On Design of a 50 Knots, Payload 1,500 Ton Hybrid Ship
S.1. Yang’, Y.G. Kim’, C.D. Koh’, J.W. Ahn’, Y.J. Chol, J.W. Kim’, Y.H. Park’
ABSTRACT
An 80 m-length hybrid ship supported by lifi and buoyancy equally with a speed of 50 knots and the payload of 1,500 ton
was designed. The design concept of the hybrid ship was validated by carrying out experiments in real sea condition
with a 10 m long test ship “NARAE”. The similarity rule was kept up except the size of the waterjet duct and side struts
enclosing waterjet ducts. The sea trial tests including wateq”et propulsion system and motion control system had been
carried out in1997[2].
The performance of waterjet propulsion system is analyzedfiom the measured data in sea trial test and compared with
model test results of the similar wateq”et system. Measuring techniques of jet velocity, gross thrust and impeller torque
for the waterjet system are explained. Usefil data such as the pump pe~ormance, the jet efficiency, the losses of inlet
duct and nozzle are obtained. Comparison shows a similar behavior,
The motion control techniques in the real sea are also presented. Since the hybrid test ship adopts a lower body and
submerged foils. Since this type of ship has a substantial instability in heave, pitch and roll modes at the foil-borne stage
due to little restoringforce, an active control isindispensable to keep the stability. Four sets of hydraulic actuators are
equipped to drive the foils, and several sensors are installed to measure the ship motion. PID controller is adopted as a
motion controller, and Pentium-class industrial PC is used for the real-time control. Quite satisfactory results were
ob-tained through the sea trial tests.
INTRODUCTION
The hybrid type high speed vessels have been developed in Korea from 1990s, and KRISO finished the conceptual design of the hybrid cargo vessel[l ,2,3,4]. The designed hybrid cargo vessel is operable in the sea height of 6 m with the speed up to 50 knots and the deadweight of 1,500 tons and it is supported by buoyancy and foil lifting force charged 50$%0of its weight each,
To validate the performance of the designed cargo vessel, a 10 m long hybrid test ship “NARAE’ was designed and constructed. From the sea trial of the test ship its perfor-mance was verified and showed good agreement with the experimental and theoretical predictions.
Measuring techniques of jet velocity, gross thrust and impeller torque for the waterjet system are presented. The performance of waterjet propulsion system in the sea trial
test isanalyzed and compared with model test results of a
similar waterjet system. The results of sea trial test show a similar behavior to those of the model test.
The motion control techniques applied to the test ship and the results of the motion control tests in the real sea are also presented. The test ship adopted a hybrid hull form with a lower body and submerged foils. This type of ship has a substantial instability in heave, pitch and roll modes at the foil-borne stage due to little restoring force, so an active control is indispensable to keep the stability. Four sets of hydraulic actuators were equipped to drive the foils, and several sensors were installed to measure the motion of the ship. PID controller was adopted as a motion con-troller, and Pentium-class industrial PC was used for the real-time control. Quite satisfactory results were obtained through the sea trial tests.
THE DETAILS ON DESIGN
Conceptual Design of Cargo Vessel
The designed cargo vessel was planned to have a catama-ran type upper hull[5,6,7]. Its wide deck area is useful to load cargoes easily and can minimize the damage at an emergency such as the trouble of the ship control systems. A half of ship’s weight is supported by the static buoyancy of lower hull designed to have a streamlined axial sym-metric form and another half of its weight is supported by the hydrodynamic lifting force of the main foils.
