Marine propulsion, alternative propulsive devices.ppt

Marine propulsion, alternative
propulsive devices
A comparative analysis of the
latest developments

Shipping statistics
 Over 90% of world trade is carried by the
international Shipping Industry. Without shipping
the import and Export of goods on a scale
necessary for the modern world would not be
possible.
 Seaborne trade continues to expand, bringing
benefits for consumers across the world through
low and decreasing freight costs. Thanks to
growing efficiency of shipping as a mode of
transport and increased economic liberalisation, the
prospects for the industry further growth continue
to be strong.
 There are around 50,000 merchant ships trading
internationally, transporting every. Kind of cargo. At
1st January 2006, the world trading fleet was made
up of 48,681 ships with a combined tonnage of
647,075,000 gross tonnes.
 General Cargo Ships 18,316
 Bulk Carriers 6,471
 Container Ships 3,524
 Tankers 11,786
 Passenger Ships 5,790
 Others / Special of ships 1,794
 Total 47,681

Propulsion system design
 Propulsion is the term used to describe mechanical means of
enabling floating vessel such as ship or boat to propel itself
through water. For any self propelled vessel the following
functions are essential:
 A propulsion system, which provides the necessary thrust to give
the vessel in, question a specified speed and in some cases the
static thrusts are of importance. The normal solution is a
conventional marine propeller with shaft-line, stern tube with
seals, line shuffling bearings, reduction gear in case medium.
Speed engines and, of course, the propulsion engine itself.
Remote control of machinery from the wheel house is now a days
provided.
 A steering system which control of the ships direction and course
keeping at speeds at which the redder is effective. The standard
solution is a rudder to deflect the water off of the propeller, with a
rudder post and bearings and a steering machine with auxiliaries.
Rudder control from the wheelhouse is by remote control of
steering gear from a wheel or lever. An interface to an autopilot
system is normally provided.
 A maneuvering system for safe and rapid ship control in confined
waters where speed and direction control of the propeller in
combination with rudder movement is still inadequate. To achieve
better results it is normal to fit transverse thruster at the bow and
in some cases also at the stream. Such a side thruster is
normally in a tunnel, with a suitable drive system, and remote
controls from the wheel house.
 The primary factors which influence the choice of engine can
be summarized as follows:-
 The ability to burn the heaviest and cheapest of fuel without
detrimental effect on engine components. and maintenance
costs.
 Maintenance work requiring periodic attention, workload for
the crew to be carried, cost and availability of spare parts.
 Suitability of the plant, to be operated unattended for long
period, thus saving on manpower through elimination of
watch-keeping.
 Propulsive efficiency of the plant, i.e. the ability to turn the
shaft with low enough speed to drive the largest diameter
and hence the most efficient propeller.
 The size and the weight of the propelling machinery as this
can be affect the revenue earning capacity of the vessel.
 The purchase and installation costs of the whole machinery
plant.
 The reputation of particular engine type for reliability and
operation without attention.
 The selection of main engine and its ancillary machinery are
decision of major importance but of equal importance are the
methods used to drive the propeller and indeed the type of
propeller used, as these can considerably alter the economic
operation profile of the vessel. Current practice is to design
the whole machinery installation to suit the vessels’ planned
operational programme.

Criterion for propulsion
consideration
 ANALYSIS OF SOME
COMMON PROPULSION
INSTALLATIONS: - Ship
propulsion normally occurs
with the help of a propeller,
while the primary source of
propeller power is the diesel
engine. Therefor in order to
arrived a solution that is as
optional as possible a thought
analysis has to be made of
the four major elements :-
 (a) Hull,
 (b) propulsion,
 (c) Prime mover &
 (d) interaction effects

Various machinery arrangement
 Various Machinery installations :- There are a wide a variety of
machinery installation used in ship building practice throughout the
world, each with their own specific areas of application with their
respective advantage and disadvantages :-
 Single screw single Engine installation.
 Multiple Engine single screw installation.
 Multiple screw installation.
 Plants with mixed machinery.
 Electric propulsion.
 Nuclear Propulsion. And
 Magneto Hydrodynamic propulsion.
 Cosag :- In earlier steam propelled ships, bore cruise and boost
turbines were geared to …. Propeller to meet top speed and normal
arising power levels. With the advent of aero-type gas turbines. Which in
marinades version because available for marine propulsion, the use of
this gas turbine to replace boost steam turbine because popular. The
advantage of Combined Steam And Gas plant is that the vessel can be
made ready for sea. Very quickly whilst the steam can be raised when
the vessel is under way. Acceleration characteristic of gas turbine are
excellent, besides very high power output can be obtained from compact
power unit.
 Codog :- The combined Diesel or Gas plant simply uses the diesel
engine for cruise mode, for boost mode, however, a much more
powerful gas turbine can be put in use. With this system only gas turbine
or the diesel engine can be used at one time.
 Codag :- The Combined, Diesel And Gas system differs from the above
in that the gearing and control systems are designed. Such that the gas
turbines and diesels can be operated together with. Suitable load
sharing systems in operation.
 Codlag :- This system still uses a gas turbine for maximum speed of
operation but has an electric motor incorporated into the propeller shaft
line to give slow speed on motor drive alone. The power for this
propulsion motor is obtained from the ship auxiliary generators. And the
result is a considerable reduction in weight and space occupied by the
machinery. A particular advantage of this system is the silent running
feature of the plant at slow speed, as the reduction gearing and gas
turbines are stopped when on motor alone and the diesel generator sets
are mounted on heavily noise insulated containers. For this system it is
normal for the motor to be electrically excited at all times so at full power
will still contribute to propulsion vessel.
 Codal :- This system used high speed diesel engines also the primary
propulsion systems. But also coupled to each main reduction gear is an
electric propulsion motor. Again the power from the propulsion motor is
obtained from auxiliary generator sets by use of diesel engines a wide
range of speed and powers is obtainable from the plant at lowest
specific fuel consumption rates.

ELECTRIC PROPULSION
 The diesel electrical propulsion provides a number of well known advantages
be flexibility in operation, distribution of propulsion and hotel loads, power
station concept; flexibility in arrangement of the man components such as
gensets, converters, switch gears and propulsion motor. Notwithstanding that
8-10% loss in efficiency through power conversion, and the higher cost of
installation in machinery and control system, the electric dries is becoming
more popular because of the following advantages :-
 These is considerable in crease in reliability because there are several prime
movers instead of just one.
 Maintenance is sassier because the Main Engine are smaller in order to avoid
large electrical machines and plant is of lower weight and there is much more
interchangeability of spare parts.
 One or more engines can be shut down at see and Service. Speed of the ship
can be varied from number of generator connected to circuit. This is of
importance to a ferry operating to a timetable and any less of speed can be
made up by more prime mourners.
 Conversely, where the slips in running light the engines camber more
efficiently loaded by using ferule engines to match the reduced propulsion
requirement.
 It is only necessary to employ engines of one bore and stroke size
throughout the sleep and these in option of using main generator for
auxiliary power supplies.
 The Engines can be located at any convenient position on the ship while the
propulsion motor can be right aft eliminating long propeller shafting.
 Control of propellers shaft speed and direction from the pride is Simplified
with clinical controls compared with electric mechanical diesel populism
engines.
 Part form around fives are much quicker as maintenance work can be carried
out at sea.
 The weight of the machinery is reduced as is fell bead room required for
engine room.
 These is much flexibility conversing power distribution between propellers
and power requirement can be matched to suit the vessels operating profile.
 The major disadvantage of the electric system in the light fuel consumption
resulting from the loss of transmission efficiency and higher initial cost of the
machinery. Never tactless, there is the benefit that engines used not be
operated at part load, which is detrimental to their performance, leading to
savings in maintenance costs.
 A central electric power station for propulsion and ship service has the
following characteristics :-
 A power plant based on number of diesel or gas or steam troubles driven
gensets rated to deliver all power required for propulsion and ship services.
The number of generators connected to the distribution network can be
varied according to power demand.
 A distribution system often divided into medium voltage and low voltage
network. The medium voltage supplies the high power consumer, such as
main propulsion drive, through drive and air conditioning compressors. The
bow voltage section supplies the rest of the slips electric consumers.
 A variable spaced AC drive system comprising a propulsion motor and a
frequency connector. The motor speed is contraband by control which alter
the input frequency to the motors.
 Redundancy in power generation plant and propulsion drives the system to
continue to supply power to propeller even in the event of multiple failures.
 Lower operating costs achieved from saving in fuel and maintenance cost by
reining the minimum member of diesel generator sets at there optimum
loads.
 Enhanced availability reliability and maintainability are archived by operating
the inherently robust plants most efficiently and permitting pennant
maintenance work to be cared out dung the voyage.

