• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1383-1388
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• 2004

The flow characteristics in the blade passage of a low speed axial flow fan have been investigated by experimental analysis using a rotating hot-wire sensor for design and off-design operating conditions. The results show that the tip leakage vortex is moved upstream when flow rate is decreased, thus disturbing the formation of wake flow near the rotor tip. The tip leakage vortex interfaces with blade pressure surface, and results in high velocity fluctuation near the pressure surface. From the relative velocity distributions near the rotor tip, large axial velocity decay is observed at near stall condition, which results in large blockage compared to that at the design condition. Througout the flow measurements using a quasi-orthogonal measuring points to the tip leakage vortex, it is noted that the radial position of the tip leakage vortex is distributed between 94 and 96 percent span for all flow conditions. High spectrum density due to the large fluctuation of the tip leakage vortex is observed near the blade suction surface below the frequency of 1000 Hz at near stall condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.84-94
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• 2003

It is known that tip clearance flows reduce the pressure rise, flow range and efficiency of the turbomachinery. So, the clear understanding about flow fields in the tip region is needed to efficiently design the turbomachinery. The Navier-Stokes code with the proper treatment of the boundary conditions has been developed to analyze the three-dimensional steady viscous flow fields in the transonic rotating blades and a numerical study has been conducted to investigate the detail flow physics in the tip region of transonic rotor, NASA Rotor 67. The computational results in the tip region of transonic rotors show the leakage vortices, leakage flow from pressure side to suction side and their interaction with a shock. Depen ding on the operating conditions, toad distributions and the position of shock-wave on the blade surface are very different close to the blade tip of the transonic compressor rotor. The load distribution and the shock-wave position close to the blade tip had the close relationship with the starting position of leakage vortex and the direction of leakage flow.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.91-98
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• 2017

Performance of a low speed axial compressor is enhanced through a proper configuration of blade row tip injection and casing treatment of groove type. Air injectors were mounted evenly spaced upstream of the blade row within the casing groove and were all aligned parallel to the compressor axis. The groove, which covers all the blade tip chord length, extends all-round the casing circumference. Method of investigation is based on solution of the unsteady form of the Navier-Stokes equations utilizing $k-{\omega}$ SST turbulence model. Extensive parametric studies have been carried out to explore effects of injectors' flow momentums and yaw angles on compressor performance, while being run at different throttle valve setting. Emphasis has been focused on situations near to stall condition. Unsteady numerical analyses for untreated casing and no-injection case for near stall condition provided to discover two well-known criteria for spike stall inception, i.e., blade leading edge spillage and trailing edge back-flow. Final results showed that with only 6 injectors mounted axially in the casing groove and at yaw angle of 15 degrees opposite the direction of the blade row rotation, with a total mass flow rate of only 0.5% of the compressor main flow, surprisingly, the stall margin improves by 15.5%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.69-74
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• 2003

By employing vane tip concept, a new rotor blade (NRSB-I) has been designed to enhance the noise characteristics of BERP blade. Numerical analyses have been performed for hovering rotor and the results are compared with respect to those of original BERP blade. Although the thrust of designed rotor decreases by 6-7% due to cutout at the tip region, the results indicate that the actual performance loss is negligible because power reduction is greater than thrust loss. It is also found that aerodynamic fence is required at the outboard kink to obtain clearly separated twin-vortices because the vortex generated at kink is diffused during the convection over the blade surface.

• The KSFM Journal of Fluid Machinery
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• v.15 no.3
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• pp.5-11
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• 2012

This study is to develop a 1kW-class horizontal axis wind turbine(HAWT) rotor blade which will be applicable to relatively low wind speed regions in southwest islands in Korea. Shape design of 1kW-class small wind turbine rotor blade is carried out using a blade profile with relatively high lift to drag ratio by blade element momentum theory(BEMT). Aerodynamic analysis on the newly designed rotor blade is performed with the variation of tip speed ratio. Power coefficient and pressure coefficient of the designed rotor blade are investigated according to tip speed ratio.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.1
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• pp.92-102
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• 2000

