• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1738-1743
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• 2004

Turbo-pump system, an essential component of liquid rockets and induced weapons, adopts a partial admission axial turbine which drives pump. And the turbine of a turbo-pump system is usually operated at supersonic condition due to its high loading chracteristics. Therefore, reseaches about flow and performance characteristics of a partial admission supersonic turbine must be preceeded to progress the aerospace and defense industries as well as the development of turbo-pump systems. In this study, flow characterisitics within blades of the partial admission supersonic turbine are numerically investigated by using Fine Turbo, a commercial CFD Code. Before performing the numercial analyses, to verify accuracy of the numerical result computed by Fine Turbo, I performed the comparison between the numerical results with J.J.Cho' experimental results. It is found that the numerical results show good agreement with the experimental results. Computations about the partial admission supersonic turbine have been performed to investigate flow characteristics including shock patterns. It is also found that the flow and performance of partial admission supersonic turbine are largely depend on shocks ocurred in the nozzle and at the leading edge of blades, expansion or compression at exit of nozzle and separations occurred in passage.

• 소성∙가공
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• 제25권6호
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• pp.379-389
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• 2016

As a stator for steam turbine diaphragm, hollow-type nozzle stator to substitute for conventional solid one is introduced in this study. This hollowed stator can be separated into two parts such as upper and lower plates with large and curved surface area. This study focuses on thick plate forming process for the upper plate of the hollow-partitioned nozzle stator. First, to reduce forming defects such as under-cut and localized thinning of the deformed plate, and to avoid tool interruption between forming punch and lower die, tool design including the position determination of forming surfaces is performed. Uni-axial tensile tests are carried out using SUS409L steel plate with initial thickness of 5.00mm, and plastic strain ratio (r-value) is also obtained. Due to the asymmetric curved configuration of the upper plate, it is hard to adopt a series of blank holder or draw-bead, so the initial plate during this thick plate forming experiences unstable and non-uniform contact. To easy this forming difficulty and find suitable tool geometry without sliding behavior of the workpiece in the die cavity, two geometric parameters with respect to each shoulder angle of the lower die and the upper punch are adopted. FE models with consideration of 21 combinations for the geometric parameters are built-up, and numerical simulations are performed. From the simulated and predicted results, it is shown that the geometric parameter combinations with ($30^{\circ}$, $90^{\circ}$) and ($45^{\circ}$, $90^{\circ}$) for the shoulder angle of the lower die and the upper punch are suitably applied to this upper plate forming of the hollow-partitioned nozzle stator used for the turbine diaphragm.

• 대한기계학회논문집B
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• 제41권10호
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• pp.685-691
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• 2017

증기 질량 유량의 변화에 따른 증기 터빈 노즐 단의 등엔트로피 노즐 효율을 계산하였다. 증기상태에 관한 압축성 Navier-Stokes 방정식을 기반으로 삼차원 수치해석 모델이 개발되었다. 두 가지의 삼차원 노즐 형상으로 압력, 온도, 속도, 마하수, 그리고 Markov 에너지 손실 계수가 계산되었다. 노즐 블레이드의 두께가 15mm에서 45mm로 증가함에 따라 최대 효율의 질량 유량은 0.9kg/s에서 1.6kg/s로 증가하였으며 최대 등엔트로피 효율은 각각 96.66%, 97.32%로 계산되었다. 질량 유량에 따른 등엔트로피 노즐 효율과 Markov 에너지 손실 계수를 계산하여 Markov 에너지 손실 계수와 등엔트로피 노즐 효율이 선형적 반비례 관계가 있음을 규명하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.99-103
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• 2003

캐스케이드 내 유동 해석은 터보 펌프의 설계 제작에 필수적인 요소이다. 그러나 기존의 무한 입구 경계 조건에서는 입구 유동의 초기 설정 경계치와 계산 후 입구 유동 경계치의 차이가 발생하여 원하는 입구 경계 조건에서의 유동 해석을 하지 못한다. 이에 본 연구에서는 Fine Turbo를 이용하여 입구 경계 조건으로 무한 경계 조건을 적용하였을 때 발생하는 문제점을 분석하였다. 그리고 무한 입구 경계 조건 대신 캐스케이드 앞에 수축·확산 노즐이나 직선 노즐을 위치시켜 전산 해석을 실시하여 그 특성을 비교, 검토하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.199-200
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• 2012

