모사 배기관 내 요소수 열분해에 관한 연구

구건우 ( Kun Woo Ku ),박홍민 ( Hong Min Park ),홍정구 ( Jung Goo Hong ) 한국액체미립화학회 2014 한국액체미립화학회 학술강연회 논문집 Vol.2014 No.-

The urea decomposition in the urea-SCR system is generated under the multiphase flow field coexisting with the injected urea solution droplets in liquid phase, the inflow gas in gas phase and solid urea particles. For this reason, the urea decomposition is closely connected with thermo-fluid dynamics as well as various chemical reactions. An experimental study was performed to investigate the urea decomposition under various thermo-fluid conditions such as the temperature and velocity of inflow gas and the urea solution quantity. These inflow gas conditions were similar with the exhaust conditions of the large marine engine. The urea solution injector of twin fluid type was designed and also the lab-scaled exhaust system was designed to control the temperature and velocity of inflow gas. The spray performance of designed urea solution injector was almost identical under all the experiment conditions. This means that the spray`s effect on the urea decomposition must be minimized. The total conversion efficiency considered with both ammonia and HNCO was closely related with the urea injection quantity and convective heat transfer of inflow gas as well as the temperature of inflow gas. The conversion efficiency of ammonia was larger than that of HNCO under all experimental conditions unlike the theoretical thermolysis reaction. The difference between conversion efficiency of ammonia and HNCO was also affected by convective heat transfer and urea injection quantity as well as the temperature of inflow gas.

Urea-SCR 인젝터의 미립화 성능에 대한 실험적 연구

구건우(Kun Woo Ku),김성열(Sung Ryoul Kim),박종원(Jong Won Park),이충원(Choong Won Lee),홍정구(Jung Goo Hong),강명권(Myung Kweon Kang),김경남(Kyung Nam Kim),김재경(Jae Kyoung Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

본 연구는 비교적 저압의 분사압력에서도 우수한 미립화 특성을 가지는 스월 인젝터를 Urea-SCR 시스템에 적용하기 위한 기초연구로서, 스월 인젝터의 SMD, 분무각, 액막의 분열과 같은 분무특성을 조사하였다. 그 결과를 정리하면 다음과 같다. 1. 스월 인젝터의 분무 형상은 분무가 진행됨에 따라 hollow cone 에서 solid cone 으로 변하였다. 노즐의 설계가 액막의 분열 특성에 영향을 끼치는 것으로 생각된다. 2. 분무각은 분사압력이 증가함에 따라 증가하였으며, 니들의 구동이 분무각에 영향을 끼쳤다. 분사압력에 상관 없이 분사 시작 후 initial jet 가 관찰되었으며, injection delay time 는 동일하였다. 3. 분무선단거리에 따른 SMD 는 분사압력이 증가함에 따라 감소하였다. 특히 분사압력 7.5bar 와 10bar 에서는 분무선단거리를 따라 SMD 가 증가한 후 다시 감소하는 구간이 나타났다. In this study, a swirl hollow cone injector, which has a good atomization performance at the low injection pressure relatively, was designed to apply the Urea-SCR. In order to investigate the spray pattern and SMD of a swirl injector, the spray visualization was conducted by using the simplex swirl injector, and the images of the spray cross-section were obtained from a sheet beam ofNd-Yag laser and a CCD camera. The SMD of the swirl injector was measured with the axial distance from the nozzle exit. The shape of the spray is converted from the hollow cone to solid cone along the distance from the injector exit. The spray angle is increased and the SMD is decreased with increasing injection pressure respectively

SCR 촉매에서 Sherwood number 와 질소산화물 제거 효율의 상관관계

구건우 ( Kun Woo Ku ),박진우 ( Jin Woo Park ),박삼식 ( Sam Sik Park ),홍정구 ( Jung Goo Hong ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-

NOx is controlled to reducing the harmful components in the exhaust gas. So Marine Environment Protection Committee (MEPC) take effect `Tier Ⅱ `, `Tier Ⅱ ` of air pollution regulation in 2005 and 2011 respectively. According to NOx emissions are strictly regulated management of the vessel through them. In addition, since 2016 the regulation enter into force in the next step `Tier Ⅰ ` was confirmed by MEPC 66^th committee. It`s 80% enhanced emissions limits than the `Tier Ⅲ ` Alternatively these emission regulation, research is actively being carried out about exhaust gas after-treatment methods through the vessel application of Selective Catalytic Reduction(SCR). Therefore depending on the basic specification of cell density according to the area velocity, space velocity, linear velocity is studied the effects of NOx removal efficiency and the relationship of non-dimensional analysis for optimize the application of SCR system to the vessel.

