A ventilation and drag reduction device for an omni-rotation water jet propulsion device and a method of using the same

Abstract

The present invention relates to the technical field of ship propulsion, and discloses a ventilation and drag reduction device for an azimuth water jet propulsion device, comprising an azimuth water jet propulsion device, a ventilation well box and an azimuth ventilation and drag reduction device, wherein the azimuth ventilation and drag reduction device is connected to the bottom of the azimuth water jet propulsion device and is flush with the bottom of the azimuth water jet propulsion device, the ventilation well box is connected to the hull and the azimuth water jet propulsion device, and is wrapped around the outside of the azimuth ventilation and drag reduction device, a plurality of ventilation pipes are arranged on the ventilation well box near the azimuth water jet propulsion device, the ventilation pipes are uniformly distributed circumferentially around the azimuth water jet propulsion device, and the ventilation pipes are connected to the azimuth ventilation and drag reduction device, the present invention introduces air into the azimuth ventilation and drag reduction device and sprays it out, forms an air film under the interaction of buoyancy and the jet of the azimuth water jet propulsion device, isolates the high-speed jet from the hull, greatly reduces friction resistance, increases the thrust received by the ship, and improves the propulsion efficiency and the ship's maneuverability.

Description

Technical Field

[0001] The present invention relates to the technical field of ship propulsion, and in particular to a ventilation and drag reduction device for an omni-rotation water jet propulsion device and a use method thereof. Background Art

[0002] The fully rotating water jet propulsion device is a water jet propulsion device with a special structural form. Its propulsion working principle is similar to that of a traditional water jet propulsion device, that is, it utilizes the work of the impeller 13 and the contraction acceleration of the nozzle of the expansion chamber to generate an inlet and outlet momentum difference and generate thrust. Its characteristic is that the inlet and outlet are both located at the bottom of the propulsion device. When in operation, the propulsion device absorbs water from the center of the bottom and sprays water laterally from the outer periphery of the bottom.

[0003] like Figure 1 As shown, a conventional full-revolving water jet propulsion device 10 is installed on a well box 0, and a nozzle 11 of the full-revolving water jet propulsion device 10 is adjacent to the bottom of the well box 0. The angle between the jetting angle of the full-revolving propulsion device and the bottom of the ship is about 15 degrees, and the jetting speed exceeds 15m / s. The jetting water flows rub against the bottom of the well box 0, generating huge friction resistance, such as Figure 2 As shown in the figure, the shear stress of the downstream wall of the full-revolving water jet propulsion device nozzle generally exceeds 400Pa, resulting in the actual thrust received by the ship being much less than the thrust issued by the propulsion device. Through the small-scale ship model test, it can be obtained that the thrust reduction is as high as 0.2, that is, the actual thrust received by the ship is only 80% of the thrust issued by the propulsion device. At the same time, the nozzle of the full-revolving water jet propulsion device can rotate 360 ​​degrees in all directions, and the high shear stress area will change with the change of the nozzle position. Therefore, reducing the friction resistance of the bottom of the ship caused by the high-speed jet in all directions will greatly improve the propulsion efficiency and enhance the ship's maneuverability.

[0004] Therefore, there is no device capable of reducing the jet friction resistance of the full-rotation water jet propulsion device in the above-mentioned technology. Summary of the invention

[0005] The technical problem to be solved by the present invention is the problem of large jet friction resistance of the fully rotating water jet propulsion device in the prior art.

[0006] In order to solve the above-mentioned technical problems, the technical solution of the present invention is to provide a ventilation and drag reduction device for a full-revolving water jet propulsion device, comprising a full-revolving water jet propulsion device, a ventilation well box and a full-revolving ventilation and drag reduction device, the full-revolving water jet propulsion device comprising a nozzle, a diffusion chamber and an impeller, the full-revolving ventilation and drag reduction device is connected to the bottom of the full-revolving water jet propulsion device and is flush with the bottom of the full-revolving water jet propulsion device, the ventilation well box is wrapped around the outside of the full-revolving ventilation and drag reduction device and is connected to the full-revolving water jet propulsion device and the hull, the ventilation well box is provided with a boss at a position close to the full-revolving water jet propulsion device, and a ventilation pipe is provided on the boss, the ventilation pipes are evenly distributed circumferentially around the full-revolving water jet propulsion device, and the ventilation pipe is connected to the full-revolving ventilation and drag reduction device.

