• 제목/요약/키워드: Urea-SCR System

검색결과 90건 처리시간 0.021초

Analysis of an internal flow with multi-perforated tube geometry in an integrated Urea-SCR muffler (다공튜브 형상변화에 따른 촉매 삽입형 Urea-SCR 머플러 내부유동 해석)

  • Moon, Namsoo;Lee, Sangkyoo;Lee, Jeekeun
    • Journal of Advanced Marine Engineering and Technology
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    • 제37권5호
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    • pp.500-509
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    • 2013
  • 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 $NO_x$ 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.

An Experimental Study of Nano PM Emission Characteristics of Commercial Diesel Engine with Urea-SCR System to Meet EURO-IV (상용디젤엔진의 EURO-IV 배기규제 대응을 위한 Urea-SCR 시스템의 나노입자 배출특성에 관한 실험적 연구)

  • Lee, Chun-Hwan;Cho, Taik-Dong
    • Transactions of the Korean Society of Automotive Engineers
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    • 제15권6호
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    • pp.128-136
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    • 2007
  • It is well known that two representative methods satisfy EURO-IV regulation from EURO-III. The first method is to achieve the regulation through the reduction of NOx in an engine by utilizing relatively high EGR rate and the elimination of subsequently increased PM by DPF. However, it results in the deterioration of fuel economy due to relatively high EGR rate. The second is to use the high combustion strategy to reduce PM emission by high oxidation rate and trap the high NOx emissions with DeNOx catalysts such as Urea-SCR. While it has good fuel economy relative to the first method mentioned above, its infrastructure is demanded. In this paper, the number distribution of nano PM has been evaluated by Electrical Low Pressure Impactor(ELPI) and CPC in case of Urea-SCR system in second method. From the results, the particle number was increased slightly in proportion to the amount of urea injection on Fine Particle Region, whether AOC is used or not. Especially, in case of different urea injection pressure, the trends of increasing was distinguished from low and high injection pressure. As low injection pressure, the particle number was increased largely in accordance with the amount of injected urea solution on Fine Particle Region. But Nano Particle Region was not. The other side, in case of high pressure, increasing rate of particle number was larger than low pressure injection on Nano Particle Region. From the results, the reason of particle number increase due to urea injection is supposed that new products are composited from HCNO, sulfate, NH3 on urea decomposition process.

A Study on the Distribution of Injected Urea into the Exhaust Pipe in a SCR System (선택적 환원촉매(SCR)장치에서 배기관내에 분사된 환원제 분포에 관한 연구)

  • Choi, J.H.;Lee, Y.C.;LEE, S.W.;Cho, Y.S.;LEE, S.H.;Oh, S.K.;Dong, Y.H.
    • Journal of Power System Engineering
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    • 제14권1호
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    • pp.16-21
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    • 2010
  • This research focused on the spray and distribution characteristics of urea solution by applying flow visualization techniques and did durability and driver test on injectors as well. The spray characteristics of urea solution was observed by CCD camera. Also, the distribution characteristics of urea solution was evaluated quantitatively as well by using 3D laser scanner equipment. It was considered that it was reasonable to use the injector for gasoline engine in order to inject the urea. The best distribution chart result was observed near 45cm distance difference between catalyst and urea spray injector. As a result of trapped urea distribution chart analysis, optimal pressure and volumetric flow rates of air and urea were derived in order to improve the distribution of Urea. This information may contribute to provide fundamental data in the future.

