A portal rudder having a left rudder and a right rudder arranged on both sides of the propeller of the ship

Abstract

Provided is a portal rudder capable of reducing energy consumption of a ship during navigation. In a portal rudder having a pair of rudders consisting of a left rudder and a right rudder arranged on both sides of a propeller at a stern, the rudder is formed by a first rudder portion extending in the left-right direction and a second rudder portion extending in a straight line in the up-down direction when viewed from the rear, the rudder chord length of the second rudder portion in the front-back direction is formed to be 40% to 100% of the diameter of the propeller, the propeller is arranged between 15% and 65% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side, and the rudder shaft driving the rudder is arranged at a position of 30% to 50% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side.

Description

Technical Field

[0001] The present invention relates to a portal rudder having a left rudder and a right rudder arranged on both sides of a propeller provided at a stern of a ship. Background Art

[0002] In the past, the following portal rudder technology is known: a left rudder and a right rudder are provided on both sides of a propeller installed at the stern of a ship, with a predetermined interval in the front-rear direction and extending in the front-rear direction, and when the ship is stopped, the left rudder and the right rudder are moved to the rear of the propeller (Patent Document 1).

[0003] In order to accelerate the jet flow ejected from the propeller, there is known a technology of a ducted propeller having a left rudder and a right rudder formed in an arc shape along the outer circumference of the propeller on both sides of the propeller (Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5833278

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 1-501384 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, the technology of Patent Document 1 has the following problems: when the ship is moving straight, sufficient steering force due to the Coanda effect or the upper surface blowing (hereinafter referred to as USB) effect of the high lift device used for aircraft cannot be obtained, and the energy consumption of the ship during navigation cannot be fully reduced. In addition, due to the particularity of steering behind the propeller, a large torque is generated, and although the area is smaller than before, the capacity of the steering gear is substantially the same as before.

[0010] Furthermore, in the technology of Patent Document 2, the clearance between the propeller and the left and right rudders is set small in order to improve the efficiency of the propeller, so there is a problem that cavitation is likely to occur inside the left and right rudders.

[0011] Therefore, the main problem of the present invention is to provide a gate rudder that can reduce the energy consumption of a ship during navigation. In addition, the secondary problem of the present invention is to provide a gate rudder that can suppress the generation of cavitation generated on the inner surface of the left and right rudders. Furthermore, the capacity of the steering gear is optimized to a size that matches the smaller rudder area.

[0012] Means for solving problems

[0013] The present invention which solves the above-mentioned problems is as follows.

[0014] The invention of technical solution 1 is a portal rudder, which has a pair of rudders consisting of a left rudder and a right rudder arranged on both sides of a propeller at the stern, characterized in that, when viewed from the rear, the rudder is formed by a first rudder portion extending in the left-right direction and a second rudder portion extending in a straight line in the up-down direction, and the rudder chord length of the second rudder portion in the front-to-back direction is formed to be 40% to 100% of the diameter of the propeller, when viewed from the side, the propeller is set between 15% and 65% of the rudder chord length from the leading edge of the second rudder portion, and when viewed from the side, the rudder shaft that drives the rudder is set at a position of 30% to 50% of the rudder chord length from the leading edge of the second rudder portion.

[0015] The invention of claim 2 is the portal rudder according to claim 1, wherein the rudder shaft driving the rudder is provided at a position of 35% to 45% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side.

[0016] The invention according to claim 3 is the portal rudder according to claim 1 or 2, wherein the gap between the propeller and the second rudder portion is formed to be 4% to 10% of the diameter of the propeller when viewed from behind.

[0017] The invention of claim 4 is a portal rudder according to any one of claims 1 to 3, wherein a torsion angle is formed at the second rudder portion, and an upper torsion angle formed at the upper portion of the second rudder portion is formed to be larger than a lower torsion angle formed at the lower portion of the second rudder portion.

[0018] The invention according to claim 5 is the portal rudder according to claim 4 , wherein the upper torsion angle is formed to be greater than or equal to 3 degrees, and the lower torsion angle is formed to be less than or equal to 5 degrees.

[0019] The invention according to claim 6 is the portal rudder according to any one of claims 1 to 5, wherein when the ship is stopped, the second rudder is steered forward.

