Matching Propulsion Engine With Propulsor

Journal of Marine Marine Engineering & Technology Technology

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Matching propulsion engine with propulsor D Stapersma & Hk Woud To cite this article: D Stapersma & Hk Woud (2005) Matching propulsion engine with propulsor, Journal of Marine Engineering & Technology, 4:2, 25-32

To link to this article: http://dx.doi.org/10.1080/20464177.2005.11020189

Published online: 01 Dec 2014.

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Date: 26 Date: 26 June 2017, At: 00:35

Matching propulsion engine with propulsor

Matching propulsion engine


Matching propulsion engine with propulsor D Stapersma, Professor of Platform Systems, MSc, CEng, FIMarEST and HK Woud, Professor of Marine Engineering, MSc, FIMarEST, Delft University of Technology The basic matching problem of a propulsion engine to the propulsor is discussed and the influences which should be taken into account.The concepts of sea margin, engine margin and light running margin are handled and an indication of their values is given. The methods of calculation to evaluate design and off design conditions are discussed. Key words: matching, propulsion, engine, propulsor, sea margin, engine margin, light running margin, off-design conditions.

INTRODUCTION

W

ith the design of a ship’s propulsion system the correct matching of the prime mover(s) to the propulsor(s) and the ship is of great importance. In case the matching problem is not solved adequately the ship may have problems with regard to overloading prime movers, attainable speeds in off design conditions and an excessive fuel consumption.

AUTHORS’ BIOGRAPHIES J Klein Woud graduated in 1966 as a mechanical engineer at Delft University of Technology, with specialisation in internal combus tion (diesel) engines.After military service in 1968 he joined Stork Werkspoor Diesel where he worked as application engineer for marine diesel engines. During 1970-1986 he worked for the naval design office, Nevesbu,The Hague, where he was involved with the design and engineering of frigates, submarines and patrol craft and their machinery systems. In October 1986 he was appointed professor of marine engineering at Delft University of Technology. He lectures on marine engineering systems and conducts research with regard to condition monitoring, maintenance and design techniques. During January 1995-June 1998 he was dean of the Faculty of Mechanical Engineering and Marine Technology. Since 2000 he is the Director of Education for Mechanical Engineering and Marine Technology. Douwe Stapersma graduated at Delft Technical University in the field of gas turbines, joined Nevesbu in 1973 and was involved in the design and engineering of the machinery installation of the Standard frigate. After that he coordinated the integration of the automatic propulsion control system for a class of export corvettes. From 1980 onward he was responsible for the design and engineering of the machinery installation of the Walrus class submarines and in particular the machinery automation.Then he was in charge of the design of the Moray class submarines in a joint project organisation with RDM. Nowadays the author is professor of Naval Engineering at the Royal Netherlands Naval College and Marine Diesel Engines at Delft Technical University. He is the coauthor of the book ‘Design of propulsion and electric power generation systems’ which is a standard text in marine engineering.

No. A7 2005

Journal of Marine Engineering and Technology

The propulsion system should not only operate satisfactorily in the design condition of the ship, but also in off-design situations, which the ship might encounter. Relevant offdesign situations may involve: variation of ship displacement, increased resistance due to seaway, the influence of the number of driving engines and active propulsors and of a shaft generator. The methods described in this paper are extensively discussed.1

BASICS Resistance and propulsion Often for a ship hull a square resistance curve is assumed (R=c1.vs2, which implies a cubic power/ship speed relation PE=R.vs=c1.vs3. R is the towing resistance of the hull, v s is the ship speed). In reality the factor c 1 is not constant. The effective towing power can also be written as: P E

1

2

= C E ⋅ ρ 3 ⋅ ∆ 3 ⋅ vS 3 ,

(1)

which shows the primary dependency on displacement ∆. The specific resistance C E is depending on speed, hull form, fouling, sea state and water depth. Fig 1 shows some typical examples of resistance curves. A square curve (1) may be valid for Froude numbers of 0.1 – 0.2. For higher Froude numbers the resistance may change with speed more rapidly as indicated by curve (2). High speed craft like planing ships may have curves like (3). The ship is propelled by a machinery plant which delivers a total power P D to the propulsors. The total propulsive efficiency is now defined as: def

η D

=

P E P D

where PD=kp.Pp. where kp is the number of

, propellers and Pp the delivered power to one propeller. The propulsive efficiency can be expressed in hull efficiency ηH, propeller open water efficiency ηO and relative rotative efficiency ηR: η D

