JP2595478Y2 - Side fence device for water jet propulsion - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a side fence device used to reduce a pressure loss due to a secondary flow accompanied by a vortex pair generated in a flash type intake (inlet / outlet) of a water jet propulsion device.

[0002]

2. Description of the Related Art As shown schematically in FIG. 5, an example of a water jet propulsion device is a connection between an intake 2 opened at the bottom of the stern side of a water jet propulsion boat and a discharge nozzle 3 opened at the stern end. A main shaft 5 rotatably supported on the hull side via a bearing 4 is extended in the flush type intake duct 1 to be horizontal, and a blade of the main shaft 5 is provided at an end of the main shaft 5 so as to constitute an axial flow pump. At the same time as attaching the vehicle 7, the guide blades 6 are fixed to the inner wall of the intake duct at a position downstream of the impeller 7, and the main shaft 5 is rotated when the water jet propulsion boat is navigating to rotate the impeller 7, whereby the intake 2 The water taken into the intake duct 1 from above is jetted rearward from the nozzle 3 as jet water to obtain a propulsive force.

The propulsion efficiency of the water jet propulsion boat is determined by the total pressure loss coefficient (ζ = (Pt∞−Ptd) / 1 /) when the fluid taken in from the intake 2 is ejected through the pump in the intake duct 1. 2ρVs ² ) is greatly affected, and reducing the total pressure loss coefficient can improve the propulsion efficiency of the water jet propulsion boat. Here, Pt∞ is the total pressure in the intake 2 portion, Ptd is the total pressure in the intake duct, and ∞ is a uniform flow (ship speed).

[0004] The total pressure loss coefficient in the intake duct 1 is determined by the ratio of intake speed (IVR) when the flow velocity in the intake 2 is Vs, and the flow velocity in the intake duct 1 is Vd. .) = Vd / Vs, it has been found from the experimental results of the present inventors that the flow velocity distribution in the intake duct 1 changes due to the occurrence of cavitation in the pump section and the like.

FIGS. 6 to 9 show the results of the above experiments. FIG. 6 shows a vertical direction in the intake duct 1 which changes depending on the suction speed ratio (IVR) when the bottom of the ship is flat. It shows the flow velocity distribution, and in the intake duct 1 as shown in (a), the flow velocity in the vertical direction at the position (XX) of the pump inlet of the intake duct 1 when the flow velocity Vs of the intake 2 is 35 m / s. The distribution is shown in (b).

In FIG. 6 (b), a curve I represents a case where the suction speed ratio (IVR = Vd / Vs) is 0.25.
The flow velocity is high on the ship bottom side, which is on the lip 8 side, and small on the upper side, which is on the ramp 9 side, and the flakes are coming off. Curve II shows the I.V. V. R. = 0.5, the flow velocity distribution is such that the flow velocity on the lip 8 side is large and the flow velocity on the ramp 9 side is small. Curve III shows I.V. V. R. When 0.75, the difference in the flow velocity distribution between the lip 8 side and the lamp 9 side is small. Curve IV shows the I.V. V. R. = 1.0, the curve V V. R. = 1.25, the flow velocity distribution is such that the flow velocity on the ramp 9 side increases as Vs decreases as the flow in the intake 2 is disturbed.

FIG. 7 shows a state in which the flow velocity distribution changes according to the suction speed ratio (IVR) when the ship bottom shape is a round bottom, and the curves I, II, III, and V show the curves. The curves are the same as curves I, II, III and V in FIG. V. R. =
0.25, 0.5, 0.75, and 1.25.

In the case where the bottom of the ship is a flat bottom, FIG.
(B) A suction speed ratio showing a flow velocity distribution as shown in (b).
V. R. 8) and the total pressure loss coefficient are as shown in FIG. 8, and when the ship bottom shape is a round bottom, the suction speed ratio (I.I.) showing the flow velocity distribution as shown in FIG.
V. R. ) And the total pressure loss coefficient are as shown in FIG.

As is apparent from FIGS. 8 and 9, the difference in the flow velocity distribution is small, and the flow is stable. V. R. It can be seen that the total pressure loss coefficient is low near = 0.9, and the total pressure loss coefficient is small when the difference in the flow velocity distribution in the intake duct 1 is small.

