Keeping it quiet
Several navies currently deploy KONGSBERG Blade Air Emission technology to limit vessel signature and now the same technology is being made available to commercial shipping. The Blade Air Emission concept significantly reduces cavitation-induced noise and erosion risk; achieved by machining a channel into the leading edge of the propeller blades, the effect of which is the reduction of underwater radiated noise on marine life.
Applicable to conventional fixed pitched and controllable pitched propellers, the Blade Air Emission concept is the result of extensive research undertaken at the KONGSBERG Hydrodynamic Research Centre (KHRC) in Kristinehamn, Sweden.
Robert Gustafsson, Senior Hydrodynamicist, KHRC, said: “Propellers optimised with the Blade Air Emission system have for some time been used on naval vessels to reduce and distort vessel signature. Following the success of the system we can now roll out the concept to the wider shipping industry as a way to reduce propeller noise and erosion risk.”
Kongsberg Maritime can optimise the negative effects of cavitation by carefully balancing the amount of air circulated around the blades without adversely affecting ship efficiency
According to Gustafsson there is a balance to be achieved, “With too much air, the underwater radiated noise increases and propeller efficiency reduces. There is a sweet spot. We can optimise the propeller using this concept to achieve the optimum noise reduction without affecting propulsion performance.”
Göran Grunditz, Manager, KHRC, said: “We see huge benefits in the commercial world for the Blade Air Emission technology. While there are financial advantages in reducing the cost of repairing or replacing propeller blades damaged by cavitation erosion, the concept minimises substantially the underwater radiated noise from a ship’s propeller, which in some cases can be 180dB.
“This is a major environmental problem and is already being considered at a regulatory level. It affects the migratory, reproduction and feeding patterns of marine life, such as dolphins, whales and other species. It also causes high levels of stress for marine life.”
“We are offering the industry a more silent propeller for the benefit of the environment and the ship operator. It’s a real game-change in propeller design,” said Grunditz.