An experimental study on geometric optimization was conducted to develop a hybrid/dual swirl jet combustor for a micro-gas turbine. A hybrid concept indicating a combination of swirling jet partially premixed and premixed flames were adopted to achieve high flame stability as well as clean combustion. Location of pilot nozzle, angle and direction of swirl vane were varied as main parameters with a constant fuel flow rate for each nozzle. The results showed that the variation in location of pilot nozzle resulted in significant change in swirl intensity due to the change in flow area near burner exit, and thus, optimized nozzle location was determined on the basis of CO and NOx emissions under conditions of co-swirl flow and swirl $angle=30^{\circ}$. The increase in swirl angle (from $30^{\circ}$ to $45^{\circ}$) enhanced the emission performances, in particular, with a significant reduction of CO emission near lean-flammability limit. It was observed that the CO emission near lean-flammability limit was further reduced through the counter-swirl flow. However, there was not significant change in the NOx emission in the operating conditions (i.e. equivalence ratio of 0.6~0.7) between the co- and the counter-swirl flow.

• 한국연소학회지
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• 제7권2호
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• pp.7-14
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• 2002

The probability density functions (PDF) of temperature were measured by coherent anti-Stokes Raman Spectroscopy (CARS) in flames of gas turbine combustor sector rig of an aero-engine. The combustor was operated at simulated ground idle conditions with standard kerosene fuel. Temperature PDFs had been measured near fuel nozzle with change of rotation of a swirler and existence of a prefilmer. The characteristic features of temperature PDFs showed the variation of combustion configurations at four experimental conditions. Without a prefilmer, large recirculation of high temperature gas was expected in the co-flow condition and un vaporized fuel fragments were detected in the counter-flow condition. With a prefilmer, the enhanced mixing increased combustion intensity near fuel nozzle in the counter-flow condition and the flame was attached far from the fuel nozzle in the co-flow condition.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.594-599
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for different models. Observation of flow characteristics and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was used to simulate the waves and after obtaining the desired wave properties; the augmentation channel plus the front guide nozzle and rear chamber were integrated to the numerical wave tank. The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet. The inlet which was modeled as a plate wall moved sinusoidally with the general function, x=asin$\omega$t The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code ANSYS-CFX.

• 한국유체기계학회 논문집
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• 제16권6호
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• pp.32-39
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• 2013

In the present study, three-dimensional aerodynamic optimization of high pressure turbine nozzle for turbofan engine was performed. For this, Kriging surrogate model was built and refined iteratively by supplying additional experimental points until the surrogate model and CFX result has effective difference on objective function. When the surrogate model satisfied this reliability condition and developed enough, optimum point was investigated. Commercial program PIAnO was used for optimization process and evolutionary algorithm was used for searching optimum point. As a result, difference between estimated value from Kriging surrogate model and CFD result converges within 0.01% and the optimized nozzle shape has 0.83% improved aerodynamic efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.630-631
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• 소성∙가공
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• 제27권1호
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• pp.18-27
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• 2018

As one of the functional metal parts in steam turbine diaphragm assembly, the hollow-partitioned turbine nozzle (stator) has large and thick geometries, as well as an asymmetric configuration. Therefore it is hard to support a metal blank in the die cavity. To ease this situation and control posture and position of metal blank (workpiece), a blank support structure is newly introduced. The blank support structure is basically composed of enlarged arms from the blank, guide pins and linear bearings. It can help to control the intermediate blank without a critical sliding phenomenon. The operation mechanism of this blank support structure, during thick plate forming for the hollow-partitioned turbine nozzle stator, is first evaluated. A series of FEM-based numerical simulations, with respect to the width of the guide arm as geometric design parameters, are carried out to investigate its applicable range. As the results, it is observed the blank support structure for this thick plate forming can guide the workpiece to have stable posture during the plate forming process.