= η H ⋅ ηO ⋅ η R 25


R

def

3

η R

=

PO P p

=

Q

(4)

M p

0.8

Square curve

0.7

1

0.6

resistance curve with higher powers

ηO

0.5

10 K Q

2

10 K Q

K T

0.4

ηO

K T

0.3 0.2 0.1 0.0 0.0

V

Fig 1: Different types of hull resistance characteristics

ηH = PE/(kp.PT) = R.vs/(kp.T.vA) 1 − t which proves to be equivalent with η H = 1 − w . This follows from the definitions of thrust deduction t and wake fraction w: k p ⋅ T

−R

k p ⋅ T

def

w=

vS

− vA vS

0.6

0. 8

1.0

1.2

Fig 2: Example of screw propeller open water diagram

The propulsor delivers a thrust power PT =T.vA, where T is delivered thrust (of one propeller) at a velocity of advance vA. The relation between effective towing power and thrust power is given by the hull efficiency

def

0.4

Advance ratio J

Propulsor/hull interaction

t =

0.2

In case screw type propellers are used, the non-dimensional open water diagram (Fig 2) will be used. It gives the relation between torque, thrust, ship speed and propeller speed. Thrust and torque are made non-dimensional with propeller speed np, diameter D and sea water density ρ. Thrust coefficient: K T = ρ ⋅ n

T

⋅ D4

(5)

⋅ n p 2 ⋅ D 5

(6)

2

p

=

Q

leading to R=(1-t) . kp . T

(2)

torque coefficient: K Q

leading to vA=(1-w) . vs

(3)

v A as function of advance ratio: J = n ⋅ D p

The thrust deduction allows for the fact that while a part of the produced thrust is used to overcome the pure towing resistance, the remaining part is to ov ercome the added resistance due to the propeller in fluence on the hull. The wake fraction allows for the difference between ship speed vs and advance velocity vA experienced by the propeller, as a result of the boundary layer in the wake of the hull.

ρ

(7)

The open water efficiency can be now expressed in these three terms:

ηO

=

1

⋅

T ⋅ v A

2π Q ⋅ n p

=

K T ⋅ ρ ⋅ n p 2 ⋅ D 4 ⋅ vA

2π ⋅ KQ ⋅ ρ ⋅ n p

2

⋅ D ⋅ n p 5

=

1 2π

⋅

KT ⋅ J K Q

Propulsor The open water propeller efficiency relates the thrust power PT to the propeller power PO in open water condition, ie, without the influence of the hull: def

ηO

=

PT PO

=

1

⋅

T ⋅ v A

2π Q ⋅ n p ,

where Q is the torque in open water condition and np the rotational speed of the propeller. In reality with the propeller behind the hull, the actual propeller torque Mp and power Pp are slightly different. The ratio between actual and open water values is called the relative rotative efficiency:

26

In case water jets are used it is not customary to receive open water diagrams from the manufacturer. One gets a diagram as shown in Fig 3. This diagram gives the same information as an open water diagram: thrust and torque as function of impeller speed and ship speed but now for the installed condition in the hull.

Propulsion plant The propulsion system consists of a number of propulsors, a transmission installation and driving engines. An example is shown in Fig 4. This plant has two identical propellers (kp=2) and per shaft line two identical engines (ke=2), combined


No. A7 2005


thr ust breakdown

ship resistance

T

design poin t cavitation limit

100% m1

P1

n=100

75% m1

turbocharger limit con tinuous operation

90

50% m1

80 70

25% m1

60 V1

M1

n???

n???

n???

design poin t 100% m1

M1 n=100 90

75% m1

80 60

50% m1

70 V1

25% m1

Fig 3: Example of a performance diagram of a water jet/hull combination

G8

P1 main engine

P1

P1 P1

M1 [%] 100

2

80

6

main engine

P1 G8

P1

1-propeller curve Tor que limits of engines that are: 2-naturally aspirated 3-single stage constan t pressure turbocharged p=20bar 4-single stage pulse system turbochargd p=20bar 5-highly turbocharged p=30bar 6-sequen tially turbocharged

60 P1 main engine

4

40

3 5

20

Fig 4: Propulsion plant with definition of powers

1

0 0

through a gearbox (GB). The relations between delivered propulsor power P p, shaft power PS and engine brake power P B are given by the shaft, gearbox and transmission efficiencies:

ηs=Pp/PS, ηGB=PS/(ke.PB) and ηTR=ηs.ηGB=Pp/(ke.PB)

(8)

These efficiencies can also be expressed in torque:

ηs=Mp/MS, ηGB=MS/(i.ke.MB) and ηTR= Mp/i.ke.MB where i is the gearbox transmission ratio (n e/np).

