Basic Principles of Ship Propulsion

Abstract

For the purpose of this paper, the term “ship” is used to denote a vehicle employed to transport goods and persons from one point to another over water. Ship propulsion normally occurs with the help of a propeller, which is the term most widely used in English, although the word “screw” is sometimes seen, inter alia in combinations such as a “twin-screw” propulsion plant. Today, the primary source of propeller power is the diesel engine, and the power requirement and rate of revolution very much depend on the ship’s hull form and the propeller design. Therefore, in order to arrive at a solution that is as optimal as possible, some general knowledge is essential as to the principal ship and diesel engine parameters that influence the propulsion system. This paper will, in particular, attempt to explain some of the most elementary terms used regarding ship types, ship’s dimensions and hull forms and clarify some of the parameters pertaining to hull resistance, propeller conditions and the diesel engine’s load diagram. On the other hand, it is considered beyond the scope of this publication to give an explanation of how propulsion calculations as such are carried out, as the calculation procedure is extremely complex. The reader is referred to the specialised literature on this subject, for example as stated in “References”.