Experimental Study on Natural Gas Conversion Vehicle(2) - Evaluation of Injection System

천연가스 개조 승용차에 대한 실험적 연구(2) - 분사 시스템 평가

  • Kim, Hyung-Gu (Graduate School of NID Fusion Technology, Seoul National University of Science and Technology) ;
  • Kwon, Suntae (Engine Development Team, Institute of Technology, Daerim Motors) ;
  • Ohm, Inyong (Department of Mechanical & Automotive Engineering, Seoul National University of Science & Technology)
  • 김형구 (서울과학기술대학교 NID융합기술대학원) ;
  • 권순태 (대림자동차공업 기술연구소 엔진개발팀) ;
  • 엄인용 (서울과학기술대학교 기계.자동차공학과)
  • Received : 2015.05.08
  • Accepted : 2015.06.08
  • Published : 2015.07.01


In the previous study, several problems were observed in a NG conversion vehicle, which were fail of air-fuel ratio closed loop control, aggravated fuel economy, increased harmful emission and declined roadability. It was provisionally supposed that the mismatch of injection system with the engine caused these performance deterioration. In this context, the characteristics of fuel injection system of commercial conversion kit for NG were investigated experimentally varying the engine speed, fuel rail pressure and volume. The results are as follows; The injection quantity decreases as the engine speed increases due to the extremely small rail volume of the presenting system and flow rate of No. 2 injector are always lower than that of the other ones regardless of the speed under the dynamic operation condition. Furthermore the existing system does not meet the required fuel quantity for the normal engine operation over 3000 RPM. On the other hands, the large rail volume systems ease and/or eliminate the difference of injection quantity between the injectors according to the speed variation, however, these systems decrease injection flow rate and still cannot supply sufficient fuel. Finally, suitable combination of the higher rail pressure and the larger rail volume might be a solution about these problems.


Supported by : 서울과학기술대학교


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