• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 강연회 및 연구개발 발표회 논문집
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• pp.11-28
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• 1998

Crack initiation and propagation of blades is a serious matter in turbomachinery. Outages are common due to these problems that occur during the service of the machine resulting in a huge loss of revenue. Once in a while, the problems become serious and cause major shutdowns which can in some cases result in the loss of the whole machine in a catastrophic manner. In this presentation, we will discuss the crack initiation studies of a hydraulic machine runner blade by local stress strain approach and crack propagation at the root of a low pressure stage steam turbine blade by means of stress intensity factor approach. In both the cases, we will show how the present day technologies can predict actual field observations.

• 한국유체기계학회 논문집
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• 제14권6호
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• pp.76-84
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• 2011

The effect of inlet velocity profile on the heat transfer coefficient in a rotating smooth channel was investigated experimentally. Three simulated inlet flow conditions of fully developed, uniform, and distorted inlet conditions were tested. The Reynolds number based on the channel hydraulic diameter was ranged from 10,000 to 30,000 and the transient liquid crystal technique was used to measure the distribution of the heat transfer coefficient in the rotating channel. Results showed that the overall heat transfer coefficient increased as the Reynolds number increased. Also, the distribution of the heat transfer coefficient was strongly affected by the inlet flow condition. Generally, the fully developed flow simulated condition showed the highest heat transfer coefficient.

• International Journal of Fluid Machinery and Systems
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• 제10권3호
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• pp.264-273
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• 2017

In order to be able to predict the maximum Annual Energy Production (AEP) for tidal power plants, an AEP optimization tool based on Evolutionary Algorithms was developed by ANDRITZ HYDRO. This tool can simulate all operating modes of the units (bi-directional turbine, pump and sluicing mode) and provide the optimal plant operation that maximizes the AEP to the control system. For the Swansea Bay Tidal Power Plant, the AEP optimization evaluated all different hydraulic and operating concepts and defined the optimal concept that led to a significant AEP increase. A comparison between the optimal plant operation provided by the AEP optimization and the full load operating strategy is presented in the paper, highlighting the advantage of the method in providing the maximum AEP.

• 에너지공학
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• 제9권1호
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• pp.47-53
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• 2000

This paper is to propose the concept and performance of a gravity engine which could extract energy from sea or river as a clean. renewable and sustainable power. the vertical motion of the buoyancy cylinder of the present gravity engine is converted to the mechanical work directly without any hydraulic loss. The positive net energy between the imposed and harnessed one is achieved by the specific operating procedure. The detailed derivation of the energy balance is made based on the first principle of thermodynamics. The calculation demonstrates that the present gravity engine could harness more energy than the conventional turbine system in the same basin area because of the relatively high efficiency in the energy conversion system and added mass from the buoyancy cylinder.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.101-112
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• 2015

Renewable energy resources play an important part in the world's future. Renewable energy sources have the following components: biomass, geothermal, solar thermal, directs solar, wind, tidal and hydropower. Hydropower is still the most efficient way to generate electricity worldwide. Hydropower projects can contribute as a cheap energy source, as well to encourage the development of small industries across a wide range of new technology; furthermore hydropower systems use the energy in flowing and falling water to produce electricity or mechanical energy. Hydropower systems are classified as large, medium, small, mini and micro according to their installed power generation capacity, as do the following components: water turbines, control mechanisms and electrical transmissions. In this article a review of small hydropower systems has been done on the principles surrounding the fundamentals of hydraulic engineering, the fundamentals of hydrology, identification of sites and economic analysis.

• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.362-369
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• 2016

The shock-free inflow criterion applied in the development of two-dimensional cascade for turbomachinery design. The developed cascade analysis with potential flow calculation through a panel method has been used to determine the shock-free inflow condition. The combination between cascade analysis and PSO (particle swarm optimization) algorithm provides an opportunity to develop a diagram of a two-dimensional parameter cascade at various airfoil shapes. Analytical equations have been derived from the diagram that will facilitate the turbomachinery designer in applying the shock-free inflow criterion on their developed cascade. This method has been used to develop the very low head axial hydraulic turbine and provides excellent results of numerical and actual prototype performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.184-186
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• 2007

절연물의 열화가 진행되면 최초로 1선 지락사고가 발생할 가능성이 많고 1선 지락사고는 2선 지락 및 단락사고로 파급되어 설비에 심각한 손상으로 이어지게 된다. 따라서, 1선지 락 사고에 대한 완전한 보호방식의 적용은 설비 신뢰성 증대라는 측면에서 매우 중요한 사항이라고 판단된다. 이에 시화호조력 발전소에 설치될 수차발전기는 고정자권선의 지락사고에 대한 100%보호방식을 적용하였으며 이 설계사례를 토대로 실제적으로 적용가능한 발전기 고정자권선의 지락보호증대방식을 공유코자 한다.

• 전기학회논문지
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• 제68권4호
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• pp.523-531
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• 2019

This paper deals with a wound-field synchronous machines(WFSM), with an electromagnet on its salient rotor, as an alternative to a permanent magnet in the rotor. We then examine the power performance characteristics, loss characteristics, V-curves and large short-circuit ratios for a large-scale synchronous generator, considering the leading and lagging operations, based on the finite-element method. We predict the performance of a 100MVA-class generator based on the operating range for a constant short-circuit ratio. At the last, We compared with the electromagnetic characteristics of three model according to number of slots.

• Nuclear Engineering and Technology
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• 제18권2호
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• pp.97-106
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• 1986

1981년 6일 9일 원자력 1호기에서 발생한 77.5% 출력상태에서의 외부전원상실사고를 열, 수력학적최적계산용 코드인 RELAP5/MODl/NSC를 사용하여 모의하였으며 해석결과는 발전소 실측자료와 잘 일치하였다. 원자로 냉각재펌프의 트립에 따른 flow coastdown후에 hot-cold leg온도차에 의하여 자연순환 유동이 형성됨이 확인되었으며 실측자료와 잘 일치하여 이와 관련된 전산코드의 열수력학 적모델의 타당성을 입증할 수 있었다. 또한 위의 사고전개가 정상운전상태인 전출력(100%)에서 재발하였을 경우를 가정하여 해석하였다. 이러한 해석을 통하여 보조급수의 공급과 더불어 증기발생기 PORV의 적절한 작동으로 원자력 1호기 노심잔열을 제거하여 안전성에 문제점을 야기하지 않음을 입증하였다. 최적 계산방법에 의한 사고해석에서는 turbine stop valve 작동시간, 증기 발생기 PORV 설정치 등 non-safety 관련요소들의 특성에 대한 정화한 모의가 필수적이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.22-29
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• 2001

The present study investigates the effects of various rib arrangements and rotating on heat/mass transfer in the cooling passage of gas turbine blades. The cooling passage has very complex flow structure, because of the rib turbulator and rotating effect. Experiments and numerical calculation are conducted to investigate the complex flow structures and heat transfer characteristics; the numerical computation is performed using a commercial code, FLUENT ver.5, to calculate the flow structures and the experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. For the rotating duct tests, the test duct, which is the cross section of is $20mm\times40mm$ (the hydraulic diameter, $D_h$, of 26.7 mm, has two-pass with $180^{\circ}$ turning and the rectangular ribs on the wall. The rib angle of attack is $70^{\circ}$ and the maximum radius of rotation is $21.63D_h$. The partition wall has 10 mm thickness, which is 0.5 times to the channel width, and the distance between the tip of the partition wall and the outer wall of the turning region is 26.7 mm $(1D_h)$. The turning effect of duct flow makes the very complex flow structure including Dean type vortex and high turbulence, so that the heat/mass transfer increases in the turning region and at the entrance of the second pass. The Coriolis effect deflects the flow to the trailing surface, resulting in enhancement of the heat/mass transfer on the trailing surface and reduction on the leading surface in the first pass. However, the opposite phenomena are observed in the second pass. The each rib arrangement makes different secondary flow patterns. The complex heat/mass transfer characteristics are observed by the combined effects of the rib arrangements, duct rotation and flow turning.