JPH08104293A - Water jet propulsion unit - Google Patents

Abstract

PURPOSE: To improve high speed performance by providing an air introduction port ahead of an impeller and communicating the air introduction port with an air supply control means for controlling the air supply amount in accordance with rotary speed of the impeller and ship speed. CONSTITUTION: An air introduction port 13 is provided ahead of an impeller 9 and on an inner peripheral face of a duct 4 in the vicinity of a wing end where speed of the impeller 9 is the highest. An air supply valve 15 is opened and closed in accordance with rotary speed of the impeller 9 by an air supply control means 17 to supply air. In a water jet propulsion unit, since water flowing into the duct 4 can utilize dynamic pressure equivalent to ship speed as effective suction pressure of the impeller 9 depending on the shape of a suction port 6, the generation of cavitation can be suppressed. Consequently, the optimum air introduction amount which corresponds to rotary speed of the impeller 9 and ship speed is set by program in an air introduction amount arithmetic unit 18, and the opening and closing of the air supply valve 15 are controlled by the air introduction amount arithmetic unit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propulsion device for a ship that obtains thrust by water jet injection, and more particularly to a water jet propulsion device with improved high speed performance.

[0002]

2. Description of the Related Art Conventionally, a water jet propulsion device is shown in FIG.
10 is known, and in the example of FIG. 9, a pump impeller 9 driven by a rotary drive shaft 12 connected to a prime mover 2 for propelling water sucked from a suction port 6 provided in a ship bottom 5 is known. After being pressurized by and rectified by the guide vane 11, it is jetted from the jet nozzle 8 at a high speed, and thrust is obtained by its reaction.

Further, in the example of the hydrofoil shown in FIG. 10, the duct 4 hangs from the bottom 5 to the vicinity of the hydrofoil 52 below the surface of the water because the hull 1 floats above the surface of the water when the wing is traveling (during high-speed cruising). The suction port 6 is opened forward, and the rotary drive shaft 12 of the impeller 9 and the output shaft of the prime mover 2 are connected via a speed reducer 53 for driving the pump by the high-speed prime mover 2. .

Generally, a screw propeller has a higher propelling efficiency as it has a large diameter, low speed and operates at a low speed, and usually has a high speed impeller and a duct with friction and eddy resistance in a speed range of a ship. Is disadvantageous in efficiency, but the propeller speed increases in proportion to the speed of the surrounding water flow as the boat speed increases, while the peripheral speed of the propeller blade tip decreases performance due to cavitation, noise・ Velocity is limited due to vibrations and erosion of the propeller surface, which limits the speed of the propeller or the diameter of the propeller, thus limiting the speedup.On the other hand, the duct produces dynamic pressure equivalent to the boat speed. Since it can be used as the effective suction pressure of the impeller, it is effective in suppressing the cavitation of the impeller. It can be made faster than Yupuropera, recently, an example of using water jet propulsion apparatus in a high speed range than conventional screw propellers from speed requirements of the ship is increased.

[0005]

However, even in the above-mentioned water jet propulsion device, there is a limit to the rotational speed of the impeller that does not cause cavitation, and the pump cannot be operated at a higher speed than this limit. From the stage, the improvement of high-speed performance is hampered.In order to further speed up the ship, the shape of the pump has a small specific speed, the pressure is increased, and the water flow is accelerated by the injection nozzle to increase the speed of jet injection. As a result, the pump will become larger and heavier, so a light-weight, high-output high-speed prime mover such as a gas turbine engine will be used to increase the speed and size of a ship while the pump part will be used. Is slower and heavier and requires a speed reducer with a large reduction ratio to connect the two, making the power transmission system large and compatible with high-speed prime movers. Poor, can not be compact, lightweight, high-output of the entire propulsion system, improvement of the high-speed performance of the ship is discouraged.

In addition, the fact that the speed of a ship is increased means that the speed of the ship changes continuously from the stopped state to the high-speed cruising speed, and the propulsion device can cope with a wide range of speed changes for each running state. The conventional water jet propulsion system is designed to have the highest propulsion efficiency at high cruising speeds, and it is said that propulsion efficiency decreases when accelerating in the medium / low speed range and especially from low speed to high speed range. There is a problem,
Particularly, in the example of the hydrofoil of FIG. 10, when the hull is levitated from the surface of the water, the water resistance to the hull is large until the hull floats, and the maximum thrust is required to accelerate from the low speed range to the wing speed. It will be a great disadvantage.

