요소수(Urea solution)의 온도변화에 따른 요소 및 뷰렛함량 변화 특성 연구

도진우,박태성,이유림,임의순,이정민,강형규 한국응용과학기술학회 2018 한국응용과학기술학회지 Vol.35 No.4

대기오염에 대한 관심이 증대하면서 대기오염물질의 저감에 관한 많은 연구가 진행되고 있다. 차량용 요소수(Urea solution)를 이용한 디젤 차량의 질소산화물(NOx) 제거는 큰 효과를 나타내고 있다. 요소수의 품질은 국내법으로 엄격히 규정하고 있으나 요소수 내 불순물의 증대는 질소산화물 저감 효과를 감소시키게 된다. 따라서 본 연구에서는 일정 온도와 시간동안 요소수를 가열한 후 요소수의 물성변화를 분석하였다. 또한, 요소수를 보관하는 저장용기와 저장온도의 변화에 따른 요소수 물성변화도 함께 분석하 였다. 요소수를 일정시간 가열한 후 요소수 내 뷰렛함량은 증가하고 요소함량은 감소하였으며, 요소함량 감소에 따라 밀도와 굴절률도 함께 감소하였다. 철제 및 PET 용기와 일정온도(30 ℃, 50℃)에서 실시한 저장안정성 시험에서는 물성변화가 나타나지 않았다. As interests in the air pollution increases, many kinds of researches are underway on the reduction of air pollutants. Removal of nitrogen oxides from the emission gas of diesel vehicles using urea solution has shown a great effect. The quality of urea solution is strictly defined by domestic laws, but the increase of impurities in urea solution reduces the effect of reducing nitrogen oxides. Therefore, in this study, the change of physical properties of urea solution was analyzed after heating the urea solution for a certain temperature and time. Also, the changes of physical properties of urea solution were analyzed according to kinds of storage container and temperature for storing the urea solution. After heating the urea solution for a certain period of time, the biuret content in urea solution increased and the content of urea decreased. As the urea content decreased, both density and refractive index decreased. In the storage stability test carried out at a constant temperature with iron and PET containers, no change in physical properties was observed.

냉각수 순환 가열 방식을 이용한 요소수의 동결 및 해동 특성에 관한 수치적 연구

이승엽(Seung Yeop Lee),김남일(Nam Il Kim),박윤범(Yun Beom Park),김만영(Man Young Kim) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.8

Urea-SCR은 동절기, 북유럽과 북미지역과 같은 -20℃ 이하의 환경에서 요소수가 동결되는 문제점을 해결해야 한다. 따라서 이러한 요소수 저장탱크에 해동 시스템을 적용하여 시동 초기, 요소수를 적정 시간 내 분사하기 위한 기술의 확보가 필요하다. 본 연구에서는 저장탱크 내 요소수의 동결현상과 냉각수 순환 가열방식을 적용한 해동현상에 대하여 상용 소프트웨어인 Fluent 6.3을 이용하여 3차원 비정상상태 수치해석을 수행하였다. 이를 통하여 요소수의 동결 및 해동과정 중 나타난 온도분포, 상경계면, 그리고 액상분율을 분석하여 열전달 특성을 고찰하였다. 결론적으로 요소수의 동결은 저장탱크 벽면으로부터 중심부로 이루어졌으며, 해동현상은 순환 파이프와 인접할수록 요소수의 상변화가 빠르게 진행하였다. 또한, 냉각수의 70℃, 200ℓ/h 조건에서 1ℓ의 액상 요소수를 얻는데 약 190초의 시간이 필요하였다. Urea-SCR technology is known as one of the powerful NOx reduction systems for vehicles as well as stationary applications. For its consistent and reliable operation in vehicle applications, however, the freezing and melting of the urea solution in cold environments have to be resolved. In this study, therefore, a numerical study of three-dimensional unsteady problems was analyzed to understand the urea freezing and heating phenomena and heat transfer characteristics in terms of urea liquid volume fraction, temperature profiles, and phase change behavior in urea solutions with time by using the commercial software Fluent 6.3. As a result, it was found that the freezing phenomenon proceeds with a phase change from the tank wall to the center, whereas the melting phenomenon occurs faster in the upper part of the storage tank by natural convection and in the adjacent part of the coolant pipe than in other parts. Furthermore, approximately 190 s were required to obtain 1L of urea solution using a 4-coiled coolant heater under conditions of 70°C and 200 L/h.

