Analysis Of Using Podded Propulsors

Analysis Of Using Podded PropulsorsOver the past few decades the concept of seedcaseded propulsion in merchant ships has gained significant toleration in the merchant marine industry. Mostly due to the particular that podded propulsion systems offer several expediencys in contrast to the conventional, shaft hinge on arrangement systems. The benefits we go away refer to atomic number 18 mostly manoeuvrability, lower ring generation and more than available space for cargo in merchant vessels. However before discussing the advantages and disadvantages of a podded propulsion system we must first explain what is meant by podded propulsion by briefly analyzing its mechanical components and how they interact with the vessels water resistance and thrust efficacy. nevertheless in secern to fully realize the benefits provided by a podded propulsion system, we also essential to briefly examine several aspects of conventional propulsion systems such(prenominal) as conventional s ingle and double screw propulsion systems, systems employ fixed pitch propellers, contra-rotating propellers, overlapping propellers and controllable pitch propellers which are most usually used today in the propulsion of merchant and navy vessels.Podded Propulsion SystemsA podded propulsion system refers to a gondola shaped pod fit(p) at the stern of the vessel attach on a leg which is capable of rotating in a 360 degrees angle. Inside the pod there is an electrical push back capable of producing thrust by using a fixed-pitch propeller. The entire system is azimuth since there is no need for a rudder or any former(a) steering arrangements ( appendix 1,2). This type of propulsion system was created in the late 1980s by the Kvaerner Masa-Yards in cooperation with the ABB Stromberg Drives and the Finnish Maritime Administration. The first podded propulsion system was mounted onboard icebreakers such as the 16.000dwt M/T Uikku and M/T Lunni tankers. These type of vessels used the p odded propulsion system in order to navigate through the northeastward Passage in extremely harsh conditions by moving backwards with the propeller first, thus breaking the ice with a considerably higher efficiency than before.Today there are several types of podded propulsion systems available, some of the most commonly used are the Mermaid unit ( appendage 3) constructed by Kamewa and Cegelec, the Dolphin unit (Appendix 4) which was produced by stool Crane Lips as well as STN and the SSP Thruster (Appendix 5) which is a product of Siemens and Schottel companies. The Mermaid unit uses a low emissions gas turbine in order to power the propeller which acts as a tractor unit located in front of the pod, this type of propulsion configuration allows an optimum undisturbed water influx to the propeller thus increasing propulsion efficiency and decreasing vibration and noise. The Dolphin unit operates by integrating a powerful electric drive into a hydro-dynamically optimized pod below t he stern of the vessel resulting in a directly driven propeller. The pod is capable of rotating 360 degrees thus ensuring maximum maneuverability composition the power of this unit ranges from 3 MW to more than 19 MW, thus this type of propulsion configuration is suitable for a wide variety of commercial merchant vessels. The SSP Thruster uses two twin propellers one in front of the unit and one in the stern, rotating in the same direction powered by a permanent magnet motor. The propeller located at the stern of the pod uses the rotational energy produced in order to provide thrust by using a pair of hydrofoil fins angled away from the pod thus increasing efficiency of the unit date allowing the same maneuverability as the some other pod units since the whole system is capable of rotating in a 360 degrees angle.Conventional Propulsion SystemsSince the beginning of the development of merchant vessels, for the transportation of antithetic types of products the propulsion systems created compete a significant roll in the advancement of the maritime industry. Over the past two centuries many propulsion designs were created in order to further remediate the speed, fuel consumption and efficiency of merchant and navy vessels.Today the most conventional design propulsion systems for merchant vessels consist from a shaft, which directly drives different types of propellers while it is connected to a gearbox. Power is generated mostly from a high torque diesel engine while a rudder usually located in front of the propeller at the stern of the vessel provides the steering. Research has shown that the use of different types of propellers can produce different results depending on the type of the vessel they are used.Fixed pitch propellers (Appendix 6) created the basis of propeller production in either its mono-block or build-up form. Mono-block propellers are most commonly used today while they stew a broad spectrum of design types and sizes. They can range from those weighing only a few kilograms to those, which can weight around 130 tonnes. Their designs can take off since the blade number of the propeller can be anywhere between two and s plain blades. These kinds of propellers are used to provide propulsion for container vessel, bulk carriers and even high-speed patrol crafts. They offer several advantages in order to solve a variety of propulsion problems such as cavitation effects and excessive noise regeneration.In contrast to the fixed pitch propellers the controllable pitch propellers provide an extra degree of freedom since they can change the blade pitch. Even judgement this type of propulsion system configuration is sensitive to cavitation problems it can provide significant advantages of maneuverability since fine thrust control can be achieved without the need to accelerate the propulsion machinery. Controllable pitch propellers are mostly used in passenger ships, ferries and general cargo vessels, which require frequent be rthing maneuvers.Furthermore to the propulsion configurations we discuss above the use of contra rotating propellers (Appendix 7) can provide several advantages to the merchant marine industry. Contra rotating propellers compromise two coaxial propellers sited one behind the other while they rotate in the opposite direction. The contra rotating propulsion system provides the hydrodynamic advantage of recovering a part of the slipstream rotational energy, which would otherwise be lost. additionally contra rotating propellers are able to balance the torque reaction from the propulsor. This kind of propulsion configuration is most commonly used in excellent high-speed outboard motor units while the use of this kind of propulsion system is non efficient for large merchant vessels since