• 대한기계학회논문집
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• 제14권5호
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• pp.1330-1336
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• 1990

The factors to act on atomization of liquid fuel are viscosity, geometric shape of nozzle, atomizing pressure, etc. Most of high viscous liquid fuels show decrease in viscosity by raising the preheat temperature, but the viscosity of liquid fuel like CWM does not readily change with fuel temperature. As an experimental study to investigate the atomizing characteristics of CWM, CWM fuel is atomizing with a twin-fluid atomizer, and the effects of the geometric shape of spray nozzle on atomization are investigated by measuring the Sauter`s Mean Diameter (SMD) of CWM. The summarized results obtained in this study are as follows ; (1) As the ratio of the mass flows of atomizing air to that of fuel (W$_{a}$ /W$_{1}$) increases, 능 decreases when fuel temperature is constant. (2) At the ratio (t/d) 4 of thickness (t) of spray nozzle hole to the diameter (d) of the hole, there is the best atomization. And SMD decreases when t/d is between 1 to 4 and increases when t/d > 4.

• 한국초전도ㆍ저온공학회논문지
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• 제24권2호
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• pp.27-38
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• 2022

Urban air mobility (UAM) has recently attracted lots of attention as a solution to urban centralization and global warming. Electric vertical take-off and landing (eVTOL) is a concept that emerges as one of the promising and clean technologies for UAM. There are two difficult challenges for eVTOL aircraft to solve. One is how to improve the weight efficiency of aircraft, and the other is how to complete long-range missions for UAM's flight scenarios. To approach these challenges, we propose a consolidated concept design of battery-fuel cell hybrid tiltrotor aircraft with a liquid hydrogen (LH₂) fuel tank. The efficiency of a battery-fuel cell hybrid powertrain system on the designed eVTOL aircraft is compared to that of a battery-only powertrain system. This paper shows how much payload can increase and the flight scenario can be improved by hybridizing the battery and fuel cell and presenting a detailed concept of a cryogenic storage tank for LH₂.

• 한국분무공학회지
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• 제13권3호
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• pp.117-125
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• 2008

The correlations for the prediction of maximum liquid-phase penetration in diesel spray are reviewed in this study. The existing models developed for the prediction of maximum liquid-phase penetration can be categorized as the zero-dimensional (empirical) model, the multi-dimensional model and the other model. The existing zero-dimensional model can be classified into four groups and the existing multidimensional models can be classified into three groups. The other model includes holistic hydraulic and spray model. The maximum liquid-phase penetration is mainly affected by nozzle diameter, fuel volatility, injection pressure, ambient gas pressure, ambient gas density and fuel temperature. In the case of empirical correlations incorporated with spray angle, the predicted results will be different according to the selection of correlation for spray angle. The research for the effect of boiling point temperatures on maximum liquid-phase penetration is required. In the case of multidimensional model, there exist problems of the grid and spray sub-models dependency effects.

• 한국분무공학회지
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• 제9권2호
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• pp.34-40
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• 2004

In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its characteristics and devising a means of fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and the jet penetrations in the high pressure conditions have a similar tendency. In the dual orifice injectors, the jet penetrations of rare orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rare orifice is increased because of the drag reduction created by the jet column of the front orifice. Because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual orifice injector is much larger than the jet penetrations of single orifice injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

• 대한기계학회논문집B
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• 제30권7호
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• pp.682-691
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• 2006

This study was conducted to assess the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the various ambient conditions. Spray structure and spatial distribution of liquid phase concentration are investigated using a thin laser sheet illumination technique on the multi-component mixed fuels. A pulsed Ar+ laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contain $i-octane(C_8H_{18}),\;n-dodecane(C_{12}H_{26})$ and $n-hexadecane(C_{16}H_{34})$ that are selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 25Mpa, 42MPa, 72MPa and 112MPa in injection pressure, $5kg/m^3,\;15kg/m^3\;and\;20kg/m^3$ in ambient gas density, 400K, 500K, 600K and 700K in ambient gas temperature, 300K and 368K in fuel temperature, and different fuel mass fraction. Experimental results indicate that the more high-boiling point component, the longer the liquid phase it were closely related to fuel physical properties, but injection pressure had no effect on. And there was a high correlation between the liquid phase length and boiling temperature at 75% distillation point.

