• Title/Summary/Keyword: Cavitation

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Effect of Solution Temperature on the Cavitation Corrosion Properties of Carbon Steel and its Electrochemical Effect

  • Jeon, J.M.;Yoo, Y.R.;Kim, Y.S.
    • Corrosion Science and Technology
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    • v.20 no.6
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    • pp.325-334
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    • 2021
  • In the open system (vessel and pipe), the maximum corrosion rate of carbon steel at ca. 80 ℃ was obtained due to the decrease of dissolved oxygen by increasing the solution temperature. Effect of temperature on the cavitation damage can be explained through several mechanisms. Moreover, when cavitation occurs on the surface of metal and alloys, whether cavitation is erosion or corrosion is still controversial. This work focused on the effect of solution temperature on the corrosion of carbon steel under cavitation in an open system, Tests were performed using an electrochemical cavitation corrosion tester in 3.5% NaCl solution and the effect of solution temperature of carbon steel was discussed. Cavitation corrosion rate can be increased by cavitation, but when the temperature increases, a dissolved oxygen content reduces at a very high speed and thus the maximum cavitation corrosion temperature changed from 80 ℃ to 45 ℃. Below the maximum cavitation temperature, the electrochemical effect was more dominant than the mechanical effect by increasing temperature, but over the maximum cavitation temperature, the mechanical effect was more dominant than the electrochemical effect by increasing temperature.

A New Approach in Numerical Assessment of the Cavitation Behaviour of Centrifugal Pumps

  • Stuparu, Adrian;Susan-Resiga, Romeo;Anton, Liviu Eugen;Muntean, Sebastian
    • International Journal of Fluid Machinery and Systems
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    • v.4 no.1
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    • pp.104-113
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    • 2011
  • The paper presents a new method for the analysis of the cavitation behaviour of hydraulic turbomachines. This new method allows determining the coefficient of the cavitation inception and the cavitation sensitivity of the turbomachines. We apply this method to study the cavitation behaviour of a large storage pump. By plotting in semi-logarithmic coordinates the vapour volume versus the cavitation coefficient, we show that all numerical data collapse in an exponential manner. By analysis of the slope of the curve describing the evolution of the vapour volume against the cavitation coefficient we determine the cavitation sensitivity of the pump for each operating point.

Measurement of Cavitation-Induced Pressure Fluctuation in a Large Cavitation Tunnel (대형 공동 수조에서의 변동 압력 계측)

  • Na, Yun-Cheol;Kang, Kwan-Hyoung;Kim, Young-Gi;Lee, Mu-Yeol
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.791-796
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    • 2000
  • The cavitation-induced fluctuating pressure of the container ship named "Sydney Express" is measured in Samsung Large Cavitation Tunnel(SCAT). In the measurements, a complete ship model is employed. The effects of thrust coefficient and cavitation number on cavity pattern and cavitation-induced fluctuating pressure were investigated experimentally. It is demonstrated that the fluctuating pressure coefficient is very sensitive to the cavitation number. The results of cavitation and pressure fluctuations are compared with those of ITTC and HSVA, which shows fairly good agreement. It is exhibited that the removal of rudder can significantly change the loading condition of a propeller, and can reduce the fluctuating pressure coefficient almost by half.

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Electrochemical Approach on the Corrosion During the Cavitation of Additive Manufactured Commercially Pure Titanium (적층가공 방식으로 제조된 CP-Ti의 캐비테이션 중 부식에 대한 전기화학적 접근)

  • Kim, K.T.;Chang, H.Y.;Kim, Y.S.
    • Corrosion Science and Technology
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    • v.17 no.6
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    • pp.310-316
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    • 2018
  • The effect of passive film on corrosion of metals and alloys in a static corrosive environment has been studied by many researchers and is well known, however few studies have been conducted on the electrochemical measurement of metals and alloys during cavitation corrosion conditions, and there are no test standards for electrochemical measurements 'During cavitation' conditions. This study used commercially additive manufactured(AM) pure titanium in tests of anodic polarization, corrosion potential measurements, AC impedance measurements, and repassivation. Tests were performed in 3.5% NaCl solution under three conditions, 'No cavitation', 'After cavitation', and 'During cavitation' condition. When cavitation corrosion occurred, the passive current density was greatly increased, the corrosion potential largely lowered, and the passive film revealed a small polarization resistance. The current fluctuation by the passivation and repassivation phenomena was measured first, and this behavior was repeatedly generated at a very high speed. The electrochemical corrosion mechanism that occurred during cavitation corrosion was based on result of the electrochemical properties 'No cavitation', 'After cavitation', and 'During cavitation' conditions.