Effect of Atomization Characteristics of Twin Fluid Nozzle on Urea Pyrolysis (이유체 노즐 미립화 특성이 요소 열분해에 미치는 영향)

  • Ku, Kun Woo;Chung, Kyung Yul;Yoon, Hyun Jin;Seok, Ji Kwon;Hong, Jung Goo
    • Journal of ILASS-Korea
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    • 제20권3호
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    • pp.162-167
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    • 2015
  • Recently, there has been rising interest in applying urea-SCR systems to large marine diesel engines because the International Maritime Organization (IMO) has decided to enforce NOx reduction regulations. Generally, in the case of urea-SCR of the marine diesel engine, a type of twin fluid atomizer has been using for injection of the urea solution. This study conducted to investigate an effect of the atomization of external-mixing twin fluid nozzle on the conversion efficiency of reductant. The lab-scaled experiment device was installed to mimic the urea-SCR system of the marine diesel engine for this study. In a low temperature inflow gas condition which is similar with the exhaust temperature of large marine diesel engine, this study found that the conversion efficiency of reductant of when relative big size urea solution droplets are injected into exhaust gas stream can be larger than that of when small size urea solution droplets are injected. According to results of this study, the reason was associated with decrease of reaction rate constant caused from temperature drop of inflow gas by assist air of twin fluid atomizer.

Experimental Study on Spray Characteristics of Twin Fluid Nozzle in Urea-SCR (Urea-SCR에 적용되는 이유체 노즐의 분무특성에 관한 실험적 연구)

  • Park, Hyung Sun;Hong, Jung Goo
    • Journal of ILASS-Korea
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    • 제22권2호
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    • pp.96-102
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    • 2017
  • In order to reduce the NOx, SCR technology is most suitable. In this study, we focused on studying the injector part of urea-SCR system. When stoichiometric 1 mole of urea is injected, 2 moles of $NH_3$ are created. $NH_3$ causes a SCR reaction by reacting with NOx. However, urea is decomposed by the side reaction of coming out HNCO, deposit formation is formed. In this study, it was to design a nozzle that can spray the optimal spray flow rate. Test nozzle used in this experiment is efferverscent type. The result of the experiment, liquid flow rate was confirmed to be that they are dominated by the exit orifice diameter. The area ratio is defined by ratio of the area of exit orifice hole and that of aerorator. The droplet size was measured by varying the area ratios. In addition, it was also confirmed that there is no change of the liquid flow rate and air flow rate to change the aerorator at the same exit orifice. Further, It was confirmed that the droplet size was relatively uniform even though the area ratio was different. Finally, there is little change in the SMD that air flow rate increases in 0.3 or more ALR.

Experimental Study on Mixing Efficiency of Exhaust Gas and Reductant According to SCR Mixer Shape (SCR 믹서형상에 따른 배기가스와 환원제 혼합 효율에 관한 실험적 연구)

  • Choe, Munseok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • 제22권3호
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    • pp.74-79
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    • 2021
  • This study examined the mixing efficiency of exhaust gas and urea according to the mixer shape in the SCR system. For the experiment, an SCR simulation system was manufactured, and a uniformity detector was attached to the catalyst location to measure the uniformity. The experiment was conducted by setting the exhaust-gas flow rate, temperature, mixer type, and catalyst distance as variables. The experimental results confirmed the swirl angle analysis, urea number distribution, and uniformity. The swirl angle experiment of Models A and B confirmed that the swirl angle of Model A was formed approximately 7 to 8 degrees higher over the entire RPM range. When there was no mixer in the SCR system, the urea and water were concentrated to one side. Mixer Model A showed an even distribution overall, and Model B showed a slightly concentrated tendency at the beginning but then showed a stable distribution of urea. The mixing efficiency of 90%, which was the uniformity target, could be satisfied in Model A and Model B. In particular, Model A showed excellent results that satisfied 90% efficiency at 10 cm of the catalyst position.

Numerical Investigation of the Spray Behavior and Flow Characteristics of Urea-Water Solution Injected into Diesel Exhaust Pipe (디젤 배기관에 분사된 우레아 수용액의 분무 거동 및 유동 특성에 관한 연구)

  • An, Tae Hyun;Kim, Man Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • 제38권1호
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    • pp.41-48
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    • 2014
  • 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.

