gas. The flow velocity was measured using simulated dynamic flow bench and hot-wire anemometer. The effect of different exhaust ports opening and closing was determined by comparing the flow characteristics.
SCR 촉매 전단에서의 NH₃ 유동균일지수에 따른 NOx 저감률에 관한 수치적 연구
송미지(Miji Song),강석호(Seokho Kang),이성욱(Seangwock Lee),강연식(Yeonsik Kang),조용석(Yongseok Cho) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
The application of SCR systems has been considered an effective exhaust after-treatment method for NOx emission control. Current Urea-SCR systems is possible to achieve 90% NOx if the NH3:NOx ratio is 1:1. However, the reaction has a limited non-uniformity of the exhaust gas flow and ammonia concentration distribution. A uniformity index is developed to evaluate the mixture quality in front of the SCR catalyst, which could also serve as an indirect indication of the de-NOx efficiency of the SCR system. Current papers have been presented the geometrical effects on flow mixing by using 3D Computational Fluid Dynamics (CFD) tool. In this paper, it is presented that the NOx reduction rate has been influenced by the flow uniformity index of NH3 in front of the catalytic converter by using 3D Computational Fluid Dynamics(CFD) tool. In order to achieve uniform flow at monolith front face, we have been changed with a various diffuser angle and mixer blade angle. It is found that the smaller diffuser angle and mixer blade angle are better NH3 uniformity in front of the SCR catalyst.
CFD를 활용한 비상발전기용 PM/NOX 동시저감장치의 유동특성 연구
방효원(Hyowon Bang),박기영(Giyoung Park),유준상(Junsang Yoo),이성욱(Seangwock Lee) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
비상발전기용 디젤엔진은 소방기술기준규칙에 따라 7층 이상, 연면적 2천m² 이상의 건물에 설치하며 주 1회, 무부하 상태에서 30분 이상 운전점검을 수행해야 하는데, 이 과정에서 NO<sub>X</sub>, PM 등의 유해배출물이 다량 발생한다. 산업부 자료에 따르면 비상발전기의 PM 배출량은 1년에 770톤이며, 자동차 배출량의 80%에 이른다고 보고되었다. 현재 도로용 디젤엔진에 사용되는 DOC, DPF, SCR, AOC 등의 배기가스 후처리 시스템을 비상발전기용 엔진에 적용하여 유해배출물을 저감하고 있으나, 운전방식과 상태가 상이하여 비상발전기에 맞는 후처리 시스템 기술개발이 시급하다. 미국 환경청은 비도로용 엔진 배기가스 규제인 EPA 배출가스규제에서 비상발전기의 배출가스를 포함하고 있다. 하지만 비상발전기에 대한 환경규제가 없는 우리나라는 560kW급 이상 대형 비상발전기용 엔진에 대해서는 EPA의 최신 규제 단계인 Tier-4를 만족하는 PM/NO<SUB>X</SUB> 동시저감장치 기술이 없는 실정이다. 규제를 충족하기 위해서는 무부하 상태에서 후처리 시스템의 PM/NO<SUB>X</SUB> 저감 효율과 배압손실을 최적화해야 한다. 본 연구에서는 Tier-4 규제를 만족하는 560kW급 비상발전기용 후처리 시스템 연구를 진행하며, PM/NO<SUB>X</SUB> 동시저감장치는 SCR 전단에서 유동과 암모니아 균일도 확보를 중점으로 하였다. SCR 전단 유동균일도 분석은 CFD 해석법을 이용하여 후처리시스템의 NO<SUB>X</SUB> 저감방법에 대해 연구하였으며, 동시저감장치의 단면 형상, Urea 분사 방향, 믹서 Blade의 배치에 따른 균일도 변화를 분석하였다.
산업용 3상 교반기 내 기체와 고체 입자의 체적 균일도 지수를 활용한 교반 성능 예측
최한호(H. Choi),최종락(J. Choi),허남건(N. Hur),정광훈(G. Jeong),임선영(S. Lim),옥태준(T. Ok) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.3
In this study, transient multiphase flow simulations were carried out to evaluate the new volume uniformity indices of gas and solid particles concentrations within the 3-phase industrial stirred vessel. In the initial state, the solid phase is located at the bottom portion of the vessel with the liquid phase positioned on top. Afterwards, the gas is injected at the middle-section of the vessel from four nozzles and discharged to the top of the vessel and in the process commences the reaction between the liquid and particle phases. To focus on the mixing phenomena, this reaction process was not simulated. A sliding grid technique was adopted to describe the rotating motion of the impellers at three different stages. The mixture flows between gas, liquid, and solid particles were simulated using the Eulerian multiphase model with STAR-CCM+ V.2020.3. Since the conventional method defines volume uniformity indices based on the entire domain, there was a limitation to predict the details of volume uniformity indices of a specific phase. For the above reason, the new volume uniformity indices of the gas and solid particles in the liquid phase were proposed and compared with the conventional method by conducting the 3-phase simulations. The new volume uniformity indices of concentrations were more effective in predicting the degree of mixing level quantitatively. In such a 3-phase flow, the actual mixing degree in the stirred vessel can be determined using the proposed volume uniformity indices of concentration, which can be used to represent the stirring performance.
근접장착식 촉매장치의 유동분포 측정 및 해석에 관한 연구
조용석,김득상,주영철,Jo, Yong-Seok,Kim, Deuk-Sang,Ju, Yeong-Cheol 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.4
In this study, results from an experimental and numerical study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out using a glow measurement system. Flow distribution at the exit of the first monolith in the CCC was measured using a pitot tube under steady and transient flow conditions. Numerical analysis was done using a CF D code at the same test conditions, and the results were compared with the experimental results. Experimental results showed that the uniformity index of exhaust gas velocity decreases as Reynolds number increases. Under the steady flow conditions, flow through each exhaust pipe concentrates on a small region of the monolith. Under the transient flow conditions, flow through each exhaust pipe with the engine firing order interacts with each other to spread the flow over the monolith face. The numerical analysis results support the experimental results, and help explain the flow pattern in the entry region of the CCC.
문남수(Namsoo Moon),이상규(Sangkyoo Lee),이지근(Jeekeun Lee) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.5-1
This study reports a numerical analysis of the internal flow characteristics of the integrated urea-SCR muffler system with the various geometries of the multi-perforated tube which is set up between the muffler inlet and in front of SCR catalysts. The multi-perforated tube is generally used to disperse uniformly the urea-water solution spray and to make better use of the SCR catalyst, resulting in the increased NOx reduction and decreased ammonia slip. The effects of the multi-perforated tube orifice area ratios on the velocity distributions in front of the SCR catalyst, which is ultimately quantified as the uniformity index, were investigated for the optimal muffler system design. The steady flow model was applied by using a general-purpose commercial software package. The air at the room temperature was used as a working fluid, instead of the exhaust gas and urea-water solution spray mixture. From the analysis results, it was clarified that the multi-perforated tube geometry sensitively affected to the formation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst.