• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.104-109
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• 2004

On this paper study is concentrated on the breakup and atomization characteristics of spray formed by impinging jet injectors(like-doublet) used in liquid rocket engine(LRE). On the process of breakup and atomization, injection velocity and ambient gas pressure are the main parameters, so that these are used as variables that specify the experimental condition. Injection velocity varied from 3m/s to 30m/s and ambient gas pressure changed from 0.1MPa to 4.0MPa with nitrogen gas. As results, measured physical quantities decreased with increasing injection velocity and ambient gas pressure. But the decreasing ratios are different from those of the theory.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.1
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• pp.8-22
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• 2015

Most jet spray and atomization simulations are done with the Eulerian method which has inherent disadvantage in representing jet breakups and droplets. Full Lagrangian particles method called Smoothed Particle Hydrodynamics(SPH) is used in this work. We develop the SPH code and perform validations that confirm the suitability of our SPH method for simulating liquid jet atomization problem. Then, we conduct the simulation of liquid-liquid swirl coaxial injector for comparison against the experimental data.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.225-232
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• 2003

With an aim placed on its exploitation on practical injector design, liquid phase mixing due to unlike split triplet impinging element is experimentally investigated by a series of cold tests. Non-reacting kerosene/water spray simulates the kerosene/LOX propellant combination. Measurements of local mixture ratio distribution were made for different injection configurations and different momentum ratios. Mixing and mixing controlled characteristic velocity efficiencies are measured in terms of oxidizer/fuel jet momentum ratio from 0.5 to 8. Extent of mixing and its influence on hot performance are estimated in terms of mixing efficiency and mixing controlled characteristic velocity. Envelope of design locus for optimum mixing quality and corresponding maximum hot performance are proposed. Effects of momentum ratio, orifice diameter ratio and jet velocity ratios are also presented and discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.691-699
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• 1997

The effects of concave hemispherical surface curvature on the local heat transfer from a turbulent round impinging jet were experimentally investigated. The liquid crystal transient method was used for these measurements. This method, which is a variation on the transient method, suddenly exposes a preheated wall to an impinging jet while video recording the response of liquid crystals for the measurement of the surface temperature. The Reynolds number ranges from Re=11,000 to 50,000, the nozzle-to- surface distance from L/d=2 to 10, and the surface curvature from D/d=6 to 12.The present results are also compared to those for the flat plate case. In the experiment, the local Nusselt numbers tend to increase in all regions with an increasing surface curvature. The maximum Nusselt number for all Reynolds numbers occurred at L/d .ident. 6 and a second maximum in the Nusselt number occurred at R/d .ident. 2 for both Re=23,000 and Re=50,000 in the case of L/d=2 and for Re=50,000 only in the case of L/d=4. Meanwhile, as the surface curvature increases, the value of the secondary maximum Nusselt number decreases. All the other cases exhibit monotonically decreasing values of the Nusselt number along the curved surface. The stagnation point Nusselt numbers are well correlated with Re, L/d, and D/d.

• Journal of ILASS-Korea
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• v.10 no.2
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• pp.41-47
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And. it is extremely difficult to increase gasoline engine efficiency and to reduce NOx and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper. internal EGR(exhaust gas recirculation) effect is suggested to realize CAI combustion. An experimental study was carried out to achieve CAI combustion using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). A flame trap was used to simulate internal EGR effect and to increase flame propagation speed in the CVCC. Flame propagation photos and pressure signals were acquired to verify internal EGR effect. Flame trap creates high speed burned gas jet. It achieves higher flame propagation speed due to the effect of geometry and burned gas jet.

