• Title, Summary, Keyword: 노즐압력

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Numerical Investigation of Flow Structures near Various Nozzle Exit Geometries of the Air Bearing (공기베어링의 노즐 형상 변화에 따른 출구면 근방의 유동구조에 대한 수치해석)

  • Park, Byung Ho;Han, Yong Oun;Park, Sang-Shin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.3
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    • pp.235-242
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    • 2014
  • To investigate pressure distributions on the shaft surface of the air bearing, the commercial CFD software was employed to study three different nozzle geometries to improve the nozzle performance: general drill-shaped, matched cube-shaped and trimmed exit nozzles. Under the influence of stagnation point, the maximum pressure was observed at the center of shaft surface for all cases. Owing to the blocking effect of a fine gap between the shaft surface and the nozzle exit, the drill-shaped nozzle has the rapid local pressure increase near the nozzle exit corner, generating the ring vortex in the radial direction within pressure ratio of 6.92, and its pressure becomes negative in a certain range of downstream. In comparison, the contoured nozzle showed a local pressure increase in the measured range of pressure ratios, but a negative pressure appeared within the pressure ratio of about 10. The trimmed nozzle was seemed to extend the high pressure zone near the stagnation point in the radial direction substantially, and no negative pressure was appeared in the whole range. Based on these observations, it is found that trimming nozzle exit becomes more effective for improving the performance than modifying the nozzle inside contour.

Study of the Shock Structure of Supersonic, Dual, Coaxial, Jets (초음속 이중 동축 제트유동에서 발생하는 충격파 구조에 관한 연구)

  • 이권희;이준희;김희동;박종호
    • Journal of the Korean Society of Propulsion Engineers
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    • v.5 no.4
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    • pp.94-101
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    • 2001
  • The shock structure of dual coaxial jet is experimentally investigated. Eight different kinds of coaxial, dual nozzles are employed to observe the major features of the near field shock structure on the supersonic, coaxial, dual jets. Four convergent-divergent supersonic nozzles having the Mach number 2.0 and 3.0 are used to compare the coaxial jet flows discharging from two sonic nozzles. The primary pressure ratio is changed in the range between 1.0 and 10.0, and the assistant jet ratio from 1.0 to 4.0. The results show that the impinging angle, nozzle geometry and pressure ratio significantly affect the near field shock structure, Mach disk location and Mach disk diameter.

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Numerical Study on Heat Transfer Characteristic in Combustor Nozzle (추진기관 노즐의 열전달 특성에 관한 수치적 연구)

  • Namkoung, Hyuck-Joon;Han, Poong-Gyoo;Lee, Kyoung-Hoon;Kim, Young-Soo;Jeong, Hae-Seung
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.275-281
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    • 2007
  • For a cooling performance research of the combustor operated in a extreme environment of a high temperature and high pressure, we accomplished a cooling performance analysis. Generally a heat transfer characteristic in cooling passage is known well experimentally and theoretically, however heat flux in the combustion chamber isn't. In this study, fluid flow combined with heat transfer analysis is accomplished about a combustor nozzle. We tried to analyze the cooling performance with a heat transfer characteristic of a gas and coolant side in the view point of quantity on the mass flow rate to be supplied to the cooling channel. And finally, evaluation on the thermal safety of nozzle wall material was accomplished.

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Preliminary Experimental Results of Pressure Control for Modulatable Thruster Applications (노즐목 가변 추력기의 압력제어 기법에 관한 예비실험 결과)

  • Choi, Jae-Sung;Huh, Hwan-Il
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.18-21
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    • 2011
  • In this study, basic research on the pressure control using driven pintle of modulatable thruster is presented. For this purpose, pintle thruster and pintle shape was developed. The actuator model was selected by calculating pintle load using Fluent software. Preliminary unsteady experimental results show that huge pressure oscillation is occurred as the pintle approach toward nozzle wall. From the preliminary experimental results, we could see possibility of pressure control of the modulatable thruster.

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Heavy Oil Combustion Characteristics of the Hot Water Boiler System fueled by Rice Husk and Heavy Oil (왕겨와 중유연료를 겸용으로 이용하는 온수보일러 시스템에서 중유 연소특성)

  • 박승제;김동선
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • pp.217-222
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    • 2002
  • 본 연구에서는 가연성 폐기물을 이용한 시설원예 난방에너지 공급시스템 개발을 위하여 대형 온실 난방이나 RPC 시설에 이용할 수 있는 왕겨와 중유 겸용연소 시스템에서 중유의 연소 및 성능 특성을 분석하고자 하였다. 중요 인자로는 분사노즐의 크기(2.0, 2.25, 2.5, 3.0 GPH)와 진공압력(375, 500, 625, 750 Pa)을 설정하였으며 이에 대한 결과를 요약하면 다음과 같다. 1.진공압력 500Pa조건에서 연료 공급율이 증가할수록 연소실 벽체 열교환기 효율은 감소하고 폐열회수 열교환기와 사이클론 열교환기의 효율이 증가하였으며, 노즐 2.5GPH에서 진공압력이 커질수록 연소실 하부의 온도가 감소하였고 연소실 상부에서는 비슷한 경향을 보였다. 2, 연소온도특성, 열효율, 배기가스 성분분석 등의 결과로 볼 때 최적의 연소 조건은 노즐 2.5GPH는 진공압력 375Pa, 노즐3.0GPH는 진공압력 500Pa과 625Pa 사이로 판단되었다. 3. 배연가스내의 대기오염 성분은 모든 실험처리에서 CO 함량은 거의 없고 SO$_2$와 NO$_{x}$의 함량 또한 일반 보일러 허용기준을 만족하는 것으로 나타났다.

