T-shaped groove tip vortex structure, pump-jet propeller comprising same and design method of pump-jet propeller

Abstract

The invention belongs to the technical field of vortex eliminating structures, and particularly relates to a T-shaped groove tip vortex structure, a pump-jet propeller comprising the T-shaped groove tip vortex structure and a design method of the T-shaped groove tip vortex structure. The T-shaped groove tip vortex structure is composed of an annular groove 1b and rectangular grooves 1a which are evenly formed in the front side of the annular groove 1b in an annular array mode. The bottoms of the rectangular groove 1a and the annular groove 1b are flush, the front and rear side wall surfaces are perpendicular to the rotor shaft, and the left and right side wall surfaces are perpendicular to the bottom surface. The grooves are formed in the inner wall of the guide pipe, so that the tip clearance of the rotor is increased, the radial gradient of the speed is reduced, the radial free vortex becomes dispersed, the speed of discharge flow and the pressure difference between the tip pressure surface and the suction surface are reduced, the strength of tip clearance separation vortex and discharge flow are weakened, fusion of the separation vortex and the discharge flow is weakened, and the strength of the tip vortex is reduced; damage and dissipation effects of the inner wall of the groove on vortexes and discharge flow are achieved; the annular structure at the tail end of the groove prolongs the action interval of the groove on the tip discharge vortex, and finally a good cavitation inhibition effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vortex elimination structures, and particularly relates to a T-shaped groove tip vortex structure, a pump-jet propeller containing the structure, and a design method thereof. Background Art

[0002] The noise generated by cavitation is one of the main reasons why the propeller becomes one of the three major noise sources of an underwater vehicle. The collapse of cavitation bubbles will cause a series of harms to the underwater propeller. Once cavitation occurs in the pump-jet propeller, the radiation noise of the pump-jet propeller increases sharply, which has a serious impact on the stealth of the submarine. Due to the existence of tip-end separation vortices and tip leakage vortices in the conventional pump-jet propeller, tip clearance cavitation and tip vortex cavitation are very likely to occur. To avoid cavitation in the propeller, the cavitation inception speed of the pump-jet propeller is relatively low, which limits the improvement of the quiet speed of the submarine. Cavitation generally occurs first at the tip-end of the pump-jet propeller, followed by rotor tip vortex cavitation, and finally cavitation on the back of the rotor blade. The separation vortices and tip leakage vortices in the rotor tip clearance have very obvious unsteady motion characteristics. This unsteady vortex system will induce pressure pulsations on the surface of the duct. Since the pressure in the vicinity of the vortex system is extremely low and the tip vortex system is adjacent to the inner wall of the duct, there are also obvious low-pressure areas on the inner wall of the duct near the rotor tip and near the tip leakage vortex. During the rotation of the rotor, the spatial positions of the tip-end separation vortices and tip leakage vortices change with the rotation of the rotor. The change in the position of the vortex system will also induce large-amplitude periodic pulsations of the pressure on the surface of the duct. The flow of the tip vortex system of the rotor not only increases the flow noise, but also the pressure pulsations induced on the surface of the duct by it will cause structural vibrations of the duct of the pump-jet propeller, thereby increasing the noise, which is an important noise source of the underwater vehicle.

[0003] The means to address the tip vortex cavitation problem can be divided into two types: active and passive, according to the action mode. Among them, the passive method can be further divided into modifying the blade structure and the wall surface above the tip.

[0004] The operation of the active control method for tip leakage vortices is generally relatively complex, and an additional operating system needs to be introduced to complete the relevant work, and the duration is limited. Underwater vehicles generally have a long operation time and have high requirements for the buoyancy balance, load requirements, and structural layout of the vehicle body. Therefore, this type of method is difficult to meet the actual engineering requirements.

