Introduction to CoPropel: composite materials for marine propellers to reduce fuel consumption and underwater radiated noise
Topic(s) : Industrial applications
Co-authors :
Clement RETIERE (FRANCE), Maël MORET (FRANCE), Aldyandra Hami SENO (UNITED KINGDOM), Nithin Amirth JAYASREE , Mihalis KAZILAS (UNITED KINGDOM)Abstract :
Marine propellers are commonly made from metals using a combination of casting and machining to obtain a monolithic component with a smooth hydrodynamic shape. The result is a strong and stiff component that can have very complex geometries with very thin edge thicknesses. However, this also comes with drawbacks associated with operation and maintenance throughout its lifetime. This study presents the overview of the Horizon EU and Innovate UK funded CoPropel project which aims to develop novel composite propellers to address the drawbacks associated with current metallic ones. We will highlight the main aspects being targeted for improvement and how the work in the CoPropel project is addressing them.
Large diameter metallic propellers on large ships can be very heavy which results in the need for special equipment for handling and installation. The weight also results in large inertia which creates the need for a stronger and more powerful engine/shaft setup to rotate the propeller. The use of composite materials enables a non-monolithic construction of the propeller, consisting of several composite blades, with carbon fiber fabrics and an epoxy matrix, assembled on a hub. This results in a lightweight but strong structure, which based on the consortium’s experience manufacturing prototypes can be 50-60% lighter than metallic propellers. This reduces the requirements from the handling and burden on the propulsion system side leading to potential cost savings from maintenance and fuel efficiency. An added benefit is the inherent fatigue tolerance of composite materials which results in better long-term reliability.
Hydrodynamics wise, metallic propellers are geometrically rigid and thus are optimised for a specific operational regime which is mainly the RPM range for cruising. On the other hand, with composite propellers there is the possibility to tailor the stiffness of the blade by varying the reinforcement configuration (fibre angles, etc.) resulting in a “flexible” blade. This flexible behaviour can be designed in such a way that the blade will hydroelastically deform to match the optimum shape at a wider range of RPMs resulting in better overall boat fuel efficiency. Additionally, this flexible behaviour can be tailored to reduce very low-pressure regions on the blade edges which commonly cause cavitation at high RPMs. This leads to increased operational life of the blade as cavitation can chip away at the blade surface and significantly reduce its efficiency. Finally, flexible propellers produce less underwater radiated noise when they rotate, leading to lower environmental impact during operation.
The project is currently in the design phase of the propeller blade and will be conducting small scale propulsion and cavitation tests to verify the performance. This will inform the design of a large scale propeller blade which will be used in full scale sea trails at the end of the project.
Large diameter metallic propellers on large ships can be very heavy which results in the need for special equipment for handling and installation. The weight also results in large inertia which creates the need for a stronger and more powerful engine/shaft setup to rotate the propeller. The use of composite materials enables a non-monolithic construction of the propeller, consisting of several composite blades, with carbon fiber fabrics and an epoxy matrix, assembled on a hub. This results in a lightweight but strong structure, which based on the consortium’s experience manufacturing prototypes can be 50-60% lighter than metallic propellers. This reduces the requirements from the handling and burden on the propulsion system side leading to potential cost savings from maintenance and fuel efficiency. An added benefit is the inherent fatigue tolerance of composite materials which results in better long-term reliability.
Hydrodynamics wise, metallic propellers are geometrically rigid and thus are optimised for a specific operational regime which is mainly the RPM range for cruising. On the other hand, with composite propellers there is the possibility to tailor the stiffness of the blade by varying the reinforcement configuration (fibre angles, etc.) resulting in a “flexible” blade. This flexible behaviour can be designed in such a way that the blade will hydroelastically deform to match the optimum shape at a wider range of RPMs resulting in better overall boat fuel efficiency. Additionally, this flexible behaviour can be tailored to reduce very low-pressure regions on the blade edges which commonly cause cavitation at high RPMs. This leads to increased operational life of the blade as cavitation can chip away at the blade surface and significantly reduce its efficiency. Finally, flexible propellers produce less underwater radiated noise when they rotate, leading to lower environmental impact during operation.
The project is currently in the design phase of the propeller blade and will be conducting small scale propulsion and cavitation tests to verify the performance. This will inform the design of a large scale propeller blade which will be used in full scale sea trails at the end of the project.