A waterjet propeller impeller for optimizing cavitation performance

Abstract

The present invention relates to a waterjet propeller impeller for optimizing cavitation performance. A plurality of micro-grooves are formed on the tip of the impeller, and the grooving direction of the micro-grooves is perpendicular to the center line of the impeller tip. The most significant feature of the present invention is that the tip of the impeller is grooved, and the actual effect is to suppress the generation of cavitation. In the initial stage of the tip clearance vortex, the effect of grooving is to delay the inception cavitation number. At this time, the effect is to increase the maximum non-cavitating speed. Compared with the cavitating state, the vibration of the pump casing and the radiated noise are significantly reduced. In the fully developed stage of the cavitation bubbles, the effect of grooving is to reduce the coverage area of the cavitation bubbles on the impeller in the pump. At this time, the propeller can generate a higher power and increase the maximum speed of the ship.

Description

Technical Field

[0001] The present invention relates to a waterjet propeller in ship and ocean engineering, in particular to an impeller of a waterjet propeller. Background Art

[0002] Waterjet propulsion is a special propulsion technology that generates thrust by using the momentum difference between the ejected and inhaled water flows. It can be used in high-speed ships and amphibious vehicles. Compared with traditional propellers, it has the characteristics of low noise, high propulsion efficiency, and excellent maneuverability at high speeds. The main reasons for low noise and high efficiency are that it is less likely to generate cavitation compared with propellers. Therefore, for the design of waterjet propellers, improving the cavitation resistance ability can effectively reduce vibration, noise, and even improve the propulsion efficiency. The cavitation that occurs in the impeller of a waterjet propeller is mainly sheet cavitation and tip clearance vortex cavitation. The initial determination and scale effect of the two types of cavitation are different. Generally speaking, sheet cavitation is not affected by the scale effect, while tip vortex cavitation is affected by the scale effect. For model scale, sheet cavitation occurs earlier than tip vortex cavitation, but when converted to full scale, tip vortex cavitation occurs earlier than sheet cavitation. Therefore, tip vortex cavitation needs to be suppressed first for pump cavitation. Design parameters such as the design point, load and distribution form, pump blade profile, and local configuration of waterjet propulsion affect the tip clearance vortex cavitation performance of the pump blade. Taking a certain standard pump as an example, the relationship between its flow coefficient and the initial cavitation number of the tip clearance vortex is as Figure 1 shown. Design experience shows that the tip configuration will have an important impact on local flow, propeller efficiency, and the occurrence of tip vortex cavitation. If through reasonable design, the propeller can reduce the initial cavitation number of the tip vortex while maintaining the same efficiency, then its maximum non-cavitating speed can be significantly improved.

[0003] Through the retrieval of the prior art, it is found that Chinese Patent Publication No. CN110671360A discloses an invention that arranges strip-shaped protrusions at the leading edge of the blade to suppress cavitation on the blade back; Chinese Patent Publication No. CN106050730B discloses a technique that penetrates through the blade surface through a folding hole at the lowest pressure point on the blade back of the impeller to achieve the suppression of cavitation on the blade back; Chinese Patent Publication No. CN206478038U discloses a technique that grooves the inner wall surface of the impeller chamber to suppress cavitation in the tip clearance; Patent Publication No. WO2021 / 087640A1 published by the World Intellectual Property Organization describes a technique that suppresses tip leakage vortex and cavitation by opening holes near the tip of the impeller. The above several patents and the technology disclosed in the present invention are all for the purpose of cavitation resistance. The difference between the present invention and them lies in the means used for cavitation resistance. The present invention is to open a groove with a specific size range near the leading edge at the tip. Within the groove size range encompassed by the present invention, the effectiveness of this technology for suppressing tip cavitation has been verified through experiments. Summary of the Invention

[0004] Aiming at the problem that the tip clearance vortex cavitation of traditional impellers restricts the cavitation-free speed and the maximum speed, the present invention proposes a waterjet propeller impeller for optimizing cavitation performance. By improving the tip of the existing pump impeller, the tip clearance vortex cavitation under different flow coefficients is optimized, and the cavitation resistance of the existing inventory pumps is improved.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a waterjet propeller impeller for optimizing cavitation performance, with multiple micro-grooves opened on the tip of the impeller, and the grooving direction of the micro-grooves is perpendicular to the center line of the impeller tip.

