• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.9-23
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• 1995

To analyze the spray and flame in D.I. diesel engine, the visualizing methods by schlieren photograph and diffused background illumination photograph with high speed camera are applied to optically accessible D.I.diesel engine. Wcaporating spray, spray droplets and brightness flame are taken with high speed camera by visuallizing method in accordance with various suction air temperature and injection time. The spray and flame image on the film was analyzed by image analyzer. The optically accessible D.I. diesel engine had the similar pressure characteristic to the real D.I. diesel engine. Experimental results showed that shadow areas of the evaporating spray were extended at higher suction air temperature, spray droplets had a max. Penetration length and their penetrating patterns were dependent on the surrounding gas temperature, and flame size after ignition was largely governed by the evaporated fuel quantity at ignition point and by the surrounding gas condition due to piston motion.

• Journal of the Korean Society of Visualization
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• v.11 no.1
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• pp.22-27
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• 2013

An investigation into the influence of ultrasonic standing wave on the structural behavior of propane/air premixed flame has been made to get a clue to the combustion reaction acceleration and combustion instability. Visualization technique utilizing the Schlieren photography was employed for the observation of structural variation of the flame reaction zone. Evolutionary characteristics of the flame front were caught by the high-speed Schlieren image, through which local flame velocity of the moving front were analyzed in detail.

• Journal of the Korean Society of Visualization
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• v.15 no.1
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• pp.53-63
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• 2017

Sonic and supersonic jets include many complicated flow physics associated with shock waves, shear layers, vortices as well as strong interactions among them, and have a variety of engineering applications. Much has been learned from the previous researches on the sonic and supersonic jets but quantitative assessment of these jets is still uneasy due to the high velocity of flow, compressibility effects, and sometimes flow unsteadiness. In the present study, the sonic jets issuing from a convergent nozzle were measured by PIV and Schlieren optical techniques. Particle Image Velocimetry (PIV) with Olive oil particles of $1{\mu}m$ was employed to obtain the velocity field of the jets, and the black-white and color Schlieren images were obtained using Xe ramp. A color filter of Blue-Green-Red has been designed for the color Schlieren and obtained from an Ink jet printer. In experiments, two types of sonic nozzles were used at different operating pressure ratios(NPR). The obtained images clearly showed the major features of the jets such as Mach disk, barrel shock waves, jet boundaries, etc.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.604-605
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• 2017

The present work aims at visualization of the supersonic air jet flows discharged from C-D nozzles. In the present experiments, Prticle Image Velocimetry (PIV) was employed to specify the jet flow field quantitatively, and a color Schlieren optical method was applied to observe the same jets qualitatively. The $0.5{\mu}s$ duration of spark light source was used for Schlieren and it can be controled as $0.5{\mu}s$, $1{\mu}s$, $2{\mu}s$ and focusing mode. The convergent-divergent nozzles were used to generate the jet flow with the design Mach number of 2.0, 2.2. Nozzle pressure ratios (NPRs) were varied from 5 to 8. A good comparison of the jet size and shock location from the Schlieren images with the PIV quantitative values is obtained. The obtained images clearly showed the major features of the under-expanded jet, over-expanded jet, sound wave, turbulent eddies and so on.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.87-95
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• 1995

A commercial DOHC four valve engine was modified to make a single-cylinder optical model engine with replaceable head. Three kinds of head were used to generate swirl, tumble, and combined swirl/tumble motion. Schlieren visualization technique was applied to characterize the in-cylinder flow qualitatively. Particle Image velocimetry has been developed and applied for the quantitative flow measurements. Axial and tangential flow motion inside the cylinder has been characterized. The swirl/tumble port shows beneficial results in terms of turbulence generation for the initial flame propagation and mean swirl motion for the overall flame propagation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.489-495
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• 2017

An experimental study on supersonic jets produced by supersonic nozzles at low operating pressure ratio is conducted. In the present experiments, particle image velocimetry (PIV) was employed to quantitatively specify the jet flowfield, and a color Schlieren optical method was applied to observe the same jets qualitatively. Convergent-divergent nozzles were used to generate the jet flow with design Mach numbers of 1.5 and 1.8. Nozzle pressure ratios (NPRs) were varied from 4 to 7. A good comparison of the jet size from the Schlieren images with the theoretical values is obtained. The obtained images clearly showed the major features of the under-expanded jet and over-expanded jet.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.6
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• pp.477-483
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• 2016

Velocity profiles of laminar, transition and turbulent boundary layers were investigated by using Particle Image Velocimetry(PIV) measurements on the flat plate at Mach 2.96. The Schlieren visualization and PIV measurements are also used to confirm whether the oblique shock wave generated from the leading edge affects the flow field over the flat plate. The laminar velocity profile measured from the experiment was well matched with the compressible Blasius solution. The velocity profile of the transition boundary layer was well correlated with the theoretical turbulent velocity profile from near the wall and the transition began from Re = $1.41{\times}106$. For the turbulent boundary layer, considering compressibility effects, the Van Driest-transformed velocity satisfies the incompressible log-law. It is found that the log region is extended farther in the wall-normal direction compared to the log region in incompressible boundary layer.

• Journal of Biomedical Engineering Research
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• v.2 no.2
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• pp.141-144
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• 1981

This paper descirbes about effects of refraction of ultrasonic beam on B-mode tomogram. Both compution based on Snell's law and the experiments performed using B-mode scanner and schlieren optical method are discussed on a circular phantom immersed in water. In these results, if the discrepancy of sound velocity is more than 0. 6%, the distortion of the B-mode image becomes conspicuous and a target beyound the phantom may disappear or displayed as two targets depending on the velocity of the phantom.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.219-227
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• 1998

This paper describes the fuel spray characteristics of gasoline port injectors such as the breakup procedures of liquid fuel, breakup and extinction behaviors of fuel spray at nozzle tip, time history of SMD and velocity distribution of fuel spray in the direction of fuel stream. Pintle-type gasoline fuel injector was used to analyze mentioned spray characteristics. In order to visualize the fuel spray behaviors and to measure the droplet mean diameter and velocities of spray droplets, the Schlieren method, digital image processing and auto-correlation PIV were applied in this study. In addition, the spray characteristics according to the variation of time were considered. The results of fuel spray show that the liquid sheet breakup starts at 10mm downstream actively. The flying time is approximately 4msec between 50mm and 80mm down the nozzle tip. Also, SMD of fuel spray, the number of droplets and fuel velocity distribution at each point of downstream are discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.18-25
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• 2000

A two-color particle image velocimetry (PIV) has been developed for measuring two dimensional velocity flowfields and applied to a Mach 2.0 supersonic nozzle. This technique is similar to a single-color PIV technique except that two different color laser beams are used to solve the directional ambiguity problem. A green-color laser sheet (532 nm: 2nd harmonic beam of YAG laser) and a red-color laser sheet (619 nm: output beam from YAG pumped Dye laser using Rhodamine 640) are employed to illuminate the seeded particles. A high resolution (3060${\times}$2036) digital color CCD camera is used to record the particle positions. This system eliminates the photographic-film processing time and subsequent digitization time as well as the complexities associated with conventional image shifting techniques for solving directional ambiguity problem. The two-color PIV also has the advantage that velocity distributions in high speed flowfields can be measured simply and accurately by varying the time interval between two different laser beams due to its high signal-to-noise ratio and thereby less requirement of panicle pair numbers for a velocity vector in one interrogation spot. The velocity distribution in the Mach 2.0 supersonic nozzle has been measured and the over-expanded shock cell structure can be predicted by the strain rate field. These results are compared and analyzed with the schlieren photograph for the velocity distributions and shock location.