Diesel engines The operating envelope of a modern turbocharged diesel engine has five limits: minimum engine speed, maximum engine speed, maximum torque, turbocharger limit and a fouling (minimum torque) limit. Fig 5 shows a typical diagram both in terms

No. A7 2005

n???

main engine

P1

P1

n???

Fig 5: Operational envelope of modern turbocharged diesel engine

P1 P1

n???


20

40

60

80

100

P1 [%]

Fig 6:Torque capabilities of different diesel engine types of power/speed (PB/ne) and torque/speed (MB/ne). The fouling limit normally lies around 25% torque. It is allowed to operate the engine continuously within the area enclosed by these five limits. Operation below the fouling limit is allowed for manoeuvring during limited time periods. For a highly turbocharged engine the maximum torque can be delivered only over a limited speed range, as limited by mechanical and thermal stresses. At lower speeds the turbocharger is not capable to supply sufficient air and therefore maximum torque is limited by thermal load. The operational envelope is rather narrow at high speed and load. This makes operation of these engines especially during increased loads, eg, due to a heavy seaway, difficult. For that reason a number of diesel engine manufacturers

27


P

2

1

MCR

3

operating envelope

propeller load ne

Fig 8: Operational envelope of diesel engine with three propeller load curves Fig 7: Operational envelope of a gas turbine with free power turbine have come with solutions to improve the operational envelope. They apply eg, sequential turbocharging, which results in a much broader envelope. Fig 6 gives an indicative overview of diesel engine torque capabilities for different types of turbocharging. Please note that the figure is given on a non dimensional basis.

] % [ P

90

70 60

40

Matching of a diesel engine with a fixed pitch propeller may consider three propeller load curves: the design condition, a heavy condition (eg, due to a heavy sea way) and a light condition (eg, due to sailing in ballast). Fig 8 shows these three load curves in a

28

EM

CSR

80

A gas turbine, with a free power turbine, has a much wider operational envelope than a diesel engine. The reason is due to the fact that a gas turbine behaves almost as a constant power machine, whereas a diesel engine behaves in principle as a constant torque machine but with a significant reduction due to turbocharging. Fig 7 shows the operational envelope in terms of power/speed. Such a gas turbine only has three limits of the envelope: maximum power turbine speed, maximum and idling fuel flow. In reality the engine is also limited on power by ambient air temperature.

Diesel engine matching with fixed pitch propeller

propeller load at trial conditions

MCR

100

50

When an engine is to be matched with a propulsor the following two criteria should be met:  The engine is able to develop full power, or nearly full power, at the design condition  The propulsion plant functions satisfactorily in all design and off design conditions, ie, delivers the required speed or thrust without exceeding any limits imposed by the operational envelope. A third criterion might be:  The operation of the plant is optimised with regard to fuel consumption.

operating envelope

1

Gas turbines

BASIC MATCHING PROBLEM

propeller load at design conditions

SM

power during sea trial

30 20 10

ne

0

ne

0 10 20 30 40 50 60 70 80 90 100 ne [%]

Fig 9: Fixed pitch propeller matched with turbocharged diesel engine typical operational envelope of a turbocharged diesel engine. This picture clearly shows the problem of a turbocharged diesel engine in combination with a fixed pitch propeller:  When the propeller pitch is not properly chosen the maximum engine output will not be available in the design condition: either the pitch is low and the maximum available power is limited by the maximum speed limit or the pitch is high and the maximum available power is limited by the turbocharger limit.  In off design conditions the full engine power will never be available because of the maximum speed limit in light condition and the turbocharger limit in heavy condition. A good match for such a case is shown in Fig 9. It is assumed that the resistance/ship speed relations for trial and service condition are known. Trial condition refers to the situation of a clean hull, calm sea, deep water and unloaded. The service condition refers to the mean service conditions that the ship will encounter in its operational life. Good practice involves some hull fouling (eg, two years), sea state 2 or 3, deep water and design displacement.