In this study, the 750kW medium scale composite blade for the horizontal axis wind turbine system was designed and manufactured, and it was tested and evaluated by the specific structural test rig. In the test, it was found that local bucklings at the trailing edge of the blade and excessive deflections at the blade tip were happened. In order to solve these problems, the design of blade structure was modified. After improving the design, the abrupt change of deflection at the blade tip was reduced by smooth variation of the spar thickness and the local buckling was removed by extending the web length. The modified design was analyzed by the FEM, the safety and stability of the blade structure. And Fatigue life over 20 years was confirmed by using S-N linear damage method, Spera's method, etc.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.619-622
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• 2002

It has been recognized that the flow in the blade passage of an axial turbomachinery rotor is very complex and is influenced by various flow phenomena, of which the tip leakage flow passing through the gap between rotor blade tip and casing plays a significant role. The losses produced due to the existence of the clearance have been known to be a large contributor of the rotor overall losses. Despite several experimental studies on non-rotating blade in the cascade configuration, and on actual rotating blades, the detailed nature of the complex flow phenomena associated with tip leakage, however, remains largely unresolved. Thus, a single-stage compressor test rig was built and measurements were taken at upstream and downstream of the rotor of this compressor at the aerodynamics laboratory of University of New South Wales. A five-hole probe and a hot-wire probe were used to measure mean and fluctuating flow parameters. The results show that tip leakage losses rise rapidly beyond tip gap of 0.01 Furthermore, the present project also identifies the regions in the wake behind the rotor of the axial compressor where such losses are concentrated. These results should be useful in the better design of rotors for improved performance of axial compressor.

• Korean Journal of Agricultural Science
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• v.11 no.2
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• pp.264-269
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• 1984

The single edged blade was efficient to reduce tilling torque requirement than the double edged blade as previous reported study. This study was carried out to find reducing effects of tilling torque requirement of single edged blade comparing to double edged one in according to wearing by tilling operation. The single and double edged rotary blades were attached on same rotary shaft, and tilling operation was done in hard glass land. The wearing weights of the blade were checked out each 3 hrs tilling operation, at same time, the tilling toruqe requirements were measured with soil bin system in laboratory. The results of the study were summarized as follows: 1. The edged blade shape was not changed during the tilling operation of the rotary blade. The single edged blade was saved 5-10% in the maximum tilling torque and 3-15% in the mean tilling torque than the double edged blade for total durable period. 2. Generally, the tilling torques according to operation were decreased until original shape was maintained, but it was increased after 12 hrs tilling operation, and the tip shape of rotary blade was changed seriously. It is noted that the tip shape of the rotary blade is another factor affecting tilling torque, it should be desirable to study on the rotary blade tip shape to reduce tilling torque requirement after changing its original shape with wearing.

• Journal of KSNVE
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• v.10 no.2
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• pp.229-239
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• 2000

To reduce the drag rise on the advancing helicopter rotor blade tips, the tip of the blade is modified to have sweep, anhedral and pretwist. The equations of motion of rotor blade with these tip angles were derived using Hamilton principle, programmed using FORTRAN and named as ARMDAS(Advanced Rotorcraft Multidisplinary Design and Analysis System). Rotating frequency analysis of rotor blades with swept tipe was performed that is necessary in conceptual and preliminary design phases of the helicopter design. Vibration analysis of non-rotating blades was also accomplished and compared with MSC/NASTRAN resutls for the basis of comparison with the vibration test data. The rotating frequency analysis of blades with an actual rotor blade data was also performed to verify coded program and to check the possibility of a resonance of an actual rotor blade at the specific rotating speed.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1465-1469
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• 2009

Darrieus wind turbine blade is one of the vertical wind power system in which the lift of blade is used. In the calculation of wind power for the type of that, the multiple streamtubes method is known as an effective method. But it has big difference in the region of higher tip speed ratio because the incoming air velocity is used in the calculation of lift. The incoming air velocity is reduced from inlet to outlet continually by transferring energy to the wind blade. In this study, the air velocity on the blade, which is called blade velocity, is obtained with newly developed algorithm and used to determine the lift. And it is verified that applying blade velocity on the lift calculation cause the power prediction to improve dramatically in the region of higher tip speed ratio.