• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.252-261
• /
• 1991

A particle trajectory model to simulate two-phase particle-laden crossjets into two-dimensional horizontal free stream has been developed to study the variations of the jet trajectories and velocity variations of the gaseous and the particulate phases. The following conclusions may be drawn from the predicted results, which are in agreement with experimental observations. The penetration of the two-phase jet in a crossflow is greater than that of the single-phase jet. The penetration of particles into the free stream increases with increasing particle size, solids-gas loading ratio and carrier gas to free stream velocity ratio at the jet exit. When the particle size is large, the solid particles separate from the carrier gas , while the particles are completely suspended in the carrier gas for the case of small size particles. As the particle to carrier gas velocity ratio at the jet exit is less than unity, the particles in the vicinity of the jet exit are accelerated by the carrier gas. As the injection angle is increased, the difference of the particle trajectory from that of the pure gas becomes larger. Therefore, it can be concluded that the velocities and trajectories of the particle-laden jets in a crossflow change depending on the solids-gas loading ratio, particle size, carrier gas to free stream velocity ratio and particle to gas velocity ratio at the jet exit.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.426-431
• /
• 2001

This paper experimentally investigates the characteristics of dual coaxial jet issuing from inner supersonic nozzle and four kinds of outer converging nozzle of 40, 50, $60^{\circ}$ and $70^{\circ}$ in outer ejection angle. The pressure ratio of the stagnation to the exit ambient pressures in the inner supersonic nozzle of constant expansion rate is 7.5, which is corresponded to the condition of a slightly underexpanded, and that of outer nozzle is 4.0. Flow visualizations by using of shadowgraph method, impact pressure and centerline static pressure measurements are presented. It is found that the jet structure is changed significantly by the variation of outer nozzle ejection angle. Impact pressure level is lower and undulation of static pressure is higher, as the injection angle of outer jet increases.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2017.11a
• /
• pp.232-233
• /
• 2017

In this research, tunnel stern was applied on the asymmetric high-speed catamaran to evaluate vessel's hydrodynamic performance by numerical method, and the tunnel stern types are distinguished by angle of inclination of tunnel exit region into 3cases ($0^{\circ}$, $3^{\circ}$ and $6^{\circ}$). Consequently, it is confirmed that the total resistances of tunnel stern which have $0^{\circ}$ of inclination are lower about 4.8-17.9% than the bare hull in the wide speed range, but those of $3^{\circ}$ and $6^{\circ}$ of inclination tunnel stern are higher than bare hull about 5-14% and 5-29%, respectively. On the other hand, trim angles of $0^{\circ}$ of inclination tunnel stern show similar trend with those of bare hull in whole ranges of FnV but those of $3^{\circ}$ and $6^{\circ}$ of inclination tunnel stern are stabilized and declined respectively after FnV=1.54. These phenomena indicated that increasing angle of inclination of tunnel exit region had negative influence on resistance performance, however, it could make vessel's operation performance better than bare hull.

• International Journal of Fluid Machinery and Systems
• /
• v.2 no.1
• /
• pp.13-20
• /
• 2009

The effects of positively bowed blade on the aerodynamic performance of annular compressor cascades with large camber angle were experimentally investigated under different incidences. The distributions of the exit total pressure loss and secondary flow vectors of compressor cascades were analyzed. The static pressure was measured by tapping on the cascade surfaces, and the ink-trace flow visualizations were conducted. The results show that the value of the optimum bowed angle and optimum bowed height decrease because of the increased losses at the mid-span with the increase of the caber angle. The C-shape static pressure distribution along the radial direction exists on the suction surface of the straight cascade with large r camber angles. When bowed blade is applied, the larger bowed angle and larger bowed height will further enhance the accumulation of the low-energy fluid at the mid-span, thus deteriorate the flow behavior. Under $60^{\circ}$ camber angle, flow behavior near the end-wall region of some bowed cascades even deteriorates instead of improving because the blockage of the separated flow near the mid-span keeps the low-energy fluid near the end-walls from moving towards the mid-span region, and as a result, a rapid augmentation of the total loss is easy to take place under large bowed angle. With the increase of camber angle, the choice range of bowed angle corresponding to the best performance in different incidences become narrower.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.10
• /
• pp.1472-1479
• /
• 2003

