Pump body inlet structure and axial impeller pump

Abstract

The application provides a pump body inlet structure and an axial impeller pump. The pump body inlet structure comprises an axial sleeve, a plurality of guide ribs are arranged on the outer side wall of the axial sleeve and are spaced along the circumference of the axial sleeve, the guide ribs extend along the axial direction of the axial sleeve and comprise a straight line segment and an arc line segment, the straight line segment extends along the straight line towards the inlet end of the axial sleeve, and the arc line segment spirally extends along the arc line to the outlet end of the axial sleeve; an inner side channel is formed in the axial sleeve, and an outer side flow channel is formed between two adjacent guide ribs. In the pump body inlet structure, under a small flow condition, the circumferential strong rotation of the fluid in the pump impeller overflows and flows into the outer side flow channel, so that the main flow and the overflow flow in the inner side channel are physically isolated, the induced rotational flow is avoided in the main flow, the circumferential velocity of the overflow flow is gradually converted into the axial velocity, the hydraulic loss is reduced, and the positive slope phenomenon of the flow-head curve under the small flow condition is eliminated.

Description

Technical Field

[0001] This invention relates to the field of vane pump technology, and in particular to a pump body inlet structure and an axial flow impeller pump. Background Technology

[0002] Axial flow impeller pumps are typical mechanical equipment for fluid transportation, characterized by large flow rate and low pressure differential. The operating efficiency and stability of axial flow impeller pumps are closely related to their internal fluid flow structure and characteristics. Under design operating conditions, the internal flow of axial flow impeller pumps is stable with low energy loss, and the system can maintain high operating efficiency. However, under low flow conditions, due to the combined effects of changes in incoming flow conditions and impeller rim clearance leakage, the transient characteristics of the internal flow of axial flow impeller pumps are significantly enhanced. Complex secondary flow structures such as flow separation, rim leakage vortices, and blade channel vortices are formed inside the rotor components. The unit enters a stall state, and energy loss increases significantly. The corresponding flow-head external characteristic curve forms a "saddle shape" with a positive slope range. The corresponding unstable operating condition region is accompanied by strong pressure pulsation and energy loss, and induces structural vibration and noise, seriously affecting the safe and stable operation of the unit.

[0003] Under low flow conditions, a forward overflow flow forms at the inlet of the impeller blades in an axial-flow impeller pump. This overflow flow reverses axially and enters the inlet pipe, forming a swirling flow with a strong circumferential velocity component on the pipe wall side. This swirling flow forms a shear flow with the mainstream flow at the center of the inlet pipe, generating induced swirling flow. Existing technologies employ various flow control measures, such as inlet pipe wall grooves, impeller chamber inner wall grooves, and double-flare suction chambers; however, none can completely eliminate the positive slope characteristic of the "saddle-shaped" external characteristic curve. Summary of the Invention

[0004] This invention provides a pump body inlet structure and an axial flow impeller pump to solve the problem of unstable operation of axial flow impeller pumps under low flow conditions, and to achieve stable operation of axial flow impeller pumps under low flow conditions.

[0005] The present invention provides a pump body inlet structure, including an axial sleeve. A plurality of guide ribs are provided on the outer wall of the axial sleeve at circumferential intervals. The guide ribs extend from the inlet end to the outlet end of the axial sleeve and include a straight segment and an arc segment. The straight segment extends axially toward the inlet end of the axial sleeve, and the arc segment extends spirally along an arc to the outlet end of the axial sleeve.

[0006] An inner cavity is formed inside the axial sleeve, and an outer flow channel is formed between two adjacent guide ribs.

[0007] According to the pump body inlet structure provided by the present invention, the pump body inlet structure further includes an installation sleeve, which is fixedly sleeved on multiple guide ribs, and the inner sidewall of the installation sleeve and the outer flow channel together form an outer cavity.

[0008] According to the pump body inlet structure provided by the present invention, the pump body inlet structure further includes an axial flow impeller pump, and the outlet end of the mounting sleeve is provided corresponding to the inlet of the axial flow impeller pump.

