What is described as a ‘revolutionary’ propeller hub vortex cavitation-eliminating boss cap has successfully completed validation tests at a hydrodynamic research centre in Sweden.
The propeller hub – which could provide gains in propulsive efficiency for a wide range of vessels, including warships – will now undergo ship model basin trials to verify the efficiency gains on larger commercial and naval vessels.
Initial computational fluid dynamic (CFD) tests based on a typical twin-screw vessel with V-brackets and a 90m general cargo ship showed that EcoMarine Innovations’ Holy Boss Cap (HBC) – named thus to indicate the holes bored into the conically shaped hub – increases propulsion efficiency by up to 5%, compared to conventional propeller boss caps.
Tests also assessed the patent-pending HBC against more advanced energy efficient boss caps currently in operation, and found they are at least 3% more efficient.
“Overall, compared to the propeller boss caps that are currently available, the HBC improved propeller efficiency by 3.1% and thrust by 1.1%, while reducing torque by 2%, rudder cavitation by 10%, and propeller induced noise by 1-3dB,” explained Dr Batuhan Aktas, CEO of EcoMarine Innovations, a ship research and development group at the University of Strathclyde, Glasgow.
“The Holy Boss Cap completely eliminates propeller hub vortex cavitation, the main source of rudder erosion, and reduces associated propeller efficiency losses, which can be as much as 8%.
“Considering the investment levels required for other energy saving devices currently in the market and the potential fuel savings, we believe that the Holy Boss Cap is a game changer with and ROI of less than six months,” he said.
“With shipowners grappling with new environmental legislation and emissions reporting rules, zero propeller hub vortex cavitation can help towards ESG, EEXI and CII goals, improve efficiency and reduce the costs associated with cavitation induced rudder erosion,” said EcoMarine Innovations’ chief technical officer Dr Ahmet Gurkan.
“What we have designed is a propeller boss cap that is more efficient and costs 50% less to manufacture than current conventional propeller hubs. Considering the minimal investment required, this is a significant level of saving,” Dr Gurkan said.
“We are delighted that CFD trials have validated the concept and will now take the development to the next stage and start secondary model tests.” He said the tests were due to start in March 2024.
