Trial results of the tug boats equipped with Voith-Schneider propellers

Trial Results of the Tug-Boats Equipped

with Voith-Schneider Propellers

By

ShOichi NAKAMURA, Hitoshi Fuji and Akira NAGAYAMA

Reprinted from

TECHNOLOGY REPORTS OF THE OSAKA UNIVERSITY Vol. 11 No. 470 Faculty of Engineering Osaka University Osaka, Japan 1961

DeLi

Lab. v.

Scheepsbolrakundi.,

NO. 470

(Received June 23. 1961)

Trial Results of the Tug-Boats Equipped with

Voith-Schneider Propellers

By

ShOichi NAKAMURA, Hitoshi Fujii* and Akira NAGAYAMA** (Department of Naval Architecture)

Abstract

In this report are described the results of speed trial at free running and

bollard pull trial of five pusher type tug-boats equipped with twin

Voith-Schneider propellers (V.S.P.), which were built at Osaka Shipbuilding Co. In trials, shaft horse power, towing force and displacement of picth indicator

of V.S.P. etc. were measured. Furthermore, resistance tests were carried out on these ship forms at the experimental tank of Osaka University.

From these results, propulsion factors at speed trial and towing force per 100 SHP at bollard pull trial etc. were analysed using the characteristic curves

calculated by Taniguchi's approximate solution of V.S.P..

1. Introduction

The boat equipped with Voith-Schneider propeller (V.S.P.) displays excellent

manoeuvrability. It is, however, considered that the propulsive efficiency of V.S.P.

is not so good as that of the ordinary screw propeller for the following reasons: The stern shape with the large propelling gear affects the propulsive perfor-mance.

There is a considerable loss of power in the complicated propelling gear mechanism.

In designing any tug-boat equipped with V.S.P. we must take those reasons into consideration, but there have been little practical data available.

Since the end of the War, Osaka Shipbuilding Co., Ltd. has constructed several tug-boats equipped with V.S.P.. The measurements of the S.H.P. and towing force were carried out for five boats on the speed and bollard pull trials. Moreover, to calculate E.H.P. the resistance tests were performed with the models for each boat at the experimental tank of Osaka University. The open propeller efficiency was

estimated both by means of Taniguchi's approximate solution of V.S.P. and of

* The Mitsubishi Heavy-Industries, Reorganized. ** Osaka Shipbuilding Co.

269

270 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers

propeller test results given at the Mitsubishi Nagasaki Experimental Tank. We should like to describe the estimated data of the propulsive quality and towing

force from the above-mentioned methods.

Machinery Part 1 Length overall (m) Length between (11-0 perpendiculars Breadth moulded (m) bepth moulded (M)

Designed load draft (m) Gross tonnage (T) Full load displacement (t) CB designed CP designed Co designed 133. GO 220.44 28. 25. 3. 0. 6.80 2.20 0.502 0.583 296 00 30 853 131.68 224.19 146.87 258.83 29. 26. 3, 2. 0 7.20 0.545 0.612 32 00 40 25 147. 32. 258.79 890, 31.75 28, 25 8.20 3. 80 2. 70 210,. 03 357.88 0. 557' 0.628' 0.887

Main engine type

Number of set Niigata L6F25 Diesel Ikegai 5MSD

Diesel Ikegai 7MSD Diesel

Hanshin, 26VSH Diesel Output ,(M.C.R.) (PS) 510, 500 68.0 830 R.P.M. ( ') 600 600 600, 400 Diameter of inter-mediate shaft (mm) 110 120 145

Coupling Karuderis_flexible

. Kawasaki HCO4 hydraulic 'Mitsubishi 'TC 125 hydraulic Mitsubishi TC 140 hydraulic Propeller

Type X Number 18E/115 x 2 20E/125 x 2 24E/12&X2

Diameter of orbital

circle (n) L800 2000. - 2.400

Number of blade 4 5 6

Table 1. Principal particulars.

Name of boat DAI TO_MARU ASAHI_{MARU MARU}ASOU WAKAMIYA_MARU INABA_MARU Owner

Port where on duty

Date of delivery Daito Unyu Yok °llama Dec. 11, '57 Tokyo Kisen Yokohama Nov. 6 '58 Mie Yahata Seitetsu _Prefecture

Tobata Yokkaichi

Aug. 15. '58 Sept. 25, '58 'Aug. 31,

Hull Part

Blade length 1.156 1.250 L 247

Chord length at _Km),,

blade root 0.485 0.485 0. 472

Reduction gear ratio 1811000 1/6 1/5,

'59

S. NAKAMURA. H. FUJII and A. NAGAYAMA 271

2.

