• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.12
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• pp.979-985
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• 2007

Spray combustion characteristics of the conducting fuel electrospray has been studied for clean combustion technology. The electrospraying multiplexed system which can maintain the characteristics of the cone-jet mode is able to obtain charged micro droplets with high flow rate. In addition, they have monodisperse distribution during operating the electrospray in the cone-jet mode. The multiplexed grooved nozzle system with the extractor was applied to this experimental device set up. The stable grooved mode can be generated by the grooved nozzle and this electrospray system was applied to the diffusion combustion. It is the first step to discover the diffusion combustion characteristics of the electrospray, In case of the single grooved nozzle electrospray the diffusion flames are occurred at each Jet of grooved mode and they are quite stable. The exhaust gas analysis was indicated that there is the critical point which can make very stable diffusion combustion

• Fashion & Textile Research Journal
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• v.15 no.3
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• pp.437-443
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• 2013

This paper investigates the physical properties of aramid and aramid/nylon hybrid air jet textured filaments for protective garments relative to ATY nozzle diameters. Three types of para-aramids(840d, 1,000d, 1,500d) and nylon(420d) filaments were prepared; in addition, 840d aramid/420d nylon and three kinds of aramid filaments were texturized with a variation of air jet nozzle diameters(0.6, 0.75, 1 and 1.2 mm) on the AIKI air jet texturing machine. The measured physical properties of 16 specimens are as follows. The linear densities of aramid and aramid/nylon hybrid ATY increased with a larger nozzle diameter. The tenacity and initial modulus of aramid and hybrid ATY linearly decreased with a larger nozzle diameter; in addition, the breaking strain increased with the nozzle diameter. The dry and wet thermal shrinkage of hybrid ATY increased with a larger nozzle diameter from 0.6 mm to 1 mm and then decreased at a nozzle diameter of 1.2 mm (which seems to be a critical diameter). The wet and dry thermal shrinkage of aramid/nylon hybrid ATY are influenced by the nylon part of the hybrid yarns because the wet and dry thermal shrinkages of aramid ATY are less than 0.2%. The instabilities of aramid and aramid/nylon hybrid ATY were not influenced by the air jet nozzle diameter; however, they increased with the linear density of ATY.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.774-779
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• 2008

An experimental study on the micro-supersonic jet flow fields has been carried out. A sonic nozzle of 440 ${\mu}m$-exit diameter and a Laval nozzle of 800 ${\mu}m$ exit diameter with the nozzle exit Mach number 2.0 were fabricated by stretching a micro Pyrex glass tube for the present experiments. Schlieren flow visualization and Pitot pressure distribution of the jet flow field were obtained. Representative characteristics of the jet flow fields such as, supersonic length, jet core length, similarity of the velocity field, and jet spreading rates, have been observed. All the results were compared to previous observations of larger supersonic jets of higher Reynolds numbers, and it was found that overall characteristics of the micro supersonic jet are qualitatively similar as those of the higher Reynolds number jets, except the jet core length and the jet spreading rate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1346-1354
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• 2001

The heat transfer characteristics off swirling air jet impinging on a heated flat plate have been investigated experimentally. The main object is to enhance the heat transfer rate by increasing turbulence intensity of impinging jet with a specially designed swirl generator. The mean velocity and turbulent intensity profiles of swirling jet were measured using a hot-wire anemomety. The temperature distribution on the heated flat surface was measured with thermocouples. As a result the swirl effect on the local heat transfer rate on the impinging plate is confined mainly in the small nozzle-to-plate spacings such as L/D<3 at the stagnation region. For small nozzle-to-plate spacings, the local heat transfer in the stagnation region is enhanced from the increased turbulence intensity due to swirl motion, compared with the conventional axisymmetric impinging jet without swirl. For example, the local Nusselt number of swirling jet with swirl number Sw=0.75 and Sw=1 is about 9.7-76% higher than that of conventional impinging jet at the radial location of R/D=0.5. With the increase of the nozzle-to-plate distance, the stagnation heat transfer rate is decreased due to the diminishing axial momentum of the swirling jet. However, the swirling impinging jet for all nozzle-to-plate spacings tested in this study does not enhance the average heat transfer rate.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.1
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• pp.31-35
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• 2016

For reaction injection molding (RIM) polyurethane was mixed in the mixing head by impingement mixing, injected into the mold, and cured quickly, as soon as the mold is filled. The shape of the nozzle in the mixing head is critical to improve the quality of polyurethane. To achieve homogeneous mixing, an intensive turbulence energy in the mixing nozzle is essential. In this study, a mixing nozzle for RIM was designed, and mixing efficiency was investigated based on experiment. Experiments were conducted with different combinations of nozzle tips and exit diameter to measure the mixing efficiency by measuring jet force and investigating mixing image with high speed camera. Jet force increased gradually and reaches steady state conditions. The jet force depended on shape of nozzle tip and outlet sizes. These results suggest that optimized nozzle configurations are necessary for high efficiency mixing with RIM.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.17-22
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• 2002

