• Journal of computational fluids engineering
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• v.17 no.3
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• pp.53-58
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• 2012

Steady flow simulations through a high pressure turbine guide vanes were carried out. The main objective of the present work is to study the performance of turbulence models on the steady flow prediction from aerodynamic and aerothermal points of view. Three turbulence models were compared, namely SST, k-${\omega}$ and ${\omega}$-Reynolds stress models. The laminar results were also compared. The comparison was done with emphasis on the isentropic Mach number and heat transfer coefficient along the blade, and total pressure loss in the wake region. The calculated isentropic Mach number showed reasonable agreement with experimental data along the blade surface for all three turbulent models. For the total pressure loss in the wake region, ${\omega}$-Reynolds stress model showed the best agreement with the experimental data. However, unless using an appropriate transition model, the heat transfer coefficients of all three turbulent models showed poor agreement with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.336-345
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• 1998

The substantial loss behind axial flow rotor was generated by wake, various vortices in the hub region and the leakage vortex in the tip region. Particularly, the leakage vortex formed near blade tip was one of the main causes of the reduction of performance, the generation of noise and the aerodynamic vibration in rotor downstream. In this study, the three-dimensional flowfields in an axial flow rotor for various tip clearances were calculated, and the numerical results were compared with the experimental ones. The numerical technique was based on SIMPLE algorithm using standard k-.epsilon. model (WFM). Through calculations, the effects of the tip clearance on the overall performance of rotor and the loss distributions, and the increase in the displacement, momentum, and blade-force-deficit thickness of the casing wall boundary layer were investigated. The mass-averaged flow variables behind rotor agreed well with the experimental results. The presence of the tip leakage vortex behind rotor was described well. Although the loci of leakage vortex by calculation showed some differences compared with the experimental results, its behavior for various tip clearances was clarified by examining the loci of vortex center.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.861-866
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• 2004

A numerical flow analysis has been performed on the partial admission turbine of KARI turbopump to support the aerodynamic and structural dynamic assessments. The flow-field in a partial admission turbine is essentially three dimensional and unsteady because of a tip clearance and a finite number of nozzles. Therefore the mixing plane method is generally not appropriate. To avoid heavy computational load due to an unsteady three dimensional calculation, a frozen rotor method was implemented in steady calculation. It adopted a rotating frame in the grid block of a rotor blade by adding some source terms in governing equations. Its results were compared with a mixing plane method. The frozen rotor method can detect the variation of flow-field dependent upon the blade's circumferential position relative to the nozzle. It gives a idea of wake loss mechanism starting from the lip of a nozzle. This wake loss was assumed to be one of the most difficult issues in turbine designers. Thus, the frozen rotor approach has proven to be an efficient and robust tool in design of a partial admission turbine.

• 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.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.413-414
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• 2008

Abstract should be in English. The leaning angle optimization of turbine blade using the genetic algorithm was conducted in this paper. The calculation CFD technique was based upon the Diagonalized Alternating Directional Implicit scheme(DADI) with algebraic turbulencemodeling. The leaning angle of VKI turbine blade was represented using B-spline curve. The control points are the design variable. Genetic algorithm was taken into account as an optimization tool. The objective was to minimize the total pressure loss. The optimized final geometry shows the better aerodynamic performance compared with the initial turbine blade.

• The KSFM Journal of Fluid Machinery
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• v.19 no.2
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• pp.16-20
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• 2016

Design optimization of a transonic compressor rotor(NASA rotor 37) was carried out using response surface method(RSM) which is one of the optimization methods. A numerical simulation was conducted using ANSYS CFX by solving three-dimensional Reynolds-averaged Navier Stokes(RANS) equations. Response surfaces that were based on the results of the design of experiment(DOE) techniques were used to find an optimal shape of blade which has the maximum aerodynamic performance. Two objective functions, viz., the adiabatic efficiency and the loss coefficient were selected with three design configurations to optimize the blade shape. As a result, the efficiency of the optimized blade is found to be increased.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.78-82
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• 2004

The cross-flow fan which is used for air-conditioner indoor units were studied experimentally. The recent trend shows that the room air-conditioners need to be good-looking. According to the visual design concepts the intake regions of the fan can vary, which leads to the loss of the performance and the increase of the noise of the fan. In order to optimize the performance of the fan and minimize the aerodynamic noise for the system, the performance characteristics and the noise of the cross-flow fan have been investigated at the various conditions of the intake region of the unit.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.97-103
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• 2011

With the aim to increase blade loadings and stable operating range in highly loaded compressors, this article has been conducted to explore, through a numerical parametric study, the potential of passive control using slotted bladings in cascade configurations. The objective of this numerical investigation is to analyze the influence of location, width and slope of the slots and therefore identify the optimal configuration. The approach is based on two dimensional cascade geometry, low speed regime, steady state and turbulent RANS model. The results show the efficiency of this passive technique to delay separation and enhance aerodynamic performances of the compressor cascade. A maximum of 28.3% reduction in loss coefficient have been reached, the flow turning is increased with approximately $5^0$ and high loading over a wide range of angle of attack have been obtained for the optimized control parameter.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.155-161
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• 2000

To improve the vehicle fuel economy, various technologies such as improvement of power train efficiency, use of light weight material, improvement of aerodynamic design, have been studied. One of the possible way to improve the vehicle fuel economy is to reduce the engine friction loss by improving the engine oil characteristics. In the present paper, it was examined the effect of the engine oil viscosity and the addition of friction modifier to engine oil on vehicle fuel economy improvements. Moreover, the effect of engine oil degradation on vehicle fuel economy was examined with two gasoline vehicles and one diesel vehicle by using the fuel economy test facility.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.686-689
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• 2008

The leaning angle optimization of turbine blade using the genetic algorithm was conducted in this paper. The calculation CFD technique was based upon the Diagonalized Alternating Directional Implicit scheme(DADI) with algebraic turbulence modeling. The leaning angle of VKI turbine blade was represented using B-spline curve. The control points are the design variable. Genetic algorithm was taken into account as an optimization tool. The objective was to minimize the total pressure loss. The optimized final geometry shows the better aerodynamic performance compared with the initial turbine blade.