Promas plus nozzle propulsion & manoeuvring system

A natural evolution of the successful Promas, this system unites a new type of nozzle with an optimised propeller, hubcap, rudder bulb and a special rudder profile developed to provide very high steering forces yet minimise drag. It meets the requirements for large pulling power at low speed with a high free-running speed in transit. Components are designed to work together in a ducted system, maximising efficiency and minimising disturbances in the water flow both through and around the nozzle. Developed through CFD testing and analysis, the nozzle is a major advance on the profile used in conventional nozzle propeller installations. In a typical anchorhandler propulsion system it will reduce fuel consumption in transit by 15% or more, and improve bollard pull by around 5%. Depending on the exact requirements the rudder may be either a one-piece design or a medium flap type.

Comparisons

Propulsive efficiency improved

In general, the Promas efficiency gain is in the region of 3 – 8 per cent for single screw, and 2 – 6 per cent for twin screw vessels. Comparison tests between a conventional propeller-rudder system and Promas are shown in the graphs below.

The rudder area, profile shape and position are identical for the conventional and Promas cases in the graphs below. So the increase in efficiency shown is the pure effect of the bulb, hubcap, rudder twist and adapted propeller design.

Improved manoeuvring at low speed

At low speed manoeuvring ie. harbour manoeuvring, a maximum side force and a maximum rudder drag is important. The graph below shows the non-dimensional lift against rudder angle for a single screw vessel.

Key features

• Propeller and rudder designed as a single system for optimum efficiency
• Propulsive efficiency increased by 3 – 8 per cent
• Nozzle option can reduce fuel consumption in transit by 15 per cent or more
• Improved low speed manoeuvrability
• Improved possibility for low pressure pulse/low noise propeller design
• Almost as easy to install as a conventional propeller-rudder system
• Simple and robust with short payback time