Water-lubricated bearings of ship propeller shafts - problems, experimental tests and theoretical investigations
In recent years can be met ships whose propeller shaft polymer bearings are lubricated with water. It results from simplicity and associated low cost of such solution which is also environmentally friendly as no risk of pollution is involved. However the solution is not free of disadvantages. The main problem is intensive wear of bush material, occurring in certain cases. It very often results from errors of improper design and machining and mounting operations. Another problem is a limited value of its hydrodynamic load-carrying capacity, resulting from low viscosity of water used as a lubricating medium.
As results from the performed research investigations, bearing of the kind is a highly sensitive unit. Problems of choosing a suitable bearing clearance, designing an optimum bush geometry, selecting a proper bush material are crucial for lifitime of the bearing.
Influence of main design parameters of ship propeller shaft water-lubricated bearings on their properties
In recent years more and more frequently can be met ships in which propeller shaft water-lubricated polymer bearings have been applied. It results from their simplicity and associated relatively low initial and operational cost as compared with the complex classical sealed system based on oil-lubricated bearings. It is worth mentioning that the water-lubricated bearings are also environmentally friendly as no risk of pollution with lubricating oil used in classical systems, is involved. Design procedure of bearings in question based on materials made available by producers is relatively simple. However it turns out that choice of an appropriate sliding material, clearance value and optimum arrangement of lubricating grooves may greatly influence bearing's properties. As results from the performed research investigations, bearing of the kind is a highly sensitive unit. Problems of choosing a suitable bearing clearance, designing an optimum bush geometry, selecting a proper bush material are crucial for life time of the bearing. In particular the problem is in forming hydrodynamical properties of bearing as owing to its operation in the fluid friction regime durability of bearings, the very responsible units of propulsion transmission system, can be greatly extended.
Influence of local bush wear on properties of water lubricated marine stern tube bearings
In recent years more and more frequently can be met ships in which propeller shaft water-lubricated polymer bearings have been applied. It results from their simplicity and associated relatively low initial and operational cost as compared with the complex classical sealed system based on oil-lubricated bearings. It is worth mentioning that the water-lubricated bearings are also environmentally friendly as no risk of pollution with lubricating oil used in classical systems, is involved. Design procedure of bearings in question based on materials available from their producers is relatively simple. However the calculating of such bearings creates many problems. For calculating the hydrodynamic lubricating theory is as a rule used and elastic bush flexibility taken into account. In the case of greater loads when lubricating film is very thin to achieve a proper solution is very difficult.
For this reason is proposed a novel method in which bush local wear effect can be accounted for. Such phenomenon has been observed during experimental tests of heavy-loaded water-lubricated slide bearings. With the use of the applied calculation algorithm bush local wear close to its edges can be taken into account, and - in consequence - a greater bearing capacity can be achieved.
Since a few years students of the Faculty of Ocean Engineering and Ship Technology, Gdansk University of Technology, have designed and built untypical floating units. Until last year their efforts were focused mainly on leg-driven boats. The boats of interesting design have taken part in yearly competitions: the International Waterbike Regatta. Their advanced design made it possible to compete with the best boats from Croatia, Holland, Germany, Turkey and Italy. Recently the students have designed and built a solar-energy-driven boat. It is the catamaran Energa Solar which took part in a prestigious regatta: the Frisian Nuon Solar Challenge carried out in Holland in summer 2006.
Wojciech Litwin, Wojciech Leśniewski and Jakub Kowalski
The development and growing availability of modern technologies, along with more and more severe environment protection standards which frequently take a form of legal regulations, are the reason why attempts are made to find a quiet and economical propulsion system not only for newly built watercraft units, but also for modernised ones. Correct selection of the propulsion and supply system for a given vessel affects significantly not only the energy efficiency of the propulsions system but also the environment - as this selection is crucial for the noise and exhaust emission levels. The paper presents results of experimental examination of ship power demand performed on a historic passenger ship of 25 m in length. Two variants, referred to as serial and parallel hybrid propulsion systems, were examined with respect to the maximum length of the single-day route covered by the ship. The recorded power demands and environmental impact were compared with those characteristic for the already installed conventional propulsion system. Taking into account a high safety level expected to be ensured on a passenger ship, the serial hybrid system was based on two electric motors working in parallel and supplied from two separate sets of batteries. This solution ensures higher reliability, along with relatively high energy efficiency. The results of the performed examination have revealed that the serial propulsion system is the least harmful to the environment, but its investment cost is the highest. In this context, the optimum solution for the ship owner seems to be a parallel hybrid system of diesel-electric type
Jakub Kowalski, Wojciech Leśniewski and Wojciech Litwin
In the Faculty of Ocean Engineering and Ship Technology, Gdansk University of Technology, design has recently been developed of a small inland ship with hybrid propulsion and supply system. The ship will be propelled by a specially designed so called parallel hybrid propulsion system.
