• Title/Summary/Keyword: Gap gas

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A Study on the Exhaust Gas Recirculation in a MILD Combustion Furnace by Using the Coanda Nozzle Effect (MILD 연소로에서 Coanda 노즐 효과를 이용한 배기가스 재순환에 관한 연구)

  • Ha, Ji Soo;Shim, Sung Hoon
    • Journal of Korean Society of Environmental Engineers
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    • v.35 no.12
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    • pp.967-972
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    • 2013
  • A MILD (Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of coanda nozzle geometrical parameters, nozzle passage gap length, nozzle passage length, nozzle angle and expansion length. The optimal configuration of coanda nozzle for the best entrainment flow rate was gap length, 0.5 mm, expansion angle, 4o and expansion length, 146 mm. The nozzle passage length was irrelevant to the exhaust gas entrainement.

Prebreakdown Phenomena of $SF_{6}$ Gas in a Non-uniform Field Disturbed by a Metallic Protrusion

  • Lee, Kyoung-Ok;Lee, Bok-Hee;Jeon, Duk-Kyu
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1996.05a
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    • pp.137-141
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    • 1996
  • This paper deals with the prebreakdown phenomena of $SF_{6}$ gap stressed by non-oscillating and oscillating impulse voltages in a strong inhomogeneous field disturbed by a fred needle shaped-protrusion on the earth-side electrode. The breakdown voltage-time characteristics were measured for both positive and negative polarities and over the gas pressure range of 0.1∼0.5 MPa, and the temporal developments of the 77breakdown were observed by a shunt of 50 n. The dependence of the leader stopping time on the gas pressure were obtained. The local field enhancement due to the space charges, which is produced by the streamer corona, has influence with the electrical breakdown of the test gap. The test streamer corona is oxy a necessary condition for the electrical breakdown and the subsequent ionization activities launch the leader at the local field region.

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Study for Gas Flow Uniformity Through Changing of Shape At the High Density Plasma CVD (HDP CVD) Chamber (HDP CVD 챔버 형상 변화에 따른 가스 유동 균일성에 대한 연구)

  • Jang, Kyung-Min;Kim, Jin-Tae;Hong, Soon-Il;Kim, Kwang-Sun
    • Journal of the Semiconductor & Display Technology
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    • v.9 no.4
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    • pp.39-43
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    • 2010
  • According to recent changes in industry for the semiconductor device, a gap between patterns in wafer is getting narrow. And this narrow gap makes a failure of uniform deposition between center and edge on the wafer. In this paper, for solving this problem, we analyze and manipulate the gas flow inside of the HDP CVD chamber by using CFD(Computational Fluid Dynamics). This simulation includes design manipulations in heights of the chamber and shape of center nozzle in the upper side of the chamber. The result of simulation shows 1.28 uniformity which is lower 3% than original uniformity.

Parameterizing the Perturbed Rotational Velocities of Planet-induced Gaps

  • Yun, Han Gyeol;Kim, Woong-Tae;Bae, Jaehan;Han, Cheongho
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.63.2-63.2
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    • 2019
  • Recent submillimeter observations of ALMA reveal that many protoplanetary disks contain substructures like gaps or rings. The disk-planet interaction is believed to be the most likely gap formation scenario, and most previous numerical work attempted to constrain the planet mass using the density profiles of gas in the gaps. Since the dust and gas distributions likely differ from each other in protoplanetary disks, however, perturbed rotational velocities that directly probe the gas would give a more reliable estimate to the planet mass. In this work, we run two-dimensional hydrodynamic simulations to measure the amplitudes and widths of rotational velocity perturbations induced by planets with different mass. We present the parametric relations of the gap widths and depths as functions of the planet mass and disk properties. We also apply our relations to HD 163296 to infer the masses of embedded planets.

