• Journal of Biosystems Engineering
• /
• v.18 no.2
• /
• pp.100-109
• /
• 1993

The aim of this study was to provide the reasonable data for design of the nozzle which produces finer droplets on the same level of the effective travel distance or which transports droplets to the farther target on the reasonable atomization in comparison with the commercial nozzles being used much in Korean rural areas. Newly designed twin-fluid atomizers with some commercial nozzles were tested in this study, and their results were as follows : 1. The characteristics of the spray deposit distribution of No.1 nozzles for farther target were nearly same in the near or nearer travel distance less than 8m. Therefore it was reasonable to combine the characteristics of the spray deposit distributions of No.2 and No.3 nozzles to those of No.1 nozzle. 2. The effective travel distance was increased with increase of the sectional area of the jet ligament, and the maximum effective travel distance was reached to about 17m. 3. The droplet size was increased with increase of the sectional area of the jet ligament, and the maximum droplet size was produced in the front of the point of the maximum spray deposit distribution. 4. The atomization was excellent in the twin-fluid atomizer in comparison with the hydraulic atomizer and also the effective travel distances were nearly same level in both atomizers.

• Journal of ILASS-Korea
• /
• v.5 no.4
• /
• pp.40-46
• /
• 2000

To understand the basic the structure of the spray field and to obtain the initial conditions for computational models for shear coaxial twin-fluid injectors. the atomization characteristics under different flow and geometric conditions were examined. The spray characteristics such as SMD, mean axial and radial velocities, Dia. of droplets and volume flux with a P.D.P.A. Water and nitrogen gas under atmospheric conditions were used as a test fluids. The drops produced by shear coaxial injectors continue to disintegrate along the spray axis and decrease their sizes. SMD was the maximum at the spray center of spray and decreased with increasing radial distance. The results of this parametric study showed that SMD decreased with increasing gas injection velocity as well as with decreasing liquid injection mass flow rate, The relative velocity between gas and liquid flow played a significant role resulted in decreasing SMD and in spreading the spray. Recessing the liquid orifice resulted decreasing SMD and a spreading the spray. Recess of liquid orifice by 5.0mm showed best atomization characteristics in this experiment. Although drop diameter changes, shear coaxial injector sprays had constant velocity and exhibited a high degree of radial symmetry.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.299-302
• /
• 2002

Characteristics of the twin fluid spray with ultrasonic forcing are examined in order to obtain the high efficiency of cold fog spray of the automatic pest control machine which has been widely used for the equipment cultivation recently. An electrostrictive vibrator of PZT BLT and a magnetostrictive vibrator of ${\pi}type$ with 28 kHz are applied as the ultrasonic transducer. All experiments are made and observed in 4 methods of spray ; a conventional spray method without ultrasonic forcing, an indirect vibration method with ultrasonic forcing, an improving duality method by ultrasonic forced within liquid, and a combined use method with both of the indirect vibration method and the improving quality method. In results, It was clarified that the ultrasonic effects the atomization of spray droplets and its efficiency is about $10{\%}$ and especially much more in the case of the combined use method.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2012.06a
• /
• pp.123-124
• /
• 2012

Effervescent atomizer in which the liquid is ejected from nozzle with bubble caused by gas injection into the liquid is one of twin-fluid atomizers. Effervescent atomizer is operated with the lower injection pressure and the smaller air flow rate when compared with those of other twin-fluid atomizers. In this study, we attempted experiment study to investigate the atomization characteristics of effervescent atomizer related with the internal flow condition. The nozzle was made with acrylic material to investigate the nozzle internal flow. The macroscopic spray analysis was conducted with internal flow images and spray images. Furthermore, SMD was measured by using the laser diffraction method. According to this study, the internal flow condition changed from bubbly flow to annular flow as the air-liquid mass ratio(ALR) increases. At that time, the atomization characteristics were improved.

• Journal of ILASS-Korea
• /
• v.24 no.4
• /
• pp.185-193
• /
• 2019

The effervescent atomizer is one of twin-fluid atomizers that aeration gas enters into bulk liquid and two-phase flow is formed in the mixing section. The effervescent atomizer requires low injection pressure and small amount of aeration gas, as compared to other twin-fluid atomizers. In this study, cold flow test was conducted to investigate the spray characteristics of aerated impinging jets. The present effervescent impinging atomizers were composed of the aerator device and like-on-like doublet impinging atomizer which had different impinging angles. To analyze the spray characteristics such as breakup length and droplet size distribution, the image processing technique was adopted by using instantaneous images at each flow condition. Non-dimensional parameters, induced by the homogeneous flow model, were used to predict the breakup length. The breakup length was decreased with the mixture Reynolds number and impinging angle increasing. The result of droplets showed that the size distribution was axisymmetric about the center of the injector and their diameter tended to decrease with increasing GLR.

