Analysis and experiments for contra-rotating propeller

Abstract

Contra-rotating propellers have renewed interest from the naval architecture community, because of the recent development of electric propulsion drives and podded propulsors. Contrarotating propulsion systems have the hydrodynamic advantages of recovering part of the slipstream rotational energy which would otherwise be lost utilizing a conventional screw propeller system. The application of this type of propulsion becomes even more attractive with the increasing emphasis on fuel economy and the improvement of the propulsive efficiency. OPENPROP is an open source propeller design and analysis code that has been in development at MIT since 2007. This thesis adds another feature to the project with the off design analysis of a contra-rotating propeller set. Based on this code, the thesis offers a comparative analysis of two types of propulsors: a single propeller and a contra-rotating propeller set, which were designed for the DDG-51 destroyer class vessel. This thesis also presents the method for using these off-design analysis results to estimate ship powering requirements and fuel usage. The results show the superiority of the contra-rotating propeller over the traditional single propeller, with increased propeller efficiency of about 9% at the design point and up to 20% at some of the off design states. The annual fuel consumption savings for the DDG-51 equipped with a CRP was a total of 8.8% fuel savings.