• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.8
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• pp.580-588
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• 2009

This paper summarizes the experimentally-measured performance of small-scale, vertical-axis wind turbine for the purpose of improving the aerodynamic efficiency and its controllability. The turbine is designed to have a Savonius-Type rotor with an inlet guide-vane and an side guide-vane so that it achieves a higher efficiency than any lift- or drag-based turbines. The main design factors for this high-efficient, vertical wind turbine are the number of blades (Z), and the aspect ratio of Height/Diameter (H/D) among many. The basic model has the diameter of 580mm, the height of 464mm, and the blade number of 10. The maximum power coefficient of 0.50 was experimentally measured for the above-mentioned specifications. The inlet-guide vane ensures the maximum efficiency when the angle of attack to the rotor blade lies between $15^{\circ}$ and $20^{\circ}$. This experimental results for the vertical-axis wind turbine can be applied to the preliminary design of turbine output curve based on the wind characteristics at the proposed site by controlling its aerodynamic performance given as a priori.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.2
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• pp.75-82
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• 2011

Recently the technology of green growth became more important role among the problems of running out of fossil fuels and global warming. To procure a new growth power combined with energy and green growth, a lot of investment for wind power, photovoltaics system, fuel cell and biofuel expanded day by day. Among these, wing power has a merit of a highly economic and no discharge of toxic substance. These days government and industrial companies actively support the development of wind power technology with lots of investment, but domestic related education and equipment still stay in research level when it is compared with foreign advanced countries which lead the wind power technology. Therefore to expand the base of basic skill required in the related industrials and to advance technology, we are in the situation to be needed a development of a new curriculum and educational equipment which is analogous with the actual industrial system. In this paper a development of a new educational equipment for the learning of turbine control is introduced. This educational equipment has been developed for students to get easy understanding for the theory of wind turbine control. And finally to demonstrate the effect of the use of the developed equipments and curriculum a questionnaire carried out.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.891-898
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• 2007

Optimal aerodynamic design for the pitch-controlled horizontal axis wind turbine and its aerodynamic performance for various pitch angles are performed numerically by using the blade element momentum theory. The numerical calculation includes effects such as Prandtl‘s tip loss, airfoil distribution, and wake rotation. Six different airfoils are distributed along the blade span, and the special airfoil i.e. airfoil of 40% thickness ratio is adopted at the hub side to have structural integrity. The nonlinear chord obtained from the optimal design procedure is linearized to decrease the weight and to increase the productivity with very little change of the aerodynamic performance. From the comparisons of the power, thrust, and torque coefficients with corresponding values of different pitch angles, the aerodynamic performance shows delicate changes for just $3^{\circ}$ increase or decrease of the pitch angle. For precisive pitch control, it requires the pitch control algorithm and its drive mechanism below $3^{\circ}$ increment of pitch angle. The maximum torque is generated when the speed ratio is smaller than the designed one.

• Journal of Power System Engineering
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• v.21 no.1
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• pp.70-79
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• 2017

The output power of turbine is greatly affected by the losses generated within the passage. In order to develop a better turbine or loss models, an experimental study was conducted using a linear cascade experimental apparatus. The total pressure loss and flow structures were measured at two cross-sectional planes located downstream of blade row. Measurement was conducted in a steady state for the several different locations of the blade row along the rotational direction. The blade row moved by 20 % of the pitch, and tip clearance was varied from 2% to 8%. Axial-type blades were used and its blade chord was 200mm. A square nozzle was applied and its size was $200mm{\times}200mm$. The experiment was conducted at a Reynolds number of $3{\times}10^5$ based on the chord. Nozzle flow angle sets to $65^{\circ}$ based on the axial direction and the solidity of blade row was 1.38. From the experimental results, the total pressure loss was greatly varied in the receding region than in the entering region. The flow properties within the blade passage were strongly changed according to the location of blade row.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.65-69
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• 2011

This paper introduces the multi-coil eddy current sensor and its characteristic in magnetic material gas turbine rotor. In the past, magnetic particle inspection method was used for qualitative defect evaluation in magnetic material gas turbine rotor. And the ultrasonic inspection method was used for quantitative defect evaluation. Nowadays, eddy current method is used in magnetic gas turbine rotor inspection due to advanced sensor design technology. We developed multi-coil eddy current sensor for the rotor dovetail inspection. At first, rotor stress is analyzed for the determination of sensor position and number. The sensor coils are designed to cover the stress concentration area of rotor dovetail. We select optimum frequency according to material standard penetration data and experiment results. The rotor mock-up and artificial defects were made for the signal detection and resolution analysis of multi-coil eddy current sensor. The results show that signal detection and resolution capabilities are enhanced in comparison to the commercialized sensor enough for the gas turbine rotor inspection. So, this developed multi-coil eddy current sensor substituted for commercialized one and it applied in real gas turbine rotor inspection.

