The high energy density fuel is a significant interest for high speed propulsion systems. One possible approach to accomplish this is the addition of highly exothermic and energetic nanoparticles (NPs) to liquid fuels. An experimental study about vaporization and ignition characteristics of liquid fuel droplets containing energetic NPs was carried out at elevated temperatures and pressures under normal gravity. Multicomponent (Kerosene) liquid hydrocarbon fuels were selected as base fluid. Aluminum(Al) NPs were used as energetic additives. The effect of ambient temperature on the evaporation rate constant and on autoignition delay was investigated. The effects of other factors such as concentration of NPs, type and concentration of the surfactants were also investigated. A single Kerosene droplet containing 0.1%, 1% by mass of Al NPs mounted to silicon carbide(SiC) fiber was exposed to high ambient temperature( $400-700^\circ C$ ) at desired ambient pressures(0.1-2.5MPa) under normal gravity. The evaporation histories of nanofluid fuel droplets showed two-staged behavior similar to pure fuel droplets. Similar to pure fuel droplets, the ignition delay time of nanofluid fuel droplets decreased with an increase in ambient temperature. An increase in ambient pressure reduces the ignition location distance from the droplet. The ignition delay time of pure Kerosene droplet was also examined for comparison. The results show that similar to pure Kerosene droplet, the ignition delay time of NPs laden Kerosene droplet was followed the Arrhenius functional form and decreased exponentially with an increase in temperature. The addition of dilute concentrations of Al NPs to Kerosene droplet affected the ignition delay time significantly. The n-Al/Kerosene droplets exhibited disruptive burning behavior, which was characterized by multiple expansions and ruptures and microexplosions. During these microexplosions, the NPs were ejected from the droplets. Thus, the ignition delay time of 1% n-Al/Kerosene droplet was substantially reduced compared to pure Kerosene droplets at all combustion temperatures.
고속 추진 시스템에서 고에너지 밀도의 연료는 중요한 관심사이다. 이러한 연료를 만들기 위한 한 방법으로 높은 발열량과 에너지를 가진 나노입자를 액체 연료에 첨가하는 방식을 들 수 있다. 본 논문에서는 표준중력 하에서 고온 고압에서 높은 에너지를 가진 나노입자를 포함한 액체연료 액적의 증발과 점화에 관한 실험을 수행하였다. 연료로는 다중성분을 지닌 케로신을 사용하였고 고 에너지의 첨가물로는 알루미늄 나노입자를 사용하였다. 온도와 압력이 증발율과 점화지연시간에 미치는 영향을 알아보았고 나노입자의 농도와 계면활성제의 농도가 미치는 영향 또한 살펴보았다. 표준중력 하에서 알루미늄 나노입자를 질량분율 0.1%와 1%를 포함한 케로신 단일 액적을 0.1mm 두께의 실리콘 카바이드에 고정된 상태로 압력조건(0.1-2.5MPa) 와 온도조건( $400-700^\circ C$ )에 노출시킴으로써 실험을 진행하였다. 나노입자가 포함된 연료액적의 증발현상은 순수 연료 액적의 그것과 비슷한 결과를 보여주었다. 점화지연시간 역시 순수 연료액적과 비슷하게 외부 온도의 증가에 따라 감소하는 경향을 보인다. 압력의 증가는 액적으로부터 점화 거리의 감소를 야기하였다. 1%의 알루미늄 나노입자의 첨가는 점화지연시간을 상당히 감소시키는 효과를 보여주었다.