저온 반응장에서 요소 수용액의 환원제 전환에 관한 실험적 연구

구건우 ( Kun Woo Ku ),홍정구 ( Jung Goo Hong ) 한국분무공학회 2015 한국액체미립화학회지 Vol.20 No.1

Urea-SCR which is one of the aftertreatment technologies for reducing the NOx emission is widely used. An experimental study was performed to investigate urea decomposition under various thermo-fluid conditions, with different temperatures and velocities of inflow gas, and urea solution quantities. 40 wt. % aqueous urea solutions were used in this study. The inflow gas conditions were similar to the exhaust conditions of a large marine engine. The spray performance of urea solution injec- tor was identical under all experimental conditions. The conversion efficiency of NH3 was larger than that of HNCO under all experimental conditions, unlike for the theoretical thermolysis reaction.

250 ℃ 이하 배기관에서 우레아 수용액의 암모니아 전환율 특성에 관한 실험적 연구

구건우(Kun Woo Ku),박홍민(Hong Min Park),홍정구(Jung Goo Hong) 대한기계학회 2015 大韓機械學會論文集B Vol.39 No.2

디젤 엔진과 산업용 보일러에서의 질소산화물(NOx) 배출은 환경오염을 유발시키는 주요물질 중의 하나이다. 이러한 질소산화물 발생을 저감시키기 위한 방법으로 후처리 기술 중의 하나인 우레아 선택적 촉매 환원(Urea-SCR)기술이 널리 사용되고 있다. 본 연구에서는 선박용 디젤엔진의 배기가스 조건을 모사한 실험실 스케일의 실험장치를 통해 우레아 수용액의 열분해 특성에 대해 고찰하였다. 40 wt. %의 우레아 농도를 가진 우레아 수용액을 사용하였고, 모사가스의 온도와 유속변화, 우레아 수용액의 유량에 따른 총 전환율 뿐만 아니라 암모니아(NH3)와 이소시안산(HNCO)의 전환율 차이를 알아보았다. 210 ℃와 250 ℃ 모사가스 온도에서 체류시간에 따라 암모니아의 전환율이 이소시안산의 전환율보다 높게 나타남을 확인하였다. The NOx emissions from diesel engines and industrial boilers are a major cause of environmental pollution. The selective catalytic reduction of urea is an aftertreatment technology that is widely used for the reduction of NOx emissions. The objective of this study was to investigate the characteristics of the thermal decomposition of a urea aqueous solution using laboratory-scale experimental equipment under conditions similar to those of marine diesel engines. A 40 wt. urea aqueous solution was used in this study. It was found that the total conversion rate varied with the inflow gas conditions and flow rates of the urea aqueous solution. In addition, there were conversion rate differences between NH3 and HNCO. At inflow gas temperature conditions of 210 ℃ and 250 ℃, the NH3 conversion rate was found to be higher than that of the HNCO, depending on the residence time.

원형 및 타원형 노즐 내부유동과 외부유동의 상관관계

구건우(Kun Woo Ku),홍정구(Jung Goo Hong),박철우(Cheol Won Park),이충원(Choong Won Lee) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.3

원형 및 타원노즐의 내부유동과 외부유동의 상관관계를 알아보기 위해 실험적 연구가 수행되었다. 분사압력에 따라 유량, 분무각, 액적크기 등의 외부유동에 관해 관찰하였고, 노즐 내부유동의 유속 및 압력분포 등을 수치해석을 통해 정량적인 결과를 도출하였다. 외부유동의 경우, 동일한 압력조건하에서 타원형 노즐의 경우, 원형 노즐에서 나타나지 않는 표면분열의 분무특성을 관찰할 수 있었고, 수치해석을 통해 노즐 내부의 유동을 분석한 결과, 원형의 경우와는 달리 타원형 노즐의 단축에서 내부유동의 재부착이 노즐 벽면에서 발생되었다. 타원노즐 외부유동의 표면분열이 내부유동에 따른 결과라고 판단된다. An experimental study was carried out to determine the correlation between the internal flow in a circular nozzle and elliptical nozzles with the external flow. The flow rate, spray angle and drop size were measured under various conditions of the injection pressure. Numerical simulations were attempted to investigate the internal flow structure in the elliptical nozzles, because the experimental study was limited in its measurements of flow velocity and pressure distributions in the relatively small orifice. In the case of the elliptical nozzles, the disintegration characteristics of the liquid jet were significantly different from those of the circular nozzle. Surface breakup was observed at the jet issued from the elliptical nozzles with injection pressure. This is due to the internal flow structure, which is reattached to the orifice wall at the minor axis plane of the elliptical nozzle, unlike that observed with the circular nozzle.

