Trial Results of the Tug-Boats Equipped. with Voith-Schneider Propellers. ShOichi NAKAMURA, Hitoshi Fuji and Akira NAGAYAMA.

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1 ARCHEF Lab. v. Scheepsbolrakundi. Techn:sdle tiorra--1 DeLi 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 UNVERSTY Vol. 11 No. 47 Faculty of Engineering Osaka University Osaka Japan 1961

2 NO. 47 (Received June ) Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers By ShOichi NAKAMURA Hitoshi Fujii* and Akira NAGAYAMA** (Department of Naval Architecture) Abstract n 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. n 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 1 SHP at bollard pull trial etc. were analysed using the characteristic curves calculated by Taniguchi's approximate solution of V.S.P.. 1. ntroduction The boat equipped with Voith-Schneider propeller (V.S.P.) displays excellent manoeuvrability. t 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 performance. (2) There is a considerable loss of power in the complicated propelling gear mechanism. n 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-ndustries Reorganized. ** Osaka Shipbuilding Co. 269

3 1 27 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. Owner Name of boat Port where on duty Date of delivery Length overall (m) Length between perpendiculars (11- Breadth moulded (m) bepth moulded (M) Designed load draft (m) Gross tonnage Full load displacement CB designed CP designed Co designed (T) (t) Machinery Part Main engine type Number of set 133. GO Niigata L6F25 Diesel kegai 5MSD Diesel kegai 7MSD Diesel '.628'.887 Hanshin 26VSH Diesel Output (M.C.R.) (PS) R.P.M. ( ') Diameter of intermediate shaft (mm) Coupling Hull Part Propeller Table 1. DA TO Daito Unyu Yok llama Dec. 11 '57 Karuderis flexible. Principal particulars. ASAH Tokyo Kisen Yokohama ASOU WAKAMYA Yahata Seitetsu Tobata NABA Mie Prefecture Yokkaichi Nov. 6 '58 Aug. 15. '58 Sept. 25 '58 'Aug Kawasaki 'Mitsubishi 'TC 125 HCO4 hydraulic hydraulic Mitsubishi TC 14 hydraulic Type X Number 18E/115 x 2 2E/125 x 2 24E/12&X2 Diameter of orbital circle (n) L Number of blade Blade length L 247 Chord length at blade root Km) Reduction gear ratio /6 1/5 '59

4 S. NAKAMURA. H. FUJ and A. NAGAYAMA Particulars of Each Boat All is pusher type tug-boats and the principal particulars of each boat are shown in Table Measurement at Trials 3-1. Trial Conditions Table 2 shows the conditions of the speed and bollard pull trials for each boat. Table 2. Trial conditions. Sea condition Calm Calm Calm Calm Calm Specific gravity of sea water Draft fore (m) aft (m) mean (m) Trim (m).6 F.95 A.656 A.275 A.367 A Displacement (t) Date Weather DA] TO ASAH ASOU WAKAMYA Name of boat M ARU Speed Trial (condition in port) Bollard Pull Trial Wind velocity (m s) Dec. 8. '57 Cloudy 3. 1 Nov. 3 '58 Aug. 8 '58 Cloudy Sea condition Calm Calm Calm Calm Calm Specific gravity of sea water Draft fore (m) Fine 3 Sept. 18. '58 Fine 4.5 NABA Date Dec. 4. '57 Oct. 22. '58 Aug. 5. '58 Sept. 15 '58 Aug. 22 '59 Weather Cloudy Fine Fine Fine Cloudy Wind velocity (m s) Aug. 25. '59 Fine aft (m) mean (m) Trim (m).7 F O. 12 A.235 A O. 335 A.752 A Displacement (t)

5 272 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers 3-2. Measured tem (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. where 7rD4G Q= s 32 LR Q =torque ( kg-mm) D =diameter of intermediate shaft (mm) G =- modulus of rigidity of intermediate shaft =83 kg/mm L =gage length between ring centre points= 15 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 p Slip ring Fig. 1. Torsion meter 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: 1415 m Sea depth: about 8 m).

6 S. NAKAMURA. H. FUJ! and A. NAGAYAMA 273 Reading of Pitch ndicator 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. Fig. 2. Tension meter Measurement Results Figs. 3-5 show the measurement results at speed trials. The shaft horse power 15 _ E E `.- 1 i -. t DATO V.S.P. 18E/11 5 (4 blades) - -- ASAH pv. NS 1111fti. A N /... / Fig Ship speed V (kt) Results of speed trial of DATO and ASAH. 13

7 'Trial Results of the Tug-Boats Equipped with Voith-Schneder Propelilers 15 V.S.P. 2E/25 (5 blades) -A SOu MARL! ---- WAtAM iya MARL] As L No 1 \\9/' c Fig '' 91 1 Shiip speed T e : Results of speed trial of ASOU and WAKAMYA V'S P. 24E/125 (6 blades) NABA MA mo t CO cf). - 3'8 1 too 5 35 Fig Ship speed V; (kt) Results of speed trial of NABA l. 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.