[0006] Further, the multiple micro-grooves are arranged along the impeller tip within a range of 0.1-0.2C, where C is the chord length of the blade tip.

[0007] Further, the grooving depth of the micro-grooves is 0.08-0.12D, where D is the maximum thickness of the impeller tip.

[0008] Further, the grooving width of the micro-grooves is 0.08-0.12D.

[0009] Further, the gap between the micro-grooves is 0.4-0.6D.

[0010] Further, the grooving method of the micro-grooves is semi-circular, or the right angle of the square groove is rounded.

[0011] Further, when the impeller rotates at high speed, the pressure on the blade surface is greater than that on the blade back. The micro-grooves will generate local jets, which will cut off the tip vortex and increase the local pressure, thereby achieving the effect of suppressing the tip clearance vortex cavitation.

[0012] Further, the waterjet propeller impeller for optimizing cavitation performance is applied to high-speed surface ships with waterjet propulsion. At the designed speed, it is used to suppress the generation of tip clearance vortex cavitation, thereby significantly improving the comfort of navigation at this time and reducing the impact on the environment.

[0013] Further, the waterjet propeller impeller for optimizing cavitation performance is applied to high-speed surface ships with waterjet propulsion. In the case of the limit speed, it is used to significantly eliminate the cavitation in the pump, improve the efficiency, and break through the maximum speed at this time.

[0014] Further, the waterjet propeller impeller for optimizing cavitation performance is applied to underwater vehicles. In a low-noise environment, it is used to delay the generation of tip clearance vortex cavitation and increase the maximum cavitation-free speed.

[0015] The beneficial effects of the present invention are:

[0016] The maximum feature of the present invention is that the tip of the impeller is grooved, and the actual effect is to inhibit the generation of cavitation. In the initial stage of the tip clearance vortex, the effect of grooving is to delay the initial cavitation number. At this time, the effect is to increase the maximum non-cavitating speed. Compared with the cavitating state, the vibration of the pump casing and the radiated noise are significantly reduced. In the stage of full development of the cavitation bubbles, the effect of grooving is to reduce the coverage area of the cavitation bubbles on the impeller in the pump. At this time, the thruster can generate higher power and increase the maximum speed of the ship. Description of the Drawings

[0017] Figure 1 is the relationship between the flow coefficient and the initial cavitation number of the tip clearance vortex;

[0018] Figure 2 is the overall schematic diagram of the impeller grooving of the present invention;

[0019] Figure 3 is the partial enlarged view of the tip grooving;

[0020] Figure 4 is the schematic diagram of the grooving size;

[0021] Figure 5 is Figure 4 the view in the direction of A of

[0022] Figure 6 is the schematic diagram of the effect of the micro-groove. Detailed Embodiment

[0023] The present invention will be further described below in conjunction with the drawings and embodiments.

[0024] As Figure 2 , shown in Fig. 3, a waterjet propeller impeller for optimizing cavitation performance proposed by the present invention has a tip chord length of C, and a plurality of micro-grooves 1 are opened on the tip of the impeller blade of the impeller. The range of the micro-grooves 1 is 0.1 - 0.2C.

[0025] The maximum thickness of the impeller tip is D, wherein the grooving direction of the micro-groove 1 is perpendicular to the center line of the impeller tip, the grooving depth is 0.08 - 0.12D, the grooving width is 0.08 - 0.12D, and the gap between the micro-grooves 1 is 0.4 - 0.6D. See Figure 4 , Fig. 5.

[0026] In the embodiment, the grooving method of the micro-groove 1 can be semi-circular or the right angle of the square groove is rounded.

