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

• 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.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.63-74
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• 1999

When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus , this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine dropkets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10m/s ∼30m/s. And fuel pressur ewas fixed to 300kPa, but air assist pressure was varied to 0∼25kPa for a vairable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.159-162
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• 2007

아음속 유동 내에 수직으로 분사된 액체제트의 액적분열 분포 특성을 알아보기 위해 이유체 노즐을 사용하여 실험적으로 연구하였다. 노즐은 L/d=3의 외부혼합형으로 공기와 액체의 비를 0 ${\sim}$ 59.4%까지 변화시키면서 분사하였다. 분무형상의 변화를 이미지화 하였으며 분무의 궤적과 액주의 형상을 관찰하였다. 액체제트 분열의 단면분포 특성을 PDPA를 사용하여 측정하였며 SMD, 액적속도, 그리고 체적유속을 측정하였다. 그 결과 노즐로 공급되는 공기의 양이 많아질수록 Y/d방향의 관통거리는 증가하였고 액적의 미립화는 가속화되는 것을 관찰할 수 있었다.

• Journal of Mechanical Science and Technology
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• 제14권12호
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• pp.1376-1385
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• 2000

This study investigates spray characteristics before and after wall impingingment of gasoline spray in suction air flow. For this study, a rectangular model intake port was made of acrylic glass, and suction air was generated by using the forced air blower contrariwise. The injector for this study was a pintle-type port gasoline injector in which an air-assist adaptor is installed to supply assisted air. A PDPA system was employed to simultaneously measure the size and velocity of droplets near the wall. Measured droplets are divided into "pre-impinging droplets"with positive normal velocity and "post-impinging droplets"were negative normal velocity for the suction flow. The velocities, size distributions and Sauter mean diameter(SMD) of pre-and post-impinging droplets for varions injection angles and air-assists are comparatively analyzed.

• 대한의용생체공학회:의공학회지
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• 제35권5호
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• pp.119-124
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• 2014

A Ventricular assist device (VAD) is one of the most efficient treatments to raise the survivability of the end stage heart failure patient. However, some of LVAD patients have died for the failures and improper control of LVAD. To detect critical dangers in LVAD, the monitoring methods of LVAD outflow have been requested, because it can be affected by patient's hemodynamic states and abnormal conditions of LVAD. In the case of an external pulsatile LVAD, the air movement through the air line can be used to estimate LVAD outflow. In this study, the air movement in the air-line of the extracorporeal pulsatile LVAD was measured with a differential pressure sensor between different points. The precise estimation of air movement could be achieved by additional measurement of air pressure. In a series of in-vitro experiments, the LVAD outflow were changed according to the afterload of LVAD and the differential pressure of LVAD didn't have close correlation with the LVAD outflow that were measured with an ultrasonic flowmeter at the same time. However, new precise estimation with the data from differential pressure and one point pressure in the air-line showed higher correlations with LVAD outflow.

• 한국분무공학회지
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• 제1권4호
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• pp.32-39
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• 1996

Fuel spray in the MPI gasoline injector and its atomization characteristics are investigated with both macroscopic and microscopic visualization systems. The Bosch injector is inserted into an air-assist spray adapter which is designed to be fabricated and assembled easily. particle motion analysis system is used to measure the SMD of injector, where the assistant air pressure is varied from 0.0 to 1.5bar with fuel pressure 2.8bar. Droplet size decreased with higher air pressure and fine fuel spray with below $60{\mu}m$ of SMD is acquired at the assistant air pressure over 0.5bar.

• 한국추진공학회지
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• 제21권5호
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• pp.88-96
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• 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.434-440
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• 2000

The atomization characteristics of air-assist atomizer which is surrounded by a coflowing airstream is investigated. The air-assist, coflow air stream had swirl imparted to them in the same direction with 45 degree's angle swillers. The fuel and air entered the combustor at ambient temperature and the combustor was operated in an unconfined environment. Diesel fuel was used for all the experiments. Drop size and mean velocity are reported for certain distances downstream from the nozzle. The droplet size and velocity measurements were performed using a two-component phase/Doppler particle analyzer and velocity profiles across the entire flowfield are presented.

• 대한기계학회논문집B
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• 제20권6호
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• pp.1948-1958
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• 1996

Experimental and theoretical studies on the air-assist coaxial atomizer have been continuously carried out for a long time. But now the importance of the theoretical study is tending to increase as with the development of computer. This study is concerned to the spray modelization, especially, the instability of the liquid jet surrounded by the air stream which flows with high velocity. To study the phenomena of the break up, we used the linear theory based on the classical Kelvin-Helmholtz theory for capillary wave at a simple interface and we investigated the variation of liquid core radius. As a result, we obtained that the drop diameter and the variation of the liquid core radius predicted by using our model are reasonable.