,&
11 --- ,‘. .,/,\\.,”.,’1 I ,,, 1 # —. I -1 -.. - I ‘k’ I.,?I-.”-; I .. .\ ~,;z. ,./,1 I l,. , ‘.1, ,1 \i \ I 1~ “L —.‘ill
---
--
.!-.—---:_~-+!77. ---
IB[
0_-
_,___
--
_,---
i---0; ---1---.. -,.-. .--; ___ ---I --- __--— —
---a... . -
:+3 .. -—--k -*-.- ——-—______. ..L. -: -––;–... ---0, ---l-—— --–:-– 0 -–-;)
*---Fig. 1 General Arrangement of 80M Class Hybrid Cargo I
Vessel
As shown in the Fig. 1, V-type strut at forebody and I-type strut at after body connect the upper and lower hull. The waterjet inlet is located at both ends of main foils and connected to the guide ducts of side struts. The sea water was sucked in through the waterjet inlet of lower hull and pumped to waterjet on upper hull. Moreover, the side struts was fixed structurally at main foils expecting the reduction of the 3-D effects of main foils. A pair of for-ward fin is attached on the lower hull to control the ship’s motion. Table 1 shows the principal particulars of the designed cargo vessel.
Design and Construction of the Test Ship
After the due consideration of the test ship’s dimension and displacement, the scale ratio of test ship was decided to be 1/8 for sufficient hydrodynamic performance tests.
Table 1 Principal Particulars of KRISO Hybrid High-Speed Cargo Vessel
Length of Upper Hull 80.0 m
Lower Hull 85.0 m
Overall 85.0 m
I
Breadth 37.2 m I
Depth 16.5 m
Draft at Hull Borne Mode 12.5 m
1
Container Load Capacity 200TEu The scale ratio was not applied to the side struts since it was impossible to change the waterjet inlet and guide duct according to the scale ratio[6,7]. Table 2 shows the prin-cipal dimensions of test ship.
Table 2 Principal Particulars of KRISO Hybrid Test Ship
!!~A~~!l
Scale Ratio
Length of Lower Hull Length of Overall Breadth
Depth from B.L. K.L. Lower Hull Diameter
Main Foil Span (Foil only
Main Foil Chord
Forward Fin : Span
Chord Draft : Hull Borne
Foil Borne Speed : Max. 1/8 10.625 m 11.065 m 4.650 m 3.700 m 1.600 m 0.700 m 1.675 m 4.650 m 0.800 m 0.500 m 2.530 m 1.500 m 21.0 kts lMain Engine I D/E(TAMD 63P) lPropulsor lWaterjet(LIPS 36DL)X2set:
Upper hull was constructed of FRP sandwitch structure for lightening and lower hull was made of FRP single skin structure [6,7]. Appendages were formed by the mold and only essential equipment was installed for lightening the ship’s weight.
Main propulsion systems are :
* 2sets)
-Reduction gear : Reduction ratio 1/1.408
-Propulsor: Waterjet (Input power 240Kw *1,989RPM) Ship motion control system is composed of the hydraulic tank, pump, accumulator, manifold, actuator, pressure filter and cooler.
The section of NACA 0016 was applied to all struts con-necting between upper and lower hulls. Main foils of NACA 4412 section with 2 degree of incident angle were employed to support 50% of hull weight with lifting force. Forward fins of NACA 0012 section to make 0.4 ton of control force were engaged to control pitch and heave of ship motion[8,9]. Correlative locations of upper hull, lower hull and foils were established keeping up the even trim at sea and still water. Fig. 2 shows the photograph of test ship after construction.
linearization of the equation. But, it’s not easy to setup the equation of motions for this ship, moreover the lineariza-tion of this equalineariza-tion might be meaningless because of its severe nonlinearity. So, the practical control scheme is applied to the controller design, and the control gain is determined based on the results from the simulations and the model experiments in the model basin[lO]. The target modes of automatic control are confined to heave, pitch, and roll. The remaining modes – surge, sway, yaw – can be classified to relatively low-frequency motions, so the manual maneuvering is applied to them.
Servo valve and LVDT are installed to each cylinder to control the position of a hydraulic piston rod. In addition to the operation tests, the simulation of hydraulic system is also carried out. The proportional controller is selected, and the control gain is obtained through simulations and test operations[l 1].
