JPH01262289A - Water-jet propulsion machinery - Google Patents

Abstract

PURPOSE:To enable quick starting by spraying a partial water jet pressurized by a pump impeller to the inside of a water duct of a front flow part of the pump impeller at the time of low headway by a water nozzle, and avoiding any cavitation at the pump suction side. CONSTITUTION:A pump impeller 5 is set up in a water duct 4 interconnecting an intake 2 installed in a bottom part of a boat to a stern injection nozzle 9, and water taken in from the intake is pressurized by the pump impeller 5, spraying it out of the injection nozzle 9, and thus a thrust is secured. A partial water jet pressurized by the pump impeller 5 is put back by a water jet pipe 10, and when headway by a headway detector 11 is low, a valve 12 is opened, whereby it is sprayed to the inside of the water duct 4 of a front flow part of the pump impeller 5 from a water nozzle 13. With this constitution, occurrence of any cavitation at a time when the pump impeller 5 shifts from its low speed to the high-powered operation is avoided, thus quick starting can be made possible.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a water jet propulsion machine used as a propulsion machine for high-speed boats, which has excellent thrust characteristics particularly during low-speed navigation, and relates to a highly reliable water jet propulsion machine.

(Prior Art) As shown in FIG. 7, a water jet propulsion device generally includes a water guide duct 4 that guides water taken in from a water intake 2 provided at the bottom of a watercraft 1 into a pump casing 3, and the pump casing 3. It has a pump impeller 5 disposed inside and a differential user 6 connected to the secondary side of the pump casing 3. Also, a drive machine 7 that rotates the pump impeller 5 at high speed
will be equipped.

Water 8 introduced from the water intake 2 passes through the water guide duct 4 and is guided to the pump casing 3. The guided water 8 is pressurized by a pump impeller 5 rotated by a drive machine 7, and the pressurized water is injected at high speed from an injection nozzle 9 provided at the stern. The watercraft 1 gains thrust from the reaction of this water jet.

As the ship speed increases, the pressure of water introduced into the water intake 2 increases. In other words, a boat equipped with a water jet propulsion device uses a portion of the water pressure generated as the boat speed increases to the effective suction height (NPSH) of the suction part of the pump impeller 5.
Compared to ships equipped with general propeller propulsion equipment, the system has higher propulsion efficiency during high-speed navigation and excellent cavitation resistance.

Therefore, waterjet propulsion machines are especially suitable for propulsion of high-speed chartered vessels.

(Problems to be Solved by the Invention) However, when the above-mentioned propulsion device is installed in a floating high-speed boat, the right-handed suction height (NPSH) of the pump suction section may be insufficient.

In floating type high-speed boats, the hull is floated at high speed to reduce the resistance of the hull during high-speed cruising, so the height hS of the pump suction part from the suction water surface to the installation center of the water jet propulsion machine increases when floating. do. However, cavitation is less likely to occur because the pressure of intake water flowing in at high speed from the water intake is added as NPSH.

On the other hand, when the ship's speed is low or when attempting to shift from a stopped state to high-output operation all at once, cavitation is likely to occur because the static pressure of water acting on the pump suction part is low and the NPSH is small. In addition to not being able to obtain the desired thrust, the pump impeller may be damaged.

The characteristics of the pump impeller used in the water jet propulsion machine are generally as shown in FIG. In other words, the effective suction head (NPSH) of the pump is
When reaching H>, a cavity occurs, and the pump head H, which corresponds to the discharge pressure, decreases rapidly.At an even lower NPSH, the pump no longer functions as a pump, and the thrust of the propulsion machine decreases to near zero.

In order to avoid such a situation, when transitioning from low speed cruising to high output operation, the rotation speed n of the drive 17 is limited so as not to exceed the cavitation limit. FIG. 3 is a graph showing an example of a thrust performance curve of a water jet propulsion machine used for a small high-speed watercraft. As is clear from FIG. 3, when the watercraft is traveling at low speed or stopped, high-power operation is restricted by the cavitation limit.