Particulars of Each Boat

All is pusher type tug-boats, and the principal particulars of each boat are

shown in Table 1.

3. Measurement at Trials

3-1. Trial Conditions

Table 2 shows the conditions of the speed and bollard pull trials for each

boat.

Bollard Pull Trial Specific gravity of sea

water 1.013 1.011 1.010 1.010 1.007 Draft fore (m) 2.414 2.342 1.865 2.261 2.405 aft (m) 2. 354 2.437 2.521 2.536 2. 772 mean (m) 2.381 2.390 2.193 2.399 2.589 Trim (m) 0.060 F 0.095 A 0.656 A 0.275 A 0.367 A Displacement (t) 218.3 221.7 236.13 263.61 I, 337.08 Date Weather Wind velocity (m s) Sea condition Dec. 8. '57 Cloudy 3. 1 Calm Nov. 3, '58 Aug. 8, '58 Cloudy Fine 0 3 Calm Calm Sept. 18. '58 Fine 4.5 Calm Aug. 25. '59 Fine 4 Calm Specific gravity of sea

water 1.013 1.015 1.020 1.010 1.007 Draft fore (m) 2.430 2.290 2.165 2. 160 2.067 aft (m) 2.360 2.410 2.400 2.495 2.819 mean (m) 2.395 2.350 2.283 2.328 2.443 Trim (m) 0.070 F O. 120 A 0.235 A O. 335 A 0.752 A Displacement (t) 219.5 216.8 240.2 252.0 315.4

Table 2. Trial conditions.

DA] TO ASAHI ASOU WAKAMIYA

Name of boat _{M ARU MARU MARU} MARU INABAMARU

Speed Trial (condition in port)

Date Dec. 4. '57 Oct. 22. '58 Aug. 5. '58 Sept. 15, '58 I Aug. 22, '59

Weather Cloudy Fine Fine Fine Cloudy

Wind velocity (m s) 0 1.0 1.0 1.0

272 _{Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers}

3-2. Measured Item

(a) Shaft torque

As is shown in Fig. 1, two rings were attached to the intermediate shaft, and the relative shift between the rings was measured electrically with a torsion meter of differential transformer type. The torque, therefore, is given by the following

relation. 7rD4G Q= s, 32 LR where Q =torque ( kg-mm),

D =diameter of intermediate shaft (mm),

G =- modulus of rigidity of intermediate shaft =8,300 kg/mm,

L =gage length between ring centre points= 150 mm,

R, =distance between intermediate shaft centre and movable iron piece centre in torsion meter (mm),

S =displacement of movable iron piece.

Brush Excite coil Search coil

Slip ring Torsion meter Fig. 1. Torsion meter.

Number of Revolution of Shaft

The measurement was carried out with the electric contact attached to the

same location as the slip rings of the torsion meter.

Speed

The speed result was obtained from the speed trial between mile posts out of

Kobe Port. (Distance: 1,415 m, Sea depth: about 8 m).

Reading of Pitch Indicator

The displacement of pitch indicator was measured at the control rod top of the

driving mechanism.

Towing Force

At the towing force trials, the boat was moored with a rope through a test

piece to which was attached a wire strain gage. The elongation of the test piece

was measured with the strain meter and the towing force was obtained through

the calibration curve from a preparatory tension test. As presented in Fig. 2, the test piece was protected against rope torsion.

1500

1000

500

S. NAKAMURA. H. FUJI! and A. NAGAYAMA 273

Fig. 2. Tension meter.

3-3. Measurement Results

Figs. 3-5 show the measurement results at speed trials. The shaft horse power 550 13 600 550 6 7 8 9 10 11 Ship speed V (kt)

Fig. 3. Results of speed trial of DAITO MARU and ASAHI MARU.

_ E E `.-i00 -. t-2 50 DAITO MARU V.S.P. 18E/11 5

(4 blades) - -- ASAHI MARU

0

1111fti.

NS

pv.

IA

, ...