An object of the present invention is to enable high speed operation of the pump by exceeding the speed limit due to cavitation caused by high rotation of the impeller, thereby making the pump smaller, lighter and faster, thereby improving the high speed performance of the water jet propulsion device. In addition, it is to improve compatibility with a high-speed prime mover and to reduce the size, weight, and output of a water jet propulsion device to improve high-speed performance of a ship.

Another object of the present invention is to provide a water jet propulsion device capable of preventing a decrease in propulsion efficiency in a wide speed range corresponding to the traveling state of a ship.

[0009]

According to the present invention, there is provided a water jet propulsion device in which an impeller driven to rotate is arranged in a duct having a suction port, and an injection nozzle is arranged behind the impeller, in front of the impeller. A water jet propulsion device, characterized in that an air inlet is provided in the air inlet, and the air inlet is communicated with an air supply control means for controlling an air supply amount according to the rotation speed of the impeller and the boat speed. Is.

Further, the present invention is characterized in that an inlet guide vane provided with an air inlet is provided on the front surface of the impeller, and the inlet guide vane is fixed to the duct or is supported at a variable pitch.

Further, the present invention is characterized in that the impeller is formed in a super cavitating blade shape.

Further, according to the present invention, the rotary drive shaft of the impeller is directly connected to the output shaft of the high-speed prime mover, the suction port is provided with a pressure detecting device, and the output signal of the pressure detecting device causes
It is characterized in that a prime mover protection control device for preventing excessive rotation of the prime mover is provided.

The present invention is also characterized in that the jet nozzle is provided with nozzle area varying means for changing the cross-sectional area of the jet nozzle.

The present invention is also characterized in that the suction port is provided with a suction port shape changing means for changing the shape of the suction port.

[0015]

According to the present invention, the air supply control means introduces an appropriate amount of air into the impeller section according to the rotational speed of the impeller and the speed of the boat, thereby lowering pump performance and noise due to cavitation caused by high rotation of the impeller. -The high-speed performance of the water jet propulsion device can be improved by preventing vibration and erosion of the machine surface, enabling high-speed operation of the pump, and reducing the size, weight and speed of the pump.

An inlet guide vane having an air inlet is provided on the front surface of the impeller, so that air can be smoothly introduced into each part of the impeller when the impeller blade width is large, and the pitch of the inlet guide vane is variable. By so doing, it is possible to control the angle of attack of the water flow to the impeller and prevent a decrease in pump efficiency due to a change in the flow rate.

Since the impeller is formed in the shape of a super cavitating blade, the impeller can be operated at a very high speed, and the water jet propulsion device can be operated at a very high speed.

According to the present invention, the high-speed prime mover can be directly connected by increasing the speed of the pump, the water jet propulsion device can be made small, lightweight, and large in output to improve the high-speed performance of the ship. A pressure detecting device is provided at the mouth, and the output signal of the pressure detecting device controls the rotation of the prime mover when the inflow water to the suction port is interrupted by the prime mover protection control device for preventing the excessive rotation of the prime mover. Therefore, damage to the prime mover can be prevented.

According to the present invention, the nozzle area varying means changes the cross-sectional area of the injection nozzle in accordance with the boat speed and the running state, and the jet injection speed is optimized, thereby propulsion efficiency due to the change in the boat speed. Can be prevented.

Further, according to the present invention, the shape of the suction port is changed by the suction port shape changing means in accordance with the boat speed and the running state, and the effective suction pressure of the impeller is optimized to change the boat speed. It is possible to prevent a decrease in propulsion efficiency due to.