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Study on Reflected Pressure in a Shock Tunnel According to the Size of a Nozzle Throat (충격관 터널의 노즐목 크기에 따른 반사압력특성 분석)

  • Lee, Jong Kook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.6
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    • pp.479-487
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    • 2015
  • In a reflected shock tunnel, stagnation conditions of a nozzle are determined by the flow behind a reflected shock. When calculating the flow behind the reflected shock, unlike a shock tube, the flow leakage through the nozzle is to be considered. The analytical studies were done to find out the characteristics of the stagnation conditions of the nozzle with various nozzle throat size. Experiments and numerical simulations were also carried out for further understanding of the flow leakage effects. It was found that the nozzle stagnation pressure was diminished by the increase of the size of the nozzle throat. It was also found that the steady pressure in the stagnation were maintained well at the area ratio of the driven tube to the nozzle throat is 4.5.

EDISON_CFD를 활용한 핀틀 형상에 따른 압력특성 및 재순환 영역 연구

  • Mun, Tae-Seok
    • Proceeding of EDISON Challenge
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    • pp.68-70
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    • 2016
  • 최근 저비용 및 재사용 발사체 개발 연구에 관한 관심이 증가하고 있는 추세인데, 이로 인해 노즐 내부에 핀틀 개념을 적용하여 발사체의 성능을 높이거나 스로틀링을 활용한 재사용 연구가 중요해지고 있다. 이 노즐 내부에 탑재된 핀틀 형상은 노즐 성능을 결정짓는데 핵심적인 역할을 하게 된다. 따라서 본 논문에서는 핀틀 형상에 따른 압력특성과 재순환 영역의 경향성을 확인하여 추후 저비용, 재사용 발사체 개발 연구의 기초자료로 활용하고자 한다. 해석 결과 핀틀 크기보다 핀틀 각도가 성능 변화에 더 민감한 변수로 판단되었다.

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A study on the pintle-tip shapes effect of nozzle flow using cold-flow test (핀틀 형상이 노즐 유동에 미치는 영향에 대한 실험적 연구)

  • Kim, Joung-Keun;Park, Jong-Ho;Lee, Jong-Hoon;Jeon, Min-Kyung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.10
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    • pp.985-991
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    • 2010
  • The objective of this work was to investigate the pintle-tip shape effect on nozzle flow and thrust by cold flow test. When nozzle throat area was decreased by pintle movement, chamber pressure was increased monotonously but thrust was increased differently according to every pintle-tip shape. At the same chamber pressure and nozzle throat area, thrust of convex pintle-tip shape was mostly larger than that of concave one. Nozzle wall pressure distribution and magnitude of pintle-tip load depended on the pintle-tip shape, pintle position and nozzle throat area.

Numerical study of interior pressure development of closed nozzle (밀폐된 노즐 내부의 초기 압력발달에 대한 수치적 연구)

  • Park Geun-Hong;Kim Hyung-Jun;Kwon Se-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.423-426
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    • 2005
  • Numerical analysis of a gaseous jet injected into a closed nozzle was carried out considering the valve operation to simulate the interior pressure development of closed nozzle. Pressure data was obtained through valve operation and we compared numerical analysis with experiment data. Commercial code was used for the present calculation. Numerical results of a pressure development since its start showed good agreement for experiment data of the nozzle operation.

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Investigation of Effect of Shape of Pintle on Drag and Thrust Variation (핀틀 형상에 따른 추력 및 항력 변화 연구)

  • Park, Jong-Ho;Kang, Min-Ho;Kim, Joung-Keun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.3
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    • pp.237-243
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    • 2010
  • In this study, the effect of the shape of a pintle(obstacle) on thrust-modulation performance and drag in a pintle rocket was investigated by a cold flow test and by computational fluid dynamics. Pintle movement caused a monotonic increase in the chamber pressure. Thrust generated by the pressure distribution on the pintle body was linearly changed to the chamber pressure, and this thrust was greater than that generated by the nozzle-wall pressure distribution. Because the shock pattern in the nozzle changes with the shape of the pintle body and pressure ratio, the thrust generated by the nozzle-wall pressure is not directly affected by chamber pressure. The drag due to the pintle(obstacle) can be minimized for a fully linear pintle shape, regardless of chamber pressure.