• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.25-29
• /
• 2005

Axial fan is used for the supplement of large amount of flows. Axial blowers show relatively high efficiency of the system. The present model of axial fan is for cooling a condenser in an air-conditioning unit that exhibits tendency toward compact size. In order to realize the compact model, the width of an axial blade should be cut down in axial distance. Main interest lies on the performance of the axial blowing system with blades having shorter chord length. One of the important design parameters for axial fan is the shape of the blades of it. Design of blades includes the cross-sectional shape and its dimension, including the chord length. We consider two types of blades; one is NACA airfoil with normal chord length and the other is with shortening chord length by $10\%$ of normal airfoil. Axial blower with the modified blades is essential for the compact model of an air-conditioner. The other design parameters are same in the two cases. Using a wind tunnel follows ASHRAE standards carries out evaluation of performance of the system. Detail of flows around the blades is prepared by velocity measurements using PIV. According to performance estimation, the axial blower with short chord blade show quite close to the performance results, including flow rate and pressure rise, of the standard one. The reason of the two similar results is that the flowpatterns depend on Reynolds number based on the chord length of a blade. In this investigation, the critical chord length is found, in which the flows near the airfoil are so unstable and the performance of the system is decreased. A series of figures is for the detail information on the flow.

• Journal of Mechanical Science and Technology
• /
• v.16 no.11
• /
• pp.1457-1469
• /
• 2002

This paper is the first of several companion papers, which investigate axial stratification process and its effects in an Sl engine. The axial stratification is very sophisticate phenomenon, which results from combination of fuel injection, port and in-cylinder flow and mixing. Because of the inherent unsteady condition in the reciprocating engine, it Is impossible to understand the mechanism through the analytical method. In this paper, the ports were characterized by swir and tumble number in steady flow bench test. After this, lean misfire limit of the engines, which had different port characteristic, were investigated as a function of swirl ratio and injection timing for confirming the existence of stratification. In addition, gas fuel was used for verifying whether this phenomenon depends on bulk air motion of cylinder or on evaporation of fuel. High-speed gas sampling and analysis was also performed to estimate stratification charging effect. The results show that the AFR at the spark plug and LML are very closely related and the AFR is the results of bulk air motion.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.239-248
• /
• 1997

Steady components and unsteady components of second-order velocity and temperature within pulse tube refrigerators were obtained. Second-order solutions were obtained from the first-order solutions of continuity, momentum and energy equations, assuming that the amplitude of the piston motion is small. The axial temperature gradient was considered in the analysis. The flow direction of the streaming was consistent with previous experimental observations. Effects of axial temperature gradient on secondary flow and second-order temperature were shown.

• 유체기계공업학회:학술대회논문집
• /
• 1998.12a
• /
• pp.91-96
• /
• 1998

The broadband noise generated aerodynamically from a two-bladed axial flow fan has been measured and compared to the result of a self-noise prediction method. The prediction scheme is based on the experimental data set acquired from a series of aerodynamic and acoustic tests of two and three-dimensional airfoil blade sections. For low blade loading case the comparison showed a reasonably good agreement, but as the loading becomes larger the empirical formula overpredict the sound pressure level at high frequency range. This is probably due to the use of stationary wing data for the prediction of rotating blade case, which will be quite different in their vortex strength at the blade tip.

• 유체기계공업학회:학술대회논문집
• /
• 1998.12a
• /
• pp.64-69
• /
• 1998

In this study, a preliminary design method of the axial fan was systematically established based on the two-dimensional cascade theory. Flow deviation, lift coefficient, distribution of velocity and pressure coefficient on blade surfaces were predicted by an inviscid theory of Martensen method, which was also applied to select an airfoil of required performance in the present design process. The aerodynamic performance of designed blades can be predicted quickly and reasonably by using the through-flow calculation method in the preliminary design process. It would be recommendable to adopt three-dimensional viscous flow calculation at the final design refinement stage.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.8
• /
• pp.519-525
• /
• 2016

In a pump, from the performance point of view, it is very important to minimize the shock loss at the inlet of the rotor blades. In this study, the effects of shape and install angle of the inlet guide on the performance of an axial-flow pump are numerically simulated using commercial CFD code, Ansys CFX. Finally, to obtain the optimized shape of the vanes and the install angle of the vanes in the inlet guide under given operating conditions, optimization analysis is conducted using Analysis design exploration based on response surface optimization.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.68-70
• /
• 2002

Prediction of 3-D permeability tensor for multi-axial preform is critical to model and design the manufacturing process of composites by considering resin flow through the multi-axial fiber structure. In this study, the in-plane and transverse permeabilities for braided preform are predicted numerically. The flow analyses are calculated by using 3-D CVFEM(control volume finite element method) for macro-unit cells. To avoid checker-board pressure field and improve the efficiency of numerical computation, a new interpolation function for velocity is proposed on the basis of analytic solutions. Permeability of a braided preform is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Unlike other studies, the current study is based on more realistic unit cell and prediction of permeability is improved.

• Journal of computational fluids engineering
• /
• v.15 no.4
• /
• pp.32-39
• /
• 2010

In this study, we consider Taylor-Couette flow with the outer cylinder at rest and the inner one oscillating with a mean angular velocity. Varying the mean angular velocity, amplitude and frequency of the oscillation, we investigate the characteristics of modulated Taylor vortices. At a constant mean angular velocity, Taylor vortices intensify as the amplitude increases and frequency decreases. The axial wavenumber is calculated by spectral analysis. When the frequency varies, the axial wavenumber does not change at a constant mean angular velocity and amplitude. But, the axial wavenumber increases, as the mean angular velocity increases.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.6
• /
• pp.96-101
• /
• 2000

In this paper, an experimental investigation of characteristics of developing transitional steady flows in a square-sectional 180 urved duct is presented. The experimental study is carried out to measure axial velocity profiles by using Laser Doppler Velocimeter (LDV) system. The flow development is found to depend upon Dean number and curvature ratio. For transitional steady flows, the maximum velocity position of axial velocity profiles begins to incline toward the outer wall from $\phi$=$30^{\circ}$bended angle, velocity profiles in center of the duct have lower value than those of the inner and outer walls because of the centrifugal forces.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.943-948
• /
• 2000

The Twin-fluid Swirl Nozzles are used in many parts of the industry to produce homogeneous spray. This study is to investigate the effects of outer air swiller and inner water swiller on atomization of liquid.. The experiment was carried out with increasing air-flow rate at constant liquid-flow rate and with changing outer air swiller angle and inner water swiller angle. A Particle Dynamics Analyzer(PDA) was used to measure drop size, mean and ms values of axial velocity, number density and Sauter mean diameter(SMD). The axial mean velocity and SMD of droplets were measured along the center line and radial directions. It was found that the higher air flow-rate resulted in the smaller Sauter mean diameter of liquid spray and the higher axial mean velocity of droplets. This experimental results will be conveniently used for the preliminary design stage of twin-fluid nozzle development.