Control scenario
The operational mode of this ship can be divided into two parts : hull-borne mode and foil-borne mode. The change of these two mode should be as smooth as possible to keep stable operational conditions. A proper scenario during operation should be prepared. The optimal control path of the operation is calculated based on the variational principle using the simplified equation of motions[12]. Fig. 2 Photograph of 10 m Class Hybrid Test Ship
Heave Command Motion Control System
The ship floats by the buoyant force from both bodies at the hull-borne mode. But the upper hull full y emerges out of the water at the foil-borne mode, and a portion of her weight is supported by the lift from the 4-lifting foils attached to the lower hull side. This type of ship has the substantial instability, and so an active control is indispen-sable.
Controller
The control scheme can be divided into two parts. One is the control of the ship’s motion, and the other is that of the hydraulic system.
As a general rule, the controller design should be preced-ed by the formulation of the equation of motions and the
A cccl. Take Off Running Landing Decel. I
Pitch Command
~ .MtidPUch..
..St$ady WCh
Fig. 3 Control Scenario
Banking-turn
There is a lack of the stability in pitch, roll, and heave during running at the foil-borne mode due to little hy-drostatic restoring force, since only the thin struts are on the waterplane. Specially the centrifugal force can
aggra-vates theroll stability during the turning operation. Since the vertical gravity center of this ship is far above from the waterline, the centrifugal force acting in the opposite direction of turning might cause the very dangerous situa-tions such as a saturation in control and collapse. The banking-turn, as a well known scheme, is adopted to compensate this undesirable effect. The gravity-induced force produced by tilting a ship in the same direction of turning makes all or a limited portion of the centrifugal force canceled out. In addition to stability increase, the banking-turn can improve the maneuvering performances including the turning ability[ 13].
Control and measurement system
Four hydraulic actuators are installed inside the lower hull for driving 4-active-controlled lifting foils. The angle of each lifting foil is directly related to the position of he each piston in the cylinder, LVDTS measure their posi-tions and feed the signal into the main controller. Then, the main controller calculates command angles and feed control output signals into servo valves on each hydraulic actuator.
01Systm
The main controller is implemented using Pentium-class industrial PC with A/D and D/A processing boards.
-Heave :
The 3 types of sensors are used to measure the heave displacement (the capacity-type wave probe, the pres-sure sensor, and the ultrasonic height sensor). The heave input value is calculated by the proper combina-tion of their signals. Properly designed low-pass filter is
used to get better performance in waves. Accelerome-ters are used to measure vertical acceleration and to get velocity by integration.
- Pitch and Roll :
The 2-axis vertical reference gyro is used to measure angles and rates.
- Yaw and Speed :
Yaw rate and the ship’s speed should be measured to calculate the command signal for the banking-turn. Rate-gyro is used to measure the yaw rate, and GPS is used to get the advancing speed of the ship.
SEA TRIAL TEST OF 10M CLASS TEST SHIP
Test in Harbour
The performance of the test ship were carried out in har-bour and berth of shipyard for the validation of the test ship safety[7]. All tests in harbour were progressed ac-cording to the procedure of harbour acceptance trial. The test and evaluation was carried out in harbour classified into hull performance, hull outfit, machinery and elec-tric/communication.
F‘ig. 4 Photograph of the Harbour Trial of Hybrid Test Ship
Speed test at sea
Speed test was carried out at same time with the perfor-mance test of waterjet to measure the ship’s speed, RPM of propulsion shaft, torque and thrust of waterjet. Total breaking horsepower of two engine is 680PS. The results of the speed test at sea are affected by added resistance due to waves, control fin, hulI surface roughness, etc., and it is difficult to predict accurately the effect of speed re-duction. Table 3 shows the speed test results at a draft of 1.5 m.
Table 3 Speed Trial Results (T=l .5m)
VS(knots) I PE(HP) 8.0 50.0 10.0 75.0 12.0 57.6 14.0 103.0 16.0 135.0 18.0 208.0 20.0 250.0
The difference between sea trial and model test at low speed is analyzed to be induced by large angle of the flaps and fins to get the ship’s lifting force. The quasi-propulsion efficiency at 17.7 knots corresponding to 50 knot of the designed cargo vessei was 0.41 with 205 EHP(PS) and 500 BHP(PS). The maximum speed of test ship was about 19 knots with 0.44 of quasi-propulsion efficiency, 233 PS of EHP and 530 PS of BHP.
