Journal of the Korea Convergence Society (한국융합학회논문지)

Korea Convergence Society (한국융합학회)
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A Convergence Study on the Effects of NH3/NOx Ratio and Catalyst Type on the NOx Reduction by Urea-SCR System of Diesel Engine

디젤엔진의 Urea-SCR 시스템에 의한 NH3/NOx 비율 및 촉매 방식이 NOx 저감에 미치는 영향에 관한 융합연구

  • Yoon, Heung-Soo (Dept. of Security and Management Engineering, Graduate School, Myongji University) ;
  • Ryu, Yeon-Seung (Dept. of Security and Management Engineering, Graduate School, Myongji University)
  • 윤흥수 (명지대학교 대학원 보안경영공학과) ;
  • 류연승 (명지대학교 대학원 보안경영공학과)
  • Received : 2019.01.09
  • Accepted : 2019.04.20
  • Published : 2019.04.28
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Abstract

Diesel engines have important advantages over its gasoline counterpart including high thermal efficiency, high fuel economy and low emissions of CO, HC and $CO_2$. However, NOx reducing is more difficult on diesel engines because of the high $O_2$ concentration in the exhaust, marking general three way catalytic converter ineffective. Two method available technologies for continuous NOx reduction onboard diesel engines are Urea-SCR and LNT. The implementation of the Urea-SCR systems in design engines have made it possible for 2.5l and over engines to meet the tightened NOx emission standard of Euro-6. In this study, we investigate the characteristics of NOx reduction with respect to engine speed, load, types of catalyst and the $NH_3$/NOx ratio and present the conditions which maximize NOx reduction. Also we provide detailed experimental data on Urea-SCR which can be used for the preparation for standards beyond Euro-6.

디젤엔진은 열효율이 높고 연비가 좋으며 CO, HC 및 $CO_2$의 배출량이 낮은 등 가솔린 엔진보다 상당한 장점이 있다. 그러나 디젤엔진은 배기가스 중에 $O_2$ 농도가 높기 때문에 NOx 저감이 어렵고, 삼원촉매를 적용하기 어렵다. Urea-SCR과 LNT는 디젤엔진에서 NOx를 연속적으로 저감하는데 활용 가능한 두 기술이다. 디자인 엔진에 Urea-SCR 시스템을 구현함으로써 2.5l 이상 엔진에서 Euro-6의 강화된 NOx 기준을 충족시킬 수 있게 되었다. 본 연구에서는 엔진 회전속도, 부하, 촉매 방식 및 $NH_3$/NOx 비율에 따른 NOx 저감 특성을 연구하여 NOx 저감을 극대화하는 조건을 제시하고자 한다. 또한 Euro-6 이상의 규제에 대응할 수 있도록 Urea-SCR에 대한 정밀한 실험 데이터를 제공하고자 한다.

Keywords

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Fig. 1. The photograph of the exhaust layout installation in engine test bench

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Fig. 2. Schematic diagram of Urea-SCR system in engine bench test

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Fig. 3. The photograph of the canning zeolite based Cu-ZSM-5 catalysts and Cu-CHA catalysts

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Fig. 4. The schematic diagram showing how the NH3/NOx ratio is controlled by modulating the urea injection duration

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Fig. 5. The sample experiment and curve fit used to determine the NH3/NOx ratio with respect to injection duration which is used to predetermine the injection quantity

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Fig. 6. Variation of (a) NOx concentration and (b) NOx reduction rate for LT-catalyst and HTcatalyst for the Urea-SCR system in Dual-Loop EGR CRDI engine. The operating conditions were as follows: engine speed was 1,500rpm, bmep was 4bars, and the coolant temperature was 85±2°C

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Fig. 7. Variation of (a) NOx concentration and (b) NOx reduction rate for LT-catalyst and HTcatalyst for the Urea-SCR system in Dual-Loop EGR CRDI engine. The operating conditions were as follows: engine speed was 1,500rpm, bmep was 8bars, and the coolant temperature was 85±2°C

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Fig. 8. Variation of (a) NOx concentration and (b) NOx reduction rate for LT-catalyst and HTcatalyst for the Urea-SCR system in Dual-Loop EGR CRDI engine. The operating conditions were as follows: engine speed was 2,000rpm, bmep was 4 bars, and the coolant temperature was 85±2°C

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Fig. 9. Variation of (a) NOx concentration and (b) NOx reduction rate for LT-catalyst and HTcatalyst for the Urea-SCR system in Dual-Loop EGR CRDI engine. The operating conditions were as follows: engine speed was 2,000rpm, bmep was 8bars, and the coolant temperature was 85±2°C

Table 1. Specification of the 2.2l Common Rail Direct Injection(CRDI) engine

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Table 2. Specification of catalysts

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Table 3. Specifications of the eddy current dynamometer

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Table 4. The experimental condition

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Table 5. Specifications of the urea aqueous solution

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