Underwater submarine propeller12/20/2023 ![]() But there is an increase in noise levels at very low frequencies, most likely due to the increase in cavity volume.Rear Admiral Ma presents a component of the new Chinese IEPS for naval warships the Chinese variant is the world’s first IEPS to run on a medium-voltage, direct-current system.Īlso in the video background was a large piece of electrical machinery, which is part of the PLAN’s Integrated Electrical Propulsion System (IEPS). Preliminary results have shown that it’s possible to achieve significant noise reduction. This idea has been evaluated before and shown some potential, which is why MARIN assessed it for the Streamline tanker. An alternative approach is to inject air bubbles from the hull upstream of the propeller. However, manufacturing such a propeller blade is challenging and, as a result, expensive. In what is known as the Prairie system, the bubbles are injected in the flow-through holes in the propeller blade. Preliminary results indicate that the noise reduction may be more than 20 decibels.Īir bubbles can also be used to reduce cavitation noise: if the cavity contains a sufficient quantity of air, it collapses more slowly, reducing the volume of radiated noise. ![]() A metal midsection has been designed, manufactured and tested using a shaker to mimic machinery vibrations, and porous hoses have been mounted on the ship’s hull upstream of the metal midsection to inject air. MARIN has evaluated the Masker system for a one-propeller tanker known as the Streamline. In addition, more and more ships are now equipped with air lubrication systems that can reduce their hulls’ frictional resistance, cutting down on both fuel use and carbon emissions.Ĭombining the two approaches-air bubble injection and air lubrication systems-may produce a win-win situation when it comes to fuel efficiency and underwater noise. There is no quantitative information in the open literature about the resulting noise reduction, but this solution is still an interesting possibility for ships equipped with two-stroke diesel engines because there are currently no other promising noise mitigation measures available for these. Using the Depressurized Wave Basin, a unique research facility for testing ships and offshore structures in realistic operational conditions, MARIN has also experimented with two solutions that use air-bubble injection.Īir bubble injection below a ship’s hull to lessen machinery noise, known as the Masker system, has been used on military naval vessels before. Reducing both noise and fuel use: a win-win And two Netherlands firms, MARIN and Wärtsilä, are designing a new propeller that uses modern automated design techniques to reduce noise. Meanwhile, Sirehna, a subsidiary of Naval Group, the French naval shipyard, has been developing a trochoidal propeller whose blade motion resembles that of whale’s tail, and recently tested it on a French lake. The design is nearing completion and will be tested by the Italian Institute of Marine Engineering at the end of this year. (A twin-screw ship has two screw propellers, which usually revolve in opposite directions.)įor example, CETENA, an Italian research and consultancy firm, is studying a pump-jet propulsor-a special combination of propeller and duct that can be used on submarines to make the propeller quieter. ![]() ![]() Various organizations are exploring potential retrofits to replace the propellers on a twin-screw ferry. Cavitation-the formation and implosion of small bubbles on propellers as they rotate-causes vibration and significant underwater noise that can radiate across large distances. As a result, many of the noise-reduction technologies being studied today focus on these. Next to machinery noise, ships’ propellers are the dominant source of noise on most ships. ![]()
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