Centrifugal pump impeller for cavitation and cavitation erosion experiments

Abstract

The invention provides a centrifugal pump impeller for cavitation and cavitation erosion experiments, a plurality of blades are arranged on the centrifugal pump impeller, and each blade is composed of three sections including a pressurization section, a cavitation erosion test section and a flow guide section from outside to inside; the pressurizing section is used for ensuring the pressurizing capacity of the blade; an inflection point exists between the working surface of the cavitation erosion test section and the working surface of the flow guide section and is used for generating a low-pressure area for cavitation erosion near the working surface of the cavitation erosion test section; and the cavitation erosion test section is detachably mounted on the impeller. And an included angle capable of generating a low-pressure area for cavitation erosion in the cavitation erosion test section is arranged between the cavitation erosion test section and the diversion section. The technical difficulties that the hydraulic machinery cavitation erosion experiment consumes long time, the material surface morphology in the cavitation erosion area is difficult to measure, and the cavitation erosion performances of different materials are difficult to directly compare can be solved.

Description

Technical Field

[0001] The present invention relates to the field of cavitation, and particularly to a centrifugal pump impeller for cavitation erosion experiments. Background Art

[0002] Cavitation refers to the process in which a liquid is transformed from a liquid phase into vapor (cavitation bubbles) under a low-pressure environment, and then further develops and finally collapses under a high-pressure environment. The collapse of cavitation bubbles is often accompanied by the generation of cavitation erosion. This is because when cavitation bubbles collapse near the wall surface, high-pressure waves and microjets with extremely strong impact forces will be generated. When they act on the material surface repeatedly, it will cause material peeling, mass loss, fatigue failure, and even fracture.

[0003] Centrifugal pumps are the most widely used pump types in liquid transportation, and cavitation is an inevitable physical phenomenon during the operation of centrifugal pumps. The cavitation erosion closely related to it often causes the deterioration of the pump's boosting performance and a significant increase in vibration and noise, thereby greatly increasing the maintenance cost and inspection frequency of centrifugal pumps. It can be said that cavitation erosion has become one of the main factors affecting the lifespan of the hydraulic components inside centrifugal pumps and the reliability of the working system. Therefore, it is urgent to carry out cavitation erosion experiments inside centrifugal pumps and urgently compare the tolerance of different materials in the cavitation environment of centrifugal pumps.

[0004] However, there are many difficulties in measuring cavitation erosion experiments inside centrifugal pumps nowadays. First, when carrying out cavitation erosion experiments, since it is necessary to cause damage to the surface of metal materials, the required experimental duration is generally very long, and a large amount of human and electrical resources are needed. Second, to obtain the cavitation erosion resistance of different materials, it is necessary to use a scanning electron microscope to scan the surface morphology of the material before and after cavitation erosion. When scanning, the material needs to be a flat surface, while the flow channels of general centrifugal pumps are twisted and do not meet the basic conditions for scanning. Third, to test the cavitation erosion performance of different materials, it is necessary to use impellers made of different materials to conduct repetitive cavitation erosion experiments, which puts extremely strict requirements on the consistency of the cavitation erosion experimental conditions, that is, the same water quality, the same environmental temperature, the same cavitation bubble length, and the same cavitation erosion test duration are required in several repeated experiments. However, the experimental equipment and system required for centrifugal pump cavitation are relatively complex, and there are many uncontrollable factors (water quality, water temperature, gas content rate) in the experiment, and it is difficult to ensure that different materials bear the same characteristic cavitation erosion load in the same cavitation environment. Therefore, the existence of the above difficulties makes it difficult to effectively carry out cavitation erosion tests on hydraulic machinery at the present stage, and it is even more difficult to obtain the cavitation erosion morphology inside centrifugal pumps. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a centrifugal pump impeller for cavitation erosion experiments, which can solve the technical difficulties of long experimental duration of hydraulic machinery cavitation erosion experiments, difficult measurement of the surface morphology of the material in the cavitation erosion area, and difficult direct comparison of the cavitation erosion performance of different materials.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A centrifugal pump impeller for cavitation erosion experiments, on which several blades are provided. The blades are composed of three sections, which are, from outside to inside, a pressurization section, a cavitation test section, and a diversion section; the pressurization section is used to ensure the pressurization ability of the blades; there is an inflection point between the working surface of the cavitation test section and the working surface of the diversion section, which is used to generate a low-pressure area for cavitation near the working surface of the cavitation test section; the cavitation test section is detachably installed on the impeller.

[0008] Furthermore, an angle is provided between the cavitation test section and the diversion section, which can generate a low-pressure area for cavitation in the cavitation test section.

[0009] Furthermore, the angle between the working surface of the cavitation test section and the working surface of the diversion section is 140° - 160°.

[0010] Furthermore, the working surface of the cavitation test section is tangent to the working surface of the pressurization section.

