• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.153-159
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• 2015

In this study, a 2-W micro-gas turbine engine was designed using micro-electro-mechanical systems (MEMS) technology, and analytical and experimental investigations of its potential under actual combustion conditions were performed. An ultra-micro-gas turbine contains a turbo-charger, combustor, and generator. A compressor, turbine blade, and generator coil were manufactured using MEMS technology. The shaft was supported by a precision computer numerical control machined air bearing, and a permanent magnet was attached to the end of the shaft for generation. An analysis found that the cooling effect of the air bearing and compressor was sufficient to cover the combustor heat, which was verified in an actual experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.331-336
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• 2011

The three-dimensional complex curvature of the airfoil complicates the manufacture and repair of gas-turbine components. As a result of the developments in computer technology since the early 1990s, CNC-based technologies for machine tools and related programs have been increasingly applied in the gas turbine industry. In particular, fiveaxis simultaneous machines with adaptive functions have proven its excellent flexibility and productivity due to the capability in determining the 3D data from the unknown curvature. A well-organized robot system with eight-axis simultaneous control can lead to powerful standardization and high productivity. We summarize and review CNC technologies and their applications in the gas turbine industry, with a discussion of the manufacture and repair of gas turbine parts.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.2
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• pp.48-55
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• 1999

Performance analysis of a 50KW turbo-generator gas turbine engine with a recuperator was studied. Recuperated cycle has been employed to meet maximum fuel economy and ultra low emissions especially for military and vehicular engines. From thermodynamic stand point, it is known that recuperative cycle can contribute most to enhance thermal cycle efficiency for the Pressure ratios under 10 and of comparatively low turbine inlet temperature. Efficiency of a simple cycle with a recuperator increases relatively about 30% than without one at effectiveness of 0.5. Pressure losses in the heat exchanger less than 5.2% is considered in the design process. A tubular type heat exchanger is selected for this particular engine because it can provide simple construction as well as structural sturdiness and excellent leak tightness.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.281-284
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• 2006

An intelligent performance diagnostic program using the Neural Network was proposed for PW206C turboshaft engine. It was selected as a power plant for the tilt rotor type Smart UAV (Unmanned Aerial Vehicle) which has been developed by KARI (Korea Aerospace Research Institute). The measurement parameters of Smart UAV propulsion system are gas generator rotational speed, power turbine rotational speed, exhaust gas temperature and torque. But two measurement such as compressor exit pressure and compressor turbine exit temperature were added because they were difficult each component diagnostics using the default measurement parameter. The performance parameters for the estimate of component performance degradation degree are flow capacities and efficiencies for compressor, compressor turbine and power turbine. Database for network learning and test was constructed using a gas turbine performance simulation program. From application results for diagnostics of the PW206C turboshaft engine using the learned networks, it was confirmed that the proposed diagnostics could detect well the single fault types such as compressor fouling and compressor turbine erosion.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.183-188
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• 2003

The present work was conducted to build a propulsion system for an airship. For this purpose, free shaft gas-turbine was modified to produce electrical power. he experiments were carried out to analyze the driving rotor condition at various power shaft loads. From this analysis, an appropriate damping device was required, and the changeable inertial moment from the fly-wheel was applied. Without the appropriate damping device, instability was found, and it was resulted as power loss. Also the amount of inertial moment was certified by the performance of dynamic transient effects from the engine test results. Knowledge gained from this research could benefit the propulsion and power conversion community by increasing the better understanding of shaft loads and inertial effects.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.171-171
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• 2011

