Description
The Teignbridge Clamp on Blade (CoB) propeller is an innovative, UK patented and worldwide patents pending, replaceable blade propeller designed for operational flexibility and maximum hydrodynamic efficiency. The CoB propeller has been developed in partnership with the Energy Technologies Institute as part of a 3-year, development and demonstration project focused on improving the efficiency of ship propellers with the aim of reducing fuel consumption and associated greenhouse gas emissions. The CoB propeller is suited to a wide variety of applications including merchant, commercial, military and leisure vessels and can be supplied in a wide range of sizes from 0.75m to 5.50m diameter with keyed or hydraulic shaft fitting. A 5.5m diameter propeller can be packaged and transported in a 20ft shipping container. With a hub diameter ratio typically only 5% higher than a conventional mono-bloc fixed pitch propeller, the patented blade clamping design of the Teignbridge CoB represents the lowest hub to diameter ratio, replaceable blade propeller currently on the market, maximising the propellers surface area, therefore generating the greatest possible thrust. Unlike alternative, radially bolted solutions, Teignbridge’s CoB propellers hydrodynamic efficiency is further improved by minimising the number of bolt heads present on the hub surface resulting in improved flow over and around the hub. In the unfortunate event that propeller blades become damaged during use, the individual blades can be replaced rather than having to remove and replace the whole propeller. This feature of the CoB system saves the time and cost of having to dry dock or slip the vessel. As CoB parts can be stored onboard, there is no wait for replacement parts to be manufactured or repaired, reducing the costly downtime period of the vessel. For smaller vessels and superyachts, the modular design provides an economical and flexible option, with blade changes only requiring the services of a diver for propellers up to 1.2 metres diameter. The increased ease with which propellers blades can be changed also means that long-term changes in vessel use profile can be matched with a revised propeller design, improving efficiency, reducing emissions and saving fuel with rapid return on investment for the customer. The component parts of the CoB propeller are fully CNC machined to ensure dimensional accuracy in the initial assembly and interchangeability of replacement blades. This means that operators can carry a single, replacement blade instead of a full replacement propeller, freeing up deck/engine room space. The CoB has been developed and tested using Teignbridge Propeller’s purpose-built Hydrodynamic Research Vessel (HRV1) to validate and correlate in-house Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) structural simulation work. Additional in-house destructive physical testing has been used to further validate the structural integrity of the CoB. Carbon fibre composite propeller blades, designed utilising Teignbridge Propellers Clamp on Blade (CoB) technology produces a lightweight and efficient propeller which due to the carbon fibre material characteristics, yields lower driveline vibrations combined with substantial noise reduction compared to conventional metallic propellers. This is extremely beneficial when coupled with electric drive where controlling NVH (Noise, Vibration, Harshness) levels are of upmost importance. Carbon fibre construction allows the characteristics of a propeller to be tailored, adding strength and stiffness where needed, achieved by orientating the fibre layup and thickness, while reducing weight to produce an efficient product. Flexibility can be designed into the blade so that the loading on the propeller during use allows controllable blade deflection, meaning that cavitation inception is restrained. Flexibility creates a damping effect yielding lower vibration and noise reduction, compared to metallic propellers. Lighter weight means smaller diameter shafts can be utilised as the moment of inertia is reduced, putting less loading on other parts of the driveline. The physical properties of a composite propeller allows for an optimum propeller design that can absorb all of the power supplied by the power unit (combustion engine or electric motor) throughout the defined working range of revolutions, this is not possible with conventional metallic versions.