That is, when the watercraft moves from a stop to a start, the pump impeller is operated at a rotation speed n2 or less corresponding to the cavitation limit at the beginning of startup. Since it is difficult to exceed the hump resistance value when the number of rotations is less than n2, next the ship speed v8
In response to the increase in , the pump impeller rotation speed is increased from n to n, taking care not to exceed the cavitation limit.
. is gradually increasing to. Therefore, there is a drawback that the acceleration performance of the boat until it overcomes the hump resistance is low.

On the other hand, it is also possible to design and manufacture a propulsion machine that can rotate the pump impeller at the maximum rotation speed from the time of takeoff and obtain a powerful thrust. For example, a water jet propulsion machine with a very high design speed uses a large, low-speed pump impeller, or an inducer is installed to add suction pressure, and the rotation speed of this inducer is set lower than the rotation speed of the main pump impeller. Measures have also been taken to improve cavitation characteristics, such as by using a pump impeller with a two-speed inducer, and to improve pump suction performance at low speeds.

However, low-speed large pump impellers are too heavy and are not suitable for small high-speed boats. On the other hand, the two-speed inducer-equipped pump impeller has a complicated mechanism and structure, and therefore has many drawbacks such as difficulty in maintenance management.

The present invention has been made to solve the above problems, and in a water jet propulsion machine that is required to be smaller and lighter, it is possible to improve the pump suction performance with a particularly simple configuration. The purpose of the present invention is to provide a water jet propulsion machine that has excellent thrust characteristics during low-speed navigation and is highly reliable.

(Means for Solving the Problems) In order to achieve the above object, the present invention arranges a pump impeller that rotates at high speed in a water guiding duct that communicates between a water intake provided at the bottom of a boat and an injection nozzle provided at the stern. A water nozzle that can control the amount of water jetted according to the cruising speed of a watercraft in a waterjet propulsion machine that generates thrust by pressurizing water introduced from a water intake using a pump impeller and spraying it from an injection nozzle. is provided in the water guide duct in the upstream part of the pump impeller. In addition, a water jet pipe is provided which connects the downstream part and the upstream part of the pump impeller, and returns the pressurized water discharged from the downstream part to the upstream part as return water, and the water I that communicates with the upstream part is provided.
It consists of a water nozzle connected to the tip of the II flow tube.

(Function) When a watercraft starts or sails at low speed, water introduced from the water intake is pressurized by the pump impeller, and the pressurized water is injected from the injection nozzle. A portion of this discharged pressurized water passes through the water jet pipe and is supplied from the downstream section of the pump impeller to the upstream section as return water.

The return water injected in the form of a high-speed jet into the water guide duct upstream of the pump impeller exchanges momentum with the water introduced into the water guide duct, increasing the static pressure inside the water guide duct. By increasing the NPSH on the pump suction side, the operating range in which cavitation of the water jet propulsion device can be avoided is expanded.

That is, the increase in NPSH caused by the returned water makes it possible to shift to high-output operation even during low-speed navigation, and the acceleration performance of the boat from the low-speed range to the medium-high speed range is greatly improved. Furthermore, the simple configuration of arranging a water jet pipe makes it possible to easily increase the NPSH on the pump suction side, and it is also possible to provide a highly reliable water jet propulsion method with fewer failures.

(Example) Next, an example of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing an embodiment of a water jet propulsion device according to the present invention.

Note that the same elements as those in the conventional example shown in FIG. 7 are given the same reference numerals, and detailed explanation thereof will be omitted.

The water jet propulsion device according to this embodiment includes a pump impeller 5 that rotates at high speed in a water guide duct 4 that communicates between a water intake 2 provided at the bottom 1a of a watercraft 1 and an injection nozzle 9 provided at the stern. In a water jet propulsion machine that obtains thrust by pressurizing water introduced from a water intake by a pump impeller 5 and injecting it from an injection nozzle 9, a water nozzle that can control the amount of water injection according to the cruising speed of a boat. 13 is provided in the water guide duct 4 at the upstream side of the pump impeller 5.