[0007] By adopting the above technical scheme, the ventilation well box is connected to the hull structure as an installation base of the full-revolving water jet propulsion device, connected to the full-revolving water jet propulsion device, bearing the weight of the full-revolving water jet propulsion device and the thrust generated by it, and an full-revolving ventilation and drag reduction device and a ventilation pipe are provided to introduce air into the full-revolving ventilation and drag reduction device and spray it out, forming an air film under the interaction of buoyancy and the jet of the full-revolving water jet propulsion device, isolating the high-speed jet from the hull, greatly reducing friction resistance, increasing the thrust received by the ship, and improving the propulsion efficiency and the ship's maneuverability.

[0008] Optionally, the full-rotation ventilation drag reduction device includes a orifice plate shell and a sealing plate, the orifice plate shell is provided with a ventilation chamber and a buoyancy chamber, the orifice plate shell is flush with the bottom of the full-rotation water jet propulsion device, the sealing plate covers the orifice plate shell, the buoyancy chamber is sealed and connected to the sealing plate, the buoyancy chamber is filled with air, the bottom of the ventilation chamber is provided with air holes for ventilation, the ventilation chamber is provided with a rectifying plate, and the rectifying plate is parallel to the bottom of the ventilation chamber.

[0009] Optionally, the air holes in the azimuth ventilation and drag reduction device are located downstream of the nozzle of the azimuth water jet propulsion device.

[0010] By adopting the above technical scheme, the full-rotation ventilation drag reduction device includes a stationary component and a rotating component respectively. The rotating component rotates synchronously with the nozzle of the full-rotation water jet propulsion device, so that in any propulsion direction, the air holes are located in the high shear stress area downstream of the full-rotation water jet propulsion device, thereby achieving a drag reduction effect. A plurality of ventilation pipes are arranged on the stationary component to ensure that the air pressure at the air holes can be kept stable in each propulsion direction, thereby achieving a stable drag reduction effect in all directions.

[0011] Optionally, the air holes are arranged obliquely or vertically so that air is discharged along the bottom plate, thereby reducing the difficulty of forming an air film.

[0012] Optionally, the sealing plate includes a cover plate, an inner sealing sleeve and an outer sealing sleeve, the inner sealing sleeve and the outer sealing sleeve are higher than the cover plate, and the cover plate, the inner sealing sleeve, the outer sealing sleeve and the ventilation well box together form a raised ventilation cavity, the inner sealing sleeve is connected to an inner side wall of the boss of the ventilation well box, and the outer sealing sleeve is connected to the other inner side wall of the boss of the ventilation well box.

[0013] Optionally, a plurality of rotary seals are provided between the inner sealing sleeve and an inner side wall of the boss of the ventilation well box, and between the outer sealing sleeve and the other inner side wall of the boss of the ventilation well box.

[0014] Optionally, a sealing partition is provided between the rotary seals, and a sealing cover plate is provided above the rotary seals.

[0015] By adopting the above technical solution, multiple sealing bushings and sealing plates are provided to prevent high-pressure air from leaking from the gaps between the moving and static components, thereby preventing the inflow of the full-rotation water jet propulsion device and the use effect of the ventilation and drag reduction device.

[0016] Optionally, a ventilation hole is provided at a position where the cover plate is connected to the ventilation chamber, and the ventilation pipe is connected to the ventilation chamber through the ventilation cavity and the ventilation hole.

[0017] Optionally, the ventilation pipe is externally connected to a high-pressure air source, and a one-way ventilation valve is provided in the ventilation pipe.

[0018] A method for using a ventilation and drag reduction device for an azimuth water jet propulsion device comprises the following steps:

[0019] Step 1: Adjust the high-pressure air pressure according to the draft of the ship so that the air pressure at the vent position is slightly greater than the water pressure. The high-pressure air pressure must be determined by calculation or test and set by the rectifier on the high-pressure air source;

[0020] Step 2: The full-revolving ventilation drag reduction device can be started before the full-revolving water jet propulsion device, or it can be started at the same time as the full-revolving water jet propulsion device. High-pressure gas enters the ventilation cavity composed of the ventilation well box and the sealing plate from the ventilation pipe, enters the ventilation chamber through the ventilation hole, and discharges water from the ventilation hole. The time taken for this step is the start-up time of the full-revolving ventilation drag reduction device;

