• Journal of the Korean Society of Visualization
• /
• v.16 no.2
• /
• pp.45-52
• /
• 2018

The tangential and axial cyclones were fabricated using a 3D printer and the total collecting efficiency, cut-diameter, and pressure drop characteristics of the two types of cyclones with the same inlet area were investigated experimentally. The results show that the total collecting efficiency tends to increase as the inlet velocity increases. However, at a 20m/s condition of the tangential cyclone, the collected particles were re-entrained to the ascending vortex flow, resulting in a decrease of the total collecting efficiency. In the axial cyclone, the cross-sectional area is designed to increase at the inlet and the velocity is reduced, so that the re-entrainment effect does not appear in this study. The pressure loss of the tangential cyclone was larger than that of the axial cyclone. The cut-diameter tends to decrease with increasing the inlet velocity in two types of cyclones, except for the 20m/s condition of the tangential cyclone.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.11
• /
• pp.1618-1629
• /
• 2003

The effects of the interaction between flow field and heat transfer caused by the longitudinal vortices are experimentally investigated using a five hole probe and a transient liquid crystal technique. The test facility consists of a wind tunnel with vortex generators protruding from a bottom surface and a mesh heater. In order to control the strength of the longitudinal vortices, the angle of attack of vortex generators used in the present experiment is 20$^{\circ}$, and the spacing between the vortex generators is 25mm. The height and cord length of the vortex generator is 20mm and 50mm, respectively. Three-component mean velocity measurements are made using a f-hole probe system, and the surface temperature distribution is measured by the hue capturing method using a transient liquid crystal technique. The transient liquid crystal technique in measuring heat transfer has become one of the most effective ways in determining the full surface distributions of heat transfer coefficients. The key point of this technique is to convert the inlet flow temperature into an exponential temperature profile using the mesh heater set up in the wind tunnel. The conclusions obtained in the present experiment are as follows: The two maximum heat transfer values exist over the whole domain, and as the longitudinal vortices move to the farther downstream region, these peak values show the decreasing trends. These trends are also observed in the experimental results of other researchers to have used the uniform heat flux method.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.9
• /
• pp.731-737
• /
• 2014

A vortex chamber is a simple device that separates compressed gas into a high-temperature stream and a low-temperature stream. It is increasing in popularity as a next-generation heat exchanger, but the flow physics associated with it is not yet well understood. In the present study, both experimental and numerical analyses were performed to investigate the temperature separation phenomenon inside the vortex chamber. Static pressures and temperatures were measured using high-sensitivity pressure transducers and thermocouples, respectively. Computational fluid dynamics was applied to simulate 3D unsteady compressible flows. The simulation results showed that the temperature separation is strongly dependent on the diameter of the vortex chamber and the supply pressure at the inlet ports, where the latter is closely related to the viscous work. The previous concept of a pressure gradient wave may not be a reasoning for temperature separation phenomenon inside the vortex chamber.

• Journal of Aerospace System Engineering
• /
• v.14 no.3
• /
• pp.1-9
• /
• 2020

In this paper, the effects of the delta winglet vortex generator, the airfoil vortex generator and the guide vanes on the friction factor and the Colburn factor in the fin-tube flow were studied. The vortex generator and guide vane were non-dimensionalized based on the channel height and tube diameter, and locations were selected according to the authors' suggestions. The Reynolds number based on the inlet velocity and the tube diameter was selected in the range of 1400-8000. As a result, the friction factor resulted in a 4.7% decrease in guide vanes at the Reynolds number 8000 over the conventional fin-tube, and the Colburn factor resulted in a 33% increase in the delta winglet vortex generator at the Reynolds number 3800 over the conventional fin-tube.

• 한국연소학회:학술대회논문집
• /
• 2001.06a
• /
• pp.67-74
• /
• 2001

The annular-reverse combustor was designed for APU combustor and a three dimensional analysis for reactive flow in the combustor was performed. At the same time, the experimental work was performed in KARl combustor test facility. In this study we found out that tangential swirl type combustor is good for flame holding than single vortex type combustor. The flame tube main hole size and relative position are very important parameters for combustor general performance. The ignition characteristics are strongly depend on the air fuel ratio with combustor inlet volume flow ratio.

