• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.1-7
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• 2010

Edge flames have been interested as a basic structure that is concerned to flame stabilization and re-ignition of non-premixed flames. The edge flame consists of a lean premixed flame, a rich premixed flame, and a diffusion flame. In order to investigate fundamental structures of the edge flames at the conditions near the flammability limits, edge flames were stabilized within a heated narrow channel. Highly diluted partially premixed methane was used, and the flow rates of air and the partially premixed mixture were controlled. Various flame behaviors, including a transition between ordinary edge flames and premixed flames, were observed. Flame stabilization characteristics were examined as well. All flame stabilization conditions in this study showed a similar trend: characteristic time scales were inversely proportional to the equivalence ratio defined at the burner inlet. Finally, an interesting flame structure having a weak diffusion branch enveloped by a closed premixed branch was found near the flammability limits even in a fuel-air mixing layer. This structure was named as a "flame-drop" and the importance of this structure was first suggested.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.20-26
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• 2000

In this experimental study, we examined gas engine characteristics of a small high-speed engine in various ways. And we studied performance of natural gas, hydrogen gas and gasoline fuel engines, as emission characteristics and process of combustion. For the purpose of preventing back-fire occurred in case of high-speed and high load in hydrogen engine, we controlled air quantity by installing throttle valve in gas fuel engine. We performed experiment by mixing nitrogen to hydrogen fuel. As a result, we could find out characteristics which of a high speed small engine by applying gas fuels.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.475-481
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• 2004

Recently it is strongly required on lower fuel consumption. lower exhaust emission, higher engine performance. and social demands in a spark ignition gasoline engine. In this study. the experimental engine used at test. it has been modified the lean burn gasoline engine. and used the programmable engine management system, and connected the controller circuit which is designed for the engine control. At the parametric study of the engine experiment, it has been controlled with fuel injection, ignition timing. swirl mode, equivalence ratio engine dynamometer load and speed as the important factors governing the engine performance adaptively. It has been found the combustion characteristics to overcome the hysteresis phenomena between normal and lean air-fuel mixing ranges. by mean of the look-up table set up the mapping values. at the optimum conditions during the engine operation. As the result, it is found that the strength of the swirl flow with the variation of engine speed and load is effective on combustion characteristics to reduce the bandwidth of the hysteresis regions. The results show that mass fraction burned and heat release rate pattern with crank angle are reduced much rather, and brake specific fuel consumption is also reduced simultaneously.

• Journal of the Korean Society of Combustion
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• v.3 no.2
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• pp.13-27
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• 1998

The optimization of frontal device including fuel nozzle and swirler is required to secure the mixing of fuel and air and the combustion stability leading the reduction of pollutant emissions and the increase of combustion efficiency in gas turbine combustor. The effects of injection nozzle and swirler on the flow field, spray characteristics and consequently the combustion stability, were experimentally investigated by measuring the velocity field, droplet sizes of fuel spray, lean combustion limit and the temperature field in the main combustion region. Flow fields and spray characteristics were measured with APV(Adaptive Phase Doppler Velocimetry) under atmospheric condition using kerosine fuel. Temperatures were measured by Pt-Pt13%Rh, R-type thermocouple which was 0.2mm thick. Spray and flame was visualized by ICCD(Intensified Charge Coupled Device) camera. It was found that the dual swirler resulted in the biggest recirculation zone with the highest reverse flow velocity at the central region, which lead the most stable combustion. The various combustion characteristics were observed as a function of the geometries of injector and swirler, that gave a tip for the better design of gas turbine combustor.

• Journal of ILASS-Korea
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• v.2 no.2
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• pp.8-15
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• 1997

Combustion chamber systems using spray impinged on walls have been studied for improving combustion characteristics in high speed direct injection diesel engines. The fuel spray injected in a small combustion chamber may be easily impinged and deposited on the wall. The fuel deposit has been considered as the cause for unburned emission due to difficulty of fuel-air mixing. In this paper w-shaped combustion chamber which has four raised pips on the side wall is introduced and discussed by comparing with conventional chamber with no pips. The computer code employing new spray-wall interaction model in general non-orthogonal grids is used in here. The model is applied into the new chamber shape with raised pips. In this chamber system four-hole nozzle is used, and the sprays injected from the each hole impact on lands raised from the chamber wall surface. After impacting, the sprays break up into much smaller drops and distribute over all the chamber space, instead of distributing just near the wall surface in conventional omega-shape. The results showed the potential of the w-shaped chamber employing pips for dispersing droplets so as tn avoid the fuel deposit regions.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.5
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• pp.678-685
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• 2011

