Impeller type centrifugal pump

Abstract

The impeller type centrifugal pump suitable for the low-specific-speed working condition comprises a volute and an impeller, the impeller comprises a rotating shaft, a first impeller cover plate, a second impeller cover plate and a plurality of blades, and the first impeller cover plate, the blades and the second impeller cover plate are sequentially and tightly arranged in the axial direction of the rotating shaft. The impeller is arranged in the volute; the volute is provided with a fluid inlet and a fluid outlet; in the axial direction, the distance between the opposite vertical faces of the radial edges of the first impeller cover plate and the second impeller cover plate is smaller than the width of the fluid outlet. And the distance between the opposite vertical surfaces of the radial edges is greater than the width of the fluid outlet. The axial width of the fluid outlet of the centrifugal pump is discussed separately from a general centrifugal pump design theory, so that the design accuracy of the low-specific-speed centrifugal pump is improved, the number of design iterations can be reduced, and the development cost is reduced.

Description

Technical Field

[0001] This application relates to the technical field of centrifugal pumps, and particularly to an impeller centrifugal pump suitable for low specific speed conditions. Background Art

[0002] As one of the most important hydraulic performances of a pump, high efficiency has always been an important indicator for the hydraulic design of a pump. As shown in the following table, it shows the hydraulic efficiency performance curves of various impeller shapes in different types of pumps under different specific speed conditions. Different types of pumps have different design difficulties and uncertainties. Especially for centrifugal pumps with low specific speeds, there are generally problems such as low efficiency and the high-efficiency point of the pump characteristic curve shifting to the right in the curve chart. Especially within the scope of the European market, the European Union has a minimum requirement for the Minimum Efficiency Index (MEI) of centrifugal pumps. How to improve the efficiency of low specific speed centrifugal pumps has always been a difficult problem in the industry's hydraulic design.

[0003]

[0004] In the prior art, the mainstream hydraulic design of centrifugal pumps adopts the following design: the width b3 of the volute inlet is equal to the width b2 of the impeller outlet including the thicknesses of the front and rear covers tot , and satisfies the following formula:

[0005] b3 = b2 tot +(5 - 10) (1) or

[0006] b3 = (1.6 - 2)*b2 tot (2)

[0007] Among them, the measurement units of the width of the volute inlet and the width of the impeller outlet including the thicknesses of the front and rear covers are both mm. However, after verification, the centrifugal pumps designed using the above formula (1) or (2) are quite applicable and have considerable efficiency under medium or even high specific speed conditions; however, for centrifugal pumps designed in this way under low specific speed conditions, there are often large deviations between the theoretical design and the actual test results, and multiple rounds of iterative design are required to meet the requirements. Among them, the specific speed n s is a parameter characterizing the comprehensive performance of the water pump:

[0008]

[0009] Among them, Q represents the flow rate of the water pump, and the measurement unit is m 3 / h; n represents the rotational speed of the water pump, and the measurement unit is r / min; and H represents the head of the water pump, and the measurement unit is m.

[0010] It is conceivable that the operating cost required to overcome the right shift of the efficient point of the pump characteristic curve in the flow rate - efficiency curve chart through multiple rounds of iterative design is necessarily higher than that of a single - impeller design. Therefore, it is necessary to provide a design of a centrifugal pump with an impeller that can still meet the required MEI requirements in the case of a single impeller. Summary of the Invention

[0011] To overcome at least one of the above - mentioned defects of the prior art, the object of the present application is to provide a centrifugal pump with an impeller, including a volute and an impeller. The impeller includes a rotating shaft, a first impeller cover plate, a second impeller cover plate, and a plurality of blades. In the axial direction of the rotating shaft, the first impeller cover plate, the plurality of blades, and the second impeller cover plate are sequentially and closely arranged, and the impeller is placed inside the volute. The volute has a fluid inlet and a fluid outlet. And, the first impeller cover plate and the second impeller cover plate have radial edges in the radial direction of the impeller, and in the axial direction, the distance between the facing vertical surfaces of the radial edges of the first impeller cover plate and the second impeller cover plate is less than the width of the fluid outlet; and, the distance between the back - facing vertical surfaces of the radial edges of the first impeller cover plate and the second impeller cover plate is greater than the width of the fluid outlet.

