抄録
The performance of a contrarotating propeller for a medium sized tanker was studied by model experiments both in towing tank and in cavitation tunnel. In this study, the fore propeller was designed to have the same diameter as that of the existing conventional propeller, while a lower speed diesel engine with the same output as the existing one was chosen. Morgan's design procedure based on Lerbs' lifting line theory was applied. To obtain the reliable experimental data, the same dynamometer was used both for open-water and self-propulsion tests. The results of the tests on the contrarotating propeller showed 12% to 14% reduction in power at the design speed in comparison with the corresponding conventional propeller. This rate of power reduction was almost the same as those reported before. Further, no deterioration in cavitation characteristics was expected, judging from the results of cavitation tests. Through the tests, the usefulness of the design method by Morgan was proved.
