Numerical investigation of after stern tube bearing during ship turning maneuver
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ORIGINAL ARTICLE
Numerical investigation of after stern tube bearing during ship turning maneuver Hongjun Yang1 · Yuxin Zhang1 · Liping Lu1 Received: 23 April 2019 / Accepted: 3 September 2019 © The Japan Society of Naval Architects and Ocean Engineers (JASNAOE) 2019
Abstract Large propeller lateral loads during ship turning maneuver may cause serious damage on after stern tube bearing. Failure of after stern tube bearing frequently occurs, especially when environmentally acceptable lubricants are used in the ship’s stern tube. Therefore, a new design rule for after stern bearing is urgently needed. This paper presents a numerical investigation on the oil film performance of the after stern tube bearing of a super handy-max bulk carrier in turning maneuver. Computational fluid dynamics is adopted to estimate the propeller lateral forces and moments, which are introduced into the shafting alignment calculation. In shafting alignment analysis, the after stern tube bearing is divided into several bearing segments, and the midpoint of journal segments is used to characterize the deflection of the journal centerline. The accurate deflection of the journal center of the after stern tube bearing is obtained through the iteration of the shafting alignment program and Reynolds equation. Moreover, the distribution of oil film pressure and the minimum oil film thickness are recorded. Finally, the criterion for oil film is discussed. Keywords After stern tube bearing · Ship maneuvering · Oil film performance · Computational fluid dynamics (CFD)
1 Introduction With the recent application of environmentally acceptable lubricants in stern tubes, the bearing failure due to high temperature during the maneuvering test of a new building ship has caused huge economic losses to shipyards and ship owners. Therefore, the performance of after stern tube bearing during ship maneuvers has gained increasing attention in shaft system design. To reduce the risk of high temperature in the maneuvering test, certain shipyards must add special running procedures for after stern tube bearing during sea trial. However, the running procedures increase the test time of sea trial and the shipyard cost. Det Norske Veritas proposed an additional stringent requirement for after stern tube bearing. DNVGL released a class notation for shaft alignment, which has gained widespread attention in the ship building industry. Detailed analysis and evaluation of the after stern tube bearing of the shafting alignment are
* Yuxin Zhang [email protected] 1
Shanghai Merchant Ship Design and Research Institute, CSSC, Shanghai 201203, China
required to meet the requirements of all parties, especially ship owners and operators. Large merchant ships often use a propulsion system consisting of a main engine and screw propeller. The propeller is mounted on the stern part of the ship, and the shaft is utilized like a cantilever beam. In the design of the bearings of the shaft system, the after stern tube bearing is often placed near the propeller to bear the load f
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