Correlation study between propeller noise and cavitation erosion with inclined propeller model test (경사축 추진기 모형시험에서 추진기 소음과 캐비테이션 침식 상관관계 연구)

  • Seol, Hanshin;Paik, Bu-Geun
    • The Journal of the Acoustical Society of Korea
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    • v.38 no.3
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    • pp.328-333
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    • 2019
  • In this paper, to investigate the cavitation erosion phenomenon on the ship propeller, the correlation between the propeller noise and the cavitation intensity was analyzed. Cavitation erosion is closely related to cavitation collapsing intensity, which can be defined as the frequency and intensity of cavitation collapse. The pressure wave generated by cavitation collapse appears as a continuous acoustic pulse and this result is analyzed with the cavitation behavior to determine the relationship of the propeller noise to cavitation collapse intensity. This technique is applied to the propeller erosion test using the inclined shaft propeller model.

Effect of Tip Clearance on the Performance of a Turbopump Inducer (끝틈새가 터보펌프 인듀서의 성능에 미치는 영향)

  • Hong, Soon-Sam;Kim, Jin-Sun;Choi, Chang-Ho;Kim, Jinhan
    • 유체기계공업학회:학술대회논문집
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    • 2004.12a
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    • pp.558-563
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    • 2004
  • Experiments were performed to see the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests were done for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decreased. Attached cavitation and cavitation surge were found in the cavitation tests. In the attached cavitation one cell rotated at the same rotational speed as that of the inducer. Cavitation performance deteriorated with increase in the tip clearance. The level of casing vibration increased in the cavitation condition and the level was very high when the attached cavitation appeared.

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Effect of Tip Clearance on the Performance of a Turbopump Inducer (끝틈새가 터보펌프 인듀서의 성능에 미치는 영향)

  • Hong, Soon-Sam;Kim, Jin-Sun;Choi, Chang-Ho;Kim, Jin-Han
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.1 s.34
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    • pp.19-24
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    • 2006
  • Experiments are carried out to investigate the effect of radial tip clearance on a turbopump inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7. Hydraulic and cavitation tests are performed for three cases of tip clearance ratio, that is, 0.026, 0.053, and 0.079. With increase in the tip clearance, inducer head and pressure on the inducer tip decrease. Attached cavitation and cavitation surge are observed in the cavitation tests. In the attached cavitation one cell rotates at the same rotational speed as that of the inducer. Cavitation performance deteriorates with increase in the tip clearance. The level of casing vibration increases in the cavitation condition and the level is very high when the attached cavitation appears.

Experimental Study on the Performance of a Turbopump Inducer

  • Hong, Soon-Sam;Kim, Jin-Sun;Park, Chang-Ho;Kim, Jinhan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.240-244
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    • 2004
  • Characteristics of steady and unsteady cavitation in a turbopump inducer were investigated in this paper. To see the effect of tip clearance on the inducer performance, three cases of tip clearance were tested. The helical inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7, was tested in the water. In the non-cavitating condition, the inducer head decreased with increase in the tip clearance. Rotating cavitation and cavitation surge were observed through unsteady pressure measurements at the inducer inlet. The cell number and propagation speed of the rotating cavitation were determined through cross-correlation analysis. During the rotating cavitation one cell rotated at the same rotational speed as that of the inducer rotation and the cavitation surge did not rotate. The critical cavitation number increased with increase in the tip clearance at the same flow rate, but the change of critical cavitation number was small at the nominal flow rate.

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Analysis of bubble cavitation and control of cavitation noise of hydrofoils (기포 캐비테이션의 거동 해석 및 수중익 캐비테이션의 소음 제어)

  • 강관형;안종우;송인행;김기섭
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.335-341
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    • 2001
  • The bubble cavitation and cloud cavitation are the major sources of cavitation-induced sound and vibration. A numerical method which predicts the trajectory and volume change of a cavity is developed, to predict the cavitation noise of a body. It is shown, by using the numerical method, that the cavitation inception and events rate is strongly dependent on the screening effect caused by the pressure gradient around a body, which is confirmed experimentally. Additionally, the effectiveness of a cavitation control method utilizing air injection is investigated experimentally. It is demonstrated that the noise level of the cloud cavitation can be significantly reduced by the air-injection method.

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Experimental Study for the Prevention of Cavitation Damage in the Diesel Fuel Injection Pumps (디젤엔진 연료분사펌프 캐비테이션 손상 방지를 위한 실험적 연구)

  • Kim, Dong-Hun;Park, Tae-Hyung;Heo, Jeong-Yun;Ryu, Seung-Hyup;Kang, Sang-Lip
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2011.10a
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    • pp.61-61
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    • 2011
  • Cavitation phenomena during the injection process of the conventional fuel injection pump for a medium-speed diesel engine can cause surface damage with material removal or round-off on the plunger and barrel port and may shorten their expected life time. An experiment of flow visualization was carried out to investigate the main cause of these cavitation damages and find the prevention method. Experimental results of flow visualization show that these damages are mainly affected by fountain-like cavitation and jet-type cavitation generated before and after the end of fuel delivery process and therefore the prevention method was designed to control these cavitation flows. From the visualization and endurance test, it was proved that this method can effectively prevent cavitation damages by controlling cavitation flows.

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