• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.1-9
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• 2012

The gas jet from a coaxial porous injector for two-phase flows is discharged from the porous surface, which encloses the center liquid jet, and the gas and liquid jet interact with each other physically. The wall injected gas jet transfers the radial momentum effectively while the radial gas jet develops to axial jet, and the performance of atomizing and mixing can be improved. In this study, the Weber number and the ratio of momentum flux were controlled by changing the gas injection area and the mass flow rate of the gas jet, and a study on the spray characteristics at the cold-flow test using water and air simulant was performed. It is concluded that the radial momentum transfer concept of a coaxial porous injector gives a positive effect on the atomization and mixing of the two-phase spray.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.585-592
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• 2015

Effects of opening distance on liquid-gas spray of pintle injector were experimentally investigated under atmospheric condition by using water and air as simulants of propellants. Discharge coefficients($C_d$) and mass flow rates were calculated with various injection conditions; 0.1 bar - 1.0 bar for water pressures and 0.2 mm - 1.0 mm for the pintle opening distances. Spray angles were measured from the spray images that were obtained by a shadowgraphy method. When opening distance is 0.2 mm, liquid sheet is not formed properly and it show non-uniform spray. than it can result in combustion instability. it has a weak correlation between the momentum flux ratio and the spray angle, while it has a strong correlation between the momentum ratio and spray angle. Finally the spray angles reduced exponentially when the momentum ratio increased and the spray angles converged to about 40 degrees.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.163-172
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• 2002

The turbine system composed of a nozzle and a rotor is used to drive turbopumps while gas passes through the nozzle, potential energy is converted to kinematic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of a turbine system is investigated using compressible fluid dynamic theories with some pre-determined design requirements (i.e.,pressure ratio, rotational speed, required power etc.) obtained from a liquid rocket engine (L.R.E.) system design. For simplicity of a turbine system, impulse-type rotor blades for open type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow rate compared to the close-type system. In this study, a partial admission nozzle is adopted to maximize the efficiency of the close-type turbine system. A design methodology of the a turbine system has been introduced. Especially, a partial admission nozzle has been designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design for a 10 ton thrust level of L.R.E is presented.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.646-652
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• 2016

Biomass is regarded as one of the promising energy sources to deal with the depletion of fossil fuels and the global warming issue. Biocrude-oil can be produced through the fast pyrolysis of biomass feedstocks such as wood, crops, agricultural and forestry residues. It has significantly higher viscosity than that of conventional petroleum fuel and contains solid residues, which can lower the spray and atomization characteristics when applied to the burner. In addition, biocrude-oil consists of hundreds of chemical species derived from cellulose, hemicellulose and lignin, and evaporation characteristics of the biocrude-oil droplet are distinct from the conventional fuels. In the present study, a numerical study was performed to investigate the evaporation characteristics of biocrude-oil droplet using a simplified composition of the model biocrude-oil which consists of acetic acid, levoglucosan, phenol, and water. The evaporation characteristics of droplets were compared at various surrounding air temperatures, initial droplet diameters, and ethanol mixing ratios. The evaporation time becomes shorter with increasing air temperature, and it is much sensitive to the air temperature particularly in low temperature ranges. It was also found that the biocrude-oil droplet evaporates faster in cases of the smaller initial droplet diameter and larger ethanol mixing ratio.

• Solar Energy
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• v.19 no.4
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• pp.45-53
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• 1999

This report Introduces a total heat exchanger in a solar air-conditioning system using Lithium Chloride(LiCl) solution. The hot and humid outside air is cooled and dehumidified by LiCl solution that is sprayed on the packed layer of the total heat exchanger. LiCl solution once diluted is concentrated again in a regenerator using solar energy. Three types as the packed materials were used in this experiment and the dehumidification performance was evaluated by the value of $k_xa(kg/h{\cdot}m^3{\cdot}{\Delta}x)$, overall mass transfer coefficient based on a humidity ratio potential difference, the influence of inlet LiCl solution flow rate, air flow rate, packed layer height on $k_xa$ was investigated. It was found that air flow rate, LiCl solution flow rate, packed layer height for all types had a great influnce on the value of $k_xa$.

• Journal of the Korean Chemical Society
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• v.42 no.5
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• pp.526-530
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• 1998

Analysis of trace impurities in the gases has been very important with the development of semi-conductor related industry. Particularly, the contamination of the gas handling systems in a semi-conductor plant by the air has been a trouble to the manufacturers. Thus, the analysis of the air components in the system has been a task to the analysts. In this study, we report the analysis data with a expanded uncertainty for the trace impurities of nitrogen and argon in the bulk helium and hydrogen. All data show a good correspondence, exhibiting reliable statistical error ranges.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.500-505
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• 2011

In this paper, two types of micro-optic submersion detection systems are proposed and demonstrated. The structures are based on the transmission and reflection of incident light, respectively. Two collimators are separated by 10 mm and installed face to face in straight line. The incident light transmits from one side of collimator to the other through the air, but the optical loss is below 1 dB. On the other hand, when the sensors are submersed into water, most of optical power scattered into water. The systems monitor the dramatical power change to alarm the submersion. Reflection type of sensor system has a Bragg grating at the end of the sensor for back-reflection of sensing signal. This is for simple configuration of systems. The performance of two sensor systems are described in detail.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.65-70
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• 2008

The numerical simulation on the internal flow characteristics of the adaptor in a two-fluid nozzle has been performed to investigate the effects of carrier air supplying parameters using a commercial code. The four adaptor models with the different positions in the carrier air supplying port were considered at the fixed conditions of urea-water solution and carrier air supplying. As the results from the numerical analysis, the internal pressure of the adaptor was varied with the port position for carrier air supplying, and it shows lower pressure value than the atmospheric pressure. Consequently, the flowrate of urea-water solution issuing from the feeding injector with the adaptor varied up to 30% with the port positions for the carrier air supplying. When the carrier air is supplied from the side from the feeding injector axis and the upper part from the feeding injector tip, the flowrate of urea-water solution issuing from the feeding injector with the adaptor show higher value than other carrier air supplying conditions.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.37-46
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• 2006

The outside environment is very severe while aircraft is cruising. Especially small particle of icing in cold air condition can have negative influence on aircraft performance. If ice particle is attached to leading edge of wing, it can change wing configuration and decrease flight quality. If icing particle is attached to inlet of engine, it can damage compressor blade and have negative influence to aircraft safety. We make icing simulation device with liquid air system for analyzing about variation of engine performance due to incoming of icing to engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.55-62
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• 2009

Fracture behavior of ceramic dome port cover on air breathing engine using liquid and solid fuel propulsion system was carried out in this study. Fracture characteristics was tested and estimated using scaled model of ceramic dome port cover by Shock tube. Fracture behavior was obtained by the fracture pressure from pressure sensor and observed the scattering phenomena of fracture specimen using high speed camera. Results obtained from this study can be used in the base data of dome port cover design for an air breathing engine.