한국해양대학교

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중형 석유화학제품 운반선의 추진축계 안정성 평가에 관한 연구

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dc.contributor.author 이재웅 -
dc.date.accessioned 2017-02-22T07:04:10Z -
dc.date.available 2017-02-22T07:04:10Z -
dc.date.issued 2016 -
dc.date.submitted 57098-06-03 -
dc.identifier.uri http://kmou.dcollection.net/jsp/common/DcLoOrgPer.jsp?sItemId=000002299683 ko_KR
dc.identifier.uri http://repository.kmou.ac.kr/handle/2014.oak/10222 -
dc.description.abstract As the ship has high output and large size with the development of shipbuilding and steel technologies, the shaft stiffness increases, but it is the situation that the hull is deformed much more easily than before due to using high-strength steel plate. Therefore, deep experience and high attention of the designer are required as the propeller shaft cannot endure the reaction force change coming from the deformation of the hull, if the calculation of shaft alignment is done without considering the deformation of the hull. It can be said that the other area that is very closely connected with shaft alignment is the lateral vibration of propulsion shaft system. So, it should be considered in the safety assessment of shafting. It is better that the distance between centers of supporting bearings of the shaft system is longer in terms of shaft system alignment, but in terms of lateral vibration, the natural frequency becomes lower, so there’s a chance that resonance occurs in the range of engine operating speed. The research related to lateral vibration still remains as a problem to be solved due to unclear elements such as supporting bearing’s stiffness in shaft system, oil film’s stiffness, propeller’s exciting force, etc. Until now, it only ensures whether there’s a sufficient margin to avoid the natural frequency of 1st order propeller blades to be within ±20% of the engine nominal speed in Classification Society, international standards, etc. Therefore, when considering such a situation, it is necessary to verify the calculation result of the natural frequency in the lateral vibration with the actual measurement. In the shaft system of a ship, the increase of local load in the stern tube bearing which supports a propeller shaft occurs prominently due to the influence of the propeller weight at the shaft end, similar to the case of the cantilever beam. Especially, the after stern tube bearing is likely to have a concentrated load in the bottom of aft side while the forward stern tube bearing does on the bottom of forward side. While such magnitude and distribution of local load are determined by the relative inclination angle between the shaft and bearing, the bottom of aft stern tube bearing is most affected among them. Such local load can deflect significantly toward the aft end of aft stern tube bearing in case that the shaft sags down, when the eccentric thrust force acts downward due to the propeller force in the hydrodynamic transient status. Case studies by some authors have presented the real-time dynamic behavior analysis of the shaft system in going-straight and turning by using the telemetry system. While the impact analysis of the shaft system in going-straight and turning of ship was carried out by domestic researchers recently, it was difficult to find the case which analyzed real-time dynamic behavior so far, so that it was considered meaningful to review the shaft behavior’s impact on the shaft system through this study. 50,000 DWT oil/chemical tanker is a type of ship emerging recently as a highly efficient eco-friendly ship and it lowered the engine speed by applying de-rating technology. It reduced fuel consumption significantly compared to similar ships and its feature is to maximize propulsion efficiency through applying the propeller of increased diameter. Therefore, some negative changes in terms of shaft alignment should be compared to similar ships, as the change in aft structure and increased weight of the propeller affect the deformation of the hull. Also, as the forward stern tube bearing is skipped, the natural frequency of lateral vibration becomes lower, so that the possibility of resonance in the operating speed range is expected to be slightly increased. After a review of previous researches, it is considered that there’s no comprehensive case study reported yet, which is related to the hull deformation, the lateral vibration and acceleration of the vessel and the shaft behavior in going-straight for 50,000 DWT oil/chemical tanker. Therefore, a theoretical review and analysis of measured data were performed in this study by using finite element analysis, strain gage method and reverse calculation method. And then the results are reported as follows after reviewing in detail the stability of the propeller shaft system of the target vessel. The finite element analysis result expects that the shaft is placed right down compared to the design value when it moves from light loading to full loading due to the hull deformation, and the reaction force of each bearing satisfying allowable values even under deformation. Also, the effect of hull deformation acts as a little positive factor increasing stability of the shaft system by relieving the relative angle of inclination of the aft stern tube bearing. While the hull deformation which is analyzed by