[0020] Effects of the Invention

[0021] According to the invention described in technical solution 1, when viewed from the rear, a rudder is formed by a first rudder portion extending in the left-right direction and a second rudder portion extending in a straight line in the up-down direction, and a rudder chord length of the second rudder portion in the front-to-back direction is formed to be 40% to 100% of the diameter of the propeller. When viewed from the side, the propeller is arranged between 15% and 65% of the rudder chord length from the leading edge of the second rudder portion. When viewed from the side, a rudder shaft driving the rudder is arranged at a position between 30% and 50% of the rudder chord length from the leading edge of the second rudder portion. Therefore, when the ship is moving straight, a larger rudder force caused by the wall effect generated in the front part of the second rudder portion of the rudder and a larger rudder force caused by the USB effect generated in the rear part can generate a larger thrust to move the ship forward, thereby reducing the energy consumption of the ship during navigation, and also minimizing the rudder torque.

[0022] According to the invention described in technical solution 2, in addition to the inventive effects described in technical solution 1, the rudder shaft for driving the rudder is arranged at a position of 35% to 45% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side. Therefore, when the second rudder portion is steered forward, a larger rudder force can be generated and the rudder torque can be further minimized.

[0023] According to the invention recorded in technical solution 3, in addition to the inventive effects recorded in technical solution 1 or 2, the gap between the propeller and the second rudder portion is formed to be 4% to 10% of the diameter of the propeller when observed from the rear, so that the larger steering force caused by the USB effect generated at the rear of the second rudder portion can be maintained, and the occurrence of cavitation on the inner surface of the second rudder shaft can be prevented.

[0024] According to the invention recorded in technical solution 4, in addition to the inventive effects recorded in any one of technical solutions 1 to 3, a torsion angle is formed at the second rudder portion, and an upper torsion angle formed at the upper part of the second rudder portion is formed to be larger than a lower torsion angle formed at the lower part of the second rudder portion. Therefore, a greater thrust can be generated at the upper part of the second rudder portion opposite to a shallower draft portion of the ship where the flow velocity of the suction flow flowing into the propeller is faster, thereby further reducing the energy consumption of the ship during navigation.

[0025] According to the invention recorded in technical solution 5, in addition to the inventive effects recorded in any one of technical solutions 1 to 4, the upper torsion angle is formed to be greater than 3 degrees, and the lower torsion angle is formed to be less than 5 degrees. Therefore, it is possible to reduce the energy consumption during navigation from skinny ships such as container ships to fat ships such as tankers.

[0026] According to the invention recorded in technical solution 6, in addition to the invention effects recorded in any one of technical solutions 1 to 4, when the ship stops, the second rudder is steered forward, so when the ship stops, the stopping distance of the ship can be shortened by the larger rudder force generated by the second rudder. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a perspective view of a door rudder with port and star rudders on either side of the propeller.

[0028] Figure 2 It is the left side view of the door rudder.

[0029] Figure 3 It is the right side view of the door rudder.

[0030] Figure 4 It is the area of ​​the rudder covered by the propeller wake when the rudder angle is obtained when the rudder shaft is provided at a position 30% (Cp=0.3) of the rudder chord length from the leading edge of the rudder (the percentage relative to the whole).

[0031] Figure 5 It is the area (percentage relative to the whole) of the rudder covered by the propeller wake when the rudder angle is obtained when the rudder shaft is provided at a position 50% (Cp=0.5) of the rudder chord length from the leading edge of the rudder.

[0032] Figure 6 It is the area (percentage relative to the whole) of the rudder covered by the propeller wake when the rudder angle is obtained when the rudder shaft is provided at a position 70% (Cp=0.7) of the rudder chord length from the leading edge of the rudder.

[0033] Figure 7 This is the measured value of the steering force center position when the steering angle is operated from 0 to 60 degrees.

[0034] Figure 8 It is the rear view of the door rudder.

[0035] Fig. 9 This is the measured value of the steering force when steering from the forward steering angle to the rearward steering angle.

[0036] Fig.10 This is a simulation of the optimum clearance between the propeller and the door rudder when Cp = 0.3 and Cp = 0.5.

[0037] Fig.11 It is the measured value of the normal rudder of the rotational angular velocity when the ship turns.

[0038] Fig.12 It is the measured value of the angular velocity of the rudder when the ship is turning.

[0039] Fig.13 It is a top view of the door rudder.

[0040] Fig.14 (a) is the left side view of the port rudder of the door rudder. Fig.14 (b) is a cross-sectional view of the upper part of the left rudder. Fig.14 (c) is a cross-sectional view of the lower part of the left rudder. Fig.14 (d) is an illustration of the torsion angle of the left rudder.