Fig. 5 Performance Trial of Hybrid Test Ship at Sea
Sea Trial Test of Propulsion System
This part describes sea trial tests for a waterjet propulsion system attached in the test ship. However, as the test ship operates with several appendages and control units, the test results may be different from those of the model test due to difficult measuring techniques. Particularly, as it is impossible to install the dynamometer to measure thrust and torque, new measuring system by strain gauge must be composed. Measuring techniques of jet velocity, im-peller torque and thrust, ship speed and mean pressure of duct inner part are described. The measuring results are used to analyze the performance of the waterjet propul-sion system. The analyzed results are compared with tho-se of the model test[ 14].
Equipment for the performance test
Fig. 6 shows measurement diagram of waterjet propulsion system. In order to measure real torque and thrust oc-curred by the impeller, strain gauges must be attached on the impeller axis at duct inner part as shown in Fig. 6. As the impeller axis turns max. 2000 RPM in water, special management is required for watertight and safeguard of the strain gauge. The strain gauge is installed using the
special method as shown in Fig. 7. After the sea trial test, it was confirmed that there was no problem in watertight and safeguard.
~
w -. ., .,
-.. . . . 7.(.. ‘---- .,”:. . W$+om“.,,$
Fig. 6 Measurement System of a Waterjet Pump
Fig. 7 Watertight and Safeguard of a Strain Gauge
The impeller axis has small hole of about 1.0 m length at the central part to connect signal lines of strain gauge with exterior wireless communication equipment(wireless Data Coupler). The wireless Data Coupler(Acurex 1200B) consists of a module which is attached on the rotation part(Collar), an antenna and a readout unit. The antenna is connected to the readout unit which has the signal ampli-fication function.
Water headrise by the impeller and diffuser can obtain from mean pressures which are measured at D-section
(the front of the impeller), C-section (between the impel-ler and the diffuser) and B-section (the rear of the dif-fuser). It is necessary to manufacture several pressure holes at each section in order to obtain more accurate mean pressure. There are 4 pressure holes at the D-section and 7 pressure holes at the B-section and C-section, re-spectively. Several pressure holes at each section are con-nected to a strain-gauge type pressure transducer (Kyowa, PG-2KU) which can measure up to 2 kg~cm2. The pres-sure transducer signals are amplified using the strain-gauge type amplifier which is designed and manufactured in KRISO[15].
Impeller rotation speed can be known approximately con-sidering reduction gear ratio from engine rotation speed. However, accurate rotation speed is measured by RPM pick-up sensor which is attached on the universal joint. The RPM pick-up sensor has a photoelectric close-contact switch that occurrs a pulse signal per a rotation in general. This pulse signal is converted into voltage signal by a F/V(Frequency/Volt) converter. The aforementioned strain-gauge type amplifier[ 15] includes two F/V convert-ers.
The flow rate at the nozzle section can calculate using the jet velocity, which is measured by the pitot tube installed behind the jet nozzle. The pitot tube is connected to a differential pressure transducer (Validyne, DP15-48). The pressure transducer signal is amplified using the carrier amplifier.
Several amplified signals are stored at a 16-channel Sony digital recorder which is controlled by a notebook PC. At the same time, the time signal is observed in the PC monitor. Hence, observing the real-time signals measured from all sensors, the sea-trial test for the waterjet propul-sion system is carried out.