Effect of NH3 Uniformity Index on SCR System According to Urea Spray Characteristics (요소수 분무특성이 SCR시스템 내 분무균일도에 미치는 영향)

  • Kim, Se Hun;Ko, Jin Seok;Ko, Jae Yu;Cho, Young Jun;Lee, Dong Ryu
    • Journal of ILASS-Korea
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    • 제24권4호
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    • pp.178-184
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    • 2019
  • Diesel engines have the advantages of higher thermal efficiency and lower CO2 emissions than gasoline engines, but have the disadvantages that particulate matter (PM) and nitrogen oxides (NOx) emissions are greater than those of gasoline engines. In particular, nitrogen oxides (NOx) emitted from diesel engines generates secondary ultrafine dust (PM2.5) through photochemical reactions in the atmosphere, which is fatal to humans. In order to reduce nitrogen oxides (NOx), pre-treatment systems such as EGR, post-treatment systems such as LNT and Urea SCR have been actively studied. The Urea SCR consists of an injection device injecting urea agent and a catalytic device for reducing nitrogen oxides (NOx). The nitrogen oxide (NOx) reduction performance varies greatly depending on the urea uniformity in the exhaust pipe. In this study, spray characteristics according to the spray hole structure were confirmed, and the influence of spray uniformity on spray characteristics was studied through engine evaluation.

1-D Modeling of Heater Surface Temperature Distribution in EHC-based Urea-SCR System (EHC 기반 Urea-SCR 시스템 히터 표면온도 분포의 1-D 모델링)

  • Park, Sunhong;Son, Jihyun;Moon, Seoksu;Oh, Kwangchul;Jang, Sungwook;Park, Sungsuh
    • Journal of ILASS-Korea
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    • 제27권1호
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    • pp.11-17
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    • 2022
  • In upcoming Post Stage-V and Tier 5 regulations of construction machineries, nitrogen oxide (NOx) emissions are strictly limited in cold start conditions. In response to this, a method of improving NOx conversion efficiency has been applied by installing an electric heating catalyst (EHC) in front of conventional urea-SCR systems so that the evaporation and thermal decomposition of urea-water solution can be promoted in cold start conditions. In this strategy, the evaporation and thermal decomposition of urea-water solution and corresponding NOx conversion efficiency are governed by temperature conditions inside the EHC. Therefore, characterizing the temperature distribution in the EHC under various operating conditions is crucial for the optimized operation and control of the EHC in Urea-SCR systems. In this study, a 1-D modeling analysis was performed to predict the heater surface temperature distribution in EHC under various operating conditions. The reliability of prediction results was verified by comparing them with measurement results obtained using an infrared (IR) camera. Based on 1-D analysis results, the effects of various EHC operation parameters on the heater surface temperature distribution were analyzed and discussed.

A Study on $NO_x$ Reduction in a Light Duty Diesel Vehicle Equipped with a SCR Catalyst (선택적환원촉매를 적용한 중소형 경유차량의 질소산화물 저감 특성 연구)

  • Park, Young-Joon;Hong, Woo-Kyoung;Ka, Jae-Geum;Cho, Yong-Seok;Joo, Jae-Geon;Kim, Hyun-Ok
    • Transactions of the Korean Society of Automotive Engineers
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    • 제19권5호
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    • pp.118-124
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    • 2011
  • To reach the Euro-6 regulations of PM and $NO_x$ for light-duty diesel vehicles, it will be necessary to apply the CDPF and the de-$NO_x$ catalyst. The described system consists of a catalytic configuration, where the CDPF is placed downstream of the diesel engine and followed by a urea injection unit and a urea-SCR catalyst. One of the advantages of this system configuration is that, in this way, the SCR catalyst is protected from PM, and both white PM and deposits become reduced. In the urea-SCR system, the injection control of reductant is the most important thing in order to have good performance of $NO_x$ reduction. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency become slower, due to temperature window of SCR catalyst. And space velocity also affects to $NO_x$ conversion efficiency. In this paper, rig-tests were performed to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the urea-SCR system. And vehicle test was performed to verify control strategy of reductatnt injection. The developed control strategy of reductant injection was improved over all $NO_x$ reduction efficiency and $NH_3$ consumption in urea-SCR system. Results of this paper contribute to develop urea-SCR system for light-duty vehicles to meet Euro-5 emission regulations.