자동차 냉각수를 이용한 요소수 가열 시스템 성능 분석

박준수 ( Jun Su Park ),전문수 ( Mun Soo Chon ),추성화 ( Seong-hwa Choo ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-

The urea system is used for reducing the NOx emission in the diesel engines. The NOx reduction efficiency is influenced by the urea temperature. Therefore, the urea cooling and heating system is applied in the urea supply system. And the coolant of vehicle is used for the heat source. This study has predicted urea temperature distributions of the urea supply line that is heated by the vehicle coolant. The urea supply line is composed the double wall structure to heat exchange from vehicle coolant to urea. The vehicle coolant temperature is 80℃ and the urea inlet temperature is 60℃. This study performed the numerical analysis using ANSYS CFX v.16 to predict the urea outlet temperature. The urea outlet temperature rise very little due to the urea tube material which is very low conductivity.

미립화 및 분무장치 2 : Urea-SCR 배관 내의 요소수의 해동 특성에 관한 수치적 연구

박준수 ( Jun Su Park ),전문수 ( Mun Soo Chon ),추성화 ( Seong-hwa Choo ),최정기 ( Jeong Gi Choi ) 한국액체미립화학회 2015 한국액체미립화학회 학술강연회 논문집 Vol.2015 No.-

Urea-SCR technology is used for reducing NOx emission in the vehicles. Ensuring the reliability of Urea-SCR system, freezing and melting problem of urea solution should be resolved. Especially, the melting time of urea is very important to operate vehicle normally in the winter season. Therefore, this study performs a numerical study to understand and predict the urea coolant melting phenomena. To evaluate the effect of heating voltage, we give to the different heating voltage on the heater line and compare the urea melting time. Ansys mechanical, which is commercial numerical software, is used for investigate the urea coolant melting phenomena. As a result, The temperature difference in the urea coolant is not over 1℃during melting process. And the urea melting time of urea depends on the heating voltage. When the heating voltage increases linearly, the melting time of urea decreases exponentially.

소형 상용차용 전기 가열 모듈에 의한 동결 요소수의 해동 및 열전달 특성에 관한 수치적 연구

이두기(Doo Ki Lee),김만영(Man Young Kim),오광철(Kwang Chul Oh),노태수(Tae Soo No) 대한기계학회 2019 大韓機械學會論文集B Vol.43 No.3

배기가스 후처리장치 중 하나인 Urea-SCR은 NOx 규제 대응을 위한 우수한 장치로 평가받고 있다. 하지만 환원제로 사용되는 요소수는 –20℃ 이하 저온 환경에서 동결되는 문제가 있다. 따라서 고상의 동결 요소수를 액상으로 원활하게 공급하기 위해서는 가열이 필수적이며, 해동 과정에서 상변화와 함께 물질의 물리적 특성 변화가 수반된다. 본 연구에서는 상용코드 ANSYS Fluent를 이용하여 동결 요소수의 해동에 관한 3차원 비정상 상태 수치해석을 수행하였다. 수치해석의 검증과 함께 시간에 따른 액상 분율의 변화, 상 경계면의 이동 및 온도 분포를 통해 요소수의 해동 및 열전달 특성을 고찰하였고, 향후 전기 가열 모듈을 포함한 요소수 공급 모듈의 최적 설계를 위한 기초 데이터를 확보하였다. The Urea-SCR, one of the exhaust gas after-treatment devices, is regarded as the most device for NOx regulation. However, a challenging problems is to ensure that the urea-water solution used as a reducing agent is available for operating the system in a cold environment. The urea thawing process, in which the solid turns to liquid, is associated with the phase change and physical property change phenomena. In this study, therefore, the commercial software ANSYS Fluent was utilized to conduct a numerical analysis in order to investigate the urea thawing process, including a complex solid-liquid phase change with the electric heating module. After validating the numerical methods adopted in this work, the thermal characteristics, such as variation of the liquid fraction and temperature distribution with time, were investigated as potential basic data for optimum design.

