• 설비공학논문집
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• 제15권4호
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• pp.294-304
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• 2003

An experimental analysis using three-dimensional laser Doppler velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• 한국전산유체공학회지
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• 제9권1호
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• pp.10-17
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• 2004

Comprehensive investigation according to the two kinds of blades is systematically carried out for a design of the centrifugal blower. The motivation of this work is due to demand of enhanced flow rate with higher inlet pressure, such as air purifiers adopting several filters. It is observed that flow rate of the blower with forward blades is larger than that of the system with backward blades. The reason is due to larger outlet velocity from the rotating forward blades and the tendency is validated by a parallel experiment with a wind tunnel. Numerical analysis for the blower system shows detail information between the blades and inside the casing. A series of figures to show the flow details offers deep understanding of a centrifugal blower with the two different blades.

• 한국항공우주학회지
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• 제37권3호
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• pp.215-223
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• 2009

본 연구에서는 헬리콥터 로터 블레이드의 움직임을 모사하기 위해 중첩 격자 기법을 적용하여 헬리콥터 로터의 전진 및 제자리 비행을 모사하였다. 제자리 및 무양력 전진 비행은 Caradonna & Tung의 로터 블레이드를 적용하였으며 전진 비행은 AH-1G 로터 블레이드를 적용하여 수치해석 하였다. 전진 비행 시 cyclic pitch각에 대해서 Newton-Raphson 수렴 방법으로 수치 트림을 수행하였으며 수치 트림에 의한 결과를 실험 및 다른 수치해석 결과와 비교하였을 때 실험값과 유사한 결과를 얻었다. 또한 수치 트림에 의한 결과는 로터 전진면에서 나타나는 BVI 현상을 잘 모사하였다. 지배 방정식은 3차원 비정상 오일러 방정식을 사용하였으며 원방 경계 조건으로 리만 불변치 경계조건을 적용하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.1088-1094
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• 1993

One of the important restraint conditions for determination of rotary tiller parameters is whether the outside of front cutting surface on blade in rotary tiller pushes untilled soil in operation. By theoretical analysis and graphic verification on computer, no sil-push conditions is put forward and formula for calculating the position angle of its bent line derived, as is convenient for selection of rotary tiller parameters and design and drawing of its blade.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권1호
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• pp.50-60
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• 2004

An experimental analysis using three-dimensional Laser Doppler Velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• 대한조선학회논문집
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• 제50권5호
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• pp.282-290
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• 2013

The effects of the combination of blade number for forward and after propeller on the propeller shaft forces of a contra-rotating propeller (CRP) system are presented in the paper. The research is performed through the numerical simulations based on the Reynolds-Averaged Navier-Stokes equations (RANS). The simulation results of the present method in open water condition are validated comparing with the experimental data as well as the other numerical simulation results based on the potential method for 4-0-4 CRP (3686+3687A) and 4-0-5 CRP (3686+3849) of DTNSRDC. Two sets of CRP are designed and simulated to study the effect of the combination of blade number in behind-hull condition. One set consists of 3-blade and 4-blade, while the other is 4-blade and 4-blade. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. From the simulation results, the fluctuations of axial force and moment are dominant in the case of same blade numbers for forward and after propellers, whereas the fluctuations of horizontal and vertical forces and moments are very large in the case of different blade numbers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.326-331
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• 2007

This paper conducts a vibratory loads reduction analysis of an Advanced Active Trailing-edge Flap (AATF) blade utilizing single crystal piezoelectric actuators. For an AATF blade, a new L-L piezostack actuator using single crystal PMN-PT materials is designed. The AATF blade is designed to have similar characteristics to the Advanced Active Twist Rotor (AATR) blade. The active trailingedge flap is assumed to be 20% of the blade span and 15% of the chord, located at 75% of the blade radius. In order to conduct the vibratory loads reduction analysis of the AATF blade in forward flight, DYMORE, a multi-body dynamics analysis code, is used. The simulation result shows that the hub vibratory loads may be reduced by approximately 89% even with a much lower input-voltage when comparing with the other active rotor systems.

• 한국유체기계학회 논문집
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• 제16권5호
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• pp.5-10
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• 2013

The regenerative pump is a kind of turbomachine which is capable of developing high pressure rise at relatively lower flow rates compared to the centrifugal and axial pumps. Although the efficiency of regenerative pumps is much lower than other turbomachines, still they have been widely used in many industrial applications for working at low specific speeds. There are some theoretical models to analysis the pump performance, however, the effect of the blade angle on the pump performance has not been covered in any model to date. In the present study, experimental study on the regenerative pump performance according to the impeller blade angle and its shape has been carried out. The straight radial blades with forward, backward and chevron blades which have inclined angles of $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ were tested. The pump performance characteristics as the pressure head, efficiency were obtained depending on the flow rate for every impeller, and their results, expressed in appropriate non-dimensional coefficients, were compared and analysed in detail. From the experimental results, it was found that the pressure head and the efficiency depend strongly on the blade angles as well as the blade type. These experimental data has made it possible to better understand the effects of the blade angle on the pump performance, and widen the applicability of the current performance analysis and design models with including the effect of blade angles.

• 수산해양교육연구
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• 제28권3호
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• pp.645-652
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• 2016

At the initial stage of propulsion shaft design, in line with shaft alignment, an intensified consideration of lateral vibration is needed to verify its operational safety. Recently the alignment problem affecting the lateral vibration has been becoming issues. However, the theoretical method of forced lateral vibration analysis is not cleary established so far and it is about to simply limited among the classification societies and international standards to avoid the blade natural frequency resonance cpm outside of ${\pm}20%$ of engine rpm at MCR. On the other hand, longer center distance between each support bearing shows an affirmative result normally in shaft alignment analysis whereas the blade order resonance speed may cause lowering near the limitation in the aspect of lateral vibration. Therefore, it is required careful attention to engineers as described above. As a method to solve the problem, it is mainly considered that remove forward stern tube bearing. In this paper, based on a medium size container ship case, theoretical study was carried out in the context of the forward stern tube bearing. The various effects and functions of forward stern tube bearing are reviewed and evaluated. Then an guidance note to lead the conclusion is proposed.

• 한국유체기계학회 논문집
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• 제7권5호
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• pp.13-19
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• 2004

Centrifugal blowers are widely used for air handling units in industry applications. The blower has a centrifugal impeller and a scroll casing including a driving component such as an electric motor. The impeller takes forward or backward blades to induce flows into the blower, Comprehensive investigation according to the two kinds of blades is systematically carried out for a guidance of design for this kind research. It is observed that flow rate of the blower with forward blades is larger than that of the system with backward blades. Otherwise, the system noise is more pronounced in the case of the blower with forward blades. The reason is due to larger velocity from the rotating forward blades that pose obtuse angle with the circumferential direction. The distinguished characteristics are validated by a parallel experiments with a wind tunnel and in an anechoic chamber. Numerical analysis for the system shows detail information inside the blades and the casing. A series of figures to show the flow details offer deep understanding of the performance of a centrifugal blower with different blades.