An Ejector enhances system efficiency, are easily operated, have a mechanically simple structure, and do not require a power supply. Because of these advantages, the ejector has been applied to a variety of industrial fields such as refrigerators, power plants and oil plants. In this work, an ejector was used to safely recycle anode tail gas in a 75-kW Molten Carbonate Fuel Cell (MCFC) system at KEPCO Research Institute. In this system, the ejector is placed at mixing point between the anode tail gas and the cathode tail gas or the fresh air. Commercial ejectors are not designed for the actual operating conditions for our fuel cell system. A new ejector was therefore designed for use beyond conventional operating limits. In the first place, a few sample ejectors were manufacured and the entrainment ratio was measured at a dummy stack. Through this experiment, the optimum ejector was chosen. The 75-kW MCFC system equipped with this optimum ejector was operated successfully.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1193-1201
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• 2004

The effect of equivalence ratio and fuel/air mixing quality on the phase-resolved gas temperatures at different phases of the oscillating pressure cycle was experimentally investigated. An atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on methane with heat release rate of 1.59kW was used. Temperature measurements were made using coherent anti-Stokes Raman spectroscopy (CARS) at several spatial locations fur typical unstable combustion conditions. Analysis was conducted using parameters such as phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs). Also the probability on the occurrence of high temperature (over 1900K) was investigated to get the information on the perturbation of equivalence ratio and NOx emission characteristics. It was shown that most of temperature histograms exhibit Gaussian profile which has short breadth of temperature fluctuation at equivalence ratio of 0.6, while beta profile was predominant for the cases of other equivalence ratios (${\Phi}$=0.55, 0.50). It was also shown that phase-resolved averaged temperature oscillated in phase with pressure cycle, while normalized standard deviations which represent temporal turbulent intensity of temperature showed nearly constant value around 0.1. The characteristics on the occurrence of high temperature also displayed periodic wave form which was very similar to the pressure signal. And the amplitude of this profile went larger as the fuel/air mixing quality became poorer. These also provided additional information on the perturbation of equivalence ratio at flame as well as NOx emission characteristics.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.103-108
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• 2003

The effect of equivalence ratio and fuel/air mixing quality on the phase-resolved gas temperatures at different phases of the oscillating pressure cycle was experimentally investigated. An atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on methane with heat release rate of 1.59kW was used. Temperature measurements were made using coherent anti-Stokes Raman spectroscopy (CARS) at several spatial locations for typical unstable combustion conditions. Analysis was conducted using parameters such as phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs). Also the probability on the occurrence of high temperature (over 1900K) was investigated to get the information on the perturbation of equivalence ratio and NOx emission characteristics. It was shown that most of temperature histograms exhibit Gaussian profile which has short breadth of temperature fluctuation at equivalence ratio of 0.6, while beta profile was predominant for the cases of other equivalence ratios (${\Phi}$=0.55, 0.50). The characteristics on the occurrence of high temperature also displayed periodic wave form which is very similar to the pressure signal. And the amplitude of this profile goes larger as the fuel/air mixing quality become poorer. These also provided additional information on the perturbation of equivalence ratio at flame as well as NOx emission characteristics.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.799-805
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• 2014

Recently, the regulations of the Local and Global for a variety of air pollution prevention has been enhanced by the steep rise in fuel oil prices. So, the appearance of Gas Fuelled Ships became necessary. In this study, we configured a regasification system which uses Eglycol water as a heating medium to evaporate before being supply fuel to the DF engine, then we analysed the system properties according to the Eglycol water mixing ratio. The results were as follows. When pressure, temperature, and flux of natural gas(NG) which are supplied to DF engines are uniformly kept, the higher mixing ratio of Eglycol is, the lower mixing specific heat of Eglycol water. And the cycle flux and electric power were 1.65 and 1.54 times more required. respectively, than water was used as the heating medium. Basic variables including mass flux according to the mixing ratio of Eglycol water, required electric power of operating fluid pumps, the temperature of natural gas which is supplied to the engine, and the heat exchanger's capacity were drawn from the gotten results.

• Clean Technology
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• v.24 no.4
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• pp.323-331
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• 2018

The results of an experimental investigation on the co-firing characteristics and slagging behavior of dried and hydrothermal carbonization sewage sludge, sub-bituminous coal, and wood pellet in a fluidized bed were presented. Combustion tests were conducted in a lab-scale bubbling fluidized bed system at the uniform fuel-air equivalence ratio, air flow rate, and initial bed temperature to measure bed temperature distribution and combustion gas composition. 4 different fuel blending cases were prepared by mixing sewage sludge fuels with coal and wood pellet with the ratio of 50 : 50 by the heating value. $NO_x$ was mostly NO than $NO_2$ and measured in the range of 400 to 600 ppm in all cases. $SO_2$ was considered to be affected mostly by the sulfur content of the sewage sludge fuels. The cases of hydrothermal carbonization sewage sludge mixture showed slightly less $SO_2$ emission but higher fuel-N conversion than the dried sewage sludge mixing cases. The result of fly ash composition analysis implied that the sewage sludge fuels would increase the possibility of slagging/fouling considering the contents of alkali species, such as Na, K, P. Between the two different sewage sludge fuels, dried sewage sludge fuel was expected to have the more severe impact on slagging/fouling behavior than hydrothermal carbonization sewage sludge fuel.