[0041] Fig.15 (a) is the right side view of the starboard rudder of the door rudder. Fig.15 (b) is a cross-sectional view of the upper part of the right rudder. Fig.15 (c) is a cross-sectional view of the lower part of the right rudder. Fig.15 (d) is an illustration of the torsion angle of the right rudder.

[0042] Fig.16 The resistance value is measured when a model ship equipped with a normal rudder and a gate rudder is sailed at an oblique angle of 0 to 10 degrees.

[0043] Fig.17 It is the measured value of the rudder lateral force when a model ship equipped with a normal rudder and a portal rudder is sailed at an oblique angle of 0 to 10 degrees.

[0044] Fig.18 (a) is a simulation of the door rudder that does not form a twist angle due to the disturbance of the flow field of the attraction flow. Fig.18 (b) is a simulation of a gate rudder with a twist angle formed by the disturbance of the flow field of the attraction flow. DETAILED DESCRIPTION

[0045] like Figure 1 As shown, the rudder (hereinafter referred to as a gate rudder) of the present embodiment is formed by a left rudder 2A and a right rudder 2B arranged on both sides of a propeller 1 of a ship.

[0046] The left rudder 2A is formed by a first left rudder portion 5A extending in the left-right direction and a second left rudder portion 6A extending downward from the left end of the first left rudder portion 5A. In addition, the left end of the first left rudder portion 5A and the upper part of the second left rudder portion 6A can also be connected by an inclined or gently curved connecting portion (not shown).

[0047] A left rudder shaft 10A extending in the up-down direction is fixed to the right portion of the first left rudder portion 5A, the upper portion of the left rudder shaft 10A extends into the engine room of the ship, and a left steering gear (not shown) for steering the left rudder shaft 10A is connected to the upper portion of the left rudder shaft 10A.

[0048] Similarly, the right rudder 2B is formed by a first right rudder portion 5B extending in the left-right direction and a second right rudder portion 6B extending downward from the right end of the first right rudder portion 5B. In addition, the left end of the first left rudder portion 5A can be connected to the upper part of the second left rudder portion 6A by an inclined, gently curved connecting portion (not shown).

[0049] A right rudder shaft 10B extending in the up-down direction is fixed to the left portion of the first right rudder portion 5B, the upper portion of the right rudder shaft 10B extends into the engine room of the ship, and a right steering gear (not shown) for steering the right rudder shaft 10B is connected to the upper portion of the right rudder shaft 10B.

[0050] In addition, in this specification, the left rudder 2A and the right rudder 2B are collectively referred to as the rudder 2, the first left rudder portion 5A and the first right rudder portion 5B are collectively referred to as the first rudder portion, the second left rudder portion 6A and the second right rudder portion 6B are collectively referred to as the second rudder portion 6, and the left rudder shaft 10A and the right rudder shaft 10B are collectively referred to as the rudder shaft.

[0051] <Chord length of the second rudder>

[0052] like Figure 2As shown, the left rudder chord length CA of the second left rudder portion 6A is preferably formed to be 40% to 100% of the diameter D of the propeller 1, similarly to the duct length of the ducted propeller. Thus, the second left rudder portion 6A can efficiently obtain the steering force.

[0053] In addition, the propeller 1 is arranged between 15% and 65% of the left rudder chord length CA from the front end portion of the second left rudder portion 6A, that is, the front end portion E of the blade portion of the propeller 1 is arranged at a position farther back than 15% of the left rudder chord length CA from the front end portion of the second left rudder portion 6A, and the rear end portion F of the blade portion of the propeller 1 is arranged at a position farther forward than 65% of the left rudder chord length CA from the front end portion of the second left rudder portion 6A.

[0054] Likewise, if Figure 3 As shown in FIG. 1 , it is preferable that the right rudder chord length CB of the second right rudder portion 6B is formed to be 40 to 100% of the diameter D of the propeller 1. Thus, the steering force can be efficiently obtained from the second right rudder portion 6B.

[0055] In addition, the propeller 1 is arranged between 15% and 65% of the right rudder chord length CB from the front end portion of the second right rudder portion 6B, that is, the front end portion E of the blade portion of the propeller 1 is arranged at a position farther back than 15% of the right rudder chord length CB from the front end portion of the second right rudder portion 6B, and the rear end portion F of the blade portion of the propeller 1 is arranged at a position farther forward than 65% of the right rudder chord length CB from the front end portion of the second right rudder portion 6B.

