• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1123-1130
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• 2004

Numerical simulations have been carried out to investigate the effect of nozzle hole geometry on the combustion characteristics of the large diesel engine. 6S90MC-C. Spray and combustion phenomena were examined numerically using FIRE code. Wane breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation processes. Predictions on the cylinder peak pressure and NOx emission were first verified with the experimental data to confirm the reliability of numerical calculations. The comparison results showed good agreements within the range of 0.64% and 4.6% respectively. Finally, the effects of fuel spray angle and diameter on the engine performance were investigated numerically to find the optimum nozzle hole geometry considering fuel consumption, NOx emission and heat flux of the combustion chamber wall. It was concluded that the combustion gas recirculation in cylinder by changing fuel injection direction is an effective method to reduce NOx emission by about 10% with increasing fuel oil consumption, 1.4% in a large diesel engine.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.447-452
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• 2000

The low-emission and high-performance diesel combustion is an important issue in the combustion research community. In order to understand the detailed diesel flame field involving the complex Physical Processes, It Is quite desirable to study diesel spray dynamics, auto-ignition and spray flame propagation. Dynamics of fuel spray is a crucial element for air-fuel mixture formation flame stabilization and pollutant formation. In the present study, the diesel RCM (Rapid Compression Machine) and the Electric Control injection system have been designed and developed to investigate the effects of injection Pressure, injection timing, and intake air temperature on spray dynamics and diesel combustion processes. In terms of the macroscopic spray combustion characteristics it is observed that the fuel jet atomization and the droplet breakup processes become much faster by increasing the injection pressure and the spray angle. With increasing the cylinder pressure there is a tendency that the shape of spray pattern in the downstream region tends to be spherical due to the increase of air density and the corresponding drag force. Effects of intake temperature and injection pressure on auto-ignition is experimently analysed and discussed in detail.

• Journal of ILASS-Korea
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• v.9 no.2
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• pp.9-17
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• 2004

The performance characteristics of lean burn system in gasoline engine are mainly affected by the air-fuel mixture in cylinder, gas exchange process of manifold system, exhaust emission of engine, and the electronic engine control system. In order to obtain the effect of performance factors on the optimum conditions of lean burn engine, this study deal with the behavior of mixture formation, gas flow characteristics of air, flow and evaporation analysis of spray droplet in cylinder, vaporization and burning characteristics of lean mixture in the engine, and the control performance of electronic engine control system. The optimum flow conditions were investigated with the swirl and tumble flows in the combustion chamber with swirl control valve. The performance characteristics and optimum condition of flow field in intake system were analyzed by the investigation of inlet flow of air and combustion stabilization on cylinder.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.206-209
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• 2010

The visualization device for hybrid rocket is fabricated to investigate the combustion phenomena. Visualization device were composed with ignition system, oxidizer supply system, control system and data acquisition system, combustion visualization system. GOX as oxidizer and HDPE, Paraffin-LDPE Blending, Paraffin sd were used. As results, combustion phenomena and fuel droplet entrainment were observed.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.76-80
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• 2004

Nano-sized ZnO colloids were prepared by use of spray combustion method. for combustion reaction, $Zn(NO_3)_2{\cdot}6H_2O$ and $CH_6N_4O$ were employed as an oxidizer and a fuel. Exothermic peak was shown at $230^{\circ}C$ by DTA/TGA, and it was considered as a combustion reaction followed by ignition of the precursor mixture. In case of spray combustion method, because insufficient contents of molecules and radicals generated from precursor droplets may lead an incomplete igmition, the ignition temperature of combustion chamber was chosen at $500^{\circ}C$. For diminishing aerosol coagulation, the droplet number concentration was reduced by filter media. The fluid was laminar with 2.5 seconds of aerosol residence time. The synthesized colloids had spherical shape with 180 nanometer size, and the crystalline phase was ZnO with hexagonal structure.

• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.13-19
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• 2005

An experimental study is presented for extinguishing characteristics of liquid fuel fire by water mist containing sodium acetate trihydrate. To evaluate the extinguishing performance of water mist containing an additive, the evaporation characteristics of a water droplet on a heated surface was examined. The evaporation process was recorded by a charge-coupled-device camera. Also, small-scale extinguishing tests were conducted for n-heptane pool fire in ventilated space to measure flame temperature variation. The average evaporation rate of a water droplet containing an additive was lower than that of a pure water droplet at a given surface temperature due to the precipitation of salt in the liquid-film and change of surface tension. In case of using an additive, the flame temperature was lower than that of pure water at a given discharge pressure and it was because the momentum of a water droplet containing an additive was increased reducing flame size. And also dissociated metal atoms, sodium, were reacted as a scavenger of the major radical species OH^-,\;H^+$ which were generated for combustion process. Moreover, at a high pressure of 4MPa, the fire was extinguished through blowing effect as well as primary extinguishing mechanisms.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.179-188
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• 2003

The spray characteristics of dual orifice injector were investigated under two different fuels through measurement of SMD, number density and volume flux by using PDPA system. In this experiment, we found out that the droplet size and spray structure are strongly depend on fuel density and viscosity.

• Journal of ILASS-Korea
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• v.5 no.4
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• pp.12-32
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• 2000

The recent trends in numerical simulation of various spray phenomena are reviewed in this article. Major subtopics are atomization/breakup, collision/coalescence, wall collision, interfacial transfer, droplet dispersion, two-phase injection and spray combustion. Each submodel has been under continuous refinement and validation against more extensive data base by advanced laser diagnostic techniques. Most uncertainty in current spray simulations come from these physical submodels, not from excessive computational constraints.

• Journal of Energy Engineering
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• v.10 no.2
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• pp.153-160
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• 2001

본 연구에서는 고온 분위기 온도 및 대기압 하에서 액적의 급속가열과 연소가 가능한 고온 연소로 장치와 고속도 비디오 카메라를 이용하여 다조성 단일 액적 연소에 대해 고찰하였다. 그 결과 저비점 성분을 혼합한 경유의 액적은 기본적으로 입경의 2승 법칙에 의해서 감소되었으며, 그 과정에서 입경이 일시적으로 급속히 감소하는 현상이 보여짐과 더불어 연소기간도 단축되었다. 즉, 저비점 성분을 혼합한 경유의 액적은 미세폭발 현상에 의해 기존 디젤 연료에 비해 더 빨리 증발되고 연소가 되었다. 또한, 순수 파라핀계 및 함산소계 연료의 화염은 전체 연소기간동안 기존 경유의 화염에 비해 푸른색을 띠고 있어, 매연이 없는 연소를 입증해 주었다.

• Journal of the Korean Society of Combustion
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• v.7 no.1
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• pp.44-51
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• 2002

This paper presents an atomization model for sprays under flash boiling conditions. The atomization is represented by the secondary breakup of a bubble/droplet system, and the breakup is considered as the results of two competing mechanisms, aerodynamic force and bubble growth. The model was applied to predict the atomization of a hollow-cone spray from pintle injector under flash boiling conditions. In the regimes this study considered, sprays are atomized by bubble growth, which produces smaller SMD#s than aerodynamic forces alone. With decreasing ambient pressures, the spray thickness, fuel vaporization rate and vapor radial penetration increases, and the drop size decreases. With increasing the fuel and ambient temperatures to some extent, the effect of flash boiling and air entrainment completely change the spray pattern.