[0021]

【Example】

(First Embodiment) FIG. 1 shows a first embodiment of a water jet propulsion apparatus according to the present invention, in which a water jet propulsion apparatus forms a prime mover 2 and a duct 4 for forming propulsion water inside a hull 1. Is installed, and the inlet of the flow path 3 is the bottom 5 of the ship.
Has a suction port 6 formed in the duct 4 and an outlet formed with an injection nozzle 8 in the stern portion 7. The impeller 9 is provided between the suction port 6 and the injection nozzle 8 and the impeller bearing 1 is provided behind the impeller 9.
0 and guide vanes 11 are provided, and the impeller 9
The rotary drive shaft 12 coupled to is connected to the prime mover 2, the impeller 9 is rotationally driven by the prime mover 2 to pressurize the water sucked from the suction port 6, and the water is further rectified by the guide vanes 11, It is jetted from the jet nozzle 8 to generate thrust.

An air introduction port 13 is provided on the inner peripheral surface of the duct 4 in front of the impeller 9, and the air introduction port 13 communicates with an air passage 14 formed on the outer periphery of the duct 4, and this air passage 14 is provided with this air passage 14. An air supply valve 15 is provided, and an air introduction amount calculation device 18 in which an optimum air introduction amount is programmed by an output signal of the rotation speed detection device 16 of the impeller 9 (or the prime mover 2) and the boat speed detection device 17 is provided. The air supply control means 19 is configured by controlling the opening and closing of the air supply valve 15 by the output signal of the air introduction amount calculation device 18 using.

When the relative speed between the flow velocity of the water sucked from the suction port 6 and the rotation speed of the impeller 9 becomes high due to the rotational driving of the impeller 9, the pressure on the back surface of the impeller 9 becomes lower than the vapor pressure of the liquid and cavitation is caused. The flow is separated from the surface of the impeller 9 due to the growth of the cavity, causing separation to generate a vortex, and the fluctuation of the separation vortex also causes a pressure fluctuation, which causes a rapid increase in the drag force of the impeller 9 and a decrease in the lift force. If the cavitation bubbles collapse on the surfaces of the impeller 9, the duct 4, the guide vanes 11, etc., the pump performance will deteriorate, and the surfaces will be damaged by the erosion due to the impact pressure when the cavitation bubbles collapse, and noise will also be generated. And vibrations limit the high speed operation of the pump.

Therefore, in the present invention, the air inlet 13
Is provided in front of the impeller 9 and on the inner peripheral surface of the duct 4 near the blade tip where the speed of the impeller 9 is highest, and the air supply control means 19 opens and closes the air supply valve 15 according to the rotational speed of the impeller 9. Then, the air is supplied to the low-pressure portion on the rear surface of the impeller 9 through the air passage 14 from the air introduction port 13, and the water flow is separated from the surface of the impeller 9 by the cavitation generated by the high rotation of the impeller 9. Even if separation occurs, the surface of the impeller 9 is made to flow in a gas phase having a high pressure by the amount of the introduced air to suppress the increase of vortices, and the vortices are moved backward to reduce eddy resistance and pressure fluctuation due to vortices. As a result, the increase of the shape resistance of the impeller 9 is prevented, so that the deterioration of the pump performance can be prevented.
The cushioning effect (compressibility) due to the introduction of air reduces the impact pressure at the time of cavitation bubble collapse, preventing damage to the machine surface due to cavitation erosion, preventing noise and vibration, and thus speeding up pump operation. Since the operation is possible, the speed of the water jet propulsion device can be increased beyond the speed limit due to cavitation.

In the water jet propulsion device, unlike the ordinary pump, the inflow water into the duct 4 can utilize the dynamic pressure corresponding to the boat speed as the effective suction pressure of the impeller 9 due to the shape of the suction port 6, so that the cavitation can be prevented. The generation of air can be suppressed. Therefore, the air introduction amount calculation device 18 is programmed with an optimum air introduction amount according to not only the rotational speed of the impeller 9 but also the boat speed (suction characteristic). The opening / closing of the air supply valve 15 is controlled by the air introduction amount calculation device 18.