[0056] In addition, in this specification, the left rudder chord length CA and the right rudder chord length CB are collectively referred to as the rudder chord length C.

[0057] <Rudder shaft arrangement>

[0058] The left steering shaft 10A is preferably provided at 30% to 50% of the left steering chord length CA of the second left steering portion 6A from the leading edge of the second left steering portion 6A, and the right steering shaft 10B is preferably provided at 30% to 50% of the right steering chord length CB of the second right steering portion 6B from the leading edge of the second right steering portion 6B. In addition, in order to generate a large steering force during forward steering, the left steering shaft 10A is preferably provided at 35% to 45% of the left steering chord length CA of the second left steering portion 6A from the leading edge of the second left steering portion 6A, and the right steering shaft 10B is more preferably provided at 35% to 45% of the right steering chord length CB of the second right steering portion 6B from the leading edge of the second right steering portion 6B. In this way, the torque for steering the left rudder shaft 10A and the right rudder shaft 10B can be reduced. In addition, as described later, when the ship is stopped, the reduction in the steering force at the rear of the second left rudder portion 6A and the second right rudder portion 6B extending rearward than the propeller 1 when the ship is moving straight can be suppressed.

[0059] The steering force F generated at the rear of the second rudder portion 6 extending rearward of the propeller 1 is NThe rudder force F generated at the rear portion of the second rudder portion 6 outside the jet flow of the propeller 1 can be N1 and the rudder force F generated at the rear portion of the second rudder portion 6 in the jet flow of the propeller 1. N2 Substitute into equation 1 to calculate.

[0060] ◎

Mathematical formula 1

[0061] F N =F N1 ·(1-μ)+μ·F N2

[0062] F in formula 1 N1 It can be calculated according to Mathematical Formula 2.

[0063] ◎

Mathematical formula 2

[0064]

[0065] Here, ρ is the density, U R1 is the speed at the rudder position, A R is the area of ​​the rear portion of the second left rudder portion 6A extending rearward from the propeller 1, C L1 is the lift coefficient.

[0066] U in mathematical formula 2 R1 It can be calculated according to Mathematical Formula 3.

[0067] ◎

Mathematical formula 3

[0068] U R1 2 =u R2 + v R 2

[0069] Here, u R1 is the propeller axial component of velocity, v R is the circumferential component of velocity.

[0070] C in Math 2 L1 It can be calculated according to Mathematical Formula 4.

[0071] ◎

Mathematical formula 4

[0072]

[0073] Here, λ is the aspect ratio of the rudder and δ is the rudder angle.

[0074] F in formula 1 N2 It can be calculated according to Mathematical Formula 5.

[0075] ◎

Mathematical formula 5

[0076]

[0077] Here, ρ is the density, U R2 is the speed at the rudder position, A R is the area of ​​the rear portion of the second rudder portion 6 extending rearward from the propeller 1, C L2 is the lift coefficient.

[0078] Mathematical formula 5 U R2 It can be calculated according to Mathematical Formula 6.

[0079] ◎

Mathematical formula 6

[0080] U R2 2 =u R2 2 +v R 2

[0081] Here, u R2 is the propeller axial component of velocity, v R is the circumferential component of velocity.

[0082] Math 5 C L2 It can be calculated according to Mathematical Formula 7.

[0083] ◎

Mathematical formula 7

[0084]

[0085] Here, λ is the aspect ratio of the rudder and δ is the rudder angle.

[0086] μ in Formula 1 can be calculated according to Formula 8.

[0087] ◎

Mathematical formula 8

[0088]

[0089] Here, A CV is the area of ​​the rear portion of the second rudder portion 6 located in the jet of the propeller 1, and A R is the area of ​​the rear portion of the second rudder portion 6 extending rearward from the propeller 1, and η is the ratio of the diameter D of the propeller 1 to the height H of the rudder 2 (D / H).

[0090] like Figures 4 to 6 As shown in FIG. 2 , when the rudder shaft 10 is provided at a position rearward of 50% (Cp=0.5) of the chord length C of the second rudder portion 6 from the leading edge of the second rudder portion 6 (for example, Cp=0.7), the area A of the rear portion of the second rudder portion 6 extending rearward from the propeller 1 in equations 2 and 5 is RAs a result, it is possible that the rudder force F generated by the jet of the propeller 1 at the rear of the second rudder portion 6 extending rearward of the propeller 1 N Therefore, in order to generate a predetermined steering force F at the rear of the second rudder portion 6 extending rearward from the propeller 1, N The rudder shaft 10 is preferably arranged at a position less than 50% of the chord length C of the second rudder portion 6 from the leading edge of the second rudder portion 6. Figures 4 to 6 In FIG. 1 , the area of ​​the rear portion of the second rudder portion 6 is clearly described as “COVEREDAREA”.

