• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.132-138
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• 2006

Numerical analysis about atomization and wall impingement process of hollow-cone fuel spray is performed by a modified KIVA code with hybrid model. The atomization process is modeled by using hybrid breakup model that is composed of Linearized Instability Sheet Atomization(LISA) model and Aerodynamically Progressed Taylor Analogy Breakup(APTAB) model. The Gosman model, which is based on the droplet behaviors after impingement determined by experimental correlations, is used for spray-wall impingement process. The LIEF technique was used to compare the results with those of experiment. The calculations and experiments are carried out at the ambient pressures of 0.1 MPa and 0.5 MPa and the ambient temperature of 293K. It was found that the calculated results show satisfactory agreement with experimental ones.

• Journal of ILASS-Korea
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• v.24 no.4
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• pp.185-193
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• 2019

The effervescent atomizer is one of twin-fluid atomizers that aeration gas enters into bulk liquid and two-phase flow is formed in the mixing section. The effervescent atomizer requires low injection pressure and small amount of aeration gas, as compared to other twin-fluid atomizers. In this study, cold flow test was conducted to investigate the spray characteristics of aerated impinging jets. The present effervescent impinging atomizers were composed of the aerator device and like-on-like doublet impinging atomizer which had different impinging angles. To analyze the spray characteristics such as breakup length and droplet size distribution, the image processing technique was adopted by using instantaneous images at each flow condition. Non-dimensional parameters, induced by the homogeneous flow model, were used to predict the breakup length. The breakup length was decreased with the mixture Reynolds number and impinging angle increasing. The result of droplets showed that the size distribution was axisymmetric about the center of the injector and their diameter tended to decrease with increasing GLR.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.971-978
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• 2007

A spray-wall impingement process of a hollow-cone fuel spray from the high-pressure swirl injector in the Gasoline Direct Injection (GDI) engine were experimented and calculated at various wall geometries. The Linearized Instability Sheet Atomization (LISA) & the Aerodynamically Progressed Taylor Analogy Breakup (APTAB) model and the Gosman model were applied to model the breakup and the wall impingement process of the hollow-cone fuel spray. The numerical modelings were implemented in the modified KIVA code. The calculation results of spray characteristics, such as a spray development process and a radial distance after wall impingement, compared with the experimental results by the Laser Induced Exciplex Fluorescence (LIEF) technique. The droplet size distribution and the ambient gas velocity field, which are generally difficult to obtain by the experimental methods, were also calculated and discussed. It was found that the radial distance after wall impingement and Sauter Mean Diameter (SMD) decreased with increasing a cavity angle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.156-160
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• 2006

This study investigated the characteristics of spray generated by a liquid-liquid co-axial swirl injector used in a combustor of the liquid rocket engine. The linear stability analysis[1] was introduced In liquid sheet breakup and Post[2]'s collision model which considers shattering was adopted on the collision model after breakup. Every model was implemented to KIVA[3], which was adopted as solve. To validate the implemented models the cases of high and low injection velocity were calculated respectively and each result agreed well with test results.

• Nuclear Engineering and Technology
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• v.22 no.4
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• pp.326-336
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• 1990

Recent experiments show the existence of spacer grid improves the heat removal from the fuel rods during the reflood phase of LOCA. The local heat transfer within and downstream of the grid is increased due to the earlier quenching than rod surface, shattering of the entrained droplets into smaller ones which can be more easily evaporated and enhanced turbulent effect. Therefore, the consideration of these phenomena is necessary for the DFFB regime which prevails above the water level during the reflood. In this paper, droplet breakup model at spacer grid has been developed and incorporated into RELAP5/MOD2. Verification calculations are carried out for FEBA tests which examine the thermalhydraulic performance of grid spacer during reflood.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.344-350
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• 2006

The present study investigates the characteristics of fire-driven heat flows and gas concentration in a compartment fire by using the modified VHS model (MVHS). The main idea of this model is to add some source terms for combustion products and oxygen consumption to the original VHS model for providing more accurate and useful information on gas concentration distributions as well as thermal fields. It is found that the present MVHS model shows fairly good agreement with the experimental data and the eddy breakup combustion model. The tilting angle of fire plume calculated by MVHS is larger than that of EBU model because the fire source of VHS is affected by ventilating flow less than EBU. However, this discrepancy is apparently reduced in the downstream region of fire source.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.5
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• pp.545-552
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• 2004

The purpose of this study is to improve the prediction ability of the atomization and vaporization processes of GDI spray. Several models have been introduced and compared. The atomization process was modeled using hybrid breakup model that is composed of Linearized Instability Sheet Atomization (LISA) model and Aerodynamically Progressed TAB (APTAB) model. The vaporization process was modeled using Spalding model and Abramzon ＆ Sirignano model. Exciplex fluorescence method was used for comparing calculated with experimental results. The experiment and computation were performed at the ambient pressure of 0.1 MPa, 0.5 MPa and 1.0 MPa and the ambient temperature of 293k and 473k. Comparison of calculated and experimental spray characteristics was carried out and the calculated results of GDI spray showed good agreement with experimental results.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.47-53
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• 2005

This paper presents the effects of ambient pressure on atomization characteristics of high-Pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. In order to investigate the atomization process numerically, the LISA-DDB hybrid model was utilized. This breakup model assumes that the primary breakup occurs when the amplitude of the unstable waves is equal to the radius of the ligament of liquid sheet near the nozzle and the droplet deformation induces the secondary breakup. The results provide the effect of ambient pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is also revealed that the accuracy of prediction of LISA-DDB hybrid model is pretty good in terms of spray developing process, spray tip penetration, and SMD distribution.

• Journal of Power System Engineering
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• v.21 no.4
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• pp.34-41
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• 2017

Diesel engines with compression-ignition type have superior thermal efficiency, durability and reliability compared to gasoline engine. To control emitted gas from the engines, it can be applied to alternative fuel without any modification to the engine. Therefore, in this study, as a basic study for applying emulsified fuel to the actual diesel engine, analysis of spray behavior characteristics of emulsified fuel was carried out simultaneously by experimental and numerical method. The emulsified fuel consist of diesel, hydrogen peroxide, and surfactant. The surfactant for manufacturing emulsified fuel is comprised of span 80 and tween 80 mixed as 9:1 and fixed with 3% of the total volume of the emulsified fuel. In addition, six kinds of emulsified fuel(EF0, EF2, EF12, EF22, EF32, and EF42) were manufactured according to the mixing ratio of hydrogen peroxide. The droplet and spray experiments were performed to observe the behavior characteristics of the emulsified fuel. The numerical analysis was carried out using ANSYS CFX to confirm the microscopic behavior characteristics. Consequently, rapid mixture formation can be expected due to evaporation of hydrogen peroxide in emulsified fuel, and it is confirmed that Reitz&Diwakar breakup model is most suitable as breakup model to be applied to the numerical analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.290-297
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• 2016

A two-phase Large Eddy Simulation(LES) has been conducted to investigate breakup and atomization of a liquid jet in a cross turbulent flow in a rectangular duct. Gas-droplet two-phase flow was solved by a coupled Eulerian-Lagrangian method which tracks every individual particles. Effects of liquid breakup models, sub-grid scale models, and a order of spatial discretization was investigated. The penetration depth in cross flow was comparable with experimental data by varying breakup model and LES scheme. SMD(Sauter Mean Diameter) distribution downstream of jet was analyzed.