,

INI

/

/

274 'Trial Results of the Tug-Boats Equipped with Voith-Schneder Propelilers cf) 500 1500 1000 too 0 13 1-4 8 9 101 1I 12 Ship speed V,; (kt)

Fig. 5.. Results of speed trial of INABA MARUl.

0

6 'I' 91 10

Shiip speed T e 0:0

Fig., 4.. Results of speed trial of ASOU MARU and WAKAMIYA MARU.

450

400 CO

350

0

shows the total value of both side shafts, while the number of revolution and

displacement of pitch indicator the average. At speed trials, as is shown in Table 2, it was almost windless and the correction for wind effect, therefore, was neglected. All of the speed, shaft horse power, number of revolution and displacement of pitch indicator are presented on the average value measured in each group of one double run, Furthermore, Fig, 6 shows the results at bollard pull trials.

10 , 4L 5 , V.S.P. 20E/I25 (5 blades)

-A SOu MARL!

WAItAM iYA MARL]

0.

--- - - - , - As ....,..., No I 61 . 1 1 , \\9/' c0

..-,

I ...,

V'S P. 24E/125, IINABA MA911 (,6blades) mo t.. . -. 1 .,°-3'8 1 50 I II 1500 1000

111

7

C

0. 15

r=4 5

0

S. NAKAMURA. H. FUJII and A. NAGAYAMA 275

SHP

Fig. 6. Results of bollard-pull trials.

4. Resistance Test

Resistance tests were carried out with models at the experimental tank of

Osaka University. Each model is fitted with 0.8 mm trip wire at 9 station for

turbulent stimulation. The principal items at test conditions are given in Table 3. Furthermore, the test of INABA MARU was carried out on the designed full load

condition, changing the trim. This results show that resistance will increase in

Table 3. Conditions of resistance tests.

600 550 500

,

400 -9..-18 IIHIIIIIIIIIIrllrilfrllrill°:.''4

,

--'

'

1-1.5

IOW

,-. 7 ix ,-- - - of,,,,,,W1I I I li i<,1..., 66,,,,, to, < Z 4 CO II -, ---< Z -...,-_-.., 1.0 , /

- - -.- - - DA ITO MARU -I-

--: -- -a- -- A, SAH1 MARU MARU

--,-- ASCU

--4.--- WAHAMIYAMARU

-

-

INABA MARU Name of boat Condition LPP (m) B (m) di, (m) dm-(m) dA (m) Boat 25.00 6.80 2.20 DAITO

MARU Full load Model 1.6667 0.4523 0.1467

DAITO Boat 25.00 6.80 2.414 2.384 2.354

& _{MARU trial Model 1.6667 0.4523}

0.1609 0.1589 0.1569 ASAHI

MARU ASAHI_{MARU trial} Boat_{Model 1.6667}25.00 _0.45236.80 _0.15612.342 2.390_0.1593 2.437_0.1625

ASOU _{Boat 26.00 7.20 2.25}

MARU Full load Model 1.6667 0.4615 _0.1442

&

WAKAMIYA WAKAMIYA Boat 26.00 7.20 2.261 2.399 2.536

MARU MARU trial Model 1.6667 0.4615 0.1449 0.1538 0.1625 INABA Full load BoatModel

28.25

1.600 0.46458.20 0.15292.70

MARU _Trial Boat

Model 28.25 1.600 8.20 0.4645 2.405 0.1362 2.589 0.1466 2.772 0.1570 500 1000 1500 10

-/ 0 I I ' I 0

10.90

.z

0.05

-276 Trial Results 'of, the Tug-Boats Equipped with Voith-Schneider Propellers

Table 3 Continued

proportion to trim by Stern.. Therefore, for these, kinds of boats With the extremely

flat stern for fitting the V.S.P., large trim by stern isdisadvantageous in respect

fesistance.

