Chang Sik Lee

Experimental and numerical study on the combustion characteristics of partially premixed charge compression ignition engine with dual fuel

The objective of this work is to investigate the effect of premixed fuel ratio on the combustion and emission characteristics in diesel engine by the experimental and numerical method. In order to investigate the effect of various factors such as the premixed ratio, EGR rate, and equivalence ratio on the exhaust gas from the premixed charge compression ignition diesel engine, the injection amount of premixed fuel is controlled by electronic port injection system. The range of premixed ratio between dual fuels used in this study is between 0 and 0.85, and the exhaust gas is recirclulated up to 30 percent of EGR rate.

COMBUSTION AND EMISSION CHARACTERISTICS OF A PARTIAL HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE WHEN USING TWO-STAGE INJECTION

The focus of this study was an investigation for the realization of a partial homogeneous charge compression ignition (HCCI) combustion as a control mechanism for HCCI combustion. Premixed fuel was supplied using an in-cylinder early direct injection, and the second injection was made near the TDC to control the ignition and combustion rates of the premixed fuel. In order to obtain the optimal injection timing for the premixed fuel, combustion, and emission characteristics with respect to DI fuel injection timing was investigated in various operational ranges, from conventional diesel combustion to HCCI combustion. The results showed that two-stage injection was very effective in reducing NOx emissions from a DI diesel engine. Additionally, at an optimized injection timing, the ignition of premixed fuel can be controlled by the main injection without premature autoignition. Based on the experimental results, the effect of the premixed ratio and timings of the first and main injections on the combustion characteristics and exhaust emissions in a direct injection diesel engine were discussed.

Analysis of combustion and flame propagation characteristics of LPG and Gasoline fuels by laser deflection method

This work is to investigate the combustion characteristics and flame propagation of the LPG (liquified petroleum gas) and gasoline fuel. In order to characterize the combustion processes of the fuels, the flame propagation and combustion characteristics were investigated by using a constant volume combustion chamber. The flame propagation of both LPG and gasoline fuels was investigated by the laser deflection method and the high-speed Schlieren photography. The result of laser deflection method show that the error of measured flame propagation speed by laser method is less than5% compared with the result of high-speed camera. The flame propagation speed of the fuel is increased with the decrease of initial pressure and the increase of initial temperature in the constant volume chamber. The results also show that the equivalence ratio has a great effect on the flame speed, combustion pressure and the combustion duration of the fuel-air mixture.

Investigation of in-cylinder flow patterns in 4 valve S. I. Engine by using single-frame particle tracking velocimetry

The in-cylinder flow field of gasoline engine comprises unsteady compressible turbulent flows caused by the intake port, combustion chamber geometry. Thus, the quantitative analysis of the in-cylinder flow characteristics plays an important role in the improvement of engine performances and the reduction of exhaust emission. In order to obtain the quantitative analysis of the in-cylinder gas flows for a gasoline engine, the single-frame particle tracking velocimetry was developed, which is designed to measure 2-dimensional gas flow field. In this paper, influences of the swirl and tumble intensifying valves on the in-cylinder flow characteristics under the various intake flow conditions were investigated by using this PTV method. Based on the results of experiment, the generation process of swirl and tumble flow in a cylinder during intake stroke was clarified. Its effect on the tumble ratio at the end of compression stroke was also investigated.

Supercharging Performance of a Gasoline Engine with a Supercharger

Supercharging of intake air can improve the engine power and combustion characteristics by boosting the intake pressure above atmospheric pressure. In this work, the supercharging performance of a supercharged gasoline engine was discussed on the basis of experimental investigation. The investigation results showed that the output and torque performance of a supercharged engine were improved in comparison with the naturally aspirated engine. In the engine system with a supercharger, owing to supercharging of intake air into the cylinder, the combustion pressure, the rate of heat release, and the burning rate of fuel-air mixture were found to be higher than those of the naturally aspirated engine. In this paper, the effect of the drive pulley ratio and the pressure ratio of supercharger, and the other factors on the supercharging performance were also investigated.

A Study on the Characteristics of Combustion Variations of Compression Ignition Engine

This paper describes the results of a study of the variation of combustion characteristics in a precombusion chamber type water-cooled diesel engine. Statiscal analysis on cycle-by-cycle variation of combustion characteristics such as rate of pressure rise, heat release rate, and mass burning rate from combustion pressure-crank angle data of one thousand cycles were made under several operating conditions.The influence of engine speed and coolant temperature upon maximum frequency of combustion characteristics are discussed also.

The Effect of Combustion Parameters on the Nitric Oxide Emission in Direct Injection Type Diesel Engine

This paper presents the investigation of influence factors on the output performance and the reduction of exhaust emission in the direct injection type diesel engine. In this work, the analysis of combustion products and combustion characteristics are investigated by numerical method and experiment under the various engine operating conditions. The combusion performance and exhaust emissions are analyzed in terms of the heat release, cylinder pressure and major exhaust emissions of engine. The accuracy of the prediction versus experimental data and the capability of the heat release, cylinder pressure and all the major exhaust emissions are demonstrated. The results of this study show that the combustion parameters have influence on the combustion processes and the nitric oxide emission in the direct injection type diesel engine. The nitric oxide concentration decreases with the increase of engine speed and the advance of injection timing.

A Study on the Combustion Characteristics of Coaxial Jet Furnaces with Swirl Flow

This study is an analysis of the turbulent diffusion flame with swirl flow and the calculated results are compared with experimental data in cases of various swirl numbers and air-fuel ratios. The mathematical model is restricted to single-phase, diffusion controlled combustion with swirl flow. Values of local flow properties are obtained by solving appropriate differential equation for continuity, momentum, stagnation enthalpy, concentration, turbulence energy, dissipation rate of turbulence energy, and the mean square of concentration fluctuation. The method is proposed for calculating the local probability of chemical reaction on the use of the probability density function for the mixture fraction.