An attempt to reduce supersonic jet noise is carried out by using two steady microjets in a round jet. The jet is issued from a round sonic nozzle with an exit diameter of 10 mm. Two micro-nozzles with an inside diameter of 1 mm each are installed on the exit plane at an angle of 45 relative to the main jet axis. Far-field noise was measured at 40 diameters off the jet axis. The angle between a microphone and the jet axis is 30 or 90$^{\circ}$. For an injection rate of 4-6% of the main jet, screech tones were completely suppressed by the microjets. The reduction in the overall sound pressure levels were 2.4 and 2.7 dB for 90 and 30 measuring directions, respectively. However, the enhancement of mixing/spreading of the jet by the microjet was negligible. The reduction of noise is probably due to distorted shock cell structures and/or deformed large scale vortical structures by the microjets.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.4
• /
• pp.456-466
• /
• 2004

An experimental study has been conducted to investigate the flow and heat/mass transfer characteristics within a rectangular film cooling hole of normal injection angle for various blowing ratios and Reynolds numbers. The results are compared with those for the square hole. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code (FLUENT). The heat/mass transfer around the hole entrance region is enhanced considerably due to the reattachment of separated flow and the vortices generated within the hole. At the hole exit region, the heat/mass transfer increases because the main flow induces a secondary vortex. It is observed that the overall heat/mass transfer characteristics are similar to those for the square hole. However, the different heat/mass transfer patterns come out due to increased aspect ratio. Unlike the square hole, the heat/mass transfer on the trailing edge side of hole entrance region has two peak regions due to split flow reattachment, and heat/mass transfer on the hole exit region is less sensitive to the blowing ratios than the square hole.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1031-1036
• /
• 2009

This study is intended to identify how quick disconnect coupling which connects with refrigerant piping of air-conditioner using R-22 refrigerant has effect on characteristics of flux. in the case where the air-conditioner installs utilizes quick disconnect coupling, COP has an effect on the quantity of cooling load because of changing flow rate and physical properties of refrigerant which flow into an entrance of expansion valve from coupling. Variation of flow rate can be regulated by changing expansion-contraction angle; $\alpha$ of an entrance and an exit of coupling. In this study, quick disconnect coupling is presented flow of coupling by using FLUENT as heat flow program. To have an effect on the expansion entrance valve, and by changing expansion-contraction angle; $\alpha$ of an entrance and an exit

• International Journal of Aeronautical and Space Sciences
• /
• v.12 no.3
• /
• pp.296-304
• /
• 2011

In order to design a shear coaxial injector of solid particles with water, basic experiments on a particle laden jet are necessary. The purpose of the present study is to understand the effect of particle loading ratio on the particle spray characteristics (i.e. spreading angle, distribution of particle number density, velocity profiles, and particle developing region length). Hydro-reactive Al2O3 particles with a primary particle diameter of 35~50 ${\mu}m$ are used in this experiment. An automated particle feeder was designed to supply constant particle mass flowrates. Air is used as the carrier gas. To determine the air velocity at the orifice exit, tracers (aluminum oxide, 0.5~2 ${\mu}m$ primary diameter) are also supplied by a tracer feeder. A plain orifice type injector with 3 mm diameter, and 20 mm length was adopted. Particle image velocimetry is used to measure the mean and fluctuating velocity components along the axial and radial directions.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.809-814
• /
• 2009

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.9-21
• /
• 2000

In this study, the characteristics of high-pressure swirl injector have been studied using a commercial CFD code, STAR-CD and experiment to investigate the effect of the length of orifice and swirl port on the spray characteristics. Influences of swirl port angle and initial conditions have also been examined in terms of penetration depth and Sauter`s mean diameter. Computed results of the spray characteristics are compared with experimental results. The results show that the tangential velocity at the nozzle exit decreases, but the axial velocity increases as swirl port angle is increased. Hence, the static flow rate increases, but the initial spray angle decreases with increasing the swirl port angle. It is also shown that the values of the initial SMD used as input data for spray simulation influences the penetration depth and SMD. The spray pattern from the present numerical simulation agrees well with experimental result.