• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.8
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• pp.1132-1140
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• 1998

The disintegration process of initial spray from high-pressure swirl injector was investigated at different injection pressures. The transient breakup phenomena that were difficult to observe at high injection pressure were easily observed at the low injection pressure of 0.4MPa. The effect of fuel remained inside a nozzle hole volume on the penetration of initial spray was also investigated. The disintegration process of initial spray could be classified four regions: the formation of mushroom shape, the first collision, the second collision, and the development of spray, The liquid film of cup shape was particularly found in the second collision region, and the growth ratio of its length and width at low and high injection pressures were compared.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.2
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• pp.42-49
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• 1991

This study is to investigate the dispersion characteristics of diesel fuel spray in the initial stage of the beginning of the injection under the condition of room temperature and atmospheric pressure. It is difficult to analyse that the diesel fuel spray in diesel engine has unsteady intermittent spray. So author installed a fuel accumulator and an electromagnetic controller in order to keep the constant fuel injection rate with the time variation. With this modified fuel injection system, spray tip penetration, spray angle and initial spray development process are investigated by instantaneous photographic method. The results obtained in this study are as follows : 1) The initial shape of injection of diesel fuel spray shows the form of non-disintegrated intact core, but the formation of ligaments increasingly grows as the time increases. It can also be shown that fine droplets become disintegrated out from the ligaments. 2) The slope of spray tip penetration was changed to two different tendencies with time. The transition point of the slope is shown at the time of around between 0.09 msec and 0.4 msec from the beginning of injection. This is transition time from non-disintegrated intact core to formation of ligaments.

• Journal of ILASS-Korea
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• v.15 no.1
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• pp.8-16
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• 2010

This paper present the diesel spray characteristics at different injection system parameters in a HSDI diesel engine. The spray characteristics was calculated by the coupled simulation of fuel injection system model and three-dimensional KIVA-3V code with TAB spray model. The relevant injection parameters are accumulator volume, control chamber initial volume, control orifice diameter, needle valve diameter and nozzle chamber initial volume, etc. Parametric investigation with respect to twelve relevant injection parameters showed that there was a significant advantage in varying control chamber initial volume, control chamber orifice diameter, and nozzle chamber orifice diameter with respect to effect the SMD and fuel injection speed. Consequently, in order to design the fuel injection system for spray characteristics, it seems reasonable to suppose to be optimized the fuel injection system.

• Journal of ILASS-Korea
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• v.11 no.4
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• pp.212-219
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• 2006

The initial film flow development of the high-pressure swirl spray was investigated at different injector operating conditions to analyze film flow development and to provide the input data for the modeling works. This result can be also useful to verify the previously simulated results. The initial flow conditions such as liquid film thickness, flow angle and flow divergence are obtained by visualizing the inside and near the nozzle flow with a microscopic imaging system. The visualized images are quantified using an image processing tool. From the information of liquid film thickness and flow angle, the initial axial and tangential velocity and the swirl number of the swirl spray are successfully determined at various operating conditions. The experimental results showed that the initial liquid film thickness, flow angle and flow divergence are remained constant when the injection pressure is increased. However, initial film conditions are severely changed when the fuel temperature is increased. The swirl number remained constant when the injection pressure is increased while it showed increased value at high fuel temperature condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.9-21
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• 2000

In this study, the characteristics of high-pressure swirl injector have been studied using a commercial CFD code, STAR-CD and experiment to investigate the effect of the length of orifice and swirl port on the spray characteristics. Influences of swirl port angle and initial conditions have also been examined in terms of penetration depth and Sauter`s mean diameter. Computed results of the spray characteristics are compared with experimental results. The results show that the tangential velocity at the nozzle exit decreases, but the axial velocity increases as swirl port angle is increased. Hence, the static flow rate increases, but the initial spray angle decreases with increasing the swirl port angle. It is also shown that the values of the initial SMD used as input data for spray simulation influences the penetration depth and SMD. The spray pattern from the present numerical simulation agrees well with experimental result.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.201-209
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• 1984