[0011] Furthermore, the length of the diversion section accounts for 15% - 20% of the total length of the blade; the length of the cavitation test section accounts for 20% - 25% of the total length of the blade; 55% - 65% of the length of the diversion section.

[0012] Furthermore, the cavitation test section is a flat straight blade.

[0013] Furthermore, several blades are installed between the front cover plate and the rear cover plate of the impeller. The front cover plate of the impeller is made of a transparent material and is used to photograph the cavitation degree at different positions of the cavitation test section.

[0014] Furthermore, cavitation test sections made of different materials are installed on each blade, and the cavitation test sections of the same material are symmetrically arranged.

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

[0016] 1. For the centrifugal pump impeller for cavitation erosion experiments of the present invention, a segmented impeller blade is adopted, and a low-pressure area prone to cavitation is created at the working surface of the cavitation test section through the angle between the diversion section and the cavitation test section, so that the centrifugal pump impeller is more likely to cavitate, reducing the duration required for cavitation experiments.

[0017] 2. For the centrifugal pump impeller for cavitation erosion experiments of the present invention, the cavitation test section is a straight blade, that is, a flat surface, which is convenient for obtaining the material morphology characteristics before and after cavitation by using a scanning electron microscope before and after cavitation experiments.

[0018] 3. The centrifugal pump impeller for cavitation erosion experiments according to the present invention can conduct cavitation performance tests on different materials simultaneously through the cavitation erosion test sections of blades made of different materials, avoiding errors in experimental results caused by changes in environmental parameters and working conditions during cavitation experiments, improving the accuracy of relevant experiments, and reducing the time and economic costs of experiments.

[0019] 4. The centrifugal pump impeller for cavitation erosion experiments according to the present invention has three detachable parts of the blade, which are easier to achieve precision machining of the blade surface compared to the blades of ordinary impellers, can ensure the same surface roughness of different materials, and are more conducive to observing and comparing the surface characteristics of different materials after being subjected to cavitation impact in the later stage.

[0020] 5. The centrifugal pump impeller for cavitation erosion experiments according to the present invention has blades in the cavitation section made of different materials, which are easy to disassemble and assemble, facilitating the comparison of cavitation damage of materials after cavitation experiments; its structure is simple and easy to manufacture. At the same time, the range of selectable materials is wide, and the measurement of the cavitation resistance of various materials can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. The following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained obviously without creative efforts based on these drawings.

[0022] Figure 1 It is the front view of the impeller main body in the embodiment of the present invention;

[0023] Figure 2 It is the side view of the impeller main body in the embodiment of the present invention;

[0024] Figure 3 It is the top view of the blade in the embodiment of the present invention;

[0025] Figure 4 It is the explanatory diagram of the blade length ratio and positional relationship in the embodiment of the present invention;

[0026] Figure 5 It is the relationship diagram of net positive suction head - head under the design working conditions of the impeller in the embodiment of the present invention and the prior art.

[0027] Figure 6 It is the comparison diagram of the cavitation areas of the axial middle section of the impeller in the embodiment of the present invention and the prior art under the same cavitation working conditions.

[0028] In the figure:

[0029] 1 - Boosting section; 2 - Cavitation test section; 3 - Flow guiding section; 4 - Front cover plate; 5 - Rear cover plate of impeller; 6 - Screw hole. Detailed implementation manners

[0030] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as a limitation to the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0032] In the present invention, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] As Figure 1 and Figure 2 shown, for the centrifugal pump impeller for cavitation and erosion experiments of the present invention, a plurality of blades are provided on the centrifugal pump impeller, and the plurality of blades are installed between the front cover plate 4 and the rear cover plate 5 of the impeller; as Figure 1 and Figure 3As shown, the blade is composed of three sections, which are the pressurization section 1, the cavitation test section 2, and the flow guiding section 3 from outside to inside; the pressurization section 1 is used to ensure the pressurization ability of the blade; there is an inflection point between the working surface of the cavitation test section 2 and the working surface of the flow guiding section 3, which is used to generate a low-pressure area for cavitation near the working surface of the cavitation test section 2; the cavitation test section 2 is detachably installed between the front cover plate 4 and the rear cover plate 5 of the impeller. The front cover plate 4 of the impeller is made of transparent plexiglass, so as to facilitate taking pictures of the cavitation degree at different positions of the cavitation test section 2 through a high-speed camera.

