• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.105-110
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• 2002

Experimental study was conducted to reveal the instability such as leakage flow and rotating stall in an axial flow fan. For this study, unsteady total pressure probe and multi-hole pressure probe were specially designed for measuring the flow field upstream and downstream of rotor. The measured pressure signal was analyzed by Single and Double Phase Locked Averaging Technique. From the result of total pressure fields at inlet and outlet of the rotor, the useful information on the structure of the stall cell in radial direction was provided. Also, detailed flow measurements were carried out with a specially designed high frequency multi-hole pressure probe, providing some insight to the leakage flow and their interation.

• 대한기계학회논문집B
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• 제23권11호
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• pp.1371-1378
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• 1999

Flow through turbomachinery has a very complex structure and Is Intrinsically unsteady. In addition, trend to highly loaded turbomachinery makes the flow extremely complex due to the interaction between rotor and stator. In this study, flows through UTRC LSRR turbine are numerically analyzed using 2 dimensional Navier-Stokes equations. The convective terms of the governing equations are discretized using the Van-Leer's FVS(Flux vector splitting) with an upwind TVD scheme. The conventional central differencing is used to discretize the diffusion terms on the finite volume. The accurate unsteady motion is achieved by using a 2nd order accurate, 3-point Euler implicit scheme. The quasi-conservative zonal scheme is used for calculating the flow variables on the zonal interface between the rotor and stator. The axial gap between stator and rotor has been configured in two variations, 15% and 65% of average chord length. The analysis program is validated using experimental results and the effect of axial gap is examined. The numerical analysis results are presented by time averaged pressure coefficient and pressure magnitude coefficient and compared with experimental results.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.49-54
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• 1998

The flow inside an axial turbomachinery with multi-stage can be characterized as unsteady phenomena. In order to predict accurately these complex unsteady flow patterns including rotor-stator interaction effects, enormous computer resources are required. So it is not compatible in preliminary design process. In this study, steady coupled blade row flow with rotor-stator interaction solver is developed using interrow mixing model and used to predict the performance of the axial fan. To verify the computational method, the calculations are compared with experimental results and show satisfactory agreement with them. The interaction effects on the performance of the axial fan have also been studied by comparing the results of steady coupled blade row and steady single blade row flow calculation.

• 한국항공우주학회지
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• 제32권4호
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• pp.1-11
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• 2004

축류식 인라인 덕트팬의 개밥을 위해 엇회전식 측류팬의 공력 특성에 관한 수치해석을 수행하였다. 기존의 동익과 정익으로 구성된 축류팬의 설계기법을 확장하여, 서로 반대방향으로 회전하는 전단 동익과 후단 동익의 블레이드 형상을 설계하였다. 그리고, 압축기나 터빈 등의 터보기계 관통 유동 해석 기법인 행렬법을 엇회전식 축류팬에 적용하였고, 주파수영역 패널법을 확장하여 엇회전식 축류팬의 공력 해석 및 성능 예측을 수행하였다. 엇회전식 축 류팬의 관통 유동 해석 결과, 전단 동익과 후단 동익의 허브 부분에서 많은 유통 손실이 발생했다. 그리고, 주파수 영역 패널법을 이용한 공력 해석을 통해 블레이드의 유동손실이 주로 블레이드 전연에서 나타남을 알 수 있었고 성능 특성이 약간 과도하게 예측되었다.

• 대한기계학회논문집B
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• 제27권2호
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• pp.155-162
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• 2003

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Three design variables were selected to optimize the stacking line of the blade. 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, adiabatic efficiency was successfully improved. It is also found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.639-645
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• 2003

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Two design variables were selected to optimize the stacking line of the blade, and mass flow was used as a design variable, as well, to obtain new design point at peak efficiency. 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, adiabatic efficiency was successfully improved, and new design mass flow that is appropriate to an improved blade was obtained. Also, it is found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

• 한국유체기계학회 논문집
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• 제12권1호
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• pp.22-27
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• 2009

The important problems that arise in the design and performance of the axial flow turbine are the prediction and control of secondary flows. Some progresses have been made on understanding flow conditions that occur when the inlet endwall boundary layer separates at the point in the endwall and rolls up into the horseshoe vortex. And the flows though an axial turbine tend to be extremely complex due to its inherent unsteady and viscous phenomena. The passing wakes generated from the trailing edge of the stator make an interaction with the rotor. Unsteady flow should be considered rotor/stator interactions. The main purpose of this research is control of secondary flow and improvement efficiency in turbine by leading edge modification in unsteady state. When the wake from the stator ran into the modified leading edge of the rotor, the leading edge generated the weak pressure fluctuation by complex passage flows. In conclusion, leading edge modification(bulb2) results in the reduced total pressure loss in the flow field.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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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.

• 대한기계학회논문집B
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• 제31권1호
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• pp.68-75
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• 2007

A three-dimensional computation is conducted to simulate a three-dimensional rotating stall in a low speed axial compressor. It is generally known that a tip leakage flow has an important role on a stall inception. However, almost of researchers have taken no interest in a role of the hub-comer-stall on the rotating stall even though it is a common feature of the flow in an axial compressor operating near stall and it has a large effect on the flows and loss characteristics. Using a time-accurate unsteady simulation, it is found that the hub-comer-stall may be a trigger to collapse the axisymmetric flows under high loads. An asymmetric disturbance is initially originated in the hub-comer-stall because separations are naturally unstable flow phenomena. Then this disturbance is transferred to the tip leakage flows from the hub-comer-stall and grows to be stationary stall cells, which adheres to blade passage and rotate at the same speed as the rotor. When stationary stall cells reach a critical size, these cells then move along the blade row and become a short-length-scale rotating stall. The rotational speed of stall cells quickly comes down to 79 percent of rotor so they rotate in the opposite direction to the rotor blades in the rotating frame.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.543-544
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• 2006

Shape optimization of a transonic axial compressor rotor operating at the design flow condition has been performed using three-dimensional Navier-Stokes analysis and three different surrogate models: i.e.., Response Surface Method(RSM), Kriging Method, and Radial Basis Function(RBF). Three design variables of blade sweep, lean and skew are introduced to optimize the three-dimensional stacking line of the rotor blade. The object function of the shape optimization is selected as an adiabatic efficiency. Throughout the shape optimization of the rotor blade, the adiabatic efficiency is increased for the three different surrogate models. Detailed flow characteristics at the optimal blade shape obtained by different optimization method are drawn and discussed.