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LIEF법을 이용한 고온 고압 조건에서 충돌 디젤 분무의 특성에 관한 연구
김용래(Yongrae Kim),김만식(Manshik Kim),민경덕(Kyoungdoug Min) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Diesel sprays injected into a combustion chamber of a small sized HSDI engine impinge 0 a piston surface. As a consequence, their vaporization, mixture formation and combustion process are affected by impingement phenomena. The liquid and vapor phase of diesel sprays impinging on a flat and hot wall were visualized under high temperature and pressure conditio by LIEF technique. The experiments were carried in a constant volume chamber and the injection pressure and impinging distance were varied to analyze the effect on impinging sprays.<br/> It was found that the radius and height of a impinging spray were almost constant regardless of the injection pressure. And the vapor distribution of a impinging spray injected at hig pressure was more uniform than low injection pressure.<br/>
김용래(Yongrae Kim),임재만(Jaeman Lim),민경덕(Kyoungdoun Min) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Characteristics of auto-ignition of dimethyl ether (DME) and diesel sprays were investigated by experiment and chemical kinetics. Ignition delay of DME and diesel sprays was measured in a combustion-type constant volume vessel under various conditions. Oxygen concentration was varied to investigate the effect of EGR. The oxygen concentration affected more in ignition delays of diesel fuel more than that of DME. There exists little difference in ignition delays at the high ambient pressure condition. A reduced chemical mechanism was tuned to fit the ignition delay of diesel fuel by comparing the experimental results. <br/> The calculated results were compared with the experimental results to investigate the ignition characteristics of two fuels.
급속압축기를 이용한 연료의 점화지연 측정과 축소화학반응식의 수립
김용래(Yongrae Kim),성현택(Hyeontaek Seong),민경덕(Kyoungdoug Min) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
The auto-ignition characteristics of fuel is crucial in CAI engine development. Ignition characteristics of primary reference fuel were investigated using both of experiment and calculation. As an experimental research, a RCM (rapid compression machine) was used to measure the ignition delay time of primary reference fuel in a high temperature and pressure condition like a engine condition. The experiment was conducted in various conditions. Since internal EGR is used using variable valve timing system in CAI engine, the effect of CO₂ percentage in fuel-air mixture was also investigated. A reduced chemical kinetic mechanism of n-heptane and iso-octane was developed to estimate ignition delay and a temperature rise in an RCM experiment conditions. The calculated results in constant volume condition showed a good agreement with shock-tube experimental data. The developed mechanism was applied in calculation to simulate the RCM experiment and these results were compared with the experimental results. There was a modest difference between two results, but they showed a similar tendency and the calculation time was very fast compared with the calculation time from a detailed mechanism.
수소 내연기관의 흡기 냉각 방법에 따른 최고 출력 향상에 관한 연구
김용래(Yongrae Kim),박철웅(Cheolwoong Park),오세철(Sechul Oh),최영(Young Choi),이정우(Jeongwoo Lee) 한국가스학회 2021 한국가스학회지 Vol.25 No.5
수소는 동일한 공연비(AF ratio, Air-to-fuel ratio)에서 가솔린에 비해 점화에너지가 현격히 낮기 때문에, 희박한 혼합기 조건에서도 안정적으로 연소할 수 있는 장점을 가지고 있어 연소를 기반으로하는 내연기관에도 적용이 가능하다. 그러나 일부 연소조건에서 역화(Back-fire) 혹은 조기 점화(Pre-ignition)와 같은 이상 연소가 발생하기 쉬운 문제를 가지고 있다. 따라서 본 연구에서는 엔진의 흡기(Intake gas mixture)를 구성하는 신기(Fresh air)와 수소 연료를 각각 냉각하여 공급함으로써, 역화를 최소화하여 최고 출력을 향상하는 연구를 진행하였다. 2.4 L급 전기점화(SI, Spark-ignition)엔진이 사용되었으며 수소는 포트분사 방식(PFI, Port Fuel Injection)으로 공급하였다. 신기의 온도는 터보차저가 장착된 상황에서 인터쿨러(Intercooler)를 이용하여 제어하였으며, 수소의 냉각은 칠러의 냉매와 열교환기를 통하여 직접 냉각 후 공급하였다. 그 결과 신기의 온도를 10~20 ℃가량 냉각시킬 경우 최고출력이 약 6.5~8.6 % 가량 향상되는 것을 확인할 수 있었으며, 수소를 –6 ℃까지 냉각하여 공급할 경우 마찬가지로 약 7.7 % 가량의 최고 출력을 향상할 수 있었다. Since hydrogen has the lower minimum ignition energy than that of gasoline, hydrogen could be also appropriate for the IC engine systems. However, due to the low ignition energy, there might be a ‘back-fire’ and ‘pre-ignition’ problems with hydrogen SI(Spark-ignition) combustion. In this research, cooling effects of intake gas mixture on the improvement of the maximum power output were evaluated in a 2.4 L SI engine. There were two ways to cool intake gas mixtures. The first one was cooling intake fresh air by adjusting inter-cooler system after turbocharger. The other one was cooling hydrogen fuel before supplying by using heat ex-changer. Cooling hydrogen was performed under natural aspired condition. The result showed that cooling fresh air from 40 ℃ to 20~30 ℃ improved the maximum brake power up to 6.5~8.6 % and cooling hydrogen fuel as –6 ℃ enhanced the maximum brake power likewise.
김용래(Yongrae Kim),이경현(Kyeonghyeon Lee),민경덕(Kyoungdoug Min),이원근(Wongeun Lee),김홍집(Hongjip Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Simulation of CAI engine was conducted in an single cylinder engine which was modified for CAI combustion. Result of CFD calculation including a direct injection during underlap provided that the mixture concentration around intake valve close had a uniform distribution. A reduced chemical kinetic mechanism was used for gasoline fuel and initial conditions (EGR and temperature) were acquired from 1-D cycle simulation. The simulation results showed that CAI combustion was occurred at the temperature of 970 K ~ 1000 K and the pressure of around 15 bar. The EGR rate had an important role for high temperature mixture but the temperature in itself was more critical for the induction of CAI combustion. EGR and mixture temperature could be adjusted by an variation of valve lift and timing.