• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.751-757
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• 2003

With increasing requirements for the less harmful exhaust emissions and the better fuel economy, the conventional injectors in gasoline engines can be replaced by the air shrouded injector in order to provide improved combustion in engine operations. To find out the optimal shape of air shrouded atomizer attached to the conventional injector nozzle, the critical design parameters such as droplet size, fuel and air inlet angles, and injection angles were investigated based on experimental analyses. To explain the characteristics of fuel atomization, these experimental approaches were carried out using a Phase Doppler Particle Analyzer (PDPA) system. The droplet sizes of injected air fuel mixture were obtained by using the beam diffraction phenomenon. In order to improve the atomization effect, the various atomizers were investigated. The Saute. Mean Diameter (SMD) measured at the predetermined locations outside the atomizer represented the performance of fuel atomization. The experimental results show that the design factors and atomization mechanism needed for developing air shrouded injectors. The suggested design parameters in this paper can be a useful reference in the early design stage.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.215-221
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• 2003

A series of experiments were conducted to study the effectiveness of the extinction of a liquid pool fire with two different water atomizing nozzles. Fire source is small-scale circular stainless steel pan of 120mm in diameter with the fuels of hexane and ethanol. K-type thermocouples were used to measure the flame and fuel temperature along the pool centerline and under fuel surface. A digital camera was used to visualize the process of the fire suppression. The experimental results show that water mist droplet size is $115{\sim}180{\mu}m$ with nozzle A and $130{\sim}190{\mu}m$ with nozzle B. The extinguishing time of pool fire was reduced with the increase of pressure. When water droplets are small, they do not reach the flame base since they may be deflected or evaporated by the fire plume. However, influence of flow rate is more important than droplet size on fire extinction. Among the fire extinction mechanisms, drop of flame temperature is superior to suffocation of O2 concentration.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.86-100
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• 1998

The impingement of the fuel spray on the wall within the combustion chamber in compact high-pressure injection engines and on the intake port wall in port-fuel-inje- ction type engines is unavoidable. It is important to understand the characteristics of impinging spray because it influences on the rate of fuel evaporation and droplet distrib- ution etc. In this study, the numerical study for the characteristics of spray/wall interaction is performed to test the applicability and reliability of spray/wall impingement models. The impingement models used are stick model, reflect model, jet model and Watkins and Park's model. The head of wall-jet eminating radilly outward from the spray impingement site contains a vortex. Small droplets are deflected away from the wall by the stagnation flow field and the gas wall-jet flow. While the larger droplets with correspondingly higher momentum are impinged on the wall surface and them are moved along the wall and are rolled up by wall-jet vortex. Using the Watkins and Park's model the predicted results show the most reasonable trend. The rate of increase of spread and the height of the developing wall-spray is predicted to decrease with increased ambient pressure(gas density).

• 한국자동차공학회논문집
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• 제19권3호
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• pp.83-89
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• 2011

Diesel engines can produce higher fuel efficiency and lower $CO_2$ emission, they are subject to ever more stringent emission regulation. However, there are two major emission concerns fo diesel engines like such as particulate matter (PM) and nitrogen oxides (NOx). Moreover, it is not easy to satisfy the regulations on the emission of NOx and PM, which are getting more strengthened. One of the solutions is to apply the new combustion concept using multistage injection such as HCCI and PCCI. The other solution is to apply after-treatment systems. For example, lean NOx trap catalyst, Urea-SCR and others have various advantages and disadvantages Especially, Urea-SCR system have advantages such as a high conversion efficiency and a wide operation conditions. Hence the key factor to implementation of Urea-SCR technology, good mixing of urea(Ammonia) and gas, reducing Ammonia slip. Urea mixer components are required to facilitate evaporation and mixing because the liquid state of urea poses significant barriers for evaporation, and the distance to mixer is the most critical that affect mixer performance. In this study, to find out the distance from injector to mixer and simulation factor, a laser diagnostics and high speed camera are used to analyze urea injector spray characteristics and to present a distribution of urea solution in transparent manifold In addition, Droplet Uniformity Index is calculated from the acquired images by using image processing method to clarify the distribution of spray.

• 한국화재소방학회논문지
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• 제33권5호
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• pp.13-18
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• 2019

본 연구에서는 한국형발사체와 유사한 작동환경에서 Jet A1 액체연료의 매연 입자특성에 대해 농도를 측정함으로써 그 결과를 고찰하였다. 발사체환경과 유사한 대기 조건을 모사하기 위해 연소챔버의 산소 농도를 30%로 유지하고 내부 압력을 0.06 MPa에서 0.1 MPa 까지 변화시켜가며 실험을 통해 수행하였고, 대기의 조성을 질소, 헬륨, 이산화탄소 가스로 치환하여 실험을 수행하였다. 직경이 2 mm인 Jet-A1 액적에 동일한 점화에너지를 인가하여 발생 되는 매연 입자의 농도를 전역 광소멸 기법을 이용하여 측정하였다. Jet-A1 액적 화염의 매연 입자입자의 농도는 모든 압력조건에서 대기의 조성이 질소로 치환된 경우 높았으며, 이산화탄소로 치환된 경우 가장 낮았다. 압력이 낮아질수록 매연의 입자농도가 감소하였고, 대기압력의 Pⁿ 형태로 감소하는 경향을 확인하였다.