[0021] Step 3: After the air emerges from the vent, under the interaction of buoyancy and the jet of the full-rotation water jet propulsion device, an air film is continuously formed downstream of the nozzle, isolating the high-speed jet from the bottom of the orifice plate shell, greatly reducing friction resistance;

[0022] Step 4: When the fully-revolving waterjet propulsion device turns the rudder, the pressure diffuser drives the fully-revolving ventilation and drag reduction device to rotate synchronously, always keeping the air hole at the downstream of the nozzle. The rotary seal ensures that high-pressure air only escapes through the air hole during the rudder turning process, preventing air from entering the fully-revolving waterjet propulsion device from the upstream along the gap between the moving and static parts, thereby affecting the propulsion performance. Several ventilation pipes are evenly distributed along the circumference of the ventilation well box, so that the air pressure at the air hole position can be kept roughly the same at any rudder turning angle, so that the air film remains relatively stable.

[0023] In summary, the present invention has at least one of the following beneficial effects:

[0024] 1. The full-revolving ventilation and drag reduction device introduces air into the air holes. Under the interaction of buoyancy and the jet of the full-revolving water jet propulsion device, an air film is continuously formed in the area, isolating the high-speed jet from the hull, greatly reducing friction resistance, increasing the thrust received by the ship, and improving propulsion efficiency and ship maneuverability.

[0025] 2. The rotating parts rotate synchronously with the nozzle of the fully rotating water jet propulsion device, so that in any propulsion direction, the air holes are located in the high shear stress area downstream of the fully rotating water jet propulsion device, which has a drag reduction effect; multiple ventilation pipes are arranged on the stationary parts to ensure that the air pressure at the air holes can be kept stable in each propulsion direction, so that it has a stable drag reduction effect in all directions.

[0026] 3. Set up multiple rotary seals to contact the sealing plate and the ventilation well box respectively, and press them through the sealing partition and the sealing cover plate to prevent high-pressure air from leaking from the gap between the moving and static parts, affecting the inflow of the full-rotating water jet propulsion device and the use effect of the ventilation and drag reduction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the installation of the existing full-rotation water jet propulsion device;

[0028] Figure 2 This is the shear stress cloud diagram of the bottom plate around the azimuth water jet propulsion device;

[0029] Figure 3 This is a schematic diagram of the installation of the full-rotation water jet propulsion device of the present invention;

[0030] Figure 4 It is a schematic diagram of the structure of the full-rotation ventilation and drag reduction device of the present invention;

[0031] Figure 5 for Figure 4 Schematic diagram of the enlarged structure of the middle ventilation cavity;

[0032] Figure 6 It is a schematic diagram of the top view of the structure of the orifice plate shell of the present invention;

[0033] Figure 7This is a schematic diagram of the installation structure of the present invention when viewed from above;

[0034] Figure 8 This is another schematic diagram of the air vent structure of the present invention;

[0035] Fig. 9 This is a schematic diagram of the top view of the sealing plate structure of the present invention;

[0036] In the figure: 0, well box; 1, ventilation well box; 2, full-rotation ventilation and drag reduction device; 3, sealing plate; 31, cover plate; 32, inner sealing bushing; 33, outer sealing bushing; 34, ventilation cavity; 35, ventilation hole; 4, orifice plate shell; 41, ventilation chamber; 42, buoyancy chamber; 43, air vent; 5a, 5b, rectifying plate; 6a, 6b, 6c, 6d, rotary seal; 7a, 7b, sealing partition; 8a, 8b, sealing cover plate; 10, full-rotation water jet propulsion device; 11, nozzle; 12, expansion chamber; 13, impeller. DETAILED DESCRIPTION

[0037] The following is combined with Figure 1-9 The present invention is described in further detail.

