Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
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Comparison of CNG and LPG Combustion Characteristics in a Large-sized Gas Engine

대형 가스엔진에서 CNG와 LPG 연료의 연소 특성 비교

  • Yongrae Kim (Korea Institute of Machinery and Materials) ;
  • Cheolwoong Park (Korea Institute of Machinery and Materials) ;
  • Hyungjun Jang (Korea Institute of Machinery and Materials) ;
  • Sangho Lee (Korea Institute of Machinery and Materials) ;
  • Young Choi (Korea Institute of Machinery and Materials) ;
  • Sunyoep Lee (Korea Institute of Machinery and Materials)
  • Received : 2024.03.08
  • Accepted : 2024.04.09
  • Published : 2024.06.30
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Abstract

An easy approach to replacing older diesel engines is to replace them with gas engines using fuels such as CNG or LPG. However, fuels such as LPG have not been applied to large gas engines in many cases, so it is not easy to predict the performance of gas engines based on CNG fuel. Accordingly, in this study, we applied LPG fuel to a CNG-based large gas engine and examined the performance and emission characteristics. In particular, the results were confirmed through tests to see how effective EGR, which is widely used for NOx reduction, is applied. As a result, in the case of LPG, even though the operating conditions were secured to a level that excludes serious knocking, mild knocking at high loads was still found to be more frequent than CNG. However, it was possible to secure an output level similar to CNG in the high-speed range. Efficiency was higher due to a faster combustion speed than CNG, and it was confirmed that it was possible to simultaneously reduce NOx and the frequency of mild knocking through the application of EGR.

구형 디젤 엔진들을 대체할 수 있는 손쉬운 접근 방식은 CNG나 LPG와 같은 연료를 활용한 가스 엔진으로 대체하는 것이다. 그러나, LPG와 같은 연료는 대형 가스 엔진에 적용된 사례가 많지 않아서 CNG 연료를 기반으로 하는 가스 엔진에서의 성능을 예측하기가 쉽지 않다. 이에 본 연구에서는 CNG 기반 대형 가스 엔진에 LPG 연료를 적용하여 성능과 배출가스 특성이 어떠한지 살펴보았다. 특히, NOx 저감을 위해 널리 사용되는 EGR 적용 시에 어느 정도의 효과를 보이는지에 대해서도 시험을 통해 결과를 확인하였다. 그결과, LPG의 경우에는 심각한 노킹을 배제할 수준까지 운전 조건을 확보하였음에도 고부하에서 약한 수준의 노킹은 여전히 CNG보다는 빈도수가 높음을 알 수 있었고, 다만 고속 영역에서는 CNG와 유사한 출력 수준을 확보할 수 있었다. CNG보다는 빠른 연소 속도로 인해 LPG의 효율이 높았고, EGR 적용을 통해 NOx는 물론 동시에 약한 노킹의 빈도수를 동시에 저감 가능할 수 있음을 확인하였다.

Keywords

Acknowledgement

본 연구는 환경부의 "Post Stage-V 대응을 위한 중대형 건설기계 LPG 엔진 개조 및 차량 적용 기술개발(No. 202100339001)" 과제의 지원을 통해 작성되었기에 이에 감사를 표합니다.

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