• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.658-664
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• 2019

In the development of the liquid rocket engine using the pintle injector, spray characteristics such as spray angle, droplet size, and distribution of the droplets are dominant parameters. Three different kind of multi hole type pintle tip and a continuous type pintle tip were designed. In the case of multi hole pintle tip, SMD result did not have a significant difference depending on the number of holes. In analysis with visualization images, however, the droplets were uniformly distributed as the number of holes increased. Liquid droplets from continuous type pintle tip were finely atomized and dispersed uniformly than those from multi-hole type pintle tip. In addition, the thrust control by adjusting the liquid injection area of the pintle is suitable for the continuous type, which is easier to face-shutoff rather than the multi hole type. The spray angle of each pintle tip according to TMR was measured to derive a specific tendency and corresponding empirical formula.

• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.49-54
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• 2012

The objective of this study is to investigate the capacity of epoxy injection method using low pressure mixed with high pressure. Injection depth test and flexural strength test were respectively performed on $40{\times}45{\times}35$ cm and $100{\times}10{\times}40$ cm specimens. Considered as the test variables were injection type(low pressure, low and high pressure), crack width(0.25 mm, 0.50 mm), injection direction(upper, lower, side), and epoxy viscosity(low, medium, high). Test results showed that low viscosity epoxy injection depth of injector using low pressure mixed with high pressure for upper direction were 23 cm and tension strength of crack face repaired by injector using low pressure mixed with high pressure was larger than that of concrete.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.112-119
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• 2002

Three dimensional numerical heat transfer analysis was carried out against periodically arranged fuel injectors of the liquid rocket engine. A finite volume method based on SIMPLE algorithm was adapted which gave a good agreement with the published results of the heat transfer problem of a backward facing step. The Nusselt number and pressure drop increased as the distance between the injector elements decreased. When the Reynolds number increased, the Nusselt number increased but nondimensionalized pressure drop decreased slightly.

• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.226-231
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• 2006

The fuel injector is a pa.1 that controls the fuel supply of automotive engine. The housing of the fuel injector supports the rod, the needle valve and the solenoid. In this study, the rigid-plastic FE-analysis by using the design of experiments (DOE) and the response surface methodology (RSM) has been performed to produce the product reducing the under-fill and the maximum effective strain. From the results of DOE, the stem of counter punch and the face angle of punch at the $1^{st}$ process, and the stem of punch at the $2^{nd}$ process were determined as the significant design variables far each response such as the upper under-fill, lower under-fill and the maximum effective strain. From the results of RSM, the optimal values of the design variables have been also determined by simultaneously considering the responses.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.401-405
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• 2011

Although the APU combustors were developed successfully, it could face many unexpected hardships in a engine or a system operated under the severe environment. This study is to be verified and settled by experimently and analytically of the problems and issues occurred in a variety of engine and system operation tests.

• Archives of Plastic Surgery
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• v.42 no.3
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• pp.282-287
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• 2015

Background Morphological changes that accompany aging, such as wrinkles and skin laxity, are particularly prominent on facial skin. Recently, facial rejuvenation using the hydrofilling effect of hyaluronic acid (HA) filler has been employed for improvement of skin texture. In this study, we studied rejuvenating effects of stabilized HA (Restylane Vital) through direct intradermal injections. Methods A total of 30 female patients underwent a series of procedures on face, including three sessions at intervals of four weeks. A total of 2 mL of Restylane Vital was injected along the whole face using an automatic injector. Improvement of skin surface roughness, elasticity, brightness, moisture, and fine wrinkles was evaluated. Patient satisfaction was evaluated, and pictures of patients were taken at each visit and 6 months after last treatment session. Scoring for each patient was performed by three doctors according in five subjects. Moisture, oil and elasticity were measured before the procedure and before the last treatment in 10 patients. Results The majority of patients (77%) were satisfied with the therapeutic outcomes. Approximately 66% of patients responded that the effects of this procedure persisted for longer than four months, and the majority of patients (77%) wanted to undergo this procedure again and would recommend this procedure to acquaintances. Regarding doctors' evaluation, scores for improvement of skin surface roughness, elasticity, and brightness were significantly higher than those for improvement of moisture and fine wrinkle. Conclusions Intradermal injection of HA can have a rejuvenating effect on dry and tired facial skin, especially in improvement of skin surface roughness.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.57-64
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• 2012

Although the APU combustors were developed successfully, it could face many unexpected hardships in an engine or a system operating under the severe environments. But, it is not easy to change the combustion field or combustor structure at the engine/system development stage. So we must suggest practical ways to optimize the value quantitatively by engine test and flow analysis, and verify those by the cyclic test. This paper describes reverse-annular type combustor troubleshooting processes for verifying and settling of the problems and issues occurred in various engine and system operation tests by experiment and analysis.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4
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• pp.105-112
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• 1996

A linear acoustic analysis for baffled rocket combustion chambers has been developed. This study provides the comprehensive theoretical background for the baffle as one of the stabilizing devices in a liquid rocket propulsion system. Several specific effects of baffles are presented as mechanisms by which baffles eliminate instability. Included are longitudinalization of transverse waves inside baffle compartments, severe restriction of velocity fluctuations near the injector face, and decreased normal mode frequency of the chamber.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1021-1025
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• 2017

Numerical heat/flow analysis was performed on a liquid rocket engine head with the cooling water manifold to ensure the durability of a ground test facility for heat exchanger. Through these studies, the shapes of the injector and the flow path were determined and applied to the head of the engine under development. Firing tests were conducted to verify the designed coolant manifold and no thermal damage was found on the engine-head-face. Comparing the combustion test results with the numerical analysis, the outlet temperature of coolant showed a difference of about $15^{\circ}C$. This trend is reasonable considering existence of LOX manifold, thermal barrier coating, and the actual location of flame.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.61-68
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• 2015

Reactive sprays of two propellant combinations(GOx/kerosene and $GN_2O$/ethanol) were observed and compared with each other as a basic research of visualizing supercritical combustion. A shadowgraph imaging method was used to visualize the reactive sprays, and shadowgraph images were converted to density gradient magnitude images to analyse the structure of reactive sprays. The gas-liquid interface of GOx/kerosene spray showed rougher boundary and steeper density gradient near the injector face than the $N_2O$/ethanol at similar combustion chamber pressure. Spray core length was calculated from averaged density gradient magnitude images and it was revealed that spray core length of GOx/kerosene was shorter than that of $GN_2O$/ethanol, although momentum flux ratio of GOx/kerosene propellant combination was lower.