Axial flow type water jet propulsion pump

Abstract

The invention discloses an axial-flow type water-jet propulsion pump which comprises a pipeline, an impeller, a transmission shaft and a guide vane, and the pipeline is provided with a water inlet and a water outlet; the impeller is arranged in the pipeline and comprises a plurality of impeller blades, and the sides, facing the water inlet or the water outlet, of the impeller blades form a zigzag structure; the end, away from the impeller, of the transmission shaft 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 water 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 propulsion pump provided by the invention has the advantages that the guide vane blades are designed in a sawtooth shape, the vortex falling process at the sawtooth-shaped structure can be changed, and the flowing state of fluid in a flow channel is improved, so that the flow noise caused by vortex falling is inhibited, and the good noise reduction effect of the water-jet propulsion pump is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of marine vehicle propulsion systems, and in particular to an axial-flow water jet propulsion pump. Background Art

[0002] As the core component of the waterjet propulsion system, the waterjet pump is mainly composed of an inlet channel, guide vanes, impellers, an outlet channel and a control system. The fluid is sucked into the channel of the propulsion pump through the inlet channel, and the fluid is accelerated by the rotation of the impeller. Then, part of the rotational energy of the fluid is recovered through the guide vanes, converted into axial speed, and then flows out of the waterjet pump through the outlet channel. By spraying high-speed fluid to the rear of the hull, the hull is subjected to a forward reaction force, thereby enabling the ship to sail forward.

[0003] Since the motion state of the fluid in the flow channel of the water jet pump changes dramatically when it is accelerated by the impeller, the flow noise level generated by the fluid pulsation pressure is also high. Due to the optimization of mechanical structure and the advancement of production and processing technology, the mechanical noise and flow-induced vibration noise of the water jet pump have been well controlled, resulting in flow noise becoming the main component of the noise of the water jet pump among the noise sources of the water jet pump.

[0004] Flow noise is the main component of the noise radiated outward by the water jet pump. How to reduce the flow noise generated by the complex flow in the flow channel of the water jet pump is currently mainly based on the change of the guide vane structure. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and to provide an axial flow water jet propulsion pump to solve the technical problem in the prior art that the axial flow water jet propulsion pump generates relatively large flow noise during operation.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: The present invention provides an axial-flow water jet propulsion pump, comprising: a pipeline, the pipeline having a water inlet and a water outlet; an impeller, the impeller is arranged in the pipeline, the impeller comprises a plurality of impeller blades, and the impeller blades form a sawtooth structure on the side facing the water inlet or the water outlet; a transmission shaft, the transmission shaft is fixedly connected to the impeller, and one end of the transmission shaft away from the impeller passes through the pipeline and is used to be connected to an external power device to drive the impeller to rotate; a guide vane, the guide vane is arranged in the pipeline and is located between the impeller and the water outlet, the guide vane has a plurality of guide vane blades, and the guide vane blades are fixedly connected to the pipeline.

[0007] In some embodiments, the impeller, the transmission shaft and the guide vanes are coaxially arranged.

[0008] In some embodiments, the plurality of impeller blades are evenly arranged around the axis of the transmission shaft, and the plurality of guide vane blades are also evenly arranged around the axis of the transmission shaft.

[0009] In some embodiments, the impeller blades are arranged tilted to drive water to flow from the water inlet to the water outlet, and the guide vane blades are also arranged tilted and the tilting direction is opposite to that of the impeller blades.

[0010] In some embodiments, the guide vane has a mounting hole facing the impeller, and one end of the transmission shaft is inserted into the mounting hole and is rotatably connected to the guide vane.

[0011] In some embodiments, the drive shaft is rotationally sealed to the pipe.

[0012] In some embodiments, a first straightening cap is further included, which is fixedly connected to one end of the guide vane facing the water outlet and is coaxially arranged with the guide vane.

[0013] In some embodiments, it also includes a connecting pipe, one end of which is fixedly connected to the pipeline, the transmission shaft passes through the connecting pipe and is sealed and rotatably connected to the connecting pipe, and one end of the connecting pipe close to the impeller forms a second fairing cap.