[0009] According to the pump body inlet structure provided by the present invention, the outer diameter D3 of the axial sleeve satisfies the following relationship:

[0010] D3 = D2 - (0.02 ~ 0.04)D1;

[0011] Where D1 is the diameter of the impeller hub of the axial flow impeller pump, and D2 is the diameter of the outer edge of the impeller blade of the axial flow impeller pump.

[0012] According to the pump body inlet structure provided by the present invention, the angle β between the extension of the arc segment towards the outlet end and the circumferential direction of the axial sleeve satisfies the following relationship:

[0013] β=t(Q d ·n) / (U tb ·H d );

[0014] Among them, Q d U is the design flow rate of the axial flow impeller pump. tb H is the circumferential velocity of the impeller rim of an axial flow impeller pump. d t represents the design head of the axial flow impeller pump, n represents the rotational speed of the axial flow impeller pump, and t represents the preset parameter.

[0015] According to the pump body inlet structure provided by the present invention, the number X of the guide ribs satisfies the following relationship:

[0016] X = 4X y +2;

[0017] Among them, X y This refers to the number of impeller blades in an axial flow impeller pump.

[0018] According to the pump body inlet structure provided by the present invention, the axial extension length L1, the circumferential extension length L2, and the arc length S of the arc segment satisfy the following relationship:

[0019] L1 = (0.7 ~ 0.9)D2;

[0020] L2={(2~3)π·D2} / X y ;

[0021] S = (1.1 ~ 1.3)D²;

[0022] Where D2 is the outer diameter of the blade of the axial flow impeller pump, and X y This refers to the number of impeller blades in an axial flow impeller pump.

[0023] According to the pump body inlet structure provided by the present invention, the axial distance L3 from the end of the arc segment near the outlet end to the inlet edge of the blade of the axial flow impeller pump satisfies the following relationship:

[0024] L3 = (0.2 ~ 0.4)D1;

[0025] Where D1 is the diameter of the impeller hub of the axial flow impeller pump.

[0026] According to the pump body inlet structure provided by the present invention, the liquid outflow direction of the outer cavity is the first swirl direction;

[0027] The first rotation direction is set opposite to the impeller rotation direction of the axial flow impeller pump.

[0028] According to the pump body inlet structure provided by the present invention, the length D4 of the mounting sleeve satisfies the following relationship:

[0029] D4 = (1.8 ~ 2.0)D2;

[0030] Where D2 is the outer diameter of the blade of the axial flow impeller pump.

[0031] The present invention also provides an axial flow impeller pump, including the pump body inlet structure of any one of the above.

[0032] In the pump inlet structure provided by this invention, guide ribs are provided on the outer wall of the axial sleeve, and an outer flow channel is formed between the guide ribs. During the process of conveying fluid to the pump body, under both design and critical operating conditions, fluid is simultaneously conveyed to the pump body through the outer flow channel and the inner cavity. At the same time, due to the arc segment on the guide rib, the fluid in the outer flow channel generates circumferential velocity, increasing the circumferential momentum of the fluid on the outside and effectively suppressing the generation of channel vortex structure. Under low flow conditions, the overflow flow generated by the fluid in the inner cavity swirls into the outer flow channel, so that the mainstream direction and overflow direction of the fluid are in different pipelines, creating physical isolation, limiting the radial range of the overflow flow and avoiding the formation of induced swirl in the mainstream. Meanwhile, the circumferential velocity in the overflow flow is gradually converted into axial velocity, reducing hydraulic loss and preventing the hydraulic performance of the axial flow impeller pump from deteriorating. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 A three-dimensional structural diagram of the pump body inlet structure provided by the present invention;

[0035] Figure 2 for Figure 1 A three-dimensional structural diagram of the pump body inlet structure, including the mounting sleeve;

[0036] Figure 3 A cross-sectional view of an embodiment of the pump body inlet structure provided by the present invention;

[0037] Figure 4 for Figure 1 Schematic diagram of the middle guide rib;

[0038] Figure 5 A flow-head comparison curve between the pump body inlet structure provided by the present invention and the existing inlet structure;

[0039] Figure 6 A flow-efficiency comparison curve between the pump body inlet structure provided by this invention and the existing inlet structure.

