• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.65-72
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• 2014

Turbine rotor-pyrostarter coupled test was performed for the verification of thermo-structural suitability of a turbopump turbine. Newly developed solid propellant and design concept were used in pyrostarter development. In case of turbine rotor, rotor configuration modification and post EDM machining process are adopted in rotor manufacturing respectively for the thermal stress relief and the surface integrity improvement on the blade surfaces. In the test, combustion gas of pyrostarter was directly ejected from the nozzles and impinged on the stationary turbine rotor specimen through the identically shaped flow passage of turbopump. Three kind of thermal load - design to extreme condition - test were performed and no damages were found on the turbine rotor specimens.

• Journal of Aerospace System Engineering
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• v.14 no.5
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• pp.26-32
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• 2020

In this study, a facility was constructed to supply liquid nitrogen to simulate combustion instability in a liquid rocket combustor. The pressurization and supply performances were predicted and verified through different experiments. The liquid nitrogen supply system was composed of a pressurized supply system, and a dome regulator was used to adjust the pressure of the pressurant. A cavitation venturi was used to control the mass flow rate of liquid nitrogen. The condition of liquid nitrogen supply was a mass flow rate of 2.55 kg/s and the venturi inlet pressure was above 100 bar. Based on the initial experiment, it was observed that the predicted amount of the pressurant was not sufficiently supplied and the target pressure was not supplied due to a drop in tank pressure. Through the modification of the established facilities, the target mass flow rate was successfully supplied and the cryogenic liquid nitrogen supply facility was verified.

• Korean Journal of Acupuncture
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• v.34 no.3
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• pp.109-115
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• 2017

Objectives : Many researches have studied warm needling technique to standardize its treatment by temperature measurement and material differences in the effectiveness. The purpose of this study is to compare the temperature changes of the acupuncture needle shaft during the combustion process of the moxa stick to determine the heat transfer pattern of the warn needling. Methods : A moxa stick($7{\times}8mm$) was connected to one side of the needle shaft using a stainless steel needle(ø 0.3 mm, ø 0.5 mm, ø 0.8 mm, shaft length 40 mm) with the needle handle removed. During the warm needling, temperature changes of the needle shaft were observed with an infrared camera(Flir E30) and an infrared thermometer(TESTO 845). Results : In the normal condition, heat transmit of needle shaft increased at spots 10 mm and 25 mm below the moxa stick. The amount of heat transmit increased with the diameter of needle shaft. However, when the heat shield was installed to exclude radiant heat from the moxa stick, heat transfer was less at 10 mm below the moxa stick and no temperature change was observed at 25 mm below the moxa stick. Heat transfer by warm needling does not reach the end of needle shaft even in ø 0.8 mm needle. Conclusions : It is suggested that the radiant heat of moxa stick results in the heat transmit of acupuncture needle shaft. Thus, radiant heat transmit must be considered as one of the heat transfer characteristics of the warm needling.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2339-2358
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• 1993

Since the rate and completeness of combustion in direct injection engines were controlled by the characteristics of gas flow fields and sprays, an understanding of those was essential to the design of the direct injection engines. In this study the numerical simulations of injection pressure effects on the characteristics of gas flow fields and sprays were preformed using the spray model that could predict the interactions between gas fields and spray droplets. The governing equations were discretized by the finite volume method and the modified k-.epsilon. model which included the compressibility effects due to the compression/expansion of piston was used. The results of the numerical calculation of the spray characteristics in the quiescent environment were compared with the experimental data. There were good agreements between the results of calculation and the experimental data, except in the early stages of the spray. In the motoring condition, the results showed that a substantial air entrainment into the spray volume was emerged and hence the squish motion was relatively unimportant during the fuel injection periods. It was found that as the injection pressure increased, the evaporation rate of droplets was decreased due to the narrow width of spray and the increased number of droplets impinged on the bottom of the piston bowl.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.805-810
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• 2002

Development of a small gas-turbine combustor for 100㎾ class APU(Auxiliary Power Unit) has been performed. This combustor is a reverse-annular type and has a tangential swiller in the liner head to improve the fuel/air mixing and flame stability. Three main and three pilot fuel injectors of the simplex pressure-swirl type are used. The performance target at the design condition includes a turbine inlet temperature of l170k, a combustion efficiency of 99%, a pattern factor of 30%, and an engine durability of 3000 hours. Under developing the combustor, we conducted the performance test of our first prototype(TS1) with some variants. As a result of the test, the performance targets of the combustor are satisfied except that the pattern factor is about 4% higher than the target value. Therefore, the second prototype(TS2) was redesigned and the performance test was conducted with the critical focus on the pattern factor and the exit mean temperature. We adopted TS2 four variants to check the improvement of the pattern factor. As a result, the pattern factors of several variants were satisfied with the performance target. Finally, the TS2A variant was chosen as a final combustor fur our APU model.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.320-327
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• 2003

