Axial flow water jet propelling pump

Abstract

The application discloses an axial flow type water jet propelling pump, which comprises a pipeline, an impeller, a transmission shaft and a guide vane, the pipeline is provided with an inlet and an outlet, the impeller is arranged in the pipeline, the impeller comprises a plurality of impeller blades, and the side of the impeller blade facing the inlet or the outlet is formed in a sawtooth shape; the transmission shaft is fixedly connected with the impeller, the end of the transmission shaft away from the impeller penetrates through the pipeline and is used for being connected with an external power device to drive the impeller to rotate; the guide vane is arranged in the pipeline and located between the impeller and the outlet, the guide vane is provided with a plurality of guide vane blades, and the guide vane blades are fixedly connected with the pipeline. Compared with the prior art, the axial flow type water jet propelling pump provided by the application is designed in a sawtooth shape on the guide vane blades, the vortex shedding process at the sawtooth structure can be changed, the flow state of the fluid in the flow channel is improved, the flow noise caused by the vortex shedding is inhibited, and thus a better noise reduction effect of the water jet propelling pump is achieved.

Description

Technical Field

[0001] This invention relates to the field of marine vehicle propulsion technology, specifically to an axial-flow waterjet propulsion pump. Background Technology

[0002] As the core component of a waterjet propulsion system, the waterjet propulsion pump mainly consists of an inlet channel, guide vanes, impeller, outlet channel, and control system. Fluid is drawn into the pump's flow channel through the inlet channel, accelerated by the impeller's rotation, and then partially recovered by the guide vanes, converting it into axial velocity. The fluid then flows out of the pump through the outlet channel. By ejecting high-speed fluid towards the rear of the ship, the ship experiences a forward reaction force, thus propelling it forward.

[0003] Because the fluid's motion state changes drastically when accelerated by the impeller in a waterjet propulsion pump, the flow noise generated by the fluid pulsation pressure is also relatively high. However, due to the optimization of mechanical structure and the advancement of manufacturing technology, the mechanical noise and flow-induced vibration noise of waterjet propulsion pumps have been well controlled, resulting in flow noise becoming the main component of the noise in waterjet propulsion pumps.

[0004] Flow noise is the main component of the noise radiated outward by waterjet propulsion pumps. Currently, reducing the flow noise generated by complex flow in the flow channel of waterjet propulsion pumps is mainly based on changes to the guide vane structure. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose an axial flow water jet propulsion pump to solve the technical problem that axial flow water jet propulsion pumps generate large flow noise during operation.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] This invention provides an axial-flow water jet propulsion pump, comprising: a pipe having an inlet and an outlet; an impeller arranged inside the pipe, the impeller including multiple impeller blades, the impeller blades having a serrated structure on the side facing the inlet or the outlet; a drive shaft fixedly connected to the impeller, the end of the drive shaft away from the impeller passing through the pipe for connection to an external power device to drive the impeller to rotate; and guide vanes arranged inside the pipe and located between the impeller and the outlet, the guide vanes having multiple guide vane blades, the guide vane blades being fixedly connected to the pipe.

[0008] In some embodiments, the impeller, drive shaft, and guide vanes are arranged coaxially.

[0009] In some embodiments, multiple impeller blades are uniformly arranged around the axis of the drive shaft, and multiple guide vanes are also uniformly arranged around the axis of the drive shaft.

[0010] In some embodiments, the impeller blades are arranged at an angle to drive water from the inlet to the outlet, and the guide vanes are also arranged at an angle and in the opposite direction to the impeller blades.

[0011] In some embodiments, the guide vane has a mounting hole facing the impeller, and one end of the drive shaft is inserted into the mounting hole and rotatably connected to the guide vane.

[0012] In some embodiments, the drive shaft is rotatably and sealed to the pipe.

[0013] In some embodiments, a first rectifier cap is further included, which is fixedly connected to the end of the guide vane facing the outlet and is arranged coaxially with the guide vane.

[0014] In some embodiments, a connecting pipe is also included, one end of which is fixedly connected to a pipeline, a drive shaft passes through the connecting pipe and is rotatably connected to the connecting pipe in a sealed manner, and a second rectifier cap is formed at the end of the connecting pipe near the impeller.