SYNCHRO CONVERTERS
 Synchro – Converters : The synchnoconverter is a DC link converter having two three phase bridges, one supplying
controlled DC current to the link, which has a smoothing inductor, and then to the output bridge voltage operates in the
inverting made supplying ac power to the connected motor. Because the output bridge requires to be supplied with KVAr
from its ac load the motor has to be a synchronous machine operating in the our excited or leading power factor made. The
D.C. current input to the link by the supply converters switched in such a way so to produce or rotating field in the stator of
the machine. Each suitable operation of the machine advances the rotating field 60 deg the instance at which the switching
operation takes place is determined by the shaft encoder or motor voltage detracts, the control being so arranged the stator
and motor field axis maintain a close angular relation sleep and motor cannot fall out of step.
 For reversing opeartion the drive is reversed by phase the machine converter into reification
so that motor supplies power to the link and then to the supply by supply converter which will
operating in the immerging mode. When the motor reasues stand strill normal motoring
operation is resumed but whiter reverse switching sequence at the machine converter so that
the motor moves in reverse direction. This is a rare example of regenerative breaking by
converters.
 Because the converters are line commutted the switching sequence described requires the
motor to be operating at above approximately 10% speed to ensure that there is adequate ac
voltage to effect the commutation. At speeds, below 10% or so the supply converter
transiently forces the d.c. link current to zero so that the machine converters can be switched
over to an off state.
 The synchroconverter is able to provide output frequencies of upto 100 Hz, without incurring
any particular design penalties, and at the same time is equally satisfactory at frequencies
below 50 to 60 Hz and is suited for low frequencies desirable in slip propulsion.
 There are forque fluctuations/pulsations because the motor rotating field advances in 60
steps, the frequency of pulsation’s being dependant on the number of machine poles and
running speed. A torsional analysis of the shaft system should be all integral feature of
average drive design procedure in order to avoid critical torsinal vibration problems.

CYCLOCONVERTER
– Cycloconverter : A Cycloconverter is restricted to much lower frequencies less than one thrall of AC supply frequency
whit is associated with the way, in which a cycloconuirter operates.
 A conventional these phase converter with a de output can be controlled so that mean output
voltage is increased from zero to a maximize and then to zero without following a half sine
wave. Two such converters connected back to back can produce a two frequency ac output. The
output has a noticeable ripple content which increaceswith frequency thereby limiting the
maximum acceptable output frequency.
 Input isolation can be provided by transformer and these also have other benefits for high
power drivers.
 A cycloconverter is a direct, line commuted converter, without a d. c. link, with ac supply
providing the commutating voltages, the same can be used with either synchronous or induction
motor to optimise motor designs, these motor are capable of high dynamic performance and
this is especially true when vector control is used.
 The cycloconverters have the following disadvantages :
 The quality of cycloconverter output waveform diteriorates as the output frequency increase or
as ratio of output to input frequency inverse. The increasing harmonic content in the motor
supply waveform effects the motor torque and supply system of the changing harmonic content
of the converter input current.
 The effect of the change over delay which must be allowed between the conduction periods of
the two pridges limits max frequency thes delay leing necessary to ensure that the outgoing
bridge is definitely off before incomming bridge is switched into conduction.
 The phase control or fining delays, of the individual converters is continuosly changing and since
the power factor of a converter is related to the firing delay there is a variation in the power
factor of a three phase cycloconverter which is related to output frequency.
 The harmonic current which flow in the supply system and the motor are determined by the
Pulse number of the converter and the output frequency so that the harmonic currents are not
of constant frequency.

PULSE WIDTH MODULATED
CONVERTER
• Pulse which Modulated Converters : The pulse WIDTH modulated (PWM) converters that
are used to provide variable frequency supply for motor applications are of the dc link force
commutated type. Converters of this type can have intermediate d.c. link supplied from a
input commutator that acts as either a voltage or current source to the link. The most
common arrangement for a PWM converter is a voltage source link with simple uncontrolled
bridge rectifier at the input. The dc voltage is therefore fixed and related directly to the a.c.
supply voltage.
 The output inverter of a PWM converter can have thyristors or GTO
thyristor as its switching elements. Current designs in general use
transistor for lower powers while GTO thysistors are used for higher
power equipment’s.
 The PWM converter is favoured because by use of suitable switching
strategies, it is possible to obtain an output waveform is which the
selected harmonies have been eliminated or reduced. One the plus
switching or due carrier frequency is limited by the switching losses in the
transistors or thyristors and although small converters may use KH
frequencies which is not practicable at high power. Some PWM operates
by what is referred to as gear changes, with carrier frequencies
undergoing step changes in frequencies at particular values of the output
frequency. In althorn the steps the carrier increases in frequency as. The
output frequency increase. .

Nuclear propulsion
• Despite the political and other factors thwarting the significant use of
nuclear power in ships, the some key disadvantages and some minor
disadvantages. The major advantages are:-
• Long periods between refuelling operations and considerable
endurance range for vessel after each refuelling. [capabilities like dry-
dock to dry-dock refuelling operation is easily possible].
• Huge quantities of fuel need not be transported with resultant weight
savings and space needed for fuel, Besides a reduction in manpower
required for refuelling operation.
• As nuclear power in not dependent on air for combustion, it is very
useful choice for sub marine propulsion. For surface ship there is not
exhaust to give the ship a neat Signature and no pollution to
atmosphere by exhaust emissions.
• There are no changes in ship draft and trim as the fuel is consumed.
• Nuclear plant is very simple to control, it responds Instantly to load
demand changes and can supply quantities of high-pressure steam.
• Technology such nuclear gas turbine can cause to increase the
Dynamic advantages combining those of nuclear power plant and Gas
turbine and getting steam out of the equation.