• 한국추진공학회지
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• 제6권2호
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• pp.37-44
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• 2002

액체로켓엔진에 사용되는 2-유체 동축형 분사기의 분무 연소 특성을 수치적으로 해석하였다. 가스 역학적 상호작용에 의한 미립화 및 그에 따른 물리 현상들에 대해 유동에 대한 보존방정식과 이론식들을 적용, 수치화하여 액체 제트의 상태, 제트의 속도, 제트의 붕괴길이, 액적의 크기등을 예측 하였으며, 액체제트 분사공 크기에 따른 미립화의 변화를 고찰하였다. 모델 검증을 위하여 액체 제트의 접촉길이와 액적의 크기를 기존의 실험결과와 비교하였으며, 그 결과 정성적으로 일치함을 나타내었다. 액체 제트의 접촉길이는 분사공의 직경이 증가할수록 짧아지고 액적의 크기도 분사공의 직경이 증가할수록 작아진다. 액체 제트는 박리율 증가에 따른 분무화에 의하여 단면적이 감소되며, 그에 따른 질량유속의 보존과 가스로부터의 운동량 화산에 따라 미립화가 활발해지는 영역으로부터 그 속도가 급속히 증가된다.

• 한국재료학회지
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• 제12권10호
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• pp.784-790
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• 2002

For mass product of nanocrystalline ZnO ultrafine powders, self-sustaining combustion process(SCP) and ultrasonic spray combustion method(USCM) were applied at the same time. Ultrasonic spray gun was attached on top of the vertical type furnace. The droplet was sprayed into reaction zone of the furnace to form SCP which produces spherical shape with soft agglomerate crystalline ZnO particles. To characterize formed particles, fuel and oxidizing agent for SCP were used glycine and zinc nitrate or zinc hydroxide. Respectively, with changing combustion temperature and mixture ratio of oxidizing agent and fuel, the best ultrasonic spray conditions were obtained. To observe ultrasonic spray effect, two types of powder synthesis processes were compared. One was directly sprayed into furnace from the precursor solution (Type A), the other directly was heated on the hot plate without using spray gun (Type B). Powder obtained by type A was porous sponge shape with heavy agglomeration, but powder obtained using type B was finer primary particle size, spherical shape with weak agglomeration and bigger value of specific surface area. 9/ This can be due to much lower reaction temperature of type B at ignition time than type A. Synthesized nanocrystalline ZnO powders at the best ultrasonic spray conditions have primary particle size in range 20~30nm and specific surface area is about 20m$^2$/g.

• 한국분무공학회지
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• 제3권2호
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• pp.42-50
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• 1998

The effect of swirl flows un the fuel spray characteristics were investigated for various swillers in a model combustor. The interaction between the flow field and fuel spray in the main combustion tone made by frontal devices including fuel injection nozzles and swirlers. which were characterized by flow velocities, fuel droplet sizes and their distributions which were measured by APV(Adaptive Phase/Doppler Velocimetry) under atmospheric condition at 320cc/min kerosine fuel flow and 0.04kg/sec air supply. A dual swirler with circumferential two-stage swirl vanes of $40^{\circ}\;and\;45^{\circ}$ vanes in different directions and two single-stage swillers of $40^{\circ}$ vanes with 12 and 16 vanes were tested. It was found that the dual swirler has the largest recirculating zone with highest reverse flow velocity. The strongest swirl flow was found at the boundary of recirculation zone. Small fuel droplets were observed in the main axial stream and inside the recirculation zone when swirling flow field were generated by the frontal devices. These findings could give the tips on the optimal design of frontal devices to realize low emissions in gas turbine combustion.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.182-189
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• 2005

In order to investigate the effect of premixed gasoline, diesel fuel, and n-heptane charges on the combustion and exhaust emission characteristics in a direct injection (DI) diesel engine, the experimental studies are performed. The premixed fuels are injected into the premixing chamber that installed upstream of the intake port in order to minimize the inhomogeneity effect of premixed charge. The injection nozzle for directly injected fuel is equipped in the center of the combustion chamber. The air temperature control system is equipped in the intake manifold to examine the effect of air temperature. The experimental results of this study show premixing fuel is effective method to reduce the NOx and soot emissions of diesel engine. NOx emissions are linearly decreased with increasing premixed ratio for the three kinds of premixed fuels. The heating of intake air $(80^{\circ}C)$ reduced the deterioration of BSFC in high premixed ratio, because it promotes evaporation of premixed diesel droplet in the premixing chamber.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.149-152
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• 2008

초소형 터보제트엔진에 적용되는 슬링거연소기를 개발하고 리그시험을 수행하였다. 슬링거연소기에 적용하기 위하여 고속으로 회전하는 회전연료노즐을 설계, 제작하고 분무시험을 통해 연소에 적합한 액적크기와 분포를 얻었다. CFD를 이용해 연소기 내부 유동장을 해석하였으며, 연소리그시험을 통해 설계점에서 11.2%의 압력손실, 99.8%의 연소효율을 달성하였다.