• Journal of ILASS-Korea
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• v.17 no.2
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• pp.77-85
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• 2012

The CFD simulation of diesel spray tip penetrations were compared with 0-D simulation for experimental data obtained with common rail injection system. The simulated four injection patterns include single, pilot and split injections. The CFD simulation of the spray penetration over these injection patterns was performed using the KIVA-3V code, which was implemented with both the standard KIVA spray and original gas jet sub-models. 0-D simulation of the spray tip penetration with time-varying injection profiles was formulated based on the effective injection velocity concept as an extension of steady gas jet theory. Both the CFD simulation of the spray tip penetration with the standard KIVA spray model and 0-D simulation matched better with the experimental data than the results of the gas jet model for the entire fuel injection patterns.

• Journal of ILASS-Korea
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• v.22 no.1
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• pp.29-35
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• 2017

This paper describes the effects of spray breakup model constants on spray and combustion characteristics in single cylinder compression engine. KIVA-3V code coupled with a CHEMKIN chemistry solver was used for numerical analysis. In this study, spray simulations and combustion simulations are studied simultaneously. Spray simulation was conducted in constant volume to reduce the effects of air-flow as swirl or tumble. The model validation was conducted and there are little difference between experiments and simulation, this differences were reasonable. In spray simulation, the effects of model constants on spray tip penetration, spray patter and SMD were studied. Furthermore, the analysis of effects of breakup variables on combustion and emissions characteristics was conducted. The results show the KH-RT breakup model constants affects spray and combustion characteristics strongly. Increasing KH model variable (B1) and RT model constants ($C_{\tau}$, $C_{RT}$) induced slower breakup time.

• Journal of ILASS-Korea
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• v.5 no.4
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• pp.12-32
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• 2000

The recent trends in numerical simulation of various spray phenomena are reviewed in this article. Major subtopics are atomization/breakup, collision/coalescence, wall collision, interfacial transfer, droplet dispersion, two-phase injection and spray combustion. Each submodel has been under continuous refinement and validation against more extensive data base by advanced laser diagnostic techniques. Most uncertainty in current spray simulations come from these physical submodels, not from excessive computational constraints.

• Journal of Hydrogen and New Energy
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• v.27 no.6
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• pp.727-736
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• 2016

Numerical simulations of n-heptane spray characteristics in a constant volume combustion chamber under diesel engine like conditions with increasing ambient gas density ($14.8-142kg/m^3$) and ambient temperature (800-1000 K) respectively were performed to understand the non-vaporizing and vaporizing spray behavior. The effect of fuel temperature (ranging 273-313 K) on spray characteristics was also simulated. In this simulation, spray modeling was implemented into ANSYS FORTE where the initial spray conditions at the nozzle exit and droplet breakups were determined through nozzle flow model and Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) model. Simulation results were compared with experimentally obtained spray tip penetration result to examine the accuracy. In case of non-vaporizing condition, simulation results show that with an increment of the magnitude of ambient gas density and pressure, the vapor penetration length, liquid penetration length and droplet mass decreases. On the other hand vapor penetration, liquid penetration and droplet mass increases with the increase of ambient temperature at the vaporizing condition. In case of lower injection pressure, vapor tip penetration and droplet mass are increased with a reduction in fuel temperature under the low ambient temperature and pressure.

• Journal of ILASS-Korea
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• v.13 no.1
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• pp.22-27
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• 2008

The false diffusion occurs generally when the flow is oblique to the grid lines and when there is a non-zero gradient of the dependent variable in the direction normal to the flow. This numerical problem can overestimate diffusion terms in the continuous phase, causing the numerical inaccuracy for the simulation of impinging sprays on inclined walls because most of spray calculation uses rectangular grid system. Therefore, the main objective of this article is to investigate numerically the influence of false diffusion on numerical simulation for spray-wall impingement on inclined walls. It is found that unlike the spray impingement normal to the wall, the numerical diffusion exists in the case when diesel sprays impinge on the inclined walls with different angles. The results show that the correction function should be considered for accurate prediction of spray penetration length and more elaborate numerical schemes should be utilized to reduce the false diffusion.

• Journal of Mechanical Science and Technology
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• v.17 no.9
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• pp.1371-1379
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• 2003

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• Journal of ILASS-Korea
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• v.19 no.3
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• pp.123-129
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• 2014

A diesel spray overall SMD (Sauter mean diameter) in a spray chamber was simulated with CFD by varying the compression ratio in the spray chamber from 18:1 to 100:1. The gas densities of the spray chambers for the compression ratios of 18:1 and 100:1 were 17.97 and $74.8kg/m^3$, respectively. Standard KIVA-3V code was used for the CFD simulation. Various fuel injection patterns such as single injection, pilot injection and split injection were used for the CFD simulation. Fuel injection pressures for the simulated diesel sprays are 90 and 120 MPa. As the compression ratio increases, the CFD simulated SMD was decreased, which was generally in agreement with previous experimental studies.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.974-979
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• 2003

This study aimed to analyze spray characteristics and the ambient flow field in the mixture preparation state of the premixed combustion stage. It is very important to understand the spray characteristics and the fuel injection conditions in direct injection diesel engine because the emission gas compositions from diesel engines are related to spray formation processes of the premixed combustion stage. The numerical simulation was performed using the STAR-CD which is a commercial CFD code. Computed results of the transient high pressure diesel spray were compared with experimental results of the same spray injection condition in the constant volume chamber. The results show that spray patterns of numerical simulation agree with this experimental results comparatively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.992-999
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• 2009

The focus of this study is placed on the behavior characteristics of gasoline spray under condition field of room temperature and pressure. To analyze the behavior and flow characteristics of injected fuel spray is important in speculation of mixture formation process. Also the exhausted emissions from actual engines can be controlled by the analyzed results. The ${\varphi}$(degree of freedom) and K(energy ratio of particle motion) are selected as the simulation parameter. The factors affect characteristics of spray structure, and the factors are included in the sub-program of the KIVA-II code. In this study, the simulation study by modified KIVA-II code was conducted and the calculated results obtained by the modified KIVA-II code show good agreements with experimental results. As a result, applying the improved TAB model with ${\varphi}$=8 and K=2 to simulation analysis of the KIVA-II code is sufficiently useful for analyzing the macro characteristics in spray structure, such as the spray tip penetration of injected fuel spray.

• Korean Journal of Computational Design and Engineering
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• v.13 no.4
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• pp.296-304
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• 2008

Recently, various attempts are being done to apply off-line programming system to field of paint robot. But most commercial simulation softwares have problems that are slow simulation speed and not support various painting paramenters on simulation. This paper proposes enhanced paint simulation method for off-line programming system. For these, this method used the mathematical model of flux field from a previous research. The flux field has the flux distribution function, which reflects on the feature of paint spray. A previous research derived this flux distribution function for an integral function and calculated paint thickness function for an integral function. But if flux distribution function is defined as an integral function, it is inadequate to use for real-time simulation because a number of calculation is needed for estimation of paint thickness distribution. Therefore, we defined the flux distribution function by numerical method for reducing a mount of calculation for estimation of paint thickness. We derived the equation of paint thickness function analytically for reducing a mount of calculation from the paint distribution function defined by numerical method. In order to prove proposed paint simulation method this paper compares the simulated and measured thickness. From this comparison this paper show that paint thickness distribution is predicted precisely by proposed spray paint simulation process.