Challenges for nuclear
propulsion
• Despite the several afore mentioned advantages there as shell same challenges.
Which have to be addressed to make nuclear plant. more attractive to merchant
ships.
• The high cost of purchase and operation is a major deterent to commercial
operator who will be concerned with profitable operation and return on
investment. Since the full life operation of nuclear vessel under commercial
trading condition is nonexistent full life operation cost estimation against me
present diesels engine installation count the confirmed out is expected to diesel
engine installation cant be confirmed but is expected to be much lower.
• The cost of building and maintaining a nuclear plant are very high because of very
stringent quality control necessary to ensure reliability and extremely important,
the safety of the plant and the ship or crew.
• Reactor plants are many and require very dense shielding to contain radiation the
power is to weight ratio of the nuclear plants is only of advantage in large vessel.
• The training of crews competent enough to operate nuclear plants is both true
consuming and expensive has shown that there is great difficulty in attracting
suitable qualified scientist to serve aboard ship. Training for nuclear plant
operation is best under take in a military environment.
• A nuclear reactor installed a ship would in value some design problem as
hall,pitch, shock which have learn already learn meet by many design,put due to
string at requirement for shock and flexibility control the naval reactors are
unnecessary by expensive there is need to develop a commercial reactor
specifically for merchant ship propulsion.
• Most these reactors are of pressurized water type design that is which the steam
generated was initially of relatively low temperature requiring redesigning of
turbines.

Ships suitable for nuclear propulsion
• The ship with the following, characteristics would slow greatest economic advantage in
convention with commercial source of propulsion.
• (a)long trade route,
• (b)Quick turn around in ports
• (c)Large dead weight capacity.
• (d)minimum shaft power of 20,000.
• (e)Both side navigate fully-loaded.
• (f)Regular home or base port.
• (g) Cargo suitable for nuclear shielding.
• During present day with new technological advancements the requirement (e),(f)n be more
relaxed. These characteristics suggested the choice of ship operating at a relatively ship speed and
over a long trading route, such a tanker,are carrier or container carrier. Dry cargo freighter with
also post town and limited. Cargo is particularly unsuitable from commercial point of views. The
system is also suitable for vessel which could accommodate the heavy machinery and the same
five require very high machinery output. Ice breaking ships are the best examples,the breakers to
operate in for northern latitudes and possibly. Cargo gas on tankers to transport fuel. Reserves
from arctic region for general shipping most likely application is very large and fast containers and
huge submarine tankers.

Reactor types
• Reactor:- The most important port of the nuclear plant is the reaction,with fusion technology still in its infancy the reactors are essentially of
fission type which can essentially be divided into two type:-
• (a) FAST BREEDER REACTOR:- These reactors use plutonium as fuel. Plutonium undergoes fission which a high a large speed neutrons
strike it these reactors don't require any moderator other elements of this reactors are similar to thermonuclear reactors Fast reactors although not
in much use at the present are gaining importance as try have many advantages over thermal reactors.
• Fast reactors use plutonium which is produce artificially when U-238 atom absorbs a neutron this can be achieved by surrounding the core with a
blankets of U-238 which is gradually converted to plutonium by bombardments with neutrons escaping from the core.
• The uranium found in the earths crust is 99.3% U-238 and 0.7%U-235. Hence fast reactors enhanced the life of the fuel. For the same power
output the fuel required would be less and hence the fast breeder reactors are much smaller in size than thermonuclear reactor since the size of the
reactors is smaller for efficient that transfer metal coolant such as sodium is used.
• (b) THERMONUCLEAR REACTOR:-This uses U-235 as fuel. The neutrons are liberated from the fission neutron. But the U-235;doe sent
under go fission until a slow speed neutron strikes it. So neutrons liberated from the fission has to slowed by passing through some materials,called
MODERATOR,before try strikes the U-235 atom. These slow neutrons are called thermal neutrons and the reactor concerned Thermal reactors
or thermonuclear reactor. Depending upon the coolant, moderator,cladding used the rector can be further classified.
• The most common nuclear reactor a used in machine propulsion is pressurized water reactor. The reactor is fulled by UO2 uranium dioxide pellets
with enriched to 4.4%encased in hollow stainless steel cylinders closed at both ends. The fuel contain B10 of born as a “burnable poison”
introduced deliberately to reduce reactivity of the reactor core at the start of life. The fuel are held between two plates, secured by a control rod of
Zircoloy. The control roads of Boron carbides in the steel are placed in reactor core. In cruciform cross section these control rods can be moved in
or out of the core is space between the fuel element in the event of an emergency there is a spring drive action for inserting the rods into the core.
Thermal shields protect the pressure vessel walls from the heating effects of direct radiation from the core the pressure vessels wall in protected
from direct radiation and the resulting our heating by a series of thermal shields around the core barrel these thermal shields build to reduce the
radiation level outside the reactor and are supplement by a primary shield tank the entire reactor assembly is enclosed in an isolable steel
containment vessel the containment vessel protects the ship and her crew against the most serious conceivable reactor accident and also shields
working area from radiation while the reactor is working the main shielding is done by a secondary shield of a lead face tank around the reactor
pressure vessel which is enclosed within concrete wall 2'(fleet) thick. This tank provides a layers of water 33”thick to absorb neutrons while the
lead surface attenuates the γ(gamma) radiation. A secondary shields in formed by lead, polythene and concrete around the containment used the
shielding has been designed to reduced the radiation level in the living areas of the ship to less than 0.5 rems a year, while in actual practice the
actual exposure among the crew has in fact has been under 0.2 rems a yea

Reactor design safety features
 REACTOR DESIGN SAFETY FEATURES:- Particular points especially emphasized in design and the commercial safety are:-
 1) No one in the control area shall be exposed to radiation exceeding hall the allowable limit the radiation shields are designed for the following conditions less than
0.5 rem/yr in the non controlled area, less than 5 rems/ year in controlled area, where any one can enter, except for inspection for a limited time. The reutilization
system is divided into two sections, one for areas where radioactive.

 Contamination may occur and another for areas where it never occurs inside the reactor container, the reactor room and reactor auxiliary rooms, the atmosphere is
kept slight lower to avoid spread of inside air

 2) Any hazard due to either mishandling by an operator or malfunction of control system shall be kept to a minimum instruments monitor. The condition of the
reactor and its associated plant if these indicate a potentially dangerous situations or if all control electrical supplies, fail, the rod-drive motors de-energies and the
reactor shuts down automatically.

 3) The diffusion of radioactively shall be prevented by installing the reactor vessel and accessory instrumentation in a steel container, which also protests the
reactor plants against free flooding. At the bottom of container two sets of pressure balancing valve are provided to present the rupture of the container by external
pressure in the event of sinking. The valves open at pressure difference of 2 kg/cm2 so sea water can flow into the container and will close again after the
divination of pressure difference.

 4) The steel container should always be safe against such as collision or stranding being located in the center of the well and protected on all sides with reinforced
structure. Three reactor itself, the reactor auxiliary equipment and the reactor service area forward of the machinery space are auxiliary rooms are equipped with
anti-collision structure of uniform strength around the front and back of reactor. Both sides of these rooms re equipped with anti collision structure, which consists of
six decks of thicker plates. In event of collision, the energy will be absorbed by this structure, thus not damaging the container and the installations in the reactor
and it’s a built up lattice composed of stranding, this structure will protect the inner bottom plate against breakages and two protect the reactor container and other
installation.

 5) The two – compartment standard and strict stability criteria will be applied to prevent an eventual foundering

 6) Fireproof constructions, fire detecting system and fore extinguishing systems are to be sufficiently installed throughout the ship, non-combustible materials are to
be used for furnishing.

 7) Dust type installations and the principal of dispersal are adopted to ensure the security of functioning of all equipment. For safe and smooth operation, it is
important that all the important parts in the primary circuit duplicated so that if one of them fail other can take over the charge.

