• 대한조선학회논문집
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• 제60권1호
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• pp.1-9
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• 2023

In order to improve the propeller cavitation performance composed of Cavitation Inception Speed (CIS), cavitation extent and pressure fluctuation, it needs to improve the wake distribution that flows into the propeller. The warship propeller cavitation is strongly influenced by the wake created at the V-strut of various appendages. The inflow characteristics of the V-strut were investigated using Computational Fluid Dynamics (CFD) and the twisted angles of the V-strut were aligned with upstream flow. The resistance and self-propulsion tests for the model ship with the existing and modified V-struts were conducted in Towing Tank (TT), and wake distribution, CIS, cavitation observation and pressure fluctuation tests were conducted in Large Cavitation Tunnel (LCT). The propeller behind the modified V-strut showed better cavitation characteristics than that behind the existing V-strut. Another model test was conducted to investigate rudder cavitation performance by the change of the V-strut. The rudder cavitation characteristics were not improved by the change of the operating conditions. On the basis of the present study, it is thought that the stern appendages for better propeller cavitation performance would be developed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.340-345
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• 2003

Cryogenic turbopump test facility(CTTF) is designed and developed. Hydraulic and cavitation performance of turbopump in cryogenic environment can be measured. Working fluid is liquid nitrogen and operating temperature is $-197^{\circ}C$. Liquid nitrogen run tank, catch tank and pressurizing tank has been built and remote tank pressure control system are installed. Maximum power of turbopump is 320kW and its maximum speed is 32000rpm. Cryogenic fluids and lubricating systems are effectively separated that long test times are acquired. Therefore hydraulic and cavitation performance can be measured accurately and effectively. This facility will contribute greatly to the development of turbopump for KSLV.

• 대한조선학회논문집
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• 제48권1호
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• pp.15-22
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• 2011

In this paper, cavitation patterns of model tests were compared with those of full-scale measurement for a propeller of crude oil carrier which was suffered from erosions on suction side of blade tip region. Cavitation tests were performed at design and ballast draft using model and full scale nominal wakes. A model ship and wire mesh method was used for the simulation of wake patterns of model nominal wakes. For the prediction of full-scale wake patterns, a RANS solver(Fluent 6.3) was used and wire mesh method was used for the simulation of the full scale wakes. Comparison results show that cavitation patterns using predicted full-scale wake patterns are closer to cavitation patterns of full-scale measurement at ballast draft condition. Also, cloud cavitations were observed on the position of eroded area at both full-scale measurement and cavitation tests using simulated full-scale wake patterns.

• 대한조선학회논문집
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• 제58권2호
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• pp.105-111
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• 2021

The main source of underwater radiated noise of ships is cavitation generated by propeller blades. After the Cavitation Inception Speed (CIS), noise level at all frequencies increases severely. In determining the CIS, it is based on the results observed with the naked eye during the model test, however accuracy and consistency of CIS values are becoming practical issues. This study was carried out with the aim of developing a technology that can automatically recognize cavitation images using deep learning technique based on a Convolutional Neural Network (CNN). Model tests on a three-dimensional hydrofoil were conducted at a cavitation tunnel, and tip vortex cavitation was strictly observed using a high-speed camera to obtain analysis data. The results show that this technique can be used to quantitatively evaluate not only the CIS, but also the amount and rate of cavitation from recorded images.

• 항공우주기술
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• 제8권1호
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• pp.26-31
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• 2009

터보펌프 실매질 시험에 사용하기 위해 제작된 3기의 산화제펌프와 1기의 연료펌프에 대한 단품 수류시험을 실시하였다. 수류시험의 시험 영역(유량비, 캐비테이션 수)은 실매질 시험의 작동 영역을 충분히 포함하였으며, 각 펌프는 설계요구조건을 만족하였다. 시험 결과, 제작된 산화제펌프는 내부 형상에 따라 양정이 약 2% 차이가 났으며 효율 및 흡입성능은 거의 차이가 없었다. 연료펌프의 경우 형상이 같았던 이전 모델과 양정과 효율은 비슷하였으나, 흡입성능은 약간 떨어지는 것으로 나타났다.

