The developing of polar ships is an important support of the polar strategic target in China, while the multi-working conditions of ships sailing in polar ice regions complicate the strength design of the propulsion machinery system - the heart of a vessel. The design principle and the corresponding rules and specifications for the strength of the propulsion shafting of DNV are introduced to ensure the reliability and safety of the ships sailing in polar regions. Regarding the impact of the ice load excitation on the propulsion system and the shafting components, DNV recommends a digital solution considering the excitation of the diesel engine cylinder and the phase angle of the ice load excitation based on its experience. In the current study, the Nauticus Machinery software developed by DNV is used to calculate the torsional vibration of a PC4 polar ship in time and frequency domain. The shafting dimension is then evaluated by using the Palmgren-Miner linear damage rule, and the results of the time-domain analysis are compared with those of the frequency-domain analysis. An iteration procedure has been provided for the design and optimization of the shafting dimension aiming at the strength design of the propulsion shafting for polar ships.

In view of the oil and gas pollution caused by the ventilation of the fuel oil storage tank to the main deck, an optimal design scheme and a systematic design process have been proposed according to the characteristics of the closed overflow ventilation system of the fuel oil storage tank. It is proved that the optimal design scheme can meet the system design requirements and avoid the oil and gas pollution on the main deck through the combination of theoretical calculation and CFD simulation of a 2 200 TEU container ship.

The 3D method for the radar mast design is put forward based on CATIA V6 platform. It comprehensively considers the practical design requirement of the radar mast and the technical difficulties of 3D model. The problems of the associated design, efficient modeling and 3D drawing in the design process of a radar mast are solved by using the multiple software functions, such as the multi-level skeleton, solid modeling, knowledge engineering and secondary development of drawing. The practical results show that the iterative efficiency and the design quality of the 3D design of the radar mast can be significantly improved by using the proposed 3D design method. This design method can also be applied to other truss-type structures except the radar mast and even more other steel structures, according to the analysis of other specific design scenes.

The design scheme of the variable frequency fan for a 20 000 TEU container ship is given as the optimum efficiency point of the engine-room fans under the variable working conditions are determined by fitting the efficiency curve. The energy-saving effect that can be produced by installing the variable frequency system on the engine-room fan is estimated by analyzing the environmental climate and the different working conditions of the typical Eurasian routs. A reasonable economic benefit analysis method is finally put forward for the fan with the variable frequency system.