In the test results, effect of tank cross section Was cortected by blockage

method and shown in Fig. 7, as residual resistance coefficient, CR. Effective horse power of trial conditions, calculated upon those results, is given in Figs. 3--5. In the calculation of frictional resistance, Schoenherr's formula was used both. for the

models and for the boats, and tICF=0.0004 was added as roughness allowance for the boats. 010 0 6765 Name of boat Condition Trim (m) A I

,

1

r

_{-B CP S} (m2) DAITO 1 Full load. 1 Boat _a 194.5 t 0.502 0..585 225.5_1.002 NIARU Model 56.23 kg & DAITO 1 MARU trial 1 Boat Model 0_60 F 0_0040 F 218.3 t 63.85 kg 0 532 0)614 236.5 1.051 ASAHI _{Boat G. 095 A 221.7 t} 227.2

MARU ASAHI_{MARU trial} 1

Model 1 0.0064 A 64.97 kg 0.533 0.614 1.010 ASOU

MARU i Full load BoatModel 0

237.7 t 61.08 kg 0: 545 0.612 235.4 0.967 & WAKAMIYA MARU WAKAMIYA MARU trial BoatModel

0.-275 A 0..0176 A I 263.61 t 68.75 kg 0.566 O. 631 246.7 1.014

INABA Full load

Boat Model 0 , 359.5 t 64.84 kg 0_557 C.628 301.8 0.968

MARU _'trial Boat

Model 0.367 A 0.0208 A 337.08 t 60.80 kg 0.540 C. 613 294.2 0.944 . '.2 <I o n. 1-la 10 -005 I -5 Fu I I L406 r. ster., t 4\ e,'. .,.';' _,,,,,ii N$L'>''' . / .t. tr / a A 04171 0 0.4 rn bow 2 Trio 1 Oft

,.--...42Ialgaill

Fun Load

13W. 1

e

l'5i /

I

i I Pr 4 3 /

/

"a 000i,, Tr . I

-

Mill

F ut I Load DAI,0 MPRu TY ;01 ASAH I MAR Tr ' o I

I---- ---

, i , 1 0.0 0.15 0.20 0.25 0130 0.35 0.40 Frounde's No. VI Lg

Fig. 7. Residuary resistance coefficient curves.. of

/

--S. NAKAMURA, H. FUJII and A. NAGAYAMA 277

5.

Analysis of Trial Results

5-1. Calculation of Eccentricity

Fig. 8 gives the outline of the driving mechanism of V.S.P.. In order to make

clear the change of

the attack

angle, a part of the mechanism is

illustrated in Fig. 9.

When the guide plate is shifted

by y perpendicularly to the boat's running direction, the cross head

is also shifted by y and the arm

Ri of the driving link turns by

giving the rotation of

to the

arm R2.

The attack

angle of

blade, therefore, changes by 0.

As to

the relation between

the turning angle on the

orbit,

0(Z020X) and 1/r, the following

formula is obtained.

Fig. 9.

C) Control rod C) Guide plate

C) Cross head C) Driving link C) Blade

278 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers

cos(0-1-0)

tan ik--=

(a/y) sin(C+e)

where 6=angle between arm A and 002,

a =distance between cross head of arm A and Oi , and the following relation can be obtained between ik and y.

o=132+tan--1

cos(13''11)(L/Rt)

sin(3iV1)

si

(L/ R2) cos Oi - _{Ri) cos 02+ cos(01- R2)- - (LI R2)cos(13i-*)}

n-1

,./(L/Ri)2+1-(2LIR)cos(1-*)

where i=-angle between arm R, and 0102, at Y=0,

02=angle between arm R2 and 0,02, at 0=0, L =distance between Oi and 02.

The relation between the eccentricity e(ON/R) and the change of the attack

angle of blade y, is as follows:

1

cos0 coty+sin0

From (1), (2), (3), the relation The pitch indicator of the

propeller is attached to the top of the control rod and it is easy

to get the relation between y and the reading of pitch

indi-cator 8. The relation between

e and a, therefore, will be given. The driving system of the

orthodox V.S.P. is arranged as

0-0, and the blade is attached

at the location of 01.

There-fore, the change of the attack

angle of blade is ..tk, and e is

always constant, independent of

0.

In the actual

V.S.P. the

system is just

as the above

illustration. For this case, Fig.

between y and e will be given as a function of_0.