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The Measurement of Minimum Ignition Energy and Explosion Limit for Pine Tree Dust (소나무 분진의 최소착화에너지와 폭발한계 측정에 관한 연구)

  • Choi Il-Gon;Cho Il-Keon;Mok Yun-Soo;Lee Dong-Hoon;Choi Jae-Wook;Ha Dong-Myeong
    • Journal of the Korean Institute of Gas
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    • v.2 no.2
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    • pp.55-60
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    • 1998
  • In this study, we investigated the dust explosion characteristics by determining minimum ignition energy and explosion limit for this experiment, we used pine-tree dust which was used widely for the filler of thermosetting resin. The experiment was accomplished according to the variation of discharge gap, dust concentration, particle size and humidity. The result of this experiment are as follows; (1) The relation between the discharge gap and ignition energy was that ignition energy decreased according as the discharge gap became small, but increased when the discharge gap was below 4mm and suddenly became infinite when the discharge gap was below. So, we knew that this infinite value was limit discharge gap. (2) When the dust concentration increase and the particle size became microscopic it was easy to explore and in the same particle size, if the humidity increase the minimum ingnition energy decreased.

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A Parametric Study on Secondary Electron Emission from MgO

  • Yoon, Sang-Hoon;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 2008.10a
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    • pp.953-956
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    • 2008
  • Using the theoretical model of Auger electron emission, effects of MgO properties which include band gap energy, escape probability, gas ion, and doping elements on the yield of secondary electron emission were examined. The results indicated that the band gap of MgO must be decreased and escape probability must be enhanced in order to increase the yield of secondary electrons from Xe ions and that may proved to be a critical for achieving high luminance efficacy in ac-PDPs.

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Band Gap Energy Engineering of Electron Emission Layer of ac-PDPs

  • Yoon, Sang-Hoon;Kim, Yong-Seog
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.262-264
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    • 2009
  • Ternary oxides with controlled band gap energy and reduced reactivity against moisture and carbon dioxide gas were designed and studied as a potential material for protective layer of ac-PDPs. The results showed a significant reduction in firing voltage and improved environmental stability.

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Effect of Piston Ring Gap on the Axial Motion of Piston Ring and Oil Consumption (피스톤 링갭이 링거동 및 오일소모에 미치는 영향)

  • 민병순;김중수;최재권
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.2
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    • pp.197-204
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    • 1997
  • In order to investigate the relationship between the ring gap ratio and oil consumption, the axial motion of piston ring was measured by capacitance technique. The pressures of each land and the motions of each ring were calculated by orifice-volume method in which it is assumed that the ring gaps are the only gas leakage paths. The calculated results were compared with the measured ones. Consequently, it is known that the increase of ring gap ratio has the effect of lifting the first ring. The calculated results were roughly in accordance with those measured. Therefore, it is possible to predict the effect of design variables on the pattern of ring motion. It is known that the lift off of first ring accompanied by the increase of ring gap ratio make rise of oil consumption.

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Welding Gap Detecting and Monitoring using Neural Networks

  • Kang, Sung-In;Kim, Gwan-Hyung;Lee, Sang-Bae;Tack, Han-Ho
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 1998.10a
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    • pp.539-544
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    • 1998
  • Generally, welding gap is a serious factor of a falling-off in weld quality among various kind of weld defect. Welding gap is created between two work piece in GMAW(Gas Metal Arc Welding) of horizontal fillet weld because surface of workpiece is not flat by cutting process. In these days, there were many attempts to detect welding gap. though we prevalently use the vision sensor or arc sensor in welding process, it is difficult to detect welding gap for improvement of welding quality. But we have a trouble to find relationship between welding gap and many welding parameters due to non-linearity of welding process. As mentioned about the various difficult problem, we can detect welding gap precisely using neural networks which are able to model non-linear function. Also, this paper was proposed real-time monitoring of weld bead shape to find effect of welding gap and to estimate weld quality. Monitoring of weld bead shape examined the correlation of welding parameters with bead eometry using learning ability of neural networks. Finally, the developed system, welding gap detecting system and bead shape monitoring system, is expected to the successful capability of automation of welding process by result of simulation.

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