Regarding the air supply, if the suction pressure into the impeller 9 at the air introduction port 13 is a negative pressure sufficient for the optimum air introduction amount, the air is directly supplied from the air supply valve 15 by the atmospheric pressure. When the negative pressure is insufficient, air having a pressure higher than atmospheric pressure is supplied by a compressor or the like, and when the prime mover exhaust or the prime mover is a gas turbine engine, the air in the compressor part can be used. The combination of the pressure on the supply side and the opening area of the air introduction port 13 makes it possible to optimize the air inflow rate in the range of the optimum air introduction amount, and in this embodiment, as shown in FIG. Although 13 has a slit shape, this may be a hole arranged at a predetermined interval on the inner peripheral surface of the duct 4.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention, in which the duct 4 in front of the impeller 9 is shown.
This is an example of further downsizing the water jet propulsion device by introducing air from the central portion. An air inlet 13 is provided in front of the impeller 9 of a shaft case 20 surrounding the rotary drive shaft 12, and an air supply valve 15 is provided. Is provided so as to communicate with the flow path 3 side of the water sealing device 21 at the proximal end of the shaft case 20, and the gap between the shaft case 20 and the rotary drive shaft 12 forms an air passage 14, and the air supply control means 19 is provided. Depending on the rotation speed of the impeller and the boat speed, the air supply valve 15
The opening and closing of is controlled and air is supplied.

In the above-described first embodiment, the air is introduced from the low pressure portion near the blade tip of the impeller 9 so that the efficiency is high.
In the present embodiment, air is introduced from the central portion of the duct 4, but the duct 4 is small, the impeller 9 has a small blade width 22, and air is generated by a secondary flow in the radial direction on the blade surface generated by the centrifugal force generated by the rotation of the impeller 9. Can be sufficiently introduced to the wing tip, and the air passage 14 is not required on the outer circumference of the duct 4, so that the outer shape can be made smaller, and the water jet propulsion device suitable for a small high-speed boat can be provided.

(Third Embodiment) FIGS. 3 and 4 show a third embodiment of the present invention in which an inlet guide vane 23 having an air inlet 13 is provided on the front surface of the impeller 9. In FIG. 3, one end of the plurality of inlet guide vanes 23 is cantilevered from the inner wall of the duct 4 toward the center of the duct 4, and the other end is joined to the shaft case 20 at the center of the duct 4 to support the shaft case 20. The air inlet 13 is provided on the suction surface or the trailing edge of the inlet guide vane 23.
Is provided with a plurality of air introduction holes 13a, and the air introduction holes 13a extend from the air passage 14a formed in the cross section of the inlet guide vane 23 to the air passage 1 on the outer periphery of the duct 4.
4 to communicate with the air supply valve 15.

Therefore, in this embodiment, the position of the air introduction hole 13a can be freely set in the radial direction of the duct 4,
Since the air can be smoothly introduced into each part of the impeller 9 when the impeller 9 has a large blade width, it is suitable for a high-speed / large-flow water jet propulsion device having a large flow passage cross section. Since the setting of the air introduction port 13 in the circumferential direction of the duct is restricted as compared with the above, the continuity of the air introduction is reduced and the pressure change becomes large with respect to the rotation of the impeller 9, so that the number of the inlet guide vanes 23 is It is preferable that the flow path cross-sectional area is decreased or the resistance is increased in an allowable range, and it is possible to prevent the generation of vibration and non-uniform air inflow due to the unbalance of the fluid force between the inlet guide vane 23 and the impeller 9. In order to prevent this, it is preferable that the number of inlet guide vanes 23 is equal to or more than the number of blades of the impeller 9, or is an integer multiple of the number of impeller blades at equal intervals in the circumferential direction of the duct.

FIG. 4 shows an example in which the above-mentioned inlet guide vane 23 is a variable inlet guide vane 23a, and the variable inlet guide vane 23a is a vane shaft 24 integral with this.
Is rotatably supported by a vane bearing 25 provided in an air passage 14b formed on the outer periphery of the duct 4, and the air passage 14b and the air introduction hole 13a are provided in the cross section of the variable inlet guide vane 23a and the vane shaft 24. The formed air passage 14a communicates with each other via a vane bearing 25, and the vane shaft 24 has a drive arm 26,
A variable inlet connected to a vane variable device 28 composed of a guide ring 27 and an actuator (not shown), which is connected to each drive arm 26 by rotating the guide ring 27 concentrically with the duct 4 by the actuator. The pitch of the guide vanes 23a can be changed. Therefore, the angle of attack of the water flow with respect to the impeller 9 is controlled by the variable inlet guide vanes 23a in accordance with the rotation speed of the impeller 9 and the boat speed, thereby reducing the pump efficiency due to the change in the flow rate. This can be prevented, and the inflow angle of the air into the impeller 9 can be easily controlled, so that the control accuracy of the cavitation flow around the impeller 9 can be increased.