using the strain gage method, is expected -2mm from the intermediate shaft bearing and about -4mm from the main engine bearing and it is a little bigger compared to the existing 47,000 DWT class, the increased weight of the propeller and main engine and the aft change due to the increase in propeller diameter are considered as main causes. The reaction force of the bearing supporting shaft system met allowable value like in the finite element analysis result, also in the full deformation and the cross validation result of bearing force obtained by the strain gage method, jack up method, and the shaft alignment program showed good correlations in most conditions so that the reliability of the analysis was able to be confirmed. The calculation result of lateral vibration’s natural frequency showed that resonant revolution speed was located in the area of more than 163.8% compared to MCR, so that it was above the limit value(±20%) and it was confirmed that there was no notable resonance point also in measurement analysis results. In case of 1st order component of lateral vibration, it showed the constant response of bending stress value regardless of rpm generally, it was considered because of run-out value. Furthermore, the measured bending stress was only 10% level of the provided measurement result, so that a negative influence by the lateral vibration was not expected to occur. The review result of the trajectory during the full laden draft operation showed that slight partial friction phenomenon was estimated with 25% of engine load in strain gage position #7. Therefore, it would be necessary to be careful on the long-time operation at 25% engine load to ensure the stability of shaft. strain gage position #5, it was considered acceptable phenomenon which could occur due to different anisotropy in vertical and horizontal stiffness in the intermediate shaft bearing. And while the hit and bounce friction phenomena was suspected at NCR condition (83 rpm) and it was expected to be stabilized after running-in operation. However, periodical monitoring was required to be continued through the shaft open-up survey when docking. Knowing the fact that the shaft direction in strain gage position #7 which was installed at the closest to propeller, moved toward left down direction with increasing engine load at both conditions regarding the shaft behavior. It was determined that the shaft direction in propeller location moved to the right upper direction which was the opposite to the moving direction of the strain gage installed location, and its effectiveness could be confirmed based on the previous study results obtained with direct measurements. Although the method above couldn’t determine the exact displacement component at the center of shaft, it could provide the moving direction’s pattern of propeller shaft by the engine load during operation, so that it was confirmed that it was significant and practical as an alternative method to the direct measurement one in the position of the propeller. Also, the propeller force during going-straight acted as a force lifting the shaft from the aft stern tube bearing and it reduced the possibility of damage to the aft stern tube bearing. Therefore, it was considered to contribute to improve the reliability of the shaft system. If the results obtained in this study are applied to similar type of ships for the shaft alignment and lateral vibration calculation, it is considered that it will help ensure the stability of the shaft system and prevent damages not only in quasi-static but also in dynamic conditions. -
dc.description.tableofcontents 목 차 제 1 장 서 론 1 1.1 연구의 배경 1 1.2 선행연구(Literature survey) 3 1.2.1 축계정렬 4 1.2.2 축계 횡진동 7 1.2.3 축의 거동 분석 8 1.3 연구의 목적 9 1.4 연구의 내용 및 구성 10 제 2 장 유한요소법에 의한 축계정렬 계산 이론 13 2.1 기본식의 유도 13 2.1.1 횡하중과 모멘트 하중을 받는 부등 단면보의 절점 방정식 13 2.1.2 횡하중과 모멘트 하중을 받는 보의 강성 매트릭스 16 2.2 횡하중과 모멘트 하중을 받는 부등 단면보 절점방정식의 해법 18 2.2.1 절점방정식의 해법 18 2.2.2 지점의 처리 18 2.3 반력 영향계수의 계산 20 제 3 장 축계 횡진동의 이론적 해석 방법 23 3.1 횡진동의 근사계산법 23 3.1.1 Panagopulos의 식 23 3.1.2 수정 Panagopulos의 식 26 3.1.3 Jasper의 식 27 3.1.4 Jasper-Rayleigh의 식 33 3.2 횡진동의 정밀 계산법 36 3.2.1 강성 매트릭스를 이용한 진동방정식의 유도 37 3.2.2 진동방정식의 해법 40 제 4 장 축계 베어링 반력 측정법 43 4.1 잭업법 43 4.1.1 주기관 최후부 베어링 측정 방법 47 4.1.2 주기관 베어링 측정 방법(최후부 베어링 외) 49 4.1.3 선미관 선수베어링과 중간축 베어링의 측정 방법 52 4.1.4 잭업법을 이용한 베어링 지지하중 계산 방법 53 4.1.5 잭업법을 이용한 축 불균형(run-out)량 계산 방법 55 4.2 스트레인 게이지법 55 4.2.1 축계 굽힘모멘트 산출 방법 60 4.2.2 스트레인 게이지법을 이용한 베어링 지지하중 계산 방법 64 4.2.3 스트레인 게이지법을 이용한 축 불균형(run-out)량 계산방법 67 제 5 장 선체 변형을 고려한 추진축계 안정성 평가 69 5.1 선체 변형을 고려한 축계정렬 해석 방법 69 5.2 해석 결과 및 고찰 78 5.3 소결론 89 제 6 장 계측치 역분석을 통한 추진축계 안정성 평가 91 6.1 계측 및 데이터 분석 방법 91 6.2 선체 변형량 예측 및 베어링 반력 계산 결과 96 6.3 소결론 104 제 7 장 축계 횡진동 분석 105 7.1 횡진동 계산 및 분석 방법 105 7.2 결과 및 고찰 107 7.3 소결론 116 제 8 장 가속 및 직진시 축 거동상태 분석 119 8.1 계측 및 데이터 분석 방법 120 8.1.1 측정 설비의 구성(configuration) 120 8.1.2 계측 절차 123 8.1.3 원 신호(raw data)의 처리 124 8.1.4 진동 원인별 궤도(orbit)형태 분석 127 8.2 동적 상태 계측(dynamic measurement) 130 8.2.1 만재흘수 조건(full laden APT tank full -
dc.description.tableofcontents NBE) 139 8.3 소결론 153 제 9 장 결 론 155 참고문헌 157 -
dc.description.tableofcontents FLF) 130 8.2.2 밸러스트 흘수 조건 (ballast APT tank empty -
dc.language kor -
dc.publisher 한국해양대학교 대학원 -
dc.title 중형 석유화학제품 운반선의 추진축계 안정성 평가에 관한 연구 -
dc.type Thesis -
dc.date.awarded 2016-08 -
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