• Title, Summary, Keyword: Orifice

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Analytical Study on the Compressure Flow Through a Double Orifice (이중 Orifice를 지나는 압축성 유동에 관한 해석적 연구)

  • 김희동;김태호;우선훈
    • Journal of the Korean Society of Propulsion Engineers
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    • v.1 no.2
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    • pp.41-47
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    • 1997
  • The flow choking in a double orifice is expected to depend on cross-sectional area ratios of the orifices, upstream Mach number and total pressure loss between the orifices. However, no research has been reported on the problems of the compressible flow through a double orifice so far. The present study investigated analytically the choke conditions of the compressible gas through a double orifice, using a simple compressible theory. The orifice area ratio, upstream Mach number, and total pressure loss were involved to find the effects that they have on the flow choking. The results of analytical method show that for orifice area ratios below 1.0, flow choking moves from the first to the second orifice as the total pressure loss increases, however, for orifice area ratios over 1.0, it occurs only at the second orifice.

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Particle Laden Flows Around Orifice Plates for Pressure Control in Pulverized Coal Pipe Lines (분체 이송관내 압력 조절을 위한 오리피스 주위에서의 입자 유동 및 마모 해석)

  • Cho, Hyung-Hee;Lee, Jae-Keun;Park, Ho-Dong;Seo, Tae-Won
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.11
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    • pp.1499-1508
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    • 1998
  • A numerical study is performed to investigate pressure drops, particle trajectories and erosion around orifice plates in pulverized coal pipe lines. Particle impaction rates change significantly with orifice shapes and Stokes numbers. At Reynolds number of $5{\times}10^5$, the pulverized coal flows well with streamlines and do not collide at the orifice plates at small sizes (${\sim}20{\mu}m$). However, the large particles (over $70{\mu}m$) impact on the front face of the orifice and erode the orifice surface. The pressure loss coefficients around the erode orifice are largely different from the designed original orifice.

Natural Orifice Transluminal Endoscopic Surgery and Upper Gastrointestinal Tract

  • Kim, Chan Gyoo
    • Journal of Gastric Cancer
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    • v.13 no.4
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    • pp.199-206
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    • 2013
  • Since the first transgastric natural orifice transluminal endoscopic surgery was described, various applications and modified procedures have been investigated. Transgastric natural orifice transluminal endoscopic surgery for periotoneoscopy, cholecystectomy, and appendectomy all seem viable in humans, but additional studies are required to demonstrate their benefits and roles in clinical practice. The submucosal tunneling method enhances the safety of peritoneal access and gastric closure and minimizes the risk of intraperitoneal leakage of gastric air and juice. Submucosal tunneling involves submucosal tumor resection and peroral endoscopic myotomy. Peroral endoscopic myotomy is a safe and effective treatment option for achalasia, and the most promising natural orifice transluminal endoscopic surgery procedure. Endoscopic full-thickness resection is a rapidly developing natural orifice transluminal endoscopic surgery procedure for the upper gastrointestinal tract and can be performed with a hybrid natural orifice transluminal endoscopic surgery technique (combining a laparoscopic approach) to overcome some limitations of pure natural orifice transluminal endoscopic surgery. Studies to identify the most appropriate role of endoscopic full-thickness resection are anticipated. In this article, I review the procedures of natural orifice transluminal endoscopic surgery associated with the upper gastrointestinal tract.

Spray Characteristics of a Liquid-fueled Ramjet Engine under High Pressure Air Condition (고압 유동조건에서의 액체 램제트 엔진의 분무특성)

  • Youn, H.J.;Lee, C.W.
    • Journal of ILASS-Korea
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    • v.9 no.2
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    • pp.34-40
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    • 2004
  • In a liquid-fueled ramjet engine, the insufficient mixing and evaporation result in the low combustion efficiency and combustion instability. Improving its characteristics and devising a means of fuel droplets with air may compensate these disadvantages of liquid fuel ramjet engine. The jet penetrations of various fuel injectors were measured to investigate the spray characteristics of a liquid-fueled ramjet engine under high pressure air-stream conditions. The penetrations in high pressure conditions are smaller than the values calculated from Inamura's or Lee's equations, and the jet penetrations in the high pressure conditions have a similar tendency. In the dual orifice injectors, the jet penetrations of rare orifice is rapidly increased due to the reduction of the drag, which is created by the jet column of front orifice. The jet penetration of rare orifice is increased because of the drag reduction created by the jet column of the front orifice. Because of the drag reduction formed by the column of jet, the jet penetration in the rear orifice of dual orifice injector is much larger than the jet penetrations of single orifice injector. As the distances of the orifice are increased, the jet penetrations of the rear orifice decrease.

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An Experimental Study on Flow Characteristics for Dual-Structured Orifice (이중구조 오리피스 팽창장치의 유동특성에 관한 실험적 연구)

  • 곽경민;김하덕;이중형;배철호;김종엽
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.12
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    • pp.1039-1046
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    • 2002
  • To investigate the characteristics of orifice as an expansion devices, the experimental apparatus was made and experiments are being peformed using R22 and R290. The main idea of this control method of refrigerant flow rate with coupled orifices is to control the ON/OFF state of T and Ball type orifice corresponding to the subdivided region of thermal load. When system requires minimum thermal load, both T and Ball type orifices are closed, but refrigerant can flow through small hole of T type orifice. In regular thermal load, when ball type orifice is closed, T type orifice is opened and mass flow rate increase more than OFF state of T type orifice, due to large diameter. In maximum thermal load, both T and Ball type orifices are open and the much refrigerant can flow. The flow characteristics on T type orifice and parallel-combined orifice are obtained in the subdivided region of thermal load.

