• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.247-253
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• 2003

Burning velocities of conventional methane flame and oxygen-enriched methane flame were determined by experimentally and numerically at atmospheric pressure in order to examine the validity of various detailed reaction mechanisms in oxygen-enriched flame. The schlieren system was adopted to obtain the burning velocity of flame stabilized on a circular nozzle. Premix code was employed to compute the burning velocity. Three reaction mechnisms were tested at several oxygen enrichment level, whose names are GRI 3.0, MB(Miller and Bowman) and LKY(Lee Ki Yong) reaction mechanism. Sensitivity analysis was also performed to discriminate dominantly affecting reaction on burning velociy. The results showed that conventional reaction mechanisms originally based on methane-air flame were underpredict the burning velocity at high oxygen-enrichment level. The modified GRI 3.0 reaction mechanism based on our experimental results was suggested and shows a good agreement in estimating the burning velocity and the NO number density of oxygen-enriched flame.

• Journal of ILASS-Korea
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• v.25 no.3
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• pp.111-118
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• 2020

This paper describes the effect of DME, biodiesel blended fuels on the macroscopic spray characteristics in a high pressure diesel injection system using Background Oriented Schlieren (BOS) method. The BOS method for visualization of impingement evaporation sprays to analyze macroscopic spray properties and evolutionary processes. In this work, the blending ratio of DME in the blended fuel are 0, 50, 100% by weight ratio. In order to investigate the macroscopic impinged spray characteristics under the various injection parameters and blending ratio. In this work, a mini-sac type single-hole nozzle injector with nozzle hole was length 0.7 mm and diameter of 0.3 mm was used. According to the result, the spray area of the collision wall increased as the DME mixing ratio increased, and the evolutionary pattern showed a stepwise increase due to the collision effect of the wall. Also, results of impinged spray area were increased according to increasing injection pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.1-10
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• 1996

In the present study, the structure and the characteristics of gaseous premixed flame impinging normal to the flat plate have been investigated experimentally. For the examination of the heat transfer and combustion characteristics, measurements of temperature, direct and schlieren photography were performed. The results of present study show that the length of inner flame becomes smaller as distance from nozzle exit to plate decrease. The width of flame becomes larger as air-fuel ratio decreases. The smaller Reynolds number at nozzle exit and the smaller distance from nozzle exit to plate lead to the higher heat transfer rate in the region of center of plate. As the air-fuel ratio decreases, the heat transfer at plate with moderate rate occurs on wide region.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2177-2183
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• 1994

The rapid expansion or condensible gas such as moist air of steam gives rise to nonequilibrium condensation. As a result of irreversibility of condensation process in the supersonic cascade flow of low pressure steam turbine, the entropy of the flow is increased, and the efficiency of the turbine is decreased. In the present study, to investigate the flow of moist air in 2-dimensional cascade made as the configuration of the tip section of the last actual steam turbine moving blade, the static pressure at both sides of pressure and suction of blade are measured by static pressure taps and the distribution of Mach number on both surfaces of the blade are obtained by using the measured static pressure. Also, the flow field is visualized by a schlieren system. From the experimental results, the effects of the stagnation temperature and specific humidity on the flow properties in a 2-dimensional stationary cascade of a practical steam turbine blade are clearly identified.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.6
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• pp.57-67
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• 1989

This paper deals with the experimental study of the turbulent flow fields by the hot-wire anemometer and the density fields by the Schlieren photography. In this study, the air mixed with CO$_{2}$ was used to visualize and to study this process and experimental parameters used were valve lift and valve shape. The results obtained are as follows: 1) The axial velocity of mixture flow passing a valve is changed greatly by valve seat angle and valve lift. Especially, it is changed more when the valve seat angles is 30.deg. and 45.deg. than when these are 60.deg. and 90.deg. 2) Experimental results by hot wire anemometer and Schlieren apparatus are very close together. The most satisfactory results are shown when the valve seat angle is 45.deg.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2611-2623
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• 1993

To construct the design back data for a lean-burn gas engine, we investigated the combustion characteristics in the main chamber using a constant volume combustion chamber with subchamber. The combustion characteristics with configuration change of the critical passageholes have been studied by taking pressure data, schlieren photograph, ion current and light emission signal of flame. Heat release rate with various critical passageholes also have been analysed by using the combustion model of a prechamber diesel engine. It was found that combustion characteristics in the main combustion chamber were greatly influenced by the geometric configurations of critical passagehole.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.121-130
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• 1999

It is necessary to measure pressure, temperature, chemical equilibrium and the shape of flame in order to understand the combustion process in a combustion chamber. In particular, the flame formulation and combustion process of divided combustion chamber are different from those of a single chamber, And the variable diameter of a jet hole can effect not only physical properties like ejection velocity, temperature and time of combustion but also a chemical property like the reaction mechanism. Accordingly temperature is one of the most important factors which influence the combustion mechanism. This paper observed shape of flame by using the schlieren photographs and measured the pressure in a combustion chamber and the reaching time of the flame by ion probe By doing these, we investigation the formulation of the flame and the process of propagation. These measurement methods can be advanced in understanding the combustion process and process and propagation of flame.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.1
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• pp.5-10
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• 2008

A flame speed of methane mixture of water vapor and air have been measured to study the process of flame propagation using schlieren photographs. The quantity of water vapor contained were changed 5% and 10% of total mixture, and equivalence ratio of mixture between 0.8 and 1.2 were tested under the ambient temperature 323K and 373K. The results showed that the burning velocity was decreased by increasing the water vapor contents due to the interruption of flame development. And, the reduction rate of burning velocity was smaller by increasing the water contents under the same ambient temperature. The effects of ambient temperature on burning velocity was decreased by increasing the water vapor contents.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.191-196
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• 2009

Experiments were conducted in a constant pressure combustion chamber using schlieren system to investigate the effects of carbon dioxide/nitrogen/helium diluents on cellular instabilities of syngas-air premixed flames at room temperature and elevated pressures. Laminar burning velocities and Markstein lengths were calculated by analyzing high-speed schlieren images at various diluent concentrations and equivalence ratios. Experimental results showed substantial reduction of the laminar burning velocities and of the Markstein lengths with the diluent additions in the fuel blends. Effective Lewis numbers of helium-diluted syngas-air flames increased but those of carbon dioxide- and nitrogen-diluted syngas-air flames decreased in increase of diluents in the reactant mixtures. With helium diluent, the propensity for cells formation was significantly diminished, whereas the cellular instabilities for carbon dioxide-diluted and nitrogen-diluted syngas-air flames were not suppressed.

• Journal of ILASS-Korea
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• v.20 no.3
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• pp.187-194
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• 2015

In this study, three visualization methods, Schlieren, Shadowgraph, and Mie-scattering, were applied to compare diesel and gasoline spray structures. Fuels were injected into a high pressure/high temperature constant volume chamber under the same ambient pressure and temperature condition of low load in gasoline direct injection compression ignition (GDCI) engine. Two injection pressures (40 and 80 MPa), two ambient pressures (4.2 and 1.7 MPa), and two ambient temperatures (908 and 677 K) were use. The images from the different methods were overlapped to show liquid and vapor phases more clearly. It was found that the gasoline fuel is more appropriate to form a lean mixture.