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고고도 무인기용 수소연료엔진의 냉각수 온도변화에 따른 연소 특성

Characteristics of Combustion by Varying Different Coolant-temperature in a Hydrogen Engine for HALE UAV

  • 이의형 (한국기계연구원 그린동력연구실) ;
  • 장형준 (한국기계연구원 그린동력연구실) ;
  • 박철웅 (한국기계연구원 그린동력연구실) ;
  • 김용래 (한국기계연구원 그린동력연구실) ;
  • 최영 (한국기계연구원 그린동력연구실)
  • Yi, Ui-Hyung (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Jang, Hyeong-Jun (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Park, Cheol-Woong (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Kim, Yong-Rae (Dept. of Engine Research, Korea Institute of Machinery and Materials) ;
  • Choi, Young (Dept. of Engine Research, Korea Institute of Machinery and Materials)
  • 투고 : 2017.10.25
  • 심사 : 2018.04.12
  • 발행 : 2018.04.30

초록

최근 무인기에 대한 관심과 수요가 높아지고 있는 가운데, 가동범위가 넓고 전략적으로 활용이 많은 고고도장기체공 무인기의 동력원개발이 연구 목표로 검토되었다. 기존 왕복동 엔진에 수소 연료를 적용하는 기술은 현행으로써 적용성이 용이하고 경제적이다. 수소는 중량당 에너지 밀도가 높아서 한 번 충전으로 장시간 운항을 지속할 수 있고 환경적인 측면에서도 무공해 연료라는 긍정적인 부분이 존재하기 때문에 적합하다고 평가된다. 하지만 현재 수소연료를 왕복동 엔진에 적용한 개발사례가 적은 편이라 향후 기술적으로 많은 연구가 필요한 것으로 판단된다. 항공기는 운항고도에 따라 공기밀도 저감으로 인한 냉각성능 저하 또는 복사열 감소에 의한 주변온도 강하로 과냉각이 될 수 있는 요인들이 존재한다. 따라서 본 실험은 냉각수온을 변화시켜서 이러한 주변온도 변화가 수소연료 엔진에 미치는 연소특성에 대해 살펴보았다. 역화에 의한 안정적인 운전 영역의 제한은 냉각수 온도변화에 의한 영향보다 공기과잉률에 의한 영향이 지배적으로 나타났으며, 냉각수 온도가 증가할 경우 충진효율이 감소하여 토크가 감소하고 냉각수 온도가 감소할 경우 열손실이 증가하여 열효율이 감소하였다.

Using hydrogen fuel is expected to be suitable as a reciprocating internal combustion engine with heightened interest in HALE(High Altitude Long Endurance) UAV(Unmanned Aerial Vehicle). Hydrogen is hightest energy density per mass so it can continue to charge for long periods of time and have positive part of the environmental effects. However, it is estimated that there is less research on hydrogen fuel engine currently applied, and many studies need to be done. Depending on the operation, there are factors that result in supercooling due to reduced radiation or reduce cooling performance due to low air density. Therefore, the experiment was to change the temperature of the cooling water and investigate the effect on engine combustions. The limitation of the stable operation range due to backfire is dominated by the excess air ratio rather than the effect of the cooling water temperature change. When the cooling water temperature increases, the volumetric efficiency decreases and the torque decreases. As the cooling water temperature decreases, the heat loss was increased and consequently the thermal efficiency was decreased.

키워드

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