• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.185-193
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• 2003

Basic flow fields of two dimensional V flames were examined as a preliminary work to study the instability of premixed flame with vorticity generation. Laminar premixed propane and methane flame were anchored by electrically heated wire to make two dimensional V flames. Flow fields were measured mainly by PIV(Particle Image Velocimetray) and the results were compared with those obtained by LDV(Laser Doppler Velocimetry) to confirm their reliability. Because the curvatures of V flames are so small, V flames were locally assumed to be inclined planar flames in gravitational field. The measured flow fields were locally compared with those of analytical solutions, which showed the qualitatively similar results. In downstream region, the vorticity fields were nearly constant except region near the center line, which support the assumption of locally one dimensional flame. Besides it was tried to find experimentally the similarity of flow fields in downstream region. Finally, stability diagram of propane and methane flames were drawn for the equivalence ratio less than one and the wide range of mean velocity.

• Journal of Advanced Marine Engineering and Technology
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• 제24권1호
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• pp.25-30
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• 2000

In present paper, mass transfer over a flat plate with film condensation including noncondesable gas is analyzed with the help of similarity methods. Couette flow was assumed in liquid film and boundary-layer approximation was used in the ambient flow. Governing equations were transformed into the ordinary differential equtions by the similarity methods. Runge-Kutta and shooting method were used in order to fine the effect of mass transfer on the velocity and concentrations at the liquid-vapor interface.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.71-75
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• 1999

An approximate similarity theory has been applied to predict the forming load of non-axisymmetric forging of aluminum alloys through model material tests. The approximate similarity theory is applicable when strain rate sensitivity geometrical size and die velocity of model materials are different from those of real materials. Actually the forming load of yoke which is an automobile part made of aluminum alloys(Al-6061) is predicted by using this approximate similarity theory. Firstly upset forging tests are have been carried out to determine the flow curves of three model materials and aluminum alloy(Al-6061) and a suitable model material is selected for model material test of Al-6061 And then and forging tests of aluminum yokes have been performed to verify the forming load predicted from the model material which has been selected from above upset forging tests, The forming loads of aluminum yoke forging predicted by this approximate similarity theory are in good agreement with the experimental results of Al-6061 and the results of finite element analysis using DEFORM-3D.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.790-797
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• 2011

삼상유동층에서 수력학적 유사성을 규모인자(scaling factor)를 이용하여 해석하였다. 규모인자는 직경이 다른 두 종류의 삼상유동층간의 기체, 액체, 그리고 고체입자의 체류량과 단위면적당 유효부피흐름속도를 기준으로 정의하였다. 두 종류 삼상유동층의 직경은 각각 0.102 m와 0.152 m이었다. 여과된 압축공기, 물 그리고 밀도가 2,500 kg/$m^3$인 유리구슬을 각각 기체, 액체 그리고 유동고체입자로 사용하였다. 각 삼상유동층에서 각 상들의 체류량은 정압강하법에의해 결정하였다. 기체 및 액체의 유속 그리고 고체유동입자의 크기가 각 상들을 기준으로한 규모인자와 유효부피흐름속도를 기준으로한 규모인자에 미치는 영향을 검토하였다. 직경이 다른 두 삼상유동층에서 기체 체류량의 편차는 기체와 액체의 유속이 증가함에 따라 감소하였으나 유동입자의 크기가 증가함에 따라 증가하였다. 직경이 다른 두 종류 삼상유동층에서 액체 체류량 편차는 기체와 액체 그리고 고체유동입자의 크기가 증가함에 따라 감소하였다. 두 종류 삼상유동층에서 고체입자 체류량 편차는 기체유속과 유동입자의 크기가 증가함에 따라 증가하였으나 액체의 유속이 증가함에 따라 감소하였다. 직경이 다른 두 종류 삼상유동층에서 유효부피흐름속도를 매개로 한 규모인자는 기체유속과 유동입자의 크기가 증가함에 따라 감소하였으나 액체의 유속이 증가함에 따라 증가하였다. 본 연구에서 정의된 규모인자는 삼상유동층 공정의 수력학적 유사성을 해석하는데 효과적으로 사용될 수 있었다.

