• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.589-595
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• 2009

The instability wave formed near nozzle region grows to vortex with large scale in downstream region of spray. It plays an important role in the fuel-air mixing, combustion process and engine exhaust emissions in direct injection diesel engine. The objective of this study is to analyze effect of variant parameters (injection pressure, ambient gas density, etc.) and fuel properties on spray instability near nozzle region. Spray structure near nozzle region was investigated using a magnification photograph. A pulsed Nd-YAG laser was used as a light source, and image was taken by CCD camera. The following conclusions are drawn from this experimental analysis. In low ambient density, the effect of fuel properties on spray instability near nozzle region is dominant. In high ambient density, the effect of ambient gas on spray instability near nozzle region is dominant. High jet velocity has strong influence on spray instability.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.454-459
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• 2000

Diesel engine which has high thermal efficiency is one of the major movers. Recently, as people pay attention to the environmental pollution, the emission of Diesel engine becomes an important problem. So it is needed to understand the characteristics of diesel fuel spray injected into a combustion chamber to reduce the emission. The factors which control the diesel fuel spray are the injection pressure, the nozzle diameter, the impinging angle and the variation of an ambient pressure and temperature. In this paper, the experiments were conducted in the free spray and the impinging spray with various ambient temperatures(273K, 373K, 573K). And the behaviors of the diesel fuel spray, such as penetration, spray angle and axial distance in the free spray and axial distance and spray thickness in the impinging spray were studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1635-1646
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• 1997

The nozzle length to diameter ratio of real diesel nozzles is about 2-8 which is not long enough for a fully developed and stabilized flow. The characteristics of the flow such as turbulence at the nozzle exit which affect the development of the spray can be enhanced by impinging the flow inside nozzle. The flow details inside the impinging nozzles have been investigated both experimentally and numerically. The mean velocities, the fluctuating velocities, and discharge coefficients in the impinging inlet nozzles, round inlet nozzle, and sharp inlet nozzle were obtained at various Reynolds number. The developing feature of the external spray were photographed by still camera and the droplet sizes and velocities were also measured by laser Doppler technique. The spray angle was greater and the droplet sizes near the spray axis were smaller with the impinging flow inside nozzle.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.1-7
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• 2004

This paper describes the characteristics of injection rate and macroscopic behavior of fuel spray injected from common-rail type diesel injectors with different nozzle geometries. The injection rates according to the nozzle geometries were measured at different energizing duration of the injector solenoid and injection pressure by using the Bosch's injection rate meter based on the pressure variation in the tube. The spray behaviors injected from the different nozzles were visualized using the spray visualization system composed of an Ar-ion laser, an ICCD camera, and a synchronization system at various injection and ambient pressures. It is revealed that VCO nozzle has higher spray tip velocity at the early stage of injection duration and wider spray cone angle than the mini-sac nozzles. Also the spray cone angle is increased with the increase of nozzle diameter.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.79-80
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• 2006

In this paper, ultrasonic nozzle and driving circuit were manufactured and their electrical properties were investigated. Uitrasonic nozzle was fabricated using PSN-PMN-PZT ceramics showing excellent piezoelectric characteristics. In order to drive ultrasonic nozzle, PWM controller(KA3525A) was used. With increasing input voltage of nozzle, particle diameters of diesel were increased up tot 16V and then decreased. At the input voltage of 12V, volume particle diameter showed the minimum value of $37.3{\mu}m$ and also at the input voltage of 18V, volume particle diameter showed the maximum value of $51.3{\mu}m$.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.493-500
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• 2006

Investigation on the fuel adhering on a wall was carried out experimentally to clarify the characteristics of impinging diesel sprays. Diesel sprays were injected into a high-pressure chamber of cold state and impinged to a wall having various impingement distances and ambient pressures. Photographs of both the fuel film and the post-impingement spray were taken through a transparent wall. Adhered fuel mass on a wall was measured by means of dividing into two types of fuel state: the fuel film itself; and sparsely adhered fuel droplets. Adhering fuel ratio was predicted and further the distribution of fuel mass for impinging diesel spray was analyzed as a function of time. As result, with an increase of the ambient pressure, both the maximum fuel film diameter and the adhered fuel ratio decreased. Based on some assumptions, the adhering fuel mass increased rapidly until the fuel film diameter approached the maximum value, and then increased comparatively gradually.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.43-50
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• 2002

In the present study, reduction of harmful exhaust gas in a diesel engine using stratified injection system of dual fuel (diesel fuel and methanol) was tried. The nozzle and fuel injection pump of conventional injection system were remodeled to inject dual fuel in order from the same injector. The quantity of each fuel was controlled by micrometers, which were mounted at rack of injection pumps. The injection ratio of dual fuel was certificated by volumetric ratio in injection quantity test. Cylinder pressure and exhaust gas were measured and analyzed under various supply condition of duel fuel. We confirmed that combustion of dual fuel was performed successful1y by using modified injection system in a D.I. diesel. Soot and NOx are simultaneously reduced by stratified injection without large deterioration of thermal efficiency, but THC and CO are relatively increased.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.410-415
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• 2000

A diesel engine is one of the major prime movers to its high thermal efficiency. But due to the recent attention far the environmental pollution, the emissions of diesel engine became to a important problem. So it is needed to understand the characteristics of diesel spray injected into a combustion chamber. The factor which controls the diesel spray are the injection pressure, the nozzle diameter, the impinging angle and the variation of pressure and temperature. In this paper, experiments were conducted far the variation of the environmental temperature(273k, 373k, 573k), free spray and impinging spray. And the notions of penetration, spray angle, axial distance for free spray, and axial distance, spray thickness from impinging wall fur impinging spray.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.28-34
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• 2001

Great attentions are paid to HSDI diesel engine for passenger cars because of its high thermal efficiency. The most interesting research in HSDI diesel engine developments is focused on applying common rail system as a fuel injection equipment. In this study, a series of tests are carried out to investigate the effect of injection pressure variation on the smoke and fuel concluded in a small HSDI diesel engine with common rail system. As a result of this study it is concluded that there is an optimum rail pressure dependent on combustion system such as nozzle type, combustion chamber geometry.

• International Journal of Automotive Technology
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• v.6 no.3
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• pp.215-219
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• 2005

Liquefied petroleum gas (LPG) has been used as motor fuel due to its low emissions and low cost. A liquid direct injection system into a cylinder was suggested as a next generation system to maximize a fuel economy as well as a power. This study addresses the analysis of the LPG spray injecting from single hole injector. Two different test conditions are given, which are a fully developed spray case with various injection pressures and a developing spray case with ambient pressure variation. The LPG spray photographs are compared with the sprays of gasoline and diesel fuel at the same conditions, and the spray angles and penetration lengths are also compared, and then the spray behavior is analyzed. The LPG spray photos show that the dispersion characteristic depends very sensitively on the ambient pressure soon after injection. The spray angle is very wide in a low ambient pressure condition until the saturated pressure, but the angle is quickly reduced at the condition over the pressure. However, the down stream of the LPG spray shows much wider dispersion and less penetration than those of gasoline and diesel sprays regardless ambient pressure condition.