[0038] The present invention discloses a ventilation and drag reduction device for a fully rotating water jet propulsion device, referring to Figure 3-5 , including an all-revolving water jet propulsion device 10, a ventilation well box 1 and an all-revolving ventilation drag reduction device 2. The all-revolving water jet propulsion device 10 includes a nozzle 11, a diffusion chamber 12 and an impeller 13. The all-revolving ventilation drag reduction device 2 is connected to the bottom of the all-revolving water jet propulsion device 10 and is flush with the bottom of the all-revolving water jet propulsion device 10. The ventilation well box 1 is connected to the hull structure and serves as an installation base for the all-revolving water jet propulsion device 10. It is connected to the all-revolving water jet propulsion device 10 and bears the weight of the all-revolving water jet propulsion device 10 and the thrust generated by it. The ventilation well box is wrapped around the outside of the all-revolving ventilation drag reduction device 2. The ventilation well box 1 is provided with a boss at a position close to the all-revolving water jet propulsion device 10. The boss A vent pipe 9 is provided on the top, which is evenly distributed around the full-revolving water jet propulsion device 10 in the circumferential direction, and the vent pipe 9 is connected with the full-revolving ventilation and drag reduction device 2. A one-way vent valve is provided in the vent pipe 9, and an external high-pressure air source is connected, wherein the full-revolving ventilation and drag reduction device 2 is rigidly connected to the diffusion chamber 12 of the full-revolving water jet propulsion device 10, and can rotate synchronously with the diffusion chamber 12. By arranging the full-revolving ventilation and drag reduction device 2 and the vent pipe 9, air is introduced into the full-revolving ventilation and drag reduction device 2 and sprayed out, and an air film is formed under the interaction of buoyancy and the jet of the full-revolving water jet propulsion device 10, which isolates the high-speed jet from the hull, greatly reduces friction resistance, increases the thrust received by the ship, and improves the propulsion efficiency and the ship's maneuverability.

[0039] In a further embodiment, referring to Figure 4 and Figure 6The full-revolving ventilation drag reduction device 2 includes a perforated plate shell 4 and a sealing plate 3. The perforated plate shell 4 is provided with a ventilation chamber 41 and a buoyancy chamber 42. The perforated plate shell 4 is flush with the bottom of the full-revolving water jet propulsion device 10. The sealing plate 3 covers the perforated plate shell 4. The buoyancy chamber 42 is sealed and connected to the sealing plate 3. The buoyancy chamber 42 is filled with air. The bottom of the ventilation chamber 41 is provided with an air hole 43 for ventilation. The ventilation chamber 41 is provided with a rectifying plate. The rectifying plate is parallel to the bottom of the ventilation chamber 41. The buoyancy chamber 42 and the sealing plate are connected to each other. The plate 3 forms a closed space filled with air, which reduces the weight of the full-revolution ventilation drag reduction device 2 in the water, reduces the ventilation volume required for drag reduction, and shortens the start-up time of the full-revolution ventilation drag reduction device 2. The width of the ventilation chamber 41 is equivalent to the diameter of the full-revolution water jet propulsion device 10. In this embodiment, two rectifying plates are provided, wherein the rectifying plate 5a is arranged above the rectifying plate 5b, and the two are parallel, so that the pressure of each air hole 43 is equivalent. When installing the full-revolution ventilation drag reduction device 2, refer to Figure 7 The air hole 43 is located downstream of the nozzle 11 of the full-revolving water jet propulsion device 10, covering Figure 5 In the high shear stress region, the vent holes 43 are arranged vertically in this embodiment. Figure 8 The air holes 43 are arranged obliquely. By changing the air holes 43 from a vertical arrangement to an inclined arrangement, the air is discharged along the bottom plate, reducing the difficulty of forming an air film.

[0040] In a further embodiment, referring to Fig. 9 The sealing plate 3 includes a cover plate 31, an inner sealing sleeve 32 and an outer sealing sleeve 33. The inner sealing sleeve 32 and the outer sealing sleeve 33 are higher than the cover plate 31. The cover plate 31, the inner sealing sleeve 32, the outer sealing sleeve 33 and the ventilation well box 1 together form a raised ventilation cavity 34. The inner sealing sleeve 32 is connected to an inner side wall of the boss of the ventilation well box 1, and the outer sealing sleeve 33 is connected to the other inner side wall of the boss of the ventilation well box 1. A plurality of rotary seals are arranged between the inner sealing sleeve 32 and an inner side wall of the boss of the ventilation well box 1 and between the outer sealing sleeve 33 and the other inner side wall of the boss of the ventilation well box 1. Sealing partitions are arranged between the rotary seals. A sealing cover plate is arranged above the rotary seal. A ventilation hole 35 is opened at the position where the cover plate 31 is connected to the ventilation chamber 41. The ventilation pipe 9 is connected to the ventilation chamber 41 through the ventilation cavity 34 and the ventilation hole 35.

