Process for ship pre-swirl stator retrofit attachment design
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Insinööritieteiden korkeakoulu | Master's thesis
Nordic Master Programme in Maritime Engineering
AbstractConcerns for global warming is leading the actual rule frameworks towards environmentally guidelines. IMO´s attempts to enforce the energy efficiency design index (EEDI) are pushing ship operators to develop energy saving devices. These devices are meant to fulfil the requirements imposed by rules and regulations to avoid possible legislative consequences to ship operators. In addition, those devices become very attractive when their installation reduces the fuel consumption. Due to the lack of rules and guidelines on the matter of fin structural assessment, a practical process is proposed to perform a Pre-swirl stator attachment design. Hence, the overall target of this thesis is to state a sequence of steps to develop and improve the design of the Pre-swirl stators attachment. This report seeks to describe a framework methodology that can be applied to any ship and its usability is applied to a case study. By means of a project planning steps it was possible to identify the factors involved in the design of the fin attachment. The process was applied at the very beginning of the project design phase to understand the fin connection context. This method was used first to state the problem definition. Then, project goals and requirements were formulated. With those in mind, several alternatives were studied. The alternatives were considered or dismissed based on selected evaluation criteria that brought a set of optimal solutions. Finally, with a compromise between all the possible solutions, the most convenient option was selected. Design rules for a similar structure such as rudder were used to create the design process for the fin attachment. Notice that the design process proposed in this thesis considers certain aspects that are not considered in new build ships. Performance time and harmless manufacturing procedures (for the surrounding systems) are examples of factors that are included in this process and are not stated on similar design methodologies. The process outlines all substantial factors concerning reliability, performance, quality and manufacturing time of the fin connection. In order to satisfy these aspects, the ultimate strength and fatigue of the connection piece needs to be assessed. In addition, immense attention is focused on the welding technique as this determines the time and cost of the fin installation procedure. Furthermore, the welding affects the reliability and performance in terms of joint connection strength and potential shaft misalignment due to excess heat induced in the area. The main factors affecting the attachment design are evaluated using several design alternatives to better understand how the different factors affect the overall outcome.
Thesis advisorHakulinen, Petri
pre-swirl stator, power saving device (PSD), fin attachment, retrofit, welding time, strength assessment