Journal of Mar ine Engineering and Technology

No. A7 2005


propeller load at service conditions

MCR PB EM CSR

propeller load at trial conditions

LRM

dition. This margin is required to achieve reasonable maintenance intervals of the engine, to enable a higher ship speed than design speed in case the ship is behind schedule and to cope with increased loads due to more fouling or a higher sea state than in design condition. This is expressed in the Engine Margin (EM): EM =

nLRM SM

nM

power during sea trial ncsr ne

Fig 10:The EM, SM and LRM

Service margin, engine margin and light running margin The ratio between effective power in service and trial condition is called the service margin (SM): SM =

P E ,Service P E ,Trial

>1

Values for the service margin are 1.1 – 1.25, excluding the influence of the loading condition. For merchant vessels this influence can be significant. It can be estimated with equation (1). The next step will be the design of a suitable propeller. This will result in a propeller power/speed (P p/np) curve, both for trial and service condition. These load curves can be converted to brake power/engine speed (P B/ne) load curves, by use of the transmission efficiency and ratio (equation (8)). Depending on the type of machinery plant: a direct drive system with a low speed diesel engine or a geared drive with medium or high speed diesel engines, the design procedure of the propeller will be different. This is not discussed further in this paper. The load curves as experienced by the engine are then plotted in the operational envelope, resulting in Fig 9. A proper matching means that the service condition curve intersects with the operational envelope at maximum power and maximum speed of the engine. The power at this point is called the Maximum Continuous Rating (MCR). Also the operational points regarding the design speed at trial and service condition are shown. The power at design speed in service condition is called Continuous Service Rating (CSR). As the propulsive efficiency will change only marginally between trial and service condition, the service margin is almost equal to the brake power ratios: P B,Service SM ≅ P B,Trial The MCR power for merchant vessels should be higher than the required brake power at design speed in service con-

No. A7 2005


CSR MCR

P B,Service

=

P B,Max

<1

The engine margin is based on ship owners requirements and experience and will be in the order of 0.8 – 0.9. For naval vessels it is common practice to have no engine margin (EM = 1). This is done because the design top speed is not run continuously, but only during limited periods. The rating of naval engines is not a continuous rating but a peak rating. Some engine manufacturers also define a Light Running Margin (LRM), as shown in Fig 10. The LRM relates the engine speed difference between the service propeller curve and the propeller curve for trial or light running condition at CSR power to the speed at MCR. It is defined as: LRM =

n LRM

− nCSR

n M

The LRM should have a value of 0.05 to 0.06. It is supposed to offer sufficient engine speed margin to maintain constant engine power when the ship deteriorates from trial condition to service condition. Either the SM or the LRM can be chosen. The other will be the result of the margin chosen.

FROM RESISTANCE TO BRAKE POWER To solve matching problems adequately it is essential to convert a resistance/ship speed (R/v s) relation to a brake power/engine speed (PB/ne) relation. This will be shown for a fixed pitch propeller with use of the open water diagram. Consider a resistance/ship speed point: R, v s. This can be converted to a factor c1=R/vs2. Note that this is possible irrespective whether this point is part of a square or non square resistance curve. Using the wake fraction w this can also be written as (equation (3)): 2

 v  R = c1 ⋅  A   1 − w 

,

with thrust deduction t and number of propellers k p follows (equation 2): T =

c1 ⋅ v A 2

R k p ⋅ (1 − t )

=

k p ⋅ (1 − t ) ⋅ (1 − w )

2

= c8 ⋅ v A2 .

(9)

The required thrust coefficient for this ship at speed v s is then (equations (5) and (7)): c8 ⋅ v A

K T ,ship

=

K T ,ship

= c7 ⋅ J 2

ρ

2

⋅n ⋅ D 2 p

4

=

c8 ρ

⋅ D

2

⋅

v A 2 p

n

2

⋅D

2

=

c8

⋅

ρ D

2

⋅ J 2

or:

(10)

29

Matching propulsion engine with propulsor Design ship speed v s Effective towing power PE Factor c1 Wake fraction w Thrust deduction t Relative rotative efficiency ηR Propeller diameter D Advance ratio J Thrust coefficient K T Torque coefficient K Q Propeller open water efficiency ηO Propeller power Pp,load (one propeller) Propeller speed Engine brake power PB,load (one engine) Engine rpm Engine MCR Engine MCR rpm Gear ratio Transmission efficiency ηTR Sea water density ρ

