• Journal of ILASS-Korea
• /
• v.8 no.2
• /
• pp.1-6
• /
• 2003

The liquid phase LPG injection (LPLI) system (the third generation technology) has been considered as one of the next generation fuel supply systems for LPG vehicles, since it has a very strong potential to accomplish the higher power, higher efficiency, and lower emission characteristics than the mixer type(the second generation technology) fuel supply system However. when a liquid LPG fuel is injected into the inlet duct of an engine, a large quantity of heat is extracted due to evaporation of fuel. This leads to freezing of the moisture in the air around the outlet of a nozzle, which is called icing phenomenon. It may cause damage to the outlet nozzle of an injector or inlet valve seat. In this work, the experimental investigation of the icing phenomenon was carried out The results showed that the icing phenomenon and process were mainly affected by humidity of inlet air instead of air temperature in the inlet duel. Also, it was observed that the total ice formed around the nozzle weighs at about $150mg{\sim}260mg$ after injection for ten minutes. And some fuel species were found in the ice attached at the front side of a nozzle, while frozen ice attached at the back of a nozzle was mostly' consisted of moisture of inlet air. Therefore, some frozen ice deposit. detached from front nozzle of an injector, may cause a problem of unfavorable air fuel ratio control in the small LPLI engine.

• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.46-52
• /
• 2004

An LPG engine (KL6i) for heavy duty vehicle has been developed using liquid phase LPG injection (LPLi) system, which has regarded as one of next generation LPG fuel supply systems. For the KL6i engine, lean burn technology was introduced to minimize the thermal loading and NOx emissions due to an increase of the engine power. In this work, injection timing and piston bowl shape were investigated for the stabilization of lean burn characteristics. Experimental results reveals that fuel stratification induced by these parameters is most effective strategy to extend lean combustion limit in the LPLi system.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.4
• /
• pp.272-277
• /
• 2009

The liquid phase LPG injection (LPLi) system (the 3rd generation technology) has been considered as one of the most promising fuel supply systems for LPG vehicles. To investigate the reaction characteristics of LPG with rubber parts in LPLi system, various rubbers were tested. The results showed that the amount of residue from the cover rubber of a fuel pump was increased about 10 times after testing. Furthermore, the amount of sulfur and nitrogen species which are considered as main sources of deposit formation in LPLi fuel injectors were also found to be higher than those in original LPG fuel. In addition, these residues made the core parts of LPLi injector such as needle and nozzle, partially worn, which eventually causes leakage in LPLi injectors.

• Journal of ILASS-Korea
• /
• v.12 no.1
• /
• pp.38-44
• /
• 2007

Since the Liquid Phase LPG injection (LPLI) system has Advantages in power generation and emission characteristics compared to the mixer-type fuel-supply system, a variety of studies regarding LPLi system has been conducted and its applications are made in automobile industry. However, the heat extraction due to the evaporation of liquid fuel, causes not only a post-accumulation of fuel but also an icing phenomenon which is a frost of moisture in the air around the nozzle tip. Since there exists a difficulty in the accurate control of air fuel ratio in both fuel supply systems, it can result in poor engine performance and a large amount of harmful emissions. This research examines the characteristics of icing phenomenon and develops anti-icing bushing to prevent an icing on the surface of the injection tip. It was found that n-butane, which has a relatively high boiling point ($-0.5^{\circ}C$), was a main species of post-accumulation. Also the results show that the post-accumulation problem was allevaited the utilization of a large inner to outer bore ratio and smooth surface roughness. In addition, an icing phenomenon and its formation process were found to be mainly affected by the humidity and the temperature of inlet air in an inlet duct. Also, it was observed that an icing phenomenon is lessened using aluminum bushing whose end coincides with the end of fuel injection tip in length.

• 연구논문집
• /
• s.33
• /
• pp.5-16
• /
• 2003

Fuel distribution, combustion, and flame propagation characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine. Optically accessible single cylinder engine and laser diagnostics system were built for quantifying fuel concentration by acetone PLIF(planar laser induced fluorescence) measurements. In case of Otto cycle engine with large bore size, the engine knock and thermal stress of exhaust manifold are so critical that lean burn operation is needed to reduce the problems. It is generally known that fuel stratification is one of the key technologies to extend the lean misfire 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 Rs2.3. Thus, strong swirl flow could promote desirable axial fuel stratification and, in result, may make flame propagation stable in the early stage of combustion.