large vessels equip a large shaft line. in the end the last conventional propulsion system we will discuss involves the use of overlapping propellers (Appendix 8). This system uses again two propeller s although in this case the propellers are not mounted coaxially but are each located on separate shaft line systems with the distance between the shaft centerlines being less than the diameters of the propellers. The advantage gained from this type of configurations is to increase propulsion efficiency by achieving as mush benefit as possible from the low-velocity portion of the wake field. patronage the fact of alter propulsion efficiency this kind of configuration may increase the levels of fluctuating thrust and torque thus more research and development must be done before it can be used on large merchant vessels.Advantages and Disadvantages of using Podded PropulsionSince we have briefly examined the mechanical characteristics behind podded propulsion and conventional propulsion systems it is time to discuss several advantages and disadvantages of using podded propulsion in the operations of merchant vessels.As yet, studies have not shown whether pods are more efficient than c onventional shaft lines. There has been much research on the subject, but most studies have been aimed at a specific aspect of pod performance instead of an overall efficiency review. Several advantages have been attributed to pod propulsion systems, such as reduced emissions, lower noise and vibration levels, meliorate steering maneuvering, and braking capabilities. The reduced number of component parts also allows for more flexibility in arranging system machinery, more efficient construction and modify shipyard logistics. On the opposite end of the argument, pods require a greater capital investment, have a 30MW power limitation (per screw), and have been known to suffer losings in power due to the electric propulsion.Specifically by using podded propulsion merchant vessels gain a significant advantage due to the fact that they can achieve an increased space capacity in order to fit more cargo mainly because the engine can be allocated more freely thus decreasing the size of th e engine room. This advantage plays a crucial role for todays shipping companies, which depend mainly in increasing their deadweight tonnage duty in order to reduce their costs by achieving economies of scale. Moreover another(prenominal) crucial advantage of using podded propulsion seems to be the environmental benefits realized not only from reduced gas emissions but also due to the decreased fuel consumption thought good hydrodynamic efficiency. Since fuel consumption is a significant factor when calculating the vessels costs, it is of high importance that the vessel is capable of covering great distances at competitive speeds with as less fuel as possible. Even though today most berthing terminals and major ports invest in increasing the size of their facilities in order to accommodate the larger merchant vessels, maneuverability plays an important role in order to avoid delays and unnecessary costs due to the use of tug assistance. Research has shown that using podded propulsi on can significantly increase the maneuverability of even the largest vessels, since the pod is able to rotate in a 360 degrees angle and thus provide thrust in every direction.Despite the advantages we mention above podded propulsion suffers from several disadvantages. The most crucial disadvantage seems to be that the capital costs associated with the production and use of pods, are a dance band higher than the capital costs associated with the use of conventional propulsion configuration. This is one of the main reasons most merchant vessels are not equipped with podded propulsion. Furthermore another important disadvantage seems to be associated with the power production of podded propulsors. Due to the fact that pods have a 30MW power limitation and they depend on electric propulsion, adapted speed may not be achieved while power losses due to the electric propulsion may be experienced.Finally it is not lento to realistically judge the suitability of pod propulsion for diff erent ship types based on these advantages, disadvantages and limitations. However if we examine more closely reports based on the efficiency of podded propulsion we can derive that pods would be more efficient, fitted in cruise and liner vessels using twin screw configurations and even some small bulk carriers and general cargo vessels, while on the other hand they would not be suitable for large container vessels and tankers which require high power outputs. findingIn this essay we provided the reader with a comprehensive analysis of podded propulsion systems as well as conventional propulsion configurations. We examined several benefits created from the use of both types of propulsion systems, while we furthered analyzed the podded propulsion configuration by also providing several disadvantages experienced in merchant vessels, in order to conclude whether or not podded propulsion systems will be well suited in the operations of todays merchant ships. Finally reports has shown th at even thought there is still a lot of research and development to be done on podded propulsion systems their use on merchant vessels would be more extensive in the future.AppendixAppendix 1 microbe Azipod XO The new generation Azipod takes podded propulsion to a new levelwww05.abb.com/global/scot/scot293.nsf//azipod%20xo_2010.pdfAppendix 2Source Electrical systems in pod propulsion, moderate of Science Thesis of Electric Power Engineering, Lena Bergh Ulrika Helldn,Department of Energy and Environment, Division of Electric Power Engineering, CHALMERS UNIVERSITY OF TECHNOLOGY Gteborg, Sweden, 2007Appendix 3Source Electrical systems in pod propulsion, Master of Science Thesis of Electric Power Engineering, Lena Bergh Ulrika Helldn,Department of Energy and Environment, Division of Electric Power Engineering, CHALMERS UNIVERSITY OF TECHNOLOGY Gteborg, Sweden, 2007Appendix 4Source Podded propulsion drive for cruise liner Seven Seas Voyagerwww.sam-electronics.de/dateien/pad/broschueren/ 1.083.pdfAppendix 5Source Electrical systems in pod propulsion, Master of Science Thesis of Electric Power Engineering, Lena Bergh Ulrika Helldn,Department of Energy and Environment, Division of Electric Power Engineering, CHALMERS UNIVERSITY OF TECHNOLOGY Gteborg, Sweden, 2007Appendix 6Source Marine Propellers and Propulsion, John Carlton, second edition 2007, Published by Elsevier LtdAppendix 7Source Marine Propellers and Propulsion, John Carlton, second edition 2007, Published by Elsevier LtdAppendix 8Source Marine Propellers and Propulsion, John Carlton, second edition 2007, Published by Elsevier Ltd