[0041] In this embodiment, the cover plate 31, the inner sealing bushing 32 and the outer sealing bushing 33 form a ventilation cavity 34 with the ventilation well box 1. The cover plate 31 is provided with a ventilation hole 35 at the position where the ventilation cavity 34 is connected to the ventilation chamber 41 of the orifice plate shell 4, connecting the two spaces. The buoyancy chamber 42 of the orifice plate shell 4 and the cover plate 31 of the sealing plate 3 form a closed space filled with air. The side of the outer sealing bushing 33 is connected to the rotary seal 6a and the rotary seal 6b. A sealing partition 7a is provided between the rotary seal 6a and the rotary seal 6b. A sealing partition 7a is provided above the rotary seal 6b. Cover plate 8a, the side of the inner sealing bushing 32 is in contact with the rotary seal 6c and the rotary seal 6d, a sealing partition 7b is arranged between the rotary seal 6c and the rotary seal 6d, a sealing cover plate 8b is arranged above the rotary seal 6d, the top of the outer sealing bushing 33 is sealedly connected to the sealing cover plate 8a, the top of the inner sealing bushing 32 is sealedly connected to the sealing cover plate 8b, the sealing partition and the sealing cover plate press the rotary seal to prevent high-pressure air from leaking from the gap between the dynamic and static parts, affecting the inflow of the full-rotation water jet propulsion device 10 and the use effect of the full-rotation ventilation and drag reduction device 2.

[0042] The present invention also discloses a method for using a ventilation and drag reduction device for an omni-rotation water jet propulsion device, comprising the following steps:

[0043] Step 1: Adjust the high-pressure air pressure according to the draft of the ship so that the air pressure at the air vent 43 is slightly greater than the water pressure. The high-pressure air pressure must be determined by calculation or test and set by the rectifier on the high-pressure air source.

[0044] Step 2: The full-revolving ventilation and drag reduction device 2 can be started before the full-revolving water jet propulsion device 10, or it can be started at the same time as the full-revolving water jet propulsion device 10. The high-pressure gas enters the ventilation cavity 34 composed of the ventilation well box 1 and the sealing plate 3 from the ventilation pipe 9, enters the ventilation chamber 41 through the ventilation hole 35, and discharges the water from the ventilation hole 43. The time taken for this step is the start-up time of the full-revolving ventilation and drag reduction device 2.

[0045] Step 3: After the air emerges from the air vents 43, under the interaction of buoyancy and the jet of the full-rotation water jet propulsion device 10, an air film continues to form downstream of the nozzle 11, isolating the high-speed jet from the bottom of the orifice plate shell 4, greatly reducing friction resistance.

[0046] Step 4: When the fully-revolving waterjet propulsion device 10 turns the rudder, the pressure diffuser 12 drives the fully-revolving ventilation and drag reduction device 2 to rotate synchronously, and always keeps the air hole 43 downstream of the nozzle 11. The rotary seal ensures that high-pressure air only escapes through the air hole 43 during the turning process, and prevents air from entering the fully-revolving waterjet propulsion device 10 from the upstream along the gap between the moving and static parts, thereby affecting the propulsion performance. A number of ventilation pipes 9 are evenly distributed along the circumference of the ventilation well box 1, so that the air pressure at the position of the air hole 43 can be kept roughly the same at any turning angle, so that the air film remains relatively stable.