A CFD (Computational fluid Dynamics) research is conducted for the investigation of the fuel alteration of MBTU (medium-Btu) gas in IGCC gas turbine combustor. The computational analysis method of the gas turbine combustor is constructed by incorporating MBTU gas reaction and fuel NOx models into commercial CFD code. With the use of the present analysis method, comparisons are made on the flow velocity, the chemical species and the temperature distributions, and on the flame shape and behavior of gas turbine combustor firing natural gas and MBTU gases (coal gas, heavy residue oil gas). Furthermore, the NOx formation characteristics and the turbine matching condition of the combustor are analyzed. Based on the computed analysis results, the present study provides the directions for the redesign and the design modification of IGCC gas turbine combustor firing MBTU gas as alternative fuel.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.171-176
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• 2010

Using a hydrogen blended compressed natural gas (HCNG) as a fuel for IC engines has a significant meaning in terms of achieving a reduction of automotive exhaust emissions as well as preparing for an upcoming hydrogen economy by constructing hydrogen infrastructure. In addition, a HCNG engine has higher thermal efficiency than a CNG engine, which is another advantage that makes HCNG fuel considered as a future alternative for natural gas. Therefore, in this study, idling operation of a 11 litre HCNG bus engine was investigated in terms of fuel consumption rate and emissions characteristics. The results show that fuel consumption rate was decreased more than 20% by use of HCNG and all the emissions were significantly reduced in idling condition.

• Atmosphere
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• v.27 no.4
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• pp.483-498
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• 2017

Sky view factor can quantify the influence of complex obstructions. This study aims to evaluate the best available SVF method that represents an urban thermal condition with land cover in complex city of Korea and also to quantify a correlation between SVF and mean air temperature; the results are as follows. First, three SVF methods comparison result shows that urban thermal study should consider forest canopy induced effects because the forest canopy test (on/off) on SVF reveals significant difference range (0.8, between maximum value and minimum value) in comparison with the range (0.1~0.3) of SVFs (Fisheye, SOLWEIG and 3DPC) difference. The significance is bigger as a forest cover proportion become larger. Second, R-square between SVF methods and urban local mean air temperature seems more reliable at night than a day. And as the value of SVF increased, it showed a positive slope in summer day and a negative slope in winter night. In the SVF calculation method, Fisheye SVF, which is the observed value, is close to the 3DPC SVF, but the grid-based SWG SVF is higher in correlation with the temperature. However, both urban climate monitoring and model/analysis study need more development because of the different between SVF and mean air temperature correlation results in the summer night period, which imply other major factors such as cooling air by the forest canopy, warming air by anthropogenic heat emitted from fuel oil combustion and so forth.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.1-6
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• 2013

Using natural gas-hydrogen blended fuel (HCNG) in a heavy duty vehicle is regarded as an alternative to meet reinforced emission regulation compared to a recent direct injection (DI) diesel engine. Hydrogen can lead stable lean combustion even under leaner mixture condition than natural gas, so that improving not only thermal efficiency but also $NO_x$ emissions. In the present study, the feasibility of HCNG engine's commercialization was accessed with HCNG fuel (30% $H_2$ and 70% natural gas) in aspect to the reliability and possibility to reduce $NO_x$ emissions by the level of EURO-VI under various operating conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.148-154
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• 2018

When shooting small arms, the inner surface temperature is heated up to about $700{\sim}1,000^{\circ}C$ by the friction of the bullet and the inner wall of the barrel and the combustion of propellant. High-temperature propellant gas and high-speed movement of the bullet cause corrosion of the inner wall, which is noticeable immediately in front of the chamber. In this study, the mechanical properties of Cr-Mo-V steel, which is the base material, were tested using Taguchi experimental design to find the best nitriding treatment conditions. For the nitriding process, the working time, salt bath temperature, and salt concentration were combined as three conditions and placed in the $L_9(3^4)$, orthogonal array table. The thicknesses of the white layer and the nitrogen diffusion layer were measured after nitriding under each condition in a salt bath furnace. Durability was evaluated by measuring the degree of dispersion through actual shooting because it was difficult to evaluate the mechanical properties of the cylinder inner structure. As a result, it was confirmed that the durability was optimal at $565^{\circ}C$, 1 hour, 0.5%. These optimal conditions were selected by the statistical analysis of the Minitab program(ver.17).