Furthermore, as equipment for supplying water to the water nozzle 13, the downstream part of the pump impeller 5 and the upstream part U are bypassed and connected, and the pressurized water discharged from the downstream part is returned to the upstream part U. A return water jet pipe 10 is provided.

This water jet pipe 10 is equipped with a water carrier adjustment valve 12 that operates according to the ship speed detected by a ship speed detector 11, and the water volume adjustment valve 12 opens the water jet pipe 10 when the ship speed is slow. The water jet pipe 10 is configured to be closed when the boat speed is high.

Further, the water jet pipe 10 is connected to a water nozzle 13 that is open downstream of the upstream portion U of the pump impeller 5.

This water nozzle 13 is connected to the water guide duct 4 by a support member 14.
Fixed inside.

Next, pump water M25ff at design sailing speed 45 knots
l/main, injection nozzle diameter d, = 100 m, water nozzle diameter d. The effects of the water jet propulsion device will be specifically explained with respect to a water jet propulsion machine in which the pump installation height hs from the axis of the pump impeller 5 to the suction liquid level is set to 2.5 m.

When a boat is sailing at its design speed, as shown in Figure 4, part of the water dynamic pressure generated by the boat speed is the suction pressure)
1s, the operating point of the pump impeller 5 of the waterjet propulsion machine is determined by the pump performance curve (Q-
H) and the hull resistance curve B. The pump water ffiQ at the operating point is 25TIl/1n.

On the other hand, the operating point of the pump impeller 5 when the water inserted in the water jet pipe 10 is in a state where the regulating valve 12 is fully closed and the boat is stopped is similar to the resistance curve A when stopped. The pump water mQ at this time is given by the intersection a of 24, 374/
It becomes i+in.

Next, when the water volume adjustment valve 12 is fully opened, the effective cross-sectional area of the injection nozzle 9 increases by the nozzle cross-sectional area of the water nozzle 13 provided in the water guide duct 4, and the pump operating point is determined by the resistance curve C and the pump The pump moves to the intersection C with the performance curve (Q-)-1 curve), and the pump water flow Q at this time is 26 ffl/
It will be a win.

At this time, the flow velocity Vj of high-speed diene [.
The flow velocity V of the high-speed jet at the exit of No. 3 is approximately equal and is calculated by the following equation (1).

-50.6m/sec -・-=・(
1) Water f injected from the injection nozzle 9 and the water nozzle 13
f1Q・andQ. are respectively Q from the nozzle cross-sectional area ratio.
・=23 , 9 Td/ ll1i n , Q n −
2-1 yd/min.

Here, the increase value of the hydrostatic pressure due to the return water flow from the water nozzle 13 provided in the water guide duct 4 is ΔH34, and the amount of water mixed with the water taken from the water intake RO2 and the return water from the water nozzle 13 is Q. (= 26 Td/ll1in), and when the flow rate is V, ΔHst is given by the following equation (2).

Q V Here, assuming that the maximum flow velocity V of water in the water guiding duct 4 is 8 m/sec, and substituting the numerical value into equation (2), equation (3) is obtained.

ΔH5t=2, 3 m ・---
--(3) That is, the NPSH of the pump suction part is 2.3 m
J! It turns out that J adds.

Here, the rotation speed n of the pump impeller is set to 200 Orpm, and the suction specific speed S・, So of each pump is calculated for the case where the return water is injected from the water nozzle 13 in the water guide duct 4 and the case where it is not injected. When calculated, the following (4) (5)
). Here, the pump N P S at the time of starting
H is 7.5m.

min Italy m.

11n-771 Further, the thrust force T is generally given by the following equation (6).

T=ρQ (V=-VS) -----...
(6) γ Here, ρ is the density of water, ρ = −= 102Q is the amount of water (Td/sec), Vj is the flow velocity of the high-speed jet at the outlet of injection nozzle 9 (m/sec), V3
is the speed of the boat (TrL/5eC).