[0015] In some embodiments, the serrated structure is located on the side of the impeller blade facing the outlet, and the line connecting the root and tip of the serrated structure is a straight line.

[0016] In some embodiments, the serrated structure is located on the side of the impeller blade facing the inlet, and the line connecting the root and tip of the serrated structure is an arc.

[0017] Compared with the prior art, the axial flow water jet propulsion pump provided by the present invention has a sawtooth design for the guide vane blades, which can change the vortex shedding process at the sawtooth structure, improve the flow state of the fluid in the flow channel, thereby suppressing the flow noise caused by vortex shedding, thus achieving a better noise reduction effect of the water jet propulsion pump. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an axial flow water jet propulsion pump according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the internal structure of an axial flow water jet propulsion pump according to an embodiment of the present invention;

[0020] Figure 3 yes Figure 2 A schematic diagram of the structure of a single impeller blade;

[0021] Figure 4 yes Figure 3 A diagram of the tooth-shaped structure of the sawtooth pattern.

[0022] Figure 5This is a noise level comparison diagram of Embodiment 1 of the axial flow water jet propulsion pump provided in this invention.

[0023] Figure 6 This is a schematic diagram of the structure of Embodiment 2 of the axial flow water jet propulsion pump provided in this invention;

[0024] Figure 7 yes Figure 6 A schematic diagram of the structure of a single impeller blade;

[0025] Figure 8 yes Figure 7 A diagram of the tooth-shaped structure of the sawtooth pattern.

[0026] Figure 9 This is a noise level comparison diagram of Embodiment 2 of the axial flow water jet propulsion pump provided in this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] To address the technical problem of significant flow noise generated during operation in existing axial-flow waterjet propulsion pumps, this invention provides an axial-flow waterjet propulsion pump that can reduce flow noise during operation.

[0029] It should be noted that the impeller described in this invention is used, but not limited to, axial-flow waterjet propulsion pumps, and can also be applied to other types of waterjet propulsion pumps. For ease of explanation, this invention only uses the application of the impeller to an axial-flow waterjet propulsion pump as an example. The principle of applying this impeller to other types of waterjet propulsion pumps is essentially the same as that applied to an axial-flow waterjet propulsion pump, and will not be elaborated here.

[0030] Example 1

[0031] Please see Figures 1 to 4 An axial flow water jet propulsion pump includes: a pipe 1A, an impeller 2A, a drive shaft 3A, and guide vanes 4A.

[0032] Pipe 1A has an inlet 11A and an outlet 12A, forming a flow channel between the inlet 11A and the outlet 12A. Water is drawn in through the inlet 11A and ejected through the outlet 12A, propelling the ship or other vessel forward.

[0033] Impeller 2A is arranged inside the pipe. Impeller 2A includes multiple impeller blades 21A. The side of the impeller blades 21A facing the inlet 11A or outlet 12A forms a sawtooth structure 211A. A gap as small as possible is formed between the impeller blades 21A and the pipe 1A, as long as it does not affect the rotation of the impeller blades 21A.

[0034] In this embodiment, the impeller blade 21A has a serrated structure 211A on the side facing the outlet 12A, i.e., the trailing edge. Furthermore, the line connecting the root and tip of the serrated structure 211A is a straight line, i.e., straight serrations are used.

[0035] Inspired by the wings of eagles in nature, this embodiment incorporates a biomimetic sawtooth design for the impeller blade 21A. The sawtooth structure 211A can make the vortex shedding process at the trailing edge of the impeller blade 21A more discrete, improving the flow state of the fluid in the flow channel, thereby suppressing the flow noise caused by vortex shedding, and thus achieving a better noise reduction effect for the water jet propulsion pump.

[0036] Conventional impellers form a vortex at the trailing edge, known as a "trail-induced vortex." However, due to the pressure difference between the blade surface and the back of the blade, the serrated structure 211A generates a pair of small vortices rotating in opposite directions at the groove of each serration, creating a low-speed zone near the root.

[0037] Meanwhile, the flow field velocity distribution in the wake region of the sawtooth structure 211A is more uniform than that of the traditional trailing edge structure. This is because the small vortices at the sawtooth groove mentioned above fully mix the high-speed pumped fluid, thereby making the axial velocity distribution of the fluid more uniform. The sawtooth structure 211A can significantly reduce the turbulent kinetic energy of the wake.

