JPS6116680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a propeller for propelling a ship.

Normally, it is effective to determine the maximum diameter of propellers for ship propulsion so that the highest propulsion efficiency can be obtained at the designed operating point, but generally speaking Due to these constraints, propellers are often forced to have smaller diameters than this optimum diameter, and as a result, propellers are currently used in conditions that are quite poor in terms of propulsion efficiency. On the other hand, under such current circumstances, as a propeller type that can more effectively improve propulsion efficiency, there is a so-called tandem type propeller in which two propellers are provided spaced apart at the front and rear on the same propeller shaft. Since this tandem propeller has two propellers on one shaft, the propeller shaft is long, and it is necessary to strengthen not only the shaft strength but also the bearing that supports this propeller shaft. Also, since the axial length is longer than a normal propeller, there was a disadvantage that it could not be replaced on current vessels using normal propellers due to the dimensions between the stern and the rudder plate.

In view of these conventional circumstances, this invention incorporates the advantages of tandem type propellers and eliminates their disadvantages, thereby achieving a propulsion efficiency that is almost the same as that of the optimum diameter even when the diameter is smaller than the designed maximum diameter. It provides the same propeller.

Embodiments of the propeller according to the present invention will be described in detail below with reference to the accompanying drawings.

1 to 3 are diagrams showing an embodiment of the present invention. In FIG. 1, reference numeral 1 indicates the stern portion of a ship, 2 indicates a rudder plate, and 3 indicates a portion located in front of the rudder plate 2 and located on the propeller axis. It is a propeller installed on the

As shown in FIGS. 2a, b and 3, this propeller 3 has at least four or more even number propeller blades 5, 6 each having a predetermined diameter provided on the outer peripheral surface of a boss 4. Among the adjacent propeller blades 5 and 6, one propeller blade 5
(hereinafter referred to as the front wing) has its reference line _G1 inclined forward by a rake angle θ _R1 and a pitch angle θ _P1 with respect to a plane orthogonal to the rotational axis CL. On the other hand, the other propeller blade 6 (hereinafter referred to as the rear blade) has its reference line G ₂ with respect to the plane perpendicular to the rotational axis CL.
is the same development plane as the reference line _G1 of the one wing 5, and the angle Δ is on the opposite side of the rotation axis CL.
In other words, each reference line G ₁ , G ₂
The boss 4 is inclined rearward by a rake angle θ _R2 so that a difference of the distance d occurs at the point where the boss 4 contacts the outer circumferential surface of the boss 4, and has a pitch angle θ _P2 larger than the pitch angle θ _P1 . Note that these front wings 5 and rear wings 6 are not formed in a tandem shape for reasons described later and to avoid interference with the stern and rudder plate, but are designed so that at least a portion 7 of the wings overlaps in the circumferential direction. will be placed.

Therefore, in the case of this embodiment, since the rake angles and pitch angles between the adjacent front wings 5 and rear wings 6 provided on the common shaft boss 4 are different, the front wings are tilted forward. In the flow accelerated by 5, there is a rear wing 6 tilted rearward. For this reason, even if the operating conditions (rotational speed, flow velocity) and diameter of the propeller change slightly, the characteristics of the front blade 5 will change in the same way as a conventional propeller, but the pitch angle of the rear blade 6 will be lower than that of the front blade 5. The change in characteristics is weakened in the accelerated flow, and after this the wing 6
Even under the above conditions, the reduction in propulsion efficiency is smaller than that of the conventional one. Incidentally, FIG. 4 shows the relationship between the diameter Dia and the propulsion efficiency ηo for the propeller a according to this embodiment and the conventional propeller b. In the figure, the symbol c indicates the optimum diameter.

According to the study results of the inventors, the sum of the rake angles of both propeller blades 5 and 6, that is, the angle Δθ in FIG. is 0.0 to 0.2Dp (Dp: propeller diameter), and the pitch ratio of both wings 5 and 6 (H/
It has become clear that propellers exhibit higher efficiency than normal propellers when the difference Δ(H/Dp) in Dp) is between 0.1 and 0.3. Figure 5 shows this state.
In the figure, a ₁ is Δθ = 0°, a ₂ is Δθ = 10°, a ₃ is Δθ
This is when θ = 15 to 20 degrees, and by appropriately selecting the relative positions of the front propeller blade 5 and the rear propeller blade 6, the wake of the propeller blade 5 can be prevented from interfering with the propeller blade 6. This shows that the effect of