 8) Emergency devices and the safety systems associated with reactor plant shall operate satisfactorily when subjected to the following:-
 Roll 600 – single amplitude
 Pitch 200 – single amplitude
 List 600 – Trim – 200
 Vertical acceleration: 1+1.3g, other ascertain – 1.0 g

Characteristics of MHD propulsion
The propulsion system are composed of superconducting magnets,
persistent current switches between refrigeration units, sea water
pipes electrodes etc. and each onset of these systems is arranged
on the post and starboard sides of the ship respectively. The
superconducting magnet are of a six linked ring construction with
six saddle type superconducting coils being arranged on a
concentric circle in a helium vessel. The leakage of the magnetic
field around magnets are made small as much as leakage of the
magnetic field around. Magnets are made small as much as
possible by mutually combining the magnetic fluxes of each coil.
The sea water pipes are blow passages of sea water through the
bull are subjected to sea water pressure and electromagnetic force.
Furthermore, the sea water pipes are required to be with a good
insulating character against electricity in order to held the
electrodes and busbars for sending electric current for these
reason, the sea water are inside of epoxy resin GPRP Titanium-
nobium alloy is used as the base metal of the electrodes with the
anode of DSA and the cathode plated with platinum. The length of
the electrode is 3.4m.

Alternative propeller design
In the following sections we will analyze the new and radical
propeller designs, their application and their relative
advantages. The most noteworthy inventions and
developments are:-
(i)RIM DRIVE THRUSTER
(ii)BULB HUB CAP TWISTED RUDDER
(iii)PRE-SWRIL STATOR
(iv)FEATHERING C.P.P.
(v) CONTRA-ROTATAING PROPELLER RUDDER
(vi)NAKASHIMA NON-HUB VORTEX (NHV) PROPELLERS
& PROPELLER BOSS CAP FINS (PBCF)
(vii)AZUPOD PROPULSION OR AZIMUTHING POD
DRIVES

Rimdrive thruster
 The advantages cited for the RDT system
over the conventional system are :-
 Increased ship design arrangement
flexibility , due to the compact nature of the
integral thruster motor.
 The blades are simpler and easier to fit
and exchange, easing maintenance task .
 The RDT's are lighter in weight and
compact due to integral motor design.
 Increased scope of speed selection
through the use of PM's
 Improved Hydrodynamic efficiency and
high thrust efficiency.
 Very low noise level {suitable for stealth}.
 Due to the specific nature of the bearings
obviating the need for lubricating oil and
dynamic seals which promises to reduce
maintenance and reduce oil pollution risk.

Bulb cap twisted rudder
 BULB HUB CAP TWISTED RUDDER – Studies by Rolls–Royce interest interaction between bull, propeller
and ruder have led to a development of a system herein some of the swirl energy in the flow from the propeller
is concerted to forwarded thrust. The device combines a tapered and cap and a rubber bulb, using a spade
rudder incorporated a twisted leading edge profile. The increased propulsive effectiveness which caused
significant fuel consumption reduction. The improvement in the efficiency should be in the 3-6% region, giving a
pay back time of one to two years, the tapered bulbcap fitted to be propeller leads to water flow on to a bulb
which forms a part of the spade rudder. Throught the twisting of the rudders’s forward edge, the burled
components of the propeller slipstream in effectively harnessed to give extra forward propulsion thrust.
 Although the bulb solution are not new, the difference with the rolls –Royce concept in the functions integration
fo propeller, bulb and rudder elements. The design functions efficiently not only at rudder straight ahead but
also at rudder angles of one to four degrees, typically entailed in making normal course corrections and when
rudder is fact handover during low speed manufacturing. The presence of hub – cap and rudder bult rumove
the risk of hub vortex cavitation. As a consequence, the hydrodynamic loads can be modified by increasing the
loading towards the hub and reducing the loading at the tips, the intensity of the blade pressure pulses can be
lessened reducing propeller induced noise and vibration.

 When designing larger propulsion system it is essential to consider the propeller and rudder together as the
eventual propulsion system will have significant influence on the performance of the rudder. The rudder
operates in a combination of helicoidal flow produced by the propeller and the ship layer boundary the
incidental flow to the rudder has strong rotational component. Also, the rudder tuds to distorts the flow field so
that the ship stream generated by the propeller fitted to large container ship suffer from cavitations erosion on
integrated approach giving due consideration to rudder design is warranted.

Pre-swirl stator
• PRE-SWIRL STATOR: This concept was jointly
developed by Dawoo ship building and marine engineering
(DSME) and SSPA switch. It use a stator, typical of four
blades of diameter equal to that of the propeller in a stator
on the hull bassing immediately forward of the propeller
so as to alter the water flow to the propeller disc in order
to improve hydrodynamic efficiency. Although the stator
does not itself save energy or create a forward force and in
fact adds to resistance, it increases and altered interaction
with the blades that improves propulsive efficiency and
result in reduced power requirements. A consistent and
durage gain of 4% on propulsion power was achieved at
design through with optimized stator angles.
•
• Careful running of the blade angles achieves beneficial
interaction between the propeller blades and the flow
direction, besides increasing propulsion efficiency ;
improvements in propeller cavitations performance and
cavitation generated pressure pulse may also be achieved.
•
• The stator configuration and blade settings have to be
optimized to each bull form and not all level shapes will
benefit from preswire stator. The most promising sector at
present is that of full bodies songle screw ships such as
VLCC’s

Feathering C.P.P.
• FEATHERING CPP- A
featuring CPP has a least
40% excess pitch than
normal CPP in case a twin
screw ship has to operation a
single shaftice due either
engine failure or reduced
speed demand etc. employing
CP propeller design rather
than standard non feathering
units will reduce drag and
minimize fuel consumption.
Wartsilta happens to be the
largest supplier of feathering
CP propeller

CONTRA ROTATING
PROPELLER RUDDER
• A Japanese hybrid propulsion system designed to boost hydrodynamic efficiency and improve
ship mousse verabilitythrough optimized water flow and swirl energy recovery promises a total
energy savings of about 15%.
•
• The system consists of two propeller on the centre-line axis, a Conventionally mounted,
controllable pitch unit driven by diesel engine immediately abaft is a contra-rotating propeller built
into the rudder and independently powered by an electric motor.
•
• The contract rotating unit interrupts the vortex flow generated by the main propeller converting
the swore energy into extra thrust the direct conversion give the configuration an increase of
propulsion efficiency of 12% and depending on the precise manner and mode of operation using
main and auxiliary propulsion units in combination or separately further potential savings of 3%
are said to be attainable to give overall scope of gain around 15%.
•
• The electric motor driven assist propulsion can be turned up to 90 to part or starboard and used
in conjuction with the bow thereafter facilities the transverse movements and manuring berting
and unberthing. The ship can be navigated with either main or assist propulsion unit, a factor
which ensures back up in the event of main engine failure.