50 40 30 20 10 0 30 60 (1) -10 -co -60 -30 0 (deg)

Fig. 10. Relation between change of attack angle of blade and turning angle on the orbit 0.

co

10 gives the curves showing the relation between y and C for the given y as an

example of the five blade 20E/125 type. From Fig. 10 and the formula (3), e is

obtained as is shown in Fig. 11. When y is small, e is almost constant to 0, but e V.S.P. 20E/125 (5 b odes)

A

4

AAR

Pir

illin

1111/1

WAIri

/

_all

\

0

" ^

- -0U 'JO QI

,0 (deg)

Fig. Ill. Relation between eccentricity e and turning angle of blade on the oi-bit

5-2. Characteristic Curves

Each blade. of V.S.P. advances revolving in the trochoidil way, and thrust

changes by B. So, the induced velocity field is very complicated as compared with

that of the ordinary screw propeller and has not yet been completely analyzed. In the Mitsubishi Nagasaki experimental tank, Dr. Taniguchi obtained the approximate solution* simplifying the induced velocity field And assuming that the actual charac-teristic of blade section is the same as that of steady condition.') Furthermore he compared the solution with the open test results in the tank by the orthodox V.S.R. driving system, and has analyzed various coefficients and improved the theory.2)

As mentioned above, the driving system of the actual V.S.P. is a little different from that of the orthodox V.S.P., and, therefore, it is considered that there will be

some difference between the characteristic curve § by Taniguchi's solution and

those of the orthodox .V.S.P.: _{However, it is difficult to apply the difference of the}

driving system to the theory. Here, we should like to analyze the trial results,

using the characteristic curves with Taniguchi's solution. From the blade element theory by Taniguchi's solution, Thrust coefficient

CT

_pnrEPS

8

7,r4

a(e 21)/,(e, A1), (4)

Torque 'coefficient 30 90

4C .- 1 li

, , V.S.P 20E/125 K) <5 blades) 1.8

LE/00

I.

1111111111111111Mhill

11111661111111111111

'.4111.11 1.4

40 Re

1 )_ _

S. NAKAMURA, H. FUJII and A. NAGAYAMA :279

changes considerably during one revolution of the blade, according to increase of y.

?MI Trial Results of the Tug-Boats EquIPPed with Voith-Sclinelder Propellers

Al C

pn2D4S 2 r+ 7.±L8 2 2 21Y.13(e, 201, (5)

and from the momentum theory, Thrust coefficient

CT =27r2211--(.11 A). (B)

Therefore CT and A1 can be graphically obtairied from (4) and (6), after that, CQ can be decided .from (5), Then the propeller efficiency will be given as follows:

-727,=(2/2)(CriCe),, (7)

where,

D =diameter of blade orbital circle,

,n =number of revolution of propeller (rps),,

S =blade length,

e =eccentricity,,

v 17rnD AL =v3,/7:nD,

=advance speezi of propeller,

=intake velocity of the water into propeller, a =blade solidity= ZtohrD,

Z =number of blade,

to =chord length at blade root,

=lift coefficient of blade section=aa, =drag coefficient of blade section=C0+ ka2

a =attack angle of blade (rad.),

litc=coefficient of contraction of propeller current correspond to' ,efficiency .drop

due to non-uniformity of transverse distribution, of induced. velocity.

11(e, 2k), I2(A) and 13(e, Ai) are given in the following ellitotic 'integral,:

1 /2 / 1-:- Ai sin 0

li(e; cos20 d0;

7r j,2 1-r e Al (e+ Ai) sin ft

1.2(21)=_Lr .(1=

Ai sin 0),./1 + Ai-221 sin 0 d01,

ir -7T/2

1 cr/ (1A1 sin 0),./1-Fg.-22isin 0'_{cos20 dB.}

13(e' 24)=-7: -70 {1+ e 21 (e + Ai) sin 0} 2

The characteristics of the blade section a,, k, and the coefficient of con-= traction lc, were taken ,directly from the values that Dr. Taniguchi had got through

the. analysis of the open test results with the orthodox V.S.P., driving system, that

111 Q C,0 C h(2i) A = , v C,

20=

C,

is, a=5.34, Cz0=0.0190, k=2.24 and x=1.321. Fig. 12 shows an example of charac-teristic curves for 5-blade 20E/125 type.

5 4.0 ao CT 2.0 1.0

S. NAKAMURA, H. FUJII and A. NAGAYAMA 281

2.0

CQ

1.0

0.5

(b) Estimation of transmission efficiency.

In analyzing the trial results of ships with ordinary screw propeller, it is popular

V. S. P. 20 (5 bladeS

Ilil

6= E /1 2 5 Type ) 0.386 C7 = T/inzD3S C 0 = Q/in2D4S

'÷ -Et

1 =7irr,rD

iiihk

q 111116.