Therefore, the thrust forces T and T at the time of starting the boat, respectively, when water is injected from the water nozzle 13 and when water is not injected. , the following equation (708) is obtained. When starting, VS = O, and Vj = 4X102X24.32 In order to set the limit value of the pump suction specific speed when the return water is not injected to the same value as the limit value of the pump suction specific speed when it is injected. is the rotation speed n of the pump impeller. needs to be reduced as given by equation (9) below.

・・・・・・(9) At this time, thrust force T. is given by the following equation (10).

Here, the thrust T is generally proportional to the square of the water IQ and the square of the rotation speed of the pump impeller, so = 1700 (/r
y) ......(10) That is,
In order to provide suction performance that prevents the occurrence of cavitation, it is possible to increase the NPSH at the pump suction port by adjusting the suction ratio of the pump impeller and spraying water from the water nozzle 13 disposed in the water guide duct 4. , the thrust at the time of starting a boat from 1000Kg (To) - in total 2
It can be increased to 060Kg (Tj). This greatly improves the acceleration performance of the boat when starting and when transitioning from low-speed cruising to high-output operation.

The above effects will be explained with reference to the thrust characteristic curve shown in FIG. According to this embodiment, a part of the pressurized water discharged from the downstream part of the pump impeller 5 is returned to the upstream part U through the water jet pipe 10, so that the NPSH in the upstream part U can be increased. I can do it.

Therefore, the region in which the pump impeller 5 can be operated without causing cavitation is expanded as shown by the hatched area. By selectively adjusting the rotational speed of the pump impeller 5 in this operating range, the maximum thrust when starting the watercraft can be increased from the conventional T to T8.

Therefore, it is possible to significantly improve the thrust characteristics when the boat starts and when cruising at low speed.

On the other hand, during high-speed sailing when cavitation is less likely to occur, injecting return water from the water nozzle 13 in the water guide duct 4 will actually reduce the thrust;
When the water flow rate exceeds a certain value, it is necessary to provide equipment to automatically adjust the amount of returned water, such as a mechanism for closing the flow path of the water jet pipe 10.

Specifically, as shown in FIG. 1, ON-OFF control is performed according to the ship speed V detected by the ship speed detector 11,
Or the sipping water amount adjustment valve 12 that proportionally controls the area of the flow path.
is arranged in the water jet pipe 10.

The water carrier regulating valve 12 opens the water jet pipe 10 when the ship speed 3 is slow, i.e. when starting or sailing at low speed, increasing the NPSH of the pump suction section, while when the ship speed is high, the water jet pipe 10 opens. to prevent thrust loss.

In addition, in this embodiment, the return water flow control mechanism is easily constructed with only a few parts such as the water jet pipe 10, and has no moving parts other than the water mother regulating valve 12, so maintenance management is easy. It also has the feature of extremely high operational reliability.

Next, another embodiment of the present invention will be described with reference to FIG. In the water jet propulsion basin according to this embodiment, the tip of the water nozzle 13a that injects water into the upstream portion U of the pump impeller 5 is provided so as to open on the inner wall surface of the back axial direction of the water guiding duct 4. There is.

Therefore, the flow velocity distribution of water in the water guide duct 4 is made uniform, the water flow path resistance is reduced, and the N
PSH can be obtained.

That is, when examining the flow velocity distribution of water in the water guide duct 4 connected to the water intake 2, it is generally found that the stroke length of the flow path along the pipe axis direction from the lowest end of the bent water intake 2 is longer than that on the opposite side. Since the flow length is longer than the stroke length of the flow path, the flow velocity of water flowing in from the lower end of the water intake port 2 is relatively reduced, forming an uneven flow velocity distribution.

Therefore, the flow velocity distribution of the high-speed jet stream ejected from the injection nozzle also becomes non-uniform, and there is a possibility that the propulsion efficiency will decrease.

However, as in this embodiment, the water nozzle 13a is disposed at the back surface of the water guiding duct 4 where the flow velocity decreases, and by jetting high-speed jet water in the axial direction, it is possible to accelerate the water flow. Therefore, it is possible to make the flow velocity distribution throughout the water guide duct 4 more uniform, and a higher thrust can be obtained by a more stable high-speed jet flow.