[0005] Based on the passive modification scheme, Patent CN113158376 A provides a vortex elimination structure of rectangular grooves on the inner wall of a pump-jet propeller duct and its design and processing methods. It creatively uses rectangular grooves to weaken the tip vortex cavitation of the rotor. The groove structure on the inner wall of the duct can transfer part of the low-pressure area to the inside of the grooves, weaken the low-pressure extreme value in the tip leakage vortex channel, and the low pressure in the flow field no longer concentrates on the tip leakage vortex center, reducing the tip leakage vortex cavitation. However, at the same time, in the main area where the rectangular groove duct suppresses the tip vortex cavitation, that is, near the end face of the groove, the huge pressure difference causes the fluid in the rotor domain to enter the inside of the groove. Since the shape of the groove edge changes greatly and there are corners in multiple directions, there are large high-pressure areas near the groove edges of the axial and transverse boundaries of the groove. Correspondingly, the velocity direction also changes around the high-pressure extreme point. The high-pressure points on the axial boundary form a large circumferential velocity, and the high-pressure area on the transverse boundary forms a large axial velocity with a negative direction, which is prone to the superposition of the axial velocity and the circumferential velocity at the groove angle, resulting in too strong a separation flow inside the groove near the trailing edge of the rotor, a large separation vortex intensity inside the groove, and the pressure at the vortex core center and the pressure on the inner wall of the duct being much lower than the saturated vapor pressure. Summary of the Invention

[0006] The object of the present invention is to provide a T-shaped groove tip vortex structure that can enhance the effect of rectangular grooves in suppressing tip leakage vortex cavitation and weaken the separation vortex at the groove edge, a pump-jet propeller duct containing this structure, and its design method based on the actual needs and on the basis of the rectangular groove vortex elimination structure.

[0007] To achieve the above object, the present invention adopts the following technical solutions.

[0008] A T-shaped groove tip vortex structure is composed of an annular groove 1b and rectangular grooves 1a uniformly arranged in an annular array on the front side of the annular groove body 1b.

[0009] For a further improvement or preferred embodiment of the aforementioned T-shaped groove tip vortex structure, the radial depth H of the T-shaped groove g is 1 / 7 to 1 / 2 of the thickness of the duct at the position of the groove; the axial length L of the rectangular groove g is 3 / 200 to 1 / 40 of the inner wall circumference of the duct at the position of the groove; the circumferential length B of the rectangular groove g is g 1 / 10 to 3 / 10 of the axial length L; the number N of the rectangular grooves is 40 to 160; the angle θ between the axis of the rectangular groove and the axis of the rotor is 0 to 0.5°; the circumferential length L of the annular groove r is g 1 / 20 to 1 / 5 of the axial length L of the rectangular groove.

[0010] For a further improvement or preferred embodiment of the foregoing T-shaped groove tip vortex structure, the bottom of the rectangular groove 1a is flush with the bottom of the annular groove 1b, the front and rear side walls are perpendicular to the rotor shaft, and the left and right side walls are perpendicular to the bottom surface.

[0011] The present application also provides a pump-jet propeller including the T-shaped groove tip vortex structure described in claim 1, wherein a T-shaped groove tip vortex structure is provided on the inner wall of the pump-jet propeller duct; the front end of the rectangular groove 1a is opposite to the farthest end of the leading edge of the rotor tip, and the rear end of the annular groove 1b is opposite to the farthest end of the trailing edge of the rotor tip.

[0012] The present application also provides a design method for the duct of a pump-jet propeller with a T-shaped groove tip vortex structure, which is characterized by including the following steps:

[0013] Step 1: Determine the initial design parameters of the groove on the inner wall of the duct; specifically, according to the working parameters of the pump-jet propeller and the geometric shapes of the duct and the rotor, determine the initial parameters of the T-shaped groove on the inner wall of the duct.

[0014] Step 2: Respectively change the axial length Lg and the number N of the rectangular grooves, determine the influence laws of the axial length and the number of the grooves on the lowest pressure value of the rotor tip end face and the core pressure of the rotor tip vortex, and select the axial length Lg and the number N of the rectangular grooves that make the pressure of the rotor tip end face the lowest and the increment of the core pressure of the rotor tip vortex the largest as the optimization results.

[0015] Step 3: Taking the optimization results of Step 2 as the initial state, respectively change the circumferential length Bg of the rectangular groove, determine the influence laws of the circumferential length Bg of the rectangular groove on the lowest pressure value of the rotor tip end face and the core pressure of the rotor tip vortex, and select the circumferential length Bg of the rectangular groove that makes the pressure of the rotor tip end face the lowest and the increment of the core pressure of the rotor tip vortex the largest as the optimization results.

