• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.473-480
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• 2005

Clocking effects of a stator on the performance and internal flow in an UTRC 1.5 stage axial turbine are investigated using a three-dimensional unsteady flow simulation. Six relative positions of two rows of stator are investigated by positioning the second stator being clocked in a step of 1/6 pitch. The relative efficiency benefit of about 1% is obtained depending on the clocking positions. However, internal flows have some different characteristics from that in the previous study at the best and worst efficiency positions, since be first stator wake is mixed out with the rotor wake before arriving at the leading edge of the second stator. Instead of the first stator wake, it is found that the wake interaction of the first stator and rotor has a important role on a relative efficiency variation at each clocking position. The time-averaged local efficiency along the span at the maximum efficiency is more uniform than that at the minimum efficiency. That is, the spanwise efficiency distribution at the minimum efficiency has larger values in mid-span but smaller values near the hub and casing in comparison to those at the maximum efficiency. Moreover, the difference between maximum and minimum instantaneous efficiencies during one period is found to be smaller at the maximum efficiency than at the minimum efficiency.

• 열병합발전
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• 통권36호
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• pp.16-21
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• 2003

For many years, T/G Supplier has constructed a number of thermal power plants and researched to improve the performance and the reliability of steam turbine, which are achieved by advances in design and materials technology. In recent, interest is renewed in advance steam condition as means of improving economy of thermal power plant and reducing environmental pollution. Improvements in the maximum power have been driven by the development of advanced rotor and bucket material and longer last stage bucket. Improvements in efficiency have been brought through advance in mechanical efficiency and thermodynamic efficiency. This paper describes a number of new steam path design features introduced to the steam turbine product. And also this paper describes new design technologies' development, new technologies' trend and technologies' development for ultra-super critical steam turbine.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2174-2179
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• 2003

For many years, T/G Supplier has constructed a number of thermal power plants and researched to improve the performance and the reliability of steam turbine, which are achieved by advances in design and materials technology. In recent, interest is renewed in advanced steam condition as means of improving economy of thermal power plant and reducing environmental pollution. Improvements in the maximum power have been driven by the development of advanced rotor and bucket material and longer last stage bucket. Improvements in efficiency have been brought through advances in mechanical efficiency and thermodynamic efficiency. This paper describes a number of new steam path design features introduced to the steam turbine product. And also this paper describes new design technologies' development, new technologies' trend and technologies' development for ultra-super critical steam turbine.

• 산업경영시스템학회지
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• 제18권36호
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• pp.297-306
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• 1995

An automatic transfer line consists of several stages(groups of stations) in series into one system by a common transfer mechanism and a common control system. In this system losses of the efficiency are evidenced in periods where a stage is forcod down- starved or blocked. The efficiency of an automatic transfer line can be improved by providing buffer storages between a stage or the length of line common senses there are several critical factors, system configurations relative position, and buffer capacity allocations in automatic transfer line are considered with a point of view production rates, average stock, and mean delay. The propose of this paper is to provide the robust designs by Taguchi method which improve the efficiency of four-stage transfer line.

• 한국실내디자인학회논문집
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• 제21권5호
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• pp.106-113
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• 2012

A study on techniques to evaluate auditorium assignment visible efficiency using three-dimensional simulation. The most important thing to be considered is to ensure the visibility to the podium upon assigning auditorium of venues, classrooms or seminar rooms. However, since there are so many variables to be considered such as the form of the stage, the area and height of the stage, size of screen, and the distance and angle of the auditorium from the podium, the methods to assign auditorium are staying at the level of basic for a long time. Thus, in this study, we proposed simulation methodology to quantitatively evaluate the three-dimensional visible efficiency based on Visual Graph Analysis (VGA) theory. After analytical methodology manufactures application, it sets examples of visibility depending on location of screen, visibility depending on degree of height difference and visibility about three-dimensional Mass Zoning like a stage and verifies the efficacy. In addition, based on results, visibility expectation curve is drawn and the method to calculate the stepped height depending on necessary visibility is proposed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.100-102
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• 2008

As Utility interactive fuel cell systems are widely used, it is required for each power conditioning system(PCS) to have higher generating performance and more stable connecting characteristics. This study is focused to minimization of power losses and hence higher efficiency related to the new half bridge type 3-stage utility interactive PCS topology. The loss factor of half-bridge converter becomes only 1.2[%] under the rated load, and hence total efficiency is maintained to be higher as 91[%].

