• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.688-694
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• 2012

A study on the effect of engine nozzle configuration on the engine plume Infra-red (IR) signature characteristics is performed. Configuration design of an engine nozzle with high aspect ratio to reduce IR signature level and a cylindrical nozzle which is typically used for conventional aircraft which does not require IR signature reduction is performed. And CFD analysis for the two nozzles is performed to compare the flowfields characteristics of the two nozzles. Finally IR signature analysis for the two nozzles is accomplished to calculate the total intensity level at mid-wave infra-red and investigate the differences of IR signature characteristics between the two nozzles.

• Journal of the Korean Society of Combustion
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• v.11 no.2
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• pp.1-6
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• 2006

This report presents a study of the development of an advanced coal nozzle used in burners to reduce unburned carbon (UBC) in a tangential coal-fired boiler. To understand the mechanism of UBC reduction, experiments using conventional burners were carried out to evaluate the effects of air injection velocity, coal fineness and over fired air (OFA) on combustion efficiency. It was confirmed that ignition of pulverized coal particles close to the burner is helpful toward the complete burn of residual carbon in fly ash. These efforts indicated the additional results that UBC was strongly dependent on the primary air velocity and coal fineness; especially that UBC dramatically decreased when the weight fraction of pulverized coal under $75{\mu}m$ was over 85 %. New coal nozzles, modified from conventional nozzles, were prepared and tested to improve the combustion efficiency. Some of these nozzles offered relatively lower unburned carbon than those of conventional burners and are referred to as HPFS (High Performance Flame Stability) coal nozzles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.899-905
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• 2009

Most supersonic-flow test facility has axisymmetric nozzles or two-dimensional symmetric nozzles. Compared to these nozzles, a two-dimensional asymmetric nozzle has advantages of reducing low cost for various Mach number testing and undesirable flow structure such as shock wave reflection because the nozzle part can be directly connected to the test section part in this type of nozzle. The two-dimensional asymmetric nozzle, which was Mach number 2, was designed for supersonic combustion experiment. And it was verified with the numerical analysis and visualization of Mach wave. This study suggested the practical method for design and verification of supersonic two dimensional asymmetric nozzles.

• Journal of Biomedical Engineering Research
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• v.26 no.3
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• pp.157-161
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• 2005

Direct injection of a fibrinolytic agent to the intraarterial thrombosis may increase the effectiveness of thrombolysis by enhancing the permeation of thrombolytic agents into the blood clot. Permeation of fibrinolytic agents into a clot is influenced by the surface pressure, which is determined by the injection velocity of fibrinolytic agents. In order to calculate the pressure distribution on the clot surface for different jet velocities (1, 3, 5 m/sec) and nozzle arrangements (1, 9, 17 nozzles), computational fluid dynamic methods were used. Thrombolysis of a clot was mathematically modeled based on the pressure and lysis front velocity relationship. Direct injection of a thrombolytic agent increased the speed of thrombolysis significantly and the effectiveness was increased as the ejecting velocity increased. The nine nozzles model showed about $20\%$ increase of the lysed volume, and the one and seventeen nozzles models did not show significant differences. The wall shear stress decreased as the number of nozzles increased, and the wall shear stress in most vessel wall was lower than 25 Pa. The results implied that thrombolysis could be accelerated by direct injection of a drug with the moderate velocity without damaging the blood vessel wall.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.28-36
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• 2000

Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short, An investigation into various spray characteristics from different holes of VCO(Valve Covered Orifice) nozzles was performed and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from multi hole nozzles were measured with back light imaging while the sprays from the other holes are covered by a purpose-built nozzle cap. The investigation manifestly reveals the different spray patterns at the beginning of injection produced by VCO nozzles can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at 0.9∼1.0ms from the start of injection.