[0038] The vortex at the groove of the serrated structure 211A helps to promote the dissipation of the wake vortex, that is, to decompose the original "large vortex" into "small vortex". Therefore, the vortex intensity and turbulent kinetic energy in the wake region are significantly less than those of conventional structures, thereby reducing the flow noise of the waterjet propulsion pump across the entire frequency band.

[0039] The drive shaft 3A is fixedly connected to the impeller 2A. The end of the drive shaft 3A away from the impeller 2A passes through the pipe 1A and is used to connect with an external power unit, namely the power turbine of the aircraft or other power unit, to drive the impeller 2A to rotate, drive water to flow from the inlet 11A to the outlet 12A, and generate the driving force for the aircraft to move forward.

[0040] Guide vane 4A is arranged inside pipe 1A and located between impeller 2A and outlet 12A. Guide vane 4A has multiple guide vane blades 41A, which are fixedly connected to pipe 1 to secure guide vane 4A. The fluid (i.e., water) accelerated by impeller 2 is pumped out in a rotating manner. Guide vane 4A can correct the direction of the rotating fluid, causing the fluid to move axially and be ejected from outlet 12A. In other words, guide vane 4A serves to guide the flow.

[0041] In some embodiments, the impeller 2A, the drive shaft 3A, and the guide vanes 4A are arranged coaxially. Preferably, a plurality of impeller blades 21A are evenly arranged around the axis of the drive shaft 3A, and a plurality of guide vane blades 41A are also evenly arranged around the axis of the drive shaft 3A.

[0042] In some embodiments, the impeller blades 21A are arranged at an angle to drive water from the inlet 11A to the outlet 12A, while the guide vanes 41A are also arranged at an angle and in the opposite direction to the impeller blades 21A, such as... Figure 2 As shown.

[0043] In some embodiments, the guide vane 4A has a mounting hole facing the impeller 2A, and one end of the drive shaft 3A is inserted into the mounting hole and rotatably connected to the guide vane 4A. This mounting hole serves to support the end of the drive shaft 3A, reducing the influence of gravity on the drive shaft 3A and improving its straightness.

[0044] In some embodiments, the drive shaft 3A is rotatably sealed to the pipe 1A, and a dynamic sealing structure is provided between the two to ensure that the connection between the drive shaft 3A and the pipe 1A does not leak water when the drive shaft 3A rotates.

[0045] In some embodiments, the axial-flow water jet propulsion pump further includes a first rectifier cap 5A, which is fixedly connected to the guide vane 4A at the end facing the outlet 12A and is arranged coaxially with the guide vane 4A. The first rectifier cap 5A rectifies the flow of the fluid.

[0046] In some embodiments, the axial-flow water jet propulsion pump further includes a connecting pipe 6A, one end of which is fixedly connected to the pipe 1A. A drive shaft 3A passes through the connecting pipe 6A and is rotatably connected to the connecting pipe 6A in a sealed manner. A second rectifier cap 61A is formed at the end of the connecting pipe 6A near the impeller 2A. The second rectifier cap 61A and the first rectifier cap 5A are arranged symmetrically and have the same function: to rectify the fluid.

[0047] In one embodiment, the impeller blades 21A number 5, and the hub ratio is 0.3. The guide vane blades 41A number 7. The design operating condition is a flow rate Q = 40 m³ / s. 3 / h, rotational speed n=1500rpm. The tooth height h of the serrated structure is 4.2mm, and the tooth width λ is 3.36mm. The pipe 1A, impeller 2A, drive shaft 3A, guide vane 4A and other structures can be machined using an integrated CNC machine tool, or processed using 3D printing technology, or other feasible manufacturing methods.

[0048] In this embodiment, the novel impeller 2A achieves a total sound pressure level noise reduction of 4.96 dB compared to the traditional impeller in the 25-4000 Hz frequency range. See [link to noise reduction results] Figure 5 .

[0049] It should be noted that the sawtooth geometry is related to the boundary layer thickness. Under design conditions, the boundary layer thickness δ on the impeller blade surface of the waterjet propulsion pump mentioned in this invention is 1.4 mm. The boundary layer refers to a very thin layer of fluid near a solid wall in a flow field, dominated by fluid viscosity. In the boundary layer, the fluid at the bottom layer can adhere to the wall without slipping (i.e., the wall velocity is 0), and there is a large velocity gradient in the direction perpendicular to the wall.