A numerical solution procedure has been developed to analyze the flow field resulted from the injection of a transverse jet through the divergent flap of a 2DCD nozzle for thrust vector control. The formulation employs the compressible Navier-Stokes equations in conservation law form and a two equation $\kappa-\omega$ turbulence model. Detailed numerical results are presented in this paper for the 2DCD nozzle over a range of secondary to primary injection mass flow ratios and nozzle pressure ratios.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4013-4026
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• 1996

A numerical simulation has been carried out for the jet impinging on a flat plate and a semi-circular concave surface. In this computation finite volume method was employed to solve the full Navier-Stokes equation based on a non-orthogonal coordinate with non staggered variable arrangement. The standard k-.epsilon. turbulent model and low Reynolds number k-.epsilon. model(Launder-Sharmar model) with Yap's correction were adapted. The accuracy of the numerical calculations were compared with various experimental data reported in the literature and showed good predictions of centerline velocity decay, wall pressure distribution and skin friction. For the jet impingement on a semi-circular concave surface, potential core length was calculated for two different nozzle(round edged nozzle and rectangular edged nozzle) to consider effects of the nozzle shape. The result showed that round edged nozzle had longer potential core length than rectangular edged nozzle for the same condition. Heat transfer rate along the concave surface with constant heat flux was calculated for various nozzle exit to surface distance(H/B) in the condition of same jet velocity. The maximum local Nusselt number at the stagnation point occurred at H/B = 8 where the centerline turbulent intensity had maximum value. The predicted Nusselt number showed good agreement with the experimental data at the stagnation point. However heat transfer predictions along the downstream were underestimated. This results suggest that the improved turbulence modeling is required.

• Journal of the Korean Graphic Arts Communication Society
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• v.28 no.1
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• pp.51-63
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• 2010

Ink-jet is part of the non impact printing that shooting the ink drop from the nozzle to paper. It is very silence and express good color. There are two types of printing that continuous and drop on demand. But drop on demand process is becoming the mainstream. these days, LCD, PDP is passed more than semiconductor industry. And we expect organic EL, FED as a next display. But product equipment, main component and technology have a gap between an advanced country and us nevertheless physical development. Expecially, previous process part is depended on imports. Ink-jet printing technology that there isn't complicated photo lithography process is attracted, so ink-jet printing resolution is more embossed. But there were not many of ink-jet resolution thesis but ink-jet head or nozzle. Because, to out of the ink from the nozzle is unseeable and hard to experiment. Therefore this thesis was experimented and simulated how can ink-jet printer improved resolution by flow-3d simulation package program.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.323-328
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• 2001

Supersonic coaxial, axisymmetric, jets issuing from various kinds of dual coaxial nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with an impinging angle in the jet axis of the annular jets were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio produces longer supersonic length of the dual, coaxial jet.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.450-457
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• 2016

While many studies on the heat transfer effect of an impinging jet have been published, most studies focus on the downward impinging jet. This study investigates the impinging jet heat transfer phenomenon when water at a temperature of $24^{\circ}C$ impinges on the downward isothermal circular plate at 60, 70, and $80^{\circ}C$ and when the upward round jet nozzle is 4, 6, and 8 mm diameter with a flow rate 3.6, 4.6, and 5.6 L/min, respectively, and when the ratio of the nozzle clearance/nozzle diameter (H/D) is 1. The results showed that, as the nozzle diameter decreases, the heat transfer coefficient increases at a constant flow rate. The correlation equation of $Nu_r$, $Pr_r$, and $Re_{jg}$ is obtained in the impinging and constant velocity flow region $(Nu_r/Pr^{0.4}_r)Dr=4.6[Re_{jg}(r/R_c)Dr]^{0.8}$ at all flow rates, in the deceleration and falling flow regions $(Nu_r/Pr^{0.4}_r)Dr=42.7{\mid}Re_{jg}(r/R_c)Dr-345.7{\mid}^{0.3}$ at 3.6 L/min, $(Nu_r/Pr^{0.4}_r)Dr=92.4{\mid}Re_{jg}(r/R_c)Dr-16.8{\mid}^{0.2}$ at 4.6 L/min, and $(Nu_r/Pr^{0.4}_r)Dr=322.4{\mid}Re_{jg}(r/R_c)Dr-536.2{\mid}^{0.01}$ at 5.6 L/min.