• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.2012-2017
• /
• 2003

This paper reports on the influence of blade surface roughness on turbine efficiency. The performance of a low speed one-stage axial turbine with roughened blade surfaces was evaluated. Sandpaper with equivalent sandgrain roughness ($k_s$) was used to roughen the blades. Efficiency (${\eta}/{\eta}_0$) decreases by 4.5 % with sandgrain size of 400 ${\mu}m$ on the stator suction surface.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.115-119
• /
• 2004

The effect of a continuous blowing or suction on an oscillating 2-D NACA0012 airfoil was investigated numerically for the dynamic stall control. The influence of control parameter variation was also studied in the view point of aerodynamic characteristics. The result showed that the blowing control kept a higher lift drag ratio before stall angle but the dynamic stall angle was not exceed to without control result. As the slot position was closer to leading edge, the positive control effect becomes greater. The stronger jet and the smaller jet angel made more favorable roles on the control performance. In the cases of the suction, the overall control features were similar to those of the blowing, but dynamic stall angle was increased, i.e. suction was more effective to control dynamic stall. It was also founded that the suction control was showed better control effect as the slot position moves to trail edge within thirty percentage of chord length. In the simulation for the jet strength and the jet angle control, the same tendencies were observed to those of blowing cases.

• Journal of Mechanical Science and Technology
• /
• v.19 no.3
• /
• pp.894-904
• /
• 2005

The flow structure inside the intake head greatly affects the working efficiency of a vacuum cleaner such as suction power and aero-acoustic noise. In this study, the flow inside intake heads of a vacuum cleaner was investigated using qualitative flow visualization and quantitative PIV (Particle Image Velocimetry) techniques. The aerodynamic power, suction efficiency and noise level of the intake heads were also measured. In order to improve the performance of the vacuum cleaner, inner structure of the flow paths of the intake head, such as trench height and shape of connection chamber were modified. The flow structures of modified intake heads were compared with that of the original intake head. The aero-acoustic noise caused by flow separation was reduced and the suction efficiency was also changed due to flow path modification of intake head. In this paper, the variations of flow fields for different intake heads are presented and discussed together with results of aerodynamic power, suction efficiency and noise level.

• Journal of the Korean Society of Safety
• /
• v.10 no.1
• /
• pp.41-49
• /
• 1995

A potable oil skimmer is in need to remove spilt oils before they spread, which is applicable to various situations of oil viscosity, spill location, current, tides, waves and wind. An air suction skimmer was selected to be developed because of its advantages such as simple structure, excellent transportability, and easy deployment. A prototype operating by a commercial vacuum cleaner was fabricated. Tests of the skimmer showed good performance : the maximum suction rate of water and suction head were 18㎥/h and 2.7m, respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.3
• /
• pp.329-338
• /
• 2019

Suction of unsaturated bentonite buffers is a very important input parameter for hydro-mechanical performance assessment and design of an engineered barrier system. This study analyzed suction measurement techniques and constitutive models of unsaturated porous media reported in the literature, and suggested suction measurement techniques and constitutive models suitable for bentonite buffer in an HLW repository. The literature review showed the suction of bentonite buffer to be much higher than that of soil, as measured by total suction including matric suction and osmotic suction. The measurement methods (RH-Cell, RH-Cell/Sensor) using a relative humidity sensor were suitable for suction measurement of the bentonite buffer; the RH-Cell /Sensor method was more preferred in consideration of the temperature change due to radioactive decay heat and measurement time. Various water retention models of bentonite buffers have been proposed through experiments, but the van Genuchten model is mainly used as a constitutive model of hydro-mechanical performance assessment of unsaturated buffers. The water characteristic curve of bentonite buffers showed different tendencies according to bentonite type, dry density, temperature, salinity, sample state and hysteresis. Selection of water retention models and determination of model input parameters should consider the effects of these controlling factors so as to improve overall reliability.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.6
• /
• pp.51-56
• /
• 2010

A numerical simulation is carried out to investigate the effect of flow rate variation and performance characteristics of double-suction centrifugal pump. Two types of pump which have different impeller inlet breadth and curvature of the shroud line consist of six blades impeller and shroud ring. Finite-volume method with structured mesh and $k-\omega$ Shear Stress Transport turbulence model was used to guaranty more accurate prediction of turbulent flow in the pump impeller. Total head, power and overall efficiency were calculated to obtain performance characteristics of two types of pump according to the variation of flow rate. From the results, impeller having smooth curve along the shroud line obtained good performance. The lower flow rate, the more circulation region, flow unsteadiness and complicate flow pattern are observed. Complicated internal flow phenomena through impellers such as flow separation, pressure loss, flow unsteadiness and performance are investigated and discussed.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.3
• /
• pp.1074-1082
• /
• 1996

• The KSFM Journal of Fluid Machinery
• /
• v.16 no.2
• /
• pp.21-26
• /
• 2013

Super-cavitating vehicle which is operating under water speeds up to 100m/s. In this process super-cavitation around body reduces frictional resistance. This paper introduces experimental study on different width of suction path as there is a warhead in the torpedo. Hydraulic performances of turbopump at non-cavitating condition does not display a significant differences depending on different width of suction path. However, cavitation performance of each model shows obvious differences in the same condition of experience. In case of radial inlet, the value of critical NPSH(which indicates 3% head drop) increases about 20% in comparison of axial inlet.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.2 s.35
• /
• pp.13-18
• /
• 2006

This paper was studied to design Process considered flexibility and reliability of suction and discharge valves. Flexibility and reliability of valves are main important factors in compressor valves design. And they are incompatible with efficiency of compressor. In this study, we have performed the optimal design of CO2 compressor valves to consider these factors. At first, we analyzed performance simulation of compressor to obtain optimal flexibility level of valves. From this simulation, we could get some important data at valve design like the optimal natural frequency and the height of retainer. After that we studied to reliability of valves corresponding to optimal flexibility level by finite element method. For each case bending stress and natural frequency were obtained by it. Also we investigated the fatigue stability to obtain optimal valve shape that ensured to reliability.

• Journal of computational fluids engineering
• /
• v.17 no.2
• /
• pp.58-64
• /
• 2012

Turbulent flows in a intake part of vacuum cleaner are studied by RANS simulations. The governing equations are solved by the SIMPLE algorithm based on the finite volume method of the unstructured grid system. The predicted results show that the suction performance is closely related to the variation of flow structure in the intake part. In order to investigate for the cleaning of bedclothes and carpet without sticking, several design changes are applied. The introduction of a solid cylinder in the intake part changes vortical structures significantly. Based on this result, a new design with spiral brushes is proposed. The design shows a good behavior for the suction performance and the flow control.