• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.26-33
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• 2003

Recess is a geometrical configuration shape that the exit surface of an inner injector is located at a certain length inward from that of an outer injector. It is known to have the characteristics that it can augment mixing efficiency and flame stabilization through internal mixing of propellant in it. So, various experiments, such as backlit stroboscopic photography, phase Doppler particle analyzer(PDPA) and mechanical patternator, were performed at several recess lengths to grasp its effect on the spray characteristics of spray angle, breakup length, atomization and' mixing. Recess length was normalized to dimensionless recess number and two principal mechanisms of impingement and swirl recovery were introduced to explain its influence on the spray characteristics. The effect of recess on SMD doesn't appear significantly near the recess number where mixing efficiency attains to the maximum, whereas mass distribution and mixing efficiency are changed considerably. Thus, it can be inferred that a certain optimum recess number exists, where mixing efficiency becomes the maximum.

• Journal of the Korean Society of Safety
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• 제13권3호
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• pp.102-111
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• 1998

This study was concerned with the development of a heavy duty rust-converting agent, the function of which is to form metal complex coatings, containing vinyl halide-acrylic terpolymer emulsion, defoamer, emulsifying agent, glass flakes, chelating agent such as gallotannic acid, gallic acid, and pyrogallic acid, and other additives. The resulted emulsion products(Sample No.1~No.5) were characterized through test either in the forms of emulsions, which include Viscosity, Penetration rate, Acidity and Film drying rate test, or in the forms of coated layer on rusty steel substrates by FT-IR, which include hardness, gloss, salt spray, adhesion and flame retardant test. The test results are as follows ; Penetration rate(0.1~0.4 mm/min), Solid content(70%), Acidity (pH 1.8~2.0), Specific gravity(1.30~1.35), Film drying rate(108min, RH 40% ; 150min, RH 80%), Gloss(83~92, incident angle $60^{\circ}$; 88~97, incident angle $85^{\circ}$), Pencil hardness(4H~5H), Adhesion (100/100), Salt spray test(>720Hr), LOI(%) value(38%), Vertical burning test(UL 94-v-l). According to the various performance of specimens show above, the evaluation of the availability of this heavy duty rust-converting agent can be concluded that all the samples(No.1~No.5) are capable of being used in the field of chemical plant and in the hazard areas of fire and explosion potential. It was observed that the properties of sample No.2, especially gloss and hardness, were much better than that of the other samples.

• Journal of Korean Society of Environmental Engineers
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• 제29권1호
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• pp.23-30
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• 2007

The ultimate objective of this study is to develop oxygen-enriched combustion techniques applicable to the system of practical industrial boiler. To this end the combustion characteristics of lab-scale LNG combustor were investigated as a first step using the method of numerical simulation by analyzing the flame characteristics and pollutant emission behaviour as a function of oxygen enrichment level. Several useful conclusions could be drawn based on this study. First of all, the increase of oxygen enrichment level instead of air caused long and thin flame called laminar flame feature. This was in good agreement with experimental results appeared in open literature and explained by the effect of the decrease of turbulent mixing due to the decrease of absolute amount of oxidizer flow rate by the absence of the nitrogen species. Further, as expected, oxygen enrichment increased the flame temperatures to a significant level together with concentrations of $CO_2$ and $H_2O$ species because of the elimination of the heat sink and dilution effects by the presence of $N_2$ inert gas. However, the increased flame temperature with $O_2$ enriched air showed the high possibility of the generation of thermal $NO_x$ if nitrogen species were present. In order to remedy the problem caused by the oxygen-enriched combustion, the appropriate amount of recirculation $CO_2$ gas was desirable to enhance the turbulent mixing and thereby flame stability and further optimum determination of operational conditions were necessary. For example, the adjustment of burner with swirl angle of $30\sim45^{\circ}$ increased the combustion efficiency of LNG fuel and simultaneously dropped the $NO_x$ formation.

• Journal of the Korean Society of Propulsion Engineers
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• 제6권2호
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• pp.29-36
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• 2002

Experiments have been performed to investigate the effect of secondary venturi tip angle on flow and spray characteristics in gas turbine combustor with a swirl cup assembly. Three variations of secondary venturi tip angle are made: converging, straight and diverging angles. It is found that the variation of venturi tip angle results in the significant changes of flow and spray characteristics in gas turbine combustors, such as the size and location of recirculation zones. drop size and mass distribution affecting combustion efficiency and NOx emissions. In diverge case, central toroidal recirculation zone(CTRZ) exists near the exit, which is known to be beneficial for flame stability. But in converge case, the finest SMD distribution and uniform mass distribution are found and CTRZ is longer than other cases. Consequently, high combustion efficiency and low pollutant emission are expected in converge case.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.259-267
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• 2001

