• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.73-80
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• 2013

Endothermic fuel utilizing technology is considered as a unique practical method of hypersonic vehicle for long distance flight. Research activities about characteristics of fuel injection and combustion using cracked by endothermic reaction are reviewed. Studies on characterization of supercritical fuel injection and mixing within supersonic flow field are surveyed. Researches on combustion characteristics such as ignition delay time, laminar burning velocity and combustion efficiency at supersonic model combustor are reviewed. In addition, domestic research activities on endothermic fuel are surveyed.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.4
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• pp.400-412
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• 2022

Hydrogen with high chemical reactivity and combustion efficiency, is expected to reduce greenhouse gas and CO emission. However, there is a problem of increase in NOx emission due to hydrogen combustion. MILD combustion technology has been proposed to resolve NOx emission. In this study, the characteristics of MILD combustion and NOx formation by flue gas recirculation (KV) in CH₄-H₂ mixture were analyzed and predicted using 0D premixed combustion model. The ignition delay time became shorter as the hydrogen co-firing rate increased, and longer as the recirculation rate increased. For NOx emission, EINO decreased as the KV increased, but EINO increased as the hydrogen co- firing rate increased. In particular, EINO was predicted to increase significiently above 80% hydrogen. Through the pathway analysis of NO formation, it was found that the influence of N₂O intermediate route and NNH route was enhanced for hydrogen co-firing.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.68-74
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• 2014

During the life firing test of 1 N-class thruster development model, pulse mode performance and performance changes were examined. The deviation of pulse mode response time according to thruster feed pressure was relatively small and the resultant ignition delay, response time, tail-off time were 32-35 ms, 86-91 ms, 89-98 ms, respectively. For the stabilized pulse region the impulse bit revealed the outstanding reproducibility of 1.41, 1.32, 2.10% at $3{\sigma}$. During the life firing test, the impulse bit was decreased with limited amounts, therefore the pulse mode performance could be considered to be maintained. The thrust centroid was also maintained during the life firing test.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.1
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• pp.30-38
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• 1993

In this study, the combustion characteristics in a pre-combustion chamber diesel engine was investigated with experimental conditions of marine engine load. The heat release analysis used was a single-zone single-chamber thermodynamic analysis based on pre-combustion chamber pressure-time data. Based on the results of this investigation, the following conclusions were reached: 1) Increasing the load, peak pressure was increased and position of P sub(max) was retarded in crank angle degrees. 2) Ignition delay time was almost constant without relating to the load and the heat values to form a combusitible mixture were decreased apparently with increasing the load. 3) In premixed-combustion mode, the pattern of heat release rate was resembled without relating to the load and premixed-combustion time was shortened with increasing the load. 4) Increasing the load, mass of premixed-burned fuel was increased slightly, but was invariable beyond a certain fuel-air ratio. 5) Increasing the load, premixed-burned fraction was decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.140-148
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• 1999

Experiments on flame spread in an one-dimensional droplet array up to supercritical pressures of fuel droplet have been conducted In normal gravity and microgravity. Evaporating process around unburnt droplet is observed through high-speed Schlieren and direct visualizations in detail, and flame spread rate is measured using high speed chemiluminescence images of OH radical. Flame spread behaviors are categorized into three: flame spread is continuous at low pressures and is regularly intermittent up to the critical pressure of fuel. flame spread is irregularly intermittent and zig-zag at supercritical pressures of fuel. At atmospheric pressure, the limit droplet spacing and the droplet spacing of maximum flame spread rate in microgravity are larger than those in normal gravity. In microgravity, the flame spread rate with the increase of ambient pressure decreases initially, takes a minimum, and then decreases after taking maximum. This is so because the flame spread time is determined by competing effects between the increased transfer time of thermal boundary layer due to reduced flame diameter and the reduced ignition delay time in terms of the increase of ambient pressure. Consequently, it is found that flame spread behaviors in microgravity are considerably different from those in normal gravity due to the absence of natural convection.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.7
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• pp.685-693
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• 2013

The biodiesel used as an alternative fuel for diesel engines is well- known, however the price of the bio-diesel is still higher than conventional diesel oil (DO) by 10% to 15% depending on a kind of bio-oil and a country producing the bio-diesel. One of idea to reduce the price of bio-diesel is to use the pure bio-oil as fuel for marine diesel engines, because to use the pure bio-oil as fuel without the esteritification process can reduce the price of bio-fuel. At present time, some experts in some countries who have been carrying out experiments on the use of pure bio-oil produced from rape seeds, sunflower seeds... as fuel for marine diesel engines have achieved important results. In recent years, at Vietnam Maritime University we also have been using the pure palm oil and its blended fuel (Palm oil and DO) as fuel for marine diesel engines in laboratory and on board of ships. The blended fuel is a mixing fuel of the pure palm oil and diesel oil with content of pure palm oil by 5%, 10%, 15%, 20% and 35%. In this paper, we would like to present some results from our experiments to investigate the impacts of using the palm oil and its blended fuel on the important technical features of the fuel supply system of marine diesel engines such as the fuel supply amount for one cycle, fuel supplying pressure, ignition delay time and so on. The results from the research will be good fundamental parameters to support proper operation of marine diesel engines using bio-oil and blended fuels as alternative fuel in near future.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.54-60
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• 2015