Measurementresults
Measuring the torque and thrust simultaneously, two col-lars must be installed on the coupling which connects the impeller shaft and the universal joint. However, it is im-possible to install two collars together due to spatial re-striction. So torque and thrust are measured in separate sea-trial test. Figs. 8 and 9 show the torque and thrust measurement results, respective y. Various symbols rep-resent the rising height and the advance direction of the test ship, respectively. Irrespective of the rising height and the advance direction, the torque and thrust are linearly related to the impeller rotational speed.
l.zy soil 10QO 1500 8ql?z
~:o$*:p::Jzfl*
"""'""""""'""`"""-":"""~""""---.-.--..-.'..'~.-...--...-....~.-... 0.6
L 4
Fig. 8 Torque (Sea trial test)
20y 500 IOoil 1500 z% ;g:;~ H=o, Dlr=l 17.5 :-{ : H-D,D.-II . ..'.' . . . ..~. . . .. . . ..[ . . . .. . .. . . .. . .. . . 17.5 A H=cL25.Dir-l H-L125, DlnzI1 15 ;... : H@5, Du+ . . . .. . . ..j . . . .. . .. . . . H=05. Dm.11 /!.: ,5 ;$ IS=@75. D,d -12.5 -..: 0 ::~.;mll .--....-.-..-{---h -.---.-: 12.5 ~ ::, . H-l. D,mll ~v E 10 ...T ...{...~ ...= 10 $ + 7,5 . ... . .. . ... . ... .. .. . . ... ... .. ... .. . .. . ....~. .. ... ... .... . ...m: . .. .. ..~... ... .. ... . ... .. ... ...= 7.5
I
-1
5 .. .. .. .. .. ... ... ... ...+ ... ... .. . .. ... ... .. ... . ../& . .. .... .. . .. ... . .. . ..~.. ... ... .. ... . .. ... ... . 5 J 2.5 ~ .. . ... .. ... .. .... . .. .. . . .. ..a..9 .. ..n . . ..j . .. ... .. .... ... .. ... . .. . .. .... ... .. .. ... . .. .. . ....= 2.5 ~: 00 I I 1 500 1500 Zod?l i~MFig. 9 Thrust (Sea trial test)
Using the experimental results obtained from a pitot tube and a differential pressure transducer, the jet velocity (Vj) is calculated as follows:
‘,=F
(1)
The jet velocity is measured at the position of 0.5R~ (R. : nozzle radius) from the central point, and the result is shown in Fig. 10. The jet velocity shows the similar trend to the torque and thrust. However, while the jet velocity has first-order linear relation to the impeller rotational speed, the torque and thrust have linear relation above second-order.
Analysis of measurement results
From the measured data in sea trial test, performance of the waterjet propulsion system is analyzed and compared with that of a similar model waterjet system. The model
waterjet propulsion system is a stand-alone waterjet ex-perimental system similar to an equipment for the con-ventional propeller open water test, as shown in Fig. 11
[16] 30 0 500 loco 1500 2% ;IJ: ■ H+. Dud I&0 Du-11 25 -.. : “*.M, Dp, ... ... ... ... ... .... .; #...--:8 25 A H=I125Dill H*,5 k== ; M+.j. ~[1 20 -. ● H=I175.h+ ... ....{.---..m ---& 20 g M=c.75.Du=.1[ lb]. Dir-l H=). Du=l! $,5 :., ... ...y ... ...*@~ ; ... ...~...-~ 15 > •~ 10 . ... ...+ ...= ...j ... ... ...j. . ...-,@: 10 .
lliiillil~
00 500 1000 15C0 2ol& RPMFIR. 10 Jet Velocity (Sea trial test)
Fig. 11 Model Waterjet Experimental System
The waterjet propulsion systems of the model and the test ship are designed for the same target ship. However, im-peller type, diameter of duct inner-part and nozzle di-ameter, etc are different each other. Table 4 shows differ-ent principal parameters between the model and the test ship.