(Fourth Embodiment) FIG. 5 shows a cross section of an impeller blade according to a fourth embodiment of the present invention. In this embodiment, the impeller blade shape is formed into a super cavitating blade shape and water jet propulsion is performed. This is an example in which the device is made ultra-high-speed, and the super-cavitation blade 29 sets the usage state at ultra-high speed to positively cause cavitation.
As shown in Fig. 5, the cavity 30 has a cross-sectional shape suitable for a super cavitation state in which the length is longer than the length of the blade, and the leading edge of the blade is edge-shaped to cause cavitation. Back surface 31 (negative pressure surface)
Since everything is put in the cavity 30, the pressure of the back surface 31 is almost equal to the vapor pressure, and the lift 32 is designed to depend on the pressure of the pressure surface 33 rather than the back surface 31, but ultra high speed operation is possible. In the present invention, when the cavity 30 is small in the low speed range, the performance of the blade is extremely deteriorated. In the present invention, the air supply control means 19 introduces air in a predetermined low speed range to enlarge the cavity 30. Since it is possible to create a flow similar to that of a super cavitation state, it is possible to prevent performance deterioration, and also to prevent damage to the machine surface due to cavitation erosion and noise and vibration due to the cushioning effect of air introduction. it can.

The performance of the super cavitating wing varies greatly depending on the shape of the wing, and the degree of freedom in design is low because cavitation is generated by the wing itself, making it difficult to secure the strength of the wing and improve its performance. Although it is sensitive and its performance drops sharply when it is used at a speed deviating from the design point, in the present invention, the cavitation flow on the blade surface is controlled by the introduction of air into the impeller 9, so the degree of freedom in designing the blade shape is high. Therefore, it is possible to secure both the blade strength and improve the performance by, for example, making the cross-sectional shape of the front edge thick, and to prevent the increase of the shape resistance of the impeller 9 due to the change of the attack angle 34. Since it is possible to prevent a sharp drop in performance, the water jet propulsion device can be made to operate at an extremely high speed, and the variable inlet guide vane 23a of the third embodiment described above can be used. If use can be easily controlled attack angle 34, it is possible to improve the performance of the water jet propulsion apparatus in a broader speed range.

(Fifth Embodiment) FIG. 6 shows a fifth embodiment of the present invention in which the output shaft 35 of the high-speed prime mover 2a mounted on the hull 1 and the rotary drive shaft 12 of the impeller 9 are directly connected. A high-speed prime mover 2a is provided with a prime mover protection control device 37 for preventing excessive rotation of the high-speed prime mover 2a according to an output signal of a pressure detecting device 36 provided at the suction port 6. In the present invention, a high speed operation of the pump is possible. Even if the high speed prime mover 2a such as a gas turbine engine is used, an independent speed reducer having a large reduction ratio is not required, and the output shaft 3 of the high speed prime mover 2a is not required.
5 and the rotary drive shaft 12 of the impeller 9 can be directly connected to each other, and the power transmission system does not increase in size. Therefore, the power loss generated in the power transmission mechanism is small, and the responsiveness of the rotation speed control is fast.
Since the compatibility between the high-speed prime mover 2a and the pump is high, it is possible to improve the high-speed performance of the ship by making the water jet propulsion device smaller, lighter and more powerful.

When the intake port 6 is exposed above the water surface in a valley of waves during high-speed running and the water flowing into the duct 4 is interrupted, the high-speed prime mover 2a suddenly becomes unloaded during high-speed rotation, and therefore rotates. May rise and be damaged, and the inflow water is interrupted by the pressure signal proportional to the water pressure generated by the pressure detection device 36 provided in the suction port 6 and the rate signal proportional to the rate of change of the water pressure. The state of the motor protection control device 37 is detected, the rotation of the high-speed prime mover 2a is quickly decelerated to a safe speed, and over-rotation can be prevented to prevent damage to the high-speed prime mover 2a. In order to avoid that the rotation of the high-speed prime mover 2a is too low when the normal suction state is restored and the suction port 6 (propulsion device) becomes additional resistance of the boat, the prime mover protection control is performed according to the running speed. The device 37 is a motor control device (normal load). In concert with your), it is possible to prevent the speed variation of fast ocean-going travel time due to a rapid change in the suction state of the water.