• Journal of ILASS-Korea
• /
• v.22 no.2
• /
• pp.96-102
• /
• 2017

In order to reduce the NOx, SCR technology is most suitable. In this study, we focused on studying the injector part of urea-SCR system. When stoichiometric 1 mole of urea is injected, 2 moles of $NH_3$ are created. $NH_3$ causes a SCR reaction by reacting with NOx. However, urea is decomposed by the side reaction of coming out HNCO, deposit formation is formed. In this study, it was to design a nozzle that can spray the optimal spray flow rate. Test nozzle used in this experiment is efferverscent type. The result of the experiment, liquid flow rate was confirmed to be that they are dominated by the exit orifice diameter. The area ratio is defined by ratio of the area of exit orifice hole and that of aerorator. The droplet size was measured by varying the area ratios. In addition, it was also confirmed that there is no change of the liquid flow rate and air flow rate to change the aerorator at the same exit orifice. Further, It was confirmed that the droplet size was relatively uniform even though the area ratio was different. Finally, there is little change in the SMD that air flow rate increases in 0.3 or more ALR.

• Journal of ILASS-Korea
• /
• v.23 no.4
• /
• pp.205-211
• /
• 2018

Y-jet nozzle has various advantages over other twin-fluid nozzles and are used in industrial boilers. However, it costs large energy consumption because of assisted air and its design is complex. The Y-jet nozzle is consisted of a liquid and gas port and a mixing chamber. The diameter of the port and the length of the mixing chamber greatly affect spray and atomization characteristics, therefore, they are the most important factors in nozzle design. In this study, The experimental setup is consisted of a laboratory scale spray system. The characteristics of the Y-jet nozzle according to the design parameters were observed. As a result, it was found that the length of the mixing chamber did not have effect on the flow rate and the choking condition. The droplet size was measured using a Malvern type measuring device. In addition, measurements were conducted in the front and the right directions of the nozzles. Based on the results, the SMD View Ratio is defined. It is the asymmetrical design characteristics of the Y-jet nozzle.

• Journal of ILASS-Korea
• /
• v.24 no.3
• /
• pp.137-144
• /
• 2019

The Y-jet nozzle has benefits such as simple design and wide operating conditions. Because of these benefits, it is used in various combustion devices including industrial boilers. The most important variables in the design of the Y-jet nozzle are the mixing chamber length, the supply diameter of the liquid fuel and gas, and the exit orifice diameter. In addition, because of the use of a twin-fluid, optimized data is required depending on the spray condition. In this study, spray experiment was carried out under the pressure condition of 7 bar or more, which is the spraying condition used in industry. There was no change in flow rate with the length of the Y-jet nozzle mixing chamber, but the difference in SMD was confirmed. Adjusting the exit orifice diameter is most important to achieve the desired flow rate. Changes in the liquid and gas inlet port diameters ratio were found to be help improve the operating range and significant difference in SMD was observed.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.3
• /
• pp.50-58
• /
• 2011

To utilize wind resources effectively around buildings in urban area, the magnitudes of wind velocity and turbulence intensity are important, which means the need of the information about the relationship between the magnitude of wind velocity and that of fluctuating wind velocity. In the paper, wind-tunnel experiments were performed to provide the information about Characteristic of Wind flow around buildings with the spanwise distance and the side ratio of buildings as variables. For a single building with the side ratios of one and two, the average velocity ratio was 1.4 and the velocity standard deviation ratio ranged from 1.4 to 2.6 at the height of 0.02m at the corner of the windward side, in which flow separation occurred. For twin buildings with the side ratios of one and two, the velocity ratio ranged from 2 to 2.5 as the spanwise distance varied at the height of 0.02m, and the velocity standard deviation ratio varied near 1.25. For twin buildings with the side ratios of one and two, the maximum velocity ratio was 1.75 at the height of 0.6m, and the maximum velocity standard deviation ratio was 2.1. It was also found from the results of CFD analysis and wind-tunnel experiments that for twin buildings with the side ratios of one and two, the difference between the velocity ratio of CFD analysis and that of wind-tunnel experiments at streamwise distances was near 0.75.

• Journal of Ship and Ocean Technology
• /
• v.10 no.4
• /
• pp.12-23
• /
• 2006

In this paper, a numerical study is carried out to investigate the turbulent flow around a twin-skeg container ship model with rudders including propeller effects. A commercial CFD code, FLUENT is used with body forces distributed on the propeller disk to simulate the ship stem and wake flows with the propeller in operation. A multi-block, matching, structured grid system has been generated for the container ship hull with twin-skegs in consideration of rudders and body-force propeller disks. The RANS equations for incompressible fluid flows are solved numerically by using a finite volume method. For the turbulence closure, a Reynolds stress model is used in conjunction with a wall function. Computations are carried out for the bare hull as well as the hull with appendages of a twin-skeg container ship model. For the bare hull, the computational results are compared with experimental data and show generally a good agreement. For the hull with appendages, the changes of the stem flow by the rudders and the propellers have been analyzed based on the computed result since there is no experimental data available for comparison. It is found the flow incoming to the rudders has an angle of attack due to the influence of the skegs and thereby the hull surface pressure and the limiting streamlines are changed slightly by the rudders. The axial velocity of the propeller disk is found to be accelerated overall by about 35% due to the propeller operation with the rudders. The area and the magnitude of low pressure on the hull surface enlarge with the flow acceleration caused by the propeller. The propellers are found to have an effect on up to the position where the skeg begins. The propeller slipstream is disturbed strongly by the rudders and the flow is accelerated further and the transverse velocity vectors are weakened due to the flow rectifying effect of the rudder.