Maneuverability characteristics of ships with a single-cpp and their control

Transcription

1 Maneuverability characteristics of ships with a single-cpp and their control during in-harbor ship-handlinghandling Hideo YABUKI Professor, Ph.D., Master Mariner Tokyo University of Marine Science and Technology Contents 1. Introduction. Comparative full-scale experiments between CPP & FPP using 5,88 G.T. training ship.1 Coasting tests. Stopping tests 3. Simulation studies 3.1 Stopping motion prediction 3. Estimation of the critical range of stopping maneuver 3.3 Effective stopping maneuver for berthing under windy condition 3.4 Steering control of CPP ships during stopping maneuver (c) 1 Hideo YABUKI 1

2 1. Introduction CPP (Controllable Pitch Propeller) and FPP (Fixed Pitch Propeller) Highly skewed CPP Conventional FPP Maneuverability characteristics of ships with CPP advantage FPP; thrust is controlled by changing the engine revolution &i its rotating direction. i (When the propeller is turned astern while rotating to ahead, the engine must be stopped & re-started in reverse with compressed air. ) CPP; pitch & thrust are controlled by rotating the blades about their length axis using a hydraulic servomotor installed in the boss. (allows for the engine to work in a constant direction) CPP can provide smooth speed control. (c) 1 Hideo YABUKI

3 Maneuverability characteristics of ships with CPP difficulties 1. During coasting maneuver of ships with CPP pitch feathered to zero, the control of head turning motion by steering is difficult especially under windy condition.. During stopping maneuver of CPP ships, their turning motion is less stable than that of FPP ships particularly under windy condition and it is difficult to control their head turning motion by steering. Coasting; proceed with the ship s inertia with the engine stopped (without ahead propulsion) Topics Results of full-scale experiments to investigate the maneuverability characteristics of ships with CPP 1. Turning motion during the coasting maneuver. Stopping motion under windy condition. Results of the simulation study to develop the in-harbor ship-handling method of CPP ships 1. Method to estimate the critical range of stopping maneuver without t tug assistance.. Effective stopping maneuver for berthing under windy condition. 3. Control of stopping motion by maximum rudder angle steering. (c) 1 Hideo YABUKI 3

4 . Comparative full-scale experiments between CPP & FPP using 5,88 G.T. training ship.1 Coasting tests (1) Course keeping tests at coasting with propeller pitch zero operation () Course keeping tests at coasting with MHP (minimum ahead pitch ) operation. Stopping tests (1) with CPP () with FPP MHP; smallest blade angle of CPP for ahead propulsion which ensures adequate steerage Test ship Principal Particulars Hull Rudder (Flap Rudder) Length: Lpp (m) 15. Ar ( m ) 1.34 Breadth: B (MLD, m) 17.9 Ar/Ld 1/63.4 Depth: D (MLD, m) 1.8 Aspect Ratio Cb.5186 draft: d (m) Propeller (CPP) 5,884 G.T. Training Ship with CPP Prop. Brade No. 4 & Direct reversing system Prop. Dia.: Dp (m) 4.7 for Diesel Engine 1.5 P.R. (Brade Angle) (5.5 ) (c) 1 Hideo YABUKI 4

5 . Coasting tests Coasting with the propeller pitch zero operation The ship turns her head into the wind even though the wind is very weak. The head turning motion can t be controlled by steering U (knots), Ψ, CPP (deg.) Pitch Zero U CPP δ Ψ Wind : 1 (m/s) (deg.) δ ( CPP blades at the propeller pitch zero operation Ast. Pitch (Tip) Ahead Pitch (Boss) Generation of unstable flow Reduction of steering ability (c) 1 Hideo YABUKI 5

6 CPP pitch distribution at Propeller pitch zero operation (stop) Pitch zero operation Tip; Pitch changes to the reverse side Boss; Advance pitch remains Generation of unstable flow Reduction of steering ability Coasting with MHP operation MHP; smallest blade angle of CPP for ahead propulsion which ensures adequate steerage.) U (kn nots), Ψ, CPP (deg Ψ CPP U δ Wind : 5~6 (m/s) MHP The ship can keep her original course under strong wind by applying the appropriate helm. The head turning motion can be controlled sufficiently by steering δ (deg.) (c) 1 Hideo YABUKI 6

7 . Stopping tests (1) Indexes for expressing the stopping ability G Y X Stopping time t = t / (Lpp/U ) U ; Initial speed Stopping distance (Track reach) S = S / Lpp X = X / Lpp ; Head Reach Y = Y / Lpp ; Side Reach Ψ ; Final Heading Angle Ψ Lpp ; Length between Perpendiculars Initial Advancing Constant J S Stopping ability can be expressed as the function of J S where u n D p J /( ) S u n p or J /( ) S u n D ; initial speed (1) () ; astern revolution ; propeller diameter ; propeller pitch (nominal pitch)* * for CPP, effective pitch is used instead of nominal pitch (c) 1 Hideo YABUKI 7