• 한국음향학회지
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• 제19권8호
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• pp.47-53
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• 2000

수중에서 프로펠러에 의해 추진되는 추진체를 식별하기 위해 프로펠러의 추진력에 의하여 수중에 발생되는 cavitation의 비선형 음향학적 현상으로부터 발생되는 프로펠러의 shaft-rates와 blade-rates를 탐지하여 표적을 식별하기 위한 Maximum Likelihood Classifier를 유도하고, 시뮬레이션과 실험을 통한 검증을 수행하였고, 실제 해양에서 수집한 데이터에 대해 적용 가능함을 입증하였다.

• 한국표면공학회지
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• 제45권6호
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• pp.278-283
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• 2012

This investigation evaluated the effect of cavitation condition on electrochemical characteristics of 304 stainless steel, which is widely used for marine environment. The cavitation test with time were conducted on 304 stainless steel in seawater solution. Surface morphologies of specimen were observed by scanning electron microscope (SEM) and 3D microscope. Pitting depth, weight loss and damage rate were analyzed after each cavitation experiment. The surface damage was more severe as the current density increased. A dramatical increase in the damage depth and weight loss was observed after 7 hours of cavitation experiment.

• 한국유체기계학회 논문집
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• 제7권4호
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• pp.16-23
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• 2004

Hydraulic performance and cavitation characteristics of fuel pump in turbopump were studied experimentally. This fuel pump has a centrifugal impeller with a separate inducer. In this paper, static pressure distribution of inducer was examined in non-cavitation and cavitation conditions. As cavitation came, the rising curve of static pressure in front of inducer was lightened because blade lodging did. In result, this offered the mechanism that recirculation zone could be small in case that recirculation was generated in low flow rate.

• Corrosion Science and Technology
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• 제10권6호
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• pp.218-224
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• 2011

The fresh water and sea water in present ships is used as cooling water for marine engine. Therefore, corrosion damage in seawater system is frequently occurred. In particular, in the impeller of pump, the performance and material span due to the corrosion and cavitation erosion has adverse effects. Most of the pump impellers in vessels are used Cu-Al alloy. Cu-Al alloy which having the excellent mechanical properties and corrosion resistance is widely used in marine environments. However, despite the excellent characteristics, the periodic replacement parts due to the cavitation damage in seawater is vulnerable to economic viewpoint. In this study, Cu-Al alloy used with impeller for centrifugal pump were conducted various experiments to evaluate its characteristics in seawater and fresh water solutions. As an electrochemical result, the dynamic conditions that exposed to the cavitation environment presented high corrosion current density with collapse of the cavity compared with the static conditions. Cavitation test results, the weightloss and weightloss rate in fresh water are observed more than those of seawater.

• 한국지반공학회논문집
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• 제21권1호
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• pp.43-50
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• 2005

고압분사주입공법은 지반개량, 차수벽, 흙막이벽, 기초 보강말뚝 등에 사용되고 있다. 고압분사주입공법은 사질토지반에 대해서는 지수목적으로, 연약한 점성토 지반에서는 지반강화를 위하여 사용되고 있다. 그러나 현재 국내에 적용되고 있는 경우의 대부분은 지반조건에 따른 강도증가 효과를 경험적으로 파악하여 설계에 적용하고 있는 실정이고 이에 대한 많은 연구가 진행되고 있다. 본 연구에서는 고압분사주입공법의 지반교란에의 효율성을 증대시킬 목적으로 공동현상(cavitation) 이론을 응용하고자 하였다. 그리고 이를 정량적으로 분석하기 위하여 공동현상(cavitation)을 적용한 경우와 적용하지 않은 경우에 대해 지반조건, 주입압력 및 주입시간 등을 변화시켜가며 점성토 및 사질토 모형지반에 대하여 그라우팅을 실시하였다. 시험결과 공동현상(cavitation)을 적용한 경우 점성토 및 사질토 지반 모두 좋은 결과를 보여, 실제 공법에 적용가능성이 높은 것으로 나타났다.