[0016] Step 4: Taking the optimization results of Step 3 as the initial state, change the radial depth Hg of the rectangular groove, obtain the influence laws of the radial depth Hg of the rectangular groove on the lowest pressure value of the rotor tip end face and the core pressure of the rotor tip vortex, adjust the groove depth, and select the radial depth Hg of the rectangular groove that makes the pressure of the tip end face the lowest and the increment of the core pressure of the rotor tip vortex remain unchanged as the optimization results.

[0017] Step 5: Taking the optimization results of Step 4 as the initial state, change the circumferential length Lr of the annular groove, obtain the influence laws of the circumferential length Lr of the annular groove on the lowest pressure value of the rotor tip end face and the core pressure of the rotor tip vortex, adjust the groove depth, and select the circumferential length Lr of the annular groove that makes the pressure of the tip end face the lowest and the increment of the core pressure of the rotor tip vortex remain unchanged as the optimization results.

[0018] Step 6: Taking the optimization result of Step 5 as the initial state, change the angle θ between the axis of the rectangular groove and the axis of the rotor, determine the influence laws of the angle θ on the lowest pressure of the rotor tip end face and the pressure of the rotor tip vortex core, and select the corresponding angle θ when the pressure of the tip end face is the lowest and the pressure increment of the rotor tip vortex core is the largest as the optimization result;

[0019] Step 7: Based on the optimization result of Step 6, successively change the shapes of the edges of the T-shaped groove into guide circle structures with different radii Rrc, determine the influence laws of the guide circle radius of the T-shaped groove edge on the lowest pressure of the rotor tip end face and the pressure of the rotor tip vortex core, and select the corresponding guide circle radius of the T-shaped groove edge when the pressure of the tip end face is the lowest and the pressure increment of the rotor tip vortex core is the largest as the optimization result.

[0020] For a further improvement or preferred implementation step of the design method of the pump-jet propeller duct with the aforementioned T-shaped groove tip vortex structure, it is characterized in that the initial parameters include: the initial radial depth Hg of the rectangular groove, which is set to 1 / 4 of the thickness of the duct at the position where the T-shaped groove is located; the initial axial length Lg of the rectangular groove, which is set to 1 / 240 of the inner wall circumference of the duct at the position where the T-shaped groove is located; the initial circumferential length Bg of the rectangular groove, which is set to 1 / 5 of the axial length Lg of the rectangular groove; the initial number N of the rectangular grooves, which is set to 120; and the angle θ between the axis of the rectangular groove and the axis of the rotor, which is set to 0°.

[0021] Its beneficial effects are as follows:

[0022] In the pump-jet propeller with a certain number of T-shaped grooves opened on the inner wall of the duct of the present invention, due to the grooves opened on the inner wall of the duct, the clearance at the rotor tip is increased, the radial gradient of the velocity is reduced, the radial free vortex becomes dispersed, and at the same time, the velocity of the leakage flow and the pressure difference between the pressure surface and the suction surface at the tip are reduced, so that the intensity of the tip clearance separation vortex and the leakage flow are weakened, and the fusion of the separation vortex and the leakage flow is weakened, and the tip vortex intensity is reduced; the destruction and dissipation effects of the inner wall of the groove on the vortex and the leakage flow; and the annular structure at the end of the groove extends the action range of the groove on the tip leakage vortex, can increase the pressure of the wake vortex core, and is also beneficial to delaying the time when the rotor tip separation vortex and the blade shear vortex merge with the tip leakage vortex, increasing the time for each of the three to dissipate independently, and further increasing the low-pressure amplitude of the wake vortex core pressure. It effectively increases the vortex core pressure and reduces the tip vortex cavitation volume, and the reduction of the lowest pressure on the inner wall of the duct is less, and finally achieves a better cavitation suppression effect. At the same time, the T-shaped groove vortex elimination structure of the present application can reduce the pressure pulsation on the inner wall of the duct and reduce the vibration noise of the pump-jet propeller duct structure. Description of the Drawings

[0023] Figure 1 is the geometric model of a certain pre-stator pump-jet propeller

[0024] Figure 2 is a schematic diagram of the cavitation simulation result of the original duct;

[0025] Figure 3 is a schematic diagram of the T-shaped groove structure form;

[0026] Figure 4 is a schematic diagram of the distribution position of the T-shaped groove structure;