NAKASHIMA (NHV) PROPELLERS AND
PROPELLER BOSS CAP FINS:
The increase flow on the curved side
of the blade forces the stream
upwards to form a hub vortex with
PBCP the upwards flow of water is
blocked into straight ship stream by
the fins of the PBCF. The flow of water
over the fins causes the PBCF to
rotate in the same direction as the
propeller, reducing toque by 3.5%. The
ground effect of the blades caused by
fins boost thrust by 1.5%. The
illumination of hub vortex has several
addition benefits such as :-
a) Reduced stern vibration
(b) Reduced propeller noise
© Erases acoustic equipment noise
(d)fixes rudder erection problem
(e) it also fixes torque rich proble

PBCF ADVANTAGES
PBCF has proved its worth by constantly increasing sales
even during the lower oil price years. The PBCF benefits
verified from the data obtained from tests on 60 vessels
and the experience of 860 vessels are as follows:-
Performance enhancement, increase in propeller
efficiency by 5% torque reduction by 9.5% thrust
augmentation by 1.5%
PBCF is easily installed and can be replaced even at sea
saving shipyard fees. It is of the same materials as boss
cap and installed in the same way as the boss cap. No
additional maintenance is even required.
PBCF is useful in reduction propeller generated noise and
vibration, it reduce stern vibration propeller noise, acoustic
equipment noise
It can be effect in retrofitting for solving problems like
torque rich operation problem and rudder cavitation
erosion problems in large containers.
The PBCF can be easily be retrofitted enabling precise
measurement of the effect through speed trials or
manifation data on the same ship. They are effective even
with CPPs used with fact ferries, RO-Ro ship etc. but a
design review is required. It is approved by major
classification societies.

AZUPOID PROPULSION OR
AZIMUTHING POD DRIVE:
The azimuthing pod drive has been around for more than a decade and
recent years have been their growing use on a widening variety of
application. The development azimuthing pods has been market driven
action which is quiet rare in the field of marine propulsion research. The
potential benefits have proud very attractive to ship operators, who in turn
have demanded more and better from pod manufacturers. This forced
evolution has placed significant demands on the pod manufactures to
respond, authorities to legislate and crews on the pod driven ship to learn
low to best operate these new technologies. An azimuthing pod drive is an
integrated unit wholly replacing action of conventional propeller and rudder.
The pod unit is comprised of an electric motor ; situated outside the full of
the ship, encased in a water tight body and attached to the ship by a
pivoting strut. The electric motor power a horizontal shaft supporting the
propeller at on end or both ends ; or even two propellers fitted one end in
contra-rotating fashion. All powering and coolant requirement are passed
from the ship via the street and pinot joint, which can azimuth through 360.
The street acts a ruder with a flap for steering mechanism

Forces on azimuthing poded drives
Generally speaking the loads induced by the pods can be devided into three contributing components:-
a) Propeller generated ; (b) pod body generated and (c) those generated by gyroscopic moments.
a) Propeller generated load: It is clearly the trust generated load but a side force which is generated when the propeller is place at an
angle of attack to the flow while the side force in generally small compared to the thrust its lever about the showing arise can be used to
balance
other loads.
B) Pod body generated forces: This can be devided into lift force and draf force while the drag force is comparatively small compared to
trust, the lift force is typically 3.5 times larger than the trust. This lift force can also present a large moment about the showing ==
warranting careful attention about the position of centre of pressure in lift and the sluring stock axis –
C) Gyrocopfic moment: These are caused by the gyroscoping moments of the rotating propeller the shaft. A pod is force to the both by
helm control and/ or ship yarning motion, and with the motor spinning inside it, it will experience a pitching moment acting about the light
of the propeller shaft. This moment can be of significant magnitude and must be absorbed by the shaft bearing. The use of pods over
commontional propulsion arrangements can offer a 6-7% increase in propulsive efficiency depending upon geometry and other factors.
Much of this can be achieved by reductionin appendage drag due to the removal of conventional shafting and shaft brackets. A proportion
neavy also be attributed to improved a wave making performance due to favourable interaction between the pod and the stern section of
the levels as well as the reduced surface area, thus functional draf offered by the prammed stern form. The pod propeller can have higher
efficiency than its water posts properller in isolation due to the flow declaration for some pod configurations and propeller race rotational
energy gains for other pod configuration. The efficiency can by as high as 10% but some of its is cost due to trictional and from drag.

INTERACTION BETWEEN MAJOR
COMPONENTS OF A SHIP
SYSTEM:-
THE MAJOR COMPONENTS ARE;-
I. WAKE FIELD
II. HULL STRUCTURE
III. CHOICE OF PROPULSION
MACHINERY.

WAKE FIELD EFFECT
 CAUSED BY FRICTIONAL DRAFT OF THE HULL AND
PRESSURE FIELDCREATED BY THE WAVE MAKING
RESISTANCE AND IS MODIFIED BY PROPELER SUCTION
FIELD
 EFFECTS SUCTION FIELD OF PROPELLER.
 THE WAKE FILED HAS SEVERAL UNDESIRABLE
EFFECTS:-
a) THE PERIUODIC FORCES AND COUPLES ARE CREATED
AND TRANSMITTED THROUGH WATER AND SHAFT
BEARINGS OF THE SHIP CAUSING HULL VIBRATIONS.
b) THIS CAUSES A CHANGE IN ANGLE OF ATTACKCAUSING
THE ON SET OF CAVITATION
c) REQUIRES THE USE OF “WAKE ADAPTED SCREWS” FOR
BETTER EFFICIENCY, SINCE IT IS IMPOSSIBLE TO SUITE
INFLOW VELOCITIES AT ALL POINTS ON THE PROPELLER
DISC.
CAUSES DEDUCTION IN THRUST , +VE INTERFERNCE
CAUSES THRUST DEDUCTION AND –VE INTERFERNCE
CAUSES THRUST AUGMENT.

EFFECT OF HULL
STRUCTURE
 INFLUENCE OF THE SHAPE OF THE AFTER BODY
1. AT LOW PROPELLER REVOLUTIONS & CONTABT POWER THE
PROPULSIVE EFFICIENCY AND THE MAXIMUM SPEED OBTAINABLE
INCREASED AS THE CENTRE OF BOUYANCY IS MOVED FWD AND
AFTER BODY LINES WERE FINED; THE VALUE RECHED A PEAK AND
THEN GRADULLY DECREASED.
2. WITH INCREASE IN RPM, THE OPTIMUM POSITION OF THE CENTRE
OF BOUYNACY MOVES FWDAND THE AFT LINES MUST BE FINED.
3. Q.P.C. INCREASED WITH R.P.M. WITH RATE OF INCRFEAS DEPENDED
ON THE POSITION OF THE CB.
4. THRUST DEDUCTION FACTORVARIED WITH THE POSITION OF THE CB
BUT REAMINED CONTANBT W.R.T.RPM.
INFLUENCE OF BEAM:-
1. THE MAX SPEED ACHIVABLE WITH CONSTANT POWER AT FIRST
INCREASE RAPIDLY WITH INCREASE OF BEAM , THAT REACHES
MAXIMUM AND THEN GRADULLY DROPS.
2. QPC DIDN’T VARY SYSTEMATICALLY WITH BEAM.
3. THE OPTIMUM L/B = 6.93 AND DIDN’T VARY MUCH WITH THE
REVOLUTIOIN.
4. THE VALUE FOR OPTIMUM BEAM DECREASES WITH INCREASE OF
RPM.
5. OPTIMUM BEAM FOR MINIMUM RESISTANCE IS THE SAME AS THE
OPTIMUM BEAM FOR MAX Q.P.C. THIS GIVES BEST ALL ROUND
PERFORMANCE.
INFLUENCE OF THE SAHPE OF THE BODY SECTION
1. THE PROPULSIVE COEFFICIENT & SPEED OBTAINABLE CONSTANT
POWER BOTH ROSE QUICKLY AT FIRST WITH INCRESE IN VERTICAL
PRISMATIC COEFFFICIENT AND REACH MAX AT 0.9.
2. THE OPTIMUM VERTICAL PRISMATIC COEFFICIENT DECREASE WITH
INCREASE IN R.P.M.
3. THE SLOW RUNNING SCREWS HAVE HIGHER EFFICIENCY.