14.40m/s (28 knots) 16 000kW 5.36x103 0.04 0.06 0.99 3.8m 0.992 0.206 0.0457 0.710 11 624kW 3.67rev/s (220rpm) 6115kW 979rpm 6500kW 1000rpm 4.45 0.95 1025kg/m3

Table 1: Design data of example ship

This square KT,ship curve can be plotted in the open water diagram, as shown in Fig 11. The point of intersection leads to the operational point of the propeller (J, KT) and also the torque coefficient and open water efficiency can be determined. With the advance ratio J and wake fraction w the propeller speed can be determined as a function of ship speed (equations (7) and (3)):

  ⇒ n = v A = (1 − w) ⋅ v n p ⋅ D  p J ⋅ D J ⋅ D s v A = vs ⋅ (1 − w )   J =

v A

(11)

With the torque coefficient K Q and relative rotative efficiency ηR the propeller load can be determined (equations (6) and (4)): K Q

=

Q ρ

⋅ n p 2 ⋅ D 5

=

5 ⋅ M p ρ ⋅ D → = ⋅ KQ ⋅ n p 2 M p 2 5 ρ ⋅ n p ⋅ D η R

η R

With the transmission efficiency and ratio the P p,np point can be converted to an engine brake power/speed P B,ne point (equation (8)). This procedure can be repeated for a number of points on the ship resistance curve leading to a brake power load curve which can be plotted in the operational envelope. Note that in case of a square resistance curve and constant wake fraction and thrust deduction this calculation needs to be done only once. In this case the propeller has a constant operational point (J, KT), which leads to the observation that ship speed and propeller rotational speed are then proportional (equation (11)).

30

ηO

1,00 10 K Q

10 K Q 0,80 K T 0,60 K T 0,40

O

0,20 Ship 0,00 0,0

0,2

0,4

0,6

0,8 1,0

1,2

1,4

1,6

Advance ratio

Fig 11: Intersection of ship K T curve with propeller K T curve leading to operational point of the propeller

OFF-DESIGN CONDITIONS The propulsion plant will often operate under off-design conditions. It is necessary to determine these and check whether the plant still functions satisfactorily. The main off-design conditions are:  The hull resistance has changed due to hull fouling, change of displacement or sea state or sailing in restricted water depth  The resistance that needs to be overcome by a propeller also changes when towing another ship or dragging equipment  Change of number of driven shafts  Change of pitch in case of a CP propeller  Change of number of driving engines  Connection or disconnection of Power Take Offs (PTOs)  Change of gear ratio of the gearbox. When investigating off-design conditions, it is essential to distinguish between two categories: 1. Off-design conditions that influence the operational point of the propeller. They should be studied by using the open water diagram. As a rule of thumb, all off-design conditions that are a result of changes that take place outside the ship’s hull belong to this category: for example change of resistance, change of driven shafts and change of propeller pitch. 2. Off-design conditions that do not change the operational point of the propeller, so they can be solved without the open water diagrams. As a rule of thumb, the off-design conditions that are the result of a change inside the ship’s hull belong to this category: for example change of number of connected engines, change of power to PTO and change of gear ratio. Two examples of calculation of the off-design behaviour will be given. The basis is a CODAD propulsion plant according Fig 4. The plant consists of two identical shaft lines; each driven by two identical turbo charged diesel engines. To simplify the example a number of assumptions have been made:  the ship has a square resistance curve  the propellers are of the fixed pitch type  wake fraction, thrust deduction, relative rotative efficiency and transmission efficiency are constant.


No. A7 2005


ηO

10 K Q

10 K Q 0.80 K T

7000

Single shaft operation Design condition

1.00

0.60 K T η

0.40

6000

W k n i 5000 r e w o 4000 P r e w o p 3000 e n i g n 2000 E

0.20 Ship

24 k nots

20 k nots

1000

16 k nots

0.00 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 400

Advance ratio J

500

600

700

800

900

1000

Engine speed in r pm

Fig 12: Open water diagram with K T,ship curves for design condition and single shaft operation The open water diagram of the propellers is according to Fig 11. The shown KT,ship-curve corresponds with the design service condition of the ship. In that condition both s hafts and all four engines are in operation. Some data for this design condition are shown in Table 1.