[0027] Figure 5 is a schematic diagram of the cavitation simulation result of the T-shaped groove conduit

[0028] Figure 6 is a schematic diagram of the axial section distribution;

[0029] Figure 7 is a schematic diagram of the pressure comparison on the inner wall of the conduit and the vortex structure inside the groove;

[0030] Figure 8 is a schematic diagram of the pressure on the inner wall of the conduit and the cavitation inside the groove at the trailing edge of the rotor;

[0031] Figure 9 is a schematic diagram of the isosurface of the gas volume fraction α = 0.1 of different conduit structures;

[0032] Figure 10 is a schematic diagram of the position of the T-shaped groove structure. Specific embodiments

[0033] The following detailed description is given to the present invention in combination with specific embodiments, and the protection scope of the present invention cannot be limited thereby.

[0034] As Figure 1 shown, taking a certain type of pre-stator pump-jet propeller as an example, through CFD simulation software simulation, adding an S-S cavitation model, calculating the cavitation flow field of the pump-jet propeller under the condition of a rotor speed of 1100 rpm, the saturated vapor pressure is 3.2 KPa, and the tip vortex cavitation is displayed through the isosurface of the gas volume fraction α = 0.1, as Figure 2 shown.

[0035] On the basis of the above, for the pump-jet propeller with a T-shaped groove opened on the inner wall of the conduit based on the design scheme of the present invention, as Figure 3 shown, the design scheme implemented on the pre-stator pump-jet propeller is: the axial length L of the T-shaped groove g = 28.9 mm, the circumferential length B of the rectangular groove g = 5.9 mm, the radial depth H of the T-shaped groove g = 8.8 mm, the number of rectangular grooves is 100, the circumferential span of the rectangular grooves is about 2.7° and the angular intervals along the circumferential direction are equal, the fillet radius R at each edge of the T-shaped groove rc = 0.5 mm, the circumferential length L of the annular groove r is about 3.7 mm, and its distribution and position are asFigure 4 , Figure 10 as shown

[0036] Through CFD simulation software, the S-S cavitation model is added to calculate the cavitation flow field of the T-groove pump jet propeller under the condition of a rotor speed of 1100 rpm. The saturated vapor pressure is 3.2 KPa. The tip vortex cavitation is shown by the isosurface of the gas volume fraction α = 0.1, as Figure 5 shown

[0037] Combined with the original design, the rectangular groove design scheme and the T-groove design scheme of this application, a comparative analysis is carried out.

[0038] To quantify the specific reduction of tip vortex cavitation, calculate the volume of the region where the gas volume fraction α ≥ 0.1, calculate and monitor the cavitation volume in the rotor tip region and the groove region respectively, and make a comparison. The obtained cavitation volume is shown in Table 1 as follows:

[0039] Table 1 Cavitation volume data

[0040]

[0041] To analyze the adverse effect of the separation vortex at the groove edge on the minimum pressure of the duct inner wall, after the calculation is stable, monitor the minimum pressure on the two duct walls respectively, and the comparison is shown in Table 2 as follows:

[0042] Table 2 Minimum pressure data of the duct inner wall

[0043] Original catheter Rectangular groove catheter T-shaped groove catheter Pressure (KPa) 62.151 -7.265 32.426

[0044] From Table 2 and the comparison of the observed cavitation volume, it can be seen that under the condition of a rotational speed of 1100 rpm, the T-groove duct can reduce the tip leakage vortex cavitation by 83.07% compared with the original duct, and can reduce the tip leakage vortex cavitation by 40.15% compared with the rectangular groove duct, and has a more excellent inhibitory effect on the rotor tip vortex cavitation; in the groove region, although the inner wall of the rectangular groove duct has a smaller minimum pressure, it is negative, which causes bubbles to form on the inner wall of the duct, and the effect is rather poor. The T-groove does not show cavitation. After analysis, the T-groove vortex elimination structure can reduce the minimum pressure on the inner wall of the duct, thereby reducing the pressure pulsation on the inner wall of the duct, reducing the vibration and noise of the pump jet propeller, and further improving the overall stability and stealth performance.

[0045] The hydrodynamic calculations of the original structure design, the rectangular groove and the T-groove vortex elimination structure are shown in Table 3 as follows.