• 대한기계학회논문집B
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• 제38권2호
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• pp.155-163
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• 2014

주유소에서 거래되는 액체 연료인 석유류는 온도 변화에 따라 팽창과 수축하게 된다. 석유류의 체적팽창계수는 약 $0.1%/^{\circ}C$이고, 우리나라의 기온은 겨울철에는 $-15^{\circ}C$, 여름철에는 $35^{\circ}C$까지 변한다. 온도 변화에 따른 체적의 변화가 석유류 거래에 미치는 영향을 조사하기 위해 주유소에 저장된 연료와 주유되는 연료의 온도 변화를 측정하였다. 또 우리나라의 지난 50 년간의 일간, 월간, 년간 온도 변화를 고찰하였다. 지하 저장탱크의 유류 온도는 계절에 관계없이 하루 중 안정되게 유지되었다. 주유소 주위의 환경 조건과 위치, 주유 빈도등이 주유되는 유류의 온도에 영향을 미치는 것을 알 수 있었다. 이러한 연구 결과는 건전한 석유류의 거래와 관련 법령의 제정에 활용될 것이다.

• 한국항공우주학회지
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• 제45권12호
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• pp.1059-1068
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• 2017

우주 탐사선은 다량의 액체 연료를 탑재하는데, 절반 이상을 넘는 경우가 많다. 이러한 경우, 액체 연료의 슬라슁 현상이 탐사선의 자세 안정성에 영향을 주기 때문에 탐사선 설계에 슬라슁 현상을 고려해야 한다. 본 논문에서는, 액체 연료의 슬라슁 현상과 이와 상호작용하는 탐사선의 동적 거동을 분석한 결과를 제시한다. 이를 위하여 탐사선의 기동이 액체 연료의 슬라슁 현상을 일으키는 모델과 슬라슁에 의한 반력 힘과 모멘트가 탐사선에게 전달되는 모델을 개발하였다. 모델리카 언어로 작성한 시뮬레이션 프로그램을 이용하여 탐사선의 거동을 분석하였다.

• 한국기계가공학회지
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• 제16권3호
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• pp.88-93
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• 2017

In the present study, the ignition characteristics of liquid fuel were experimentally investigated. To quantify its ignitability as ignition characteristics, the minimum ignition energy (MIE) of liquid fuel was defined and measured under at the elevated oxygen concentrations and reduced atmospheric pressures which that are the most probable conditions likely to be encountered during operation of the space launch vehicle's operating process. The experimental results demonstrate that the measured MIE decreased with the increasing the oxygen concentration at given atmospheric pressures. When the atmospheric pressure was reduced from 1 atm to 0.2 atm at a fixed oxygen concentration, the measured MIE was found to vary with $P^{-2}$ but the lowest MIE was observed at 0.8 atm.

• 한국분무공학회지
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• 제10권4호
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• pp.8-15
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• 2005

The use of clean gaseous fuels for the purpose of high efficiency and low emission in automotive engines has tendency to increase in order to meet the reinforcing emission regulations and to efficiently utilize limited natural resources. Automotive companies developed and commercialized a LPG liquid injection system, which is mounted on LPLi(Liquid Phase LPG Injection) engines and vehicles based on this research trend. This research examines the biggest problem in LPLi engine, that is, the leakage characteristics of low viscosity LPG fuel according to the injector design variables. This study is also aimed to improve the performance of fuel-leakage in LPLi engine through the addition of a lubrication improver in HFRR(High Frequency Reciprocating Rig) facility. The needle displacement and the spring displacement of an LPLi injector are found to be already optimized. The possibility of a maximum of 70% leakage reduction compared to a conventional case, is verified when 1000ppm of a lubrication improvement material is added and 40% increase of a injector spring constant (K) is applied.

• International Journal of Aerospace System Engineering
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• 제5권2호
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• pp.16-22
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• 2018

An analysis has been made on the performance variation due to pressure drop change at propellant supply pipes of liquid rocket engine. The objective is to compare the effectiveness of control variables to tune the liquid rocket engine performance. The mode analysis program has been used to estimate the engine performance for different modes which is realized by controlling the flow rate of propellant. The oxidizer of combustion chamber, the fuel of combustion chamber, the oxidizer of gas generator and the fuel of gas generator are the independent variables to control engine thrust, engine mixture ratio and temperature of gas generator product gas. The analysis program is validated by comparing with the powerpack test results. The error range of compared variables is order of 4%. After comparison of tuning effectiveness it is turned out that the pressure drop at oxidizer pipe of gas generator and pressure drop at combustion chamber fuel pipe and the pressure drop at the fuel pipe of gas generator can effectively tune the thrust of engine, mixture ratio of engine and temperature of product gas from gas generator respectively.