• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.918-919
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• 2015

Because of environmental regulations in emissions control area, the demand for ships to use LNG as fuel is increasing. Orders for domestic shipbuilders to produce LNG carriers are steadily increasing. However, major appliances such as spray pump, main cargo pump and others have been relied on imports. Therefore, development of pump motor using at cryogenic temperature is necessary. Operating temperature of an induction motor is at $-163^{\circ}C$. At this low temperature, the resistivity of a motor coil is quite different from normal ones, and so does the torque characteristics of motor. This paper presents a designing method of a cryogenic induction motor for LNG pump. The variation of resistivity of motor coil is considered in the design process. The heat source such as core-loss, hysteresis-loss and copper-loss are analyzed to prevent the LNG evaporation which may cause the motor failure.

• Journal of ILASS-Korea
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• v.18 no.3
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• pp.140-145
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• 2013

Sub/supercritical spray experiments were conducted, and cryogenic nitrogen and gaseous argon were selected for simulants. liquid nitrogen and gaseous argon were injected in subcritical case, and supercritical nitrogen and near-critical gaseous argon were injected in near-critical/supercritical cases. shadowgraph method was used to visualize spray, and analyzed about the breakup length. The breakup length was measured from numbers of Instantaneous shadowgraph Images from each case, and they were compared with momentum flux ratios and density ratios. It was observed that the relation between breakup length and momentum flux ratio was fitted into former experiment results. and the reasonable constant was suggested about the relation between breakup length and density ratio.

• Journal of ILASS-Korea
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• v.26 no.1
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• pp.18-25
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• 2021

The objective of this study is to investigate the effect of cryogenic intake air temperature on the injected fuel droplet behavior in a compression ignition engine under the different start of energizing timing. To achieve this, the intake air temperatures were changed from -18℃ to 18℃ in steps of 9℃, and the result of fuel evaporation rate, Sauter mean diameter, and equivalence ratio distributions were compared. When the intake air temperature decreased in steps of 9℃, less fuel was evaporated by about 3.33% because the cylinder temperature was decreased. In addition, the evaporated fuel amount was increased with retarding the start of energizing timing because the cylinder temperature raised. However, the difference was decreased according to the retarded start of energizing timing because the cylinder pressure was also increased at the start of fuel injection. The equivalence ratio was reduced by 5.94% with decreasing the intake air temperature. In addition, the ignition delay was expected to longer because of the deteriorated evaporation performance and the reduced cylinder pressure by the low intake air temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.61-65
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• 2010

To research and develop a liquid rocket engine injector, it needs empirical studies about the hydrodynamic and spray characteristics such as pressure drop, mixing and atomization. In this study, the design and implementation of lab-scale cold-flow/hot fire test stand which can supply cryogenic propellant and be controlled by time-critical LabVIEW cyclogram logic has been done. In order to visualize the spray of a liquid-centered swirl coaxial injector in cryogenic condition, LN2-GN2 cold-flow test has been done, and combustor assembly and thrust bed for LOX-$GCH_4$ hot-fire test have been fabricated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.3
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• pp.222-229
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• 2012

The cooling of a injector effects on the vapor pressure of cryogenic oxidizer spray, and it decides the phase transition point at the ignition process, when the combustion chamber pressure increases drastically. The phase transition of oxidizer spray affects the ignition characteristics, and several ignition tests with the LOx/$GCH_4$ uni-element coaxial swirl injector was performed in the different initial temperatures of oxidizer injector, in order to investigate the effect of injector cooling on the ignition transient characteristics. At the transition point of oxidizer phase, where the combustion chamber pressure increased over the LOx vapor pressure, the temporary quenching phenomenon of the flame occurred. The lower temperature of chilled down injector and tubing tends to move up the phase transition earlier.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.7
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• pp.999-1004
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• 2015

In this paper, the study presents the development of 34kW class cryogenic induction motor using LNG Pump. Operating temperature of an induction motor using LNG Main Cargo Pump is at −163℃. Due to variation of the resistivity, these motor have different torque characteristics. So, it should design to considering the resistivity change. The most important consideration of induction machine operating is cryogenic temperature. If the temperature rise, LNG is vaporized. it is a major cause of pump failure. There are several causes of heat source like coreloss, hysterisysloss, copperloss. This paper analyzed the thermal distribution of the induction motor at rated speed operation.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.137-145
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• 2017

This paper describes numerical modeling of transcritical and supercritical fluid flows within a liquid propellant rocket engine. In the present paper, turbulence is modeled by standard $k-{\varepsilon}$ model. A conserved scalar approach in conjunction with multi-environment probability density function model is used to account for the turbulent mixing of real-fluids in the transcritical and supercritical region. The two real-fluid equations of state and dense-fluid correction schemes for mixtures are used to construct thermodynamic data library based on the conserved scalar. In this study, calculations are made on two cryogenic nitrogen jets under different chamber pressures. Sensitivity analysis for two different real-fluid equations of sate is particularly emphasized. Based on numerical results, precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results show that the current real-fluid model can predict the essential features of the cryogenic liquid nitrogen jets.

• Design & Manufacturing
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• v.13 no.3
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• pp.41-47
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• 2019

In conventional machining, the use of cutting fluid is essential to reduce cutting heat and to improve machining quality. However, to increase the performance of cutting fluids, various chemical components have been added. However, these chemical components during machining have a negative impact on the health of workers and cutting environment. In current machining, environment-friendly machining is conducted using MQL (minimum quantity lubrication) or cryogenic air spraying to minimize the harmful effects. In this study, the injection nozzle that can combined injecting minimum quantity lubrication(MQL) and cryogenic gas was designed and the shape optimization was performed by using computational fluid dynamics(CFD) and design of experiment(DOE). Performance verification was performed for the designed nozzle. The diameter of the sprayed fluid at a distance of 30 mm from the nozzle was analyzed to be 21 mm. It was also analyzed to lower the aerosol temperature to about 260~270K.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.2
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• pp.41-47
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• 2017

By using liquid and gaseous nitrogen as simulants, effects of pintle opening distance and simulant supplying condition on spray from pintle injector were investigated qualitatively. The experiment was performed by fixing the liquid supply pressure and varying the opening of the pintle and the supply pressure of gaseous nitrogen. Shadowgraph method with CCD camera was used for image visualization, and the differences of liquid-gas spray were compared by image post processing. In case of liquid nitrogen single injection, as the opening distance was increased, the injection speed was decreased. Therefore, the end of liquid sheet were converged to the center of spray. In the case of liquid nitrogen/Gaseous nitrogen spray, although shadowgraph images look similar to each other, It is shown that it can be analysed by image post processing.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.1-9
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• 2017

The cryogenic nitrogen spray of a swirl injector has been numerically investigated using three dimensional LES turbulence model to analyze the dynamic characteristics under supercritical condition. To predict the precise nitrogen properties under supercritical condition, SRK equation of state, Chung's method for viscosity and thermal conductivity and Takahashi's correlation based on Fuller's theory for diffusion coefficient are implemented. The complex flow structures due to interaction between flow field and acoustic field are observed inside and outside the injector under supercritical condition. FFT, POD, and DMD techniques are employed to understand the coherent structures. By implementing the FFT, the dominant frequencies are identified inside and outside the injector. The coherent flow structures related to the dominant frequencies are visualized using the POD and DMD techniques. In addition, the DMD provides the damping coefficient which is related with the instability prediction.