[0034] As Figure 3 and Figure 4 shown, each blade is composed of three sections. The flow guiding section 3 accounts for 15%-20% of the total length of the blade, and its main function is to guide the mainstream to move along the direction of the flow guiding section 3; the length of the cavitation test section 2 accounts for 20%-25% of the total length of the blade. As Figure 4 shown, the supplementary angle of the angle between the cavitation test section 2 and the flow guiding section 3 is α, and the angle range of α is between 20 and 40 degrees. Then, the angle between the working surface of the cavitation test section 2 and the working surface of the flow guiding section 3 is 140° to 160°, and this angle can generate a low-pressure area for cavitation. By setting this angle, a flow separation low-pressure area can be generated in the cavitation section of the blade, making cavitation more likely to occur, and the surface of the cavitation section is a flat straight surface, which is convenient for scanning the material morphology with an electron scanning microscope before and after cavitation; the length of the pressurization section 1 accounts for 55%-65% of the total length of the blade, and the working surface of the cavitation test section 2 is tangent to the working surface of the pressurization section 1, which is convenient for the blade to pressurize the mainstream, so that the experimental impeller will not significantly reduce the pressurization performance on the premise of being prone to cavitation.

[0035] The cavitation test section 2 is a flat straight blade, which is convenient for cavitation morphology scanning.

[0036] In the embodiment, there are 6 impeller blades in total, and the 6 cavitation sections of the 6 blades can be made of 3 materials according to needs. The cavitation sections of the impeller made of the same material are symmetrically arranged to balance the radial force generated during impeller rotation. It can be a 4-blade impeller made of 2 materials, or an 8-blade impeller made of 4 materials.

[0037] As Figure 5 shown, by comparing the net positive suction head - head under the design conditions of the impeller of the embodiment and the prior art, it can be seen that the impeller of the present invention is more prone to cavitation; as Figure 6 shown, by comparing the cavitation areas of the axial middle section of the impeller of the embodiment of the present invention and the prior art impeller under the same cavitation working conditions, it can be seen from this figure that the coverage range of the area where the cavitation bubbles are located in the impeller of the present invention is wider, and the cavitation bubbles mainly collapse in the cavitation test section. Therefore, it is easier to obtain the cavitation morphologies of different materials in the test section.

[0038] When the centrifugal pump impeller for cavitation erosion experiment according to the present invention is in a working state, the mainstream enters from the impeller inlet. After the mainstream flows through the diversion section 3, it enters the cavitation test section 2. Due to the angle between the diversion section 3 and the cavitation test section 2, a low-pressure area is formed near the cavitation test section. As a result, the cavitation nuclei carried in the water flow expand under the action of low pressure to form cavities, and the cavities collapse in the cavitation test section 2, generating a cavitation effect. Finally, the mainstream increases the head in the pressurization area and is output from the outlet. Due to the circumferentially symmetric structural characteristics of the impeller, the above cavitation effect is approximately uniformly distributed in the circumferential direction. Therefore, the material specimens of the cavitation test section on the blades bear cavitation loads with nearly the same spatio-temporal characteristics and strength characteristics, thus ensuring the testing of the cavitation resistance of different materials under the same hydraulic cavitation conditions.

[0039] It should be understood that although this specification is described according to various embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0040] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A centrifugal pump impeller for cavitation erosion experiments, wherein a plurality of blades are provided on the centrifugal pump impeller, and it is characterized in that, The blade is composed of three sections, which are the pressurization section (1), the cavitation test section (2), and the flow guiding section (3) from outside to inside; the pressurization section (1) is used to ensure the pressurization ability of the blade; there is an inflection point between the working surface of the cavitation test section (2) and the working surface of the flow guiding section (3), which is used to generate a low-pressure area for cavitation near the working surface of the cavitation test section (2); the cavitation test section (2) is detachably installed on the impeller.

2. The centrifugal pump impeller for cavitation erosion experiment according to claim 1, characterized in that, An angle is provided between the cavitation test section (2) and the flow guiding section (3) to generate a low-pressure area for cavitation in the cavitation test section (2).

3. The centrifugal pump impeller for cavitation erosion experiment according to claim 2, characterized in that, The angle between the working surface of the cavitation test section (2) and the working surface of the flow guiding section (3) is 140° - 160°.

4. The centrifugal pump impeller for cavitation erosion experiment according to claim 2, characterized in that, The working surface of the cavitation test section (2) is tangent to the working surface of the pressurization section (1).

5. The centrifugal pump impeller for cavitation erosion experiment according to claim 1, characterized in that The length of the flow guiding section (3) accounts for 15% - 20% of the total length of the blade; the length of the cavitation test section (2) accounts for 20% - 25% of the total length of the blade; 55% - 65% of the length of the flow guiding section (3).

6. The centrifugal pump impeller for cavitation erosion experiment according to claim 1, characterized in that, The cavitation test section (2) is a flat straight blade.

7. The centrifugal pump impeller for cavitation erosion experiment according to claim 1, characterized in that, A number of blades are installed between the front cover plate (4) and the rear cover plate (5) of the impeller. The front cover plate (4) of the impeller is made of a transparent material and is used to photograph the cavitation degree at different positions of the cavitation test section (2).

8. The centrifugal pump impeller for cavitation erosion experiment according to claim 1, characterized in that Cavitation test sections (2) made of different materials are installed on each blade, and the cavitation test sections (2) of the same material are symmetrically arranged.

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