[0040] Figure label:

[0041] 100. Pump body inlet structure; 1. Axial sleeve; 11. Guide rib; 2. Mounting sleeve; 3. Impeller. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] Please see Figure 1The present invention provides a pump body inlet structure 100, including an axial sleeve 1. A plurality of guide ribs 11 are provided on the outer wall of the axial sleeve 1 at circumferential intervals along the axial sleeve. The guide ribs 11 extend axially along the axial sleeve 1 and include straight segments and arc segments. The straight segments extend along a straight line toward the inlet end of the axial sleeve 1, and the arc segments extend spirally along an arc to the outlet end of the axial sleeve 1. An inner cavity is formed inside the axial sleeve 1, and an outer flow channel is formed between two adjacent guide ribs 11.

[0044] In the pump body inlet structure 100 provided by the present invention, a flow guide rib 11 is provided on the outer wall of the axial sleeve 1, and an outer flow channel is formed between the flow guide ribs 11. During the process of conveying fluid to the pump body, under the design conditions and critical conditions, fluid is simultaneously conveyed to the pump body through the outer flow channel and the inner cavity. At the same time, due to the setting of the arc segment on the flow guide rib 11, the fluid in the outer flow channel generates circumferential velocity, increases the circumferential momentum of the fluid outside, and improves the pressure rise of the axial flow impeller pump. Under the condition of low flow rate, the circumferential strong swirling overflow flow generated by the fluid in the pump impeller swirls back into the outer flow channel, so that the mainstream direction and overflow direction of the fluid are in the inner cavity and the outer flow channel respectively, creating physical isolation, limiting the radial range of the overflow flow and avoiding the formation of induced swirling in the mainstream. At the same time, the circumferential velocity in the overflow flow is converted into axial velocity, reducing hydraulic loss.

[0045] For further details, please refer to Figure 2 In this embodiment, the pump inlet structure 100 further includes an installation sleeve 2, which is fixedly sleeved on multiple guide ribs 11. The inner wall of the installation sleeve 2 and the outer flow channel together form an outer cavity. In this embodiment, the installation sleeve 2 and the axial sleeve 1 together form a delivery pipe for supplying liquid to the pump body. Through the inner cavity and the outer cavity, a dual-inlet structure is formed. Under low flow conditions, the outer cavity is used to guide the backflow, reducing the impact of backflow on the inflow conditions. Furthermore, the guide ribs 11 convert the circumferential momentum of the overflow flow into static pressure, reducing hydraulic losses, avoiding a decrease in the hydraulic performance of the axial flow pump, and eliminating the positive slope phenomenon of the flow-head curve under low flow conditions.

[0046] For details, please refer to Figure 3 The pump body inlet structure 100 also includes an axial flow impeller pump, with the outlet end of the mounting sleeve 2 corresponding to the inlet of the axial flow impeller pump. In this embodiment, a complete pump body structure is formed by the mounting sleeve 2, the axial sleeve 1, and the axial flow impeller pump. Fluid is delivered into the axial flow impeller pump through the water inlet pipe composed of the mounting sleeve 2 and the axial sleeve 1. At the same time, the arc segment is set to correspond to the impeller 3 of the axial flow impeller pump to ensure that the flow state at the impeller inlet is uniform when the flow rate is greater than the critical operating condition flow rate.

[0047] In the embodiments provided by the present invention, the outer diameter D3 of the axial sleeve 1 satisfies the following relationship:

[0048] D3 = D2 - (0.02 ~ 0.04)D1

[0049] Where D1 is the diameter of the impeller hub of the axial flow impeller pump, and D2 is the diameter of the outer edge of the impeller blade of the axial flow impeller pump.

