Journal of the Korean Institute of Gas (한국가스학회지)

The Korean Institute of GAS (한국가스학회)
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Experimental Research on the Power Improvement by Increasing Intake pressure in a 1.4 L Turbocharged CNG Port Injection Spark Ignition Engine

1.4L 급 터보 CNG 엔진에서 흡기압력 상승에 따른 출력 증대 효과에 관한 연구

  • Lee, Jeong-Woo (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Park, Cheol-Woong (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Bae, Jong-Won (Dept. of Mechanical Engineering, Soongsil University) ;
  • Kim, Chang-Gi (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Lee, Sun-Youp (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Kim, Yong-Rae (Dept. of Engine Research, Korea Institute of Machinery and Materials)
  • 이정우 (한국기계연구원 그린동력연구실) ;
  • 박철웅 (한국기계연구원 그린동력연구실) ;
  • 배종원 (숭실대학교 기계공학과) ;
  • 김창기 (한국기계연구원 그린동력연구실) ;
  • 이선엽 (한국기계연구원 그린동력연구실) ;
  • 김용래 (한국기계연구원 그린동력연구실)
  • Received : 2019.09.30
  • Accepted : 2019.12.19
  • Published : 2019.12.31
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Abstract

Natural gas has been regarded as one of major alternative fuels, because of the increment of mining shale gas and supplying PNG(Pipeline Natural Gas) from Russia. Thus, it needs to broaden the usage of natural gas as the increasing its supplement. In this situation, application of natural gas on the transport area is a good suggestion to reduce exhaust emissions such as CO2(carbon dioxides) and soot from vehicles. For this reason, natural gas can be applied to SI(spark ignition) engines due to its anti-knocking and low auto-ignitibility characteristics. Recently, since turbocharged SI engine has been widely used, it needs to apply natural gas on the turbocharged SI engine. However, there is a major challenge for using natural gas on turbocharged SI engine, because it is hard to make natural gas direct injection in the cylinder, while gasoline is possible. As a result, there is a loss of fresh air when natural gas is injected by MPI (multi-point injection) method under the same intake pressure with gasoline-fueled condition. It brings the power reduction. Therefore, in this research, intake pressure was increased by controling the turbocharger system under natural gas-fueled condition to improve power output. The goal of improved power is the same level with that of gasoline-fueled condition under the maximum torque condition of each engine speed. As a result, the maximum power levels, which are the same with those of gasoline-fueled conditions, with improved brake thermal efficiency could be achieved for each engine speed (from 2,000 to 6,000 rpm) by increasing intake pressure 5-27 % compared to those of gasoline-fueled conditions.

셰일가스의 채굴량 확장과 러시아를 통한 PNG (Pipeline Natural Gas)의 도입은 천연가스가 유력한 대체 연료임을 시사해주고 있다. 따라서 향후 증대될 천연가스의 공급에 맞추어 해당 연료의 수요처 증대가 필수적인 상황이다. 이와 같은 상황에서 수송분야는 저탄소 기체 연료인 천연가스를 적용하기 적합한 분야이며, 이를 통해 이산화탄소와 입자상 물질 등의 유해 배기물질을 저감하는 데 큰 역할을 할 것으로 기대된다. 천연가스는 자발화 특성이 낮고, 내노킹(Anti-knocking)성이 우수하기 때문에 전기점화 방식에 적합하다. 최근 가솔린 엔진은 연비 개선을 위해 연소실에 직접 분사하는 방식을 주로 채택하고 있으나,연소실 내로 액상 직분사를 하는 반면 천연가스의 경우 액상분사 혹은 고압 분사가 어렵다. 따라서 포트에 분사하는 방식을 사용하므로 동등 흡기압력에서 연료의 분율이 흡입공기의 체적을 대체하여 가솔린 직분 방식에 비해 출력이 저하되는 현상을 피할 수 없게 된다. 이에 본 연구에서는 터보차저를 천연가스 포트 분사 엔진에 적용하여 흡기 압력 상향을 통한 출력 보상을 도모하고자 하였다.그 결과 천연가스 적용 시 흡기압력을 기존 가솔린 대비 5-27 % 상향 시 가솔린 직분사 엔진과 동등 출력을 확보함과 동시에 향상된 제동 열효율을 확인 할 수 있었다.

Keywords

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