• Journal of Korean Society for Atmospheric Environment
• /
• v.12 no.1
• /
• pp.43-53
• /
• 1996

Numerical simulation was performed for the 3-dimensional flow filed of gas and particle phase for cyclone dust collector. FVM(Finite Volume Method) was employed for gas phase. The flow was solved suing the k-.varepsilon. epsilon turbulence model. The particle exit at the bottom of the cone was treated as a solid wall in this model because the gas flow through the effective dust exit is usually insignificant. The major parameters considered in this study was vortex finder diameter, effective dust exit diameterm vortex finder length, inlet type for dimension performance. Particle trajectory calculations were made for three different, particle sizes of 1, 25 and 50 .mu.m. The results obtained from this study give some physical insight of dust particle collection mechanism together with the indication of the collection efficiency. The simulation results were in generally good agreement with empirical knowledge. The application of this kind of computer program looks promising as a potential tool for the design of cyclone and determination of optimum operating condition.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.583-589
• /
• 2004

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fan has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control of the size and position, is the important cause of performance decrease. In this study, experiments are carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to research the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spital, which is the important factor haying an effect on it.

• Particle and aerosol research
• /
• v.10 no.4
• /
• pp.155-162
• /
• 2014

The internal temperature will change depending on operation conditions and material of cyclone dust collector. This study compares the results of collection efficiency and temperature distribution on the different heat flux at wall of dust collector. The previous researcher's experiment results were used to confirm the reliability of CFD(Computational Fluid Dynamics) model. Based on this verified CFD model, we extended the analysis on the cyclone dust collectors. In CFD study, we used RNG k-epsilon model for analysis of turbulence flow, fluid is air, the velocity at inlet is 10 m/s, the temperature of air is $600^{\circ}C$. Because of the difference of outer vortex and inner vortex temperature, the collection efficiency will reduce with the increase of heat flux, showed the highest collection efficiency at heat insulation.

• Journal of computational fluids engineering
• /
• v.13 no.2
• /
• pp.14-19
• /
• 2008

Effects of the Reynolds and Knudsen numbers on a micro-viscous pump are studied by using a Navier-Stokes code based on a finite volume method. The micro viscous pump consists of a circular rotor and a two-dimensional channel. The channel walls are treated by using a slip velocity model. The Reynolds number is studied in the range of $0.1{\sim}50$. The Knudsen number varies from 0.01 to 0.1. Numerical solutions show that the pump works efficiently when two counter rotating vortices formed on both sides of the rotor have the same size and intensity. As the Reynolds number increases, the size and intensity of the vortex on the inlet side of the pump decrease. It disappears when the Reynolds number is larger than about Re=20. The characteristics of the performance of the pump is shown to deteriorate, in terms of mean velocity and pressure rise, as the Reynolds number increases. The Knudsen number shows a different effect on the characteristics of the pump. As it increases, the mean velocity and pressure rise decrease but the characteristics of the vortex flow remains unchanged, unlike the effect of Reynolds number.

• Particle and aerosol research
• /
• v.11 no.2
• /
• pp.47-55
• /
• 2015

This study compares the results of collection efficiency of difference gas temperature in cyclone dust collector. The previous researcher's experiment results were used to confirm the reliability of CFD(Computational Fluid Dynamics) model. Based on this verified CFD model, we extended the analysis on the cyclone dust collectors. In CFD study, we used RNG k-epsilon model for analysis of turbulence flow, fluid is air, the velocity at inlet is 10 m/s, the temperature of air is $20^{\circ}C$, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $600^{\circ}C$ and $1000^{\circ}C$. As the temperature decreases, the average velocity of outer vortex and collection efficiency is increased, showed the highest collection efficiency at $20^{\circ}C$. It can be inferred smooth flow in cyclone dust collector is difficult because air viscosity increases as temperature increases. The power required at $1000^{\circ}C$ is almost 18 times greater than that of $20^{\circ}C$ to get the similar collection efficiency.