• Journal of ILASS-Korea
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• v.19 no.1
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• pp.1-8
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• 2014

Liquefied petroleum gas (LPG) is regarded as an alternative fuel for spark ignition engine due to similar or even higher octane number. In addition, LPG has better fuel characteristics including high vaporization characteristic and low carbon/hydrogen ratio leading to a reduction in carbon dioxide emission. Recently, development of LPG direct injection system started to improve performance of vehicles fuelled with LPG. However, spray characteristics of LPG were not well understood, which is should be known to develop injector for LPG direct injection engines. In this study, effects of operation condition including ambient pressure, temperature, and injection pressure on spray properties of n-butane were evaluated and compared to gasoline in a multi-hole injector. As general characteristics of both fuels, spray penetration becomes smaller with an increase of ambient pressure as well as a reduction in the injection pressure. However, it is found that evaporation of n-butane was faster compared to gasoline under all experimental condition. As a result, spray penetration of n-butane was shorter than that of gasoline. This result was due to higher vapor pressure and lower boiling point of n-butane. On the other hand, spray angle of both fuels do not vary much except under high ambient temperature conditions. Furthermore, spray shape of n-butane spray becomes completely different from that of gasoline at high ambient temperature conditions due to flash boiling of n-butane.

• Journal of Power System Engineering
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• v.12 no.4
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• pp.5-11
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• 2008

The RI gasoline engine haying a sub-chamber had a high cycle variation due to the difficulty of the residual gas scavenge in the sub-chamber. To solve this problem and improve the combustion performance of RI engine, we devised a method to inject directly CNG fuel into the sub-chamber. A DI diesel engine of single cylinder was converted into a RI-CNG engine and an electronic control unit for the engine was manufactured. In this study, the combustion characteristics of the RI-CNG engine were investigated with the injection timings and air excess ratios at the load conditions of 50% throttle open rate and 1700rpm. As the results from this study, the RI-CNG engine worked reliably under the condition of the ignitable lean limit of $\lambda=1.7$ by showing the $COV_{imep}$ below about 5%. And the highest thermal efficiency could be obtained in the injection timing that produced the high imep and the low $COV_{imep}$ at the same time. The CO emission concentration indicated very low values and the THC and $NO_x$ showed an opposite pattern. With a view to improving the thermal efficiency and reducing the harmful emissions, the proper control region of the ignition timing and the mixture ratio were nearly ATDC $20^{\circ}\sim50^{\circ}$ and $\lambda=1.4$ respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.383-390
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• 2013

The reduction of the maximum acceleration which causes shock for a missile is very important to prevent abnormal operation of a missile and decrease size and cost of missile components. Because the maximum acceleration created by operation of an ejection gas generator occurs in the initial ejection stage, the design parameters which affect initial ejection stage were examined. The igniter and the nozzle closure were selected as design parameters of a gas generator. The maximum acceleration created by the gas generator was examined experimentally by changing of the design parameters. Finally the reduction effect of the maximum acceleration was compared quantitatively by static fire test of a gas generator. The maximum acceleration of the best model which was applied to each optimal design parameter was about 68% reduced than that of the reference model.

• The KIPS Transactions:PartD
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• v.9D no.6
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• pp.1119-1126
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• 2002

In this paper, we propose two predictive spatial data mining based on spatial statistics and apply for predicting the forest fire hazardous area. These are conditional probability and likelihood ratio methods. In these approaches, the prediction models and estimation procedures are depending un the basic quantitative relationships of spatial data sets relevant forest fire with respect to selected the past forest fire ignition areas. To make forest fire hazardous area prediction map using the two proposed methods and evaluate the performance of prediction power, we applied a FHR (Forest Fire Hazard Rate) and a PRC (Prediction Rate Curve) respectively. In comparison of the prediction power of the two proposed prediction model, the likelihood ratio method is mort powerful than conditional probability method. The proposed model for prediction of forest fire hazardous area would be helpful to increase the efficiency of forest fire management such as prevention of forest fire occurrence and effective placement of forest fire monitoring equipment and manpower.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.21 no.2
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• pp.157-166
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• 1985

The Purpose of this study are to investigate the characteristics of the flame behavior of gasoline-methanol blended fuels in spark ignition engine. Ionization probe were installed at the cylinder head and piston in order to measure flame speed. Other parameter such as engine performance, fuel consumption rate and exhaust gas were measured. The results were as follows. 1. In the case of increase methanol contents in blend fuel, flame propagation speed were increased, and thermal efficiency of the engine were increased due to decrease of energy consumption rate. 2. In the case of fixed equivalance ratio, NO sub(X) in exhaust gas were increased in accordance with increase of spark advance, and mean effective pressure were decreased in accordance with increase of methanol contents. 3. CO and HC concentration were decreased in accordance with increase of methanol contents.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.105-113
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• 2009