[0050] In this embodiment, the outer diameter D3 of the axial sleeve 1 directly affects the backflow guidance effect of the overflow flow under low flow conditions. The overflow flow needs to enter the outer cavity through the arc segment. The generation of the overflow flow is related to the blades in the axial flow impeller pump. Therefore, the outer diameter of the axial sleeve 1 is obtained according to the difference between the impeller hub diameter and the outer edge diameter of the blade to ensure the backflow guidance effect.

[0051] It should be noted that the inner diameter of the axial sleeve 1 is (0.8~1.0)D2, which ensures the effective elimination of the circumferential velocity of the swirling flow in the outer channel.

[0052] Meanwhile, the length of the axial sleeve 1 is (1.8~2.0)D2, ensuring the normal transport of water flow.

[0053] On the other hand, please see Figure 4 The end of the arc segment facing away from the straight segment extends along the first direction, and the angle β between the first direction and the axial direction of the sleeve circumference satisfies the following relationship:

[0054] β=t(Q d ·n) / (U tb ·H d )

[0055] Among them, Q d U is the design flow rate of the axial flow impeller pump. tb H is the circumferential velocity of the impeller rim of an axial flow impeller pump. d t represents the design head of the axial flow impeller pump, n represents the rotational speed of the axial flow impeller pump, and t represents the preset parameter.

[0056] In this embodiment, the arc segment extends from the straight segment to the outlet end of the axial sleeve 1. The direction of the arc segment near the end of the straight segment is set along the axial direction of the axial sleeve 1, the same as the straight segment, to ensure the connection with the straight segment. The direction of the arc segment away from the straight segment approaches the end face of the axial sleeve 1 and forms an angle with the circumferential direction. The angle directly affects the circumferential velocity when the fluid is output or flows back into the outer cavity. Therefore, in this embodiment, the angle is set by using the design operating condition external characteristic parameters of the axial flow impeller pump to ensure that a good circumferential flow guidance effect can be generated.

[0057] The value of t ranges from 0.4 to 0.5.

[0058] On the other hand, the number X of the flow guide ribs 11 satisfies the following relationship:

[0059] X = 4X y +2

[0060] Among them, X y This refers to the number of blades in impeller 3 of the axial flow impeller pump.

[0061] In this embodiment, the number of outer cavities directly affects the control effect of circumferential swirling flow under low flow conditions; therefore, the number of guide ribs 11 is determined according to the number of impeller blades, and multiple guide ribs 11 are evenly spaced circumferentially to ensure a stable effect during inflow or return.

[0062] Similarly, the axial extension length L1, the circumferential extension length L2, and the arc length S of the arc segment satisfy the following relationship:

[0063] L1 = (0.7 ~ 0.9)D2

[0064] L2=((2~3)π·D2) / X y

[0065] S = (1.1 ~ 1.3)D²

[0066] Where D2 is the outer diameter of the blade of the axial flow impeller pump, and X y This refers to the number of impeller blades in an axial flow impeller pump.

[0067] In this embodiment, the curvature of the arc segment is obtained through the blade parameters of blade 3 to ensure its control effect on the circumferential swirling flow, so as to adapt to different blades 3.

[0068] On the other hand, the axial distance L3 between the end of the arc segment near the outlet and the inlet edge of the blade of the axial flow impeller pump satisfies the following relationship:

[0069] L3 = (0.2 ~ 0.4)D1

[0070] Where D1 is the diameter of the impeller hub of the axial flow impeller pump.

[0071] By ensuring the axial distance between the end of the arc segment and the inlet edge of the vane pump 3, the overflow flow can be guaranteed to flow back into the outer cavity.

[0072] It should be noted that in this embodiment, the thickness of the guide rib is 3mm.

[0073] Additionally, it should be noted that in this embodiment, the length of the straight section of the guide rib is (0.9~1.1)D2.

[0074] In the embodiments provided by the present invention, the liquid outflow direction of the outer cavity is a first swirl direction; the first swirl direction is opposite to the impeller swirl direction of the axial flow impeller pump. In this embodiment, under the design operating conditions, the first swirl direction generated when the fluid flows out of the outer cavity, that is, the circumferential velocity, is opposite to the impeller swirl direction.

