• The KSFM Journal of Fluid Machinery
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• v.2 no.4 s.5
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• pp.16-23
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• 1999

The characteristic of unsteady flowfields on gas turbine, particularly on a rotor blade surface has been numerically investigated. The unsteady flow in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid flow approach, and solved by Euler equations using a time accurate marching scheme. Unsteady flow in the blade passage is induced by periodically moving a wake model across the passage inlet. The wake model used in this study is the Gaussian wate model in which the wake flow is assumed to be parallel with uniform static pressure and uniform relative total enthalpy. Numerical results show that for the case of Ps/Pr=1.5, the velocity and pressure distribution on the blade surfaces have much more complex profiles than for the case of Ps/Pr=1.0.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.233-239
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• 1998

The effects of unsteady flow on gas turbine, particularly on a rotor blade surface are numerically investigated. The unsteady flow in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid flow approach, and solved by the Euler equations using a time accurate marching scheme, Numerical results show that for the case of $P_s/ P_r= 1.5$, the velocity and pressure distribution on the blade surfaces have much more complex profiles than those of $P_s/ P_r= 1.0$.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.428-433
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• 2000

The characteristics of unsteady heat transfer and boundary layer flow in the SSME turbine rotor passage are investigated with LRN $k-{\varepsilon}$ turbulence model. The unsteady flow and heat transfer in a rotor blade passage as a result of wake/blade interaction is modeled by the inviscid/boundary-layer flow approach. The relevant governing equations are discretized to a system of finite different equations by means of a BTBCS implicit method. These equations have been solved numerically, for the velocity and temperature fields using TDMA method. Heat flux on the blade surface and flow parameters in the rotor passage are calculated with wake interaction. Numerical results show that velocity, pressure, turbulent kinetic energy and heat flux on the blade surface are varied periodically by wake passing.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2591-2596
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• 2007

The effect of incidence angle on the three-dimensional flow and aerodynamic loss in the downstream region of a high-turning turbine rotor blade has been investigated with a straight miniature five-hole probe. The incidence angle is changed to be +10, +5, 0, -10, -20, -30 and -40 degrees. The results show that the positive incidence reinforces the three-dimensional vortical flows within the turbine passage including the passage vortex, but the negative incidence weaken them significantly. A small increment in the positive incidence angle results in a remarkable aerodynamic loss increase, while increasing the incidence angle in the negative range leads to a very small change in the aerodynamic loss.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.525-532
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• 2005

Shape optimization of a transonic axial compressor rotor operating at the design flow condition has been performed using response surface method and three-dimensional Navier-Stokes analysis. 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. the adiabatic efficiency is increased by reducing the tub comer and tip losses. Separation line due to the interference between a passage shock and surface boundary layer on the blade suction surface is moved downstream for the optimized blade compared to the reference one.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.94-101
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• 2002

The steam turbine rotor blade is designed using the Turbine Rotor Design Package developed by the authors. It can quickly accomplish blade shape design in the power plant industry. The quasi-3d code is employed for analysis of passage flow in the blade sections. Iterative change of each blade shape is made by moving position of control points in the Bezier curve under GUI(graphic user interface) environment. The full 3-D blade shape is obtained by stacking of the section blades.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.2
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• pp.190-199
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• 2011

Unsteady flow simulations of complete helicopter configurations were conducted, and the flow fields and the aerodynamic interferences between the main rotor, fuselage, and tail rotor were investigated. For these simulations, a three-dimensional flow solver based on unstructured meshes was used, coupled with an overset mesh technique to handle relative motion among those components. To validate the flow solver, calculations were made for a UH-60A complete helicopter configuration at high-speed and low-speed forward flight conditions, and the unsteady airloads on the main rotor blade were compared to available flight test data and other calculated results. The results showed that the fuselage changed the rotor inflow distribution in the main rotor blade airloads. Such unsteady vibratory airloads were produced on the fuselage, which were nearly in-phase with the blade passage over the fuselage. The flow solver was then applied to the simulation of a generic complete helicopter configuration at various flight conditions, and the results were compared with those of the CAMRAD-II comprehensive analysis code. It was found that the main rotor blades strongly interact with a pair of disk-vortices at the outer edge of the rotor disk plane, which leads to high pulse airloads on the blade, and these airloads behave differently depending on the specific flight condition.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.223-230
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• 2005

The unsteady nature of vortex structures has been investigated by a large eddy simulation (LES) in an axial flow fan with a shroud covering only the rear region of its rotor tip. The simulation shows that the tip vortex plays a major role in the structure and unsteady behavior of the vortical flow in the fan. The movements of the vortex structures induce high-pressure fluctuations on the rotor blade and in the blade passage. Frequency characteristics of the fluctuating pressure on the rotor blade are analyzed using wavelet transform. The dominant frequency of the real-time pressure selected at the high pressure fluctuation region corresponds well to that of the fluctuating rotor torque and the experimental result of fan noise. It is mainly generated due to the unsteady behavior of the vortical flow, such as the tip vortex and the leading edge separation vortex.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.125-133
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination as a whole. This often imposes a serious computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is to adopt a momentum source method in which the action of rotor is approximated as momentum source over a rotor disc plane in a stationary computational domain. This makes the simulation much simpler. For unsteady simulation, the instantaneous momentum sources are assigned only to a portion of disk plane corresponding to blade passage. The momentum source is obtained by using blade element theory with dynamic inflow model. Computations are carried out for the simple rotor-airframe model (the Georgia Tech model) and the results of the simulation are compared with those of the full Navier-Stokes simulation with moving mesh system for rotor and with experimental data. It is shown that the present simulation yields results as good as those of the full Navier-Stokes simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.10-18
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• 2007

A tested micro axial-type turbine consists of two stages and its mean radius of rotor flow passage is 8.4 mm. This turbine could be applied to a driver of micro power system, and its rotational speed in the unloaded state reaches to 100,000 RPM. The performance of this system is sensitive depending on the blade angles of the rotor and stator because it is operated in a low partial admission rate, so a performance test is conducted through measuring the specific output power and the net specific output torque with various blade angles on the nozzle, stator and rotor. The experimental results show that the net specific output torque is varied by 15% by changing the rotor blade angle, and the optimal incidence angle is about $10.3^{\circ}$.