Single shaft operation 2 engines/shaft Design condition

Fig 13: Diesel engine operational envelope with design condition load curve and single shaft operation load curve 7000

Change of number of driving shafts In this off-design condition only one shaft line is in operation and is driven by two engines. The other shaft is not driven but free to rotate: a trailing propeller. This is an off-design condition, that has influence on the operational point of the propeller (in J,KT-terms). Consequently it can only be solved by use of the propeller open water diagram. The trailing propeller means that an additional resistance is created. This additional resistance is assumed to be 7.5% of the normal ship resistance. The factor c 1 has increases with a factor 1.075 and changes from 5.36x10 3 to 5.76x103. The resistance of the ship increased by the contribution of the trailing propeller has now to be overcome by the thrust of only one operating propeller. Originally that propeller overcame half ship resistance (two propellers operating), now it has to overcome 1.075 times the original resistance. So the thrust to be delivered by the operating propeller increases with a factor 2.15. This means that also the factor c 7 of the KT,ship-curve will increase with a factor 2.15 (equation (10)). The new KT,ship curve can be plotted in the open water diagram and leads to a new operational point of the operating propeller (Fig12): J=0.808, K T=0.293, KQ=0.0624 and ηO=0.605. With this new data the propeller power and speed as well as engine brake power and speed can be determined, as described before. Assuming that the design speed of 28 knots will be maintained, this leads to: Pp,load=29 383kW, np=270 rpm, PB,load=15 465kW (for one engine) and ne=1201rpm. The calculated operational point clearly lies outside of the operational envelope of the engine, as was to be expected, simply by lack of power. It is not possible in single shaft operation to maintain the design speed. Plotting the new engine load curve in the operational envelope shows the maximum power that may be achieved (Fig 13)

No. A7 2005


6000 5000

W k i 4000 r e w o 3000 e i g E 2000 n

24 k nots

p n

20 k nots

n

16 k nots

1000 0 0

1000

2000

3000

4000

5000

Engine speed in r pm Single shaft o peration 2 engines/shaft Design condition

Fig 14: Gas turbine operational envelope with design condition load curve and single shaft operation load curve The engine speed which can be achieved proves to be in the order of ne=875rpm and the developed power is then PB=5980kW, on a limit line of the envelope. The corresponding ship speed is 20.4 knots. This seems quite acceptable but it is questionable whether the margin of the new load curve in the operational envelope leaves sufficient room for acceleration of the ship or increased resistance due to a heavy sea way. Most probably it would be wise to adopt a controllable pitch propeller which allows pitch reduction in single shaft operation. This will shift the load curve in the operational envelope to a more attractive location. For a detailed analysis see reference.1

31


The situation would have been quite different in case the propulsion plant used gas turbines instead of diesel engines. Fig 14 shows the operational envelope of a gas turbine again with the design load curve and the single shaft operation load curve. Now there is in single shaft operation sufficient room for acceleration and increased resistance. A fixed pitch propeller is then a good choice.

7000 6000

Wk 5000 i

n

re

w 4000 o

p

e

24 k nots

ig 3000

n

E

Change of number of driving engines In this off-design condition both shafts are in operation but each shaft is driven by only one engine. This is an offdesign condition that has no influence on the operational point of the propeller (in J,K T-terms). Consequently it can be solved without use of the propeller open water diagram. The propeller load curve (in P p,load,n p-terms) has not changed. But instead of two engines this load has to be carried by one engine. This means that at the same engine speed the required brake power for the operating engine has doubled. Fig 15 shows what happens. This situation proves to be fully unacceptable. The load curve lies completely out of the envelope. A good solution might be to adopt a gearbox with two different gear ratios or again a controllable pitch propeller. For a gas turbine with a much wider envelope, the load curve would still be acceptable.

n

2000

CONCLUSIONS

20 k nots

1000 16 k nots 0 400

500

600

700

800

900

1000

Engine speed in r pm Twin shaft operation 1 engine/shaft

Design condition 2 engines/shaft

Proper matching of propulsion engine with propulsor is essential to obtain acceptable behavior of the ship and its propulsion system. The selected types of machinery have a dominating influence on the possibilities to get a good match. To evaluate design and off-design conditions adequately, both the naval architectural as well as the marine engineering aspects should be understood.

REFERENCES Fig 15: Diesel engine operational envelope with design condition load curve (two engines per shaft) and load curve with one engine operating per shaft

32

1. KleinWoud J and Stapersma D. Design of Propulsion and Electric Power Generation Systems , IMarEST, 2003. ISBN 1-902536-47-9


No. A7 2005

Matching Propulsion Engine With Propulsor

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