Diesel Electric Propulsion
Diesel Electric Propulsion
- Download (JPG - 826 Ko)
Operating principles
This type of propulsion aims to reduce the fuel consumption of ships working under different duty ranges.
The idea is to optimise the overall efficiency of the propulsion to use up less energy and yet achieve the same result, and thus to reduce pollution.
Electric energy is usually produced by four diesel generator sets that are sized to meet the ship's power requirement.
As a rule, the higher the power requirements, or the more additional or alternative drives are required with respect to the main propulsion, the greater the interest of this solution.
Main advantages
Fuel consumption is proportional to the actual power requirement of the ship. The safety factor is increased, since these ships are provided with 4 diesel engines, instead of one.
If two electric motors are used for one propulsion output, safety is multiplied by 2 with respect to one single engine.
The generator sets are running at constant speed, and at their nominal speed. This will improve efficiency.
Maintenance of the power plant is facilitated.
Principles of operation of controllable pitch propeller systems driven by two electric motors
This propulsion arrangement is designed to reduce fuel consumption of ships working at different operating speeds.
The idea is to optimise the speed and pitch of the propeller, especially at low ship speed. The electric energy is usually supplied by four identical generator sets chosen as a function of the propulsion power requirement, and the power necessary to drive the on-board electric loads.
A power management system (PMS) allows to adapt the number of gen-sets in operation to the actual needs.
As a rule, the higher the on-board power requirements, or the more additional or alternative drives are required with respect to the main propulsion, the greater the advantage of this solution.
- External link Shipyard
3 modes of propulsion
Eco mode
One main electric motor running at variable speed, and with variable pitch, to optimise propeller efficiency.
Maximum speed mode
2 electric motors in operation, functioning at constant speed; ship speed is adjusted through changes of the propeller pitch.
Come-home mode
Only the electric booster motor is in operation, running at constant speed. The ship's cruising speed is adjusted through changes of the propeller pitch.
A few technical data
This ship has 4 diesel generator sets rating 500 kW each, to satisfy the overall power needs (on-board equipment, propulsion, freezer, winches), i.e. a total power of 2000 kW. The gen-sets are triggered as power is required.
The propulsion system takes up 700 kW to 1400 kW. The transmission, a MM W 20000 (ratio 6.179:1) has 2 input shafts, each of which is connected to one of the two 700 kW electric motors, one of which being a variable speed motor.
The main propulsion is transmitted through a MM Controllable Pitch Propeller of the S780 type with 2800 mm diameter.
The whole unit has BV certification, Ice class 1C.
Data sheet to download
