• 한국자동차공학회논문집
• /
• 제9권1호
• /
• pp.57-62
• /
• 2001

EFI system has severe problems of heavy HC emission generated by large fuel droplets and non-uniform air-fuel mixture. Therefore, various atomization techniques are being developed in order to reduce HC emission. The one among those techniques is ar shrouded injector, which has better atomization ability and demands less power loss than other atomizers. Thus, the development of this air shrouded injector can be major topic to cope with international emission regulation. Nevertheless, there are few domestic and foreign studies which deal with air shrouded injector. In this study, the spray characteristics and atomization mechanism of the representative air shrouded injector were analyzed using PDPA system. From experimental results, the definite standards of air shrouded injector's spray characteristics were established.

• 한국분무공학회지
• /
• 제3권4호
• /
• pp.16-24
• /
• 1998

The fuel injection type, in the gasoline engines of atomization of fuel droplet and its distribution hae influenced directly on the decision of engine performance and harmful emission. In this paper, atomization characteristics of fuel spray is investigated with microscopic visualization system. Particle motion analysis system is used to measure the SMD from fuel spray of air-assisted injector by initial factors such as temperature of ambient air and air-assisted pressure. As air-assist pressure and ambientair temperature increase, the SMD is decreased, and its variation is more stable.

• 한국추진공학회지
• /
• 제21권5호
• /
• pp.88-96
• /
• 2017

재생냉각 기술을 적용한 스크램제트 엔진 개발의 일환으로 스크램제트 엔진에 사용될 공기 보조형 인젝터(Air-assist type injector)에 대한 연구를 수행하였다. 실험에 사용된 인젝터는 주 유동에 대해 $90^{\circ}$와 $60^{\circ}$의 각도로 분출되는 두 종류의 인젝터를 사용하였으며 측정 방법에는 미 산란(Mie-scattering)을 이용한 가시화 측정방법과 PDPA를 이용한 미립화 측정 방법을 사용하였다. 실험 결과, 공급되는 기체의 압력 증가와 노즐로부터의 거리가 증가할수록 더 좋은 미립화 특성을 보였으며 분출각도가 $60^{\circ}$인 인젝터가 $90^{\circ}$의 인젝터보다 더 좋은 미립화 특성을 보였다.

• 한국자동차공학회논문집
• /
• 제6권3호
• /
• pp.187-197
• /
• 1998

To investigate the spray behavior and atomization characteristics using an air-assist injector, spray visualization and PDPA measurements were carried out under the various assisted air pressures and the fixed fuel pressure. The air assist pintle type injector employed in this study is consisted of the air assist adaptor and an injector housing using the gasoline fuel and air as the working fluids. As results, increasing pressure of assisted air, the growth of spray tip penetration is gradually reduced at the end of spray and spray angle is steadily increased at the main spray region except from the early spray. For the air assist pressure of 25㎪ in a spray downstream, it is doncluded that droplet size distribution shows the peak of 10${\mu}{\textrm}{m}$ and most of the droplet sizes are less than 50${\mu}{\textrm}{m}$. Also, the air-assist injector extremely improves fuel atomization in order to produce much finer droplets, it shows that approximately, in this case, 50% decreade of SMD than without air assit.

• 한국산학기술학회논문지
• /
• 제18권6호
• /
• pp.1-7
• /
• 2017

분무식 노즐(spray nozzle)은 액체의 표면을 증가시키기 위해 에너지를 공급하여 액체를 다수의 액적으로 미립화시키는 장치로 연소과정에서의 연료의 미립화 또는 표면이나 입자의 코팅 등 여러 산업분야에 다양한 목적으로 응용된다. 초음파 미립화 노즐은 진동 발생장치로부터 고진동수의 전기에너지를 받아 같은 진동수의 기계적 에너지로 변환시키는 변환기를 갖고 있다. 변환된 에너지를 액체에 부가하여 고주파 진동에 의해 미세한 액적을 생성하여 분사한다. 코팅작업에서 가압되지 않은 저속의 분무는 액적이 튕겨나가지 않고 표면에 달라붙어 과도하게 분사되는 양을 줄일 수 있다. 초음파 미립화 노즐은 초음파 진동부 외벽에 공기를 공급해 줄 수 있는 공간을 통해 생성된 보조 공기흐름을 이용하여 저속의 액적을 운반하여 분무특성이나 분무형상을 조절할 수 있다. 따라서 주위 공기의 흐름을 이용하여 원하는 분무특성을 얻을 수 있다. 본 연구에서는 액적의 분사 운동을 모사하기 위해 라그랑지안 분산상 모델(DPM)을 적용한 상용코드 FLUENT를 사용하여 액적 주위의 공기흐름을 동반하는 초음파 미립화 노즐을 해석하였다. 노즐 수축부 형상, 액적의 크기 그리고 공기 측 압력차의 크기를 변화시키며 수치해석을 수행하여 코팅용 분무를 위한 최적 조건을 연구하였다.

• 한국분무공학회지
• /
• 제20권2호
• /
• pp.82-87
• /
• 2015

A nozzle with vortex generator was used to develop the low pressure nozzle with high atomization performance and the nozzle atomized the liquid by centrifugal shear forces. In order to analyze the atomization characteristics, a shadowgraphy method was used and the measurement of droplet size was performed by using laser diffraction analyzer. The liquid injection pressure was fixed as 0.03 bar which is very low pressure and the gas injection pressures were changed from 0 bar to 2.0 bar. As a result, the breakup was achieved at the air injection pressure of 0.25 bar and over. The nozzle with the orifice diameter of 0.4 mm and the orifice gap of 0.25 mm presented small droplet diameters under 50 at the air injection pressure of 0.75 bar.

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

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

• 대한기계학회논문집B
• /
• 제23권1호
• /
• pp.92-103
• /
• 1999

The fuel spray behavior in the intake port of an electronic control port irijection gasoline engine has a strong influence on engine performance, exhaust emission and fuel consumption. Thus, in this study, fuel spray behavior and flow characteristics of the air assist gasoline spray injected into a suction flow in a simulated rectangular intake port have boon investigated. Macro-behavior of spray characteristics was investigated by means of visualization and the measurements of SMD and velocity were made by PDPA. For analysis the flow field with droplets size, droplets are classified five droplets size groups. As a result, the normal distance of suction flow increasing, the relatively large droplets distribution and SMD increase because small droplets easily follow suction flow. Near impinging wail, after impinging against the wall, secondary atomized small droplets of D < $30{\mu}m$ bound from the wall. And the increasement of suction flow progress to the large droplets of D > $100{\mu}m$ distribution. Therefore, SMD are apparently increased near impinging wall, Z/d = 9.0.

• 한국분무공학회지
• /
• 제3권4호
• /
• pp.58-64
• /
• 1998

In the gasoline engine of fuel injection type, atomization of fuel droplet and its distribution has directly influenced the performance of engine and harmful emission. To investigate atomization characteristics of fuel spray, in this paper fuel spray of air-assisted injector is observed at the various initial conditions of ambient air temperature and air assisted pressure. Behavior of fuel spray is photographed with microscopic visualization system. The SMD of fuel droplet is measured with PMAS (Particle Motion Analysis System). The effect of air-assisted pressure and temperature of ambient air resulted in the decrement of SMD and its variation. Finally, It was found that It was found that from spray angle at the two-hole injector had measured $20{\pm}4$ degree the result of photographs by shadow graphy. The mean diameter of suns decreased and the of droplets increased with increasing the temperature in the spray fields by the results of PMAS measurement. It was found that the characteristics of sprays became finer by increasing the temperature of spray fields about 373K without the delivery of air-assistance.