[0047] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A ventilation and drag reduction device for an omni-rotating water jet propulsion device, characterized in that: The invention comprises an azimuth water jet propulsion device (10), a ventilation well box (1) and an azimuth ventilation drag reduction device (2), wherein the azimuth water jet propulsion device (10) comprises a nozzle (11), a pressure diffusion chamber (12) and an impeller (13), the azimuth ventilation drag reduction device (2) is connected to the bottom of the azimuth water jet propulsion device (10) and is flush with the bottom of the azimuth water jet propulsion device (10), the ventilation well box (1) is wrapped around the outside of the azimuth ventilation drag reduction device (2) and is connected to the azimuth water jet propulsion device (10) and a hull, the ventilation well box (1) is provided with a boss at a position close to the azimuth water jet propulsion device (10), the boss is provided with a ventilation pipe (9), the ventilation pipe (9) is uniformly distributed around the circumference of the azimuth water jet propulsion device (10), and the ventilation pipe (9) is connected to the azimuth ventilation drag reduction device (2); The full-revolving ventilation drag reduction device (2) comprises an orifice plate shell (4) and a sealing plate (3); a ventilation chamber (41) and a buoyancy chamber (42) are provided on the orifice plate shell (4); the orifice plate shell (4) is flush with the bottom of the full-revolving water jet propulsion device (10); the sealing plate (3) covers the top of the orifice plate shell (4); the buoyancy chamber (42) is sealedly connected to the sealing plate (3); the buoyancy chamber (42) is filled with air; a ventilation hole (43) is provided at the bottom of the ventilation chamber (41) for ventilation; a rectifying plate is provided in the ventilation chamber (41); the rectifying plate is parallel to the bottom of the ventilation chamber (41); The ventilation pipe (9) is connected to an external air source, and a one-way ventilation valve is provided in the ventilation pipe (9).

2. The ventilation and drag reduction device for the full-rotation water jet propulsion device according to claim 1, characterized in that: The air vent (43) in the azimuth ventilation and drag reduction device (2) is located downstream of the nozzle (11) of the azimuth water jet propulsion device (10).

3. The ventilation and drag reduction device for the full-rotation water jet propulsion device according to claim 1, characterized in that: The air holes (43) are arranged vertically or obliquely.

4. The ventilation and drag reduction device for an azimuth water jet propulsion device according to claim 1, characterized in that: The sealing plate (3) comprises a cover plate (31), an inner sealing sleeve (32) and an outer sealing sleeve (33); the inner sealing sleeve (32) and the outer sealing sleeve (33) are higher than the cover plate (31); the cover plate (31), the inner sealing sleeve (32), the outer sealing sleeve (33) and the ventilation well box (1) together form a raised ventilation cavity (34); the inner sealing sleeve (32) is connected to an inner side wall of a boss of the ventilation well box (1); and the outer sealing sleeve (33) is connected to the other inner side wall of the boss of the ventilation well box (1).

5. The ventilation and drag reduction device for the full-rotation water jet propulsion device according to claim 4, characterized in that: A plurality of rotary seals are provided between the inner sealing bushing (32) and an inner side wall of the boss of the ventilation well box (1), and between the outer sealing bushing (33) and another inner side wall of the boss of the ventilation well box (1).

6. The ventilation and drag reduction device for the full-rotation water jet propulsion device according to claim 5, characterized in that: A sealing partition is arranged between the rotary seals, and a sealing cover plate is arranged above the rotary seals.

7. The ventilation and drag reduction device for the full-rotation water jet propulsion device according to claim 4, characterized in that: A vent hole (35) is provided at a position where the cover plate (31) is connected to the ventilation chamber (41), and the ventilation pipe (9) is in communication with the ventilation chamber (41) through the ventilation cavity (34) and the vent hole (35).

8. The method for using the ventilation and drag reduction device for the azimuth water jet propulsion device according to claim 7, characterized in that: The steps include: Step 1: Adjust the air pressure according to the draft of the ship so that the air pressure at the air vent (43) is slightly greater than the water pressure. The air pressure must be determined by calculation or experiment and set by the rectifying device on the air source; Step 2: The full-revolving ventilation drag reduction device (2) may be started before the full-revolving water jet propulsion device (10), or may be started simultaneously with the full-revolving water jet propulsion device (10). Gas enters the ventilation cavity (34) formed by the ventilation well box (1) and the sealing plate (3) from the ventilation pipe (9), enters the ventilation chamber (41) through the ventilation hole (35), and water is discharged from the ventilation hole (43). The time taken for this step is the start-up time of the full-revolving ventilation drag reduction device (2); Step 3: After the air emerges from the air vent (43), an air film is continuously formed downstream of the nozzle (11) due to the interaction between the buoyancy and the jet of the full-rotation water jet propulsion device (10), isolating the high-speed jet from the bottom of the orifice plate shell (4); Step 4: When the azimuth water jet propulsion device (10) turns the rudder, the pressure diffuser (12) drives the azimuth ventilation and drag reduction device (2) to rotate synchronously, and the air vent (43) is always kept downstream of the nozzle (11).

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