[0046] Table 3 Hydrodynamic calculation results of the pump jet propeller

[0047]

[0048]

[0049] where T m is the thruster thrust, T rm is the rotor thrust, Q rm is the rotor torque, T dm is the duct thrust, T sm is the stator thrust. All monitored values do not include the forces and moments on the hub.

[0050] According to Table 3, the calculation results are converted into dimensionless coefficients. The propulsion coefficients under two flow fields are shown in Table 4, and the calculation formula is as follows:

[0051]

[0052] where, V m = 1.926 m / s, n = 18.33 rps, D m = 0.246 m.

[0053] Table 4 Propulsion coefficient data of the pump-jet thruster

[0054]

[0055]

[0056] The thrust and torque on the rotor selected as the research object when establishing the rotor tip region were monitored separately, and the average value of the calculation results is compared as shown in Table 5.

[0057] Table 5 Calculation results of the thrust and torque of a single-blade rotor

[0058] Original catheter Rectangular groove catheter T-shaped groove catheter Thrust of fully wet flow field 107.523 108.189 104.976 Torque of fully wet flow field 5.564 5.599 5.442 Thrust of cavitation flow field 108.293 107.453 105.333 Torque of cavitation flow field 5.609 5.562 5.466

[0059] Although the rectangular groove has a good effect on weakening the rotor tip vortex cavitation, the groove structure on the inner wall of the duct can transfer part of the low-pressure area to the inside of the groove, weaken the low-pressure extreme value in the tip leakage vortex channel, and the low pressure in the flow field is no longer concentrated at the tip leakage vortex center, thus reducing the tip leakage vortex cavitation. However, at the same time, in the main area where the rectangular groove duct suppresses the tip vortex cavitation, that is, near the end face of the groove, the huge pressure difference causes the fluid in the rotor domain to enter the inside of the groove. Since the shape of the groove edge changes greatly and there are corners in multiple directions. For further analysis, a series of axial sections are established for the rotor domain, such as Figure 6 , according to Figure 2From the pressure distribution on the inner wall of the duct, it can be seen that there are large high-pressure areas at the edges of the groove near the axial boundary and the lateral boundary of the groove. Correspondingly, the velocity direction will also change around the high-pressure extreme point. The high-pressure point on the axial boundary forms a large circumferential velocity, and the high-pressure area on the lateral boundary forms a large axial velocity with a negative direction. The superposition effect of the axial velocity and the circumferential velocity is easy to occur at the groove angle, resulting in excessive separation flow inside the groove near the trailing edge of the rotor, and the separation vortex formed inside the groove is relatively strong. The pressure at the center of the vortex core and the pressure on the inner wall of the duct are much lower than the saturated steam pressure.

[0060] The minimum wall pressure on the rectangular grooved conduit is much lower than that on the original conduit. Figure 7 As shown, the pressure on the inner wall of the rectangular groove duct is generally higher than that of the original duct, and the low-pressure area formed by the trailing vortex is mainly concentrated on the groove boundary at the trailing edge of the rotor.

[0061] During the calculation process, it was found that near the edge of the groove at the trailing edge of the rotor, a low-pressure area with a pressure of P = 3.2 KPa appeared in the fully wetted flow field, and cavitation bubbles with a gas volume fraction of α = 0.1 also appeared in the cavitation flow field. Here, only the cavitation inside the groove at a certain moment is shown. Figure 8 The main cause of cavitation here is that the separation flow at the edge of the groove is too strong, and an overly strong separation vortex is formed at the edge of the groove, which causes a significant reduction in the minimum pressure on the inner wall of the duct. The average value at the lowest pressure is far lower than the saturated steam pressure, and finally a small amount of cavitation appears near the inner wall of the groove in the cavitation flow field.

[0062] The T-groove vortex elimination structure of the present application mainly changes the vortex elimination effect on the inner wall of the duct from the following two angles: first, to enhance the favorable aspect of the rectangular groove in suppressing tip vortex cavitation, that is, to increase the length range of the groove's effect on tip vortex cavitation, and further enhance the effect of the groove end face above the rotor trailing edge to weaken the tip vortex cavitation; second, to optimize the groove edge and weaken the separation vortex at the groove edge.