• 대한기계학회논문집
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• 제18권1호
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• pp.150-155
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• 1994

An Approximate solution for plane two-dimensional incompressible laminar jet issuing from a finite opening with arbitrary initial profile into the same ambient fluid is proposed. For an arbitrary initial velocity profile, the problem is generated from the well known similarity solution for the jet of infinitesimal opening and provides good approximations in the region where the similarity solution cannot be used as an approximation. The asymptotic behavior of this solution is investigated and it is shown that, as goes downstream, the present solution approachs the similarity solution.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.583-589
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• 2004

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fan has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control of the size and position, is the important cause of performance decrease. In this study, experiments are carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to research the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spital, which is the important factor haying an effect on it.

• 한국정밀공학회지
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• 제15권2호
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• pp.162-169
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• 1998

Lacking for the skilled grinding operator possessed of the experiential knowledges in machine shop, there is the just requirement which includes the establishment of the optimal grinding conditions. Accordingly, we attemt to develope the selection system of optimal grinding conditions such as workpiece velocity, depth of cut and wheel velocity and to add the trouble shooting system by means of the neural network. Those systems are robust to the each machine error and environmental unstable state. In addition. we produce the loaming process that is progressed with additional data modified by skilled operators, and excluding is advanced to similarity of input data.

• 한국정밀공학회지
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• 제17권1호
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• pp.204-208
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• 2000

An approximate similarity theory has been applied to predict the forming load of non-axisymmetric forging of aluminum alloys through model material tests. The approximate similarity theory is applicable when strain rate sensitivity, geometrical size, and die velocity of model materials are different from those of real materials. Actually, the forming load of yoke, which is an automobile part made of aluminum alloys(Al-6061), is predicted by using this approximate similarity theory. Firstly, upset forging tests are have been carried out to determine the flow curves of three model materials and aluminum alloy(Al-6061), and a suitable model material is selected for model material test of Al-6061. And then hot forging tests of aluminum yokes have been performed to verify the forming load predicted from the model material, which has been selected from above upset forging tests. The forming loads of aluminum yoke forging predicted by this approximate similarity theory are in good agreement with the experimental results of Al-6061 and the results of finite element analysis using DEFORM-3D.

• 한국연소학회지
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• 제5권1호
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• pp.19-30
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• 2000

The characteristics of NOx emissions in pure hydrogen nonpremixed flames with coaxial air are analyzed numerically for the three model cases of coaxial air flames classified by varying coaxial air velocity and/or fuel velocity. In coaxial air flames, the flame length is reduced by coaxial air and can be represented as a function of the ratio of coaxial air to fuel velocity. Coaxial air decreases flame reaction zone, resulting in reducing flame residence time significantly. Finally, the large reduction of EINOx is achieved by the decrease of the flame residence time. It is found that because coaxial air can break down the flame self-similarity law, appropriate scaling parameters, which are different from those in the simple jet flames, are recommended. In coaxial air flames, the flame residence time based on the flame volume produces better results than that based on a cube of the flame length. And some portion of deviations from the 1/2 scaling law by coaxial air may be due to the violation of the linear relationship between the flame volume and the flame reaction zone.

• Journal of Advanced Marine Engineering and Technology
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• 제34권5호
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• pp.725-734
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• 2010

본 연구에서는 2종류의 피라미드형 패조류용 인공어초의 안정성 평가를 위해 Froude 상사법칙을 적용한 고정상 및 이동상 수리모형실험을 수행하였으며, 현장 설계외력(파랑, 흐름 등) 조건에 따라 이론적/실험적 검토를 하였다. 실험 결과는 파랑-흐름 공존장에서 어초의 안정성에 영향을 미치는 무차원 영향인자(설계파라메타)인 쇄파상사지수, 수립자속도, 파압 등을 사용하여 상호관련성을 검토하였다. 그 실험결과, 어초의 활동을 일으키는 한계조건은 고정상 실험에서는 쇄파상사지수에 따라서 무차원 최대수립자속도가 약 0.4 이상일 때, 이동상 실험에서는 무차원 파압에 따라서 상대수심이 약 0.11 이하일 때 나타났다. 또한 상대수심에 따른 수평 및 연직 파압은 상대수심이 증감함에 따라서 선형적으로 감소하는 경향을 나타내었다.