• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.97-102
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• 2003

An experimental study is conducted to investigate the effects of duct corrugation angle on heat/mass transfer characteristics in wavy ducts by using a naphthalene sublimation technique. The corrugation angles of the wavy ducts are $145^{\circ}$ , $130^{\circ}$ and $115^{\circ}$ . and the Reynolds numbers based on the duct hydraulic diameter vary from 300 to 3,000. At the low $Re(Re{\leq}1000)$, high heat/mass transfer regions are formed by the secondary vortex flows called Taylor-Gortler vortices on both pressure-side and suction-side walls. At the high $Re(Re{\geq}1000)$, the effects of these secondary flows are vanished. As corrugation angle decreases, the local peak Sh induced by Taylor-Gertler vortices are increased and average Sh also enhanced. More pumping power (pressure loss) is required with the smaller corrugation angle due to the stronger secondary vortex flows.

• 대한기계학회논문집B
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• 제29권7호
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• pp.773-783
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• 2005

Internal flow measurement of very low specific-speed semi-open impellers has been carried out by PIV in order to understand better the internal flow patterns that are responsible fur the unique performance of these centrifugal pumps operating in the range of very low specific speed. Two types of impellers, one equipped with six radial blades (Impeller A) and the other with four conventional backward-swept blades (Impeller B), are tested in a centrifugal pump operating at a non-dimensional specific-speed of $n_s=0.24$. Complex flow patterns captured by PIV are discussed in conjunction with the overall pump performance measured separately. It is revealed that Impeller A achieves higher effective head than Impeller B even though the flow patterns in Impeller A are more complex, exhibiting secondary flows and reverse flows in the impeller passage. It is shown that both the localized strong outward flow at the pressure side of each blade outlet and the strong outward through-flow along the suction side of each blade are responsible for the better head performance of Impeller A.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.39-47
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• 2006

Recent trend in pursuit of high performance and effectiveness for automotive cooling system has changed the application of material for impeller of automotive water pump from metal to high ability engineering resin, which can achieve optimization of design of impeller geometry and realize lightweight high efficiency water pump. Closed type water pump improves hydraulic loss of fluid through the clearance between volute casing and impeller compared with that of the existing open type water pump(Although closed type is heavier than open type for the same size and same material, adoption of plastics can solve the problem.). In the present study, the characteristics of hydraulic performance of closed type water pump were investigated with respect to the angle between shroud and hub of impeller and the shape of discharge port of volute casing. Performance tests were carried out for 4 cases, that is, for 2 impellers and 2 casings. The modification of shape of only discharge port can enhance the hydraulic performance by 10 percent and the pump efficiency by 4-6 percent.

• 설비공학논문집
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• 제29권3호
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• pp.127-133
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• 2017

Performance analysis has been carried out on a high side scroll compressor that had a fixed scroll equipped with a circular oil groove on its thrust surface. Oil was supplied to the oil groove through an intermittent opening from a high pressure oil reservoir formed inside the orbiting scroll hub. Oil in the groove was then delivered to both suction and back pressure chambers by pressure differentials and viscous pumping action of the orbiting scroll base plate. Mathematical modeling of this oil groove system was incorporated into a main compressor performance simulation program for an optimum oil groove design. The study findings were as follows. Pressure in the oil groove can be controlled by changing its configuration and the oil passage area. With an enlarged oil passage, the pressure in the oil groove heightens due to an increased flow rate, but the pressure elevation in the back pressure chamber is small, resulting in reduced friction loss at the thrust surface between the two scrolls. On the other hand, by increasing the oil passage area, the oil content in the refrigerant flow increases. Considering all these factors, the energy efficiency ratio could be improved by about 3.6% under the ARI condition by an optimal oil groove design.

• Journal of Chest Surgery
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• 제27권6호
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• pp.489-493
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• 1994

Our patient was a 2.3 kg, male of 33 weeks gestation and spontaneous vaginal delivery. Copious salivary secretion, mild aspiration pneumonia episode due to tracheoesophageal fistula and intermittent cyanotic appearance due to hypoxia were noted shortly after birth. Head up position, frequent upper pouch suction, and adequate fluid and antibiotic therapy were done in incubator. Combined Chest and abdominal film was revealed gas in the stomach and an haziness in right chest with mediastinal shift to the right side. Esophagogram revealed markedly dilated proximal esophagus as blind pouch, and Two dimensional echocardiography showed the Ventricular Septal Defect. The conclusion was congenital esophageal atresia with tracheoesophageal fistula, Vogt-Gross type C, Waterston Risk Category B. Surgical correction with Beardmore anastomosis was performed extrapleurally through 3rd rib bed after the cannulation of umbilical vein and preliminary gastrostomy. The fistula was closed by triple ligation and the upper pouch was then brought down to the presenting surface of the lower esophageal segment that incised, and end to side anastomosis was underwent using interrupt suture placed through the full thickness of both upper pouch and lower esophageal segment. The postoperative patient was well tolerated and recovered uneventfully, permitted feeding on 7th postoperative day after esophagogram.