헬륨냉동계통은 연구용 원자로인 하나로에서 냉중성자를 생산할 수 있도록 설치된 수조내기기 내의 감속재인 수소가 정상적으로 열 사이펀을 유지하기 위한 주요 계통이다. 헬륨냉동계통은 헬륨가스를 압축하는 헬륨 압축부분과 헬륨가스를 팽창시켜 저온을 생성시키는 헬륨 팽창부분으로 나누어진다. 헬륨 압축부분은 두 개의 스크류가 맞물려 회전하면서 약 1.05 bar(a)의 헬륨가스를 최대 13 bar(a)까지 압축시키는 압축기가 있으며, 헬륨 팽창부분인 냉동박스의 팽창 터빈은 self-acting gas bearing에 의해 구동되며, 저온모드 운전 시작시 헬륨 압축부분에서 일부의 가스는 팽창 터빈 축(shaft)으로 유입되어 회전속도가 서서히 증가하면서 고속으로 회전하여 극저온의 헬륨가스(14~18 K)를 생성하는 주요 기기이다. 헬륨을 팽창하는 부분인 냉동박스 내로 헬륨 압축가스를 유입하기 전에 압축된 헬륨가스 내 불순물의 순도를 분석하여 냉동박스의 주요 부품인 팽창터빈의 운전에 영향을 미치지 않는 것이 가장 중요하다. 따라서 헬륨 저압측에 헬륨가스 내 불순물 즉, 수소($H_2$), 수분($H_2O$), 질소($N_2$), 탄화수소류(CxHy) 및 오일(Oilaerosol) 등의 함량을 분석하기위해 가스 분석기가 설치되어 있으며, 냉동박스 내로 유입되기 전에 헬륨압축에서 순환되는 가스 내 불순물인 수분, 질소, 탄화수소류 및 오일은 10 vpm 이하이어야 하며, 수소 함량은 0.1 % 이내이어야 한다. 헬륨 압축부분에서 순환되는 가스의 불순물이 요구 조건에 만족하도록 헬륨 고압측과 헬륨 저압측에 cryogenic adsorber를 설치하여 가스 내 불순물을 제거하는 가스순도제어 작업을 수행해야 한다. cryogenic adsorber를 사용하기 위해서는 장치 내의 불순 가스를 공정진공도(1.33 X $10^{-3}$ mbar) 이하로 진공배기하는 작업이 매우 중요하다. 이는 계통의 헬륨가스가 오염되지 않도록 하는 것으로 cryogenic adsorber 내에는 액체질소를 충전하여 액체질소 온도에 노출된 활성탄층을 헬륨가스가 흐르면서 수분, 질소, 탄화수소류 및 오일 등이 제거된다. 이 논문에서는 헬륨냉동계통의 가스 순도 제어 작업을 통해 헬륨가스의 순도가 요구조건 이하로 만족하며, 팽창 터빈의 운전에 영향을 미치지 않음을 기술하고자 한다.

• Journal of the Korean Institute of Gas
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• v.15 no.3
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• pp.53-57
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• 2011

The present study has been carried out to analyze the flow characteristics of a heat recovery steam generator with the change of inlet flow conditions by using numerical flow analysis. The inlet of HRSG corresponds the outlet of gas turbine exit and the flow after gas turbine has strong swirl flow and turbulence. The inlet flow condition of HRSG should be included the exit flow characteristics of gas turbine. The present numerical analysis adopted the flow analysis result of gas turbine exit flow as a inlet flow condition of HRSG analysis. The computational flow analysis result of gas turbine exit shows that the maximum axial velocity appears near circular duct wall and the maximum turbulent kinetic energy and dissipation rate exist relatively higher gradient region of axial velocity. The comparison of flow analysis will be executed with change of inlet turbulent flow condition. The first case is using the inlet turbulent properties from the result of computational analysis of gas turbine exit flow, and the second case is using the assumed turbulent intensity with the magnitude proportional to the velocity magnitude and length scale. The computational results of flow characteristics for two cases show great difference especially in the velocity field and turbulent properties. The main conclusion of the present study is that the flow inlet condition of HRSG should be included the turbulent properties for the accurate computational result of flow analysis.

• The KSFM Journal of Fluid Machinery
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• v.2 no.1 s.2
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• pp.103-107
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• 1999

Transient flow inside a hollow shaft of a Gas Turbine engine during sudden engine stop may result in non uniform heat transfer coefficients in the shaft due to flow instability similar to steady Taylor vortex, which may decrease the lifetime of the shaft. In the present study, transient Taylor vortex phenomena inside a suddenly stopped hollow shaft are studied analytically. Flow visualization is also performed to study the shape and onset time of Taylor Vortices for various initial rotational speed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.289-292
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• 2005

Because of accumulation of operation time, the performance of main components(compressor, combustor, turbine, etc.) come to be deteriorated in gas-turbine engine. So, high reliability and minimun of expense are important problem for engine manufacturer and user in operation of gas-turbine engine. In this study, the diagnostic code of the engine performance using the thermodynamic sensitivity between the sensed parameters and the health parameters has been developed without an application of the commercial program. The single performance deterioration of the turbo-shaft engine has been estimated with this code.

• 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.