Table 4 Principal Parameter of Waterjet Propulsion Sys-tem
r Item Test Ship Stand-alone Model
Impeller Type Mixed Axial
Impeller Dia. 0.335 m 0.360 m
Impeller RPM 2,000 RPM 2,200 RPM Inlet Dia. 0.331 m 0.260 m
Nozzle Dia. 0.163m 0.2215 m
The water headrise by the impeller and the diffuser is caculated using mean pressure measured at B-section, C-section and D-C-section shown in Fig. 6 [17]. The impel-ler/diffuser efficiency is calculated using the water headrise and the supply power and defined as follows:
(2)
‘Ip — .,
27cKQ
where J~ (= Qj /nD3) denotes the flow rate coefficient, K~(H/n2D2)the head coefficient, ~ the torque coefficient. H denotes the headrise across the impeller. Fig. 12 shows the impeller/diffuser efficiency for the test ship and the model. The efficiency presented as a function of the ship speed(V,) shows a similar trend for both of the test ship and the model. However, the test ship efficiency is higher than that of the model . This is due to the fact that while the test ship has a mixed-type impeller, the model has a axial-type impeller. As a axial-type impeller turns higher RPM than a mixed-type impeller at the same test condi-tion, it is known that a mixed-type impeller has higher efficiency. Moreover, it is thought that different diffuser form may also have an effect on the impeller/diffuser efficiency.
1’:
1
0.9 ...--.--... --.. --... --}--.m-.- .. .. ..~-...~--.~~q#.*.-.o --- 0.9 <~ o,8 . ..--..--..mp~ ... ... .... ...~...j... r’ [ ■ ; D, 1.H=CIU : D“ 11,H&m 0.7 ... ...+ ... ... .... ....~... : D. [, H=o25m D. [1,H=325111 1 h I. H-o 5m ~~ ,V Dk [[. H4.5mO.L
~~i~~
~
%F!!VJ.
0.6 . .... ... ... ... .... ... ... ... .... .. ....j ....J o 5 10 15 VJKts)Fig. 12 Impeller/Diffuser Efficiency
I
0.80.7 0.6
Figs. 13 and 14 show the relation of jet efficiency and ship speed, and the relation of jet efficiency and IVR(Inlet Velocity Ratio; Vs/Vj), respectively. The jet efficiency (Tj) presented with the model test results is defined as follows:
~j = 2IVR (1 - IVR) (3)
l+ fj–(l–~j) lVR2+2g Ah/V,2
where Ah denotes the height of the jet centerline above the undisturbed water surface, ~. the headrise loss factor
from the duct inlet to the impeller, ~j the headrise loss factor from the diffuser to the nozzle. gin and ~j are de-fined as follows: et. = ~fl–PP, +1/2p. (~.;–V; ) – p., g Ah (4) 1/2 pm y; ~,. ‘p” -p”’”;;:;? -V;) (5) m
where Pp, and Vpi denote the mean pressure and the mean velocity at the front of the impeller(D-section), PPOand VWthe mean pressure and the mean velocity at the rear of the diffuser(B-section), respectively. From Eq.(3), it can be understood that IVR is an important factor and rela-tively small nozzle diameter makes the jet efficiency re-duce.
Figs. 13 and 14 show the trend that as the ship speed and the IVR are increased, the jet efficiency is increased. Be-cause the test ship operates at the low IVR region due to relatively small nozzle diameter, the jet efficiency of the test ship is slightly lower than that of the model at the same ship speed (see Fig, 13). However, as shown in Fig. 14, because two headrise loss factors(~n and ~j) have an dominant effect on the jet efficiency presented as a func-tion of the IVR, the jet efficiency is relatively disadvanta-geous at the model waterjet propulsion system with small duct diameter (with high flow velocity).
