• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.106-113
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• 2016

Lean burn engine, classified into port injection and direct injection, is recognized as a promising way to meet better fuel economy. Especially, LPG direct injection engine is becoming increasingly popular due to their potential for improved fuel economy and emissions. Also, LPDi engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. However, LPDi engine has many difficulties to be solved, such as complexity of injection control mode (fuel injection timing, injection rate), fuel injection pressure, spark timing, unburned hydrocarbon and restricted power. This study is investigated to the influence of spark timing, fuel injection position and fuel injection rate on the combustion stability of LPDi engine. Piston shape is constituted the bowl type piston. The characteristics of combustion is analyzed with the variations of spark timing, fuel injection position and fuel injection rate (early injection, late injection) in a LPDi engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.6
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• pp.619-626
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• 2016

The new 1.4 L turbocharged LPG direct injection (T-LPDI) engine is presented in this paper to improve the fuel efficiency of the vehicles installed with the 2.0 L LPG port fuel injection (LPI) engine, while maintaining the performance as a downsizing concept for the new engine platform development. Firstly, the return type high pressure LPG fuel supply system is designed and mounted in the new 1.4 L T-LPDI engine. As a result, this new engine shows a much better WOT performance and approximately 8 % of improved fuel economy level, as compared to the 2.0 L LPI vehicle. Secondly, the LPDI engine specific optimized design for high pressure fuel components and fuel injection control strategies are proposed and evaluated in order to overcome the restartability problem in a heat-soaked condition called the vapor lock phenomenon. Consequently, these experimental results illustrate a great potential for the developed 1.4 L T-LPDI engine as a possible substitute for the 2.0 L LPI engine.

• Journal of ILASS-Korea
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• v.27 no.4
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• pp.211-218
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• 2022

Recent vehicle regulations have become increasingly stringent in order to reduce greenhouse gases. Then not only movement to replace internal combustion engine vehicles with hybrid vehicles, but also studies of replacing internal combustion engine fuels with low-pollution fuels are increasing. In this study, the characteristics of a vehicle with LPG fuel engine and mild hybrid system is investigated. To avoid shortage of maximum power on LPG engine, a direct injection system of LPG is applied. In addition, P0 mild hybrid system is adopted to enhence the efficiency of the vehicle. The vehicle model is developed in order to predict fuel economy and CO2 emission of LPDi MHEV.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.454-459
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• 2003

The one of the most important subject to develop a LPDi engine is to suppress the generation of bubble inside LPG direct injector. For the purpose of this, in this study, the analogy visualization injector to visualize the generation and behavior of bubble, is manufactured and the bubbling phenomenon and behaviors are visualized and studied. The bubble inside the injector is generated at injection hole and after rising by buoyancy, it disappear around the top of a nozzle. The number of bubble generated is little changed regardless of the lapse of time but it is increased remarkably as the temperature around the injector is increased. With injection, the temperature around the injector at which the bubble is generated in_cylinder is much lower than that without injection because the transient pressure drop of fuel by injection.

• Journal of ILASS-Korea
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• v.28 no.4
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• pp.191-197
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• 2023

LPG direct injection (LPDi) technology is a method of improving the weaknesses of existing LPG vehicles by directly injection into the combustion chamber. This study was conducted on the comparison of emissions and fuel efficiency performance of the engine and vehicle by applying LPDi technology. The LPDi hybrid engine's maximum output and maximum torque were measured at an equivalent level of less than 1% compared to conventional gasoline fuel. The fuel amount was corrected using the LCU controller, and the THC, CO, and NOx emissions were reduced to 90% in the operating range of the three-way catalyst through air-fuel ratio control. The analysis of THC+NOx and CO emissions in FTP-75 (CVS-75) driving mode satisfied the US LEV III SULEV30 regulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.1-8
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• 2006

One of the most important subjects to develop a LPDi engine is to suppress the bubble generated inside the liquid LPG direct injector. For the purpose of this, the analogy visualization injector to visualize the generation and behaviors of bubble is manufactured, and the bubbling phenomenon and behaviors of bubble are visualized and investigated according to the change of the temperature around an injector wall, fuel pressure and a needle configuration. As results, it was found that the bubble inside the injector is generated around an injector hole and after rising by buoyancy it disappears around the top of a nozzle. The number of bubbles generated is little changed regardless of the lapse of time but it remarkably increases as the temperature around the injector increases. Also, it was known that as the sac volume in LPDi injector decreases the generation of bubble is more active and the rising velocity of bubble generated is increased.