[0091] like Figure 7 As shown in FIG. 1 , when the steering gear is operated to change the steering angle to 0 to 60 degrees, the center position of the steering force (dimensionless value) changes monotonically from 20% to about 40% with the increase of the steering angle in a normal rudder, whereas it decreases from 45% to about 25% and then further increases to about 55% in a gate rudder. Therefore, in order to minimize the maximum steering torque, it is necessary to move the steering axis position from about 30% to about 40%. In addition, Figure 7 , the center position of action of the rudder force (dimensionless value) obtained from the water tank experiment is compared with that of a conventional rudder.

[0092] <Clearance between propeller and rudder>

[0093] like Figure 8 As shown, the left gap TA between the outer circumference L of the propeller 1 and the left inner surface 7A of the second left rudder portion 6A has a great influence on the steering force caused by the wall effect generated at the front part of the second left rudder portion 6A and the steering force caused by the USB effect generated at the rear part of the second left rudder portion 6A. The front part of the second left rudder portion 6A extends forward of the propeller 1 due to the suction flow flowing into the propeller 1 due to the suction force of the propeller 1, and the rear part of the second left rudder portion 6A extends rearward of the propeller 1 due to the jet ejected from the propeller 1.

[0094] Similarly, the right gap TB between the outer circumference L of the propeller 1 and the right inner surface 7B of the second right rudder portion 6B has a greater influence on the steering force caused by the wall effect generated at the front part of the second right rudder portion 6B and the steering force caused by the USB effect generated at the rear part of the second right rudder portion 6B. The front part of the second right rudder portion 6B extends forward of the propeller 1 due to the suction flow flowing into the propeller 1 due to the suction force of the propeller 1, and the rear part of the second right rudder portion 6B extends rearward of the propeller 1 due to the jet ejected from the propeller 1.

[0095] That is, when the left clearance TA and the right clearance TB are smaller than the prescribed clearance, damage caused by cavitation may occur on the inner surfaces of the left and right rudder parts. When the left clearance TA and the right clearance TB are larger than the prescribed clearance, the flow velocities of the suction flow and the jet may become low, the wall effect and the USB effect may be reduced, and the rudder force may become smaller.

[0096] In the present specification, the left inner surface 7A and the right inner surface 7B are collectively referred to as the inner surface 7 , and the left gap TA and the right gap TB are collectively referred to as the gap T.

[0097] like Fig. 9 As shown, in the case of the left rudder 2A, the steering force generated when the left rudder shaft 10A is steered toward the -rudder angle (forward steering angle) so that the front part of the second left rudder portion 6A is located on the right side of the front than the rear part is greater than the steering force generated when the left rudder shaft 10A is steered toward the +rudder angle (rear steering angle) through the flap effect caused by the interference between the stern and the second left rudder portion 6A so that the front part of the second left rudder portion 6A is located on the left side of the front than the rear part.

[0098] Similarly, in the case of the left rudder 2B, the steering force generated when the right rudder shaft 10B is steered toward the -rudder angle so that the front part of the second right rudder portion 6B is located on the left side of the front relative to the rear part is greater than the steering force generated when the right rudder shaft 10B is steered toward the +rudder angle so that the front part of the second right rudder portion 6B is located on the right side of the front relative to the rear part due to the flap effect caused by the interference between the stern of the ship and the second right rudder portion 6B.

[0099] In addition, if Fig.13 As shown, the -steering angle of the left steering shaft 10A is the steering angle for steer the left steering shaft 10A forward in the clockwise direction, the +steering angle of the left steering shaft 10A is the steering angle for steer the left steering shaft 10A backward in the counterclockwise direction, the -steering angle of the right steering shaft 10B is the steering angle for steer the right steering shaft 10B forward in the counterclockwise direction, and the +steering angle of the right steering shaft 10B is the steering angle for steer the right steering shaft 10B backward in the clockwise direction.