The flow field in a cylinder of a 4-valve pentroof engine is studied using the KIVA-3V code. Turbulence is generated from the jet flow through valves and broken down to the small scale eddies in the compression process. It is known that the tumble effectively keeps turbulence during the compression process. In the combustion process, turbulence is known to enhance flame speed by increasing mass, momentum and heat transfer rates. The effects of the intake port angles on the flow and combustion characteristics are studied in this study. To study the effect of turbulence on the combustion process, Cantore combustion model is applied in this study.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1995년도 제2회 KOSCI Workshop
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• pp.105-121
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• 1995

The objective of this study is to find out the design data for gas burner with an axal and radial type nozzles. The design parameters are chosen as the stabilizer type, the jet hole size of gas nozzle, the distance between gas nozzle and stabilizer, the size of stabilizer and the hole size of stabilizer, the stabilizer type with or without air swirler, the angle of swirler. For the experimental test combustor sizing ${\phi}1.3m{\times}L4.5m$ is designed and manufactured, in which the set up of power diagram, the exhaust gas analysis, blow-off test, the flame temperature and the direct photography are performed.

• Journal of the korean Society of Automotive Engineers
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• 제14권4호
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• pp.31-38
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• 1992

The objective of this study is to determine the ignition feasibility of a single shot, air-assisted gasoline fuel injector operated in a constant volume combustion chamber under atmospheric condition. A number of parameters has been selected for this experiments, such as dwelling time, spark gap position(r,z), spark electrode geometry, supplied air and fuel masses and spray cone deflector angle. On-site visual inspection of the instantaneous flame glow was chosen as one way to judge the successful ignition. In addition, chamber pressure and occasional photography were mobilized as for data recording. It was clearly observed that there was an entrainment air-fuel mixture toward spray axis from the spray formation and its development later on. The optimum ignition conditions were found for those parameters given above.

• Journal of the korean Society of Automotive Engineers
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• 제8권2호
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• pp.31-42
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• 1986

The prediction of performance, exhaust emissions and EGR effect is made by the SI engine cycle simulation. In this simulation several models are employed - two zome, thermodynamic combustion, mass fraction burned, heat transfer, chemical equilibrium, chemical kinetics for NOx, laminar flame speed for ignition delay. The chemical species in burned gas considered are 13 species-CO$_{2}$, CO, $O_{2}$, H$_{2}$O, H$_{2}$,OH, H, O, N$_{2}$, NO$_{2}$, N, Ar - and the cylinder pressure, burned and unburned zone temperature and composition of gas are calculated at each crank angle through the compression, ignition delay, combustion and expansion process. To check the validity of the model, experimental study is done for measuring emissions, combustion pressure and engine output. The predicted values for pressure and emissions show qualitative agreement with the measured data and the EGR effect also shows similar tendency.

• Journal of the korean Society of Automotive Engineers
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• 제5권4호
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• pp.47-61
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• 1983

In this paper the simulation of a thermodynamic power cycle for a 4-stroke, single-cylinder, spark-ignition engine was studied. In this simulation the cylinder volume was restricted to two zones, a burnt and an unburnt zone, and the convective heat transfer from cylinder contents to surroundings was considered. The chemical species in burnt gas considered was 12 species including H$_{2}$O, H$_{2}$, OH, H, N$_{2}$, NO, N, CO$_{2}$, CO, $O_{2}$, O and Ar. Using this model, computer program for compression, ignition and expansion processes was composed and pressure, temperature and composition of cylinder gas at each crank angle were computed. The composition of CO$_{2}$, CO, $O_{2}$ in the burnt gas when exhaust valve opens, the maximum temperature, the maximum flame speed and the combustion duration were also computed as a function of equivalence ratio. The relation between burnt mass fraction and burnt volume fraction was also computed.

• Journal of ILASS-Korea
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• 제24권3호
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• pp.130-136
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• 2019

Spray visualization of a vaporizer fuel injection system of a micro turbo jet engine was experimentally studied. The fuel heating by combustion was simulated by the high pressure steam generator and combustor inlet air from the centrifugal compressor was simulated by compressed air stored in the high pressure air tank. Spray visualization was performed with single vaporizer, and then six vaporizers which are same number of micro turbojet engine were used. As a results, the spray characteristics of the vaporizer were understood with pressure difference of the combustor inlet air and the fuel supply pressure. Spray angles with three types of vaporizer configuration were measured. In the results, guide vane configuration has a wider spray angle than the straight tube and smooth curve tube with a swirler, so it is expected that the fuel will be effectively distributed inside the combustor flame tube.