However, if the suction speed ratio (IVR) where the difference in the flow velocity distribution in the intake duct is small as described above, the total pressure loss coefficient can be reduced, and the propulsion of the water jet propulsion boat can be achieved. Although the efficiency can be improved, a vortex 10 is generated symmetrically at the opening edge of the intake 2 as shown in FIG. 10. A pressure loss due to the flow occurs in the intake 2 portion, and as a result, the smooth flow into the intake 2 is not performed, the flow velocity Vd in the intake duct 1 is reduced, and the suction velocity ratio in which the difference in the vertical flow velocity distribution is small is reduced. Therefore, the total pressure loss coefficient cannot be reduced, and the propulsion efficiency of the water jet propulsion boat cannot be improved.

Therefore, in order to weaken the generation of the secondary flow accompanied by the vortex of the intake which affects the propulsion efficiency of the water jet propulsion boat, the flow from the intake to the intake duct can be smoothly performed. FIG.
(B) As shown in (b) and (c), two side fences 11 having a length equal to or shorter than the opening length in the front-rear direction of the intake 2 are provided at positions near both side edges of the opening of the intake 2. It is conceivable that the height H is configured to be installed in parallel in the front-rear direction.

When the side fences 11 are arranged on the left and right sides of the opening of the intake 2 as described above, the flow of the intake 2 is regulated and a smooth flow is achieved. As shown in FIG. 11 (b), the strongly viscous flow accompanied by the vortex pair generated by the vibration is weakened, and as shown in FIG. 11 (b), a smooth flow like the flow 12 flows smoothly to the intake 2 at the opening edge of the intake 2. It has been confirmed by experiments that the pressure loss in the intake 2 portion is reduced, the flow velocity distribution in the intake duct 1 is improved, the total pressure loss coefficient can be further reduced, and the propulsion efficiency can be improved. I have.

That is, the length L ₁ of the side fence 11 attached to the intake 2 in parallel in the front-rear direction is
When the opening length L of the intake 2 is 430 mm, 27
If the height is set in the range of 0 mm to 430 mm and the mounting height H of the side fence 11 (the width of the side fence 11) is set to 1/5 to 1/6 of the opening width W of the intake 2, it occurs in the second portion of the intake. As a result of reducing the pressure loss by weakening the secondary flow accompanied by the swirling vortex, it has been confirmed by experiments that the total pressure loss coefficient can be reduced where the flow is stabilized in the intake duct 1, and a patent application has already been filed by the present applicant. I have.

[0014]

However, the side fence 11 is provided in the front-rear direction along the opening edge of the intake 2 as shown in FIGS. Then, as shown in FIG. 12, when the water jet propulsion watercraft S obliquely travels at an angle of θ with respect to the traveling direction Y, the side fence 11 also inclines at an angle of θ with respect to the traveling direction Y, and the angle of arrival becomes θ degrees. The water flow hits at the corners, and an eccentric flow occurs around the side fence 11 to generate a negative pressure on the back surface of the side fence 11 and a positive pressure on the surface. As a result, lift FL and drag FD as shown in FIG. Is generated as shown by the broken line, and it is conceivable that the generation of negative thrust and the alienation of stability such as the stern side swinging adversely affect the propulsion of the ship.

In view of the above, the present invention weakens the secondary flow accompanying the vortex pair generated in the intake portion to reduce the pressure loss, and also suppresses the lift and drag generated during oblique navigation when the side fence is provided. Is what you try to do.

[0016]

According to the present invention, in order to solve the above-mentioned problems, the length of the opening of the intake is set to be equal to or shorter than the front-rear length of the opening at the position near both side edges of the opening. In addition, two side fences provided with a large number of small-diameter holes so that water can pass in the front and back directions are arranged in parallel in the front-rear direction, and the heights of the two side fences are adjusted to the opening of the intake. One fifth of width
In other words, the diameter of the hole provided in each side fence is set to 1/10 or less of the height of the side fence, and the hole brightness is set to about 1/6 or less.

[0017]

Since the flow of the fluid in the intake portion is regulated by the left and right side fences having a height of one fifth to one sixth of the width of the opening width of the intake, the fluid flows along the opening edge of the intake. Secondary flow with vortex pairs is weakened, smooth flow into the intake is performed, pressure loss at the intake part can be reduced, flow velocity distribution in the intake duct is improved, and the total pressure loss coefficient is reduced Let me do.