IL

N'Q.' e o ,..0.

,

,,-...0 0.9 d . ,d ,

11

1

02 03 04 0.5 06 0.7 08

Fig. 12. Characteristic curves calculated by approximate solution.

5-3. Results of Analysis

(a) Estimation of eccentricity to the reading of pitch indicator.

As is explained in 5.1, e changes considerably according to 0, when y is large. The question, therefore, arises about what curves of e shall be used, but, here, the following assumption is used: the thrust will be maximum where the blade comes near the phase angle which generates the maximum 0. Therefore, from Fig. 10, 0

to generate is obtained, e for that 0 is got from Fig. 11 and this e is assumed

to correspond to the given y. Fig. 13 shows the relation between e and the

dis-placement of pitch indicator 6 for each type of V.S.P..

' 0.

28Z Trial Results of the Tug-Boat S Equipped With Voith-Schneider Propellers

that DLII.P. should be obtained on the assumption of the transmission efficiency 72r through the measured S.H.P.. In this case, however, it is difficult to estimate the

power loss for the complicated V.S.P. mechanism and, therefore, the following ,method was adopted.,

Fig. 14 shows the comparision between the results by the approximate solution,

and the open test results by the orthodox V.S.P. driving and lever crank driving

systems for same e. From this figure, it will be understood that the calculated

value fairly conforms to the open test results by the orthodox V.S.P. driving

system, but is .different from the lever crank driving system. However, the smaller

the advance constant is, the smaller the differnce is. The actual V.S.P. driving

system is considerably close to the orthodox V.S.P. driving system, as is seen from Fig. 15,. which shows the curves of the attack angle of blade for one 'revolution of the orthodox V.S.P. driving system, lever crank driving system and actual V.S.P. It can be estimated, that the calculated values, Cr and CQ will almost be accurate at 2=0.. So,. at the bollard pull trials, e was given from the reading of pitch indi-cator CQ at 2=Q, c,orresponding to that e,,, was obtained from the characteristic

50

Displ. of Pitch Indicator 8' (mm) Fig. 13., Relation between eccentricity

e and displacement of pitch indi,

cator a.

5.0

4.0

01 02 03 0.4 05 06

Fig. 14., Comparison of characteristic curves. 07 08

N. N.' N

\

CT. CGI _{Calculated by approx.}

solution -Experimental' ,results

by orthodox V.S.drve Do.by lever cran k drive

----.- .'- -= , _N.. N. N... P N.;(?,...

\

\\0 i \ , Ca

\-\

, 1 I I \ p - _

\

' a 0.20 ,3s. MO

11\

i ''''.' '

\\\

\ , , -4Y V

-).

-4/ '0 cb k, I <79L

bill

Frill

ao CT 2.0 111 11 1.0 0.5

-\ \ 1.0 0.8 0.6 0.4 5 a

30

20

10

-20

-30

S. NAKAMURA, H. FUJI' and A. NAGAYAMA 283

Fig. 15. Comparison of variation curves of attack angle c/S.

curves and the transmission efficinecy was secured in the ratio of the D.H.P. and

measured S.H.P.. The 77r for each engine load is shown in Table 4. The 72, for

each engine load fluctures to some extent, but the average values for each boat are utilized in the analysis of the speed trial results. The flexible coupling is provided at the aft end of the intermediate shaft of the "DAITO MARU" and the loss due

to the coupling is included in 77, . In the other boats, the loss due to the driving

mechanism and others is about 10% and is considerably large, compared with that of the screw propeller.

Table 4. Transmission efficiency at bollard pull trials.

(c) Propulsion factors at speed trials

The results of the speed trials were analyzed by the ordinary method with this

VT The number of revolution of the propeller N, was obtained from that of the

intermediate shaft and CQ was given from AT, and D.H.P.. The eccentricity e was obtained from Fig. 13 through the reading of pitch indicator and using the

charac-teristic curves corresponding to this e, and the resistance from the results of the tank tests, the propulsion factor was calculated by the torque identity method.