[0014] In some embodiments, the sawtooth structure is located on the side of the impeller blade facing the water outlet, and the line connecting the tooth root and the tooth tip of the sawtooth structure is a straight line.

[0015] In some embodiments, the sawtooth structure is located on the side of the impeller blade facing the water inlet, and the line connecting the tooth root and the tooth tip of the sawtooth structure is an arc line.

[0016] Compared with the prior art, the axial-flow water jet propulsion pump provided by the present invention has a serrated design for the guide vane blades, which can change the vortex shedding process at the serrated structure, improve the flow state of the fluid in the flow channel, thereby suppressing the flow noise caused by vortex shedding, thereby achieving a better noise reduction effect of the water jet propulsion pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic structural diagram of a first embodiment of an axial-flow water jet propulsion pump provided by an embodiment of the present invention; Figure 2 Schematic diagram of the internal structure of the first embodiment of the axial flow water jet propulsion pump provided by the embodiment of the present invention; Figure 3 yes Figure 2 Schematic diagram of the structure of a single impeller blade; Figure 4 yes Figure 3 Tooth structure diagram of the sawtooth structure; Figure 5 is a noise level comparison diagram of Example 1 of the axial flow water jet propulsion pump provided by an embodiment of the present invention; Figure 6 is a structural schematic diagram of a second embodiment of an axial-flow water jet propulsion pump provided in an embodiment of the present invention; Figure 7 yes Figure 6 Schematic diagram of the structure of a single impeller blade; Figure 8 yes Figure 7 Tooth structure diagram of the sawtooth structure; Fig. 9 It is a noise level comparison diagram of the second embodiment of the axial flow water jet propulsion pump provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] In order to solve the technical problem in the prior art that an axial-flow water jet propulsion pump generates relatively large flow noise during operation, the present invention provides an axial-flow water jet propulsion pump capable of reducing flow noise during operation.

[0020] It should be noted that the impeller of the present invention is used for but not limited to axial flow water jet pumps, and can also be applied to other types of water jet pumps. For the convenience of explanation, in the present invention, only the application of the impeller to the axial flow water jet pump is used as an example for explanation, and the principle of the application of the impeller to other types of water jet pumps is substantially the same as that of the application to the axial flow water jet pump, and will not be repeated here.

[0021] Example 1 See also Figures 1 to 4 The axial-flow water jet pump comprises a pipeline 1A, an impeller 2A, a transmission shaft 3A and a guide vane 4A.

[0022] The pipe 1A has a water inlet 11A and a water outlet 12A, and a flow channel is formed between the water inlet 11A and the water outlet 12A. Water is sucked in from the water inlet 11A and ejected from the water outlet 12A, thereby propelling a ship or other craft forward.

[0023] The impeller 2A is arranged in the pipeline, and includes a plurality of impeller blades 21A, and the impeller blades 21A form a sawtooth structure 211A on the side facing the water inlet 11A or the water outlet 12A. A gap as small as possible is formed between the impeller blades 21A and the pipeline 1A as long as it does not affect the rotation of the impeller blades 21A.

[0024] In this embodiment, the side of the impeller blade 21A facing the water outlet 12A, that is, the trailing edge, forms a sawtooth structure 211A, and the line connecting the tooth root and the tooth tip of the sawtooth structure 211A is a straight line, that is, a straight tooth sawtooth is adopted.

[0025] This embodiment is inspired by the wings of a goshawk in nature and adopts a bionic serrated design for the structure of the impeller blade 21A. The serrated structure 211A can make the vortex shedding process at the trailing edge of the impeller blade 21A discrete, improve 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 of the water jet propulsion pump.

[0026] Conventional impellers will form a circle of vortex at the trailing edge, called the "trailing edge induced vortex", while the sawtooth structure 211A will produce a pair of small vortices rotating in the opposite direction at the groove of each sawtooth due to the pressure difference between the blade surface and the back of the blade, and a low-speed area will be generated near the root.

[0027] At the same time, the flow field velocity distribution in the wake area 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 grooves mentioned above fully mix the fluid pumped out at high speed, 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.