(Sixth Embodiment) FIG. 7 shows a sixth embodiment of the present invention in which an impeller bearing 10 for rotatably supporting an impeller 9 is supported in the center of the duct 4 by a plurality of guide vanes 11. A tail cone 38 is supported on the rear portion of the impeller bearing 10 so as to be concentric with the injection nozzle 8 and slidable in the axial direction, and a hydraulic cylinder 39 incorporated inside the impeller bearing 10 and one end thereof coupled to the tail cone 38. The nozzle area changing means 42 is configured so that the hydraulic piston 40 is driven to slide the tail cone 38 by the pressure oil supply control by the hydraulic control valve 41, and the flow passage cross-sectional area of the injection nozzle 8 is increased or decreased. The hydraulic control valve 41 is controlled by the propulsion device control device 43.

In the water jet propulsion device, the propulsion efficiency changes depending on the speed ratio of the jet injection speed to the boat speed, and normally, the injection is performed in accordance with the jet injection speed at which the propulsion efficiency is highest at the high cruising speed (maximum cruising rating). Nozzle 8
The cross-sectional area is set, so when the boat is stopped or accelerating from a low speed range, the speed ratio increases, resulting in a decrease in efficiency. However, in particular, in the case of the hydrofoil shown in FIG. 10, the maximum thrust is required when the hull is levitated by accelerating from the low speed range to the wing speed, which is very disadvantageous. The control device 43 includes a rotation speed detection device 16 and a boat speed detection device 17 for the impeller 9.
The output signal of the operation signal calculates the cross-sectional area of the injection nozzle 8 that maximizes the propulsion efficiency according to the rotation speed of the impeller 9 and the boat speed, outputs a signal to the hydraulic control valve 41, and the tail cone 38 is slide-controlled. Since the jet injection speed can be optimized, acceleration performance can be improved, and a reduction in propulsion efficiency due to a change in boat speed can be prevented.

The propulsion device control device 43 is provided with an air introduction amount calculation device, controls the opening and closing of the air supply valve 15 to introduce an appropriate amount of air, and controls the cavitation flow around the impeller 9 to control the impeller 9. Enables high speed rotation,
Due to the compressibility (cushion effect) of the gas-liquid two-phase flow in the wake of the impeller 9 in the duct 4, it is possible to prevent cavitation erosion and the generation of noise and vibration. It is a bubble flow that is compressed and dispersed into small bubbles.
Since it has an effect of accelerating the water and expanding as the pressure decreases, it has the effect of accelerating the surrounding water, so that the thrust can be increased. It is preferable to control the increase / decrease in the cross-sectional area of the injection nozzle 8 in synchronization with the above-described control for preventing the reduction in the propulsion efficiency so that the maximum change in the cross-sectional area of the injection nozzle 8 can be obtained.

In this embodiment, the nozzle cross-sectional area is made variable by the tail cone 38 without changing the outer diameter of the injection nozzle 8. However, as another nozzle area changing means, the injection nozzle is finely divided in the circumferential direction. It is possible to make a variable injection nozzle of a type that is formed by overlapping long flaps that overlap each other and narrows the diameter by increasing the overlap of each flap at the injection nozzle outlet. Such a variable injection nozzle has a complicated mechanism and a large size. However, since the amount of change in the cross-sectional area of the nozzle can be increased, a water jet propulsion device suitable for higher speed large ships can be provided.