[0012] In one embodiment, there is a gap between the radial edge and the inner surface of the volute.

[0013] In another embodiment, the back - facing vertical surfaces of the first impeller cover plate and the second impeller cover plate respectively face the corresponding inner surfaces of the volute, thereby defining low - pressure cavities on both sides of the impeller.

[0014] In yet another embodiment, the fluid outlet has a pair of outlet vertical surfaces orthogonal to the axial direction, and the pair of outlet vertical surfaces respectively correspond to the thickness centers of the first impeller cover plate or the second impeller cover plate in the radial direction.

[0015] In yet another embodiment, the gap between the first impeller cover plate or the second impeller cover plate and the inner surface of the volute serves as a fluid passage from the impeller to the low - pressure cavity, and the fluid flowing through the fluid passage flows perpendicular to the main flow direction from the impeller to the fluid outlet.

[0016] In yet another embodiment, the first impeller cover plate and the second impeller cover plate have a plurality of through - holes so that the fluid in the low - pressure cavity is sucked by the negative pressure generated by the impeller between the first impeller cover plate and the second impeller cover plate.

[0017] In some embodiments, the specific speed of the centrifugal pump with an impeller is in the range of 10 to 80.

[0018] In yet another embodiment, the specific speed of the centrifugal pump with impeller is 50.3.

[0019] In yet another embodiment, the rated flow rate is 17 m 3 / h, the rated head is 14 m, and the rated speed is 1450 r / min.

[0020] This application separately discusses the axial width of the fluid outlet of the low-specific-speed centrifugal pump, separated from the general centrifugal pump design theory, improving the accuracy of designing low-specific-speed centrifugal pumps, reducing the number of design iterations, and lowering the development cost. On the other hand, the centrifugal pump with impeller designed according to this application effectively increases the efficiency of the low-specific-speed centrifugal pump, improves the MEI of the water pump, and conforms to the energy conservation and emission reduction policy. Further, according to the design of this application, the highest efficiency point of the centrifugal pump shifts towards the small flow rate direction, improving the trend that the high-efficiency point of the low-specific-speed pump generally shifts towards the large flow rate point under conventional designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following-described drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 Shows an axial sectional view of the centrifugal pump with impeller according to an embodiment of this application;

[0023] Figure 2 Shows Figure 1 An axial semi-sectional view of the centrifugal pump with impeller of the illustrated embodiment;

[0024] Figure 3 Shows a simplified axial sectional view of the impeller and fluid outlet of the prior art; and

[0025] Figure 4 Shows the hydraulic efficiency curve diagrams of centrifugal pumps with different designs.

[0026] LIST OF REFERENCE NUMERALS:

[0027] 1 - Centrifugal pump with impeller; 2 - Volute; 3 - Impeller; 101 - First vertical surface of the fluid outlet; 102 - Second vertical surface of the fluid outlet; 103 - Fluid outlet; 104 - Fluid inlet; 201 - First impeller cover plate; 202 - Second impeller cover plate; 203 - First low-pressure cavity; 204 - Second low-pressure cavity; 205 - Blade; 206 - Rotating shaft; b2 - Hydraulic outlet width of the impeller; b3 - Width of the fluid outlet; b2 tot - Impeller outlet width including the cover plate thickness. Detailed implementation manners

[0028] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are only a part rather than all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0029] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "X-axis", "Y-axis", "Z-axis", "vertical", "parallel", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application 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 application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "plural" is two or more.

[0030] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected" and "coupled" 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 application can be understood according to specific circumstances.

