• 한국자동차공학회논문집
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• 제8권6호
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• pp.22-30
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• 2000

The present article deals with comparisons of published liquid breakup models for diesel sprays to analyze the influence of breakup models on various spray parameters. The three different models tested in this study are the surface wave instability (Wave) model, the Taylor analogy breakup (TAB) model, and the drop drag model(DDM). The numerical results using these models are compared with several experimental data to assess the prediction capabilities of breakup models. Additional task in this study is to investigate effects of the breakup time constant in the Wave model on the spray parameters because the spray behavior is sensitive to the breakup time constant. It is seen that there is uncertainly about the breakup time constant indicating that the suitable acceptance of the constant is important, and the TAB model generally shows significant under-prediction of Sauter Mean Diameter(SMD). In addition, it may be indicated that differences between the DDM and Wave model are not significant, showing that the DDM may be suitable for air-assisted atomization rather than pressure atomization.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.52-58
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• 1998

The spray characteristics of air-assisted fuel injection and its effects on the engine combustion was investigated in this study. The atomization characteristics of a Bosch fuel injector inserted into the air-assist adapter were measured using particle motion analysis system. Droplet size decreased with air supplied and fine spray with below $60\mu\textrm{m}$ of SMD was acquired under the conditions of air-assist pressure over 0.5bar. The lean combustion performance of a 1.8L DOHC engine equipped with air-assist adapters was tested on the dynamometer. When the assistant air pressure is 1.0bar, lean limit recorded the highest value, and CO, HC emissions were decreased at the pressure over 1.0bar.

• 한국가시화정보학회지
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• 제12권2호
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• pp.9-12
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• 2014

Conventional electrospray and air spray methods have the vulnerabilities of limited flow rate (throughput) and droplet size, respectively. Since high throughput with uniform size of droplet is required for various applications, an improved technique should be adopted. Here, we report a combined system of an air pressure and an electric field and evaluate the atomization performance of it. The air flow allowed applying high flow rate range and the electric field reinforced the atomization process to generate fine droplets. A correlation between two forces was investigated by comparing the droplet produced by each method. The atomized droplets were measured and visualized by image processing and a particle image velocimetry (PIV). The quantitative results were achieved from the parametric space and the effect of both forces was analyzed. The motion of charged droplets followed the outer electric field rather than the complex vortex in the shear layer so that the droplets accelerated directly toward the grounded collector.

• 한국분무공학회지
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• 제2권2호
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• pp.35-42
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• 1997

An innovating technique of atomizer has been proposed to supply and to atomise molten materials. Both of a simple geometry of nozzle and an improved nozzle have been fabricated in the present study. With these nozzles, characteristics of the suction and disintegration have been empirically investigated. The important conclusions are as follows; In the case of a simple nozzle: 1) Although the sucking up and supplying of molten materials are available, the applications of powder metallurgy are limited. 2) It is concluded that the more air flow rate, $W_A$ or the shorter the height of air nozzle from the surface of supplied water, $L_h$, the more the atomizing mass of liquids, $W_L$. In the case of an improved nozzle: 3) The stable liquids can be supplied due to cut off the passage of surrounding air entrainment by air jets. 4) The atomizing mass of liquids, $W_L$ has affected not so much on the height of nozzle from the surface of supplied water, $L_h$ as that from the orifice, hc.

• 한국분무공학회지
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• 제1권1호
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• pp.55-62
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• 1996

In a fuel injection engine, atomization of liquid fuel and mixture formation process has influenced(or affected) directly on the engine performance and pollutant emission. In this study, the characteristics of fuel spray and the behaviors of secondary atomization developed at the downstream of the valves were investigated using an image processing method. Solid and perforated valves are chosen in order to evaluate the valve performance in terns of air flow rate, valve opening angle and valve shape. Experimental results clearly indicate that the spray atomization quality can be improved by increasing the perforated rat io and the blockage rat io in the perforated valve, the characteristics of spray atomization is improved by using the perforated valve with high perforated rat io and blockage ratio.

• 대한기계학회논문집
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• 제14권5호
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• pp.1211-1221
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• 1990

본 연구에서는 CWM을 이류체 미립화기(twin-fluid atomizer)로 미립화 시켜 미립화에 크게 영향을 미치는 인자들로 믿어지는 공기분사압력, 부하도(loading), 미 분탄의 크기 그리고 CWM 방울 채집위치의 변화가 CWM 방울크기 분포와 CWM 방울안 미 분탄 존재유무에 미치는 영향을 연구의 목적으로 하였다.

• 디지털융복합연구
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• 제10권5호
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• pp.283-288
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• 2012

본 연구는 이유체 분무장치 미립화 장치 분무특성을 연구하기 위해 수행되었다. 실험 조건은 상온에서 분사압력을 5 bar에서 10 bar 까지 1 bar 간격과 송풍기로부터 공기유량은 0.5, 1.0, 2.0 mmH2O(X10-2)로 증가하였으며, 사용된 액체는 경유이다. 분무특성을 연구하기위해 SMD를 측정하였다. 이 실험으로 부터 다음과 같은 결과를 얻었다. 1. 분무 압력이 증가할수록 SMD는 점점 감소한다. 2. 압력노즐로부터 측정 거리가 증가할수록 SMD도 증가한다. 3. 송풍공기가 더해지면서 분무되는 경우의 SMD는 상대적으로 감소한 것으로 볼 수 있다. 이 연구의 결과로 알 수 있듯이, 송풍공기가 더해지는 분사 장치는 유용한 SMD의 변화를 볼 수 있다. 이는 이유체 분무장치 미립화 장치 분무특성 설계와 성능평가를 위한 중요한 지표로 사용될 수 있을 것으로 판단된다.

• 한국연소학회지
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• 제7권1호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.303-306
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• 2002

Liquid atomization by means of a spinning cup is widely used as a device for combustion, in cooling and spray drying. In this study, the blowing type rotary atomizer was experimental carried out the investigations on the characteristics of the blowing type rotary atomizer which is an air flow energy of blower instead of an electric motor most commonly used to a driven energy. The analysis on the rotary cup speed, air velocity with the blower conditions was performed and also the drop size was measured using LDPA. It was tried to analyzed on air-nozzle size and liquid flowrate as the result. It was found that the increase of the relative velocity between liquid and air improve significantly atomization liquid, and decrease of the liquid flowrate improved the maximum drop size though the mean drop size is really the same.

• 한국분무공학회지
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• 제9권3호
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• pp.35-41
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• 2004

The spray characteristics were investigated to study the effect of shroud air with swirl flow on simplex type fuel injector for gas turbine combustor. The spray tests using PDA(Phase Doppler Anemometry) technique were conducted to compare the performance of simplex atomizer with $0^{\circ},\;40^{\circ},\;50^{\circ}$ swirled-shroud air conditions. In this study. we found that the injector with strong swirled-shroud air has the better atomization Performance compared with weaker swirled and non-swirled conditions.