• 한국유체기계학회 논문집
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• 제11권5호
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• pp.50-56
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• 2008

Metal cutting operations involve generation of heat due to friction between the tool and the pieces. This heat needs to be carried away otherwise it creates white spots. To reduce this abnormal heat cutting fluid is used. Cutting fluid also has an important role in the lubrication of the cutting edges of machine tools and the pieces they are shaping, and in sluicing away the resulting swarf. As a cutting fluid, water is a great conductor of heat but is not stable at high temperatures, so to improve stability an emulsion type mixed fluid with water and oil is often used. It is pumped over the cutting site of cutting machines as a state of atomized water droplet coated with oil by using jet. In this paper, to develop cutting fluid supplying nozzle to obtain ultra thin oil film for coating water droplet, a numerical analysis of three dimensional mixed fluid Jet through multi-stage nozzle was carried out by using a finite volume method. Jet flow characteristics such as nozzle exit velocity, development of mixing region, re-entrance and jet intensity were analyzed. Detailed mixing process of fluids such as air, water and oil in the nozzle were also investigated. It is easy to understand complex flow pattern in multi-stage nozzle. Important flow Information for advance design of cutting fluid supplying nozzle was drawn.

• 한국자동차공학회논문집
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• 제7권9호
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• pp.63-74
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• 1999

When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus , this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine dropkets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10m/s ∼30m/s. And fuel pressur ewas fixed to 300kPa, but air assist pressure was varied to 0∼25kPa for a vairable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.

• 한국분무공학회지
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• 제1권4호
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• pp.46-53
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• 1996

The present study is aiming at improving the performance of main nozzle of an air jet loom with a modified reed and auxiliary nozzles. The double coaxial pipe jets consisting of a central air jet and an annular air jet have been experimentally investigated. The duter jet has a potential core and a constant velocity. The inner jet through an inner long pipe is induced by the subatmospheric pressure near the inner nozzle edge, and the jet velocity of an inner pipe is always lower than that of a outer pipe. The static pressures of the main nozzle over a wide range of the nozzle tank pressure were measured, and the nozzle velocity and Mach numbers were analytically calculated. Experiment81 results indicate that the critical condition of Mach number of unity to occur at the two positions in a main nozzle; one of them is the needle tip and the other is the acceleration tube exit An increase in the tank pressure causes the critical throat condition to occur at the two positions above. The velocity of acceleration-tube exit is maximum at the critical length L* and flow patter in acceleration-tube over critical lengh remains unstable.

• 한국자동차공학회논문집
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• 제3권5호
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• pp.47-55
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• 1995

Cylindrical chokes are used widely as components of hydraulic equipments. The dynamic charac teristics between flowrate and pressure drop through the cylindrical chokes were discussed by the frequency characteristics of the chokes. It was assumed no pressure recovery occured at the downstream neighborhood of the choke. The pulsating jetflow from outlet of cylindrical chokes shows very complex behaviours which are quite different from the steady jetflow but it is not clarified quantitatively. In order to utilize the chokes as a flowmeter, it is indispensable to discuss the estimation of the dynamics of pressure drop in the downstream jetflow region of cylindrical chokes. In this experimental study, the dynamic behaviours of the jetflow in the downstream region of cylindrical chokes are investigated precisely by using flow visualization. In the results of experimental sutdy, it is clarified that the retachment length depended on pressure wave is compared with it depended on velocity wave.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 추계 학술발표회 논문집
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• pp.61-66
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• 2000

분류층 건식 석탄가스화 방식을 택하고 있는 아주대학교 내 BSU 가스화기는 반응 후 회분을 용융상태의 슬랙으로 처리하여 가스화기 하단으로 배출하고, 생성된 석탄가스는 가스화기 상부로 배출시켜 생성된 석탄가스로의 슬랙 유입을 최소화한 디자인이다. 이러한 분류층 가스화기는 고정층이나 유동층 방식의 가스화기에 비해 가스화기 출구에서의 온도가 130$0^{\circ}C$이상의 고온이 유지되므로, 미분탄을 사용하는 분류층 가스화방식에서는 미립 입자 일부가 비말동반되어서 미분탄내의 회재를 100% 용융 슬랙으로 처리하기는 불가능하고, 수 % 정도는 생성 석탄가스와 함께 가스화기 밖으로 배출된다.(중략)

