The most important input when considering the optimum propulsive solution is the time distribution of operating conditions of the ship and its machinery.
Increased focus on “green shipping” demands a more comprehensive focus on details in finding the right propulsion solution.
This is not new to Brunvoll, we have for decades tailored propulsion configurations to the actual vessels' operating profile to achieve optimum efficiency.
The most important input when considering the optimum propulsive solution is the time distribution between the different operating conditions of the ship and its machinery.
When this is established in cooperation with the customers, power requirements and associated fuel consumption/emission can be predicted, and one propulsion/machinery solution can be compared against another.
An extensive search for the best solution which offers the ultimate propulsive efficiency is aimed for. At the same time, the cost of choosing the optimum solution is equally important and the overall optimum will then be the solution which is the best tradeoff between all the conflicting requirements.
A wide product range, combined with experience and competence give Brunvoll a leading position as a Propulsion System supplier.
Extensive range of configurations varying from the simple to the complex within hybrid, electrical and conventional propulsion systems, give Brunvoll a perfect base in search for the optimum system for the operating profile.
By being involved in the newbuilding or retrofit project at an early stage, Brunvoll contributes with valuable input to owners and designers in search for the ultimate propulsive efficiency. This valuable interaction also goes the other way that requirements from customers and designers lead to innovative solutions for the ship type and segment.
Feathering is an option on CP-propellers.
A feathering propeller has the blade angle adjusted in line with the water flow.
For vessels working in different conditions with a wide variation in thrust demand and sometimes with restrictions in allowable rpm range, the Controllable Pitch Propeller often turn out to be the preferred solution.
A CP-Propeller is an efficient propeller type, that by its stepless pitch match motor characteristics and different operating conditions. An ideal setup is to include one or more optimum pitch/rpm combinators, tailor-made for the actual operating mode.
Often quite extensive setup/configurations may be calculated and ranked against each other based on the overall fuel consumption basis.
This focus may consider selection of gear steps which determine optimum propeller speeds and associated diameter but also more advanced gears, for instance two step gears and gears which may be combined with variable rpm driven electric motors in combinations with traditional motors (hybrid approach)
The operational profile will also be important when preference on open or ducted propeller is sought. The time difference at low or moderate ship speeds and corresponding thrust demands will be important parameters to find the optimum propeller solution.
CP-propellers in single- or twin-screw with reduction gearbox, PTO/PTI, main engines, generators and electric motors offers numerous options for the efficient propulsion system.
Whether or not there is a gearbox included, a CP-propeller and electric motor can be optimally adapted to the actual operating condition. Variable rpm at the electric motor and adjustable pitch propeller give the necessary flexibility to ensure optimised working conditions for the propeller.
A 2-stroke slow speed engine is an effective engine for vessels which have large power demands, and the CP-propeller will add the necessary flexibility and compensate for varying running conditions.
For vessels which works mainly in one condition with very small variation in thrust demand, the fixed pitch propeller may turn out to be a preferred solution, which will be both cost effective and a reliable solution.
One of the important assets with the azimuth thruster as a propulsion device is that it offers excellent flexibility since it can operate with high degree of performance in both propulsion and manoeuvring.
For vessels where those two considerations are important, the azimuth may be the most attractive solution. Due to the fact that thrusters can move the vector thrust at an artificial angle with 360 degrees, sometimes one can eliminate/reduce number of tunnel thrusters in area where the azimuth is located.
Push ducted propellers, built for heavy duty operations, designed with emphasis on maximum bollard pull and focus on hydrodynamic- and total energy efficiency and excellent manoeuvrability.
Pull open propellers, designed as a highly efficient pulling thruster with good manoeuvrability, course stability and low resistance. The excellent wake due to the propeller in front of the gear housing give room for designing better and more optimum blade designs for efficiency and low hydroacoustic noise emittance.
The CRP - Contra Rotating Propeller is one example of an energy saving device, where is found that in many cases this solution will offer attractive improvement on the propulsive efficiency. Typical gains with CRP compared to traditional single step propellers are within the range 5-10%, but can even exceed that in some special cases.
For ducted propellers, the profile shape of the nozzle and the size of the nozzle may be subject to a closer examination in search for efficiency improvement. The profile shape of nozzle and the size of nozzle will be considered in each special case.
Other examples are for instance ICP (Integrated Costa Propulsion) where the swirl in the propeller slip stream due to the blunt termination of the propeller hub, is partly recovered by a smooth transition between the hub and the rudder.
Sales Manager Retrofit, Brunvoll Volda AS