• Wind and Structures
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• 제33권6호
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• pp.471-480
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• 2021

This present paper leads to investigation of blade-fluid interactions of cambered blade H-Darrieus rotor having EN0005 airfoil blades using comprehensive Computational Fluid Dynamics (CFD) analysis to understand its performance in low wind streams. For several blade azimuthal angle positions, the effects of three different low wind speeds are studied regarding their influence on the blade-fluid interactions of the EN0005 blade rotor. In the prevailing studies by various researchers, such CFD analysis of H-Darrieus rotors are very less, hence it is needed to improve their steady-state performance in low wind velocities. Such a study is also important to obtain important performance insights of such thin cambered blade rotor in its complete rotational cycle. It has been seen that the vortex generated at the suction side of the EN0005 blade rolls back to its leading edge due to the camber of the blade and thus a peak velocity occurs near to the nose position of this blade at its leading edge, which leads to peak performance of this rotor. Again, in the returning phase of the blade, a secondary recirculating vortex is generated that acts on the pressure side of EN0005 blade rotor that increases the performance of this cambered EN0005 blade rotor in its downstream position as well. Here, the aerodynamic performances have been compared considering Standard k-ε and SST k-ω models to check the better suited turbulence model for the cambered EN0005 blade H-Darrieus rotor in low tip speed ratios.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.631-636
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• 2001

The internal flow in the rocket pump inducer of LE-7 engine for H-II rocket was predicted at design and off-design flow rates using CFD code, CFX- Tascflow. In this numerical study, the performance curve of inducer coressponding to flow rates variation and the internal flow in the front of blade leading edge show good agreement between the calculations and the measurements. Backflow is appeared at suction side of leadinge edge tip, and this region is extended to upstream as flowrate decrease. Because of backflow, pressure loss coressponding to meridinal coordinate occupy 50% from inlet domain to leading edge. By this phenomena, pressure loss in front of blade leading edge take a great effect to inducer performance.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.24-29
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• 1999

The ASME strainers have been newly installed at the suction side of each reactor coolant pump to get rid of the foreign materials which may damage the pump impeller or interfere with the coolant path of fuel flow tube or primary plate type heat exchanger. The strainer was designed in accordance with ASME SEC. III, DIV. 1, Class 3 and the structural integrity was verified by seismic analysis. The screen was designed in accordance with the effective void area from the result of flow analysis for T-type strainer. After installation of the strainer, it was confirmed through the field test that the flow characteristics of primary cooling system were not adversely affected. The pressure loss coefficient was calculated by Darcy equation using the pressure difference through each strainer and the flow rate measured during the strainer performance test. And these are useful data to predict flow variations by the pressure difference.

• 한국유체기계학회 논문집
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• 제3권2호
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• pp.57-65
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• 2000

The aim of this paper is to understand the unsteady flow phenomena in a high speed centrifugal compressor channel diffuser. Instantaneous pressures aye measured at six locations in the diffuser using fast-response pressure transducers. Instantaneous pressure ratio decomposition was applied to analyze the pressure signal. In vaneless space where impeller-vaned diffuser interaction is strong, aperiodic unsteadiness is high and periodic pressure waveforms by blade passing are not clear at low flow rates, especially near vane suction side. High aperiodic unsteadiness decreases downstream of diffuser. The blade-to-blade pressure wave does not disappear in surge flow condition. In surge there exist not only large scale periodic surge wave but also blade-to-blade pressure wave.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.197-212
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• 1997

The performance of a torque converter can be expressed by the performance parameters such as flow radius and flow angle, on the mean flow path. The geometric analysis of the torque converter is required to determine these parameters for the modeling of the torque converter. In general, the blade shape is depicted by three dimensional data at the mid-surface of blade or those of the pressure and suction side. To generate three dimensional model of the blade using the data mentioned above, a consistent data format and a shape generation algorithm are required. This paper presents a useful consistent data format of the blades and an algorithm for the geometrical shape generation. By the geometric analysis program to which the shape generation algorithm is embedded, the variation of blade angles in rotating element analyzed. Then finally, the analyzed results of geometric profile of a blade are compared with those of the blade design principle, so called forced vortex theorem.