[0028] The vortex at the groove of the sawtooth 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 area are significantly smaller than those of the conventional structure, thereby reducing the flow noise of the water jet propulsion pump in the full frequency band.

[0029] The transmission shaft 3A is fixedly connected to the impeller 2A, and one end of the transmission shaft 3A away from the impeller 2A passes through the pipe 1A, and is used to be connected to an external power device, that is, the power turbine of the aircraft or other power device to drive the impeller 2A to rotate, drive water to flow from the water inlet 11A to the water outlet 12A, and generate driving force for the aircraft to move forward.

[0030] The guide vane 4A is arranged in the pipeline 1A and is located between the impeller 2A and the water outlet 12A. The guide vane 4A has a plurality of guide vane blades 41A. The guide vane blades 41A are fixedly connected to the pipeline 1 to fix the guide vane 4A. The fluid (i.e., water) accelerated by the impeller 2 is pumped out backward while rotating. The guide vane 4A can correct the direction of the rotating fluid, so that the fluid moves axially and is ejected from the water outlet 12A. That is, the guide vane 4A plays a role in guiding the flow.

[0031] In some embodiments, the impeller 2A, the transmission shaft 3A and the guide vane 4A are coaxially arranged. Preferably, a plurality of impeller blades 21A are evenly arranged around the axis of the transmission shaft 3A, and a plurality of guide vane blades 41A are also evenly arranged around the axis of the transmission shaft 3A.

[0032] In some embodiments, the impeller blades 21A are arranged tilted to drive water from the water inlet 11A to the water outlet 12A, and the guide vane blades 41A are also arranged tilted and the tilt direction is opposite to that of the impeller blades 21A. Figure 2 shown.

[0033] In some embodiments, the guide vane 4A has a mounting hole facing the impeller 2A, and one end of the transmission shaft 3A is inserted into the mounting hole and rotatably connected to the guide vane 4A. The mounting hole plays a role in supporting the end of the transmission shaft 3A, reducing the influence of gravity on the transmission shaft 3A, and improving the straightness of the transmission shaft 3A.

[0034] In some embodiments, the transmission shaft 3A is rotatably sealed with the pipeline 1A, and a dynamic sealing structure is provided between the two to ensure that the connection between the transmission shaft 3A and the pipeline 1A does not leak when the transmission shaft 3A rotates.

[0035] In some embodiments, the axial flow water jet pump further includes a first straightening cap 5A, which is fixedly connected to the end of the guide vane 4A facing the water outlet 12A and is coaxially arranged with the guide vane 4A. The first straightening cap 5A straightens the fluid.

[0036] 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 pipeline 1A, and the transmission shaft 3A passes through the connecting pipe 6A and is sealed and rotatably connected to the connecting pipe 6A. The end of the connecting pipe 6A close to the impeller 2A forms a second rectifying cap 61A, and the second rectifying cap 61A is symmetrically arranged with the first rectifying cap 5A, and both have the same function of rectifying the fluid.

[0037] In one embodiment, the number of impeller blades 21A is 5, and the hub ratio is 0.3. The number of guide vane blades 41A is 7. The design condition is flow rate Q=40m 3 / h, speed n=1500rpm. The tooth height h of the sawtooth structure is 4.2mm, and the tooth width λ is 3.36mm. The structures such as the pipeline 1A, the impeller 2A, the transmission shaft 3A, and the guide vane 4A can be processed by an integrated CNC machine tool, or by using 3D printing technology, or by other feasible manufacturing and processing methods.

[0038] In this embodiment, the new impeller 2A can achieve a total sound pressure level noise reduction of 4.96 dB in the 25-4000 Hz frequency range compared to the traditional impeller. Figure 5 .

[0039] It should be noted that the geometric dimensions of the sawtooth are related to the thickness of the boundary layer. Under the design conditions, the boundary layer thickness δ of the impeller blade surface of the water jet propulsion pump mentioned in the present invention is 1.4 mm. The boundary layer refers to a thin layer of fluid near the solid wall in the flow field, in which the viscosity of the fluid plays a dominant role. In the boundary layer, the bottom fluid of the boundary layer can adhere to the wall without slipping (that is, the wall velocity is 0), and there is a large velocity gradient in the direction perpendicular to the wall.

