Lecture 14 - Self Propulsion Test

Resistance & Propulsion (1) MAR 2010

Self Propul Propulsio sion n Test estss

Introduction Objectives of Self propulsion test: 1. To confirm c onfirm early ship power & spee speed d requirement requirementss and to check the propulsor is able to absorb the delivered power 2. To deri derive ve val values ues of propulsi propulsion on fac factors tors (w, t,

ηR

)

Introduction Objectives of Self propulsion test: 1. To confirm c onfirm early ship power & spee speed d requirement requirementss and to check the propulsor is able to absorb the delivered power 2. To deri derive ve val values ues of propulsi propulsion on fac factors tors (w, t,

ηR

)

Test procedure Model is mounted on the carriage similar to a conventional calm water test. However a propulsion system is also added T-R T, Q

V

n

T Dynamometer

Motor

Towed resistance (R)

Test procedures T-R

V

η

T, Q T Dynamometer

1.

Motor


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

s

Test procedures T-R T, Q

V

η

T Dynamometer

2.

Motor


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

V

η

T Dynamometer

3.

Motor


During each run measurements are taken for V , n , T , Q , & carriage dynamometer m

m

m

force T - R

m

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:

K T P , K QP , C

TR

For fixed

Self propulsion test

V m

10

QP

10K QP

C

K T

K T P

P

C

C

s

− C

T −R

t n i o p n o i s l u p o r p f l e s l e d o M

T −R

m

1.2 (1 + x)F

C

s

) n 0 o i = s X l u d p r o a r d p n f l a t e S s ( p t i n h i S o p

− C m

n o i s ) l u l a p i r o T r ( p t f l i n e o s p p i h S

0

+ J P

-

(1 + x)F

C

s

− C

m

Ship service self propulsion point

P/D = 0.8

Self propulsion test K QP C

T −R

K T P

C

C

s

− C

T −R

m

1.2 (1 + x)F

C

s

− C

n o i s l u p o t n r i p o f l p e s p i h S

n o d i s r l a u d p n ) o a 0 r t p S = ( f l t X e n s i p o i p h S

m


+ 0

J P -

(1 + x)F

C

s

− C

m


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


T −R

K T P

C

C

s

− C

T −R

m

1.2 (1 + x)F

C

s

− C



m


+ 0

J P -


The first shift corrects for the skin friction coefficient: SF C =

c c  − s

m

(i.e. shift 0-0 line down)


T −R

K T P

C

1.2 (1 + x)F

C

T −R

s

− C



m


+ 0

J P -

(1 + x)F

C

s

− C


m

For trial condition the power prediction factor is also included (2nd shift)

cs 

trial =

cs (1 + x)f 

cs− cm (1 + x)f 


T −R

K T P

C

1.2 (1 + x)F

C

s

− C

T −R



m


+ 0

J P -


For service the power margin of 1.2 is included (3rd shift), hence:

cs− cm 1.2(1 + x)f 

Self propulsion test Then at ship trial self propulsion point we read off: J p

K Qp

K T p

K QP C

T −R

K T P

C

C

s

− C

n o i s l u p t o n r i p o f l p e s p i h S

T −R

m

1.2 (1 + x)F

C

s

− C


m

n o i s ) l u l a p i r o T r ( p t f l i n e s o p p i h S

+ 0

J P -

(1 + x)F

C

s

− C

m



Then model rps at the self propulsion point:

nm

V =

J p Dm


define a resistance coefficient:

kR

Rm =

4 D ρ n2 m m

Where R is the resistance of the ship reduced to model scale and calculated c ) from (  m


Then propulsive efficiency

ηD =

P e P D

=

Rm V m 2π nm Qm

2

=

D

4

ρnm Dm kR V m

2π nm

×

ρn2 m

×

5 Dm K Qp

Self propulsion test Finally, given that:

ηD =

J p 2π

J p

=

V m =

n m Dm

kR K Qp

(Self propulsion test)

Then for each speed calculate: P D =

(1 + x)

P E ηD

(towing tank test)

Self propulsion test Confirmation of the propeller speed including the scale effect due to the propeller wake

(rpm)N = 60 n s

m

m

D

s

N s

k2

=

k2 N standard

= 1.265 − 0.1(1 + x)F − 0.2C B (according to BTTP-65)

Self propulsion test Finally plot the predicted values of P D

D

,

s

vs

s

N s N s

Design

D

P D V s Predicted trial speed

Self propulsion test The previous method derived the ship power and speed requirements. The following is to derive

w, t, &

ηR

.

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

Self propulsion test KT

0.7

10 KQ

Eta_0

ot

0.6

ηoq

0.5 0.4

Input from S-P tests for Torque identity analysis

Qp Q ot

0.3 0.2

Input from S-P tests for Thrust identity analysis

K T p

T oq T ot

0.1 J o q

0 0.1

0.2

0.3

J o t 0.4

0.5

Advance coefficient

0.6

0.65

0.7

0.8

Thrust identity analysis KT

0.7

10 KQ

Eta_0

ot

0.6 0.5 0.4

K Q p K Q ot

0.3

K T p

0.2

K T

ot

0.1 J o t

0 0.1

0.2

0.3

0.4

J p

0.5


0.6

0.65

0.7

0.8


0.7

10 KQ

Eta_0

ηot

0.6 0.5 0.4

Qp Q ot

0.3

T p

0.2

K T

ot

0.1 J o t

0 0.1

0.2

0.3

0.4

p

0.5

0.6

0.65

0.7

0.8


wt

J p =

− J ot J p

ηht =

1

−t 1 − wt

ηRt

qot =

K qp


0.7

10 KQ

Eta_0

ηot

0.6 0.5 0.4

Qp Q ot

0.3

T p

0.2

K T

ot

0.1 J o t

0 0.1

0.2

0.3

0.4

p

0.5

0.6


ηot =

J ot 2π

×

tp

K qot

0.65

0.7

0.8

Torque identity analysis KT

0.7

10 KQ

Eta_0

0.6 ηoq

0.5 0.4

K Q p

0.3 K T p

T oq

0.2 0.1

J o q

0 0.1

0.2

0.3

0.4

0.5

0.6

0.65

0.7

0.8


wq

p =

− oq J p

t

K tp =

− K R

K tp

ηhq =

−t 1 − wq

Torque identity analysis KT

0.7

10 KQ

Eta_0

0.6 ηoq

0.5 0.4

K Q p

0.3 K T p

T oq

0.2 0.1

J o q

0 0.1

0.2

0.3

0.4

0.5

0.6

0.65

0.7


ηRq

K tp =

K T oq

ηoq =

J oq 2π

×

K toq K qp

0.8


In evaluation of

ηo

R

in the thrust identity:

P to =

ηR

ηB

P Do

P T b

ηB =

=

ηo

P Db

P tb =

×

P Db

P Do P T o


In torque identity P Db

ηRq

P T b =

P T o

=

P Do

K tp =

K T oq


In thrust identity

ηRt

P Db

=

P Do

P T b

=

P T o

P Do =

P D

K qot =

K qp

Self propulsion test But ηD

=

ηhq ηoq ηRq

=

ηht ηot ηRt

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

Lecture 14 - Self Propulsion Test

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