0

11/11/1111

V.S.drive (e - 0.5)

Orthodox

___ Actual V.S.P(5blades)

---- Lever crank drive

A

1

_Ir

/,

/

1/4 0.749 0.833 0.895 2/4 0.745 0.929 0.959 0.955 0.985 3/4 0.799 0.877 0.944 0.892 0.936 4/4 0.816 0.908 0.793 0.870 0.875 O.L. 0.846 0.905 0.763 0.905 0.928 Mean 0.802 0.905 0.832 0.889 0.923

Name of boat DAITO_MARU ASAHI_MARU ASOU_MARU WAKAMIYA_MARU INABA

MARU Engine load VT 110

II

0 -6 -30 30 120 150 (deg) 0 2 2

284 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers I -t 0.8 0.6 0.4 2p 0.6 0.4 0.2 2 0. 0. 0. .4 .2 .o .8 .6 .4 1ZR 1.2 10 0.8

--e- -DAITO MARU --0--- ASOUMar.

a--

INASA

MARU i --A--ASAHI MARU --8-- WAKAMIYA MARU

-....nem

1-LL 1

nion

mid

11/11/PE--memr

MEM=

IF:._

num

II

110

_Emma

p.-.

liffi

mi

EN

IIM

NEPA.

paw&

6 8 9 10 1 Ship speed V8 (kt)

Fig. 16. Propulsion factors at speed trials. Fig. 16 shows each propulsion factor for ship speed V.

The wake fraction w of each boat, which ranges from 0.25 to 0.35, will be

regarded as rather large for the twin screw boat, due to the following reasons: the

actual V.S.P. disagrees little with the orthodox V.S.P. driving method and, therefore,

in the actual characteristic curves, as it can be understood from Fig. 14, CQ is large compared with that of the approximate solution. 2 was estimated as small and inevitably tv as large.

The hull efficiency va of each boat varies considerably according to the speed, 7

up

.8

--S. NAKAMURA, IL FUJII and A. NAGAYAMA 285

but at the normal output ranges reasonably from 1.0 to 1.2.

The relative rotative efficiency '0, of the "INABA MARU" is very high, which is associated with the high propulsive efficiency, and it was regared to be arised from some errors of the resistance calculation. As for other four boats, 1.0 will be suitable for

(b) Thrust reduction and pull ratio at bollard pull trials

Table 5 shows the thrust reduction of each engine load at bollard pull trials, which was given from the rope tension and the propeller thrust, obtained from Cr

at 2=0 by the approximate solution. There is much fluctuation in the table,

depending upon each engine load, and especially the thrust reduction of the "INABA

MARU" is far over from those of other boats. But for other four boats, the thrust reduction ranges from about 0.02 to 0.08 at the normal output, and in estimating the bollard pull it will be proper to take 0.04 as the mean value.

Table 5. Thrust reduction at bollard pull trials.

Name of boat

Engine load

DAITO

MARU ASAHIMARU ASOUMARU WAKAMIYAMARU

INABA MARU

Fig. 6 shows the relation between the pull ratio (towing force per 100 SHP)

and the S.H.P.. At the normal output, there comes out about 1.0, which will be

lower, compared with that of the tug-boat with the ordinary screw or variable pitch propeller. As far as the towing force, the tug-boat with V.S.P. is not so excellent

as that equipped with the variable pitch propeller, etc., but it will be favorable

when the excellent maneuverability is required.

6. Conclusion

The calculation results and analysis of the speed and bollard pull trials for

five tug-boats with V.S.P. have been described and the data to estimate the propul-sive quality or towing force have been collected by calculating the characteristic

curves. In order to get more accurate data, it is very necessary to carry out the

propeller open test through the actual V.S.P. driving mechanism and also the self-propulsion test, but there will be difficult to carry out such tests. There has been

1/4 0.095 0.007 0.163 0.236 2/4 0.011 0.172 0.142 0.184 0.264 3/4 0.019 0.021 0.093 0.109 0.262 4/4 0.020 0.031 0.023 0.080 0.292 O.L. 0.039 0.025 0.005 0.094 0.315 t

286 Trial Results of the Tug-Boats Equipped with Voich-Schneider Propellers

no practical data about the tug-boat equipped with V.S.P. and, therefore, this report will be sufficiently useful at this stage for the design data.

References

K. Taniguchi, J. of the Soc. of Naval Arch. in Japan, 74, 153 (1952) (in Japanese). K. Taniguchi. J. of the Soc. of Naval Arch. in Japan, 88, 63 (1955) (in Japanese). -1)