• Journal of Power System Engineering
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• v.15 no.4
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• pp.37-41
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• 2011

This paper introduces the special eddy current sensor and its characteristic for bolt hole defect evaluation in gas turbine rotor. In the past, Fluorescent penetration inspection method was used for qualitative defect evaluation in gas turbine rotor bolt hole. This method can defect the bolt hole defect but can not evaluate the defect size. Nowadays, eddy current method is used quantitative defect evaluation due to advanced sensor design technology. And eddy current method is more time and cost saving than the old method. We developed bolt shape eddy current sensor for the rotor bolt hole defect detection and evaluation. The eddy current sensor moves to the bolt hole guided by screw nut and detects the defect on the bolt hole. The bolt hole mock-up and artificial defects were made and used for the signal detection & resolution analysis of eddy current sensor. The results show that signal detection capability is enough to detect 0.2 mm depth defect. And the resolution capability is enough to differentiate 02, 0.5, 1.0 and 2.0 mm depth defect.

• Journal of Power System Engineering
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• v.12 no.6
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• pp.70-77
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• 2008

The purpose of this study is to compare the quality of digital radiography image with that of classical film images for welded structure in power plants. The CMOS(Complementary Metal Oxide Semiconductor) flat panel detecter and Agfa D5 film are used to image flaw specimens respectively. In the test, CMOS flat panel detector has been determined to have a better image than that of film image. In the IQI(Image Quality Indicator) transmission test, one or two more line can be seen in digital image than in film image. Digital Radiography Test enabled to successfully detect all defects on the weld specimens fabricated with real reheat stem pipe and boiler tube as well. In the specific comparison test, Digital radiography test detected micro flaws in the size of 0.5 mm in length by 0.5 mm in depth. However, film test has limited it to 1.0 mm in length by 1.0 mm in depth. As a result of this study, digital radiography technology is estimated well enough to perform the inspection in the industry with far more cost effective way, compared to the classical film test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.217-218
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• 2006

This paper presents an investigation on the characteristics for new micro tool dynamometer by using the ultrahigh-speed air turbine spindle. Recently, the ultrahigh-speed micro flat endmilling has been investigated actively due to request of accuracy improvement and productivity of die and mould manufacturing. To perform efficient ultrahigh-speed micro flat endmilling, evaluation of ultrahigh-speed machinability must be studied preferentially and it can be identified by investigation of cutting force. The cutting forces in ultrahigh-speed micro flat endmilling can be measured by micro tool dynamometer. But general dynamometer has low natural frequency and so is improper for measuring very high frequency cutting forces in ultrahigh-speed micro flat endmilling. In this study, the micro tool dynamometer which has very high natural frequency is newly designed.

• Journal of Power System Engineering
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• v.6 no.1
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• pp.55-60
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• 2002

There has been no report on the life prediction for gas turbine materials at high temperatures based on the creep properties and their relationship with the AE(acoustic emission) properties as a means of real-time non-destructive testing. One of the important issues is thus to develop a reliable method of evaluating creep properties by the AE technique. In this paper, the real-time evaluation of high temperature creep time and AE cumulative counts for nickel-based superalloy Udimet 720 was performed on round-bar type specimens under pure load at the temperatures of 811, 922 and 977K. The total AE cumulative counts until the starting point of secondary creep($N_1$) and that of tertiary creep($N_2$) have quantitative relationship with the tertiary creep time and the rupture time. It is thus possible to construct the life prediction system based on creep and the prevention system of tertiary creep by using AE technique.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.16-21
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• 2011

The large scale decisive battle will be gradually reduced on the sea in the future and surface combatant ship installed advanced weapon units as well as propulsion system will be continuously increased. The high level of military technology leads to appear state-of-the-art weapon system using high power energy. As a results, fossil fuel powered main prime mover as diesel engine and gas turbine which are composed of mechanical propulsion system should be decreased from combatant ship in the near future. The new building naval combatant ship with the latest technology has electric based propulsion method of the hybrid type combined with mechanical and electrical drive. U.S. and Royal Navy, especially, select the integrated fully electric based propulsion system for the next generation combat ship and play an important roll for developing them. In this context, this paper was focused on the deduction of implications through analyzing the combatant ship propulsion system using diesel and gas turbine engine which are promoted on the worldwide.