• 산업경영시스템학회지
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• 제44권3호
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• pp.248-261
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• 2021

Scientific and technological performances (e.g., patents and publications) made through R&D play a pivotal role for national economic growth. National governments encourage academia-industry cooperation and thereby pursue continuous development of science technology and innovation. Increasing R&D-related investments and manpower are crucial for national industrial development, but evidence of poor performance in business performance, efficiency, and effectiveness has recently been found in Korea. This study evaluates performance efficiency of the 6T sector (Information Technology, Bio Technology, Nano Technology, Space Technology, Environment Technology, Culture Technology), which is considered a high-potential promising industry for the next generation growth and currently occupies two thirds of the national R&D projects. The study measures the relative efficiency of R&D in a comparative perspective by employing the Data Envelopment Analysis (DEA) method. The result reveals overall low efficiency in basic R&D (0.2112), applied R&D (0.2083), development R&D (0.2638), and others (0.0641), confirming that economic performance and efficiency were relatively poor compared to production efficiency. Efficient R&D needs policy makers to create strategies that can increase overall efficiency by improving productivity performance and quality while increasing economic performance.

• 무역학회지
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• 제48권1호
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• pp.215-241
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• 2023

항만 간 경쟁이 심화되면서 항만효율성은 더욱 중요하게 인식되고 있다. 항만효율성 개선을 통하여 항만의 지속 가능한 개발을 촉진함과 동시에 지역 및 국가 경제성장을 도모하는 것은 항만운영자뿐만 아니라 지방 및 정부의 주된 관심사이다. 본 연구는 중국의 황금내륙수로인 양쯔강 상의 내륙항만들의 경쟁이 치열해지고 있는 상황에서 2010년부터 2017년까지의 패널자료를 이용하여 장강변 14개 주요 내륙항의 효율성을 분석하고 시간에 따른 항만 효율성의 변화를 살펴보고자 하였다. 동시에 14개 내륙항구를 양쯔강 중류, 상류, 하류 항만군으로 나누어 유역별 항만효율성 수준의 차이를 비교 검토하였다. 특히 본 연구를 수행하기 위해 3단계 DEA 분석 방법을 적용하여 효율성 평가에 영향을 미칠 수 있는 환경적 요인과 통계적 노이즈의 영향을 최대한 배제하여 항만 자체의 순수 상대효율성을 평가하였다. 분석결과, 1단계 효율 평가 결과와 3단계 효율 평가 결과 포트의 효율 값에 뚜렷한 차이가 있음을 확인하였고, 구체적인 결과를 해석과 함께 본문에서 제시하였다. 또한 하류항만들의 효율성이 중·상류 항만에 비해 상대적으로 높은 효율성을 보이고 있음을 알 수 있었다.

• 동력기계공학회지
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• 제12권4호
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• pp.57-63
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• 2008

The last stage blade of the low pressure steam turbine remarkably affects turbine plant performance and availability Turbine manufacturers are continuously developing the low pressure last stage blades using the latest technology in order to achieve higher reliability and improved efficiency. They tend to lengthen the last stage blade and apply shrouds at the blades to enhance turbine efficiency. The long blades increase the blade tip circumferential speed and water droplet erosion at shroud is anticipated. Parts of integral shrouds of the last stage 40 inch blades were cracked and liberated recently in a combined cycle power plant. In order to analyze the root cause of the last stage blades shroud cracks, we investigated operational history, heat balance diagram, damaged blades shape, fractured surface of damaged blades, microstructure examination and design data, etc. Root causes were analyzed as the improper material and design of the blade. Notches induced by erosion and blade shroud were failed eventually by high cycle fatigue. This paper describes the root cause analysis and countermeasures for the steam turbine last stage blade shroud cracks of the combined cycle power plant.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.119-124
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• 2008

Recently, focus has been drawn on natural refrigerants due to increasing concern on global warming. As a consequence, CO2 systems such as a heat pump water heater using CO2 as a refrigerant are rapidly growing on the market. Currently, rolling piston rotary compressors are widely used for CO2 heating and/or refrigeration systems. There are several ways of realizing gas compression structure. They are single stage compression with single cylinder, single stage compression with two cylinders, and two stage compression with two cylinders. In this paper, computer simulation program which was validated for a single stage rotary compressor with one cylinder has been extended for a single stage, two cylinder rotary type. Numerical investigation has been made on optimal design for the cylinder configuration using the extended simulation program. For a single stage two cylinder rotary compressor having a displacement volume of 4 cc for each cylinder, compressor efficiency has been found to be maximum when the cylinder radius and height are 31mm and 10mm, respectively.