• The KSFM Journal of Fluid Machinery
• /
• 제15권2호
• /
• pp.12-19
• /
• 2012

This study presents unsteady and unstable characteristics of three stage transonic axial compressor, developed by Korea Aerospace Research Institute. As approaching to the unstable operating region at the 103% design speed of the compressor, a modal type stall precursor appears in front of highly loaded 3rd rotor row at first, and it propagates to the upstream. On the contrary, actual stall cell initiates from the stall precursor in front of the 1st rotor row, and it propagates to the downstream of the compressor. After the stall region reached the 3rd stage and stall cell rotates circumferentially about 360 deg, it develops to one dimensional compressor surge mode. It shows a mild surge behaviour with 3~4 Hz frequency. From the test data, it can be suggested that there is a priority to give an optimum blade loading distributions to construct a multi stage transonic axial compressor stages either to secure more stable compressor operating ranges, or to maximize the compressor efficiency.

• Transactions of the Korean Society of Mechanical Engineers
• /
• 제16권1호
• /
• pp.77-86
• /
• 1992

This paper discusses the thermodynamic study on the suction cooling-steam injected gas turbine cycle. The aim of this study is to improve the thermal efficiency and the specific output by steam injection produced by the waste heat from the waste heat recovery boiler and by cooling compressor inlet air by an ammonia absorption-type suction cooling system. The operating region of this newly devised cycle depends upon the pinch point limit and the outlet temperature of refrigerator. The higher steam injection ratio and the lower the evaporating temperature of refrigerant allow the higher thermal efficiency and the specific output. The optimum pressure ratios and the steam injection ratios for the maximum thermal efficiency and the specific output can be found. It is evident that this cycle considered as one of the most effective methods which can obtain the higher thermal efficiency and the specific output comparing with the conventional simple cycle and steam injected gas turbine cycle.

• Journal of the Society of Naval Architects of Korea
• /
• 제50권6호
• /
• pp.450-457
• /
• 2013

For the design guide of a vessel operating in cold region, numerical analysis was carried out to evaluate the weather-tight door which installed the heating cables by using ANSYS 13.0 Transient Thermal. The numerical analysis was performed by considering Advection-Diffusion equation. This study based on the experimental results of 'A study on Anti-Icing Technique for Weather-Tight Door of Ice-Strengthened Vessels'(Jeong, et al., 2011a) in KIOST. For validation of the numerical analysis results, the cold chamber experimental data measured by the heat sensors in certain location of the weather-tight door was used. The external environmental temperature which varies from $5^{\circ}C$ to $-55^{\circ}C$ was considered in numerical analysis. Also three different heating cables which have the heat capacity of 33W/m, 45W/m and 66W/m were adapted for the design parameters to be the most efficient and guidelines for anti-icing design of the weather tight door.

• Transactions of the Korean Society of Mechanical Engineers
• /
• 제14권2호
• /
• pp.358-366
• /
• 1990

As a basic study to clarify the scoring resistance in lubricated sliding contact, the temperature rise on frictional surface was analyzed by theoretical method and the effects of various factors on the temperature rise were examined. On the basic of the results obtained theoretically, the practical equations to calculate the maximum average temperature of the contact surface were proposed which are applicable to sliding contact. Then, the effects of sliding velocity and oil temperature on the seizure behavior, and the relation between seizure and temperature rise were investigated. The following conclusions are deduced : The maximum average temperature rise and the other bulk temperature. The former is affected by the size of heat supply region and the sliding velocity, the latter is affected by heat transfer coefficient. Without regard to the operating condition such as sliding velocity, oil temperature and operating time at each load-step, the maximum average temperature just before seizure is nearly constant except in the region of lower velocity. Consequently, the maximum average temperature of the contact surface in boundary lubrication is a useful criterion to predict the scoring of sliding contact.

• Journal of the Society of Naval Architects of Korea
• /
• 제52권4호
• /
• pp.323-329
• /
• 2015

For the design guide of a vessel operating in cold region, numerical analysis was carried out to evaluate the ice class louver which installed the heating cables by using ANSYS 13.0 CFX. The numerical analysis was performed by considering Unsteady Reynolds Averaged Navier Stokes (RANS) equation. This study based on the experimental results of ‘The Cryogenic Performance Evaluation for the Excellent De-icing Ice Class Louver’ in KRISO. For validation of the numerical analysis results, the cold chamber experimental data measured by the heat sensors in certain location of the ice class louver was used. The external environmental temperature which varies from 0℃ to –30℃ was considered in numerical analysis. Also the design guide for optimum de-icing presented through heating cable power capacity(33 W/m, 45 W/m, 66 W/m), location of the heating cable(front, center, behind on the blade) and relative velocity(1 m/s, 4 m/s, 7 m/s).

