Air Emissions Propeller Technology Reduces Underwater Noise
The naval sector has been using Kongsberg Blade Air Emission technology for a number of years now to limit vessel signature. The company now also offers the technology for commercial ship propellers to reduce the effect of underwater radiated noise on marine life.
By machining a channel into the leading edge of the propeller blades, the Blade Air Emissions concept significantly reduces cavitation-induced noise and erosion. On the one hand, reduced noise is beneficial to marine life. On the other hand, damage to the propeller caused by cavitation erosion is reduced. The concept can be applied to both fixed pitch and controllable pitch propellers.
Finding an Equilibrium
The silent propeller was developed at the Kongsberg Hydrodynamic Research Centre (KHRC) in Kristinehamn, Sweden. By carefully balancing the amount of air circulated around the blades, the negative effects of cavitation are reduced without adversely affecting ship efficiency.
According to Robert Gustafsson, Senior Hydrodynamicist at KHRC, there is an equilibrium. '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.'
Picture by Kongsberg.