The performance of a direct-injection type diesel engine often depends on the strength of swirl or squish, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the combustion in the cylinder was affected by the mixture formation process. In this paper, combustion process of biodiesel fuel was studied by employing the piston which has several grooves with inclined plane on the piston crown to generate swirl during the compression stroke in the cylinder in order to improve the atomization of high viscosity fuel such as biodiesel fuel and toroidal type piston generally used in high speed diesel engine. To take a photograph of flame, single cylinder, four stroke diesel engine was remodeled into two stroke visible engine and high speed video camera was used. The results obtained are summarized as follows; (1) In the case of toroidal piston, when biodiesel fuel was supplied to plunger type injection system which has very low injection pressure as compared with common-rail injection system, the flame propagation speed was slowed and the maximum combustion pressure became lower. These phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of swirl groove piston, early stage of combustion such as rapid ignition timing and flame propagation was activated by intensifying the air flow in the cylinder. (3) Combustion process of biodiesel fuel was improved by the reason mentioned in paragraph (2) above. Consequently, the swirl grooves would also function to improve the combustion of high viscosity fuel.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.48-55
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• 2018

It has recently been reported that methanol fuel has been used in the product carrier with established duel fuel engine, which has been greatly reducing emissions of $CO_2$, NOx and SOx from the engine. However, to use methanol alone as fuel oil in a general diesel engine, design modification of cylinder head is needed because the ignition aid device or the duel fuel injection system is needed. On the other hand, only if the mixer is installed on the fuel oil supply line, diesel oil - methanol blending oil can be used as fuel oil for the diesel engine, but there is a problem of the phase separation when two fuels are mixed. In this study, diesel oil and methanol were blended compulsorily in preventing the phase separation with installing agitators and a fuel oil boost pump on fuel line of a test engine. Also, cylinder pressure and fuel consumption quantity were measured according to engine load and methanol blending ratio, and indicated mean effective pressure, heat release rate and combustion temperature obtained from the single zone combustion model were analyzed to investigate the effects of latent heat of vaporization of methanol on combustion stability and characteristics. As a result, the combustion stability and characteristics of 10% methanol blending oil are closest to the those of diesel oil, and it could be used as fuel oil in existing diesel engines without deterioration of engine performance and combustion characteristics.

• Fire Science and Engineering
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• v.28 no.2
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• pp.48-53
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• 2014

In this study, we would evaluate fire risk by domestic standard for artificial turf installed on field and roofs. Today domestic regulation for artificial turf only applies to outdoor uses and especially KS M 3888-1 has compulsion but limited to school athletic facilities. Indoor regulation complying with National Emergency Management Agency (No. 2012-35) was enacted as recommendations. Thus this study did combustion test of artificial turf installed on field. Analyzed result by 45 degree flammability test, standard was inadequate to judge the fire risk so we compared and analysed its characteristic through combustion test of flame retardant finishing carpet used as flooring. Test and assessment result of its ignitionability by 45 degree flammability test showed that carpet was satisfied with flame retardant finishing performance standard contrary to artificial turf. For this reason, by conducting cone calorimeter test, the combustion property after ignition would be analyzed and evaluated and then this study will suggest a countermeasure for strengthening standard.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.3
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• pp.103-111
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• 2006

The spray behavior of direct-injection spark-ignition(DISI) engines is crucial for obtaining the required mixture distribution for optimal engine combustion. The spray characteristics of DISI engines are affected by many factors such as piston bowl shape, air flow, ambient temperature, injection pressure and fuel temperature. In this study, the effect of fuel temperature on the spray and combustion characteristics was partially investigated for the wall-guided system. The effect of fuel temperature on the fan spray characteristics was investigated in a steady flow rig embodied in a wind tunnel. The shadowgraphy and direct imaging methods were employed to visualize the spray development at different fuel temperatures. The microscopic characteristics of spray were investigated by the particle size measurements using a phase Doppler anemometry(PDA). The effect of injector temperature on the engine combustion characteristics during cold start and warming-up operating conditions was also investigated. Optical single cylinder DISI engine was used for the test, and the successive flame images captured by high speed camera, engine-out emissions and performance data have been analyzed. This could give the way of forming the stable mixture near the spark plug to achieve the stable combustion of DISI engine.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1317-1324
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• 1998

In general, DI gasoline engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance and lower emissions due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, some kinds of methodologies have been adapted in various papers. In this study, a reflector was adapted around the injector nozzle to apply the concept of stratified charge combustion which leads the air-fuel mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally rich to ignite while the lean mixture is wholly introduced into the combustion chamber. The characteristics of combustion is analyzed with the variations of fuel injection pressure and load in a stratified -charge direct injection single cylinder gasoline engine. The obtained results are summarized as follows ; 1. The MBT spark timing approached to TDC with the increase of load on account of the increase of evaporation energy, but has little relation with fuel injection pressure. 2. The stratification effects are apparent with the increase of injection pressure. It is considered by the development of secondary diffusive combustion and the increase of heat release of same region, but proceed rapidly than diesel engine. Especially, in the case of high pressure injection (l70bar) and high load (3.0kgf m), the diffusive combustion parts are developed excessively and results in the decrease of peak pressure than in the case of middle load. 3. The index of engine stability, COVimep value, is drastically decreased with the increase of load. 4. To get better performance of DI gasoline engine development, staged optimizaion must be needed such as injection pressure, reflector, intake swirl, injection timing, chamber shape, ignition system and so on. In this study, the I50bar injection pressure is appeared as the optimum.