• 오토저널
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• 제23권3호
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• pp.69-71
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• 2001

• International Journal of Automotive Technology
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• 제7권4호
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• pp.407-413
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• 2006

The liquefied petroleum gas(LPG), mixture of propane and butane, has the potential to reduce toxic hydrocarbon emissions and inhibit ozone formation due to its chemical composition. Conventional mixer systems, however, have problems in meeting the future lower emission standards because of the difficulty in controlling air-fuel ratio precisely according to mileage tar accumulation. Liquid Phase LPG injection(LPLi) system has several advantages in more precise fuel metering and higher engine performance than those of the conventional mixer type. On the other hands, leakage problem of LPLi system at the injector tip is a main obstacle for meeting more stringent future emission regulations because these phenomena might cause excessive amount of THC emission during cold and hot restart phase. The main focus of this paper is the development of a leaked fuel recirculation system, which can eliminate the leaked fuel at the intake system with the activated carbon canister. Leaked fuel level was evaluated by using a fast response THC analyzer and gas chromatography. The result shows that THC concentration during cold and hot restart stage decreases by over 60%, and recirculation system is an effective method to meet the SULEV standard of the LPLi engine.

• 한국자동차공학회논문집
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• 제17권2호
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• pp.82-89
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• 2009

In order to investigate the spray characteristics according to diesel and bioethanol blending with biodiesel fuel, macroscopic spray characteristics were analyzed from the comparison of the effect of the injection pressure, ambient pressure and density on the spray tip penetration and spray cone angle. In addition, spray atomization characteristics were studied with local and overall Sauter mean diameter (SMD) and the contour map of SMD distribution at various injection conditions. It was revealed that the spray tip penetration of biodiesel fuels blended with diesel and ethanol was shorter than that of an undiluted biodiesel fuel at low injection pressure. However, the difference of spray tip penetration among three test fuels reduces at a high injection pressure. Increase of the ambient gas density leads to the decrease of the spray tip penetration of three test fuels. When diesel and ethanol fuels add to an undiluted biodiesel fuel, spray cone angle increases due to the decrease of the fuel density at the same ambient pressure condition. On the other hand, the droplet mean diameter decreases due to the reduction of the kinematic viscosity and surface tension.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.115-122
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• 2006

To evaluate the durability characteristics of in-direct injection diesel engine using BDF 20(a blend of 20% biodiesel fuel and 80% diesel fuel in volume), an IDI diesel engine used to commercial vehicle was operated on BDF 20 for 300 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the combustion characteristics, engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. From the results, the combustion variations such as the combustion maximum pressure($P_{max}$) and the crank angle at which this maximum pressure occurs(${\Theta}_{Pmax}$) were not appeared during long-time dynamometer testing. Also, BSFC with BDF 20 resulted in lower than with diesel fuel. The peak pressure with BDF 20 was higher than that with diesel fuel due to the oxygen content in BDF. And, BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with a little increase of oxides of nitrogen than diesel fuel. It was concluded that there was no unusual deterioration of the engine, or any unusual change in exhaust emissions during the durability test of an IDI diesel engine using BDF 20.

• 오토저널
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• 제13권2호
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• pp.42-49
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• 1991

This study is to investigate the dispersion characteristics of diesel fuel spray in the initial stage of the beginning of the injection under the condition of room temperature and atmospheric pressure. It is difficult to analyse that the diesel fuel spray in diesel engine has unsteady intermittent spray. So author installed a fuel accumulator and an electromagnetic controller in order to keep the constant fuel injection rate with the time variation. With this modified fuel injection system, spray tip penetration, spray angle and initial spray development process are investigated by instantaneous photographic method. The results obtained in this study are as follows : 1) The initial shape of injection of diesel fuel spray shows the form of non-disintegrated intact core, but the formation of ligaments increasingly grows as the time increases. It can also be shown that fine droplets become disintegrated out from the ligaments. 2) The slope of spray tip penetration was changed to two different tendencies with time. The transition point of the slope is shown at the time of around between 0.09 msec and 0.4 msec from the beginning of injection. This is transition time from non-disintegrated intact core to formation of ligaments.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.128-135
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• 2008

EGR(exhaust gas recirculation) is considered as a most effective method to reduce the NOx emissions. But high EGR tolerance is always pursued not only for its advantages of the pumping loss reduction and fuel economy benefit in Gasoline-Hybrid engine. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel efficiency, combustion stability, engine performance and exhaust emissions. With optimal EGR rates, the fuel consumption was improved by 4%. This improvement was achieved while a reduction in NOx emissions of 75% was accomplished. Increase of EGR gas temperature causes the charge air temperature to affect the knock phenomenon and moreover, the EGR valve lift changes for the same control signal.