[0031] As Figure 1-2 shown, it shows the axial sectional view and half sectional view of a volute centrifugal pump according to an embodiment of the present application. The volute centrifugal pump 1 of the present application is applicable to the working conditions with a low specific speed n s , especially in the range of 10 - 80. For example, the volute centrifugal pump 1 has a flow rate Q of 17 m 3 / h, a head H of 14 m, and a rated speed n of 1450 r / min. Calculated by formula (3), its specific speed n s is 50.3.

[0032] The volute centrifugal pump 1 includes a volute 2 and an impeller 3. The volute 2 has a fluid inlet 104 and a fluid outlet 103. The impeller 3 includes a rotating shaft 206, a first impeller cover plate 201, a second impeller cover plate 202 and a plurality of blades 205. Generally, the impeller 3 is placed inside the volute 2, and the impeller 3 rotates around the rotating shaft 206 to form a negative pressure, sucking the fluid from the fluid inlet 104 of the volute 2 into the cavity defined by the centrifugal pump 1 and forcing the fluid to flow towards the fluid outlet 103.

[0033] In this embodiment, in the axial direction of the rotating shaft 206, the first impeller cover plate 201, the plurality of blades 205 and the second impeller cover plate 202 are closely arranged in sequence. In other words, the plurality of blades 205 are sandwiched between the first impeller cover plate 201 and the second impeller cover plate 202.

[0034] It can be understood that in the axial direction of the rotating shaft 206, both the first impeller cover plate 201 and the second impeller cover plate 202 have a certain thickness. Preferably, the first impeller cover plate 201 and the second impeller cover plate 202 have the same thickness. In this direction, the distance between the opposite vertical surfaces of the first impeller cover plate 201 and the second impeller cover plate 202 is defined as the impeller hydraulic outlet width b2, with the measurement unit of mm; the width b3 of the fluid outlet 103 of the volute 2, with the measurement unit of mm; the distance between the back vertical surfaces of the first impeller cover plate 201 and the second impeller cover plate 202 is defined as the impeller outlet width b2 including the cover plate thickness tot , with the measurement unit of mm. The volute centrifugal pump 1 needs to be designed such that b2 < B3 < b2 tot .

[0035] In the existing design, as Figure 3 shown, b3 > b2 tot > b2. Specifically, according to the existing mainstream hydraulic design theory, when designing the volute hydraulic width b3, b3 is usually greater than b2 including the thickness of the front and rear impeller cover plates tot , specifically b3 = b2 tot +(5 - 10) or b3 = (1.6 - 2)b2 tot . Through the applicant's research, it is found that this empirical formula is more applicable to medium-specific-speed and high-specific-speed centrifugal pumps and has higher efficiency. However, it has a weak effect on low-specific-speed centrifugal pumps.

[0036] For low-specific-speed centrifugal pumps, as Figure 4 shown, the volute centrifugal pump 1 designed with b2 < b3 < b 2tot has an obvious improvement in hydraulic efficiency. Compared with the designs of other relative size relationships of the above three widths, such as b2 = b3 < b2 tot and b2 < b2 tot<b3, and there is a sign that its highest energy efficiency point shifts to the right.

[0037] Among them, the range of low specific speed is 10 - 80.

[0038] In the radial direction of the rotating shaft 206, there are gaps between the radial edges of the first impeller cover plate 201 and the second impeller cover plate 202 and the inner surface of the volute 2. Moreover, the back-facing vertical surfaces of the first impeller cover plate 201 and the second impeller cover plate 202 face the corresponding inner surfaces of the volute 2 respectively, thus defining the low-pressure chambers on both sides of the impeller 3, namely the first low-pressure chamber 203 and the second low-pressure chamber 204. It can be expected that most of the fluid flowing out from the impeller hydraulic outlet width b2 flows to the fluid outlet 103, while the remaining part flows into the first low-pressure chamber 203 and the second low-pressure chamber 204 through this gap. This gap serves as the fluid passage from the impeller 3 to the first / second low-pressure chambers 203 / 204, and its length direction is perpendicular to the main flow direction from the impeller 3, especially from the impeller hydraulic outlet width b2 to the fluid outlet 103. The advantage of such a structure is that the fluid is not easy to flow smoothly into this gap, thereby reducing the flow rate of the fluid flowing into the first low-pressure chamber 203 and the second low-pressure chamber 204, reducing the disc friction loss, and ultimately improving the hydraulic efficiency of the centrifugal pump 1.