승용 디젤차량에서 Urea-SCR 시스템의 NOx 저감 특성에 관한 실험적 연구

박승원(Seungwon Park),이성욱(Seangwock Lee),조용석(Yongseok Cho),강연식(Yeonsik Kang) 대한기계학회 2017 大韓機械學會論文集B Vol.41 No.4

LNT(Lean NOx Trap), LNC(Lean NOx Catalyst), SCR(Selective Catalytic Reduction)과 같은 NOx 저감기술은 상용차뿐만이 아닌 승용차량 성능향상을 위해 지속적으로 개발이 진행되고 있다. 특히 Urea-SCR 시스템은 연료손실 없이 이론상 100%에 가깝게 NOx를 저감하는 가장 효과적인 기술로 환원반응으로 배기가스를 N₂와 H₂O로 배출하기 위해 환원제인 요소수를 분사해야한다. 하지만 엔진에서와는 달리 실제차량에서의 적용은 SCR 효율이 떨어지게 된다. 따라서 실제차량에서의 SCR 효율을 극대화하는 기술개발이 요구되고 있는 실정이다. 본 연구에서는, Post EURO-6 배기가스 규제에 대응하기 위한 디젤승용차량에서의 Urea-SCR의 NOx 저감 성능에 의한 저감효율의 극대화를 목적으로 실차용 Urea-SCR 시스템위한 기초자료로 제시하고자 한다. NOx reducing technique such as LNT, LNC , and selective catalytic reduction (SCR) have been developed and applied, especially on heavy-duty vehicles. However, it is expected that NOx reduction techniques will also be applied to diesel passenger vehicles. The urea-SCR system is receiving attention as the most effective NOx reduction technology without a fuel penalty. Thus, many advanced countries are developing this technology. The urea-SCR system sprays an aqueous urea solution that separates NOx into N₂ and H₂O, which are harmless and emitted into the atmosphere. The urea injected in front of the SCR catalyst should be changed to 100% NH₃, which is required for NOx reduction in the SCR system to maximize the reduction efficiency. The purpose of this study was to determine the basic data for the urea-SCR system to maximize the NOx reduction efficiency by understanding the NOX reduction characteristics in a real passenger vehicle to comply with the post EURO-6 emission regulation.

냉각수 순환 가열 방식을 이용한 요소수의 동결 및 해동 특성에 관한 수치적 연구

이승엽(Seung Yeop Lee),김만영(Man Young Kim) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.5-2

Urea-SCR technology, which converts nitrogen oxides in exhaust gases to nitrogen and water in the presence of a reducing agent, usually AdBlue™ urea solution, is known as one of the powerful NOX reduction systems for vehicle as well as stationary applications. For its consistent and reliable operation in vehicle applications, however, such various problems as ammonia slip, transient injection, and freezing and melting in cold environments have to be resolved. In this work, therefore, numerical study on three-dimensional unsteady problems were analyzed to find the urea freezing and heating phenomena and heat transfer characteristics in terms of urea liquid volume fraction, temperature profiles, and phase change behavior in urea solutions with time by using the commercial software Fluent 6.3. After validating present solutions by comparing with experimental data, parametric investigations are conducted with -30℃ freezing urea solution in 34 storage tank with and 4-coiled coolant heater. Finally, it can be found freezing ℓ phenomena is proceeded by phase change from the tank wall to center, while melting phenomena occurs faster in the upper part of storage tank by natural convection and adjacent part of coolant pipe than other parts. Also, it took approximately 700s to obtain urea solution of 1ℓ with 4 coiled coolant heater with conditions of 70℃and 200 ℓ/h.