The effective horsepower(EHP) can be obtained using the torque measurement result and the quasi-propulsive effi-ciency(q~), The quasi-propulsive efficiency is defined as follow:
~1) =~P ~j ~H (6)
where the thrust deduction factor(t) must be considered to calculate the hull efficiency(q~). The thrust deduction factor means the difference of the resistance performance between the condition which a duct inlet is closed and the condition which an impeller is operated. However, it is very difficult to get this thrust deduction factor of the pod-type waterjet propulsion ship experimentally. Moreover, it is more difficult to get it in the sea-trail test. For this rea-son, the thrust deduction factor cannot help predicting or assuming. Because there are the effects of the wave, flap angle increase for hull rising and nozzle form in the sea-trial test, it is thought that the full-scale ship resistance may be increased more than that of the model ship. In order to predict the thrust deduction factor of the test ship, various factors of resistance increase and the self-propulsion test result of the model ship with the
flush-type waterjet propulsion system are considered. Finally, the thrust deduction factor is assumed as 0.2 and the ship wake neglected. For the consistent performance compari-son, the thrust deduction factor of the model ship also is assumed as 0.2. 0.55° 5 10 15 2%.55 ~i...’’’’’~’rj .. ... .7 ; ■ D,, 1,H=M ,! ❑ h 1[,H=Om 0.5F1 A Dlrli.H+25m D!, 1 Ha ?Sm ...}. ...i...o.5
I
vv l),,D. 11,H-0 h1,H=c,5m D,, 1,H* 7Sm : D,, 11,H=dl75m / 9 0.45 . ● mrl, H=l Om n w 11.H-l On ‘i ‘“””j-””’”’’”””’””””””- ““”~y”””’””-””””-” 045 — F-[796;74;
]
0.4 ...- .... ... ...Q.-- ...H ... ... :.-....r-- . ... ... ... .... ... ... ... .... 0,4 0.35 .. ....- .... ...-.= . ...-~-.. ...- ... ....!-- ....-...-...-...-...-...~ .. ... ... ... 0.35 0.30 I I I 5 10 15 #.3 V$Kts)Fig, 13 Jet Efficiency vs. Ship Speed
0.59 ‘ 5r 0,2 0.25 0.3 0.35 0.4 ?’ 43.55 :-1 ~ ~ 0.5 –j A Di 11,H-3 Mm ~.j... ..-..-...-.. ~... .. ... 0.5 17 Di I,H+,%n D“n,H-d Sell ‘, [-. [-.[-.l [-. [-.[-.[-.&[-.q[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.[-.l[-. . .. . . . 0,45 ~ 0.4 :“Jmp 1 ‘ . ... .. ... .... ...n .. . .. ..w . .. ..j ... .. .... ...!.. ...-..-..-...!-. .-...--- 0.4 b .Clm !Dm %]:~~ :m 0.35...+...!...i...\...!...-0.35 %15 I I I I I 0.2 0.25 0.3 0.35 0.4 0.493 IVR(V@fJ)
Fig. 14 Jet Efficiency vs. IVR
Fig. 15 shows the quasi-propulsive efficiency for the test ship and the model. The test ship and the model present the similar performance above the ship speed 10knots.
Both of them show the quasi-propulsive efficiency of about 0.315 at the ship speed 15 knots. However, because the thrust deduction factor is assumed, this can not be thought as the accurate comparison. In the future, this has to be investigated accurately through the self-propulsion test of a model ship, not a stand-alone waterjet experi-mental system.
Fig. 16 shows the effective horsepower (EHP) calculated using the torque measurement results and the
quasi-propulsive efficiency. The rising height shown in Fig. 11 is maintained by controlling the hydrofoil with the flap. As the ship speed is increased at the same rising height, the resistance tends to increase rapidly. At the same ship speed, the resistance of the rising height 0.75 m is smaller than that of any other rising heights. At the rising height around 1.0 m, the resistance is increased. Therefore, it is thought that the rising height 0.75 m is optimal for the present test ship.
0.4° 5 10 15 2%.4 1“’” -- ‘
Dw L H% : W [1.H=Om & III, [. H=O25m ,!
11
...
A 0.35 : ● o : CD 0.3 —o.25\
...
..4.X ...~
...
