• The KSFM Journal of Fluid Machinery
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• v.19 no.1
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• pp.24-30
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• 2016

In this study, a 2W micro-gas turbine engine was designed using micro-electro-mechanical systems (MEMS) technology, and experimental investigations of its potential under actual combustion conditions were performed. A micro-gas turbine (MGT) contains a turbo-charger, combustor, and generator. Compressor and turbine blades, and generator coil were manufactured using MEMS technology. The shaft was supported by a precision computer numerical control (CNC) machined static air bearing, and a permanent magnet was attached to the end of the shaft for generation. A heat transfer analysis found that the cooling effect of the air bearing and compressor was sufficient to cover the combustor's high temperature, which was verified in an actual experiment. The generator performance test showed that it can generate 2W at design rotational speed. Prototype micro-gas turbine generated maximum 1 mW electric power and lasted up to 15 minutes.

• Tribology and Lubricants
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• v.34 no.1
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• pp.9-15
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• 2018

Modern high-performance automotive turbochargers (TCs) implement ceramic hybrid angular contact ball bearings in series with squeeze film dampers (SFDs) to enhance transient responses, thereby reducing the overall emission levels. The current study predicts the rotordynamic responses of the commercial automotive TCs (compressor wheel diameter = ~53 mm, turbine wheel diameter = ~43 mm, and shaft diameter at the bearing locations = ~7 mm) supported on ball bearings and SFDs for various design parameters of SFDs, including radial clearance, axial length, lubricant viscosity, and rotor imbalance conditions (i.e., amplitudes and phase angles) while increasing rotor speed up to 150 krpm. This study validates the predictive rotor finite element model against measurements of mass, polar and transverse moments of inertia, and free-free mode natural frequencies and mode shapes. A nonlinear rotordynamic model integrates nonlinear force coefficients of SFDs to calculate the transient responses of the TC rotor-bearing system. The predicted results show that SFD radial clearances, as well as phase angles of rotor imbalances, have the paramount effect on the dynamic responses of TC shaft motions.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.100-110
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• 2008

It is not easy to monitor and identify all engine faults and conditions using conventional fault detection approaches like the GPA (Gas Path Analysis) method due to the nature and complexity of the faults. This study therefore focuses on a model based diagnostic method using Neural Network algorithms proposed for fault detection on a turbo shaft engine (PW 206C) selected as the power plant for a tilt rotor type unmanned aerial vehicle (Smart UAV). The model based diagnosis should be performed by a precise performance model. However component maps for the performance model were not provided by the engine manufacturer. Therefore they were generated by a new component map generation method, namely hybrid method using system identification and genetic algorithms that identifies inversely component characteristics from limited performance deck data provided by the engine manufacturer. Performance simulations at different operating conditions were performed on the PW206C turbo shaft engine using SIMULINK. In order to train the proposed BPNN (Back Propagation Neural Network), performance data sets obtained from performance analysis results using various implanted component degradations were used. The trained NN system could reasonably detect the faulted components including the fault pattern and quantity of the study engine at various operating conditions.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.33 no.12
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• pp.105-112
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• 2017

Through various media, damage of both smoking and second-hand smoking has been recognized, and brought global scale of interest in antismoking. In Korea, government has tightened regulations of smoking in non-smoking zone since December, 1980, and after National Health Promotion Act in 1995, non-smoking zone has been gradually expanded. On the other hand, there were law suits to find those regulation towards smokers are either unconstitutional or not for 4 times. In this current state, people need smoking area to prevent second-hand smoking and to consider smokers in multi-unit dwelling. Main purpose of this research is to plan smoking spaces based on various typology of multi-dwelling plan for protection of both smokers and non-smokers' right. The research group collected and analyzed the smoking behaviors in various multi-unit dwelling types such as flat type, tower type, hybrid type and others. Based on those data, the group found three phenomena. First, there are internal regulations in multi-unit dwelling to make non-smoking zone based on National Health Promotion Act and resident representative meeting decision. Second, main smoking activities are occurring at major traffic line and entrances. Third, smoking inside of multi-unit dwelling complex causes second-hand smoking to residents live in $1^{st}$ floor and when they enter. Therefore, one can achieve both smokers' and non-smokers' protection of right by creating a designated smoking space near main entrances of multi-unit dwelling complex to consider smokers' and prevents second-hand smoking by using shaft space, which is in core space, to ventilate tobacco smoke through roof.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1339-1342
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• 2005

