• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1811-1820
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• 2005

Thermo-acoustic instability of methane/ air flames in an industrial gas-turbine combustor is numerically investigated adopting CFD analysis. The combustor has 37 EV burners through which methane and air are mixed and then injected into the chamber. First, steady fuel! air mixing and flow characteristics established by the burner are investigated by numerical analysis with single burner. And then, based on information on the flow data, the burners are modeled numerically via equivalent swirlers, which facilitates the numerical analysis with the whole combustion system including the chamber and numerous burners. Finally, reactive flow fields within the chamber are investigated numerically by unsteady analysis and thereby, spontaneous instability is simulated. Based on the numerical results, scaling analysis is conducted to find out the instability mechanism in the combustor and the passive control method to suppress the instability is proposed and verified numerically.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1465-1469
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• 2009

Darrieus wind turbine blade is one of the vertical wind power system in which the lift of blade is used. In the calculation of wind power for the type of that, the multiple streamtubes method is known as an effective method. But it has big difference in the region of higher tip speed ratio because the incoming air velocity is used in the calculation of lift. The incoming air velocity is reduced from inlet to outlet continually by transferring energy to the wind blade. In this study, the air velocity on the blade, which is called blade velocity, is obtained with newly developed algorithm and used to determine the lift. And it is verified that applying blade velocity on the lift calculation cause the power prediction to improve dramatically in the region of higher tip speed ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.201-207
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• 2015

Turbine-generator torsional response is caused by interaction between electrical transient air-gap torque and mechanical characteristics of turbine-generator shafts. If torsional shaft torque exceeds a certain threshold, the loss of fatigue life may occur and, in the end, it is possible to happen permanent shaft failure. Therefore, it is required to understand the torsional response for reliable operation and protection of turbine-generator shaft system. In this paper, we introduced multi-mass modeling method of turbine-generator shaft system using mechanical-electrical analogy and state-space equation to verify the transient torsional response based on ElectroMagnetic Transient Program (EMTP). These simple realization methods for turbine-generator shaft torsional response could be helpful to understand torsional interaction phenomena and develop the transient torque reduction countermeasures for turbine-generator shaft system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.1
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• pp.34-41
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• 1991

The effect of flow conditions on flow measurement is difficult to identify from the inherent characteristics of the flowmeters and flow standard system. A new experimental approach has been attempted to detect the turbine meter error due to inlet flow conditions. In this try not only the design of the turbine meter package but also the data analysis method was altered. It was found that k factor slope of the turbine meter responds to the change of flow conditions in the test line with higher sensitivity than the degree of the data scattering. The flow standard system of $0.1m^3/s$ was chosen for the investigation. The systematic and random error of the system were less than ${\pm}0.08%$ and ${\pm}0.13%$ respectively.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.291-300
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• 1999

Currently under development is an airborne auxiliary power unit with 100 Kw equivalent power, which is composed of a centrifugal compressor, a reverse annular combustor, and a radial turbine. Air-foil bearings are used in this power unit to eliminate the oil supplying system, which can reduce the system complexity and weight. The high speed generator is adopted as an electric power generation and engine starting system, which can also eliminate the reduction gear system. Not only electric power but also pneumatic power is provided by bleeding the compressed air This power unit is aimed for the multi-purpose use such as a primary power unit In the army weapon system, an auxiliary power and environmental control unit in a next-generation tank, and a smoke generating unit.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.155-160
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• 2001

The low NOx characteristics have been investigated to develop the combustor for micro turbine. The lean premixed combustion technology was applied to reduce the NOx emission. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of $450\sim650K$ were supplied to the combustor through the air preheater. The temperature and emissions of NOx and CO were measured at the exit of combustor, The exit temperature and NOx were increased and CO was decreased with increasing inlet air temperature. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The NOx was decreased with decreasing the equivalence ratio. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.4. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The NOx was decreased and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.598-603
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• 2005

Recently, the advanced industries using micro parts are rapidly growing. The appearance of ultra-precision feed mechanism and the development of control system make it possible to process parts in sub millimeter scale by mechanical methods. Micro endmilling is one of the prominent technology that has wide spectrum of application field ranging from macro parts to micro products. So, micro stairs have been trying to cut by using high revolution air turbine spindle and micro-endmill, and studying for magnitude of cutting force. This investigation deals removal characteristics of burr generated by micro endmilling process. Also, decreasing of burr is significant problem in making smooth and precise parts in micro endmilling. In micro endmilling, the material removal rate(MRR) and cutting forces are very small. This paper presents an investigation on the machining characteristics for micro stairs by using ultrahigh-speed air turbine spindle in machining.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.152-159
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• 2001

In this paper it is intended to set-up a sound model of the 60,000rpm 100kW prototype APU gas turbine rotor-bearing system, and particularly to investigate the influences of the tie shaft on the rotordynamic characteristics of the entire APU gas turbine rotor-bearing system, employing the dual shaft model. Firstly, a mock-up APU rotor has been constructed to test and verify the model. Analytical natural frequency results have agreed with the corresponding modal test ones to within 5% difference. Then, the rotordynamic characteristics of the prototype APU rotorbearing system have been investigated. Natural vibration and unbalance response analyses results have shown that the inner tie shaft resonance can cause high enough vibration of the outer main rotor shaft. This could be a concern as the rotor journals operate on very thin air film at high speed. It is concluded as a conservative design practice that the inner tie shaft should be explicitly modeled in the rotordynamic analysis of the APU rotor-bearing system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.829-832
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• 2010

For gas turbine engine starting, external power should be supplied with engine to accelerate to suitable rotational speed for air and fuel ignition conditions. Electric starting system for small gas turbine engine has simple system and light weight, so it is generally used for small aircraft. For system analysis of gas turbine engine electric starting system, Characteristics of battery, start motor, engine drag torque should be analyzed and theirs temperature effects should be considered. In this paper, preliminary design procedure of small gas turbine engine electric starting system and major design parameters were described.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.704-711
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• 2008

Integrated gasification combined cycle (IGCC) is an environment friendly method of using coal. Several commercial IGCC plants have been built worldwide during the past decade, and a domestic development project has also been launched recently. Operation and performance characteristics of a gas turbine in the IGCC plant deviates from those of original gas turbines due to several factors such as increased amount of fuel supply and integration with other components. In this study, performance of a gas turbine in the IGCC plant is analyzed considering its integration with the air separation unit (ASU). Influence of the degree of integration (split of air supplies to ASU from the auxiliary compressor and the gas turbine compressor) on the system performance is investigated. In addition, effect of modulating nitrogen return flow from the gasifier to the gas turbine on the operating characteristics of the gas turbine is examined.