Each of the side fences has a hole having a diameter of 1/10 or less of the height of the side fence, and furthermore, the drilling rate is set to 1/6 or less. Water flow hitting the surface of the fence will pass through the small holes in the side fence and flow to the back, reducing the pressure difference between the surface and the back of the side fence, thus reducing the lift and drag due to the side fence. be able to.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 (a), (b) and (c) show an embodiment of the present invention. As shown in FIGS. 11 (a), (b) and (c), a water bottom having a round bottom is shown in FIG. The side fence 11 having a length equal to or shorter than the length in the front-rear direction of the opening of the intake 2 is provided close to both side edges of the intake 2 elongated in the front-rear direction at the bottom of the jet propulsion boat. The height is arranged in parallel in the front-rear direction to reduce the pressure loss at the intake 2 part.
In the same configuration as the case where the total pressure loss coefficient in the intake duct is reduced by smoothly flowing into the intake duct, a side fence 13 having a large number of small-diameter holes 14 such as a perforated plate is used. The perforated side fence 13 is arranged close to both side edges of the opening of the intake 2 and arranged in parallel in the front-rear direction.

The diameter of the holes 14 of the side fence 13 and the number of the holes 14 are such that water can pass through the holes 14 of the side fence 13 so that the pressure difference between the front side and the back side of the side fence 13 can be suppressed. And intake 2 as shown in FIG.
The secondary flow accompanying the vortex 10 generated at the opening edge of the opening is made appropriate from the viewpoint that it can be weakened.

The present invention have found, for the case the ship bottom shape of a round bottom, and if not replacing the side fences to the intake 2 parts, 270 mm length L ₁ as a side fence, and the mounting height (width) H 25 mm 11 (a), (b) and (c) without holes, and the side fence 13 with holes 14 with hole diameters of 2mm, 3mm and 5mm. An experiment was conducted on how the total pressure loss coefficient changes with respect to the case where
The result as shown in FIG. 2 was obtained. In FIG. 2, the crosses indicate the suction speed ratio (I.
V. R. ) Shows the change in the total pressure loss coefficient in the range of 0.25 to 1.25. On the other hand, in the case of the side fence without holes when the side fence is attached, the total pressure loss coefficient changes as
In the case of a side fence 13 with a hole, a hole with a hole diameter of 2 mm is shown as a triangle, a hole with a hole diameter of 3 mm is shown as a square, and a hole with a hole diameter of 5 mm is shown as a triangle. Was done.

As is clear from the experimental results shown in FIG.
When the side fence is attached, as compared with the case where the side fence is not attached, the suction speed ratio (IVR) at which the problem of cavitation of the pump portion in the intake duct 1 is small is 0.75 to 1. It can be seen that the total pressure loss coefficient can be reduced at 0, but in the case of the perforated side fence 13, the total pressure loss coefficient cannot be reduced so much if the diameter of the hole 14 is 5 mm, so it is better to reduce the hole diameter to 3 mm or less as much as possible. You can see that.

Next, the side fence 13 provided with the hole 14
When the diameter L of the hole 14 was 3 mm or less when the length L ₁ of the side fence 13 was 270 mm and the mounting height H was 25 mm, FIG. Mounting height H, as shown partially enlarged
When the diameter of the hole 14 provided in the side fence 13 is d, the pitch of the holes 14 in the width direction of the side fence 13 is P ₁ , and the pitch of the holes 14 in the longitudinal direction of the side fence 13 is P ₂ , the diameter of the hole 14 Is preferably 3 mm or less, so that if the hole diameter is d = 3, d / H = 3/25 = 1 / 8.3 about 1 /
The hole diameter is about 10H, P ₁ = about 3 × d, P ₂ = 3
When the hole porosity is obtained with about × d, the hole porosity = (1 / 2πd
² ) / (3d × 3d) = π / 18 = approximately 1/6, and therefore, the porosity ≦ １ ／ and the pore diameter d / H ≦ 1/10
The following are the critical hole porosity and the hole diameter.

In the configuration in which the side fence 13 having the hole opening ratio and the hole diameter determined as described above is attached, when the water jet propulsion boat makes a diagonal trip, as shown in FIG. Side fence 1 at the appropriate angle θ
3 is inclined with respect to the traveling direction Y of the ship, so that the water flow hits the side fence 13 at an angle of attack of θ degrees, the lift FL and the drag F
D occurs, but the side fence 13 has a hole 14
Since the water flow passes through the hole 14 and the pressure difference between the front side and the back side of the side fence 13 can be suppressed low, the lift FL and the drag FD are reduced as shown by the solid lines in FIG. You can do it.