[0100] On the other hand, if the -rudder angle of the left rudder shaft 10A is excessively steered, so that the front part of the second left rudder portion 6A is too close to the stern, the flow field of the suction flow flowing into the propeller 1 is disturbed, and cavitation that causes vibration or noise may increase. Therefore, it is preferable to set the maximum steering angle of the -rudder angle of the left rudder shaft 10A to 15 degrees, which can obtain the same steering force as the steering force generated when steering 25 degrees to the +rudder angle. In addition, the rotation angle of the left rudder shaft 10A can be set arbitrarily, but in the present embodiment, the -rudder angle is set to a rotation angle of 0 to 15 degrees, and the +rudder angle is set to a rotation angle of 0 to 105 degrees.

[0101] Similarly, if the right rudder shaft 10B is steered excessively at the - rudder angle, so that the front part of the second right rudder portion 6B is too close to the stern, the flow field of the suction flow flowing into the propeller 1 is disturbed, and there is a possibility that cavitation, which is a cause of vibration or noise, will increase. Therefore, it is preferable to set the maximum steering angle of the - rudder angle of the right rudder shaft 10B to 15 degrees, which can obtain the same rudder force as that generated when steering 25 degrees to the + rudder angle. In addition, the rotation angle of the right rudder shaft 10B can be set arbitrarily, but in the present embodiment, the - rudder angle is set to a rotation angle of 0 to 15 degrees, and the + rudder angle is set to a rotation angle of 0 to 105 degrees.

[0102] When stopping the ship, by steering the left rudder shaft 10A to a negative rudder angle of 15 degrees and steering the right rudder shaft 10B to a negative rudder angle of 15 degrees, the water flow from the front of the hull that promotes the idling of the propeller can be cut off, and the inertia force of the propeller can be reduced. Therefore, it is easy to shift to a reverse rotation state, especially in the case of an FPP (fixed pitch propeller), and the stopping performance and reverse performance can be improved.

[0103] The clearance T between the outer peripheral line L of the propeller 1 and the inner surface 7 of the second rudder portion 6 can be calculated according to Mathematical Formula 9.

[0104] ◎

Mathematical formula 9

[0105]

[0106] Here, Rp is the rotation radius of the second rudder portion 6, Cp is the value obtained by dividing the length of the leading edge of the second rudder portion 6 and the rudder axis 6 by the rudder chord length C when viewed from the side (set to 0.3 to 0.5 in the present embodiment), and ψ is the steering axis of the -rudder angle of the rudder axis 10 (set to 15 degrees in the present embodiment).

[0107] like Fig.10 As shown, when Cp=0.3 is substituted into the mathematical formula 9, the value obtained by dividing the chord length C of the second rudder portion 6 by the diameter D of the propeller 1 is increased to 0.4 to 0.7, and the gap T calculated is 0.04D to 0.06D. When Cp=0.5 is substituted into the mathematical formula 9, the value obtained by dividing the chord length C of the second rudder portion 6 by the diameter D of the propeller 1 is increased to 0.4 to 0.7, and the gap T calculated is 0.06D to 0.1D. Therefore, it is preferable that the gap T between the outer peripheral line L of the propeller 1 and the inner surface 7 of the second rudder portion 6 is formed to be 4% to 10% of the diameter D of the propeller 1.

[0108] Thus, when the ship is traveling straight, a large rudder force due to the Coanda effect is generated at the front of the second left rudder portion 6A extending forward from the propeller 1 by the suction flow flowing into the propeller 1, and a large rudder force due to the USB effect is generated at the rear of the second left rudder portion 6A extending rearward from the propeller 1 by the jet flow ejected from the propeller 1, so that a large thrust (lift) for moving the ship forward can be generated. In addition, by forming a gap T larger than the gap of the ducted propeller, that is, 0.03D, the generation of cavitation generated at the front of the inner surface A of the second rudder portion 6 can be prevented.

[0109] like Fig.11 and Fig.12 As shown, a conventional rudder installed behind a propeller, especially behind a CPP (variable pitch propeller), has a tendency for the ship's rotational force (rotational angular velocity) to stall when the steering angles of - and + rudder angles are 20 degrees or more. On the other hand, even if the steering angles of - and + rudder angles are 20 degrees or more, the gate rudder can maintain an increasing tendency without stalling the rotational force (rotational angular velocity) corresponding to the rudder angle. In addition, Fig.11 In the figure, the gate rudder of the present embodiment is referred to as “Gate Rudder”, and the normal rudder is referred to as “Flap Rudder”. The horizontal axis represents the rudder angle, and the vertical axis represents the rotational angular velocity.

