• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.63-75
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• 2017

Many axial fans have circular arc blades with constant thickness. It is still a challenging task to calculate their performance, i.e. to predict how large their pressure rise and pressure losses are. For this task a need for cascade data exists. Therefore, the designer needs a method which works quickly for design purposes. In the present contribution a design method for such cascades consisting of circular arc blades with constant thickness is described. It is based on a singularity method which is combined with a CFD-data-based flow loss model. The flow loss model uses CFD-data to predict the total pressure losses. An interpolation method for the CFD-data are applied and described in detail. Data of measurements are used to validate the CFD-data and parameter variations are conducted. The parameter variations include the variation of the camber angle, pitch chord ratio and the Reynolds number. Additionally, flow patterns of two dimensional cascades consisting of circular arc blades with constant thickness are shown.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.99-106
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• 2010

Gas turbines operation for power generation increased rapidly since 1990 due to the high efficiency in combined cycle, relatively low construction cost and low emission. But the operation and maintenance cost for gas turbine is high because the expensive superalloy hot gas path parts should be repaired and replaced periodically This study analyzed the initiation and propagation of the crack at the gas turbine blades which are coated with MCrAIY as a bond coat and TBC as a top coat. The sample blades had been serviced at the actual gas turbines for power generation. Total 7 sets of blades were analyzed and they have different EOH(equivalent operation hour). Blades were sectioned and the cracking distribution were measured and analyzed utilizing SEM(scanning electron microscope) and optical microscope. The blades which had 52,000 EOH of operation had cracks at the substrate and the maximum depth was 0.2 mm. Most of the cracks initiated at the boundary layer between TBC and bond coat and propagated down to the bond coat. Once bond coat is cracked, the base metal is exposed to the oxidation condition and undergoes notch effect. Under this environment, the crack branched at the inter-diffusion layer and propagated to the substrate. Critical cracks affecting the blade life were analyzed as those on suction side and platform.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1025-1032
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• 2010

Gas turbine compressor blades used in a combined cycle power plant are possibly damaged and fractured during their operation. There are two possible causes of the failure of compressor blades; one is a defect of material quality which can be detected through some microscopic inspections for the fracture section, the other is high cycle fatigue problem caused by vibration and can be diagnosed by carrying out dynamic characteristics analysis for the blades. In this paper, in order to determine the cause of the failure of compressor blades in a combined cycle power plant, examination of the fracture section and the propagation mechanism of the crack via stress analysis are performed. Dynamic characteristics analysis via FRF estimation is also performed to identify the cause of failure.

• New & Renewable Energy
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• v.16 no.2
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• pp.1-13
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• 2020

The reduction of noise from wind turbines has been studied using various methods. Some examples include controlling wind turbine blades, designing low-noise-emitting wind turbine blades, and using trailing-edge serrations. Among these methods, serration is considered an effective noise reduction method. Various studies have aimed to understand the effects of trailing-edge serration parameters. Most studies, however, have focused on fixed-wing concepts, and few have analyzed noise reduction or developed a prediction method for rotor-type blades. Herein, a noise prediction method, composed of two noise prediction methods for a wind turbine with trailing-edge serrations, is proposed. From the flow information obtained by an in-house program (WINFAS), the noise from non-serrated blades is calculated by turbulent ingestion noise and airfoil self-noise prediction methods. The degree of noise reduction caused by the trailing-edge serrations is predicted in the frequency domain by Lyu's method. The amount of noise reduction is subtracted from the predicted result of the non-serrated blade and the total reduction of the noise from the rotor blades is calculated.

• Journal of the Korean institute of surface engineering
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• v.43 no.1
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• pp.41-45
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• 2010

The effect of $MoS_2$ and graphite content on wear resistance and mechanical properties of Cu/Sn bonded diamond micro blades was comparatively investigated in terms of volume and weight fraction. For the evaluation of endurance and cutting performance, instantaneous electric power consumption and cumulative wear loss during cutting glass work piece at constant velocity were measured with the micro blades of the wide range of lubricant content. The energy consumption of blades for glass cutting decreased with the content of lubricants. Wear amount of blade in volume increased with the amount of lubricant addition. It was found to be relevant to the decrease in flexural strength and hardness with the amount of lubricants. With the same amount of lubricant content in volume fraction $MoS_2$ showed superiority in mechanical properties and cutting performance than graphite while graphite could result in stronger effect on lowering electric consumption during cutting work piece for the same weight percent fraction than $MoS_2$ because of lower density.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.385-390
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• 2003

Shape of a multi-blades centrifugal fan is optimized by response surface method based on three-dimensional Navier-Stokes analysis. For numerical analysis, Reynolds-averaged Wavier-Stokes equations with standard $k-{\varepsilon}$ turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Optimizations with and without constraints are carried out. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. The correlation of efficiency with relative size of inactive zone at the exit of impeller is discussed as well as with average momentum fluxes in the scroll.

• ALGAE
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• v.21 no.2
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• pp.193-208
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• 2006

Porphyra pulchella sp. nov. Ackland, West, Scott and Zuccarello was obtained at Mimosa Rock National Park, New South Wales; Westgate Bridge, Victoria, Australia; and Waihau Bay, North Island, New Zealand. It occurs mainly in mangrove habitats and is very small (± 1 mm) in field collections. In laboratory culture at 21 ± 2°C tiny blades (0.5-3.0 mm) reproduced exclusively by archeospores liberated from vegetative cells of the upper sector of the blades. The archeospores displayed amoeboid and gliding motility once discharged. At 14 ± 2°C the blades grew to 25 mm and produced longitudinal spermatangial streaks mixed with ‘phyllosporangial’ streaks. The discharged ‘phyllospores’ showed amoeboid motility and germinated forming asexual blades. A conchocelis phase with typical bangiophycidean pit connections was observed in blade cultures after 8-10 weeks at 14 ± 2°C. Conchocelis filaments produced conchosporangia and these released amoeboid conchospores that developed into archeosporangiate blades. Molecular data indicate that all 3 isolates are genetically identical.

• Journal of Wind Energy
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• v.14 no.3
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• pp.100-108
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• 2023

The aim of this study is to develop guidelines for predicting interference between drones and wakes during non-destructive blade inspections in wind power systems. The wake generated by wind towers and blades can affect the stability of drone flights, necessitating the establishment of guidelines to ensure safe and efficient inspections. In order to predict the interference between drones and blades, environmental variables must be considered, including quantification of turbulence intensity in the wake generated by the tower and blades, as well as determining the appropriate distance between the drone and the tower/blades for flight stability. To achieve this, computational fluid dynamics (CFD) analysis was performed using cross-sectional geometries corresponding to the main wind turbine blade and tower span locations. Based on the CFD analysis results, a safe flight path for drones is proposed, which minimizes the risk of collision and interference with towers and blades during maintenance operations of wind power systems. Implementation of the proposed guidelines is expected to enhance the safety and efficiency of maintenance work.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.559-564
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• 2001

Advanced gas turbine engines employ turbine entry temperatures so high that cooling of the turbine blades is essential. The coolant flow introduces losses which need to be minimized, and therefore it is important that the minimum amount of coolant is used. This work presents the result of the one-dimensional analysis and the effect of the boundary conditions on coolant flow rate in gas turbine blades.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.9
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• pp.888-894
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• 2001

Advanced gas turbine engines employ turbine entry temperatures so high that cooling of the turbine blades is essential. The coolant flow introduces losses which need to be minimized, and therefore it is important that the minimum amount of coolant should be used. This work presents the result of the one-dimensional analysis and the effect of the boundary conditions on coolant flow rate in gas turbine blades.