• 대한기계학회논문집B
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• 제20권4호
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• pp.1363-1375
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• 1996

Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate three-dimensional flow characteristics and total pressure losses of a row of film-cooling jets injected in spanwise direction. For several span-to-diameter ratios, experiments are performed in the case of three velocity ratios of 0.5, 1.0 and 1.5. The flow measurements show that downstream flow due to the injection is characterized by a single streamwise vortex instead of a pair of counter-rotating vortices, which appear in the case of streamwise injection, and the vortex strength strongly depends on the velocity ratio. Regardless of the velocity*y ratio, presence of the spanwise film-cooling jets always produces total pressure loss, which is pronounced when the velocity ratio is large. It has also been found that the production of the total pressure loss is closely related to the secondary vortical flow. In addition, effects of the span-to-diameter ratio on the flow and total pressure loss are discussed in detail.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.702-707
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• 2001

The characteristics of flow in dividing regions are precise, therefore their classification is very important not only in industry but also in hydrodynamics. By now, many studies of flow in dividing regions have been performed, but flow characteristics that use visualization in dividing regions have not been studied. The present study of the PIV and the CFD exhibit average velocity distributions, kinetic energy distributions and total pressure distributions etc of the total flow field due to the development of the accurate visualization optical laser and of optical equipment. Also, PIV is accurate with the flows characteristics of the dividing region as continuous analysis is done using input equipment. The study analyzes average velocity vector field, average kinetic energy, x-axis stress distributions, average and total pressure distributions of dividing regions with flow for visualization of the PIV and the CFD measurement in a dividing rectangular duct.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.270-275
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• 2001

The characteristics of flow in dividing regions are precise, therefore their classification is very important not only in industry but also in hydrodynamics. By now, many studies of flow in dividing regions have been peformed, but flow characteristics that use visualization In dividing regions have not been studied. The present study of the PIV and the CFD exhibit average velocity distributions, kinetic energy distributions and total pressure distributions etc of the total flow field due to the development of the accurate visualization optical laser and of optical equipment. Also, PIV is accurate with the flows characteristics of the dividing region as continuous analysis is done using input equipment. The study analyzes velocity vector field, turbulence kinetic energy, turbulence viscosity of dividing regions with flow for visualization of the PIV and the CFD measurement in a dividing rectangular ducts.

• International Journal of Fluid Machinery and Systems
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• 제2권1호
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• pp.80-91
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• 2009

In this study, a prediction theory for specific noise that is the overall characteristic of the fan has been proposed. This theory is based on total pressure prediction and broadband noise prediction. The specific noises of two forward curved fans with different number of blades were predicted. The flow around the impeller having 120 blades (MF120) was more biased at a certain positions than the impeller with 40 blades (MF40). An effective domain of the energy conversion of MF40 has extended overall than MF120. The total pressure was affected by the slip factor and pressure loss caused by the vortex flow. The suppression of a major pressure drop by the vortex flow and expansion of the effective domain for energy conversion contributed to an increase in the total pressure of MF40 at the design point. The position of maximum relative velocity was different for each fan. The relative velocity of MF120 was less than that of MF40 due to the deviation angle. The specific noise of MF120 was 2.7 dB less than that of MF40 due to the difference in internal flow. It has been quantitatively estimated that the deceleration in the relative velocity contributed to the improvement in the overall performance.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.41-46
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• 2002

Flow field downstream of an inducer was measured to see the flow and performance characteristics of a turbopump inducer. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow - without interaction of the inducer and the volute. A conventional 3-hole probe was used to measure the flow. At inducer exit axial component of absolute velocity decreased on hub region with decrease in flow rate. Tangential velocity component static pressure, and total pressure increased from hub to tip. Relative flow angle from tangential direction was a little higher than outlet blade angle at flow coefficient $\varphi$=0.087 and 0.073. Dynamic pressure was $53\%$ of the mean total pressure at inducer exit at $\varphi$=0.073.