[0040] Strictly speaking, there is no obvious boundary between the boundary layer and the mainstream area. The thickness when the velocity reaches 99% of the mainstream velocity is usually used as the outer edge of the boundary layer, and the vertical distance from the outer edge to the wall is called the boundary layer thickness.

[0041] The boundary layer thickness δ is estimated by the following formula:

[0042] in, is the Reynolds number, which represents the ratio of inertial force to viscous force in fluid flow.

[0043] Where ρ is the fluid density in kg / m 3 ; U is the flow velocity in m / s; L is the characteristic length, in meters; μ is the dynamic viscosity, and its unit is Pa·s.

[0044] The sawtooth size needs to estimate the thickness of the impeller boundary layer first. The ratio of sawtooth height to boundary layer thickness h / δ has a certain noise reduction effect in the range of 2 to 4, and the best noise reduction effect is when h / δ=3. The ratio of sawtooth width to sawtooth height λ / h has a good noise reduction effect in the range of 0.6 to 1.2, and the best noise reduction effect is when λ / h=0.8. The noise reduction effect decreases with the increase of sawtooth width. Some experimental data are shown in the table below.

[0045] Waterjet pump impeller blade serration size

[0046] Example 2 See also Figures 6 to 8 In this embodiment, the side of the impeller blade 21B facing the water inlet, that is, the leading edge, forms a sawtooth structure 211B. And the line connecting the tooth root and the tooth tip of the sawtooth structure 211B is an arc line, that is, a circular arc sawtooth is used. The other structures are the same as those in the first embodiment and will not be repeated.

[0047] This embodiment is inspired by the wings of barn owls in nature and adopts a bionic serration design for the impeller blade 21B structure. The leading edge serration is similar to a barbed tip, which controls the boundary layer of the fluid when it flows over the surface and suppresses the unstable fluid caused by vortex shedding, thereby reducing the noise generated by the fluid.

[0048] Flow noise is the main component of the noise radiated outward by the waterjet pump. When the impeller of the waterjet pump rotates at high speed, irregular turbulence will be generated, and at the same time, tail vortex shedding will occur at the trailing edge of the blade. The generation of these local turbulences will radiate noise outward in the form of pressure waves. The rotation of the impeller of the waterjet pump has a considerable impact on the pulsating pressure and flow noise of the fluid in the pump. Generally speaking, the flow field distribution in the flow channel of the waterjet pump is relatively complex, with more vortices, and more vortices will form quadrupole sound sources, thus generating greater flow noise.

[0049] The leading edge of the barn owl's wings has a fine-tooth comb structure that can generate tiny vortices during flight. These vortices help to smooth the airflow through the wings, so that the air vortices flowing over the wing surface are "filtered" into smaller vortices, which can suppress the generation of turbulent boundary layer noise, reduce airflow separation, and thus reduce the generation of turbulence, thereby reducing the generation of noise.

[0050] Therefore, this embodiment is inspired by the structure of the wing of the barn owl and performs a bionic sawtooth design on the leading edge of the water jet propulsion pump impeller. Through experiments and simulation calculations, it is found that when the incoming flow contacts the sawtooth structure 211B, separation occurs not only in the vertical direction, but also along the expansion direction of the impeller 2B, which will weaken the unsteady load distributed on the leading edge of the impeller blade 21B. This is the main reason for reducing the low-frequency noise of the impeller 2B rotation. At the same time, the arc-shaped sawtooth structure 211B can decompose large vortices into a large number of small vortices, thereby suppressing the instability in the shear layer of the separated fluid.

[0051] In this embodiment, the sawtooth structure 211B is associated with the boundary layer thickness on the surface of the impeller 2B. Under different flow conditions, the change 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 water jet propulsion pump, turbulence is dominant in the flow channel, and the Reynolds number on the surface of the impeller 2B is related to the rotation speed, impeller diameter, and impeller surface roughness.

