• Journal of computational fluids engineering
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• v.2 no.2
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• pp.80-88
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• 1997

A new wall impaction model for diesel spray is described in this paper. The gas phase is modelled in terms of the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach. The droplet parcel contains many thousands of drops assumed to have the same size, temperature and velocity components. The droplet parcel equations of trajectory, momentum, mass and energy are written in Lagrangian form. The new drop-wall interaction model is proposed, which is based on experimental investigations on individual drops, and it is applied for the general non-orthogonal grid. The model is then assessed through comparison with experiments over a wide range of test conditions of sprays. The results are in good agreement with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1013-1020
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• 2001

This paper addresses to the area where the extended collision model is applied. In order to find the optimum shape of wall sprays, the extended model is applied to the nearest cells of just over the impaction wall, spray core or over all. The droplet distribution, wall spray radii, heights and gas flows are shown in all the cases. Those results show that the best spray shape represents in the case applying the extended model just on the impinging wall.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.54-65
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• 1997

Wall wetting in diesel engines has been considered as a bad phenomenon because of fuel deposition which makes fuel/air mixing and evaporation worse. In order to avoid the problem, many research works have been carried out. One of the studies is on new combustion chamber systems which are using spray impacting on a wall. In this study a new type of chamber system is analysed using wall impaction model introduced and assessed in the coupled paper. The gas phase is modelled in terms of the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction, The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. With various conditions the spray distribution, vapor contour and gas flows are analyzed, and then design factors of those combustion systems are recommended.

• Journal of Mechanical Science and Technology
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• v.14 no.2
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• pp.236-250
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• 2000

Compression ignition direct injection diesel engines employed a high pressure injection system have been developed as a measure to improve a fuel efficiency and reduce harmful emissions. In order to understand the effects of the pressure variation, many experimental works have been done, however there are many difficulties to get data in engine condition. This work gives numerical results for the high pressure effects on spray characteristics in wide or limited space with near walls. The gas phase is modelled by Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled using the discrete droplet model approach in Lagrangian form and the drop behavior on a wall is calculated with a new droplet-wall interaction model based on the experiments observing individual drops. The droplet distributions, vapour fractions and gas flows are shown in various injection pressure cases. In free spray case which the injection spray has no wall impaction, the spray dispersion and vapour fraction increase and drop sizes decrease with increasing injection pressure. The same phenomena appears more clearly in wall impaction cases.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.137-142
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• 1996

A new wall impaction model for spray and its assessment are described in this paper. The gas phase is modelled in terms of the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach. The droplet parcel contains many thousands of drops assumed to have the same size, temperature and velocity components. The droplet parcel equations of trajectory, momentum, mass and energy are written in Lagrangian form. The new drop-wall interaction model is proposed, which is based on experimental investigations on individual drops, and it is applied for the general non-orthogonal gird. The model is then assessed through comparison with experiments over a wide range of test conditions of sprays. The results are in good agreement with experimental data.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.1
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• pp.47-53
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• 1999

Small compression-ignition direct injection engines have been developed as a measure to improve a fuel efficiency and reduce harmful exhaust gases. Those small engines generally employ high injection pressure increase on the spray impacting on a wall is discussed in this paper. The gas phase is modelled by the Eulerian continuum conservation equations of mass momentum energy and fuel vapour fraction. The liquid phases is modelled following the discrete droplet model approach in Lagrangian form and the droplet wall interaction is modelled as a func-tion of the velocity normal to impaction lands. The droplet distributions vapor fractions and gas flows are analyzed in various injection pres-sure cases. The penetrations of wall spray and vapor increase and the Sauter mean diameter decreases with increasing injection pressure.

• Particle and aerosol research
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• v.18 no.4
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• pp.129-136
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• 2022

The line width of circuits in semiconductor devices continues to decrease down to a few nanometers. Since nanoparticles attached to the patterned wafer surface may cause malfunction of the devices, it is crucial to remove the contaminant nanoparticles. Physical cleaning that utilizes momentum of liquid for detaching solid nanoparticles has recently been tested in place of the conventional chemical method. Dropwise impaction has been employed to increase the removal efficiency with expectation of more efficient momentum exchange. To date, most of relevant studies have been focused on drop spreading behavior on a horizontal surface in terms of maximum spreading diameters and average spreading velocity of drop. More important is the local liquid velocity at the position of nanoparticle, very near the surface, rather than the vertical average value. In addition, there are very scarce existing studies dealing with microdroplet impaction that may be desirable for minimizing pattern demage of the wafer. In this study, we investigated the local velocity distribution in spreading liquid film under various impaction conditions through the CFD simulation. Combining the numerical results with the particle removal model, we estimated an effective cleaning diameter (ECD), which is a measure of the particle removal capacity of a single drop, and presented the predicted ECD data as a function of droplet's velocity and diameter particularly when the droplets are microns in diameter.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.18-26
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• 2001

OSKA engine was developed to remove the dense core of injection sprays. The engine uses impinging spray on a small pip, which spray after impinging is broken into smaller drops and disperses into fee space in chamber. In this paper the pip size is analyzed to give more dispersion of spray and fuel vapor. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form, and the droplet wall interaction is modelled as a function of the velocity normal to impaction lands. The droplet distributions, vapor fractions and gas flows are analyzed for various injection pressure cases. Numerical results indicate that the land diameter of 5.6mm has the best performance of spray dynamics and vaporization in the test sizes.

• Journal of ILASS-Korea
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• v.2 no.2
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• pp.8-15
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• 1997

Combustion chamber systems using spray impinged on walls have been studied for improving combustion characteristics in high speed direct injection diesel engines. The fuel spray injected in a small combustion chamber may be easily impinged and deposited on the wall. The fuel deposit has been considered as the cause for unburned emission due to difficulty of fuel-air mixing. In this paper w-shaped combustion chamber which has four raised pips on the side wall is introduced and discussed by comparing with conventional chamber with no pips. The computer code employing new spray-wall interaction model in general non-orthogonal grids is used in here. The model is applied into the new chamber shape with raised pips. In this chamber system four-hole nozzle is used, and the sprays injected from the each hole impact on lands raised from the chamber wall surface. After impacting, the sprays break up into much smaller drops and distribute over all the chamber space, instead of distributing just near the wall surface in conventional omega-shape. The results showed the potential of the w-shaped chamber employing pips for dispersing droplets so as tn avoid the fuel deposit regions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.619-629
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• 2003

A grease filter is used to remove grease generated from a cooking appliance in a kitchen. Since the inertial impaction is a dominant particle removal mechanism of the grease filter, the performance of the filter is greatly affected by the geometry. This numerical study has been conducted to investigate the effect of geometry on the performance of grease filters for four models having nominal flowrate of 100 m$^3$/h. Four models were designed by changing the shape of impaction surface, the length of eyelid, and the number of eyelids of the grease filter. The flow field and particle trajectories in the grease filter with a flow chamber were simulated using the commercial code of STAR-CD. The difference of air velocity and pressure distributions among four models was discussed in detail. The collection efficiency curves and the pressure drops of four models were also compared. It was found that the grease filter model with flat top surfaces shows highest performance among four models, having high particle collection efficiency and relatively low pressure drop. The cutoff diameter of this model representing 50-% collection efficiency is about 7.1 ${\mu}{\textrm}{m}$ for water droplets at 100 m$^3$/h.