EFFECT OF HULL STRUCTURE
► INFLUENCE OF THE SHAPE OF THE AFTER BODY
1. AT LOW PROPELLER REVOLUTIONS & CONTABT POWER THE PROPULSIVE
EFFICIENCY AND THE MAXIMUM SPEED OBTAINABLE INCREASED AS THE
CENTRE OF BOUYANCY IS MOVED FWD AND AFTER BODY LINES WERE
FINED; THE VALUE RECHED A PEAK AND THEN GRADULLY DECREASED.
2. WITH INCREASE IN RPM, THE OPTIMUM POSITION OF THE CENTRE OF
BOUYNACY MOVES FWDAND THE AFT LINES MUST BE FINED.
3. Q.P.C. INCREASED WITH R.P.M. WITH RATE OF INCRFEAS DEPENDED ON
THE POSITION OF THE CB.
4. THRUST DEDUCTION FACTORVARIED WITH THE POSITION OF THE CB BUT
REAMINED CONTANBT W.R.T.RPM.
INFLUENCE OF BEAM:-
1. THE MAX SPEED ACHIVABLE WITH CONSTANT POWER AT FIRST INCREASE
RAPIDLY WITH INCREASE OF BEAM , THAT REACHES MAXIMUM AND THEN
GRADULLY DROPS.
2. QPC DIDN’T VARY SYSTEMATICALLY WITH BEAM.
3. THE OPTIMUM L/B = 6.93 AND DIDN’T VARY MUCH WITH THE
REVOLUTIOIN.
4. THE VALUE FOR OPTIMUM BEAM DECREASES WITH INCREASE OF RPM.
5. OPTIMUM BEAM FOR MINIMUM RESISTANCE IS THE SAME AS THE
OPTIMUM BEAM FOR MAX Q.P.C. THIS GIVES BEST ALL ROUND
PERFORMANCE.
INFLUENCE OF THE SAHPE OF THE BODY SECTION
1. THE PROPULSIVE COEFFICIENT & SPEED OBTAINABLE CONSTANT POWER
BOTH ROSE QUICKLY AT FIRST WITH INCRESE IN VERTICAL PRISMATIC
COEFFFICIENT AND REACH MAX AT 0.9.
2. THE OPTIMUM VERTICAL PRISMATIC COEFFICIENT DECREASE WITH
INCREASE IN R.P.M.
3. THE SLOW RUNNING SCREWS HAVE HIGHER EFFICIENCY.

EFFECT ON PRIME MOVER
► EFFECT OF HULL FOULING
1) IT HAS LITTLE EFFECT ON THE PROPELLER CURVE, OR HULL PROPELLER
INTERACTION.
2) IT INCRESES THE HULL RESISTANCE AND THE SPEED DROP
SUBSTANCIALLY.
3) INCREASES WAKE FRACTION AND HENCE THRUST DEDUCTION.
INFLUNCE OF THE NO OF BLADES:-
1. WITH INCREASE IN THE NUMBER OF BLADES THE EFFICIENCY DECRASE.
2. NORMALLY PROPELLERS ARE OF 4 TO 6 BLADES.
3. CHANGE IN EFFICIENCY/ NO OF BLADES 2%.
4. NO OF BLADES ARE PREDOMINANTLY CHAOSEN FROM VIBRATION
CONSIDERATION.
• INFLUNCE OF PROPELLER DIAMETER
1) LARGER DIAMETER MEANS SLOWER SPEED OF REVOLUTION.
2) SLOW SPEED X-HD SUPER LONG STROKE ENGINES ARE MORE SUITABLE
FOR THIS DUTY.
3) LARGE DIAMETER SLOW SPEED PROPELLERS GIVE BETTER PROPELLER
EFFICIENCY.
4) THE LARGE DIAMETER HAS TO BE ADJUSTED CONSIDERING DRAFT
RESTRICTIONS AND MINIMUM HULL CLEARENCE.
• EFFECT OF SKEW
1. DOESN’T CHANGE POWER ABSORBTIONOR THRUST DEVOLOPED.
2. MAINLY INTRODUCED TO MINIMISE PRESSURE PULSATION DURING BLADE
TRANSITION ACROSS POINTS ON THE DISC.
3. REDUCE VIBRATION USEFUL FOR STEALTH.

EFFECT ON PRIME MOVER
► PROPELLER AREA RATIO AE/AO :-
1) DOESN’T SIGTNIFICANTLY INFLUNECE THE POWER CURVE.
2) LARGE BOSS/DISC AREA REDUCES THE EFFICIENCY.
3) AS SURFACE AREA INCREASES, SO DOES DISC FRICTION, HENCE LARGE
BLADE AREA TENDS TO REDUCE THE FEFICIENCY.
4) THE MINIMUMK SURFACE AREA IS FIXED BY BLADE LOADING IN EXTREME
CONDITION AND THE ONSET OF CAVITATION.
INFLUNECE OF THE PITCH/ DIAMETER RATIO:-
1) IT TOTALLY DECIDES THE ENGINE LOADING AND THE ACHIVABLE SPEED,
AND HENCE FUNDAMENTALLY INFLUNCE PERFORMANCE.
2) MUST BE ADJUSTED AS PER ENGINE CHARECTERISTEICS AND PROPELLER
HULL INTERACTION.
3) THE PITCH EASILY MEASURED IS “FACE PITCH” WHICHJ IS DIFFERENT
FROM THE “EFFECTIVE PITCH” DUE TO THE EFFECT OF THE BLADE
THICKNESS.
4) THE PITCH TO BE CONSIDERED IS THE MAEN PITCH ESTIMATED BY
ASSUMING EQUAL POWER ABSORPTION ACROSS THE DISC OF FREE
RUNNING PROPELLER:-
PM3 = (ΣPX
3 X )/ΣX
5) OVERPITCHING CAUSES ENGINE OVERLOADING AND THE RPM WILL LESS
THAN EXPECTED FOR THE GIVEN VESSEL SPEED.
6) UNDER PITCHING WILL CAUSE THE VESSEL SPEED TOBE LESS THAN
DESIRED AT THE RATED R.P.M., IT WILL ALSO HAMPER THE POWER
ABSORPTION BY THE PROPELLER. IT SHOULD BE CONFIRMED BY DOCK
TRIALS.

SERVICE ALLOWANCE
INSPITE OF THE VERY LARGE VARIATION IN THE
ALLOWANCE (1% TO 80%), THE PROPELLER CURVE ARE
VERY CLOSE TO EACH OTHER.
ROUGHENING OF THE HULL WILL CAUSE THE BOUNDARY
LAYER TO GROW AND WILL CHANGE THE DISTRIBUTION
OF VELOCITYOF FLOW ALONG THE HULL AND WILL
INCRESE THE THE RESISTANCE BY UP TO 25% TO 50%
THROUGHOUT THE LIFE TIME OF THE SHIP.
THE ROUGHENING OF THE PROPELLER WILL INCRESE THE
DISC FRICTION AND DECREASE THE HYDRODYNMAMIC
EFFICIENCY AND MAY CAUSE LOCAL FLOW
SEPERATIONAND TURBULENCE IN CASE FO EXCESSIVE
DAMAGE.
THE SERVICE CONDITION HAS LTTLE IN FLUENCE ON THE
POWER CURVE BUT A LARGE INFLUENCE ON THE DESIRED
SPEED AND THE NECESSARY POWER REQUIRED FOR A
FIXED SPEED, WHICH INCREASES SHARPLY WITH THE
INCREASE IN THE SERVICE ALLOWANCE.