[0039] In a preferred embodiment, the fluid outlet 103 has a pair of outlet vertical surfaces orthogonal to the axial direction, namely the first fluid outlet vertical surface 101 and the second fluid outlet vertical surface 102, which respectively correspond to the thickness centers of the first impeller cover plate 201 and the second impeller cover plate 202 in the radial direction.

[0040] In a preferred embodiment, the first impeller cover plate 201 and the second impeller cover plate 202 can be designed to have a number of through holes (not shown). Thus, the fluid staying in the first low-pressure chamber 203 and the second low-pressure chamber 204 is sucked by negative pressure between the first impeller cover plate 201 and the second impeller cover plate 202 for subsequent transportation by the impeller 3 to the fluid outlet 103.

[0041] It should be understood that the above-mentioned drawings and the specific embodiments described are only exemplary embodiments of the present application, rather than an exhaustion of all possible embodiments of the present application. Those skilled in the art can make various modifications to the above specific embodiments within the protection scope of the present application without departing from the main idea of the present application.

Claims

1. A volute centrifugal pump, comprising a volute and an impeller, wherein the impeller includes a rotating shaft, a first impeller cover plate, a second impeller cover plate and a plurality of blades. In the axial direction of the rotating shaft, the first impeller cover plate, the plurality of blades and the second impeller cover plate are sequentially arranged closely, and the impeller is placed in the volute; the volute has a fluid inlet and a fluid outlet; Characterized in that, the first impeller cover plate and the second impeller cover plate have radial edges in the radial direction of the impeller. In the axial direction, the distance between the facing vertical surfaces of the radial edges of the first impeller cover plate and the second impeller cover plate is less than the width of the fluid outlet; and the distance between the back-facing vertical surfaces of the radial edges of the first impeller cover plate and the second impeller cover plate is greater than the width of the fluid outlet.

2. The centrifugal impeller pump according to claim 1, characterized in that, There is a gap between the radial edge and the inner surface of the volute.

3. The centrifugal impeller pump according to claim 2, wherein The back-facing vertical surfaces of the first impeller cover plate and the second impeller cover plate face the corresponding inner surfaces of the volute, thereby defining low-pressure chambers on both sides of the impeller.

4. The centrifugal impeller pump according to claim 3, characterized in that, The fluid outlet has a pair of outlet vertical surfaces orthogonal to the axial direction, and the pair of outlet vertical surfaces respectively correspond to the thickness centers of the first impeller cover plate or the second impeller cover plate in the radial direction.

5. The volute centrifugal pump according to claim 3, characterized in that, The gap between the first impeller cover plate or the second impeller cover plate and the inner surface of the volute serves as a fluid passage from the impeller to the low-pressure chamber, and the fluid flowing through the fluid passage flows perpendicular to the main flow direction from the impeller to the fluid outlet.

6. The volute centrifugal pump according to claim 3, characterized in that, The first impeller cover plate and the second impeller cover plate have a plurality of through holes so that the fluid in the low-pressure chamber is sucked by the negative pressure generated by the impeller between the first impeller cover plate and the second impeller cover plate.

7. The centrifugal impeller pump according to any one of claims 1-6, characterized in that, The specific speed of the volute centrifugal pump is in the range of 10 to 80.

8. The centrifugal impeller pump according to claim 7, characterized in that, The specific speed of the volute centrifugal pump is 50.

3.

9. The volute centrifugal pump according to claim 8, characterized in that, The rated flow rate is 17 m 3 / h, the rated head is 14 m, and the rated speed is 1450 r / min.

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