• Journal of ILASS-Korea
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• v.19 no.2
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• pp.69-74
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• 2014

The comparison of the flow characteristics between circular and swirl jets which were controlled by the spinner attachment inside the airtube were conducted in this study. Swirl jet means a flow in whirls by mixing the flow of axial and tangential direction. Swirl flow has been used for the improvement of the combustion efficiency in the combustor. This flow is controlled by the spinner which has several vanes inclined by certain angles to the axial direction. In this study, angle of vane $30^{\circ}$ and diameter ratio of outlet to inlet of the airtube 0.73 were made. These spec. should find on the general gun type burner built in the domestic small size boiler. As the flow characteristics, axial and tangential velocities were measured by using the 2-D hot-wire velocimeter system and analyzed statistically. And also this research conducted a practical experiment considering to the attached belongings likes as ignitor, nozzle etc. on the airtube of the gun type burner. As a result, swirl occurred at the occasion of beingness and flow region extended considerably toward the radial direction. But effect of swirl did not transmit to the downstream. And the complicated flow was appeared regardless of the existence of spinner because of the effect of belongings.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.320-324
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• 2017

Effect of elliptical orifice on the spray characteristics of liquid jet ejecting into subsonic crossflows were experimentally studied. Circular/elliptical plain-orifice injectors, which had different ratios of the orifice length to diameter and major axis to minor axis, were used for transverse injection. Compared with the previous research, breakup lengths of elliptical nozzles are shorter than circular nozzles at all experimental condition. Cavitation/hydraulic flip are considered as a reduction in the breakup length at all circular/elliptical nozzle. In the case of liquid column trajectories, major axis which was placed to the crossflows, increases the frontal area of the liquid column exposed to the crossflows. Hence, the aerodynamic force exerted on the jet is increased and the penetration depth is reduced.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.77-84
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• 2003

It is an aim of this study to perform extensive numerical study for analyzing the anisotropic turbulence effects on spatial and temporal behaviors of diesel sprays after wall impingement. The turbulence model of Durbin is used for comparisons with the $k-\varepsilon$ model. The turbulence-induced dispersions of droplets are considered to describe the anisotropy of turbulence effectively and the spray/wall interactions are simulated using the model of Lee and Ryou. The present study investigates the internal structures of impinging diesel sprays such as Sauter mean diameter (SMD), loca1 droplet velocities, and local gas velocities and also compares the results predicted by two turbulence models with the experimental data. The Durbin's model considering the anisotropy of turbulence predicts both gas and droplet tangential velocities better than the$k-\varepsilon$ model does. It is concluded that the anisotropy of turbulence should be considered in simulating impinging diesel sprays.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.2.1-2.1
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• 2011

Electrospray deposition (ESD) technique is fast finding its applicability in the field of thin film device manufacturing processes and the ease and cost efficiency attached to ESD process with possible integration with batch manufacturing technologies is the potential future of thin film device manufacturing. As the name suggests, the deposition phenomenon should solely be a spray achieved through electrostatic forces. In fact it is an imbalance between the surface forces arising because of the surface tension of the liquid to be sprayed and Maxwell stresses which are induced because of the electric field, that pull the liquid downwards from the capillary into a stable jet which further disintegrates into smaller droplets because of coulomb forces and hence a cloud of charged, mono-dispersed and extremely diminutive (sometimes up to femtolitres) droplets is achieved. The present talk is going to be exclusively about the electrospray process concepts, generation and possible applications.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.157-167
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• 2003

The exciplex fluorescence technique with the TMPD (tetamethyl-Ρ-phenylene-diamine) / naphthalene dopant system was applied in a combustion-type constant-volume spray chamber. A detailed set of calibration experiments has been performed in order to quantify the TMPD fluorescence signal. It has been demonstrated that the TMPD fluorescence intensity was directly proportional to concentration, was independent of the chamber pressure, and was not sensitive to quenching by either water vapor or carbon dioxide. Using a dual heated-jet experiment, the temperature dependence of TMPD fluorescence up to 1000 K was measured. The temperature field in the spray images was determined using a simple mixing model, and an iterative solution method was used to determine the concentration and temperature field including the additional effects of the laser sheet extinction. The integrated fuel vapor concentration compared favorably with the measured amount of injected fuel when all of the liquid fuel had evaporated.