• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.819-824
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• 2000

The flow inside an axial turbomachinery must be unsteady. Rotor-stator interaction by two blade rows influences performance, the generation of noise and vibration. So, it will be necessary to study the rotor-stator interaction for the design of an axial fan in which the axial gap between two blade rows is small. In this study, rotor-stator interaction is investigated by experimental methods. The research fan has one stage which consists of 24 rotor blades and 22 stator blades. Three-dimensional velocities measured using $45^{\circ}$ slanted hot wire probe and total pressure is measured using Kiel total pressure probe between rotor and stator with the axial 25%, 55%, 145% of chord length,. This study describes the influence of rotor-stator gap on the flow pattern, performance and loss. The efficiency curve show that the change of the rotor-stator gap make difference in the efficiency. And, the 3-dimensional velocity distribution show that the potential interaction between the rotor and the stator have a great effect on the flow field downstream of rotor, where there are wake flow. various vortices in hub region and leakage vortex in casing region etc.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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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.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.571-580
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• 2015

In this paper, a computational study was conducted in order to investigate the rotor blade sweep effect on the aerodynamics of a small axial supersonic impulse turbine stage. For this purpose, three-dimensional unsteady RANS simulations have been performed with three different rotor blade sweep angles ($-15^{\circ}$, $0^{\circ}$, $+15^{\circ}$) and the results were compared with each other. Both NTG (No tip gap) and WTG (With tip gap) models were applied to examine the effect on tip leakage flow. As a result of the simulation, the positive sweep model ($+15^{\circ}$) showed better performance in relative flow angle, Mach number distribution, entropy rise, and tip leakage mass flow rate compared with no sweep model. With the blade static pressure distribution result, the positive sweep model showed that hub and tip loading was increased and midspan loading was reduced compared with no sweep model while the negative sweep model ($-15^{\circ}$) showed the opposite result. The positive sweep model also showed a good aerodynamic performance around the hub region compared with other models. Overall, the positive sweep angle enhanced the turbine efficiency.

• 한국항공우주학회지
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• 제30권4호
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• pp.99-105
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• 2002

본 연구에서는 정익과 동익간의 축방향 간격을 달리하여 축류형 터빈에서의 성능시험을 수행하였다. 실험에 사용된 터빈은 저압저속터빈으로써 평균반경에서 반동도가 0.373이며 축류형 3차원 단단터빈이다. 터빈의 평균반경 직경은 257.56mm이며 평균반경에서 동익의 익현은 28.2mm이다. 성능시험을 위한 공기력 입력장치로는 풍동이 사용되었으며 풍동의 터보블로워 동력은 30kW로써 290mmAq의 정압력에서 $340m^3$/min의 공기량을 보낼 수 있다. 터빈에서의 회전수 및 출력은 터빈 축에 직결식으로 연결된 다이나모메터에서 제어되었다. 실험에서 축방향 간격조정은 평균반경에서의 정익 축방향 익현의 1/4에서 3배까지 변경하여 총 9개의 성능시험을 수행하였다. 같은 무차원 유량과 RPM에서 축방향의 간격에 따른 효율의 변화는 최대 8%이내지만 최고효율을 얻게되는 축방향 간격은 1.6-1.9Cx 였다.

• 한국추진공학회지
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• 제19권3호
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• pp.29-38
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• 2015

본 연구에서는 초음속 충동형 터빈의 노즐과 1단 로터 사이 축 간극 거리를 달리하며 3차원 비정상 유동해석을 수행하고 초음속 터빈의 성능 특성을 분석하였다. 계산결과는 기존의 초음속 터빈 효율 경향과 잘 일치하였으며 특정 축 간극 구간에서 효율의 급격한 감소를 보이고 그 이후에는 큰 변화가 없는 구간이 존재함을 확인하였다. 로터 앞전에서 발생하는 충격파의 영향이 노즐 끝단에 전달이 되는 정도에 따라 터빈 내의 여러 성능 특성이 달라짐을 살펴보았고 터빈 스팬 별 손실 특성에서 축 간극이 커질수록 허브 영역에서의 손실이 증가하고 미드스팬 이상의 영역에서 손실이 감소함을 보였다.

