• Title/Summary/Keyword: Cavitating venturi

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Papers : Application of Cavitating Venturi for Stable propellant feed system (논문 : 안정적인 액체연료 공급을 위한 Cavitating Venturi 의 응용)

  • Park,Hui-Ho;Kim,Yu;Jang,Eun-Yeong;Lee,Su-Yong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.1
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    • pp.88-94
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    • 2002
  • For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

Experimental Investigation on the Performance of a Cavitating Venturi According to Upstream and Back Pressure Variation (전단압과 배압 변화에 따른 캐비테이션 벤츄리 성능의 실험적 연구)

  • Ahn, Hyun Jong;Kang, Yun Hyeong;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.25 no.6
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    • pp.12-19
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    • 2021
  • An experimental study was performed for a cavitating venturi supplying a constant rate of flow independent of downstream pressure fluctuations when providing liquid propellant. The venturi was designed and manufactured in order to figure out the performance of the cavitating venturi. Effects of the rear-end shape, upstream pressure, and back pressure on the ratio of downstream to upstream pressure of the venturi as well as the flow-rate were observed. As a result, critical pressure ratio of the venturi, which generally depends only on the configuration of the venturi, was kept at 0.74 regardless of the rear-end shape and the upstream pressure of the venturi.

A Study on the Flow Control for Stable Combustion of Liquid Rocket (액체로켓의 연소안정을 위한 유량공급에 관한 실험적 연구)

  • Park, Hee-Ho;Kim, Yoo;Cho, Nam-Choon;Keum, Young-Tag
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.6
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    • pp.788-794
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    • 2002
  • In liquid rocket engine, propellant feed rate is proportional to approximately square root of the pressure difference between injector head and combustion chamber. This ΔP depends on the engine design, but in general on the order of 50psi. However, during ignition period, especially for the pressurized feed system, combustion chamber pressure is almost atmospheric and large ΔP causes over flow of propellants which may lead to catastrophic accident due to hard start. Hard start may be prevented by applying cavitating venturi or/and two step ignition. In cavitating venturi, evaporated propellants near the venturi throat become chocked and flow rate depends on only upstream condition. In two step ignition propellants are supplied to the liquid engine in two different flow rate. First step, to avoid hard start, small amount of propellants are supplied to build up chamber pressure in safe zone, then full propellants to ensure design pressure. In this study, both cavitating venturi and two step ignition method were used for the hot test and hard start problem was completely solved.

Flow Control Characteristics of Cavitating Venturi in a Liquid Rocket Engine Test Facility (액체로켓엔진 연소시험설비에서의 캐비테이션 벤튜리 유량공급 특성)

  • Kang, Donghyuk;Ahn, Kyubok;Lim, Byoungjik;Han, Sanghoon;Choi, Hwan-Seok;Seo, Seonghyeon;Kim, Hongjip
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.3
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    • pp.84-91
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    • 2014
  • The flow rate control of a cavitating venturi has been investigated with downstream pressure variation. A set of cavitating venturies for a liquid rocket engine thrust chamber firing test facility have been designed and manufactured. The flow characteristics of the cavitating venturies have been analyzed by experimental and computational methods. Results showed that constant mass flow rate condition was established by the cavitation inside the venturi. However, upstream pressure less than the actual design pressure of the cavitating venturi could not supply a constant flow rate.

Performance of Flow Rate Control of a Cavitating Venturi (캐비테이션 벤튜리의 유량제어 성능)

  • Cho Won Kook;Moon Yoon Wan;Kim Young-Mog
    • 한국전산유체공학회:학술대회논문집
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    • 2002.05a
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    • pp.146-151
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    • 2002
  • Characteristics of flow rate control has been studied for a cavitating venturi adopted in a liquid rocket propellant feed system. Numerical simulation has been peformed to give about $10\%$ discrepancy of mass flow rate to the experimental data for cavitating flow regime. Mass flow rate is confirmed to be saturated for pressure difference higher than $3\times10^5$pa when the upstream pressure is fixed to $22.8\times10^5$pa and the downstream pressure is varied. The evaporation amount depends substantially to non-condensable gas concentration. However the mass flow rate characteristic is relatively insensitive to the mass fraction of non-condensable gas. So it is reduced by only $2\%$ when the non- condensable gas concentration is increased from 1.5PPM to 150PPM. From the previous comparison the expansions of the non-condensable gas and the evaporation of liquid are verified to have same effect to pressure recovery.