[0063] The SS cavitation model is added to calculate the cavitation flow field under the condition of n = 1100rpm speed. The saturated steam pressure is 3.2KPa. The tip vortex cavitation is displayed by the isosurface of the gas volume fraction α = 0.1 and compared with Figure 9 The results in comparison are as follows.

[0064] Through the comparison of cavitation volume, it can be seen that under the speed condition of 1100rpm, the T-groove duct can reduce the tip vortex cavitation by 83.07% compared with the original duct, and can reduce the tip vortex cavitation by 40.15% compared with the rectangular groove duct, and the effect of suppressing the rotor tip vortex cavitation is more superior; in the groove domain, there are only trace cavitations in the rectangular groove, and no cavitation occurs in the T-groove.

[0065] From the comparison of the calculation results in the two flow fields of Table 4 and Table 5, it can be seen that the tip vortex cavitation has little effect on the hydrodynamic performance of the pump-jet propeller. The difference between the thrust and torque is less than 0.3%. Combining Table 6, the influence of tip vortex cavitation on the thrust and torque of the single-blade rotor is also less than 1%. When using the original duct, the maximum change in the thrust of the single-blade rotor is 0.72%. When using the grooved duct, the changes in both thrust and torque are less than 0.1%. Tip vortex cavitation mainly occurs in the latter half of the rotor chord length and the rotor wake, generally at a certain distance from the rotor wall and the inner wall of the duct. There is no conversion between the gas phase and the liquid phase on the surface of the pump-jet propeller. Therefore, the tip vortex cavitation has little impact on the time-averaged hydrodynamic performance.

[0066] From the comparison of the time-averaged hydrodynamic performance results of the pump-jet propeller with three types of ducts in Table 4 and Table 5, it can be seen that the change of the duct has little effect on the total thrust of the pump-jet propeller. There are certain differences in the thrust and torque of the propeller when using the three duct models, but generally the differences are not large. From the comparison of the thrust on the rotor and the duct, when using the rectangular grooved duct, the rotor thrust increases slightly, but the duct thrust decreases, and the propeller thrust decreases by 1.2%. When using the T-shaped grooved duct, the rotor thrust decreases, and the duct thrust increases to be close to that of the original duct, and the total thrust decreases by 1.6%. From the comparison of the efficiency, the differences in the rotor propulsion efficiency are all within 1%. When using the rectangular grooved duct, the total propulsion efficiency decreases by 1.35%. When using the T-shaped grooved duct, the propulsion efficiency increases by 0.27%. On the basis of significantly reducing the tip leakage vortex cavitation, the T-shaped grooved duct has little effect on the time-averaged hydrodynamic performance of the pump-jet propeller, and the propulsion efficiency of the propeller is slightly higher than that of the original duct and much higher than that of the rectangular grooved duct.

[0067] From the comparative analysis, it can be seen that the T-shaped grooved duct can further significantly increase the vortex core pressure on the basis of the rectangular grooved duct, especially the vortex core pressure in the wake is further increased. Through the analysis of the cavitation flow field calculation results, it is proved that at the operating condition of 1100 rpm, when using the T-shaped grooved duct, the reduction of the tip vortex cavitation volume for the original duct and the rectangular grooved duct is 83.07% and 40.15% respectively, and the cavitation suppression effect is better. The cavitation on the duct wall disappears, and the low-pressure amplitude on the inner wall of the duct increases, effectively alleviating the adverse effect of pressure pulsation on the duct structure and improving the overall stealth performance of the pump-jet propeller.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A T-shaped groove tip vortex structure is provided on the inner wall of the propeller duct, characterized in that, It is composed of an annular groove (1b) and rectangular grooves (1a) uniformly arranged in an annular array on the front side of the annular groove body (1b).

2. The T-shaped groove tip vortex structure according to claim 1, wherein The radial depth H of the T-shaped groove g is 1 / 7 to 1 / 2 of the thickness of the conduit at the location of the groove; the axial length L of the rectangular groove g is 3 / 200 to 1 / 40 of the inner wall circumference of the conduit at the location of the groove; the circumferential length B of the rectangular groove g is 1 / 10 to 3 / 10 of the axial length L g ; the number N of the rectangular grooves is 40 to 160; the angle θ between the axis of the rectangular groove and the axis of the rotor is 0 to 0.5°; the axial width L of the annular groove r is 1 / 20 to 1 / 5 of the axial length L of the rectangular groove g .

