Shaft and blade load measurements on a highly skewed propeller model in ice

Moores, Corwyn E. W. (2001) Shaft and blade load measurements on a highly skewed propeller model in ice. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (5MB)

Abstract

Recent work pertaining to shipping traffic in Arctic and Sub Arctic regions has resulted in an increased understanding of the loading experienced by the propulsion systems of vessels equipped with highly skewed propellers. Testing completed on model propellers using conventional shaft load measurements indicates that the loading experienced in ice is substantially greater than that experienced in open water. -- The research described herein was completed with the intention of determining the loading experienced by an individual highly skewed blade during the ice interaction process. It documents the results of a series of ice milling tests using a highly skewed propeller model. This 4-bladed model was designed to be tested in the ice tank at the National Research Council of Canada's Institute for Marine Dynamics (IMD). In this series of tests, loads experienced by an individual blade, as well as the conventionally measured shaft loads, were recorded. The blade loads were measured using a purpose built, hub-mounted dynamometer to which one propeller blade was mounted. Testing was completed over a range of pitch settings for the controllable pitch blades, including design, reduced and reverse settings. As well, tests at a range of ice cut depths and advance ratios were conducted to observe the effect of each of these on the blade loads. -- Results from the ice milling tests indicated that during the ice milling event the blade attached to the dynamometer experienced maximum peak loads that were substantially higher than 1/4 of the maximum shaft loads. During the tests, the maximum loads in most cases were observed in the design condition. However, relative increases in load due to ice when compared to the open water loads were seen to rise as the pitch was reduced from the design case. Ice loading effects on the maximum resultant bending moment at the blade root, a common design criterion, were also observed to be significantly higher than the open water case. Based on these observations it is concluded that the regulations for propeller design based on the loading experienced during design pitch operation in open water, with allowances for ice interaction, should be reconsidered for a more detailed design based on ice loading tests. -- In addition to the ice milling tests, a series of compression tests were also performed to determine the effect of temperature and strain rate on the model ice used for the model propeller tests. Results from these tests indicate that EG/AD/S model ice follows a similar stress versus strain rate pattern as fresh and salt water ice. This result lends credence to its use as the modeling medium for propeller ice interaction, where strain rates are higher than in other types of ice-structure interaction phenomena.

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