• Journal of Hydrogen and New Energy
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• v.13 no.3
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• pp.233-241
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• 2002

To achieve hydrogen power system with high performance and stable operation, the COVimep of hydrogen fueled engine with direct injection was evaluated with the change of engine speed, injection timing, air-fuel equivalence ratio and spark timing. And the cause of cycle variation was analyzed by using coefficient of variation in combustion period defined in this study. the results showed that the cycle variation of hydrogen fueled engine is mainly dependent on the early combustion period.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.11-17
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• 2011

본 연구는 라디칼 착화(Radical Ignition이하 RI) 기술을 적용한 부실직분식 CNG(Compressed Natural Gas) 엔진의 구동특성에 관한 것이다. 실험엔진은 단기통 디젤엔진을 개조하여 사용하였으며, 이는 부실식 디젤엔진처럼 연소실이 주실과 부실로 나누어져 있다. 부실에 분사된 CNG는 스파크플러그로 점화하며, 부실로 부터의 연소가스가 주실 희박 혼합기를 시켜 구동하는 엔진이다. RI 기술은 연소속도를 향상시킬 수 있다. 본 연구는 주로 저부하 RI-CNG 엔진의 성능을 연구하였다. 연료분사기간은 9 ms, 공기과잉률은 1.0, 1.2, 1.4로 하였다. 연료분사시기는 엔진의 배가밸브가 닫히는 ATDC $20^{\circ}CA$ 부터 $120^{\circ}CA$ 사이로, $20^{\circ}CA$ 간격으로 지각시켜 가며 실험하였다. 본 연구는 연료분사시기 및 공기과잉률이 연소최고압력 ($P_{max}$), 연소최고압력시기(${\Theta}_{pmax}$), 도시평균유효압력(IMEP), 사이클 변동계수($COV_{imep}$), 연소속도에 미치는 양향 등을 구하고 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.700-707
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• 2017

In the international natural gas market, natural gas has markedly low calories. The domestic calories standard of natural gas was changed and the performance and efficiency of many industrial machines using natural gas were affected because of low caloric natural gas. Therefore, in this study, a dual fuel engine fueled with natural gas and diesel was tested to examine the effects of the CNG substitution rate on the combustion characteristics, such as thermal efficiency, COVimep and heat release rate. The CNG substitution rate was defined as the ratio of CNG instead of diesel, which was calculated as the total energy. The conditions of the tested engine were fixed $1800rpm/500N{\cdot}m$. In addition, diesel fuel was injected at $16^{\circ}CA$ BTDC and the fuel pressure was fixed at 85 MPa; the lower heating value of CNG was $10,400kcal/Nm^3$. The results of the engine test showed that the amount of diesel fuel was changed according to the CNG substitution rate. Therefore, when the substitution rate was increased, the amount of diesel fuel was decreased, which affected the energy for ignition. In addition, the ignition delay duration was increased, which affected the thermal efficiency and torque. On the other hand, the COVimep was less than 5% and a stable combustion state of the engine was shown.