• 한국유체기계학회 논문집
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• 제6권4호
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• pp.38-44
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• 2003

Flow field downstream of an inducer was measured to see the flow and performance characteristics of a turbopump inducer. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow - without interaction of the inducer and the volute. A conventional 3-hole probe was used to measure the flow. At inducer exit, axial component of absolute velocity decreased on hub region with decrease in flow rate. Tangential velocity component, static pressure, and total pressure increased from hub to tip. Relative flow angle from tangential direction was a little higher than outlet blade angle at flow coefficient ${\phi}=0.087$ and 0.073. Dynamic pressure was $53\%$ of the mean total pressure at inducer exit at ${\phi}=0.073$.

• 한국가시화정보학회지
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• 제22권2호
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• pp.55-62
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• 2024

Using an internal flow noise test bench, this study investigates the variation in internal flow noise at the inlet and outlet monitoring points of a DN100 T-junction pipe under different flow velocities. Results indicate that with increasing flow velocity, both the sound pressure level and total sound pressure level at the inlet and outlet monitoring points increase. The highest total sound pressure level is observed at the vertical outlet monitoring point B, followed by the horizontal inlet monitoring point A, with the lowest at the horizontal outlet monitoring point C. At a constant flow velocity, the sound pressure level at the inlet and outlet points initially increases and then decreases as frequency increases.

• 설비공학논문집
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• 제27권7호
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• pp.344-353
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• 2015

In the present study the characteristics of turbulent oscillatory flows in a square-sectional $180^{\circ}$curved duct were investigated experimentally. A series of experiments for air flow were conducted to measure axial velocity profiles, secondary flow velocity profiles and pressure distributions. The measurements were made by a Laser Doppler Velocimeter (LDV) system with a data acquisition and processing system which includes Rotating Machinery Resolve (RMR) and PHASE software. The results from the experiment are summarized as follows. (1) The maximum velocity moved toward the outer wall from the region of a bend angle of $30^{\circ}$. The velocity distribution had a positive value extended over the total phase in the region of a bend angle of $150^{\circ}$. (2) Secondary flows were generally proportional to the velocity of the main flow. The intensity of the secondary flow was about 25% as much as that in the axial direction. (3) Pressure distributions were effects of the oscillatory Dean number and respective region.

• 한국안전학회지
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• 제35권6호
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• pp.32-45
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• 2020

The problem of determining the discharge rates of gases from pressurized vessels through pressure relief devices was dealt with comprehensively. First, starting from basic fluid flow equations, detailed modeling procedures were presented for isentropic nozzle flows and frictional flows in a pipe, respectively. Meanwhile, physical explanations were given to choking phenomena in terms of the acoustic velocity, elucidating the widespread use of Mach numbers in gas flow models. Frictional flows in a pipe were classified into adiabatic, isothermal, and general flows according to the heat transfer situation around the pipe, but the adiabatic flow model was recommended suitable for gas discharge through pressure relief devices. Next, for the isentropic nozzle flow followed by adiabatic frictional flow in the pipe, two equations were established for two unknowns that consist of the Mach numbers at the inlet and outlet of the pipe, respectively. The relationship among the ratio of downstream reservoir pressure to upstream pressure, mass flux, and total frictional loss coefficient was shown in various forms of MATLAB 2-D plot, 3-D surface plot and contour plot. Then, the profiles of gas properties and velocity in the pipe section were traced. A method to quantify the relationship among the pressure head, velocity head, and total friction loss was presented, and was used in inferring that the rapid increase in gas velocity in the region approaching the choked flow at the pipe outlet is attributed to the conversion of internal energy to kinetic energy. Finally, the Levenspiel chart reproduced in this work was compared with the Lapple chart used in API 521 Standatd.

• International Journal of Fluid Machinery and Systems
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• 제2권3호
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• pp.223-231
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• 2009

Experimental investigations were conducted for the internal flows of the axial flow stator and diagonal flow rotor. Corner separation near the hub surface and the suction surface of stator blade are mainly focused on. For the design flow rate, the values of the axial velocity and the total pressure at stator outlet decrease between near the suction surface and near the hub surface by the influence of corner wall. For the flow rate of 80-90% of the design flow rate, the corner separation of the stator between the suction surface and the hub surface is observed, which becomes widely spread for 80% of the design flow rate. At rotor outlet for 81% of the design flow rate, the low axial velocity region grows between near the suction surface of rotor and the casing surface because of the tip leakage flow of the rotor.