• 대한기계학회논문집B
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• 제30권5호
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• pp.446-456
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• 2006

The effect of relative position of the stationary turbine blade for the fixed vane has been investigated on blade tip and shroud heat transfer. The local mass transfer coefficients were measured on the tip and shroud fur the blade fixed at six different positions within a pitch. A low speed stationary annular cascade with a single turbine stage was used. The chord length of the tested blade is 150 mm and the mean tip clearance of the blade having flat tip is 2.5% of the blade chord. A naphthalene sublimation technique was used for the detailed mass transfer measurements on the tip and the shroud. The inlet flow Reynolds number based on chord length and incoming flow velocity is fixed to $1.5{\times}10^5$. The results show that the incoming flow condition and heat transfer characteristics significantly change when the relative position of the blade changes. On the tip, the size of high heat/mass transfer region along the pressure side varies in the axial direction and the difference of heat transfer coefficient is up to 40% in the upstream region of the tip because the position of flow reattachment changes. On shroud, the effect of tip leakage vortex on the shroud as well as tip gap entering flow changes as the blade position changes. Thus, significantly different heat transfer patterns are observed with various blade positions and the periodic variation of heat transfer is expected with the blade rotation.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.342-351
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• 2010

During the operation of a hydro turbine the fluid mechanical pressure loading on the turbine blades provides the driving torque on the turbine shaft. This fluid loading results in a structural load on the component which in turn causes the turbine blade to deflect. Classically, these mechanical stresses and deflections are calculated by means of finite element analysis (FEA) which applies the pressure distribution on the blade surface calculated by computational fluid dynamics (CFD) as a major boundary condition. Such an approach can be seen as a one-way coupled simulation of the fluid structure interaction (FSI) problem. In this analysis the reverse influence of the deformation on the fluid is generally neglected. Especially in axial machines the blade deformation can result in a significant impact on the turbine performance. The present paper analyzes this influence by means of fully two-way coupled FSI simulations of a propeller turbine utilizing two different approaches. The configuration has been simulated by coupling the two commercial solvers ANSYS CFX for the fluid mechanical simulation with ANSYS Classic for the structure mechanical simulation. A detailed comparison of the results for various blade stiffness by means of changing Young's Modulus are presented. The influence of the blade deformation on the runner discharge and performance will be discussed and shows for the configuration investigated no significant influence under normal structural conditions. This study also highlights that a two-way coupled fluid structure interaction simulation of a real engineering configuration is still a challenging task for today's commercially available simulation tools.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.413-422
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• 2005

본 연구에서는, 먼저 $Fine^{TM}/Turbo$의 신뢰성을 확보하기 위해 초음속 터빈의 실험 결과와 비교 해석하였다. 그 결과 $Fine^{TM}/Turbo$는 초음속 유동 현상을 비교적 정확하게 해석함을 알 수 있었다. 다음으로 Grid Independency Test를 통하여 3차원 터빈의 적합한 격자계를 선정하여. 3차원 초음속 터빈의 노즐-로터 상호작용에 관해 유동해석을 실시하였다. 터빈의 노즐-로터간의 축방향 간격은 점점 커질수록 높은 추력을 나타냈으며, 로터 블레이드의 Chamfering Angle 또한 Blade-Edge가 날카로워 질수록 추력이 증가하였다.

• 대한기계학회논문집B
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• 제25권10호
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• pp.1384-1391
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• 2001

Three-dimensional flow analysis is implemented to investigate the flow through transonic axial-flow compressor rotor(NASA R67) and to evaluate the performances of Abid's low-Reynolds-number k-$\omega$ and Baldwin-Lomax turbulence models. A finite volume method is used fur spatial discretization. The equations are solved implicitly in time by the use of approximate factorization. The upwind difference scheme is used for inviscid terms and viscous terms are approximated with central difference. The flux-difference-splitting method of Roe is used to obtain fluxes at the cell faces. Numerical analysis is performed near peak efficiency and near stall. The results are compared with the experimental data for NASA R67 rotor. Blade-to-Blade Mach number distributions are compared to confirm the accuracy of the code. From the results, it is concluded that Abid'k-$\omega$ model is better for the calculation of flow rate and efficiency than Baldwin-Lomax model. But, the predictions for Mach number and shock structure are almost the same.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.279-283
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• 2002

The effects of finite gap at the tip of turbomachinery blades have long been topics of both theoretical and experimental research because tip clearance degrades turbomachinery performance. This paper presents an analytical study of radial flow redistribution in a high speed compressor stage with axisymmetric tip clearance. The flow is assumed to be inviscid and compressible. The stage is modeled as an actuator disc and the analysis is carried out in the meridional plane. Upon going through the stage, the radially uniform upstream flow splits into the tip clearance and passage flows. The tip clearance flow is modeled as a jet driven by blade loading, or pressure difference between the pressure and suction sides. The model takes into consideration the detached shocks which occur in the rotor passage at the design point. This shock model is used to calculate the density ratio across the stage. Thus, the model is capable of predicting the kinematic effects of tip clearance in the high speed compressor flow field.