• 동력기계공학회지
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• 제18권5호
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• pp.11-15
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• 2014

Currently, there are active researches being conducted on a new combustion technology that can reduce emission quantity while enhancing vehicle performance as well as Improving fuel quality. In a gasoline engine that uses petroleum, high volatility makes it easy to jump spark ignition and prevent knocking phenomenon that occurs inside an engine. In a diesel engine that uses diesel fuel, high volatility reduces combustion residues and toxic gas and is therefore good for protecting the environment. Therefore, for fuel used in a vehicle, volatility is an important factor that influences not only engine performance but also environmental protection. This research conducted a distillation experiment using gasoline and diesel fuel for vehicles produced by domestic oil companies. The test was conducted in accordance with the method of distillation experiment described in KS M ISO3405. In addition, it used the result of analysis from the experiment to examine visual distillation characteristics of each fuel and developed a formula based on distillation temperature.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.1-11
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• 2004

Combustion and fuel distribution characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine, Swirl ratio were varied between 1.2, 2.3, and 3.4 following Ricardo swirl number(Rs) definition, Rs=2.3 showed the best results with lower cycle-by-cycle variation and shorter burning duration in the lean region while strong swirl(Rs=3.4) made these worse for combustion enhancement. Excessive swirl resulted in reverse effects due to high heat transfer and initial flame kernel quenching. Fuel injection timings were categorized with open valve injection(OVI) and closed valve injection(CVI). Open valve injection showed shorter combustion duration and extended lean limit. The formation of rich mixture in the spark plug vicinity was achieved by open valve injection. With higher swirl strength(Rs=3.4) and open valve injection, the cloud of fuel followed the flow direction and the radial air/fuel mixing was limited by strong swirl flow. It was expected that axial stratification was maintained with open-valve injection if the radial component of the swirling motion was stronger than the axial components. The axial fuel stratification and concentration were sensitive to fuel injection timing in case of Rs=3.4 while those were relatively independent of the injection timing in case of Rs=2.3.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.54-66
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• 2000

A gasoline direct injection single cylinder engine has been developed to study operational characteristics for highly stratified conditions. Parameters related to design and experiment were also studied to understand the characteristics of combustion and emissions at some part load conditions. It was found that optimal timings between the end of fuel injection and spark ignition were existed for stable combustion under the stratified modes, In a low engine speed, fuel spray behavior around piston bowl was important for stable combustion. The in-cylinder air motion affecting fuel spray behavior was found to be a dominant factor at higher engine speed as fuel injection timing had to be advanced to secure enough time for fuel evaporation and mixing with surrounding air. As swirl ratio increased, spark timing could be advanced for stable combustion and a higher compression ratio could be used for improved fuel consumption and stable combustion at the stratified mode. It was also observed that electrode geometry and piston bowl shape played an important role for combustion and emission characteristics and some results were shown for comparison.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.134-139
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• 2008

This research investigated variations of the engine performance and the exhaust emission characteristic of a direct injection diesel engine by fueling a commercial diesel fuel, which was blended with the di-ether group (butyl-ether: BE). The smoke emission reduced to 26% from the diesel engine with the blending fuel (diesel fuel 80 vol-% + BE 20 vol-%)at the full engine load of 2500 rpm compared to it with the diesel fuel only. The power, torque and brake specific energy consumption of the diesel engine showed very slight differences. The NOx emission from the diesel engine, however, with the blended fuel was higher than with the commercial diesel fuel only. By applying EGR method, as a counter plan of the NOx reduction, this research obtained reductions of the smoke and NOx emission at the same time from the diesel engine with the BE blended diesel fuel.