8 C ' S. NAKAMURA. H. FUJ and A. NAGAYAMA r= Fig ' ' SHP Results of bollard-pull trials. 4 6 Hrllrilfrllrill :.''4 - OW -. 7 ix ofw1 li i< < Z to 4 CO < Z DA TO : // -- -a- -- A SAH ASCU WAHAMYA NABA Resistance Test Resistance tests were carried out with models at the experimental tank of Osaka University. Each model is fitted with.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 NABA 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. Name of boat Condition LPP B di dm- da (m) (m) (m) (m) (m) DATO Full load Boat Model DATO Boat & trial Model ASAH ASAH Boat trial Model ASOU Boat Full load Model & WAKAMYA WAKAMYA Boat trial Model NABA Full load Boat Model Trial Boat Model

9 1 1 ṟ 276 Trial Results 'of the Tug-Boats Equipped with Voith-Schneider Propellers Name of boat Condition Table 3 Trim (m) 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 is disadvantageous in respect of fesistance. n 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 n the calculation of frictional resistance Schoenherr's formula was used both. for the models and for the boats and tcf=.4 was added as roughness allowance for the boats. A 1 B CP S (m2) 1 Boat t DATO Full load. a Model kg NARU DATO Boat _6 F t & 1 trial Model _4 F kg 532 ) ASAH Boat G. 95 A t ASAH trial Model 1.64 A kg 1.1 ASOU i & WAKAMYA NABA Full load WAKAMYA trial Full load 'trial Boat Model Boat Model Boat Model Boat Model.-275 A..176 A.367 A.28 A t 61.8 kg t kg t kg t 6.8 kg : O. 631 _557 C C z.5 '.2 < o n. 1- la 1-5 Fu L46 r. ster. t rn bow 2 Trio 1 Oft 13W i...42algaill e / Fun Load i Tr. -- N$L'>''' 4\. / e'...';' ii.t. l'5i / - Mill F ut Load DA MPRu TY ;1 ASAH MAR Tr ' o i -5 tr / a A / Pr 4 3 / "a Frounde's No. V Lg Fig. 7. Residuary resistance coefficient curves..

10 S. NAKAMURA H. FUJ and A. NAGAYAMA Calculation of Eccentricity 5. Analysis of Trial Results Fig. 8 gives the outline of the driving mechanism of V.S.P.. n 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. As to the relation between the turning angle on the orbit (Z2X) and 1/r the following formula is obtained. C) Control rod C) Guide plate C) Cross head C) Driving link C) Blade Fig. 8. Blade acuating mechanism of V.S.P. Fig. 9.

11 278 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers cos(-1-) tan ik--= (a/y) sin(c+e) where 6=angle between arm A and 2 a =distance between cross head of arm A and Oi and the following relation can be obtained between ik and y. (1) o=132+tan--1 cos(13''11)(l/rt) sin(3iv1) (L/ R2) cos Oi - si n-1 Ri) cos 2+ cos(1- R2)- - (L R2)cos(13i-*)./(L/Ri)2+1-(2LR)cos(1-*) where i=-angle between arm R and 12 at Y= 2=angle between arm R2 and 2 at = L =distance between Oi and 2. The relation between the eccentricity e(on/r) and the change of the attack angle of blade y is as follows: 1 cos coty+sin 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 indicator 8. The relation between e and a therefore will be given. The driving system of the orthodox V.S.P. is arranged as - and the blade is attached at the location of 1. Therefore the change of the attack angle of blade is..tk and e is always constant independent of. n 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_. 5 4 V.S.P. 2E/125 (5 b odes) A 3 WAri / 2 Pir illin /1 4 AAR all \ -1 -co co (deg) Fig. 1. Relation between change of attack angle of blade and turning angle on the orbit. 1 gives the curves showing the relation between y and C for the given y as an example of the five blade 2E/125 type. From Fig. 1 and the formula (3) e is obtained as is shown in Fig. 11. When y is small e is almost constant to but e

12 1 S. NAKAMURA H. FUJ and A. NAGAYAMA :279 changes considerably during one revolution of the blade according to increase of y. " 4C ^.- 1 li K) 1.8 LE/ V.S.P 2E/125 <5 blades) Mhill ' Re Fig. ll. ) - -U 'JO Q (deg) 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. n the Mitsubishi Nagasaki experimental tank Dr. Taniguchi obtained the approximate solution* simplifying the induced velocity field And assuming that the actual characteristic 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 Torque 'coefficient 7r4 CT pnreps 8 a(e 21)/(e A1) (4)