요소수 인젝터의 작동 변수에 따른 분무미립화 성능에 관한 연구

김동환,박준규,박성욱 한국분무공학회 2019 한국액체미립화학회지 Vol.24 No.1

This study was carried out to analyze the spray characteristics as a function of the operating parameters of urea injector used in Urea-SCR system of passenger diesel vehicle. Spray visualization and PDPA experiment were performed to analyze the macroscopic spray development and atomization performance of urea-water-solution. For the urea injector, the deformation of the spray head does not appear to be significant because it operates at a low pressure conditions, and the liquid core and primary droplet are observed throughout the operating conditions. No increase in atomization is seen when the operating pressure is increased, and the spray develops linearly due to poor atomization characteristics. The macroscopic spray behavior of the low-pressure urea injector is predictable through the modification of the Hiroyasu equation.

승용 디젤기관에서 Urea-SCR 시스템의 NOX 저감 및 NH₃ slip 특성에 관한 실험적 연구

백윤도(Youndo Baek),김종민(Jongmin Kim),박승원(Seungwon Park),이성욱(Seangwock Lee),조용석(Yongseok Cho),강연식(Yeonsik Kang) 한국자동차공학회 2015 한국자동차공학회 학술대회 및 전시회 Vol.2015 No.11

The regulation of harmful emission including CO₂ is getting more strict recently according to greenhouse gases problem caused by increasing of CO₂ emission. The Diesel engine provides many positive aspect such as higher thermal efficiency and less CO₂ emission. However, there are some problem on PM(Particulate Matters) and NOX emissions. PM has decreased by around 90% according to development of DPF technology. NOX reducing technique such as LNT, LNC, SCR has been developed and applied especially on heavy duty vehicle. But it is expected the NOX reducing technique is applied on passenger diesel vehicle, as well. The Urea-SCR system is getting attention as the most effective NOX reducing technology without fuel efficiency incline, so that many advanced countries are developing this technology. Urea-SCR system sprays Urea- aqueous solution to take apart into N₂ and H₂O and emit into the atmosphere as reducing agent which is harmless. Injected Urea in front of SCR catalyst should be changed to NH₃ 100% required for NOX reduction in SCR system to maximize reducing efficiency. In this study, it is purpose to look for the α ratio before the NH₃ slip at the load of engines by performance of the catalyst to find the maximum reduction rate of NOX. The α-ratio in the Urea-SCR system will be at one to one ratio by recognizing the NOX value in general. However, it is possible to inject NH₃ more by occlusion performance of the catalyst at the temperature condition so that there will be much reaction. As a result, there will be effect to improve the reduction rate of NOX. Therefore, it is able to exert much improved maximum performance the reaction of Urea-SCR by injecting NH₃ more as the α ratio before slipping to match the performance of the catalyst. Thus it becomes the injection strategy to reduce the nitrogen oxide. In conclusion, it is possible to create not only the exhaust regulations Euro-6 but also the Urea-SCR which satisfies Post Euro-6.

Urea-SCR 촉매가 코팅되는 전기히터 시스템의 NOx저감 성능에 관한 연구

최현하(Huunha Choi),김홍석(Hongsuk Kim),정용일(Yongil Jeong),임인혁(In-hyuk Im),박정한(Jeonghan Park),황재원(Jae-Won Hwang) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

It is well known that a urea-SCR system can reduce NOx emissions of a diesel engine effectively. But the urea-SCR technology does not shows a good NOx reduction performance at low temperature exhaust gas conditions. This study introduces a newly developed urea-SCR catalyst coated electrical heater system. This system can reduce NOx emissions of a diesel engine effectively even though at low temperature exhaust gas conditions by increasing the surface temperature of SCR catalyst electrically. The study compares the NOx reduction performance of the newly developed urea-SCR system with a conventional system. This study shows that the new urea-SCR system has high performance and low NH₃ slip at the low temperature exhaust gas conditions.