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SHIP PROPULSION

SYTEMS

Prof. Emin Korkut

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SYLLABUS

1. Introduction to Ship Resistance and Propulsion

2. Introduction to Propulsion Systems

3. The Ship as a Federation of Systems, Review of

Main Machinery; Power Plant Concepts

According to Ship Types

4. Review of Main Machinery; Diesel power plant,

Gas turbine power plant, steam and nuclear power

plant, Combined power plants

5. Transmission system and its components

6. Propulsors

7. Machinery selection-The Designer’s choice:

Criteria’s how to choose prime mover

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SYLLABUS

8. Marine Diesel Engines

9. Marine Gas Turbines

10. Engine room layout; General arrangement of a

ship, machinery spaces, noise in machinery

spaces, simple torsional vibration calculations

11. Engine room layout; General arrangement of a

ship, machinery spaces, Lloyd Rules

12. Alternative marine propulsion systems. Sub-

systems of propulsion system (typical fuel,

electrical, air, lubrication oil, cooling system etc.).

Fuel types in marine field

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REFERENCES

• Ship Propulsion Systems by Mohamed Morsy El-

Gohary & Hossam Ahmed El-Sherif.,

• Modern Ship Design by Thomas C. Gillmer

• Marine Propellers and Propulsion, Carlton, J.S,

2007, 2nd Ed., Butterworth-Heinemann, ISBN:

978-07506-8150-6

• Ship Design and Construction Vol-I,II, SNAME

• Marine Gas Turbines, Woodward, John B., ISBN

0-47195962-6

• Course text Marine Gas Turbines, Woodward,

John B., ISBN 0-47195962-6

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Lecture notes can be found at:

http://pruonline.pirireis.edu.tr/

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Assessment

Criteria

Activities Quantity Effects on

Grading,

%

Midterm 1 30

Homework 2 10

Term Paper/Project 1 20

Final Exam 1 40

TOTAL 100%

Effects of Midterm

on Grading, % 60%

Effects of Final on

Grading, % 40%

TOTAL 100%

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Introduction to Ship Resistance and Propulsion

Resistance:

• The act of stopping, opposing or withstanding when

an object is in motion in a fluid.

• Ships, aircrafts, cars etc. experience resistance

when they are in motion. Frictional forces of the

water/air against the moving object cause this

resistance.

T

V

RT (RESISTANCE) Main engine

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T o t a l R e s i s t a n c e

R e s i d u a r y R e s i s t a n c e

W a v e R e s i s t a n c e

V i s c o u s P r e s s u r e R e s i s t a n c e

F r i c t i o n a l R e s i s t a n c e ( F l a t P l a t e )

V i s c o u s R e s i s t a n c e

Fr r

C

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• Types of Resistance

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• Resistance of a ship depends on speed, displacement

and type of a hull form.

• The total resistance RT, is composed of mainly three

components

– a) Frictional resistance, RF

– b) Residual resistance, RR

– c) Air resistance, RA

• Frictional resistance RF of the hull depends on the

size of the hull’s wetted area S, and on the specific

frictional resistance coefficient CF.

• When the ship is in motion through the water, the

frictional resistance increases at a rate proportional

to the square of the speed of the ship.

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• Frictional resistance represents a considerable part of

the ship’s resistance, often some 70-90% of the

ship’s total resistance for low-speed ships (bulk

carriers and tankers), and sometimes less than 40%

for high-speed ships (cruise liners and passenger

ships).

• Residual resistance RR comprises wave resistance

and eddy resistance. Wave resistance refers to the

energy loss caused by waves created by the vessel

during its propulsion through the water, while eddy

resistance refers to the loss caused by flow

separation which creates eddies, particularly at the

aft end of the ship.

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• Wave resistance at low speeds is proportional to the

square of the speed, but increases much faster at

higher speeds. In principle, this means that a speed

barrier is imposed, so that a further increase of the

ship’s propulsion power will not result in a higher

speed as all the power will be converted into wave

energy. The residual resistance normally represents

8-25% of the total resistance for low-speed ships,

and up to 40-60% for high-speed ship.

