• Journal of the Korean Society of Combustion
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• v.22 no.1
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• pp.1-7
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• 2017

This paper presents an experimental study on the effect of double injection strategies on combustion characteristics in a single-cylinder diesel engine. These studies are applied to the double injection strategies, such as $2^{nd}$ injection timing variations with fixed injection interval (8 degree) and variations of injection pressures with fixed injection timing and intervals. The injection quantity was 7 + 7 mg for double injections, and 14 mg for single injection. When the injection pressure was increased, the ignition delay was shortened, and the ISFC (indicated specific fuel consumption) was increased due to the fast termination of combustion by the shortened energizing duration. In addition, the retardation of injection timings toward TDC (top dead center) caused the reduction of ignition delay and the decrease of ISFC with the decrease of FMEP (friction mean effective pressure).

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.114-122
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• 1997

Nowadays, gasoline direct injection engines are being commercialized by virtue of improvement in control technology of spray, flow, air fuel ratio. The stratified charge type has the advantage of improving lean limit. The homogeneous type has the advantage of reducing engine-out hydrocabon emissions in the first 30 seconds after a cold start, in addition, improving transient air fuel ratio control. The vaporization and mixing if injected fuel with air has to e completed in a short time and the fuel film in cylinder and on piston has to be minimized. So, the flow and injection should be well controlled. This paper surveyed the spray characteristics of gasoline direct injection by using laser equipment and the combustion characteristics of the single cylinder engine using homogeneousas-mixture type gasoline direct injection.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.23-32
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• 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
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• v.16 no.1
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• pp.7-14
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• 2011

High pressure LPG fuel spray with a conventional swirl injector was visualized and the impact of the injection pressure was also investigated using a DISI (direct injection spark ignition) LPG single cylinder engine. Engine performance and emission characteristics were evaluated over three different injection pressure and engine loads at an engine speed of 1500 rpm. The fuel spray pattern appeared to notably have longer penetration length and narrower spray angle than those of gasoline due to its lower angular momentum and rapid vaporization. Fuel injection pressure did not affect combustion behaviors but for high injection pressure and low load condition ($P_{inj}$=120 bar and 2 bar IMEP), which was expected weak flow field configuration and low pressure inside the cylinder. In terms of nano particle formation the positions of peak values in particle size distributions were not also changed regardless of the injection pressure, and its number densities were dramatically reduced compared to those of gasoline.

• International Journal of Automotive Technology
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• v.6 no.1
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• pp.1-8
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• 2005

Recently, the HSDI (High Speed Direct Injection) diesel engine has been spotlighted as a next generation engine because it has a good potential for high thermal efficiency and fuel economy. This study was carried out to investigate the in-cylinder flow characteristics generated in a HSDI diesel engine with a 4-valve type cylinder head. The four kinds of cylinder head were manufactured to elucidate the effect of intake port geometry on the in-cylinder flow characteristics. The steady flow characteristics such as coefficient of flow rate $(C_{f})$, swirl ratio (Rs), and mass flow rate (m,) were measured by the steady flow test rig and the unsteady flow velocity within a cylinder was measured by PIV. In addition, the in-cylinder flow patterns were visualized by the visualization experiment and these results were compared with simulation results calculated by the commercial CFD code. The steady flow test results indicated that the mass flow rate of the cylinder head with a short distance between the two intake ports is $13\%$ more than that of the other head. However, the non-dimensional swirl ratio is decreased by approximately $15\%$. As a result of in-cylinder flow characteristics obtained by PIV and CFD calculation, we found that the swirl center was eccentric from the cylinder center and the position of swirl center was changed with crank angle. As the piston moves to near the TDC, the swirl center corresponded to the cylinder center and the velocity distribution became uniform. In addition, the results of the calculation are in good agreement with the experimental results.

