• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2524-2529
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• 2008

The thermal system like a combustion chamber is believed to experience a significant instability problem with vibration in case that the thermal energy or the acoustic energy are transformed into a different form through a relevant path. This study deals with a numerically- predicted, Thermoacoustic instability in a Rijke tube by using a non-linear model for a heat source. The heating part where the energy transformation occurs actively is modeled after simulating two-dimensional cylinder case with constant surface temperature, and a nonlinear model that accounts for the transfer function of magnitude- and phase-characteristics is properly implemented so as to be dependent on the pulsation strength in the tube. The heat source model is observed to result in equivalent Thermoacoustic instabilities in the Rijke tube except low flow-rate cases in which the natural convection is dominant.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.88-93
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• 2017

Due to the requirement of the development of the precision manufacturing industry, the accuracy of machine tools has become a key issue in this field. A critical factor that affects the accuracy of machine tools is the feed system, which is generally driven by a ball screw. Basically, to improve the performance of the feed drive system, which will be thermally extended lengthwise by continuous usage, a thermal error compensation system that is highly dependent on the feedback temperature or positioning data is employed in the machine tool system. Due to the overdependence on measuring technology, the cost of the compensation system and low productivity level are inevitable problems in the machine tool industry. This paper presents a novel feed drive thermal error compensation system method that could compensate for thermal error without positioning or temperature feedback. Regarding this thermal error compensation system, the heat generation of components, principal of compensation, thermal model, mathematic model, and calculation method are discussed. As a result, the test data confirm the correctness of the developed feed drive thermal error compensation system very well.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.1-7
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• 2017

Aluminum alloys have been widely used in many fields such as electronic, structure, aero-space and vehicle industries due to their outstanding thermal and electrical conductivity as well as low cost. However, they have some difficulties for using in brazing process because of the strong oxide layer of $Al_2O_3$ on the surface of Al alloy. In addition, their melting point is similar to that of brazing filler metal resulting in thermal damage of Al alloys. Therefore, it is very important to understand the brazing principles, filler metal and its properties such as wetting, capillary flow and dissolution of base metal in the Al brazing process. This paper reviews the brazing principles, aluminum alloys, and brazing fillers. In the case of brazing principle, some formula was used for calculation of capillary force and the dissolution to obtain the best condition of Al brazing. In addition, the advanced research trends in Al brazing were introduced including thermal treatment, additive for improving property and decreasing melting point in Al brazing process.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.22-29
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• 2006

Gas turbine engine among Principal internal combustion engines has been mainly applied as an aero and industrial Power plant. In order to increase its thermal efficiency. it has been raised their pressure ratio of compressor and the turbine inlet temperature. To operate above the limit temperature of turbine material, turbine nozzle vanes should be cooled. For this the cooling air is bled from the compressor section of 9as turbine. Meanwhile, to keep high thermal efficiency of 9as turbine, turbine vanes are to be cooled by using small cooling air Therefore, the complex cooling passages are requested to be designed and evaluated the effectiveness of vane cooling by measuring turbine vane temperature. But it is very difficult or impossible for us to measure local turbine temperatures at actual temperature When local heat transfer coefficients are known these can be calculated, therefore this study has been investigated on obtaining these coefficients of turbine vane at room temperature using TLC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.955-961
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• 2013

This study aimed for the scientific approach of Korean traditional house, so called Hanok, by analyses of structural elements and thermal environmental performance. Hanok is a very unique vernacular architectural style of the Middle East Asia that fits with climate conditions of the Korean Peninsular, designed to withstand high temperature and humidity in summer and cold and dry in winter seasons. In order to evaluate thermal environment of Hanok, its sectional structure such as floor, wall, roof structure and Ondol which is Korean traditional floor heating system, was built in 3D, as well as heat transfer mechanism of its composing elements was analyzed through 3 dimensional steady state analysis. The results of the thermal environmental performance of Hanok will be used as a basic datum of design guidelines for accomplishing ecologic housing fitted with local climate.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.83-95
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• 2002

Thermal conductivity of ceramic fibrous insulator was analysed and predicted by using the modeling/simulation technique. Ceramic fibrous insulators are widely used as high temperature insulator on account of their lightweight mass and heat resisting properties. Especially it is suitable to protect the high speed aircraft and missiles from severe aero-thermodynamic heating. Thermal conductivity of ceramic fibrous insulator could be determined from the conductive heat transfer and the radiative heat transfer through the insulator. In order to estimate conductive thermal conductivity, homogenization technique was applied, while radiative thermal conductivity was computed by means of random number and radiation probability. Particularly radiation probability can make it possible to estimate the conductivity of fibrous insulator without any experimental constant. The calculated conductivity predicted in the present study have a reasonable accuracy with an average error of 7 percent to experimental data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.695-704
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• 2019

In hypersonic regime, the complicated interaction between the air and surface of aircraft results in intensive aerodynamic heating on body. Provided this phenomenon occurs on a hypersonic vehicle, the temperature of the body extremely increases. And consequently, thermal deformation is produced and material properties are degraded. Furthermore, those affect both the aerothermoelastic stability and thermal safety of structures significantly. With the background, thermal safety and dynamic stability are studied according to the altitude, flight time and Mach number. Based on the investigation, design guideline is suggested to guarantees the structural integrity of hypersonic vehicles in terms of both of thermal safety and dynamic stability.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.55-65
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• 2012

In the winter season, when the ventilation system is operating, the fresh cold air from the slot-type openings of broiler house which directly reached the animal zone can cause various problems such as thermal stress, decreasing of feed and water consumption, occurrence of respiratory disease, and etc. Therefore it is very important to control the trajectory of aero-flow from the slot openings to induce an efficient thermal heat change. Jet-drop distance model was proposed to predict and control the jet-trajectory. However their study was restricted due to the small scaled model and difficulties of measuring the Jet-drop distance. In this study, CFD was applied to analyze qualitatively and quantitatively the jet-drop distance in a real broiler house. The various variables were considered such as installed slot-angle, designed ventilation rate, and the outdoor ambient temperature. From the present study, two linear-regression models using the Jet-drop factor and corrected Archimedes number, and their R-squared values 0.744 and 0.736, respectively, were used. From this study, the applicability of CFD on the analysis of Jet-drop distance model was confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.27-30
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• 2007

In recent years, scientific community has found renewed interest in hypersonic flight research. These hypersonic vehicles undergo severe aero-thermal environments during their flight regimes. One of the most important topics of research in hypersonic aerodynamics is to find a reasonable way of calculating either the surface temperature or the heat flux to surface when its temperature is held fixed. This requires modeling of physical and chemical processes. Hyperbolic system of equations with stiff relaxation method are being identified in recent literature as a novel method of predicting long time behavior of systems such as gas at high temperatures. In present work, Energy Relaxation Method (ERM) has been considered to simulate the real gas flow over a 2-D cylinder. Present heat flux results over the cylinder compared well with the experiment. Thus, real gas effects in hypersonic flows can be modeled through energy relaxation method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.31-38
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• 2001

This paper deals with the micro turning property of setting angle using diamond tool. The bed of the system has used the granite which has the thermal and vibrational characteristics superior to the cast iron bed for the common machine tool. To minimize the inner and outer vibration of the fuming system, an air pad system was manufactured and tested. The aero-static spindle system which has the excellent rotation accuracy was designed and manufactured. As a result of the micro-cutting test on aluminum alloy, tool setting angel have effected on surface roughness. From the results, the micro-cutting conditions hope to provide the useful actual data using in industrial fields.