• Journal of Advanced Marine Engineering and Technology
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• 제25권6호
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• pp.1308-1316
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• 2001

This paper described a numerical investigation performed to understand better the effects of flow parameters in an entrained flow combustor on the flow characteristics. The computational model was based on the gas phase Eulerian equations of mass, momentum and energy. The code was formulated with RNG $k-\varepsilon$ model for turbulent flow. The calculation parameters were the ratio of primary and secondary jet velocity and the height difference between primary and secondary jet As the secondary jet velocity increased, the upper recirculation 3one of the primary jet was strengthened. It was found that as the primary jet velocity increased, there was a critical jet Velocity at which the size of upper and lower recirculation zone was reversed.

• 동력기계공학회지
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• 제13권5호
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• pp.34-39
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• 2009

In this paper, the CFD analysis using various turbulent models has been performed to evaluate which type of turbulent models can predict well the mixing flow structure of $45^{\circ}$ impinging round jet. This CFD analysis has been carried out through the commercial Fluent software. As a result, any of turbulent models cannot predict the experimental results definitely all over the flow range. However, as compared with the experimental results, the turbulent model of realizable(RLZ) k-$\varepsilon$ only predicts well in the limited range between X/$X_0=1.1$ and X/$X_0=2.0$.

• 대한기계학회논문집B
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• 제41권1호
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• pp.29-36
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• 2017

본 논문은 환형노즐 이젝터를 이용하여 세정수 공급과 기포생성을 동시에 할 수 있는 세정기술 개발을 위한 기초연구를 목적으로 한다. 환형노즐 이젝터의 피치변화에 따른 구동 및 부유체의 정량적 유동특성과 세정수조에 분출되는 분류의 정성적 가시화 이미지를 분석하였으며, 세정물의 농약 잔류물 성분의 농도를 검증하였다. 피치가 증가하면 구동유량은 증가하는 반면에, 유량비는 감소하였다. 피치가 증가하면 분류는 부력분류나 평형분류 거동을 나타내며, 잔류농약의 농도는 감소 후 증가하였다.

• 대한기계학회논문집
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• 제13권2호
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• pp.287-298
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• 1989

본 수치적 해석에서는 H$_{w}$/H$_{g}$의 비가 5.0~16.7의 범위에서 수행된 실험결과를 바탕으로 기존의 ｋ-.epsilon. 난류모델을 사용하여, 고려하고자 하는 변수, 즉 유입유속, 입구 게이트의 높이, 수위, 배플의 유.무등에 따라서 액체의 유동형태가 어떻게 변하는가를 살펴 보고자 한다.다.

• 한국음향학회지
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• 제37권6호
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• pp.469-474
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• 2018

도시 유동인구가 증가함에 따라 도시 환경 소음에 관한 연구의 중요성이 증가하고 있다. 본 연구에서는 교통상황에서 발생하는 이상 소음을 최근 환경 소음 분류 연구에서 높은 성능을 보이는 딥러닝 알고리즘을 이용하여 분류한다. 구체적으로는 타이어 제동 마찰음, 자동차 충돌음, 자동차 경적음, 정상 소음 네 개의 클래스에 대하여 합성곱 신경망을 이용하여 분류한다. 또한, 실제 교통 상황에서의 환경잡음에 강인한 분류 성능을 갖기 위해 빗소리, 바람 소리, 군중 소리의 세 가지 환경잡음을 설정하였고 이를 활용하여 분류 모델을 설계하였으며 3 dB SNR(Signal to Noise Ratio) 조건에서 88 % 이상의 분류 성능을 가진다. 제시한 교통 소음에 대하여 기존 선행연구 대비 높은 분류 성능을 보이고, 빗소리, 바람 소리, 군중 소리의 세 가지 환경잡음에 강인한 교통 소음 분류 모델을 제안한다.