[0050] Strictly speaking, there is no clear boundary between the boundary layer and the mainstream region. The outer edge of the boundary layer is usually defined as the thickness when the velocity reaches 99% of the mainstream velocity, and the vertical distance from this outer edge to the wall is called the boundary layer thickness.

[0051] The boundary layer thickness δ is estimated using the following formula:

[0052]

[0053] in, The Reynolds number represents the ratio of inertial forces to viscous forces in fluid flow.

[0054]

[0055] Where ρ is the fluid density, in kg / m³. 3 ;

[0056] U represents the flow velocity, measured in m / s.

[0057] L is the characteristic length, in meters (m).

[0058] μ is the dynamic viscosity, measured in Pa·s.

[0059] The sawtooth size requires estimation of the impeller boundary layer thickness. A sawtooth height to boundary layer thickness ratio (h / δ) of 2–4 provides some noise reduction, with h / δ=3 showing the best effect. A sawtooth width to sawtooth height ratio (λ / h) of 0.6–1.2 provides good noise reduction, with λ / h=0.8 showing the best effect, and the noise reduction effect weakens as the sawtooth width increases. Some experimental data are shown in the table below.

[0060] Water jet propulsion pump impeller blade serration size

[0061]

[0062] Example 2

[0063] Please see Figures 6 to 8 In this embodiment, the impeller blade 21B has a serrated structure 211B on the side facing the water inlet, i.e., the leading edge. Furthermore, the line connecting the root and tip of the serrated structure 211B is an arc, i.e., a circular arc serration is used. Other structures are the same as in Embodiment 1 and will not be described again.

[0064] Inspired by the wings of barn owls in nature, this embodiment incorporates a biomimetic sawtooth design for the impeller blade 21B structure. The leading edge sawtooth resembles the tip of a barb, which reduces the noise generated by the fluid by controlling the boundary layer when the fluid flows over the surface and suppressing unstable fluid caused by vortex shedding.

[0065] Flow noise is the main component of the noise radiated outward by waterjet propulsion pumps. When the impeller of a waterjet propulsion pump rotates at high speed, it generates irregular turbulence, and tail vortices are generated and shed at the trailing edge of the blades. The generation of these local turbulences radiates noise outward in the form of pressure waves. The impeller rotation of a waterjet propulsion pump has a significant impact on the pulsating pressure and flow noise of the fluid inside the pump. Generally speaking, the flow field distribution within the flow channel of a waterjet propulsion pump is relatively complex, with many vortices. These numerous vortices can form quadrupole sound sources, thus generating significant flow noise.

[0066] The leading edge of the barn owl's wings has a finely toothed, comb-like structure that generates tiny vortices during flight. These vortices help to streamline the airflow over the wings, "filtering" the air vortices across the wing surface into smaller vortices. This suppresses the generation of turbulent boundary layer noise, reduces airflow separation, thereby reducing turbulence and ultimately reducing noise generation.

[0067] Therefore, inspired by the structure of a barn owl's wings, this embodiment incorporates a biomimetic sawtooth design for the leading edge of the waterjet propulsion pump impeller. Experiments and simulations revealed that when the incoming flow contacts the sawtooth structure 211B, separation occurs not only vertically but also along the unfolding direction of the impeller 2B. This weakens the unsteady load distributed on the leading edge of the impeller blades 21B, which is the main reason for reducing the low-frequency rotational noise of the impeller 2B. Simultaneously, the arc-shaped sawtooth structure 211B can decompose large eddies into numerous smaller eddies, thereby suppressing instabilities within the shear layer of the separated fluid.

[0068] In this embodiment, the serrated structure 211B is related to the boundary layer thickness on the impeller 2B surface. Under different flow conditions, the variation in boundary layer thickness is mainly affected by factors such as flow type (laminar or turbulent), Reynolds number, external flow conditions, and surface characteristics of the object. For a waterjet propulsion pump, the flow channel is dominated by turbulence, and the Reynolds number on the impeller 2B surface is related to the rotational speed, impeller diameter, and impeller surface roughness.