8 CPP effective pitch calculation Effective pitch at pitch angleα, radius r 1 1 P P () r W () x dx / W () x dx C W ( x ) ( x C ) 1 x C (1) P () r r tan( () r ) () r ; standard pitch angle at radius r x ( r/ R) ; non-dimensional radius C ; Boss ratio ; pitch at pitch angleα, radius r Effective pitch of the test ship Blade Angle (deg.) Pitch Ratio -5.5 (D. Slow Ast.) (Slow Ast.) (Half Ast.) (Full Ast.) () Results of full-scale stopping tests for various combination of advance speed & astern operation J S u /( n p ) ( i.e., Initial Advancing Constant ) Condition CPP FPP Wind (m/s) 1~4 ~6 Wave (m). 3.3 df (m) da (m) Trim (m).3 B/S.34 B/S Displacement (ton) 5,955 5,91 (c) 1 Hideo YABUKI 8

9 (i) Crash Stop Astern Comparison.5kts to Full Ast. t S X Y Ψ FPP CPP (ii) Comparison of Astern Maneuver at Low Speed 4 kts to Full Ast. J S t S X Y Ψ FPP CPP (c) 1 Hideo YABUKI 9

10 CPP FPP t 16 (iii) Comparison of stopping ability Stopping distance CPP FPP S' Jso Stopping time t & S of CPP ships are shorter than those of FPP ships Jso Difference of the reversing operation between FPP and CPP n ; maneuvering speed n ; reversible (c) 1 Hideo YABUKI 1

11 C P P Right turn Left turn Ψ(deg.) Wind ; Starb'd Bow Wind ; Port Bow Helm ; +35 Helm ; (iv) Comparison of the final head turning angle between FPP & CPP F P P Wind ; Starb'd Bow Wind ; Port Bow Helm ; +35 Helm ; -35 Ψ(deg.) 1 8 Jso Turning motion of CPP ship is less stable than that of FPP ship. As to CPP ship, control of the turning motion direction by steering is difficult & the direction seems to be fixed by the relative wind direction. -8 R L Jso Shifting Process to Reversing Thrust FPP CPP Short transition time from propeller idling to reversing Need some transition time for attaining the ordered reverse pitch (c) 1 Hideo YABUKI 11

12 CPP pitch distribution at astern blade angle Astern operation Small advance pitch remains near the Boss Generation of unstable flow Unstable turning motion 3. Simulation studies 3.1 Stopping motion prediction MMG type Mathematical model Vw u U Ψw v Coordinate system U u v 1 tan ( v/ u) (c) 1 Hideo YABUKI 1

13 m mu mvr X mv mur Y MMG type Mathematical model X X X X X H P R W (1) Y Y Y Y Y () H P R W zz N N NH NP NR NW I r m ; mass of ship I zz ; moment of inertia of ship in yaw motion uvr,, ; axial velocity, lateral velocity, rate of turn The terms X, Y and N represent the hydrodynamic forces and moment. The subscripts H, P and W refer to the hull, propeller and wind force respectively. Hydrodynamic derivatives & coefficients were obtained by captive model tests Model ; 4.9 m (1 / 4.48) Model Propeller Model ship (stern) Model ship (bow) Rudder Propeller Bow thruster (c) 1 Hideo YABUKI 13

14 captive model tests Force & moment induced by propeller Propeller backing force X P, J P P X t n D K J 4 (1 ) (, ) P p T P P J U /( n D ) P P P ; blade angle, propeller advance coefficient K,, tnd,,, T P UP ; thrust coefficient, rate of thrust deduction, propeller revolution, propeller diameter, propeller advance speed, water density (c) 1 Hideo YABUKI 14

15 lateral force Y P, moment N P Y Ld np Y J p p ' ( /) ( ) (, p) N Ld np N J ' ( /) ( ) (, p) J U / np Ld,, p ; length between perpendiculars, mean draft, propeller pitch Lateral force & moment exerted by reversing propeller (n>, P = ) Y/(1/ /ρld(np) ) N/(1/ρL d(np) ) J=U/nP J=U/nP (c) 1 Hideo YABUKI 15

16 Wind forces & moment X Y ( /) A C U W a T X R ( /) A C U W a S Y R N ( /) A LC U W a S N R C, C, X Y C N ; wind force coefficients and moment, U, L ; air density, relative wind velocity, ship s length a R A, A T S ; longitudinal projected area of hull and transverse projected area of hull above water line Wind forces & moment Wind tunnel test (Model ; 1.5 m ) Cx With Rough Board Relative Wind Direction(deg.) (c) 1 Hideo YABUKI 16

17 Cy Cn Wind force & moment With Rough Board Relative Wind Direction(deg.) Validation of stopping motion prediction 4 knots to Slow Ast. 1 Y's Simulated Measured -1 Ψ [deg] U [m/s] Right beam wind 9 m/s 1 Right Wind 9 m/s 4 Knots, Slow Ast. X's 3 3 U Ψ Sec (c) 1 Hideo YABUKI 17