• Journal of the Korean Institute of Gas
• /
• v.16 no.2
• /
• pp.38-44
• /
• 2012

In recent years, the need for more fuel-efficient and lower-emission vehicles has driven the technical development of alternative fuels such as LPi (Liquid phase LPG injection) which uses pump for the high pressure supply of liquid LPG fuel and is able to meet the limits of better emission levels while it has an advantage of higher power. Although it has the advantage of power and lower emission levels, the characteristics of LPG, such as high vapor pressure, lower viscosity and surface tension than gasoline fuels makes it difficult design system. Therefore most fuel pumps and injectors are imported. In the present study, in order to domestically develop LPG injector which guarantees flow rates and optimal operation, the experimental investigation on leakage and flow rate characteristics of developed prototype injector was carried out at the bench test rig for developed injector.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.4
• /
• pp.23-32
• /
• 2002

Combustion and flame propagation characteristics of the liquid phase LPG injection (LPLI) engine were investigated in a single cylinder optical engine. Lean bum operation is needed to reduce thermal stress of exhaust manifold and engine knock in a heavy duty LPG engine. An LPLI system has advantages on lean operation. Optimized engine design parameters such as swirl, injection timing and piston geometry can improve lean bum performance with LPLI system. In this study, the effects of piston geometry along with injection timing and swirl ratio on flame propagation characteristics were investigated. A series of bottom-view flame images were taken from direct visualization using an W intensified high-speed CCD camera. Concepts of flame area speed, In addition to flame propagation patterns and thermodynamic heat release analysis, was introduced to analyze the flame propagation characteristics. The results show the correlation between the flame propagation characteristics, which is related to engine performance of lean region, and engine design parameters such as swirl ratio, piston geometry and injection timing. Stronger swirl resulted in foster flame propagation under open valve injection. The flame speed was significantly affected by injection timing under open valve injection conditions; supposedly due to the charge stratification. Piston geometry affected flame propagation through squish effects.

• Journal of ILASS-Korea
• /
• v.20 no.1
• /
• pp.35-42
• /
• 2015

This study is to investigate the spray behavior of DME-LPG blended fuels in common rail injection system for diesel engines. The visualization experiment was performed to analyze the macroscopic spray behavior of test fuels. In addition, the experiment using BOS(Background Oriented Schlieren) method is performed to compare liquid phase and gas phase. The test fuels are injected in high pressure chamber. The ambient pressure of high pressure chamber was formed by nitrogen gas. Spray tip penetration, spray cone angle and spray area were measured using high speed camera. SMD(Sauter Mean Diameter) and spray particle velocity were measured using the PDPA(Phase Doppler Particle Analyzer) system to analyze the microscopic properties of test fuels. The results of this experiment showed that spray tip penetration, spray cone angle and spray area of DME-LPG fuels are similar to those of DME fuel. When compared to results of experiment using BOS, significant differences of spray tip penetrations, spray cone angle and spray area are showed because of gas phase. The results of experiment using BOS method showed higher values. SMD of DME-LPG blended fuels is smaller than that of DME fuel. Velocity of DME-LPG blended fuels is faster than that of DME fuel.

• Journal of ILASS-Korea
• /
• v.15 no.1
• /
• pp.38-43
• /
• 2010

The LPG(Liquefied Petroleum Gas) fuel attracts attention as a clean alternative fuel. In order to further reduce the exhaust emission and improve performance in LPG engines, the LPLi(Liquid Phase LPG Injection) system is used. In LPLi system, the fuel pump performance is important for keeping the LPG over it's saturated vapor pressure. An external fuel pump is needed to improve the durability for LPG engines. This paper predicted the variation of fuel properties on the LPLi system with an external fuel pump. From each component's thermodynamic model, an 1-D simulation is developed for LPLi system with an external fuel pump. Then the 1-D simulation data analyzed and compared with the rig-test. The 1-D simulation and the rig-test produced similar results.

• Journal of Energy Engineering
• /
• v.24 no.4
• /
• pp.33-41
• /
• 2015

Dimethyl ether (DME) can be used as a clean diesel alternative fuel due to the high cetane number and low emission, it can also be applied to automotive fuel as a blended liquefied petroleum gas (LPG) because physical properties are similar to those of LPG. In this study, feasibility test of LPG vehicle using blended DME-LPG fuel was investigated. Three types of fuel supply such as LPLi (Liquid phase LPG injection), LPGi (Liquid phase gas injection) and mixer type were selected to consider the LPG fuel-injection system. The performance characteristics of LPG vehicle were examined by using LPG and blended DME-LPG fuel in order to compare the exhaust emissions (CO, THC, $NO_X$) and fuel economy. The emissions and fuel economy of DME-LPG blend fuel were comparable to those of LPG with increasing driving distance.