Abstract
The presence of broken ice in the flow field around a propeller causes severe blade erosion, shafting, and hull vibration. This study investigates the performance of the propeller of a ship sailing in the polar regions under the propeller–ice non-contact condition. To this end, we construct a test platform for the propeller-induced excitation force due to ice blockage in a large circulating water channel. The hydrodynamic load of the propeller, and the cavitation and propeller-induced fluctuating pressure, were measured and observed by varying the cavitation number and ice–propeller axial distance under atmospheric pressure and decompression conditions. The results show that the fluctuation range of the blade load increases with a decrease in cavitation number and ice–propeller axial distance. The decrease in the cavitation number leads to broadband characteristics in the frequency-domain curves of the propeller thrust coefficient and blade-bearing force. Under the combined effects of ice blockage and proximity, propeller suction, the circumfluence zone around the ice, and the Pirouette effect, propeller–hull vortex cavitation is generated between the ice and propeller. The decrease in cavitation number leads to a sharp increase in the amplitude of the high-order frequency of the propeller-induced fluctuating pressure.
Highlights
IntroductionWhen polar-class ships navigate in frigid zones, broken fragments of ice frequently sink along the hull and gradually flow against its surface
The results showed that the order of the propeller cavitation excitation force significantly increased owing to ice blockage
We study the influence of ice-blockage parameters, ice–propeller axial distance and cavitation number, on the propeller hydrodynamic performance, cavitation, and excitation force under different
Summary
When polar-class ships navigate in frigid zones, broken fragments of ice frequently sink along the hull and gradually flow against its surface. The broken ice slowly approaches the propeller and interacts with it. This induces extreme loads on the latter, leading to a large cavitation area on the back of the blade and reducing its performance. The blades bear the excitation force and transmit it to the hull, resulting in fatigue damage to the main components of the ship, difficulties in onboard operations, equipment failure, poor crew comfort and reduced safety, etc. The study of cavitation and the induced excitation force of ice-class propellers under ice blockage is of significance to ship and marine engineering
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