3. The T-shaped groove tip vortex structure according to claim 1, characterized in that, The bottom of the rectangular groove (1a) is flush with the bottom of the annular groove (1b), the front and rear side walls are perpendicular to the rotor shaft, and the left and right side walls are perpendicular to the bottom surface.

4. A pump-jet propulsor comprising the T-shaped groove tip vortex structure according to claim 1, characterized in that, A T-shaped groove tip vortex structure is provided on the inner wall of the pump-jet propeller duct; the front end of the rectangular groove (1a) is opposite to the farthest end of the leading edge of the rotor tip, and the rear end of the annular groove (1b) is opposite to the farthest end of the trailing edge of the rotor tip.

5. A design method for a pump-jet propeller with a T-groove tip vortex structure, characterized in that: It includes the following steps: Step 1: Determine the initial design parameters of the grooves on the inner wall of the duct; specifically: according to the working parameters of the pump-jet propeller and the geometric shapes of the duct and the rotor, determine the initial parameters of the T-shaped grooves on the inner wall of the duct. Step 2: Change the axial length L of the rectangular groove respectively g and the quantity N, and determine the influence law of the axial length and quantity of the groove on the lowest pressure value of the rotor tip end face: the pressure of the rotor tip vortex core. Select the axial length L g and the quantity N of the rectangular groove as the optimization result Step 3: Taking the optimization result of Step 2 as the initial state, change the circumferential length B of the rectangular groove respectively g , and determine the circumferential length B of the rectangular groove g and the lowest pressure value at the end face of the rotor tip: the influence law of the pressure of the rotor tip vortex core, and select the circumferential length B of the rectangular groove that makes the pressure at the end face of the rotor tip the lowest and the pressure increment of the rotor tip vortex core the largest g as the optimization result; Step 4: Taking the optimization result of Step 3 as the initial state, change the radial depth H of the rectangular groove g , and obtain the radial depth H of the rectangular groove g and the influence law of the minimum pressure value on the end face of the rotor tip: the pressure of the rotor tip vortex core. Adjust the groove depth, and select the radial depth H of the rectangular groove when the pressure on the end face of the tip is the lowest and the pressure increment of the rotor tip vortex core remains unchanged g as the optimization result; Step 5: Using the optimized result of Step 4 as the initial state, change the axial width L of the annular groove r , and obtain the axial width L of the annular groove r and the lowest pressure value at the end face of the rotor tip: the influence law of the pressure at the core of the rotor tip vortex, adjust the groove depth, and select the axial width L of the annular groove when the pressure at the end face of the tip is the lowest and the pressure increment at the core of the rotor tip vortex remains unchanged r as the optimized result; Step 6: Taking the optimization result of Step 5 as the initial state, change the angle θ between the axis of the rectangular groove and the axis of the rotor, and determine the influence law of the angle θ on the lowest pressure of the rotor tip end face: the pressure of the rotor tip vortex core; select the angle θ corresponding to the lowest pressure of the tip end face and the largest increment of the rotor tip vortex core pressure as the optimization result. Step 7: Based on the optimization result of Step 6, change the shapes at the edges of each T-shaped groove to a radius R in sequence rc For different fillet structures, determine the influence law of the fillet radius at the edge of the T-shaped groove on the lowest pressure at the end face of the rotor tip: the pressure of the rotor tip vortex core. Select the fillet radius at the edge of the T-shaped groove corresponding to the lowest pressure at the end face of the tip and the largest increase in the pressure of the rotor tip vortex core as the optimization result.

6. The design method of the pump-jet propeller for the T-shaped groove tip vortex structure according to claim 5, characterized in that, The initial parameters include: the radial depth H of the initial rectangular groove g , which is set to 1 / 4 of the thickness of the conduit at the position of the T-shaped groove; the axial length L of the initial rectangular groove g , which is set to 1 / 240 of the inner wall circumference of the conduit at the position of the T-shaped groove; the circumferential length B of the initial rectangular groove g , which is set to 1 / 5 of the axial length L of the rectangular groove g ; the initial number N of rectangular grooves, which is set to 120; the angle θ between the axis of the rectangular groove and the axis of the rotor, which is set to 0°.

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