• 수산해양교육연구
• /
• 제28권3호
• /
• pp.645-652
• /
• 2016

At the initial stage of propulsion shaft design, in line with shaft alignment, an intensified consideration of lateral vibration is needed to verify its operational safety. Recently the alignment problem affecting the lateral vibration has been becoming issues. However, the theoretical method of forced lateral vibration analysis is not cleary established so far and it is about to simply limited among the classification societies and international standards to avoid the blade natural frequency resonance cpm outside of ${\pm}20%$ of engine rpm at MCR. On the other hand, longer center distance between each support bearing shows an affirmative result normally in shaft alignment analysis whereas the blade order resonance speed may cause lowering near the limitation in the aspect of lateral vibration. Therefore, it is required careful attention to engineers as described above. As a method to solve the problem, it is mainly considered that remove forward stern tube bearing. In this paper, based on a medium size container ship case, theoretical study was carried out in the context of the forward stern tube bearing. The various effects and functions of forward stern tube bearing are reviewed and evaluated. Then an guidance note to lead the conclusion is proposed.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권1호
• /
• pp.33-41
• /
• 2008

Bearing damages by shaft misalignment have frequently been happened in marine ships. Specially. after stern tube bearing damage and failure for large crude oil carriers have been reported several times. However. the bearing reaction of the after stern tube bearing cannot be measured by jack-up test due to the hull structure condition. Therefore, when the jack-up test is used for the bearing reaction measurements, the bearing reaction for the after stern tube bearing obtained from the theoretical calculation method have to be used. In this paper, the shaft alignment on the large oil crude carrier is theoretically calculated and the differences between the calculated and actual installed bearing reaction values are compared. The bearing reactions for forward stern tube bearing and intermediate bearing are calculated by the simple formula using the strain gauge bending moments obtained from the measurements. Their reliability is confirmed by comparing the bearing reactions from jack-up test and the bearing reaction for after stern tube bearing is calculated by the same test. Also, the bearing reactions on the after stern tube bearing, forward stern tube bearing and intermediate shaft bearing under all operating conditions are calculated by using the bending moments obtained from the measurements and it is confirmed that the differences of the bearing reaction for all operating conditions are caused from hull deflection. The results of this study should prove useful for the future projects of the alignment calculation including the hull deflection effectiveness.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2005년도 특별논문집
• /
• pp.134-137
• /
• 2005

Recently, in VLCC, shafting system is stiffer due to large engine power whereas hull structure is more flexible due to scantling optimization, which can be suffered from alignment damage by incompatibility between shafting and hull, In this study, shafting system without stern tube forward bush was adapted for less sensitive system against external factors. Also, shaft alignment analysis was considered with hull deflection at various ship loading conditions and stern tube after bush of long journal bearing was evaluated by static squeezing pressure and dynamic oil film pressure with sloping control. Whirling vibration was also reviewed to avoid resonance with propeller blade order. So, reliable shafting design for VLCC could be achieved through optimized alignment analysis for the system without stern tube forward bush.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권2호
• /
• pp.130-135
• /
• 2015

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational rpm range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering from operating rpm up to target rpm, however, the range is un-measurable generally. In order to resolve the measurement issue, this study shows the measuring method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2012년도 전기공동학술대회 논문집
• /
• pp.184-184
• /
• 2012

Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering the range of MCR, however, the range is un-measurable. To resolve the measurement issue, this study shows the measuring method and the estimating method of whiling vibration by using resonance frequency of sub harmonic.

• 한국산학기술학회논문지
• /
• 제18권12호
• /
• pp.135-139
• /
• 2017

VLCC 추진축계의 선미관 후부 베어링에서 주로 발생하는 발열 사고는 프로펠러 하중이 추진축을 처지게 하여 후방부에 과도한 국부압착압력이 작용하는 것이 주된 원인이다. 최근 VLCC는 엔진 출력이 크고 축 직경이 증가하는 반면 선미관전부 베어링과 후부 베어링 사이의 간격이 상대적으로 짧아져 축계 시스템의 유연성이 저하되는 경향이 있으며, 이로 인해 발열 사고 가능성에 대한 우려가 커지고 있다. 본 연구에서는 선체의 변형에 대한 축계의 유연성을 확보하기 위한 방안으로 선미관 전부 베어링을 삭제하고 선미관 후부 베어링만을 설치한 새로운 축계 시스템의 적용 가능성을 검토하였다. 국부압착압력의 계산에 있어서는 접촉 너비를 따라 반 타원 형상의 압력 분포를 가정한 Hertzian 접촉 조건을 도입하였으며, 엔진 가동 상태의 프로펠러 하중, 열 효과 및 선체 변형을 고려하였다. 제안된 축계 시스템에 대한 해석을 통해 선미관 후부 베어링의 축 접촉면 재료인 화이트 메탈에 부분 경사를 추가 시공함으로써 설계 요구 조건이 만족됨을 확인하였다. 제안된 축계 시스템의 적용을 통해 발열 사고 예방을 위한 축계 유연성 확보 뿐 만 아니라 시스템의 단순화를 통한 설치비용의 감소 등 부가적인 효과도 기대할 수 있다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권3호
• /
• pp.185-190
• /
• 2016

선박이 고출력화, 초대형화 됨에 따라 대형저속 2행정 엔진을 탑재한 선박에서 축계배치의 잘못에 기인하는 주기관 선미측 베어링과, 선미관 후부 베어링의 손상이 증가하는 경향이 있다. 또한 고출력화에 의한 추진축의 강성은 증가한 반면에 선체는 고장력 후판을 사용하므로 이전의 선체보다 훨씬 더 쉽게 변형하는 실정이다. 이는 기존의 선박보다 더욱 정교한 축계배치가 요구됨을 의미한다. 본 연구에서는 열팽창 효과, 감도지수를 이용한 중간축 베어링의 최적위치 선정 및 베어링의 강성을 고려하여, 베어링의 하중 분석 및 영향 계수를 분석함으로서 축계 배치가 이론적으로 최적이 되는 것을 검토하였다. 이를 위하여 축계 배치 계산시 대형 엔진 제조사의 엔진 거치기준을 참조하고, 한국선급 및 DnV 선급의 축계 배치 프로그램을 이용하여 검토하고 그 신뢰성을 검증하였다.