[0052] In general, the boundary layer thickness is estimated using an empirical formula, where is the characteristic length, and the present invention takes the maximum chord length of the impeller 2B as the Reynolds number. Generally speaking, the boundary layer thickness will become thicker as the rotation speed increases, and the sawtooth structure 211B needs to be designed according to the working conditions of the water jet propulsion pump.

[0053] The ratio of the sawtooth height h of the sawtooth structure 211B to the boundary layer thickness 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.

[0054] The line connecting the tooth root and the tooth tip of the sawtooth structure 211B is an arc, the center of the circle 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, and the radius refers to the distance between the center of the circle and the tooth tip or tooth root. Taking a pump as an example, the radius of the arc sawtooth is 5.04mm.

[0055] Impeller 2B is obtained by projecting the contour line of the impeller leading edge onto the axial plane of the water jet propulsion pump, obtaining each sawtooth plane with the contour line as the edge line, rotating and cutting the complete impeller blades with each sawtooth plane as the reference plane and the axis of the water jet propulsion pump as the rotation axis.

[0056] 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 diameter of the impeller 2B is 100 mm, the number of impeller blades 21B is 5, the hub ratio is 0.3, and the number of guide vanes of the water jet propulsion pump is 7. The design working condition is: flow rate Q = 40m 3 / h, speed n=1500rpm.

[0057] See also Fig. 9 In this embodiment, the axial flow water jet pump with the impeller 2 designed to imitate the wings of a barn owl can effectively reduce the flow noise of the water jet pump and optimize the flow field distribution in the water jet pump. In particular, it performs well in the first four blade frequencies, and can reduce the sound pressure levels of the first four blade frequencies by 7.12dB, 15.34dB, 3.52dB, and 15.00dB, respectively, greatly improving the stealth performance of the pump sound. After numerical calculation research, the total sound pressure level noise reduction level of the impeller 2 provided in this embodiment can reach 10.93dB relative to the traditional impeller in the frequency range of 25-100Hz.

[0058] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An axial flow water jet pump, characterized in that: include: a pipeline having a water inlet and a water outlet; An impeller, the impeller being arranged in the pipeline, the impeller comprising a plurality of impeller blades, the impeller blades forming a sawtooth structure on one side facing the water inlet or the water outlet; A transmission shaft, the transmission shaft is fixedly connected to the impeller, one end of the transmission shaft away from the impeller passes through the pipeline and is used to be connected to an external power device to drive the impeller to rotate; A guide vane is arranged in the pipeline and located between the impeller and the water outlet. The guide vane has a plurality of guide vane blades, and the guide vane blades are fixedly connected to the pipeline.

2. The axial flow water jet pump according to claim 1, characterized in that: The impeller, the transmission shaft and the guide vane are coaxially arranged.

3. The axial flow water jet propulsion pump according to claim 2, characterized in that: The plurality of impeller blades are evenly arranged around the axis of the transmission shaft, and the plurality of guide vane blades are also evenly arranged around the axis of the transmission shaft.

4. The axial flow water jet propulsion pump according to claim 1, characterized in that: The impeller blades are arranged tilted to drive water to flow from the water inlet to the water outlet, and the guide vane blades are also arranged tilted and the tilting direction is opposite to that of the impeller blades.

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

6. The axial flow water jet pump according to claim 1, characterized in that: The transmission shaft is rotationally sealedly connected to the pipeline.

7. The axial flow water jet pump according to claim 1, characterized in that: It also includes a first straightening cap, which is fixedly connected to one end of the guide vane facing the water outlet and is coaxially arranged with the guide vane.

8. The axial flow water jet 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 transmission shaft passes through the connecting pipe and is sealed and rotatably connected to the connecting pipe, and one end of the connecting pipe close to the impeller forms a second straightening cap.

9. The axial flow water jet pump according to claim 1, characterized in that: The sawtooth structure is located on a side of the impeller blade facing the water outlet, and a line connecting a tooth root and a tooth tip of the sawtooth structure is a straight line.

10. The axial flow water jet pump according to claim 1, characterized in that: The sawtooth structure is located on the side of the impeller blade facing the water inlet, and the line connecting the tooth root and the tooth tip of the sawtooth structure is an arc line.

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