Ship Propulsion System Lecture 3Dr: Aly Hassan Elbatran

Steam Power plant with Nuclear Reactor

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A steam plant may also be powered by a nuclear reactor instead of oil-fired boiler. In merchant shipping

nuclear options are not commercially feasible, however, some icebreakers working in the frozen waters

in northern Russia have been designed with nuclear power plants. For submarines the main military

advantage is that the nuclear reactor does not need air as does a boiler or a combustion engine, sothey can stay below sea level for months.

Steam Power plant with Nuclear Reactor

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In a nuclear installation the reactor adds

heat to the primary water circuit. The

primary circuit is radioactive. The

water/steam system as found in

conventional steam turbine plants is

found here as the secondary water

circuit. The secondary circuit obtains

heat from the primary circuit in a heat

exchanger. Temperatures in the

secondary system are lower than those

in a conventional steam system, so the

thermodynamic efficiency of this system

is even lower.

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Gas Turbine Power Plant

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When compared to the diesel engine, the gas turbine has

- a high power density,

- light compact piece of machinery. This major advantage for vessels where space and weight are precious,

has to be weighed against the following disadvantages:

- It has a low efficiency and high fuel consumption

- It needs higher quality fuel than diesel engines (recent developments have started to solve this issue)

- It is more difficult to repair in situ because it has been designed for repair by replacements

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Combined Power plant

Sometimes due to the ship functions a single prime mover may not be suitable for the ship services, and the

combined plant may be a preferred choice. In combined plants, two or more prime movers are usually

connected to the propulsor through a common transmission system to take advantage of the desirable features

of each prime mover. Many combined plants configurations have been in use in several applications, e.g.

CODAG, CODOG, COGAS, CODLAG, etc.

CODAG CODOG

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Combined Power plant

Combined Gas And Steam (COGAS)

This system is suggested to be used

as an upgrade for ships powered by

gas turbines, the steam is generated

by using the heat in the exhaust of the

gas turbine thus recovering some of

the lost heat. This recovered heat can

provide the plant by up to 25% of its

total power with overall efficiency up

to 55%.

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Combined Power plant

Combined Diesel electric And Gas (CODLAG)

This system is considered a hybrid system

since it consists of both mechanical and

electrical drives. Mechanical propulsion

power is developed by two gas turbines,

each through a gearbox connected to FPP.

Additionally electric motors, fed by diesel

gensets, are delivering propulsion power.

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Machinery ArrangementThe arrangement of machinery in machinery spaces is strongly affected by the selection and specification of

the machinery and by the overall ship design.

For a small cargo vessel, machinery spaces include:

- Main machinery space (propulsion engine, gearbox,

transmission, gensets, auxiliaries)

- Steering gear room

- Workshop

- Control room (usually contains also the main switchboard)

For a cruise vessel or a naval vessel, machinery plant is more extensive:

- One or two propulsion engine rooms

- One or two diesel generator rooms

- One or two main switchboard rooms

- One or two chiller rooms

- Separate room for separators

- Pump rooms for FiFi (Fire Fighting) equipment

- Machinery control room

- Workshops

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Machinery arrangement

Location of machinery spaces

- The location of machinery spaces also depends strongly on the complexity and the extent of the plant and

the overall ship design.

- For a simple machinery plant of a small cargo vessel or a large tanker the main machinery space is

usually located in the aftermost hull compartment. The transmission system then is short and compact,

auxiliary systems are also compact and the machinery does not interfere with cargo spaces.

- The shape of the aftship, and consequently the width available for the m/c (machinery) space may not be

suitable for multiple engine or configurations. Multiple engine configurations with mechanical transmission

require that the m/c space is low and wider than the aftermost compartment.

- the engine room is usually located at 1/3 or ½ the ship’s length from aft. In case of electrical transmission

only the electric motors need to be close to the propulsors. Gensets may be located at any convenient

place in the ship; sometimes low in the ship to avoid noise and sometimes high enabling access for

maintenance and replacement.

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Transmission System

The transmission system is located between the prime mover and the propulsor. Its main function is to convert

or transmit mechanical energy. The transmission system transmits

- The torque generated by the prime mover to the propulsor,

- The thrust generated by the propulsor to the hull.