..]o.25
0,20 I I I 5 15 &2 V,;:ts)Fig. 15 Quasi-propulsive Efficiency
250° 5 10 15 20250 !2! x . . . .. ...—. ■ DwI, I+=LM ❑ D, Il. H% 200 -.. Dw1,H=02$m 2 D. 11,H-0.2Sm .. ... .. ... ... .. ... ...!.... .. .., 0+ -,..-,.- 200 v D=1,H=03m v D“ 11,H-() 5m DII 1,H=L.T5m ~: ~ D. 11.H*.~Sm 150 -..4 ~r,,”=,,~ ---{..- . . . ..- . . . ...&) --- 150 n. 0 DII 11,H=l,ln x _ 96Wamry)IMcdd T., : % ; w
:,,..17/,,,,,,:
100 . .. ... .... ... ... ... .... .... ... ...j ... .. .. . .. .. ... .... .... .. ... ... ... ... .. 100 ~] 50 -.- . ...-..--...-l .... .... ..- ...~ . ..~... .... ... ... ...l ... ... ... .. ....- 50 in ;0 ●,@ 00 5 10 15 2$ V~(Kts)Fig. 16 Effective Horse Power (EHP)
As stated above, the overall propulsive efficiency and the
individual performance are analyzed for the waterjet
pro-pulsion system of the test ship. Though the sea-trial testis more difficult than the model test, the test results are very
stable. Though the model waterjet propulsion system is
different in the impeller type from that of the test ship as
presented in Table 4, the model performance shows good
correlation with that of the test ship. However, further
investigation k required.
Maneuvering and Seakeeping Test
During 3 months from August to November in 1997,a number of trials were carried out at the real sea. On the whole, the satisfactory performance was obtained. Parts of the test results are shown here.
Fig. 17 is a measured time history of motions during take-off trial. The take-take-off height was 1.0 m, and additional pitch angle (added pitch) was introduced to get sufficient lift at take-off stage. It shows that the overall characteris-tics of tracking control is satisfactory during take-off, cruising, and landing.
— Command — Measurement o Port + Stbd 10 I / 0 t H.*v4 (m) / “ \ o I — - — 5Pitch rdeg) o I +; \ — 5 5 Roll (q .9) 0 I - * =.
Fig. 17 Time History of Motions (Take-off Height 1.0 m, Initial Pitch : 1.5°,Added Take-off Pitch :1.50,
Figs. 18 and 19 are obtained from a steady turning trial. The steady roll angle in Fig. 18 represents that the bank-ing-turn scheme worked well. Fig. 19 shows the turning trajectories with and without a drift correction. This drift is mainly due to strong currents in the area where the trial test was performed.
CONCLUDING REMARKS
The hybrid test ship was successfully developed and test-ed at sea to validate the performance of the hybrid ship with foils.It was demonstrated the possibility of the hy-brid type cargo vessel and established the core technolo-gies of hybrid ship development.
, 1 20 10 1 1 1 0 I I I *.”* (m) > I I I 0 I I I I [ [ r 5 > /t. /I~d.g) I I I I I I I I 0 I .5 I I I I I [ I [ 5 -i?.)! (V09J I I I I I I I I 0 I I I I I I I I I 3% ~. “ +91. (q*9) I I I [ I I I Oa .30 I I I I I I I I I 30 ~., p ~ngh (d@g) I [ I I I I I O* .30 I I I I I I I I I 100 120 140 160 lBO 200 Time (see)
Fig. 18 Time History of Steady Turning Trial (Take-off Height 1.0 m, Banked-turn Ratio : 0.5)
400 300 g ~w a) 2 ~ 100
a
o -100 100 0 -1oo -200 -300 -400 Transfer (m)Fig. 19 Turning Trajectories with Drift Correction
Measuring techniques of jet velocity, gross thrust and impeller torque for the waterjet system are presented. And the results of sea trial test show a similar behavior to those of the model test. The motion control techniques applied to the test ship and quite satisfactory results were obtained through the sea trial tests.
According to this series of development procedure, some required technologies to develop the cargo vessel of hy-brid type are :
- Lightening and improving the estimation methods of ship weight are necessary because the large angle of the
control fin flap cause the increase of the ship resistance. It is required to improve the estimation accuracy of light weight and gravity center in order to reduce the moving angle of control fins.
It is needed to develop the strut section of the spray suppression since most of wave resistance is due to the spray of side strut,
- Fore-body of upper hull has to get the wide waterplane area in the point of rising and handing on the surface. - It is needed to develop the exclusive loading and
un-loading system for the rapid transportation of shipping containers.
Acknowledgement
The research project reported here has been funded by the Ministry of Science and Technology, Korea, which is gratefully acknowledged.
References
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