The International Maritime Organization(IMO) has proposed the implementation of monitoring systems for URN, which could lead to the creation of specific thresholds along with long-term monitoring requirements. In this scenario, the HyPNoS research project, led by SCHOTTEL, a global propulsion systems specialist, together with Transport Canada and BC Ferries, has investigated URN emission from marine propulsion systems in the waters off Vancouver, Canada.
The HyPNoS research project
The“HyPNoS project” set as its main objective to develop effective methods for measuring, predicting and reporting URN emissions, as well as deriving optimized design measures to reduce them. This effort culminated in the creation of a real-time URN reporting system, available on board for crew and ship operators.
This technology responds to the need to protect sensitive environmental areas, where URN emission can cause damage to marine wildlife. Until now, speed reduction has been a common practice to mitigate noise, but it does not always result in effective URN abatement. HyPNoS has addressed this issue with a technical approach that includes research on the direct relationship between hull vibration on the propeller and underwater noise.
The project focused its research on a series of double-ended ferries in Canada, exploring the possibility of reducing underwater noise using a URN monitoring system based on state-of-the-art machine learning technology. This system was designed with the protection of the Southern Resident killer whales, a group of whales that inhabit the Strait of Georgia near Vancouver in mind. The development of this prototype allows the crew to take immediate operational measures to reduce URN during operation.
Studies on the measurement, calculation and prediction of the URN
The HyPNoS approach to measuring URN included detailed analysis of hull vibrations and underwater noise measurements with hydrophones. This investigation revealed a quantitative correlation between the vibrations and the noise generatedThis allowed SCHOTTEL engineers to develop an advanced algorithm for calculating and predicting URN. This algorithm can “consider additional factors” such as propeller speed, propeller pitch and ship speed.
The research was carried out on BC Ferries’ Coastal Class vessels in Canada, as well as at SCHOTTEL’s facilities in Germany. In which, two propeller designs were tested: the original and a design optimized for noise reduction. The latter showed an average decrease in URN by 5 decibels, even though the propeller diameter was reduced from 5 to 4.7 meters, demonstrating the effectiveness of adapting propulsion systems to more modern designs.
Another objective of the project was to raise operator awareness of the impact of URN through a real-time reporting system. This system will allow operators to react to elevated noise levels and take corrective action, while delineating historical and full fleet-level assessments through a cloud-based system. This could be useful for providing information on noise emission characteristics to authorities, organizations or the public.
Future applications of the technology
The results of the HyPNoS project indicate that it is possible to meet IMO requirements for URN monitoring systems with minimal input, such as vibration measurement, which is sufficient to provide an assessment of the generated underwater noise. In addition, it was evidenced that modifications to the propeller design can be an effective measure to reduce URN. This research also demonstrated that it is possible to predict URN at the propeller design stage, allowing different designs to be compared and rated more effectively.
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Source and photo: Schottel
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