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2008년도 춘계학술대회논문집
• /
• pp.652-655
• /
• 2008

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-${\varepsilon}$ model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(k-${\varepsilon}$) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

• Transactions of the Korean Society of Automotive Engineers
• /
• 제14권5호
• /
• pp.25-31
• /
• 2006

Controlled Auto Ignition(CAI) combustion has great potential in achieving significant increase in engine efficiency, while simultaneously reducing exhaust emissions. The process itself involves the auto ignition and subsequent simultaneous combustion of a premixed charge. In this study, NVO(Negative Valve Overlap) system was applied to a CAI engine in order to use residual gas. The fuel was injected directly to the cylinder under the high temperature condition resulting from heating the intake port to initiate CAI combustion. This paper introduced the valve timing strategy and experimental set-up. From this study, the effect of engine speed and valve timing on CAI combustion and exhaust emissions was clarified. In addition, stratified charge method was used to extend CAI operating region.

• Nuclear Engineering and Technology
• /
• 제56권8호
• /
• pp.3076-3083
• /
• 2024

In this work, single photon avalanche diodes (SPADs) were fabricated using the standard 180 nm complementary metal-oxide semiconductor process. Their small size of 15-16 µ m and low operating voltage made it possible to easily integrate them with readout circuits for compact on-chip sensors, particularly those used in the radiation sensor network of a nuclear plant. Four architectures were proposed for the SPADs, with a shallow trench isolation (STI) guard ring and different depletion regions designed to demonstrate the main performance parameters in each experimental configuration. The wide absorption region structure with PSD and a deep N-well could achieve a uniform electric field, resulting in a stable dark count rate (DCR). Additionally, the STI guard ring was implanted to mitigate the premature edge breakdown. A breakdown voltage was achieved for a low operating voltage of 10.75 V. The DCR results showed 286.3 Hz per ㎛² at an excess voltage of 0.04 V. A photon detection probability of 21.48% was obtained at 405 nm.

• Journal of the Korean Institute of Rural Architecture
• /
• 제15권1호
• /
• pp.47-56
• /
• 2013

As architecture has a role of vessel that contains human life, architecture of museums in a region must be a vessel that contains identity of the region. Jeju Province possesses excellent natural landscape acknowledged by the world. As such, architectural design of museums in Jeju region, differentiated in terms of natural, humanistic and cultural characteristics from other regions, must include identity of Jeju. Jeju has established and is operating so many museums with different themes that it is referred to as the heaven of museums. In addition, museums as cultural facilities must be the measure of cultural level representing regional identity and perform the role of advance guard that leads architectural culture of the region. Also, such excellent architectural asset is an important landscape element that increases value of the region. Based on Landscape Management Guideline established in 2009 by Jeju Special Self-governing Province under such critical mind, this study will support design problems and improvements of museums through case study and analysis on design characteristics of national and private museums in Jeju. Accordingly, the purpose of this study is to provide basic data to be pursued by future museums that contain identity of Jeju, based upon the results of analysis described above.

• Journal of Chest Surgery
• /
• 제48권4호
• /
• pp.281-284
• /
• 2015

We present the case of a 38-year-old woman admitted to our outpatient clinic with accelerating back pain and fatigue following a kick to her back by her husband. Upon arrival, we detected ST segment elevation in the D1, aVL, and V2 leads and accelerated idioventricular rhythm. She had pallor and hypotension consistent with cardiogenic shock. We immediately performed coronary angiography and found a long dissection starting from the mid-left main coronary artery and progressing into the mid-left anterior descending (LAD) and circumflex arteries. She was then transferred to the operating room for surgery. A saphenous vein was grafted to the distal LAD. Since the patient was hypotensive under noradrenaline and dopamine infusions, she was transferred to the cardiovascular surgery intensive care unit on an extracorporeal membrane oxygenator and intra-aortic balloon pump. During follow-up, her blood pressure remained low, at approximately 60/40 mmHg, despite aggressive inotropic and mechanical support. On the second postoperative day, asystole and cardiovascular arrest quickly developed, and despite aggressive cardiopulmonary resuscitation, she died.