[0069] Under normal circumstances, the boundary layer thickness is estimated using an empirical formula, where is the characteristic length. In this invention, the maximum chord length of impeller 2B is taken as the Reynolds number. Generally, the boundary layer thickness increases with increasing rotational speed, and the sawtooth structure 211B needs to be designed specifically for the operating conditions of the waterjet propulsion pump.

[0070] The ratio of the sawtooth height h to the boundary layer thickness of the sawtooth structure 211B is in the range of 2 to 4, and the ratio of the sawtooth width λ to the sawtooth height h is in the range of 0.6 to 1.2.

[0071] The sawtooth structure 211B has a circular arc connecting the tooth root and the tooth tip. The center of the arc is the intersection of the perpendicular bisector of the line connecting the tooth tip and the tooth root and the horizontal line where the tooth root is located. The radius refers to the distance between the center and the tooth tip or tooth root. Taking a certain pump as an example, the radius of the arc-shaped sawtooth is 5.04 mm.

[0072] Impeller 2B is obtained by projecting the impeller leading edge contour line onto the axial plane of the water jet propulsion pump, obtaining each sawtooth plane with the contour line as the edge line, using each sawtooth plane as the reference plane, and rotating and cutting off the complete impeller blade with the axis of the water jet propulsion pump as the rotation axis.

[0073] In one embodiment, the sawtooth structure 211B has a sawtooth height h of 4.2 mm and a tooth width λ of 3.36 mm. The impeller 2B has a diameter of 100 mm, 5 impeller blades, a hub ratio of 0.3, and 7 guide vanes on the water jet propulsion pump. Its design operating condition is: flow rate Q = 40 m³ / s. 3 / h, rotational speed n=1500rpm.

[0074] Please see Figure 9In this embodiment, the axial-flow waterjet propulsion pump with an impeller 2 designed to resemble a barn owl's wings can effectively reduce the flow noise of the waterjet propulsion pump and optimize the flow field distribution within the pump. It performs particularly well in the first four blade frequencies, reducing the sound pressure level by 7.12 dB, 15.34 dB, 3.52 dB, and 15.00 dB respectively, significantly improving the pump's acoustic stealth performance. Numerical calculations show that the impeller 2 provided in this embodiment achieves a total sound pressure level reduction of 10.93 dB compared to traditional impellers in the 25-100 Hz frequency range.

[0075] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An axial-flow water jet propulsion pump, characterized in that, include: A pipe having an inlet and an outlet; An impeller is arranged inside the pipe. The impeller includes multiple impeller blades. The side of the impeller blade facing the water inlet forms a serrated structure, and the line connecting the root and tip of the serrated structure is an arc. Alternatively, the side of the impeller blade facing the water outlet forms a serrated structure, and the line connecting the root and tip of the serrated structure is a straight line. A drive shaft is fixedly connected to the impeller, and one end of the drive shaft away from the impeller passes through the pipe for connection to an external power device to drive the impeller to rotate. A guide vane is arranged inside the pipe and located between the impeller and the outlet. The guide vane has multiple guide vane blades, and the guide vane blades are fixedly connected to the pipe.

2. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, The impeller, the drive shaft, and the guide vanes are arranged coaxially.

3. The axial-flow waterjet propulsion pump according to claim 2, characterized in that, The multiple impeller blades are evenly arranged around the axis of the drive shaft, and the multiple guide vane blades are also evenly arranged around the axis of the drive shaft.

4. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, The impeller blades are arranged at an angle to drive water from the inlet to the outlet, and the guide vanes are also arranged at an angle with the angle opposite to that of the impeller blades.

5. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, The guide vane has a mounting hole facing the impeller, and one end of the drive shaft is inserted into the mounting hole and rotatably connected to the guide vane.

6. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, The drive shaft is rotatably and sealed to the pipeline.

7. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, It also includes a first rectifier cap, which is fixedly connected to the end of the guide vane facing the outlet and is arranged coaxially with the guide vane.

8. The axial-flow waterjet propulsion pump according to claim 1, characterized in that, It also includes a connecting pipe, one end of which is fixedly connected to the pipeline, the drive shaft passes through the connecting pipe and is rotatably and sealed to the connecting pipe, and the end of the connecting pipe near the impeller forms a second rectifier cap.

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