In order to examine the effect of initial spray condition on the spray combustion mode and flame characteristics, theoretical analysis was carried out to predict combustion mode and flame structure for various initial distribution of droplets in spray. A system of conservation equations of spray flame in two dimensional axisymmetric for two phase flow was solved by a discrete element method for n-Butylbenzen (C$_{10}$ $H_{14}$). As a results of present study, there are two principal group combustion modes that may occur independently for various initial group combustion numbers in a spray burner. These group combustion modes are termed as an external and internal group combustion mode. The critical group combustion number between the internal and external group combustion mode and the flame characteristics of those flame are also predicted. These results may be used as a basic data in the designing of new combustors as well as proper operating conditions for spray burners.s.

• Journal of Welding and Joining
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• v.7 no.3
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• pp.55-62
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• 1989

Variation of the spray droplet velocity with spraying distance and the microstructural characteristics of spray deposits fromed by oxy-fuel thermal spraying with Ni-base alloy powder contained chrome boride for hard facing were examined. Measurements of spray droplet velocity as a function of distance from the nozzle tip were inexcellent agreement with computer simulated predictions. Optimum condition for thermal spray deposits in this experiment was found to be under #10kg/cm^2$ of acceleration gas pressure with 15cm of spraying distance. Fine microstructure and higher microhardness of the initial part of the deposits due to rapid solidification were found to be able to maintained in a thickness up to 0.4mm, and this initial microstructure and properties could be maintained throughout the thickness of a thick spray deposits by performing the multipass spraying with 0.4mm thickness of each pass.

• International Journal of Automotive Technology
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• v.5 no.3
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• pp.145-153
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• 2004

Potential fuel economy improvements and environmental legislation have renewed interest in Gasoline Direct Injection (GDI) engines. Computational models of fuel injection and mixing processes pre-ignition are being developed for engine optimisation. These highly transient thermofluid models require verification against temporally and spatially resolved data-sets. The authors have previously established the capability of PDA to provide suitable temporally and spatially resolved spray characteristics such as mean droplet size, velocity components and qualitative mass distribution. This paper utilises this data-set to assess the predictive capability of a numerical model for GDI spray prediction. After a brief description of the two-phase model and discretisation sensitivity, the influence of initial spray conditions is discussed. A minimum of 5 initial global spray characteristics are required to model the downstream spray characteristics adequately under isothermal, atmospheric conditions. Verification of predicted transient spray characteristics such as the hollow-cone, cone collapse, head vortex, stratification and penetration are discussed, and further improvements to modelling GDI sprays proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.143-148
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• 2012

This study is an investigation on macroscopic spray behavior of nonimpinging-type injector equipped on the hydrazine thruster under development. An electron microscope is employed for the acceptance examination of injector orifice. Initial performance characteristics and spray behavior of injector are observed through the instantaneous spray images which are captured by high speed camera and Schlieren method with varying injection pressures. The injector performance is scrutinized by the velocity along with penetration length of spray and categorized by dimensionless parameters. It is confirmed that there exist varying characteristics related to the spray breakup caused by fabrication errors of injector-orifices. Unexpected spray behavior, which needs to be reexamined, is grasped at specific pressure level, as well.

• International Journal of Automotive Technology
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• v.6 no.1
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• pp.9-14
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• 2005

An experimental investigation has been carried out to reveal the atomization process of the diesel fuel spray. The spray injected through a single hole nozzle was taken by a camera on the opposite side of a stroboscope for macroscopic observation or a nanolite for microscopic observation. The effect of nozzle aspect ratio was analyzed with disintegration phenomena of the diesel spray. Based on the enlarged spray photograph, atomization process was observed in detail and further the spray cone angle was measured under various ambient pressures. The result shows that atomization of diesel spray in early stage of injection is mainly progressed in the vicinity of spray periphery region except the region close to the nozzle exit and spray head region. The spray cone angle is nearly constant under the pressurized condition, while it decreases with elapsing time under the atmospheric condition.