The work was aimed at carrying out the energy efficiency analysis of a hybrid propulsion system operating in the electric motor drive mode and at performing the noise pollution measurements.
The performed investigations have shown that a significant impact on the efficiency and on the acoustic emission has the type of belt transmission applied.
Paweł Gełesz, Artur Karczewski, Janusz Kozak, Wojciech Litwin and Łukasz Piątek
Dynamic development in practically all fields of science and engineering has not passed over shipbuilding. In last years, engineers got to their use computer software which makes it possible to perform strength and hydrodynamic calculations as well as to visualize design projects in 3 D space [1-4]. At their disposal they have full spectrum of modern solutions associated with the use of advanced materials and technologies [5-7]. More and more attention is also paid to impact onto the natural environment [8,9]. Every new object must influence the environment as low as possible, beginning from building phase through its service life up to final utilization - such approach is called „green-shipping“. However, not only practical reasons are important. Clients, i.e. ship owners and passengers of ships paid more and more attention to image of floating units. During decision taking on that from whom a transport service has to be ordered, the most modern ships of an attractive image matching with place and time, are often taken into consideration.
Such situation has become a basis for an idea of working out a concept of a new ferryboat for National Maritime Museum. As the ferry has to navigate in „the heart of the town“, then, apart from strictly marine and engineering aspects, an important factor of its designing is its expected image - a set of significant meanings and emotions written in architecture language. The new ferryboat, like its historical predecessors, will never leave urban water routes.
Water-lubricated bearings have been applied to support ship screw shafts for over a hundered years.Development of plastic materials has caused that novel sliding polymers appeared available on the marketand being approved by classification institutions, possible to be applied in shipbuilding. However in thesubject - matter literature there is no reference to application of bearings fitted with metal or ceramicbushes in shipbuilding. Nevertheless they have important merits such as low resistance to motion, longservice life or stability of form. But some doubts are evoked by their large value of shape elasticity modulewhich can lead to local stress concentration at the bush edges in the case of non-axiality of bush and shaftaxes. Hence this work has been aimed at the testing of a bearing made of bronze-graphite silter. In thework is presented a comparison of measurement results of resistance to motion , hydrodynamic pressuredistributions in lubricating film as well as shaft axis trajectories of the bearing, with those made for a typicalelastic polymer bearing. The measurement results have showed high quality of the tested material. In theopinion of these authors it could be applicable to bearing ship propeller shafts.
In recent years, there has been a significant development in “green” and energy efficient propulsion systems, which fits into the general trend of environmentally friendly “green shipping”.
The pursued goal is to construct a safe passenger ship that is low in energy demand and equipped with a highly energy efficient, emission-free propulsion system.
The paper presents main problems encountered by designers of a small, hybrid-powered ferry powered lithium batteries. The conducted research allowed to create a design of an energy efficient hull shape, which decreases the demand for energy. Completed remote control model tests resulted in a proposal of an energy efficient and safe propulsion system with good manoeuvring capabilities. Measurements completed on an existing ferry permitted completing energy balance and forming an energy management policy.
The paper contains the emission calculations computed for the existing ferry that are necessary for the environmental impact analysis.
The soon to be constructed, newly designed vessel will provide a valuable contribution to hybrid-propulsion, energy management and unmanned technologies research.
Agnieszka Barszczewska, Ewa Piątkowska and Wojciech Litwin
This paper presents typical methods for conducting experimental tests on main shaft slide bearings. There are described their possible testing capabilities, advantages, drawbacks and limitations. Various testing methods were analyzed to find a solution able of providing a wide range of possible investigations at possibly acceptable limitations.