[0026] Note that in the figure is shown the case where the same and the length L ₁ of the front and rear openings of the intake 2 direction length L and side fences 13, when the 430mm of L, L ₁
Has been confirmed to be effective even if L is reduced to 270 mm, L ₁ may be shorter than the length shown in the figure.

[0027]

As described above, according to the side fence device for a water jet propulsion device of the present invention, at the position near the both side edges of the opening of the intake, the length of the intake opening in the front-rear direction is equal to or less than the length of the intake opening. Two side fences having a short length and having a large number of small diameter holes so that water can pass in the front and back directions are arranged in parallel in the front-rear direction, and the heights of the two side fences are set as described above. The diameter of the hole provided in each of the side fences is set to 1/10 or less of the height of each side fence, and the hole opening rate is set to about 6 minutes, as one fifth to one sixth of the opening width dimension of the intake. Of 1
Since it is configured as follows, the flow of the intake portion is regulated by left and right side fences having a height of 1/5 to 1/6 of the opening width dimension of the intake so as to smoothly flow into the intake. As a result, the pressure loss at the intake section can be reduced, and the total pressure loss coefficient at the pump section in the intake duct can be reduced. The large lift and drag generated by hitting the water flow in the above-mentioned hole diameter, the hole flow rate can be reduced because the water flow can pass through the hole of the side fence and the pressure difference between the surface and the back surface of the side fence can be reduced. Can,
It is possible to obtain an excellent effect that the propulsion at the time of oblique navigation of the ship can be performed stably.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a cut-away side view showing a state where a side fence is attached to an intake portion, (b) is a view taken along the line AA of (a), (C) is a view on arrow B of (a).

FIG. 2 shows the relationship between the total pressure loss coefficient and the suction speed ratio when there is no hole, when there is no side fence, when there is a side fence, and when there is a hole and the hole diameter is different when the ship has a round bottom. FIG.

FIG. 3 is an enlarged view of a part of the side fence in the present invention.

FIG. 4 is a diagram showing the lift and drag when the ship goes obliquely when the side fence device of the present invention is used.

FIG. 5 is a cut-away side view showing an example of a water jet propulsion device of the water jet propulsion boat.

FIG. 6 shows the intake duct and the flow velocity distribution in the intake duct when the ship bottom shape is a flat bottom.
FIG. 4 is a view of an intake duct, and FIG. 4B is a view showing a vertical flow velocity distribution at a pump inlet position in the intake duct.

FIG. 7 is a view showing a vertical flow velocity distribution at a pump inlet position in an intake duct when a ship bottom shape is a round bottom.

FIG. 8 is a diagram showing a relationship between a total pressure loss coefficient and a suction speed ratio when a ship bottom shape is a flat bottom.

FIG. 9 is a diagram showing a relationship between a total pressure loss coefficient and a suction speed ratio when a ship bottom shape is a round bottom.

FIG. 10 is a bottom view showing a secondary flow with a vortex pair generated in a conventional intake.

FIG. 11 shows an example in which a side fence is attached to an intake portion, in which (a) is a cut side view showing a state in which the side fence is attached to the intake portion, and (b) is a C- line in (a).
(C) is a view taken in the direction of the arrow D in (A).

FIG. 12 is a schematic diagram showing a state when the ship is obliquely sailing.

FIG. 13 is a diagram showing a lift and a drag generated around a side fence when the ship goes obliquely.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Intake duct 2 Intake 13 Side fence 14 hole L Length of intake opening front-back direction L ₁ Side fence length H Mounting height

Continuation of the front page (56) References JP-A-4-243687 (JP, A) JP-A-61-218496 (JP, A) JP-A-6-329085 (JP, A) JP-A-7-112698 (JP) , A) JP-A-2-54698 (JP, U) JP-A-7-6099 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B63H 11/103 B63H 11/10 B63H 11/01 B63H 11/107

Claims (1)

(57) [Scope of request for utility model registration] 1. A plurality of small-diameter holes having a length equal to or shorter than the length of the opening of the intake in the front-rear direction and near the side edges of the opening of the intake are provided so that water can pass in the front and back directions. The two side fences are arranged in parallel in the front-rear direction, and the height of each of the two side fences is set to 1/5 of the opening width of the intake.
In another aspect, the diameter of the hole provided in each side fence is set to 1/10 or less of the height of the side fence, and the hole brightness is set to about 1/6 or less. Side fence device for water jet propulsion.