Lecture 14 - Self Propulsion Test

Rod Sampson - School of Marine Science and Technology - 15th April 2008

Self Propulsion Tests

Resistance & Propulsion (1)MAR 2010

Introduction


Objectives of Self propulsion test:

1. To confirm early ship power & speed requirements and to check the propulsor is able to absorb the

delivered power

2. To derive values of propulsion factors ( )w, t, R

Test procedure


Towed resistance (R)MotorDynamometer

T - R

T, Q

T

V

Model is mounted on the carriage similar to a

conventional calm water test. However a propulsion system

is also added

n

Test procedures



T - R

T, Q

T

V

1. Number of sets of runs in each of which the model hull speed is fixed at a speed corresponding to the ship speed

VmVs

Test procedures



T - R

T, Q

T

V

2. In each set the propeller speed (n) is varied from a low value (TR model over propelled).

(T = Thrust, R = Resistance)

Test procedures



T - R

T, Q

T

V

3. During each run measurements are taken for

& carriage dynamometer force T - RVm, nm, Tm, Qm,

Test Procedures


For extrapolation of the results to the full scale prediction we refer to BTTP-1965 procedures as

follows:

Model test results are analysed in terms of:

KTP , KQP , C TR

Self propulsion test


Mod

el s

elf p

ropu

lsio

n po

int

P/D = 0.8Ship service self propulsion point

Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

C TR

1.2 (1 + x)F C s C m

C TRC s C m

(1 + x)F C s C m

JP0

+

-

For fixed Vm

10KQP10KQPKTP



Ship

sel

f pro

puls

ion

poin

t

Ship service self propulsion point

Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

KQPC TR

1.2 (1 + x)F C s C m

C TRC s C m

(1 + x)F C s C m

JP0

+

-

The residual drag coefficients ( ) of the ship and model will be the same but the frictional will not. Therefore a skin friction correction must

be applied to C TR

CR



Ship

sel

f pro

puls

ion

poin

t


Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

KQPC TR

1.2 (1 + x)F C s C m

C TRC s C m

JP0

+

-

(i.e. shift 0-0 line down)SFC = cs cm

The first shift corrects for the skin friction coefficient:



Ship

sel

f pro

puls

ion

poin

t


Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

KQPC TR

1.2 (1 + x)F C s C m

C TR

(1 + x)F C s C m

JP0

+

-

cs trial = (1 + x)f csFor trial condition the power prediction factor is also included (2nd shift)

(1 + x)f cs cm



Ship

sel

f pro

puls

ion

poin

t


Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

KQPC TR

1.2 (1 + x)F C s C m

C TR

JP0

+

-

1.2(1 + x)f cs cmFor service the power margin of 1.2 is included (3rd shift), hence:



Ship

sel

f pro

puls

ion

poin

t


Ship

sel

f pro

puls

ion

poin

t (T

rial

)

Ship

sel

f pro

puls

ion

poin

t (S

tand

ard

X=

0)

KTP

KQPC TR

1.2 (1 + x)F C s C m

C TRC s C m

(1 + x)F C s C m

JP0

+

-

Then at ship trial self propulsion point we read off:

Jp KQp KTp



Then model rps at the self propulsion point:

nm =V

Jp Dm




define a resistance coefficient:

kR =Rm

n2mD4m

Where is the resistance of the ship reduced to model scale and calculated

from ( )

Rm

c



Then propulsive efficiency D

D =PePD

=RmVm2pinmQm

=n2mD

4mkRVm

2pinm n2m D5mKQp



Then for each speed calculate:

PD = (1 + x)PED

D =Jp2pi

=kRKQp

Jp =Vm

nmDmFinally, given that:

(Self propulsion test)(towing tank test)



Confirmation of the propeller speed including the scale effect due to the propeller wake

(rpm)Ns = 60 nm

DmDs

Ns = k2 Nstandard

k2 = 1.265 0.1(1 + x)F 0.2CB(according to BTTP-65)



Finally plot the predicted values of PD, Ns vs Vs

PD

Ns

NsPD

PDDesign

VsPredicted trial speed



The previous method derived the ship power and speed requirements.

The following is to derive . w, t,& R

Tests require: Thrust and torque data of the stock propellers used Equivalent open water propeller curve



From the open water data of the equivalent propeller select one of 2 methods, either:

Same torque at the propulsion test rpm, this is known as Torque identity analysis

Same thrust at the propulsion test rpm, this is known as thrust identity analysis



0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

Input from S-P tests for Torque identity analysis

Input from S-P tests for Thrust identity analysis

oq

ot

KQ ot

KQ p

KT oqKT ot

KT p

Jo q Jo t


Thrust identity analysis

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

ot

KQ ot

KQ p

KT otKT p

Jo t Jp



0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

ot

KQ ot

KQ p

KT otKT p

Jo t Jp

ht =1 t1 wt Rt =

KqotKqp

wt =Jp Jot

Jp



0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

ot

KQ ot

KQ p

KT otKT p

Jo t Jp

ot =Jot2pi KtpKqot


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

oq

KQ p

KT oq KT p

Jo q

wq =Jp Joq

Jpt =

Ktp KRKtp

hq =1 t1 wq

Torque identity analysis


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.1 0.2 0.3 0.4 0.5 0.6 0.65 0.7 0.8

KT 10 KQ Eta_0

Advance coefficient

oq

KQ p

KT oq KT p

Jo q

Torque identity analysis

Rq =KtpKToq

oq =Joq2pi

KtoqKqp



In evaluation of in the thrust identity:R

o =PtoPDo

B =PtbPDb

R =Bo=PTbPDb

PDoPTo



In torque identity PDb = PDo

Rq =PTbPTo

=KtpKToq



In thrust identity PDb = PDo

PTb = PTo

Rt =PDoPD

=KqotKqp



D = hq oq Rq = ht ot Rt

But

The above check may be applied to the derived quantities for both analysis procedures which should

give similar results.

End of Presentation


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Lecture 14 - Self Propulsion Test

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