18 Stopping motion prediction under windy condition (3 knots, Slow Ast.) Xs/Lpp Wind Direction(deg.) 7 m/s 1 m/s 15 m/s m/s Head Reach Ψ(deg.) Head Turning Angle Side Reach Wind direction (deg.) Ys/B 7 m/s 1 m/s 15 m/s m/s (c) 1 Hideo YABUKI 18

19 3. Estimation of the critical range of stopping maneuver under windy condition Typical shiphandling fordocking 1.5 B Critical range of stopping maneuver Ys/B>1.5 Ψ>º º B ; ship s breadth Ys/B Critical Range Ys/B>1.5 Ψ>º Ψ(deg.) Critical range of stopping maneuver Wind direction (deg.) 7 m/s 1 m/s 15 m/s m/s (c) 1 Hideo YABUKI 19

20 3.3 Effective stopping maneuver under windy condition Difficulty of stopping maneuver in the follow wind Xs / Lpp Head wind 1 m/s 3 knot, Slow Ast. Xs / Lpp Follow wind 1 m/s 3 knot, Slow Ast Ys / Lpp Ys / Lpp Effective stopping maneuver for berthing under windy condition Stopping motion is fixed by apparent advance constant J /( ) S u n p at the initial stage of propeller reversing Stopping motion indexes increase in proportion to J S The size of stopping motion can be reduced by maneuvering so that becomes smaller J S (c) 1 Hideo YABUKI

21 Effective stopping maneuver in the follow wind Xs / Lpp Follow wind 1 m/s 3 knot, Half Ast. Xs / Lpp Head wind 1 m/s 3 knot, Slow Ast Ys / Lpp Ys / Lpp 3.4 Steering control of CPP ships during stopping maneuver (1) Control of stopping motion by maximum rudder angle steering The direction of turning motion of CPP ships seems to be fixed by the yaw moment at the initial stage of propeller reversing. Proposal Application of the head turning moment by the maximum rudder angle steering prior to propeller reversing. (c) 1 Hideo YABUKI 1

22 Effect of the proposed stopping maneuver under windy condition 1 Y's Left wind 1 m/s Left Wind 1 m/s With Rudder Angle +35 Midship Stopping maneuver with the rudder amidships θ U [deg] [deg] Ψ,δ [m/s] 15 3 δ 1 U X's 3 The ship drifts leeward & turns her head into the wind θ Ψ Initial speed 3 kts, Slow astern 1 [sec] 15 Stopping maneuver that applies maximum rudder angle steering to leeward prior to propeller reversing The ship drifts leeward. The yaw moment can be reduced sufficiently. The original heading is well maintained. Y's θ U [deg] [deg] Ψ,δ [m/s] Left wind 1 m/s Left Wind 1 m/s δ 1 U With Rudder Angle +35 Midship θ X's Ψ Initial speed 3 kts, Slow astern 1 [sec] 15 (c) 1 Hideo YABUKI

23 () Application of MHP operation & stopping maneuver with steering control to the anchoring under windy condition Anchoring procedure Approaching Stopping Proceeding on the planned track Reducing speed Controlling ships heading into the wind & tide MHP operation Stopping maneuver with rudder control Laying out anchor Fetching up Result of actual anchoring Proceeded on the planned track with MHP Coasting Hard-starb d steering to windward Yaw moment increased Changed CPP from MHP to Slow ast. directly Ship stopped with her heading to windward PP(deg.) U(Kts), CP MHP Trajectory Slow ast. Ψ CPP 166 M inimum Ahead 1614 Slow Astern U 1615 Let go anchor d 161 H ard-a-starb'd +35 steering Time history deg.) d, Ψ ( (c) 1 Hideo YABUKI 3

24 (3) Application to the crash stop astern maneuver Crash stop astern maneuver To stop the ship with the shortest distance To turn the ship s head to the starb d as great as possible Full astern operation Hard starb d steering Put the propeller to full astern after applying the starb d head turning moment by the maximum rudder angle steering. Crash ast. with rudder amidships Y's 1 Midship Starboard 35 Ship stopped turning her head slightly to starb d -1 on the original track Both Ψ & Y s are not enough to avoid collision X's 4 θ Ψ,δ U [deg] [deg] [m/s] 15 3 δ U Ψ Crash ast. with +35 steering Both sufficient Ψ & Y s to avoid collision are obtained θ 6 9 [sec] Initial speed 6kts, Full ast., Calm 1 (c) 1 Hideo YABUKI 4

25 Crash ast. Maneuver under windy condition Initial speed 6kts, Full ast. Wind 1 m/s X s Head wind wind 1 m/s X s Tail wind Tail wind 1 m/s Midship Rudder +35 Midship midships Rudder midships +35 Y s Both sufficient Ψ & Y s to avoid collision are obtained. Y s X s Left wind Left beam wind 1 m/s X s Right wind Right beam wind 1 m/s Midship Rudder +35 Midship Rudder +35 midships +35 midships +35 Y s Both sufficient Ψ & Y s to avoid collision are obtained. Y s (c) 1 Hideo YABUKI 5

26 Thank you for your attention. The test ship T.S. Seiun Maru (c) 1 Hideo YABUKI 6