SHIP PROPELLER INTERACTION AT
EXTREME WAETHER CONDITION
THE MAXIMUM LOADING
OCCURS DURING THE SHIP
ACCELERATION AND
DECELEARTION AND DURING
THE BAD WEATHER. THE
WAKE FRACTION AND THE
THRUST DEDUCTION
SIGINIFICAYNLY INFLUENCE
THE ACCLERATION AND
DECELARTION; AND
IMPORTANT PARAMETER IN
MANOEUVRING
PERFORMANCE EVALUATION.
THIS SIS DETERMINED BY
EXTENSIVE MODEL TESTING
ωT = {VS – VA}/ VS ≡{ JV – JA
}/ JT
JV = VS /nD ; JA = VA /nD
KT = T / ρn2D4 ; KQ = Q /
ρn2D4
KR = [ R+F] / ρn2D4
Where
R = resistance of free towage
F = force required for
acceleration and deceleration
ρ = salt water density.
D = propeller disc diameter.
n = rate of revolution.
t = {T – R}/ T ≡ (KT - KR)/ KT
At extreme loading the ωT
increases while the t tends to
decrease.

ALTERNATIVE PROPULSION SCHEME
TO IMPROVE VARIOUS DEFICIENCYOF ECONOMICAL AND
SIMPLISTIC PROPULSION STRATAGIESSEVERAL ALTERNATIVE
SCHEMES ARE SUGGESTED. THE RELATIVE ADVANTAGES CAN
BE GROUPED UNDER THE FOLLOWING HEADINGS:-
i. THE NORMAL PROPELLER EFFICIENCY IS 70%; 30% OF THE
ENGRGY IS WASTED , 10% DUE TO FRICTIONAL LOSSES, 10%
DUE TO ROTAIONAL LOSSES., 10% LOSS IN THE MOMENTUM.
ii. THEY HAVE GREATER DIRECTIONAL STABILITY, QUITE A FEW
HAVE THE ABILITY TO VECTOR THE THRUST ABOUT AN ANGLE
OF 360˚IN THE HORIZONTAL PLANE.
iii. SOME OF THESE HAVE THEADIITIONAL ADVANTAGES SUCH AS
SIMPLYFYING THE PLANT , REDUCING COMPOENETS SUCH AS
STEERING GEAR IN FORM OF INCREASE PART LOAD
EFFICIENCYAND REDUCED HARBOUR COSTS DURING BERTHING
THE ALTERNATIVE PROPULSION SCEMES ARE:-
 MULTIPLE SCREW ARRANGEMENT.
 RUDDER PROPELLERS/ ACRIVE RUDDERS
 GRIM WHEELS
 SHROUDED/ DUCTED PROPELLERS
 CONTROLLABLE PITCH PROPELLERS
 AZIMUTHING THRUSTERS
 CONTRAROTATINGPROPELLERSAND PODDED CRP.
 WATER JET AND PUMP JET]
 VERTCAL AXIS OR CYCLOIDAL PROPELLERS

MULTIPLE SCREW ARRANGMENT
 It has the following advantages :-
1. Increased safety through redundancy in
propulsion / prime movers.
2. Increased maneuverability.
3. Can utilize larger disc diameter when maximum
diameter of the propeller cannot be used due
to draft restriction or restriction of height ,
position and type of engine.
 The disadvantages are :-
1. Much higher installed capacity costs.
2. Much more complicated stern frame design.
3. Necessitates increased number of rudder and
steering gear.
4. Lesser efficiency than single screw able to
absorb the full power.

RUDDER PROPELLER
 Predominantly used as an auxiliary propulsion device
or steering aid. This has the following advantages:-
1. Good control especially when starting from rest.
2. Unlike lateral thrust propeller, the control improves
with speed.
3. If necessary, a lift mechanism can adjust the unit to
the ships draught.
4. To reverse the vessel the propeller is slewed 180˚.
Astern action is more efficient than normal rudder.
 The disadvantages are :-
1. Propeller has to be fixed to the supporting mechanism
which increases the resistance.
2. Complicated Z- gearing.
3. Currently limited power rating in the design.
4. Interference of the jet with hull or adverse effects
caused with interference with the main propeller race.

GRIM WHEEL
 It is simple arrangement easy to retrofit
and has the following advantages :-
1. Propulsion efficiency increases by up to
15%.
2. The main propeller can be operated at a
higher rpm favorably affecting the
weight and the cost of the prime mover.
3. Grim wheel can be as large in diameter
as possible since the large number of
blades and low speed of wheel allow
small vertical clearance.
4. There is less resistance from the rudder
fitted behind a grim wheel; this is shown
in th increased RRE.
5. Ships fitted with this device have better
stopping ability.

DUCTED/SHROUDED PROPELLER
 The arrangement is commonly known as the kort nozzle after its inventor and
is found in three types of design
a) Accelerating
b) Neutral.
c) Decelerating
 Most commonly only the accelerating type are used which found in two types
of installation.
i. Fixed nozzle and
ii. Steerable nozzle.
 The steerable accelerating nozzle is of the maximum advantageous types
whose features includes:-
I. Improvement in the propulsive efficiency of up to 20%.
II. Increased bollard pull by 30%.
III. Improvement in bad weather performance.
IV. Pressure velocity variation due to wake field generally smoothened out
reducing hull vibration.
V. Simplicity in fitting with little alteration to the hull structure.
VI. Improvement in the astern maneuvering performance.
VII. Improved Steerability due to much higher steering moments, requiring much
lesser helm angle .
VIII. Reduced blade loading.
 The minor disadvantages are:-
I. This arrangement increases the effectiveness of the suction field and hence
may hasten the incept of cavitation.
II. The steering forces are much larger hence the rudder bearing and the
steering system has to be adequately designed.
III. The propeller diameter has to be reduced compared to a “free” propeller due
to the geometrical consideration of the arrangements.

CONTROLLABLE PITCH PROPELLER
Despite the initial first costs and the marginally lesser peak efficiency
Than a F.P.P operating at the optimum condition; the C.P.P has the
following advantages:-
1. Rapid reversal of thrust from ahead to astern and practically unlimited
no of reversing not dependent on the air bottle pressure.
2. Full power in astern thrust, compared to a steam turbine and direct
coupled diesel engine where the engine parameters doesn’t ensure
optimum performance during the astern maneuvering due to timing
consideration.
3. Optimum utilization of power at partial loading. When load on the
engine is reduced the relationship between the rpm and DHP can be
altered by changing the propeller pitch so that optimum efficiency is
guaranteed for the power being developed.
4. The engine overloading can be avoided by automatic pitch control ->
The system reduces pitch if the permitted cylinder pressures are likely
to be exceeded at maximum engine loading.
5. Constant speed operation means operation in the optimum speed
range leading to fuel costs savings and avoidance of barred speed
ranges during maneuvering.
6. Possible improvement in propulsive efficiency, simple engine plant
(e.g. a gas turbine), greater maneuverability and less wear and tear.
7. Spare propeller blades are cheaper than a complete spare solid
propeller of fixed pitch type. In a standardized fleet of one type of C.P.
propeller spare parts costs are reduced.
8. The ability to drive shaft generators and pumps from the main engines
results in direct savings in the fuel costs particularly if auxiliary engine
operates on diesel oil.
9. Greater maneuverability means increased savings from the harbor
costs if tugs are not used.

