• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3282-3287
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• 2007

Lean combustion is one of the most promising method for increasing engine efficiency and reducing the exhaust emission from SI gas engines. Due to the possibility of partial burn and misfire, however, under lean burn operation, stable flame kernel formation and fast burn rate are needed to guarantee a successful subsequent combustion. Experiment data were obtained on a single-cylinder CNG fueled SI engine to investigate the effect of direct injection, spark timing and variation of injection timing. Experimental results show that lean burn limit is ${\lambda}$=1.3 with port injection, and expansion of lean burn limit ${\lambda}$=1.4 with direct injection method, due to increase of turbulence intensity in cylinder and stratified charge. Combustion duration in lean region is improved by using the variation of injection timing.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.96-103
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• 2014

Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investigate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a function of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.32-42
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• 1998

Lean burn gasoline engine is recognized as a promising way to meet better fuel economy. Lean burn engine is classified into port injection and direct injection(DI), DI is more active technique for improving fuel economy with ultra-lean operation, Nowadays, port injected lean burn engine has been produced by many Japan maker. Also, DI engine is also possible for production owing to improvement in control technique of spray, flow air fuel ratio. DI engine uses either homogeneous stoichiometric mixture or stratified mixture by controlling injection timing to be early or late respectively. HM(homogeneous mixture) is worse than SM(stratified mixture) in view of ultra-lean operation in partical load and Nox reducion by using EGR control. But, HM has advanteges in cold starting and emission reduction during transient operation, This paper describes experimental variables and bench test results of HM GDI engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.98-104
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• 2014

The technologies employing spray-guided type combustion system for ultra-lean combustion direct injection engine is focused as a promising technology for satisfying emission regulations and improving fuel economy. In the present study, control and design optimization of lean-burn LPG direct injection engine was carried out with control strategy and injection position changes. Inter-injection spark ignition strategy was applied and the effect of the strategy was assessed at relatively higher load operation condition than previous researches. In order to create richer mixture in the vicinity of spark plug electrode, relative distance between the dead-end of injector and the electrode of spark plug was changed.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.39-45
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• 2012

Today gasoline engines for vehicular application are not only faced with stringent emission regulation but also with increasing requirements to better fuel economy, while guaranteeing power density. The spray-guided type gasoline direct injection (GDI) engine has an advantage of improved thermal efficiency and lower harmful emissions. Centrally mounted high pressure injector and adjacent spark plug allow stable lean combustion due to the flexible mixture stratification. In the present study, the performance and emissions characteristics of developed spray-guided type GDI combustion system were evaluated at various excess air ratio conditions. The specific fuel consumption and nitrogen oxides ($NO_x$) emissions were reduced due to the achievement of stable lean combustion under flammability limit. Multiple injection strategy was not helpful to improve fuel consumption while further reduction of $NO_x$ emissions was possible.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.137-143
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• 2012

Currently, in order to meet the reinforced emissions regulations for harmful exhaust gas including carbon dioxide ($CO_2$) as a greenhouse gas, technologies for reducing $CO_2$ emission and fuel consumption are being developed. Gasoline direct injection (GDI) systems have the advantage of improved fuel economy and higher power output than port fuel injection gasoline engine systems. The aim of this study is to examine the performance and emission characteristics of a lean burn GDI engine equipped with spray-guided-type combustion system. Stable lean combustion was achieved with a late fuel injection strategy under a constant operating condition. Further improvement in specific fuel consumption is possible with the introduction of multiple fuel injection strategies, which also increases hydrocarbon (HC) and nitrogen oxide ($NO_x$) emissions and decreases carbon monoxide (CO) emission.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.3
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• pp.204-211
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• 2019

The analysis on two-phase flow in a Lean Direct Injection(LDI) combustor has been investigated. Linearized Instability Sheet Atomization(LISA) and Aerodynamically Progressed Taylor Analogy Breakup(APTAB) breakup models are applied to simulate the droplet breakup process in hollow-cone spray. Breakup model is validated by comparing penetration length and Sauter Mean Diameter(SMD) of the experiment and simulation. In the LDI combustor, Precessing Vortex Core(PVC) is developed by swirling flow and most droplets are atomized along the PVC. It has been confirmed that all droplets have Stokes number less than 1.0.

• Journal of the Korean Society of Safety
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• v.13 no.3
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• pp.3-10
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• 1998

In general, the stratified charge for direct injection gasoline engine should be introduced to achieve ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, a reflector was adapted on cylinder head. An installation of the reflector in front of the injector nozzle leads the mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally ich to ignite while the lean mixture is wholly introduced into the combustion chamber. In this paper, the characteristics of combustion is analyzed with the variations of injection pressure and load in a stratified-charge direct injection single cylinder gasoline engine.

• 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 Mechanical Engineers B
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• v.39 no.1
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• pp.45-51
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• 2015

In order to meet the enforced emission regulations and reduce fuel consumption, various new technologies are employed in engines. The problem of NOx emissions under a lean mixture condition should be solved, because a lean-burn direct-injection engine can realize stable lean combustion with a stratified mixture, which results in improvements in fuel economy and emissions. This study investigated the effects of intake and exhaust valve timing changes on the performance and emission characteristics of a lean-burn LPG direct-injection engine. Under a partial-load operating condition without throttling, an increase in the intake valve opening led to an increase in NOx emissions due to an increase in the amount of excess air. The fuel consumption deteriorated with an increase in the exhaust valve opening due to a decrease in the expansion work and an increase in the pumping loss.