(Seventh Embodiment) FIG. 8 shows a seventh embodiment of the present invention, in which the ramp portion 44 and the lip portion 4 are provided on the ship bottom 5.
5 is provided at the base end of the suction port 6, and the flow path 3
The duct 4 forming the section smoothly changes from a rectangular suction port 6 to a circular cross-sectional shape in front of the impeller 9, and a flap 46 is supported by a support shaft 47 so as to be rotatable up and down, and a lip portion 45 is formed. The suction port shape changing means 50 is configured by the flap 46 being driven by the hydraulic cylinder 49 by the drive arm 48 that is connected to the support shaft 47 that is integral with the flap 46. Is controlled by the output signal of the propulsion device control device 43 via the hydraulic control valve 51.

The water jet propulsion device is suitable for high-speed boats because it can utilize the dynamic pressure corresponding to the boat speed as the effective suction pressure of the impeller 9, but when it accelerates rapidly from the low speed range, Suction port 6 for rising
Since the dynamic pressure is low, the suction performance is poor, and the turbulence of the flow around the suction port 6 and the inside of the duct 4 and the generation of cavitation reduce the propulsion efficiency. By lowering the flap 46 located at the lip portion 45 of the mouth 6, the effective area of the suction port 6 can be expanded and the dynamic pressure can be recovered by the flap 46 even at a low speed, so that the required amount of water can be smoothed. And the flap 46 is raised as the boat speed increases, and the effective suction pressure of the impeller 9 can be appropriately maintained while avoiding an increase in additional resistance due to the suction port 6, and therefore the angle of the flap 46 can be adjusted. Acceleration performance is improved by optimal control, and the balance between suction performance and additional resistance is adjusted according to the sailing condition to prevent propulsion efficiency from falling over a wide speed range. It can be, if minimum control additional resistance in particular depending on the watercraft speed during high-speed cruising, the consumption of shaft power is reduced, the cruising performance of the ship can be greatly improved.

The propulsion device control device 43 includes an air introduction amount calculation device, and controls the effective suction pressure of the impeller 9 and the optimization of the air introduction amount in synchronization with each other according to the rotation speed of the impeller 9 and the boat speed. However, the high-speed performance of the water jet propulsion device can be further improved.
If the propulsion device control device 43 is controlled in conjunction with the nozzle area changing means 42 of the embodiment, a higher performance water jet propulsion device can be obtained.

Although the example of the impeller having a single stage has been shown in the above embodiments, the present invention is not limited to this, and even if the impeller is arranged in multiple stages or an inducer is added. The present invention is applied by selecting the arrangement of the air inlets.

[0044]

According to the present invention, the following effects (a)
~ (I) is achieved.

(A) An appropriate amount of air according to the rotational speed of the impeller and the speed of the watercraft is introduced into the low pressure part of the impeller to prevent the shape resistance of the impeller from increasing due to the occurrence of cavitation and prevent the deterioration of the pump performance. In addition, the cushioning effect of the introduction of air prevents cavitation erosion and the generation of noise and vibration, thus enabling the pump to operate at high speeds beyond the speed limit due to cavitation, thus speeding up the water jet propulsion device. be able to.

(B) An air inlet is provided in the center of the duct in front of the impeller to make the outer diameter of the duct smaller, and to speed up the pump by introducing proper air to further reduce the size, weight and output. Therefore, it is possible to obtain a water jet propulsion device suitable for small high-speed ships.

(C) An inlet guide vane having an air inlet is provided on the front surface of the impeller, so that the air can be smoothly introduced into the impeller having a large blade width, and a pump with a large flow rate and a large flow rate can be operated at high speed. Therefore, it is possible to obtain a water jet propulsion device suitable for a large boat at high speed.

(D) By varying the pitch of the inlet guide vanes, the angle of attack of the water flow to the impeller can be controlled, and the pump efficiency resulting from the change in the flow rate of the inflow water depending on the rotation speed of the impeller and the boat speed. Can be prevented, and the control accuracy of the cavitation flow around the impeller can be enhanced by controlling the inflow angle of air into the impeller.

(E) By making the impeller into a super cavitating blade shape, the water jet propulsion device can be made to operate at an extremely high speed, and the introduction of air prevents cavitation erosion and the occurrence of noise and vibrations, and super cavitating It is possible to prevent the deterioration of performance at low speed peculiar to the wing and to increase the freedom of wing shape design by controlling the super cavitation flow on the wing surface to obtain a wing shape that has both wing performance and strength. Therefore, the impeller can be operated at a very high speed.