Azimuthing thrusters
This drive can deliver thrust through 360˚in the
horizontal plane but presently there are limitations in
the maximum installed power. This combination of
steering and thrust executed by one mechanical device
gives the following advantages:-
1. Most effective application of the thrust as the whole unit
is turned to direct the propeller thrust to where it is
wanted rather relying on the deflection by the rudder.
2. Very precise and reliable steering of the vessel,
through thrust direction.
3. Ease of vessel control through single lever system or
microprocessor controllers linking more than one unit.
4. Much simpler machinery installation with no shaft
bearing housing to be bored, giving more flexibility in
stern design of the vessel.
5. Great flexibility in choice of propulsion units such as
direct drives, electric motors etc, if a constant speed
C.P.P. is used the engine transmission system can be
used.
6. The engine room length can be remarkably shortened
and the payload section of the vessel can be increased
by 5% to 10%.

CONTRAROTATING PROPELLER AND PODDED CRP
 Concept was first introduced by erricssion in 1839., but only recently being
used in large merchant vessels.
 Traditionally used for torpedoes due to natural torque compensation.
 Recovery of the rotational energy from the propeller race up to 10% of the
DHP.
 Complication in the sealing, bearing and gearing arrangement prevented
widespread acceptance so far.
 This problem was solved by the podded CRP concept, where a contrarotaing
propeller on a electric pod or a z-drive thruster is located directly behind the
main propeller in the centre-line skeg. The two propeller are arranged as
close as possible to each other.
 The arrangement gives 20% reduction in fuel consumption.
 As power is shared between 2 propellers the reduced blade loading delays
the onset of cavitation.
 Much greater steering moments requiring lesser angles of helm.
 Better cavitation performance.
 A split of 25% on the electric pods and 75% for the main C.P.P. is the best
recommended power division.

Water jet and Pump jet
 A typical design of water jet has an axial flow impeller with a
wide cord; running close to the pump casing with stator vanes
to straighten the water flow to prevent rotational exit loses.
The advantages are:-
1. For a given power loading higher static thrust can be provided
then even the shrouded propeller.
2. Ability absorb full engine power at all water speed without
cavitating.
3. Much enhanced steering capability due to ability to use
directional thrust.
4. Superior accelerating characteristic than propeller.
5. Can use unidirectional engines.
6. Can operate in regions with very limited depths.
 A variation of the water jet is pump jet developed by the
Schottel using a vertically mounted centrifugal pump with an
outlet jet directed down at an angle of 15˚, while the thrust can
be directed 360˚ in the horizontal plane.
 It is predominantly used as bow-thruster and a steerable
thruster unit.

Vertical Axis/ Cycloidal Propeller
 There are two types of designs:-
1. KRISTEN BOEING :-The blades are so interlocked by gears that each
blade is constrained to make half rotation about the axis for each
revolution about the axis of the propeller. The motion is a cycloid.
2. VOITH-SCHNIEDER :- The blades complete a rotation about their own
axis for each complete revolution about the propeller. The orbit is a
epicycloids .
 The advantages are :-
1) Ability to direct the thrust through 360˚ in the horizontal plane.
2) Use of constant speed unidirectional drive as C.P.P. no reversing
ability required.
3) With two units fitted in the fwd and astern a strictly lateral movements
can be obtained.
4) The propeller is used for normal steering and NO rudder is required.
 The disadvantages are :-
1) Complicated mechanism difficult to maintain.
2) Much more costly to install and maintain.
3) The hull must be specially constructed to receive the propeller.
4) The generated thrust is lesser than the conventional propeller and
much less than ducted propeller.

conclusion
 From the above discussion we see that the propulsion. System for merchant marine vessel
have come a long way from its humble beginning in the earliest days of the history of
mankind. We have also seen the modern shipping as a martin transportation agency for
man and materials from the backbone for the international trade ; which itself has reached
colossal dimensions. Economics for several developing and developed countries depend
on this maritime trade. Hence anything or any significant advancement furthering this
interest is going to have a huge and global impact over entire world economy which will
ultimately lead to prosperity of mankind.
 Recent boom in maritime transportation and present stress on building bigger, fast and
more efficient ship is throwing up new challenges for ship builders, naval architects or
engine builders alike. The huge increasing and sustained demand for containerized cargo,
LNG transportation and oil and bulk ore carriage to feed the insatiable demand for human
development is opening up new frontiers for research and development. Projects like fast
phods and HTS super conduction motors and MHD propulsionhorizons, set new standards
for performance and business volume and it is now poised for a major breakthrough in the
marine propulsion sector. systems underline the keen interest of the shipping world to
define new horizons, set new standards for performance and business volume and it is now
poised for a major breakthrough in the marine propulsion sector.

Conclusion contd
 This paper attempts to analyse and review the various propulsion scheme in practice in conceptual stages in various laboratories
or adopted by various of the world or already in use in same types vessels in some parts of the world. What is very disappointing
to note in the very slow speed of induction of these novel propulsion concepts into wide spread practice of ship building for a
wider range of merchant vessel work over. This is despite the fact that some of these noval propulsion concepts can really go a
long distance in solving some of the challenge being faced by the marine transportation, and many of them have clear and
prevent advantages in terms of higher efficiency, moise and vibration education, increased bollard pull, better manoverability and
higher swings. We can refer to the slow utilization of electric propulsion currently only used in passenger ship propulsion, slower
use of intelligent engine designs.

 The world depleting natural resources such as oil and correspondingly deteriorating quality of bunker and the increasing price had
thrown up some odd challenges in front of the growing marine transport sector. Nuclear marine propulsion is a solution to all of
this problems, which has been successfully implemented in the various marines of the world but the merchant marine application
has been totally lacking. The barrier to the successful application is neither technological or economics it purely psychological and
political. Thus situation should change ship owners association such as ICS and international legislative bocks such as INO
should get together and make this happen and develop as political concesus within the member governments to fund the national
ship building towards this ends and remove obstacles to make free trading by Nuclear ships a possibility.
 Further more we have several innovation discharge have been mentioned regarding propeller such as grim wheel, kort nozzle
contra- rotating podded population systems, water jets and pump jet these have marked advantage over the commercial
arrangements but the application for these concepts are not widespread as they should be thus flush indicate a widespread
apathy towards the acceptance and application of new design by ship builders and ship owners, a better networking between
research labs equipment manufacture and shipyards are required.
 The conclusion of the situation that as far as marine propulsion reach is concerned merchant marine sector lacks far behind its
counterparts such as commercial aircraft, and national navies. Thus situations must improve, since the commercial shipping
literally drinks from the well it digs, unless the governments around the globe combine the efforts to fund research and distribute
knowledge and unless a better network and cooperation exists for information exchange and unless classification societies, and
ship owners, underwriter all come together with a willingness to implement those path-breaking research solution, the shipping
and whole of humanity will be deprived from the benefits which be incurred from them.

Marine propulsion, alternative propulsive devices.ppt

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