[0027] When the impeller rotates at high speed, the pressure on the blade surface 2 is greater than that on the blade back 3. The opened micro-groove 1 will generate a jet flow locally. The jet flow will cut off the tip vortex and increase the local pressure, thereby achieving the effect of inhibiting the cavitation of the tip clearance vortex. See Figure 6 .

[0028] Based on the present invention, the applicable scenarios are as follows:

[0029] (1) For high-speed surface ships equipped with waterjet thrusters, at the designed speed, tip clearance cavitation may have occurred inside the pump. At this time, the tip clearance cavitation will cause the vibration of the pump casing and the increase of radiated noise, which will have an adverse impact on the crew on board and the surrounding marine life. Aiming at the adverse effects of tip clearance cavitation on vibration and noise, the application of this technology can suppress the generation of tip clearance cavitation, thereby significantly improving the comfort of navigation at this time and reducing the environmental impact.

[0030] (2) For high-speed surface ships equipped with waterjet thrusters, in the case of the maximum speed, cavitation inside the pump is already relatively serious, and the impeller surface and the tip clearance have been covered by cavitation bubbles. Cavitation has an adverse effect on efficiency. At this time, increasing the rotational speed will result in a larger cavitation bubble coverage area, and the speed will not only not increase but may even decrease. Aiming at the adverse effects of cavitation on efficiency, the application of this technology can significantly eliminate the cavitation bubbles inside the pump, improve the efficiency, and break through the maximum speed at this time.

[0031] (3) For underwater vehicles, they need to work in a low-noise environment and reduce their own radiated noise impact. It is an important design index that the thruster does not generate cavitation bubbles during navigation. With the increase of the designed speed requirement, tip clearance cavitation will become the biggest obstacle to increasing the speed. The application of this technology can delay the generation of tip clearance cavitation and increase the maximum non-cavitating speed.

Claims

1. A waterjet propeller impeller for optimizing cavitation performance, characterized in that: Multiple micro-grooves are formed on the tip of the impeller, and the grooving direction of the micro-grooves is perpendicular to the center line of the impeller tip; the micro-grooves are located at the tip near the leading edge of the impeller and are distributed within the range of 0.1-0.2C of the chord length of the blade tip, where C is the chord length of the blade tip; the multiple micro-grooves have a range of 0.1-0.2C along the impeller tip; the grooving depth of the micro-grooves is 0.08-0.12D, where D is the maximum thickness of the impeller tip; the grooving width of the micro-grooves is 0.08-0.12D; the gap between the micro-grooves is 0.4-0.6D.

2. The waterjet propeller impeller for optimizing cavitation performance according to claim 1, characterized in that: The grooving method of the micro-grooves is semi-circular, or the right angles of the square grooves are rounded.

3. The water jet propeller impeller for optimizing cavitation performance according to claim 1, characterized in that: When the impeller rotates at high speed, the pressure on the blade surface is greater than that on the blade back. The micro-grooves will generate local jets, which will cut off the tip vortices and increase the local pressure, thereby achieving the effect of suppressing tip clearance vortex cavitation.

4. The water jet propeller impeller for optimizing cavitation performance according to claim 1, characterized in that: The impeller of the waterjet propeller for optimizing cavitation performance is applied to high-speed surface ships of waterjet propellers. At the designed speed, it is used to suppress the generation of tip clearance vortex cavitation, thereby significantly improving the comfort of navigation at this time and reducing the impact on the environment.

5. The water jet propeller impeller for optimizing cavitation performance according to claim 1, characterized in that: The impeller of the waterjet propeller for optimizing cavitation performance is applied to high-speed surface ships of waterjet propellers. In the case of the limit speed, it is used to significantly eliminate the cavitation in the pump, improve the efficiency, and break through the maximum speed at this time.

6. The water jet propeller impeller for optimizing cavitation performance according to claim 1, wherein: The impeller of the waterjet propeller for optimizing cavitation performance is applied to underwater vehicles. In a low-noise environment, it is used to delay the generation of tip clearance vortex cavitation and increase the maximum cavitation-free speed.

Images