13 111?M Trial Results of the Tug-Boats EquPPed with Voith-Sclinelder Propellers C Q C Al Cr+ 7.±L h(2i) 21Y.13(e 21 (5) pn2d4s 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 A = AL =v3/7:nd v =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 C =lift coefficient of blade section=aa =drag coefficient of blade section=c+ 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) 2(A) and 13(e Ai) are given in the following ellitotic 'integral: 2= 1 /2 / 1-:- Ai sin li(e; cos2 d; 7r j2 1-r e Al (e+ Ai) sin ft 1.2(21)=_Lr.(1= Ai sin )./1 + Ai-221 sin d1 ir -7T/2 1 cr/ (1A1 sin )./1-Fg.-22isin ' cos2 db. 13(e' 24)=-7: -7 {1+ e 21 (e + Ai) sin } 2 C 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

14 S. NAKAMURA H. FUJ and A. NAGAYAMA 281 Fig. 12 shows an example of charac- is a=5.34 Cz=.19 k=2.24 and x= teristic curves for 5-blade 2E/125 type iiihk ao CT lil V. S. P. 2 q E / ( 5 blades ) 6 =.386 Type C7 = T/inzD3S C = Q/in2D4S ' -Et 1 =7irrrD CQ L N'Q. ' e o d. d Fig. 12. Characteristic curves calculated by approximate solution Results of Analysis (a) (b) Estimation of eccentricity to the reading of pitch indicator. As is explained in 5.1 e changes considerably according to 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. Therefore from Fig. 1 to generate is obtained e for that 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 displacement of pitch indicator 6 for each type of V.S.P.. Estimation of transmission efficiency. n analyzing the trial results of ships with ordinary screw propeller it is popular

15 1 ' i Z Trial Results of the Tug-Boat S Equipped With Voith-Schneider Propellers that DL.P. should be obtained on the assumption of the transmission efficiency 72r through the measured S.H.P.. n 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. t can be estimated that the calculated values Cr and CQ will almost be accurate at 2=.. So. at the bollard pull trials e was given from the reading of pitch indicator CQ at 2=Q corresponding to that e was obtained from the characteristic V ) Y bill -4/ ' cb k <79L.6 ao Frill.4 CT 2. '. N. N.' N \ _N.. N. N... CT. CG '- -= P N.;(?... \ \\ i \ Ca Calculated by approx. solution - Experimental' results by orthodox V.S.drve Do.by lever cran k drive \- \ \ \ 5 a Displ. of Pitch ndicator 8' (mm) Fig. 13. Relation between eccentricity e and displacement of pitch indi cator a. Fig. 14. \ p - _ \ ' a.2 3s. 11\ MO ''''.' \\\ 7 8 Comparison of characteristic curves. \.5

16 S. NAKAMURA H. FUJ' and A. NAGAYAMA V.S.drive 11/11/1111 Orthodox (e -.5) 11 Actual V.S.P(5blades) ---- Lever crank drive Fig (deg) / / r A 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 "DATO " and the loss due to the coupling is included in 77. n the other boats the loss due to the driving mechanism and others is about 1% and is considerably large compared with that of the screw propeller. Table 4. Transmission efficiency at bollard pull trials. Name of boat Engine load DATO ASAH ASOU WAKAMYA NABA 1/ / / / O.L Mean VT (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 characteristic 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.

17 memr 284 Trial Results of the Tug-Boats Equipped with Voith-Schneider Propellers --e- - DATO ASOU Mar. a-- NASA --A- -ASAH WAKAMYA -...nem 1-LL 1 i up.8 -t p nion 11/11/PE-- mid liffi mi EN F:._ MEM=. num _Emma 11 M NEPA. paw& p o ZR Fig. 16. Ship speed V8 (kt) 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.25 to.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

18 S. NAKAMURA L FUJ and A. NAGAYAMA 285 but at the normal output ranges reasonably from 1. to 1.2. The relative rotative efficiency ' of the "NABA " 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. 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= by the approximate solution. There is much fluctuation in the table depending upon each engine load and especially the thrust reduction of the "NABA " is far over from those of other boats. But for other four boats the thrust reduction ranges from about.2 to.8 at the normal output and in estimating the bollard pull it will be proper to take.4 as the mean value. Name of boat Engine load Table 5. DATO Thrust reduction at bollard pull trials. ASAH ASOU WAKAMYA NABA 1/ / / / O.L t Fig. 6 shows the relation between the pull ratio (towing force per 1 SHP) and the S.H.P.. At the normal output there comes out about 1. 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 propulsive quality or towing force have been collected by calculating the characteristic curves. n 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 selfpropulsion test but there will be difficult to carry out such tests. There has been

19 286 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. -1) 2) References K. Taniguchi J. of the Soc. of Naval Arch. in Japan (1952) (in Japanese). K. Taniguchi. J. of the Soc. of Naval Arch. in Japan (1955) (in Japanese).