• Proceedings of the KIEE Conference
• /
• 2001.05a
• /
• pp.159-161
• /
• 2001

This study is for the pitch control of blade, used in most horizontal-axis wind turbine systems, to sustain the maximum power output supplied to grid. The control of a blade can be divided into a stall regulation and a pitch control methods. The stall regulation method using an aerodynamic stall is simple and cheap, but it suffers from fluctuation of the resulting power. Pitch control method is mechanically and mathematically complicated, but the control performance is better than that of the stall regulation method. In this paper 2.5MW MOD-2 wind turbine system is adopted to be controlled by a pitch controller with PI method. The simulation performed by MA TLAB will show the variation of frequency, generator output, and pitch angle.

• 유체기계공업학회:학술대회논문집
• /
• 2000.12a
• /
• pp.236-244
• /
• 2000

As the second part of the author's study, the aerodynamic blockage and the slip factor of 8 centrifugal compressor impellers are investigated, when the flow rate is changed from numerical stall to choke, using three-dimensional Navier-Stokes analysis results. Based on all the exit blockage distributions, an improved model equation with two adjusting coefficients is developed for the use in design processes with the agile engineering purpose. A popular expression of constant slip factors, the Wiesner's equation, cannot be applied in design processes when more accurate prediction is strongly required at design and off-design points. Slip factor variation is found to be also influenced by the blade loadings at midspan. When the flow rate is changed, a pattern of the slip factor variations is assumed to be a simple form which can be explained using midspan blade loading distributions.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.12
• /
• pp.1240-1245
• /
• 2009

The throughput characteristics of the cluster tool with dual blade robot are analyzed. Using equipment's cycle time chart of the equipment, simple analytic form of the throughput is derived. Then, several important throughput characteristics are analyzed by the throughput formula. First, utilization of the process chamber and the robot are maximized by assigning the equipment to the process whose processing time is near the critical process time. Second, rule for selecting optimal number of process chambers is suggested. It is desirable to select a single process chamber plus a single robot structure for relatively short time process and multi process chambers plus a single robot, namely cluster tool for relatively long time process. Third, throughput variation between equipments due to the wafer transfer time variation is analyzed, especially for the process whose processing time is less than critical process time. And the throughput and the wafer transfer time of the equipments in our fabrication line are measured and compared to the analysis.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.6
• /
• pp.549-556
• /
• 2014

This study proposes a parallel operation strategy for small wind turbine systems. A small wind turbine system consists of blade, permanent magnet synchronous generator, three-phase diode rectifier, DC/DC buck converter, and the battery load. This configuration has reliability, simple control algorithm, high efficiency, and low cost. In spite of these advantages, the system stops when unexpected failures occur. Possible failures can be divided into mechanical and electrical parts. The proposed strategy focuses on the failure of electrical parts, which is verified by numerical analysis through equivalent circuit and acquired general formula of small wind power generation systems. Simulation and experimental results prove its efficiency and usefulness.

• Journal of the Korean Society of Industry Convergence
• /
• v.7 no.1
• /
• pp.33-39
• /
• 2004

Viscous flows around a cooling tower fan with sweep are numerically investigated. The Navier-Stokes equations and the continuity equation are solved in the flow domain. The Reynolds stresses are modelled using the $\kappa-{\varepsilon}$ turbulence model. The governing equations are discretized with the Finite Volume Method. The pressure and the velocity are linked with the SIMPLE algorithme. Flow and pressure characteristics around the fan are investigated. The pressure sharply increases through the fan. Pressure variations on the pressure and suction sides of the fan are well represened in the calculations. The flow streamlines in the blade passage are nearly parallel to the blade.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.153-159
• /
• 2004

We have investigated the feasibility of using differential pressure(pressure drop) of gas turbine meter to diagnose turbine performance degradation caused by mechanical wearing damage and/or dirt buildup or erosion. If the differential pressure between the upstream piping and the throat of a turine meter can be correlated to meter flow rate over the operating range of the meter, then a relatively simple differential pressure measurement in the filed might be used to detect meter performance changes. To test this method, we have conducted two experimental simulation on Straightener Integrated Type(SIT) turbine meter. One is fur dirt buildup on turbine blade, the other is for eccentricity of the blade. Results show that this method provide a reliable measure of performance degradation and is useful maintenance indicator.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.54 no.6
• /
• pp.982-988
• /
• 2021

Gamma irradiation is one of the simple methods used to induce mutagenesis. Therefore, it is widely used for the development of breeding lineages of plants and algae. In this study, it was developed a new variety of Pyropia yezoensis using gamma irradiation. It was applied a dose of 1 kGy and named the developed mutant Py1k. The blade with width of the mutant was narrower and the blade length was longer than those of the wild type. To further investigate the mutant, it was analyzed the nutrient composition and antioxidant activity. In comparison to those in the wild type, it was found a higher amino acid composition and marginally increased antioxidant activity in Py1k. Based on these results, it was suggests that our protocol can be utilized to develop Pyropia species with improved nutritional quality through gamma irradiation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.6
• /
• pp.21-30
• /
• 2005

The aerodynamic analysis of helicopter rotor airfoils was performed to generate the basic data for selection and distribution of airfoils at the helicopter rotor blade preliminary design phase.10 airfoils were chosen among the existing rotor airfoils, and the tabulated aerodynamic coefficients which are proper for the aerodynamic analysis using blade element theory were generated. Considering analysis cost, the simple mathematical models were chosen before the wind tunnel test to generate the aerodynamic characteristic curves($C_{l},C_{m},C_{d}$) in full AoA range($-180^{o}\sim180^{o}$) including the reverse flow region. The essential data necessary to the generation of the complete curves were obtained by using the IBLM(Interactive Boundary Layer Method). The generated aerodynamic characteristic curves agree with experimental results qualitatively. Finally, the aerodynamic characteristics of all 10 airfoils were compared and classified according to their own lift or moment characteristics.

• International Journal of Fluid Machinery and Systems
• /
• v.6 no.1
• /
• pp.11-17
• /
• 2013

Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-CFX) to investigate the internal flow condition in detail. It is clarified from experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Blade-to-blade low velocity regions are suppressed in the case with the splitter blades and total pressure loss regions are decreased. The effects of the splitter blades on the performance and the internal flow condition are discussed in this paper.

• Journal of Korean Foot and Ankle Society
• /
• v.15 no.1
• /
• pp.47-50
• /
• 2011

Equinus contracture of the gastrocnemius-soleus complex is associated with many foot and ankle diseases. We introduce a new simple technique that can be performed using a minimal incision with simple devices. Briefly, 0.5 cm sized medial and lateral longitudinal skin incisions are made at the level of the distal one third of the calf. The musculotendinous junction of the gastrocnemius is gently transected using an Arachnoid blade. The skin is, then, closed with non-absorbable sutures.