The autoignition temperature (AIT) of a material is the lowest temperature at which the material will spontaneously ignite. The AIT is important index for the safe handling of flammable liquids which constitute the solvent mixtures. This study measured the AITs of n-decane+ethylbenzene system by using ASTM E659 apparatus. The AITs of n-decane and ethylbenzene which constituted binary system were $210^{\circ}C$ and $430^{\circ}C$, respectively. The experimental AITs of n-decane+ethylbenzene mixture were a good agreement with the calculated AITs by the proposed equations with about $11^{\circ}C$ A.A.D.(average absolute deviation).

• Analytical Science and Technology
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• v.22 no.4
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• pp.285-292
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• 2009

It has been observed that, after long term storage, some ammunitions are misfired by tamping (combustionstopping) due to aging of the chemicals loaded in the ammunitions. Used in ammunitions are percussion powder which provides the initial energy, igniter which ignites the percussion powder, and a delay system that delays the combustion for a period of time. The percussion powder is loaded first, followed by the igniter and then the delay system, and the ammunitions explode by the energy being transferred in the same order. Tamping occurs by combustion-stopping of the igniter or insufficient energy transfer from the igniter to the delay system or the combustion-stopping of the delay system, which are suspected to be caused by low purity of the components, inappropriate mixing ratio, size distribution of particulate components, type of the binder, blending method, hydrolysis by the humidity penetrated during the long term storage, and chemical changes of the components by high temperature. Goal of this study is to find the causes of the combustion-stopping of the igniter and the delay system of the ammunitions after long term storage. In this study, a method was developed for testing of the combustion-stopping, and the size distributions of the particulate components were analyzed with field-flow fractionation (FFF), and then the mechanism of chemical change during long term storage was investigated by thermal analysis (differential scanning calorimetry), XRD (X-ray diffractometry), and XPS (X-ray photoelectron spectroscopy). For the ignition system, M (metal)-O (oxygen) and M-OH peaks were observed at the oxygen's 1s position in the XPS spectrum. It was also found by XRD that $Fe_3O_4$ was produced. Thus it can be concluded that the combustion-stopping is caused by reduction in energy due to oxidation of the igniter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.140-152
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• 1989

The study on the penetration of sprays during the initial phase of injection period, i.e. ignition delay period, in high speed small D.I. diesel engines are strongly affected by such behavior. To investigate the penetration of the sprays injected through single cylinderical orifice, a mathematical model was developed and compared with experimental results. In this model, radial heterogeneity of fuel density in the spray, transiency of injection pressure difference, and spray outrunning phenomenon were considered simultaneously. Experiments on the behaviors of sprays in the high pressure air chamber were conducted at various injection pressure differences and different levels of back air pressure. The behaviors of sprays injected into the chamber through the conventional Bosch injection pump were visualized with side stroboscopic illumination. Comparison of the experimental results with predictions from the mathematical model confirmed the validity of the model. It was also found that during the initial phase of the injection period the penetration of sprays vs. time appeared to have two transition points; one corresponded to disintegration point of liquid fuel jet, the other to the beginning of steady state injection.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.567-577
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• 2019

Due to the depletion of fossil fuels and environmental pollution, demand for alternative energy is gradually increasing. Among the various methods, a method to convert biomass into alternative fuel has been proposed. The bio-fuel obtained from biomass through pyrolysis process is called pyrolysis oil (PO) or bio-oil. Because PO is difficult to use directly in conventional engines due to its poor fuel properties, various methods have been proposed to upgrade pyrolysis-oil. The simplest approach is to mix it with conventional fossil fuels. However, due to their different polarity of PO and fossil fuel, direct mixing is impossible. To resolve this problem, emulsification of two fuels with a proper surfactant was proposed, but it costs additional time and cost. Alternatively, the use of alcohol fuels as an organic solvent significantly improve the fuel properties such as fuel stability, calorific value and viscosity. In this study, blends of diesel, n-butanol, and coffee ground pyrolysis oil (CGPO) which is one of the promising PO, was applied to diesel generator. Combustion and emissions characteristics of blended fuels were investigated under the entire load range. Experimental results show that ignition delay is similar to that of diesel at high load. Although, hydrocarbon and carbon monoxide emissions are comparable to diesel, significant reduction of nitrogen oxides and particulate matter emissions were observed.