(F) By increasing the speed of the pump, even if a high-speed prime mover is used, a speed reducer with a large reduction ratio is unnecessary,
The pump can be directly connected to the high-speed prime mover, the power loss generated in the power transmission system is small, the responsiveness of the rotation speed control is fast, and the compatibility of the high-speed prime mover and the pump is high. By increasing the output, it is possible to increase the size of the ship and improve the high-speed performance.

(G) The pressure detecting device provided at the suction port detects the interrupted state of the inflow water, and the prime mover protection control device controls the rotation of the prime mover to prevent damage to the prime mover due to excessive rotation. Further, it is possible to prevent the additional resistance of the suction port to the boat from increasing due to insufficient rotation, and to prevent speed fluctuations during high-speed running.

(H) Since the nozzle area varying means can change the cross-sectional area of the injection nozzle according to the rotational speed of the impeller and the boat speed, the jet injection speed can be optimized in accordance with the running condition. Acceleration performance is improved, and it is possible to prevent a decrease in propulsion efficiency due to a change in boat speed.

(I) Since the shape of the suction port can be changed by the suction port shape varying means according to the rotational speed of the impeller and the boat speed to optimize the effective suction pressure of the impeller, acceleration performance is improved. However, it is possible to prevent a decrease in propulsion efficiency due to a change in the boat speed, and to minimize the additional resistance of the suction port to the boat during high-speed navigation, thereby significantly improving the cruising performance.

[Brief description of drawings]

FIG. 1 is a sectional view of a water jet propulsion device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a water jet propulsion device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a water jet propulsion device according to a third embodiment of the present invention.

4 is a sectional view showing another embodiment of the inlet guide vane 23 shown in FIG.

FIG. 5 is a sectional view of a super cavitating wing 29 of a fourth embodiment of the present invention.

FIG. 6 is a simplified sectional view of a water jet propulsion device according to a fifth embodiment of the present invention.

FIG. 7 is a sectional view of a water jet propulsion device according to a sixth embodiment of the present invention.

FIG. 8 is a sectional view of a water jet propulsion device according to a seventh embodiment of the present invention.

FIG. 9 is a simplified cross-sectional view of a conventional water jet propulsion ship.

FIG. 10 is a simplified cross-sectional view of a conventional water jet propulsion hydrofoil.

[Explanation of symbols]

 2 prime mover 2a high speed prime mover 4 duct 6 suction port 8 injection nozzle 9 impeller 11 guide vane 12 rotary drive shaft 13 air inlet port 13a air inlet hole 15 air supply valve 16 rotational speed detection device 17 boat speed detection device 18 air introduction amount calculation Device 19 Air supply control means 23 Inlet guide vane 23a Variable inlet guide vane 29 Super cavitating blade 36 Pressure detection device 37 Motor protection control device 42 Nozzle area variable means 43 Propulsion device control device 46 Flap 50 Suction port shape variable means

Claims (6)

[Claims] 1. In a water jet propulsion device in which an impeller driven to rotate is arranged in a duct having a suction port, and an injection nozzle is arranged behind the impeller, an air introduction port is provided in front of the impeller, The water jet propulsion device, wherein the air introduction port communicates with an air supply control means for controlling an air supply amount according to a rotation speed of an impeller and a boat speed. 2. The water jet according to claim 1, wherein an inlet guide vane having an air inlet is provided on the front surface of the impeller, and the inlet guide vane is fixed to the duct or is supported at a variable pitch. Propulsion device. 3. The water jet propulsion device according to claim 1 or 2, wherein the impeller is formed in a super cavitating blade shape. 4. A rotary drive shaft of an impeller is directly connected to an output shaft of a high-speed prime mover, a pressure detecting device is provided at a suction port, and an output signal of the pressure detecting device is provided for preventing excessive rotation of the prime mover. The water jet propulsion device according to claim 1, further comprising a prime mover protection control device. 5. The water jet propulsion device according to claim 1, wherein the injection nozzle includes nozzle area varying means for changing a cross-sectional area of the injection nozzle. 6. The water jet propulsion device according to claim 1, wherein the suction port is provided with suction port shape changing means for changing the shape of the suction port.