This paper presents a simple AC-DC power conditioner for a squirell-cage induction generator(IG) operating under variable shaft speeds. The necessary reactive power for the IG system is supplied by means of a capacitor bank and a voltage-source PWM converter. Using a capacitor bank to transfer the reactive power to the IG under the rated speed and no-load conditions starts the IG operation and reduces the PWM power converter size. A simple control compensating for changes in the electrical loads as well as the variation in speed was developed to regulate the voltages of the IG system by controlling the rotor flux through its reactive and active currents control implementation. This proposed power conditioning scheme can be used efficiently as a wind power generation system where the output voltage of the IG is maintained constant voltage despite the variable frequency and the DC bus voltage of the PWM converter can be used for either DC applications such as battery charging or AC power applications with 60/50 Hz by connecting a stand alone inverter. The experimental and simulated operating performance results of a 5 kW IG scheme at various speeds and leads are presented.

• Journal of Hydrogen and New Energy
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• v.26 no.1
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• pp.79-87
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• 2015

In a gas engine, the exhaust and the engine cooling water are generated. The engine cooling water temperature is $100^{\circ}C$ and the exhaust temperature is $500^{\circ}C$. The amount of heat of engine cooling water is 43 kW and the amount of heat of exhaust is 21 kW. Eight different hybrid organic Rankine cycle (ORC) system configurations which considering different amount and temperature of waste heat are proposed for two gas engine tri-generation system and are thermodynamically analyzed. Simple system which concentrating two different waste heat on relatively low temperature engine cooling water shows highest thermal efficiency of 7.84% with pressure ratio of 3.67 and shaft power of 5.17 kW.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1796-1807
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• 2017

The domestic warship propulsion system is at the stage of a hybrid propulsion system changing from a mechanical propulsion system and the propulsion system becomes complicated so it is expected that the function of ECS(Engineering Control System) that controls and monitors the warship propulsion system becomes important. Recently the development of ECS has progressed domestically, so that verification of reliability and stability is required in the process of ECS development. The simulator to be proposed is composed of HILS, it can be divided into a shaft-line dynamics model of the simulating power transmission, a controller model of the simulating the control of the equipment, and a communication model communicating with the ECS. In this paper, we developed simulator for ECS verification for CODLOG hybrid propulsion system, set scenario, and conducted simulation.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.307-320
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• 2013

This paper proposes a new hybrid support structure by the driven piles which removes disadvantages of the existing type of support structure for offshore wind turbines. The hybrid type of support structure is combined with concrete cone and steel shaft, and is supported not only by gravity type foundations but also by driven piles. For three dimensional analysis of the huge and thick concrete structure, a solid-shell element that is capable of exact modeling and node interpolations of stresses is developed. By applying wave theory of stream function and solid-shell element in XSEA simulation software for fixed offshore wind turbines, a quasi-static analysis and natural frequency analysis of proposed support structure are performed with the environmental condition on Southwest Coast in Korea. In the result, lateral displacement is not exceed allowable displacement and a superiority of dynamic behavior of new hybrid support structure is validated by natural frequency analysis. Consequently, the hybrid support structure presented in this study has a structural stability enough to be applied on real-site condition in Korea. The optimized structures based on the preliminary design concept resulted in an efficient structure, which reasonably reduces fabrication costs.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.553-557
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• 1994

We propose a design method that uses H$_{\infty}$ optimization method to suppress oscillation of a shaft between motor and load for high precision (0.001 % of reference input) position controls. PI speed control loop was introduced as a minor loop. Standard problem is used for the modeling of the system and Glover-Doyle's algorithm is used for the optimization in the H$_{\infty}$ space. Friction is considered to be an important factor that makes it difficult for the system to reach steady state in short time. In this paper, we propose a hybrid controller that includes PI speed feedback loop, which is expected to have a role to reject torque disturbance like friction.n.n.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.845-847
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• 2015

A suspending force control based on fuzzy logic control is proposed to apply on a novel hybrid bearingless switched reluctance motor(BLSRM) which has separated torque and suspending force pole. Due to the unique structure, the suspending force control system can be easily decoupled from torque control system. In this paper, two fuzzy controller targeted at x-axis direction and y-axis direction are adopted to maintain the shaft at center position, which is very necessary for stable operation of BLSRM. By replacing the traditional PI block with modified fuzzy logic controller, the suspending system can behave a good performance, and the proposed scheme can be verified by simulation results.