In Figure 7, the horizontal axis is the sum of the rake angles of the front and rear blades Δθ, and the vertical axis is the independent efficiency η of the propeller of the present invention and the conventional type.
It shows the effect of the present invention when Δθ changes as a difference of ₀ . If the forward and aft wings have the same pitch ratio, it is ineffective and even harmful to tilt the wings relative to each other. If the pitch ratio of such rear blades is greater than the pitch ratio of the front blades, the independent efficiency of the propeller is increased and performance is improved by mutually tilting the blades. Also, Δθ is 20
The amount of performance improvement decreases when the angle exceeds Δθ, and 15° to 20° is the optimum range for Δθ.

In Figure 8, the horizontal axis is the pitch angle difference Δ(H/d) between the front and rear propeller blades, and the vertical axis is the difference in the independent efficiency η ₀ of the conventional propeller when Δ(H/d) is varied. This shows the effectiveness of the invention. If the forward inclination angle θ _R1 of the forward wing is −5° and the aft inclination angle θ _R2 of the aft wing is 15°, efficiency is improved by increasing the pitch angle of the aft wing than the forward wing. It is clear from this figure that mutually inclining when Δ(H/d) is 0 is harmful.

The forward inclination angle θ _R1 is 0° and the backward inclination angle θ _R2 is 15
In the case of ゜, a similar tendency of improvement is shown, but the amount is small.

In other words, the maximum effect can be obtained by tilting forward and backward and making the pitch angle of the rear wing larger than that of the front wing, and Δ(H/d) is 0.1 ~
0.3 is optimal.

In addition, in the present invention, the blade tip vortex (Tip Vortex), which is a factor that originally reduces propeller performance,
High propeller efficiency can be obtained by effectively utilizing the propeller for thrust. In other words, when a conventional propeller is tested in a cavitation water tank, TVC (Tip) spirals from the tip of the blade to the rear of the blade.
Vortex Cavitation) appears. A blade tip vortex is a vortex generated from the tip of a blade, and appears as a vortex system that continues far behind the blade, and is an element that causes energy to flow out and degrades propeller performance. However, according to the present invention, the blade tip vortex generated from the front blade 5 passes over the back surface of the rear blade 6, so that thrust can be generated in the rear blade and the propeller performance can be improved.

Figure 9a shows an example of TVC observed in a conventional propeller in a cavitation water tank, and shows a situation where TVC appears in a spiral shape from the tip of the blade to the rear of the blade. On the other hand, in Figure b, the forward inclination angle θ _R1 is −5° and the backward inclination angle θ _R2 is −5° in the propeller according to the present invention.
The observation result of the occurrence of TVC in an example cavitation water tank where the pitch angle difference Δ(H/d) is 0.2 at 15 degrees shows that the TVC of the front wing 5 passes near the tip of the rear wing 6, near the back surface, and the performance Indicates a state that contributes to improvement.

However, since the flow of the propeller is spiral-shaped and difficult to understand, the state of interference between the flow of the front blade and the rear blade along the spiral plane of the flow can be diagrammed as shown in FIG. 10. When trying to improve efficiency with a composite wing, one is the TV interference mentioned above, and the other is to make the wake of the front wing interfere with the rear wing to improve the lift-drag ratio. FIG. 11 shows the flow conditions of the front and rear wings along the cylindrical plane of flow. In order to improve the lift-drag ratio by utilizing the interference of the wake of the front wing with the rear wing, as shown in the figure, pass the wake of the front wing through the face side (pressure side) of the rear wing, and also Angle of attack α
It is effective to make the angle of attack α ₂ (pitch angle) of the rear wing larger than ₁ (pitch angle).

FIG. 10 shows the relationship between the rear wing and the front wing along the spiral plane of the flow from the rear of the flow. (a) is the case where the forward inclination angle θ _R1 of the front wing is -5°, and (b) is the case when θ _R1 is 0.

As the trailing edge of the forewing contracts, the forewing's TV becomes smaller than the trailing wing's.
Passes through 0.90~0.95R position. In the range of a normal propeller, the TV and the wake of the front wing cannot be used effectively, as shown in Figure b. That is,
The TV on the front wing hits the rear wing or passes through the face side (pressure side), and not only does the TV not improve the force, but the propeller operates hydraulically and is heavy (0.5R to 0.8 The wake of the front wing is too far away from the rear wing in the R section, making it impossible to improve the lift-drag ratio in this area as well. On the other hand, as shown in Figure 10a, by tilting the front wing forward, the TV of the front wing can pass through an appropriate position on the back side (suction side) of the rear wing, and at the same time, the wake The propeller is now in a state where it properly interferes with the rear wing, improving propeller performance as a whole.