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Flow Rate Control Characteristics of a Cavitating Venturi in a Liquid Rocket Propellant Feed System (액체로켓 추진제 공급계에서 캐비테이션 벤튜리의 유량 제어 특성)

  • Cho, Won-Kook;Moon, Yoon-Wan;Kwon, Oh-Sung;Cho, In-Hyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.6
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    • pp.46-52
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    • 2002
  • Characteristics of flow rate control has been studied for a cavitating venturi adopted in a liquid rocket propellant feed system. Both experiment and numerical simulation have been performed to give about 10% discrepancy of mass flow rate for cavitating flow regime. Mass flow rate is confirmed to be saturated for pressure difference higher than $3{\times}10^5$pa when the upstream pressure is fixed to $22.8{\times}10^5$pa and the downstream pressure is varied. The evaporation amount depends substantially to non-condensable gas concentration. However the mass flow rate characteristics is relatively insensitive to the mass fraction of non-condensable gas. So it reduces by only 2% when the non-condensable gas concentration is increased from 1.5PPM to 150PPM. From the previous comparison the expansion of the non-condensable gas and the evaporation of liquid are verified to gave same effect to the pressure recovery pattern.

NUMERICAL ANALYSIS OF CAVITATION FLOW AROUND OGIVE-CYLINDER AND VENTURI (Ogive-Cylinder 주위와 Venturi에서의 캐비테이션 전산 유동해석)

  • Lee, J.C.;Ahn, B.K.;Kim, D.H.;Kim, C.K.;Park, W.G.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.04a
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    • pp.130-133
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    • 2007
  • A two-phase method in CFD has been developed and is applied to model the cavitation flow. The governing equation system is two-phase Navier-Stokes equation, comprised of the mixture mass, momentum and liquid-phase mass equation. It employs an implicite, dual time, preconditioned algorithm using finite difference scheme in curvilineal coordinates and Chien ${\kappa}-{\varepsilon}$ turbulence equation. The experimental cavitating flows around ogive-cylinder and venturi type objects are employed to test the solver. To prove the capabilities of the solver, several three-dimentional examples are presented.

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A Study on the Flow Control for Stable Combustion of Liquid Rocket (액체로켓의 연소안정을 위한 유량공급에 관한 실험적 연구)

  • Jang, Eun-Young;Park, Hee-Ho;Kim, Sun-Ki;Kim, Yoo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.2
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    • pp.6-11
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    • 2000
  • In the pressurized propellant feed system of liquid rocket, feed pressure is decided chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosphere. So, it may have overflow, hard-start and even critical damage of engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. Hot test were already performed to verify the presented propellent feed system. The proposed propellant feed system uses two steps - pre and main combustion - to prevent large pressure increase and uses cavitating venturis for stable flow rate in whole combustion. This system feeds the flow rate lesser than the designed flow rate, so combustion pressure reached pre-combustion pressure. Cavitating venturis offer unique flow control capabilities at normal and abnormal combustion state, because flow rate is solely dependent on upstream absolute pressure and fluid properties, but independent on downstream condition.

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Analysis of flow rate control of cavitating venturi (케비테이션 벤튜리의 유량특성 해석)

  • Cho, Won Kook;Jung, Young Suk
    • 유체기계공업학회:학술대회논문집
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    • 2000.12a
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    • pp.318-324
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    • 2000
  • 액체로켓인 KSR-III는 점화시 및 연소실 압력의 이상 저하시 추진제가 지나치게 많이 공급되는 것을 막기 위하여 케비테이션 벤튜리를 사용한다. 본 연구에서는 Fluent가 제공하는 케비테이션 모형을 사용하여 케비테이션 벤튜리 내부의 공동 발생과 이에 따른 유량제어 현상을 해석하였다. 케비테이션 모형은 공동의 붕괴를 효과적으로 예측하지 못하는 단점이 있지만 벤튜리를 통과하는 유량은 공동이 발생하는 위치에서 유효 유로 감소에 의하여 제한되므로 유량제어 현상을 성공적으로 관찰할 수 있었다. 결과로서 벤튜리 상류의 압력이 일정하게 유지될 때 하류의 압력 변동에 대하여 유량이 변화하지 않음을 확인하였다. 상류의 압력이 24.1bar로 일정하게 유지되고 벤튜리에서 압력차이가 3bar 이하일 때 공동은 발생하지 않았다. 압력차가 6bar 이상일 때 공동이 발생하며 (압력차 6bar인 경우와 비교하여) 9bar, 12bar의 압력차에 대한 유량 증가는 각각 $5\%,\;7\%$에 그쳐 주어진 작동조건에서 벤튜리로 유량제어가 가능하였다.

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A Preconditioning Method for Two-Phase Flows with Cavitation

  • Shin B.R.;Yamamoto S.
    • 한국전산유체공학회:학술대회논문집
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    • 2003.10a
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    • pp.181-182
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    • 2003
  • A preconditioned numerical method for gas-liquid to-phase flow is applied to solve cavitating flow. The present method employs a density based finite-difference method of dual time-stepping integration procedure and Roe's flux difference splitting approximation with MUSCL-TVD scheme. A homogeneous equilibrium cavitation model is used. The method permits simple treatment of the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristics at low Mach number. By this method, two-dimensional internal flows through a venturi tuve and decelerating cascades are computed and discussed.

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