• Journal of the korean Society of Automotive Engineers
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• v.2 no.1
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• pp.39-50
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• 1980

This paper presents the variations obtained in heat flow rate and engine performance of a four-stroke cycle Diesel engine when there were changes in the temperature of cooling water, compression ratio, injection timing of fuel, and other factors. Heat dissipation of engine cylinder was calculated by the heat transfer coefficient of Nusselt's empirical equation and the analysis of distribution of temperature in cylinder barrel was obtained by the finite element method of two-dimensional steady state heat conduction. In this experiment, the out side temperature of cylinder liner was measured by the data logger, and the temperature distribution of liner was computed by the analysis of triangular finite element model under the assumption due to surface heat flux of cylinder inner surface. The results obtained by this study are as follows. Under the given operating condition, the temperature distribution of cylinder liner by using finite element method shows that the mean temperature of barrel is in accordance with the experimental results of Eichelberg and temperature difference is lower than 4.23.deg. C. The heat dissipation of engine decrease in accordance with the decrease of piston mean velocity, compression ratio, and the increase of coolant temperature. Influence on the delay of injection timing of fuel brings about the decrease of heat rejection over the cylinder at constant test conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.27-33
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• 1993

Using the solenoid driven gas injection valve, Hydrogen fuel supply system was made. It was attached to a single cylinder research engine and intake port injection type hydrogen fueled S.I. engine was constructed. Engine performance, emission characteristics, and abnormal combustion were studied through the engine test performed with the variations of fuel-air equivalence ratio and spark timing. Compared with gasoline, hydrogen burns so fast that cylinder peak pressure and temperature are higher and NO is emitted more at full load condition. IN the case of intake port injection type engine, COVimep becomes lower due to the well-mixing of air and fuel, and engine output is lower owing to the low volumetric efficiency. As fuel-air equivalence ratio goes up, the combustion speed increases, and COVimep decreases. NO emission peaks slightly lean of stoichiometric. As spark timing advances and fuel-air equivalence ratio goes up, the cylinder peak pressure and temperature become higher, so abnormal combustions take place easily.

• Journal of ILASS-Korea
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• v.14 no.3
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• pp.109-116
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• 2009

The purpose of this study is the experimental and numerical investigation on the DME spray characteristics in the combustion chamber according to the injection timing in a common-rail injection system. The visualization system consisted of the high speed camera with metal halide lamp was used for analyzing the spray characteristics such as spray development processes and the spray tip penetration in the free and in-cylinder spray under various ambient pressure. In order to observe the spray characteristics as a function of injection timing, the piston head shape of re-entrant type was created and the fuel injected into the chamber according to various distance between nozzle tip and piston wall in consideration of injection timing. Also, the spray and evaporation characteristics in the cylinder was calculated by using KlVA-3V code for simulating spray development process and spray tip penetration under real engine conditions. It was revealed that the high ambient pressure of 3 MPa was led to delay the spray development and evaporation of DME spray. In addition, injected sprays after BTDC 20 degrees entered the bowl region and the spray at the BTDC 30 degrees was divided into two regions. In the calculated results, the liquefied spray tip penetration and fuel evaporation were shorter and more increased as the injection timing was retarded, respectively.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.33-38
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• 2002

An optical single cylinder diesel engine equipped with a common-rail injection system has been built to investigate diesel combustion and emission characteristics. Three optical widows (piston crown quartz for bottom view of the cylinder, upper piston quartz for allowing laser sheet and liner quartz for side view) have been placed in the optical engine to visualize spray characteristics and combustion process inside the cylinder. Before doing further research using various optical diagnostics with the optical engine, fundamental combustion experiments and flame visualization incorporating a high speed motion analyser have been carried out with a wide range of engine operating conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.2
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• pp.48-55
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• 2003

The effects of pressure charge on combustion stability and emissions have been analyzed using a GDI single cylinder engine. A late injection mode of stratified condition at the air-fuel ratio of 40:1 for 1200∼2400 rpm was tested while the boosted pressure ratio was increased up to 1.5:1. In-cylinder CFD analysis was also performed for better understanding of in-cylinder flow and fuel spray behavior. With a higher boosted pressure ratio the IMEP was increased greatly due to the increased engine load, and the ISFC was improved by more than 10% at all engine speeds. The regime of stable stratified combustion was extended to a higher engine speed, but the spark ignition angle had to be more advanced for stable combustion. The emissions of ISHC and ISNOx did not show a particular trend for the increased engine speed but a general trend of lower ISHC and higher ISNOx for a gasoline engine.