• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3467-3472
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• 2007

The effects of the wall geometry on the spray-wall impingement process of a hollow-cone fuel spray emerging from a high-pressure swirl injector of the Gasoline Direct Injection (GDI) engine were investigated by means of a numerical method. The ized Instability Sheet Atomization (LISA) & Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model for spray atomization process and the Gosman model were applied to model the atomization and wall impingement process of the spray. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental ones by the Laser Induced Exciplex Fluorescence (LIEF) technique. It was found that the radial distance of the cavity angle of 90$^{circ]$ after wall impingement was the shortest and the ring shaped vortex was generated near the wall after spray-wall impingement process.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.42-49
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• 2004

The present article investigates the influence of droplet drag models on predictions of diesel spray behaviors under ultra-high injection pressure conditions. To consider drop deformation and shock disturbance, this study introduces a new hybrid model in predicting drag coefficient from the literature findings. Numerical simulations are first conducted on transient behaviors of single droplet to compare the hybrid model with earlier conventional model. Moreover, using two different models, extensive numerical calculations are made for diesel sprays under ultra-high pressure sprays. It is found that the droplet drag models play an important role in determining the transient behaviors of sprays such as spray tip velocity and penetration lengths. Numerical results indicate that this new hybrid model yields the much better conformity with measurements especially under the ultra-high injection pressure conditions.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.466-471
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• 2003

The purpose of this study is to obtain the accurate prediction for the atomization and vaporization processes of GDI spray. Atomization process is modeled using hybrid model that is composed of Linearized Instability Sheet Atomization (LISA) model and Aerodynamically Progressed TAB (APTAB) model. Vaporization process is modeled using Spalding model and Abramzon & Sirignano model. To obtain the experimental results for comparing with calculated results, the cross-sectional images of liquid and vapor phases and SMD distribution were acquired by exciplex fluorescence method and Phase Doppler Analyzer respectively. The experiment and computation was performed at the ambient pressure of 0.1 MPa, 0.5 MPa, 1.0 MPa and the ambient temperature of 293K, 473K. The calculated results by modified KIVA-II code show good agreement with experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.12
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• pp.48-58
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• 2006

The spray and combustion characteristics of liquid jet in cross flow with variation of injection angle are numerically studied. Numerical analysis was carried out using KIVA code, which may be used to generate numerical solutions to spray and chemical reactive fluid problem in three space dimensions and modified to be suitable for simulating liquid jet ejected into the cross flow. Wave model and Kelvin- Helmholtz(KH) /Rayleigh-Taylor(RT) hybrid model were used for the purpose of analyzing liquid column, ligament, and the breakup of droplet. Penetration length increases as flow velocity decreases and injection velocity increases. Numerical error increases as inflow velocity increases. The results of flame propagation contour in combustion chamber and local temperature distribution, combustion emissions were obtained.

• Journal of ILASS-Korea
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• v.13 no.2
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• pp.91-98
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• 2008

In the present study, in order to understand the overall spray combustion characteristics of DME fuel as well as to identify the distinctive differences of DME combustion processes against the conventional hydrocarbon liquid fuels, the sequence of the comparative analysis have been systematically made for DME and n-heptane liquid fuels. To realistically represent the physical processes involved in the spray combustion, this studyemploys the hybrid breakup model, the stochastic droplet tracking model, collision model, high-pressure evaporation model, and transient flamelet model with detailed chemistry. Based on numerical results, the detailed discussions are made in terms of the autoignition, spray combustion processes, flame structure, and turbulence-chemistry interaction in the n-heptane and DME fueled spray combustion processes.

• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.294-301
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• 2005

The instabilities in rocket engines and gas turbine combustors due to the interaction between the fluid flow (acoustics) and the heat transfer (thermal energy) are called thermoacoustic or combustion instabilities. Almost all analysis assumes constant hot section temperature for Modern mathematical analysis of acoustic oscillations in Rijke type devices. However, it is impossible to predict whether a system is stable or not because the flame or heater response model can have a dramatic effect on predicted growth rates. In this study, A standard ${\kappa}-{\varepsilon}$ turbulent model and hybrid combustion model(eddy breakup model and chemical reaction) were used. After steady solution was gotten, unsteady calculation is simulated by perturbating on pressure boundary. As a result, we obtained the relationship of equivalence ratio and frequency by numerical simulation, and they are comparable to the experimental result. In addition, in spite of these results, there are limitations of using turbulent and combustion model in simulation method of thermoacoutic instability