Furthermore, in the embodiment shown in FIG. 1, a support member 14 was provided for fixing the water nozzle 13 to the center of the water guiding duct 4, so there was a risk that flow path resistance would increase.
According to this embodiment shown in the figure, it is possible to omit the support member, and the pressure loss due to flow path resistance is reduced, making it possible to operate the propulsion device with higher efficiency.

In addition, in the embodiment described above, the pump blade! 11
A part of the pressurized water discharged from the downstream part of 5 is returned to the upstream part U to increase the suction pressure in the water guiding duct 4. A similar effect can be obtained even if it is supplied from a separate system.

〔Effect of the invention〕

As described above, according to the water jet propulsion device according to the present invention, jet water is supplied from the water nozzle to the upstream portion of the pump impeller when the watercraft starts or travels at low speed.

The water injected in the form of a high-speed jet into the water guide duct in the upstream portion exchanges momentum with the water introduced into the water guide duct, thereby increasing the static pressure within the water guide duct. Therefore, by increasing the NPSH on the pump suction side, the operating range in which it is possible to avoid xeviation of the water jet propulsion device is expanded.

In other words, by increasing NFSH through injection from the water nozzle, it is possible to immediately shift to high-output operation even when cruising at low speeds, and it is possible to significantly improve the acceleration performance of boats from low to medium-high speeds. can. In addition, the simple configuration of adding a water nozzle reduces the amount of N on the pump suction side.
It is possible to increase the PSH, and since there are few moving parts, maintenance management is easy, and a highly reliable water jet propulsion machine can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a water jet propulsion device according to the present invention, FIG. 2 is a sectional view showing another embodiment of the invention, and FIG. 3 is a thrust performance curve of a conventional propulsion device. FIG. 4 is a graph showing the pump performance curve and pump operating point. FIG. 5 is a graph showing the thrust performance curve of the propulsion device according to the present invention in comparison with a conventional example. FIG. 6 is a graph showing the NPSH of the pump.
FIG. 7 is a cross-sectional view showing an example of the structure of a conventional water jet propulsion machine. 1... Boat, 1a... Boat bottom, 2... Water intake,
3... Pump casing, 4... Water guide duct, 5...
...Pump impeller, 6...Diffusion user, 7...Driver, 8...Water, 9...Injection nozzle, 10...Water jet pipe, 11...Boat speed detector, 12 ...Water flow rate adjustment valve, 13.13a...Water nozzle, 14...Support member,
n, n, nl, n2...Pump impeller rotation speed, ■...Ship speed, R...Hull paper S resistance, T, T, T・, To...Thrust, H...Pump Lifting height, U...frontstream part, D...sequence part, a, b, c...
・Operating point. Applicant's agent Kuzen Hatano 6' Tsuru 2 Figure speed 73 □ Figure 3 Certain 4th ship ivs - 5th NF3Hre (, ypSH□ Graduation 6 Figure

Claims (1)

[Claims] 1. A pump impeller that rotates at high speed is disposed in a water guiding duct that communicates the water intake provided at the bottom of the boat with the injection nozzle provided at the stern, and the water introduced from the water intake is In a water jet propulsion machine that generates thrust by pressurizing the pump impeller and injecting it from the injection nozzle, a water nozzle that can control the amount of water jetted according to the cruising speed of the boat is installed in the front part of the pump impeller. A water jet propulsion device characterized by being installed inside a water guiding duct. 2. A water jet pipe is provided that connects the downstream part and the upstream part of the pump impeller, and returns the pressurized water discharged from the downstream part to the upstream part as return water. The water jet propulsion machine according to claim 1, further comprising a water nozzle connected to the tip. 3. The water jet pipe is equipped with a water volume adjustment valve that operates according to the ship speed detected by the ship speed detector, and the water volume adjustment valve opens the water jet pipe when the ship speed is slow, while The water jet propulsion device according to claim 2, wherein the water jet propulsion device is configured to close the water jet pipe when the speed is high.