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Effect of EGR on power and exhaust emissions in diesel engine

디젤엔진의 출력 및 배기가스에 미치는 EGR의 영향

  • Song, Kyu-keun (Department of Mechanical System Engineering, Chonbuk National University)
  • Received : 2015.08.06
  • Accepted : 2015.11.18
  • Published : 2015.11.30

Abstract

Diesel engines are widely used due to superior power and fuel consumption, however there are many challenges in exhaust gas management. Exhaust gas recirculation (EGR) is the most effective technique for reducing mono-nitrogen oxide (NOx) emissions in a diesel engine, in comparison with other catalytic technologies. In addition, the technology has a number of advantages in terms of economic efficiency and implementation. In this study, the effects on the power and exhaust characteristics of diesel engines equipped with EGR systems were investigated. It was found that as the EGR rate increased, horsepower expressed as IHP and BHP decreased. The net effect of the application of EGR was measured at various engine speeds. EGR technology caused decreases in BHP of around 9% during low engine speed and 3.5% during high engine speed. Additionally, NOx emissions reduced as the EGR rate increased, and increased as engine speed increased. However, smoke emissions increased as the EGR rate increased, and decreased as engine speed increased. The optimum operating conditions and ERG rate to simultaneously achieve minimum NOx and smoke emissions were investigate. It was found that as the EGR rate increased, optimal operating speed for minimal NOx and smoke also increased. Keywords: Diesel engine, Exhaust gas recirculation, Power perfomance, Emission characteristics, NOx, Smoke

디젤 엔진은 출력 및 연료소비율이 우수하여 많이 사용되고 있다. 그러나 디젤엔진은 가솔린엔진에 비하여 배출가스 저감 기술 등에서 아직 해결해야할 문제점들이 많고, 대기오염의 주범이다. 디젤엔진에 있어 배기가스 재순환(EGR; Exhaust Gas Recirculation) 기술은 여러 촉매 기술에 비해 질소산화물(NOx) 배출 저감을 위한 가장 효과적인 기술이며 또한 경제성, 적용 가능성 측면에서도 많은 장점을 갖고 있다. 본 연구에서는 EGR 시스템을 장착한 디젤 엔진을 대상으로 EGR이 디젤기관의 출력 성능 및 배기특성에 미치는 영향을 고찰하였고, 다음과 같은 결론을 얻었다. EGR율이 증가함에 따라 IHP 및 BHP는 감소하며, 순수EGR에 의한 영향은 엔진회전수에 따라 차이는 있지만, 순수 EGR에 의한 BHP는 저속 운전에서는 약 9%, 고속운전에서는 3.5% 정도 감소하였다. 그리고 NOx는 EGR율이 증가함에 따라 감소하고, 엔진회전수 증가할수록 증가한다. 또한 매연(smoke)은 EGR율이 증가함에 따라서 증가하고, 엔진회전수가 증가할수록 감소한다. EGR율에 따라 NOx와 매연 배출을 동시에 최소로 할 수 있는 최적의 운전 상태가 존재하며, EGR율이 증가할 수록 NOx 및 매연을 위한 최적운전 속도는 증가한다.

Keywords

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