Study of the Critical Gas Flow through an Orifice (오리피스를 통하는 임계 기체 유동에 관한 연구)

  • Kim, Jae-Hyung;Kim, Heuy-Dong;Park, Kyung-Am
    • Proceedings of the KSME Conference
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    • pp.532-537
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    • 2003
  • Gas flow through orifice is encountered in many diverse fields of engineering applications. In order to investigate the critical gas flow through an orifice system, a computational analysis is performed using axisymmetric, compressible, Navier-Stokes equations which are numerically solved by a fully implicit finite volume method. In the present study, the discharge coefficients of two different types of orifices which are a straight-bore orifice and a sharp-edged orifice, are predicted to obtain the critical flow conditions. The present CFD data are compared with the previous experimental results. The present computational results show that the critical mass flow rate through orifice is well predicted and it is a strong function of Reynolds number. The discharge coefficient increases with the orifice diameter.

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Effect of Nozzle Orifice Shape and Nozzle Length-to-Diameter Ratio on Internal and External Flow Characteristics of Diesel and Biodiesel Fuel (노즐 오리피스 형상 및 형상비가 디젤과 바이오디젤 연료의 노즐 내부 및 외부 유동특성에 미치는 영향)

  • Park, Su-Han;Suh, Hyun-Kyu;Lee, Chang-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.3
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    • pp.264-272
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    • 2007
  • The aim of this study is to investigate the effects of nozzle orifice shapes and the nozzle length-to-diameter ratio(L/D) on the nozzle cavitation formation inside the orifice and the external flow pattern. The nozzle used in this work was tested the taper orifice nozzle and the rectangular orifice nozzle which was made from the transparent acrylic acid resin. For studying the effect of the nozzle L/D ratio, it was used to three L/D ratios of 3.33, 10, and 20. The cavitation flow of nozzle was visualized by using the ICCD camera and optical system. This work revealed that the flow rate and discharge coefficient($C_d$) of the taper orifice nozzle was larger than those of the rectangular orifice nozzle at the same injection pressure. The cavitation flow was observed in the nozzle orifice at the low injection pressure and the breakup of liquid jet was promoted as the L/D ratio is decreased. The cavitation of biodiesel fuel was formed at the lower injection pressure than that of diesel fuel because of higher viscosity and density.

An Experimental Study on Water-Hammer Effect for Spacecraft Propulsion System (인공위성 추진계통 관로내의 수격효과에 관한 실험적 연구)

  • Kwon, Ki-Chul;Lee, Eun-Sang;Park, Sang-Min;Kang, Shin-Jae;Rho, Byung-Joon
    • Proceedings of the KSME Conference
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    • pp.288-293
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    • 2001
  • This paper presents the water-hammer effect due to the rapid opening and closing of isolation valve and thruster valve in the spacecraft propulsion system. The single propellant feed system was modeled to investigate the maximum peak pressure due to the water-hammer effect. The test parameters are tank supply pressure, shape and throat length of orifice and line length. Kerosene was used as the inert simulant propellant liquid instead of hydrazine. As downstream line length after isolation valve increased from 1.5 to 2.5m, the maximum line-filling water-hammer peak pressure decreased, but the average time interval between peak pressures increased. The maximum line-filling water-hammer peak pressure with orifice was lower than without orifice, and the maximum line-filling water-hammer peak pressure with orifice at the back of isolation valve was lower than with orifice in front of isolation valve. Without orifice, the maximum water-hammer peak pressure due to the rapid opening and closing of the thruster valve was about 126% of tank supply pressure. With orifice, it decreased. As orifice throat length increased, it decreased. The maximum water-hammer peak pressure due to the rapid closing of the thruster valve with converging-diverging orifice was lower than normal orifice. It was found that the orifice as a means of pressure drop was very effective to reduce the water hammer peak pressure at the thruster valve. The results of this study can be used for the design of spacecraft liquid propulsion feed system.

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Experimental Study on Characteristics of Two-Phase Flow through a Bypass Orifice Expansion Device

  • Choi, Jong-Min;Kim, Yong-Chan
    • International Journal of Air-Conditioning and Refrigeration
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    • v.9 no.1
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    • pp.11-19
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    • 2001
  • To establish optimum cycle of the inverter-driven heat pump with a variation of frequency, the bypass orifice, which was a short tube haying a bypass hole in the middle, was designed and tested. Flow characteristics of the bypass orifice were measured as a function of orifice geometry and operating conditions. Flow trends with respect to frequency were compared with those of short tube orifices and capillary tubes. Generally, the bypass orifice showed the best flow trends among them. and it would enhance the seasonal energy efficiency ratio of an inverter heat pump system, Based on experimental data, a semi-empirical flow model was developed to predict mass flow rate through bypass orifices. The maximum difference between measured data and model`s prediction was within $\pm$5%.

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Numerical Study on Improvement of Mixing Equipment' Plan in a Water Treatment Plant (수리해석을 이용한 정수장내 혼화장치 설계 개선에 관한 연구)

  • Oh, S.Y.;Hyun, D.S.;Oh, J.J.;Lee, S.H.;Lee, N.Y.
    • Proceedings of the KSME Conference
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    • pp.777-782
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    • 2001
  • In this study, we used In-line orifice mixer for efficient chemicals mixing in water treatment. The method of using In-line orifice mixer has been already proved the improvement of water treatment efficiency. Numerical study was performed using FLUENT, a commercial code, to standard design and production of effective In-line orifice mixer. As variable for exactly standardizing, a proper ratio between an outer diameter of cone and a diameter of pipe, a distance between cone and orifice, a determination of orifice diameter for an optimal mixing, a distance between injection nozzle's position and cone, Numerical study has been performed for optimal standard and analyzed flow field on a basis of turbulent intensity in an orifice downstream.

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