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Prediction of Effective Power (Resistance):

• For Model Testing: In order to achieve a flow

similarity between two geometrically similar bodies

(full-scale ship and model) Froude similarity should

be satisfed that the non-dimensional parameter,

Froude number (Fr) should be the same for the ship

and model.

𝐹𝑟 =𝑉

𝑔𝐿𝑊𝐿

= 𝐹𝑟𝑠 = 𝐹𝑟𝑚

where g is acceleration due to the gravity, LWL is the

ship length in waterline, indices ‘s’ and ‘m’ represent

ship and model, respectively.

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a) Froude’s Method: The resistance of a model or ship

can be split in two components: a frictional resistance

and residuary resistance as CT=CF+CR

i- Scale factor between ship and model is defined λ =𝐿𝑆

𝐿𝑀

and this yields 𝑉𝑀 =𝑉𝑆

λ

ii- Measure RTM corresponding to the model velocity, VM

iii- Calculate total resistance coefficient of the model as

𝐶𝑇𝑀 =𝑅𝑇𝑀

1

2𝜌𝑀𝑆𝑀𝑉𝑀

2

iv- Frictional resistance that is supposed equal to that of

an equivalent flat plate and usually given by ITTC1957

formula: 𝐶𝐹𝑀 =0.075

(𝐿𝑜𝑔 𝑅𝑒𝑀 −2)2 𝑅𝑒 =

𝑉𝐿

𝜈 where 𝜈 is the

kinematic viscosity of water

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v- CTM=CFM+CR then, CR=CTM- CFM Residual coefficient

CR will be the same for model and ship.

vi- Ship frictional resistance coefficient is calculated as

𝐶𝐹𝑆 =0.075

(𝐿𝑜𝑔 𝑅𝑒𝑆 −2)2

vii- Then, the total resistance coefficient of the ship is

obtained as CTS=CFS+CR

viii- Total resistance of the ship is calculated by using the

formula 𝑅𝑇𝑆 = 𝐶𝑇𝑆1

2𝜌𝑆𝑆𝑆𝑉𝑆

2

ix- Finally the effective power of the ship is calculated as

PE=RTSVS

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a) ITTC1978 Method: The resistance of a model or ship

can be split in two components: viscous resistance

and residuary resistance as CT=CV+CR=(1+k) CF+CR

where (1+k) is the form factor and determined by

Prohaska method.

Similar to Froude method;

v- CR=CTM- (1+k)CFM Residual coefficient CR will be the

same for model and ship.

vi- Ship frictional resistance coefficient is calculated as

𝐶𝐹𝑆 =0.075

(𝐿𝑜𝑔 𝑅𝑒𝑆 −2)2

vii- Then, the total resistance coefficient of the ship is

obtained as CTS=(1+k)CFS+CR

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viii- Total resistance of the ship is calculated by using the

formula 𝑅𝑇𝑆 = 𝐶𝑇𝑆1

2𝜌𝑆𝑆𝑆𝑉𝑆

2

ix- Finally the effective power of the ship is calculated as

PE=RTSVS

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Propulsion:

• Propulsion is the act or an instance of driving or

pushing forward of a body, i.e. ship, by a propeller

(in our case a screw propeller).

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Summary of efficiencies in powering

Reduction gear

B

PD T

PT

PB S

V

RT

PE

D

H

BEHIND HULL

R

0

PT

PD0

OPEN WATER

Main engine

B

DS

D

T

D

D

R

D

TB

T

E

H

D

E

D

P

P

P

P

P

P

P

P

P

P

P

P

0

0

0

RB 0

HRD 0

T Thrust

R Resistance

V Ship speed

PT Thrust power

PD Delivered power in behind hull condition

PD0 Delivered power in open water condition

PB Brake power

PE Effective power

0 Open water efficiency

R Relative-rotative efficiency

B Behind hull efficiency

S Shaft transmission efficiency

H Hull efficiency

D Propulsive efficiency