[0110] like Fig.12 As shown in FIG. 1 , in a plan view, the second left rudder portion 6A is formed by an airfoil that is formed by a warping curve (cambered curve) that connects the center of the second left rudder portion 6A in the width direction and has a bulge on the propeller side. As a result, lift is generated particularly toward the front propeller side, and the suction flow caused by the propeller 1 generated on the leading edge side of the inner surface 7A of the second left rudder portion 6A produces a Coanda effect, which can increase the lift and the corresponding rudder force.

[0111] Similarly, in a plan view, the second right rudder portion 6B is formed by an airfoil that is formed by a warp curve (cambered curve) that connects the center of the second right rudder portion 6B in the width direction and has a bulge on the propeller side. As a result, lift is generated particularly toward the front propeller side, and the suction flow caused by the propeller 1 generated on the leading edge side of the inner surface 7B of the second right rudder portion 6B produces a Coanda effect, which can increase the lift and the corresponding rudder force.

[0112] <Twist angle>

[0113] like Fig.14As shown, on the second left rudder portion 6A, a left torsion angle αA is formed in such a manner that the front portion of the second left rudder portion 6A is located to the left of the imaginary line in the front-rear direction, and the rear portion of the second left rudder portion 6A is located to the right of the imaginary line in the front-rear direction. As a result, the suction flow flowing into the propeller 1 and the jet flow ejected from the propeller 1 can flow at a predetermined angle of attack relative to the rudder chord line of the second left rudder portion 6A, so the second left rudder 6A can reduce its resistance and increase its lift. The thrust for propelling the ship forward can be increased. In addition, Fig.12 The second left rudder portion 6A shown forms the torsion angle αA over the entire chord length of the second left rudder portion 6A, but the torsion angle αA may be formed only in the front portion of the second left rudder portion 6A on the front side of the left rudder shaft 10A in a side view.

[0114] The upper left twist angle αA1 of the upper part of the second left rudder portion 6A is formed to be larger than the lower left twist angle αA2 of the lower part of the second left rudder portion 6A. Thus, a larger thrust can be efficiently generated at the upper part of the second left rudder portion 6A facing the shallow draft portion of the ship where the flow velocity is faster such as the ship suction flow which is greatly affected by the suction flow of the propeller, compared with the flow velocity in a state where the propeller is not in operation.

[0115] In addition, Fig.14 In the embodiment, the torsion angle αA is formed over the entire chord length of the second left rudder portion 6A, but the torsion angle αA may be formed only in the front portion of the second left rudder portion 6A on the front side of the left rudder shaft 10A in a side view.

[0116] Likewise, if Fig.15 As shown, on the second right rudder portion 6B, a right torsion angle αB is formed in such a manner that the front portion of the second right rudder portion 6B is located to the right of the imaginary line in the front-rear direction, and the rear portion of the second right rudder portion 6B is located to the left of the imaginary line in the front-rear direction. As a result, the suction flow flowing into the propeller 1 and the jet flow ejected from the propeller 1 can flow at a predetermined angle of attack relative to the rudder chord line of the second right rudder portion 6B, so the second right rudder 6B can reduce its resistance and increase its lift. The thrust for propelling the ship forward can be increased. In addition, Fig.14 The second right rudder portion 6B shown forms the torsion angle αB over the entire chord length of the second right rudder portion 6B, but the torsion angle αB may be formed only in the front portion of the second right rudder portion 6B on the front side of the right rudder shaft 10B in a side view.

[0117] The upper right torsion angle αB1 of the upper part of the second right rudder portion 6B is formed to be larger than the lower right torsion angle αB2 of the lower part of the second right rudder portion 6B. Thus, a larger thrust can be efficiently generated at the upper part of the second right rudder portion 6B which is opposite to the shallower draft portion of the ship where the suction flow of the propeller is more affected, compared with the flow velocity in a state where the propeller is not in operation.

[0118] In this specification, the torsion angle αA and the torsion angle αB are collectively referred to as the torsion angle α, the torsion angle αA1 and the torsion angle αB1 are collectively referred to as the upper torsion angle α1, and the torsion angle αA2 and the torsion angle αB2 are collectively referred to as the lower torsion angle α2.