이유체 노즐 미립화 특성이 요소 열분해에 미치는 영향

구건우 ( Kun Woo Ku ),정경열 ( Kyung Yul Chung ),윤현진 ( Hyun Jin Yoon ),석지권 ( Ji Kwon Seok ),홍정구 ( Jung Goo Hong ) 한국액체미립화학회 2015 한국액체미립화학회지 Vol.20 No.3

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.

디젤엔진에서 노즐 홀 형상효과의 실험적 연구

구건우 ( Kun Woo Ku ),이영진 ( Young Jin Lee ),김인수 ( In Su Kim ),이충원 ( Choong Won Lee ) 한국분무공학회 2007 한국액체미립화학회지 Vol.12 No.3

원형 노즐과 타원형 노즐에서 발생되는 캐비테이션 유동

구건우(Kun Woo Ku),홍정구(Jung Goo Hong),이충원(Choong Won Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.10

본 연구의 목적은 원형과 타원형 노즐에 발생되는 캐비테이션 유동에 대해 수치 계산을 통해 각각의 특성을 파악하는 것이다. 수치해석을 위해 상용코드인 FLUENT 6.2 을 사용하였고, 실험결과의 캐비테이션 형태와 수치계산에서 얻은 결과를 비교함으로써 계산결과의 타당성을 확인하였다. 주목할만한 결과로는 원형 노즐 내부의 캐이테이션 형상은 노즐 축방향으로 대칭적인 원통형을 가지는 반면, 타원형 노즐의 경우 장축의 캐이테이션 길이가 단축의 캐이테이션 길이보다 긴 말발굽 (horseshoe) 형태가 관찰되었다. 또한, 타원형 노즐의 경우 오리피스의 반경방향 속도는 오리피스의 장, 단축에서 확연히 다른 분포가 관찰되었다. The purpose of this study was to investigate the internal nozzle flow and cavitation characteristics numerically in both circular and elliptical nozzles. The program FLUENT 6.2 was used to perform the numerical simulation of the cavitating flow in the nozzles. A comparison was made between the cavitation shapes predicted numerically and those found experimentally in order to validate the numerical solution. This study showed that the cavitation in the circular nozzle had a cylindrical shape that was symmetrical with the nozzle axis. However, the cavitation in the elliptical nozzles had a horseshoe-like shape. In addition, the radial velocity distribution varied between the major and the minor axis planes when the working fluid was flowing into the inlet.

SCR 촉매의 공간속도 및 선속도가 NOx 제거 효율에 미치는 영향

박진우 ( Jin-woo Park ),박삼식 ( Sam-sik Park ),구건우 ( Kun Woo Ku ),홍정구 ( Jung Goo Hong ) 한국액체미립화학회 2016 한국액체미립화학회지 Vol.21 No.2

Air pollutants nitrogen oxides are inevitably generated in the combustion reaction. Its amount trend is steadily increasing because the rapid modern industrialization and population growth. For this reason, NOx is controlled to reducing the harmful components in the exhaust gas. So Marine Environment Protection Committee (MEPC) take effect ‘Tier I’, ‘Tier II’ of air pollution regulation in 2005 and 2011 respectively. According to NOx emissions are strictly regulated management of the vessel through them. In addition, since 2016 the regulation enter into force in the next step ‘Tier III’ was confirmed by MEPC 66th committee. It``s 80% enhanced emissions limits than the ‘Tier I’ Alternatively these emission regulation, research is actively being carried out about exhaust gas after-treatment methods through the vessel application of Selective Catalytic Reduction(SCR). Therefore depending on the basic specification of cell density according to the Area velocity, Space velocity, Linear velocity is studied the effects of NOx removal efficiency