However, due to the characteristics of the flow, it is not desirable to create a flow with too much distortion. If the front wing is tilted forward significantly, the spiral flow created by the front wing will also be tilted relatively forward, causing distortion in the flow.
Therefore, it is better to reduce the slope of the front wing.

In addition, in order to effectively utilize the interference of the wake of the front wing on the rear wing, it is necessary to make the angle of attack of the rear wing larger than that of the front wing. Therefore, the pitch angle of the rear wing is equal to the pitch angle of the front wing. Making it larger is effective for improving efficiency.

As is clear from the above explanation, in order to enjoy the above advantages, the propeller blades 5 and 6 must be
Of these, it is not effective to simply tilt only one of the wings; instead, one wing 5 is tilted forward and the other wing 6 is tilted in the opposite direction within the range of the angle Δθ. This can be achieved by providing a difference in pitch ratio between the wings 5 and 6 as shown in FIG.

FIG. 6 shows this state based on theoretical calculations. In the same figure, in a ₃ , the rake angle θ _R1 of the front wing 5 is 5°, the rake angle θ _R2 of the rear wing 6 is 15°, and the pitch ratio difference is 0.2, and in a ₄ , the rake angle θ _R1 of the front wing 5 is 15°. 0°, the rake angle θ _R2 of the rear wing 6 is 15°, and the difference in pitch ratio is 0.2, and for a ₅ , the rake angle θ _R1 of the front wing 5 is 0.
This is when the rake angle θ _R2 of the rear wing 6 is 15° and the pitch ratio difference is 0. As is clear from this figure, the structure in which the front blades 5 are tilted forward and the front blades 5 and the rear blades 6 have a difference in pitch ratio has higher propeller efficiency than other structures. Furthermore, in order to facilitate the manufacture of the propeller blades in the above embodiments,
As shown by the dashed line S in Fig. 1, each wing 5, 6
It is convenient to separately manufacture and assemble each of the parts together with the corresponding parts of the shaft boss 4.

As detailed above, according to the propeller of the present invention, one of the adjacent propeller blades provided on the shaft boss is tilted forward and the other backward, and the propeller blade is tilted backward relative to the pitch angle of the front propeller blade. By increasing the pitch angle of the propeller blades, the wake and tip vortices of the front propeller blades are actively used by the rear propeller blades, so even if the operating conditions and diameter of the propeller change, Propulsion efficiency is improved compared to conventional propellers. In addition, in order to obtain this effect, the front blade and the rear blade are arranged so as to overlap in the circumferential direction, so if the axial length of the propeller is long as in a conventional tandem propeller, First, there is the advantage that there is no need to reinforce the propeller shaft and its bearings, and that it can be replaced as is even on ships currently in use that use normal propellers.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the propeller according to the present invention in use, FIG. The figure shows how the pitch angle is applied to each of the blades, and the figures 4, 5, 6, 7 and 8 schematically show the operation and propulsion efficiency of this invention. Figure 9 is an observation diagram of a conventional propeller and the propeller of the present invention in a water tank. Figure 10 is a diagram showing the interference between the front and rear wings. Figure 11 is the interference of the wake of the front wing with the rear wing. FIG. 3 ...Propeller, 4...Shaft boss, 5, 6...Propeller blade, CL...Rotation axis, _G1 , _G2 ...Reference line of each blade 5, 6, θ _R1 , θ _R2 ...Each blade Rake angles of 5 and 6, Δθ...sum of rake angles, θ _P1 , θ _P2 ...
Pitch angle of each wing 5 and 6.

Claims (1)

[Claims] 1 It has an even number of propeller blades, one of the adjacent propeller blades is tilted forward and the other backward, and the pitch angle of the rear propeller blade is larger than the pitch angle of the front propeller blade, and The blades are arranged such that at least a portion thereof overlaps in the circumferential direction, and the sum of the rake angles between the blades is set in the range of 10 to 20 degrees, and the difference in pitch ratio is set in the range of 0.1 to 0.3. Propeller for ship propulsion.