• Korean Journal of Computational Design and Engineering
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• v.22 no.1
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• pp.37-43
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• 2017

3D printing techniques can be used in various application fields and many researches have been reported. FDM (Fused Deposition modeling) can make multi-material or multi-color models with the simultaneous use of two or more filaments. In a dual-nozzle FDM printers, while the active nozzle is working, the remaining nozzle will be idle. The remaining molten resins inside an idle nozzle can ooze out unwantedly. The spill over from the resting nozzle produces unwanted remaining on the fabricated product. In this research, we suggest a method for optimizing building position of a model to minimize the unwanted spill-over that could possibly contaminate the final product. The method is based on minimizing the two intersection volumes. The first intersection volume is obtained by intersecting the volume defined by the first material and the Minkowski sum between the volume of the first material and the vector obtained by subtracting the center point of the first nozzle from the center point of the second nozzle. The second intersection volume can be obtained by reversing the role of the first and second volumes and nozzles. Some results obtained from the implementation using the Parasolid (Siemens) geometric modeling kernel is presented.

• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1222-1235
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• 2004

This study examines the influence of geometry on the internal flow and macroscopic behavior of the spray in Diesel nozzles. For this investigation, two bi-orifice nozzles were employed: one cylindrical and one conical. The first step is to use a non-destructive characterization method which is based on the production of silicone moulds so that the precise internal geometry of the two nozzles can be measured. At this stage the nozzles have been characterized dimensionally and therefore the internal flow can be studied using CFD calculations. The results gained from this experiment make it possible also to ascertain the critical cavitation conditions. Once the critical cavitation conditions have been identified, the macroscopic parameters of the spray can be studied in both cavitating and non-cavitating conditions using a test rig pressurized with nitrogen and with the help of a image acquisition system and image processing software. Consequently, research can be carried out to determine the influence that cavitation has on macroscopic spray behavior. From the point of view of the spray macroscopic behavior, the main conclusion of the paper is that cavitation leads to an increment of the spray cone angle. On the other hand, from the point of view of the internal flow, the hole outlet velocity increases when cavitation appears. This phenomenon can be explained by the reduction in the cross section of the liquid phase in the outlet section of the hole.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1005-1012
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• 2011

The purpose of this study was to investigate the internal nozzle flow and cavitation characteristics numerically in both circular and elliptical nozzles. The program FLUENT 6.2 was used to perform the numerical simulation of the cavitating flow in the nozzles. A comparison was made between the cavitation shapes predicted numerically and those found experimentally in order to validate the numerical solution. This study showed that the cavitation in the circular nozzle had a cylindrical shape that was symmetrical with the nozzle axis. However, the cavitation in the elliptical nozzles had a horseshoe-like shape. In addition, the radial velocity distribution varied between the major and the minor axis planes when the working fluid was flowing into the inlet.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.553-559
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• 2019

Various types of nozzles have been used to cope with fire in ships. However, in Korea, precise nozzles that perform fine spraying function are required for fire fighting in case of fire in a ship, and most of these nozzles depend on imports. Therefore, in this study, we developed various types of nozzles to develop the water spray nozzle for evolving fire in the engine room of the ship, and developed an optimal nozzle through flow analysis and fire test. For this purpose, we selected the materials that can satisfy the characteristics of existing nozzle materials and developed the design technology and processing technology in the nozzle considering fluid flow to achieve optimal water spraying performance. In order to develop an optimal nozzle, the flow through the finite element analysis was first analyzed and the nozzle was manufactured. As a result of flow analysis of the developed nozzle, the maximum velocity at the outlets of four holes at 0.3 MPa was about 3m/s and about 0.15 MPa. In addition, when the pressure at the inlet was 1.8 MPa, it showed the outlet speed of about 18m/s and a pressure of 1.2 MPa.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.2
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• pp.80-88
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• 2022

A systematic experimental study is carried out for the fire fighting monitor nozzle of 65A diameter to design and manufacture a new nozzle with better water spray performance than available domestic nozzles. The nozzle inlet pressure, flow rate and reach for the discharged water from the nozzle are measured by utilizing the experimental facility consisting of two pumps and piping system with a flow meter and pressure gauges. It was found that the baffle position and baffle head chamfering were the most sensitive design factors to be remarkably changed in the flow rate of the discharged water. Also, It was confirmed that the baffle position and the water exit area had the significant effect on the change in reach distance. The results obtained from this study are expected to be used effectively to design new nozzles with excellent spray performances and also to validate numerical analysis results for evaluating the water spray performance of fire fighting monitor nozzles.