[0119] In the portal rudder of the present embodiment, the upper torsion angle α1 is formed to be 3 degrees or more, and the lower torsion angle α2 is formed to be 5 degrees or less. In addition, the upper torsion angle α1 and the like are different depending on the shape of the ship. In a thin ship such as a container ship, it is preferable that the upper torsion angle α1 is formed to be 5 degrees, and the lower torsion angle α2 is formed to be 1 degree. In a fat ship such as an oil tanker, it is preferable that the upper torsion angle α1 is formed to be 7 degrees, and the lower torsion angle α2 is formed to be 3 degrees. Therefore, if the relationship between the upper torsion angle α1 and the lower torsion angle α2 is sorted out, it is preferable that the upper torsion angle α1 is formed to be larger than the lower torsion angle α2, and the upper torsion angle α1 is formed to be 3 degrees or more, and the lower torsion angle α2 is formed to be 5 degrees or less.

[0120] like Fig.16 As shown in the figure, when the ship is tilted due to the influence of waves or wind, the rudder resistance of the gate rudder of this embodiment is smaller than that of a normal rudder. In addition, it can be seen that when the tilt angle of the ship is 0 to 9 degrees, the rudder resistance of the gate rudder acts as a thrust to push the ship forward. Therefore, it is clear that when the gate rudder of this embodiment is used, it has the effect of greatly reducing the energy consumption of the ship during navigation. In addition, Fig.16 In the drawings, the portal rudder of the present embodiment is referred to as the rudder of the present invention, and the normal rudder is referred to as the normal rudder.

[0121] like Fig.17 As shown in the figure, it can be seen that when the ship is affected by waves or wind and moves obliquely, the rudder lateral force of the portal rudder of this embodiment, that is, the restoring force that restores the ship to a straight state, is greater than that of a normal rudder. It can be seen that when the portal rudder of this embodiment is used, the ship's directional stability is greatly improved. In addition, Fig.17 In the drawings, the portal rudder of the present embodiment is referred to as the rudder of the present invention, and the normal rudder is referred to as the normal rudder.

[0122] like Fig.18 As shown, it can be seen that the door rudder having the twist angle α formed at the second left rudder portion 6 suppresses the disturbance of the flow field of the suction flow flowing into the propeller 1 compared to the door rudder having no twist angle formed at the second left rudder portion 6. It can be seen from this that there is an effect of preventing the reduction of the flow velocity caused by the turbulence of the suction flow, thereby preventing the reduction of the thrust generated by the door rudder and maintaining a large thrust.

[0123] Industrial Applicability

[0124] The present invention can be applied to a portal rudder having a left rudder and a right rudder arranged on both sides of a propeller of a ship.

[0125] Description of symbols

[0126] 1: propeller; 2: rudder; 2A: left rudder; 2B: right rudder; 5: first rudder section; 6: second rudder section; 10: rudder shaft; T: clearance; α: torsion angle; α1: upper torsion angle; α2: lower torsion angle.

Claims

1. A portal rudder having a pair of rudders consisting of a left rudder and a right rudder arranged on both sides of a propeller at the stern, characterized in that: The rudder is formed by a first rudder portion extending in the left-right direction and a second rudder portion extending in a straight line in the up-down direction when viewed from behind. The chord length of the second rudder portion in the front-rear direction is formed to be 40% to 100% of the diameter of the propeller. The propeller is arranged between 15% and 65% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side. The rudder shaft for driving the rudder is arranged at a position of 30% to 50% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side. forming a torsion angle at the second rudder portion, wherein an upper torsion angle formed at an upper portion of the second rudder portion is formed to be larger than a lower torsion angle formed at a lower portion of the second rudder portion, The front portion of the second rudder portion provided on the left side of the propeller is located on the left side of an imaginary line in the front-rear direction, and the rear portion of the second rudder portion provided on the left side of the propeller is located on the right side of the imaginary line. The front portion of the second rudder portion provided on the right side of the propeller is located on the right side of an imaginary line in the front-rear direction, and the rear portion of the second rudder portion provided on the right side of the propeller is located on the left side of the imaginary line.

2. The door rudder according to claim 1, wherein: A rudder shaft for driving the rudder is provided at a position of 35% to 45% of the rudder chord length from the leading edge of the second rudder portion when viewed from the side.

3. The door rudder according to claim 1 or 2, wherein: The gap between the propeller and the second rudder portion is formed to be 4% to 10% of the diameter of the propeller when viewed from behind.

4. The door rudder according to claim 1, wherein: The upper torsion angle is formed to be 3 degrees or more, and the lower torsion angle is formed to be 5 degrees or less.

5. The door rudder according to claim 1 or 2, wherein: When the ship is stopped, the second rudder is steered forward.

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