[0075] Based on the above-mentioned pump body inlet structure 100, the present invention also provides an axial flow impeller pump, which includes all the technical features of the above-mentioned pump body inlet structure 100, and therefore also has the technical effects brought about by all the above-mentioned technical features, which will not be described in detail here.

[0076] Based on the above-mentioned pump body inlet structure 100, the present invention provides verification data. It should be noted that the present invention uses CFX software to conduct simulation tests on the above-mentioned pump body inlet structure 100 and the inlet model of a common axial flow impeller pump.

[0077] Please see Figure 5 In particular, when the flow rate is greater than the critical operating condition, the flow rate-head curves of the original model and the model of this invention are basically the same.

[0078] The head value of the model in this invention is basically equal to that of the original model under the design conditions.

[0079] At critical operating conditions, as the flow rate decreases further from the critical operating conditions, the head of the original model decreases rapidly with the decrease in flow rate, while the head of the model of this invention gradually increases with the decrease in flow rate.

[0080] A comparison between the model of the present invention and the original model shows that the model of the present invention can eliminate the positive slope phenomenon of the flow-head curve and has no significant impact on the head under the condition that the flow rate is greater than the critical operating condition.

[0081] at the same time, Figure 6 The flow-efficiency curves show that, under stall conditions, the efficiency of the model in this invention is generally about 10 percentage points higher than that of the original model.

[0082] The efficiency comparison analysis between the model of the present invention and the original model shows that the model of the present invention significantly reduces energy loss under stall conditions, improves efficiency, and ensures increased head.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pump body inlet structure, characterized in that, The device includes an axial sleeve, on the outer wall of which are provided a plurality of guide ribs spaced circumferentially along the axial sleeve. The guide ribs extend from the inlet end to the outlet end of the axial sleeve and include a straight segment and an arc segment. The straight segment extends axially toward the inlet end of the axial sleeve, and the arc segment extends spirally along an arc to the outlet end of the axial sleeve. An inner cavity is formed inside the axial sleeve, and an outer flow channel is formed between two adjacent guide ribs; The outer flow channel is used to accommodate and guide the overflow flow returning from the pump impeller under low flow conditions, so that the mainstream of the inner cavity and the overflow flow of the outer flow channel are physically isolated; and the arc segment is used to convert the circumferential velocity of the overflow flow into the axial velocity. The pump body inlet structure also includes a mounting sleeve and an axial flow impeller pump; The mounting sleeve is fixedly sleeved on the multiple guide ribs, and the inner sidewall of the mounting sleeve and the outer flow channel together form an outer cavity. The outlet end of the mounting sleeve is set to correspond to the inlet of the axial flow impeller pump; The liquid outflow direction of the outer cavity is the first swirling direction; The first rotation direction is opposite to the impeller rotation direction of the axial flow impeller pump.

2. The pump body inlet structure according to claim 1, characterized in that, The outer diameter D3 of the axial sleeve satisfies the following relationship: D3 = D2 - (0.02 ~ 0.04)D1; Wherein, D1 is the diameter of the impeller hub of the axial flow impeller pump, and D2 is the diameter of the outer edge of the blade of the axial flow impeller pump.

3. The pump inlet structure according to claim 1, characterized in that, The angle β between the extension of the arc segment toward the outlet end and the circumferential direction of the axial sleeve satisfies the following relationship: β=t(Q d n) / (U tb H d ); Among them, Q d U is the design flow rate of the axial flow impeller pump. tb H is the circumferential velocity of the impeller rim of the axial flow impeller pump. d The design head of the axial flow impeller pump is n, the rotational speed of the axial flow impeller pump is n, and t is a preset parameter.

4. The pump inlet structure according to claim 1, characterized in that, The number of guide ribs X satisfies the following relationship: X=4X y +2; Among them, X y The number of impeller blades in the axial flow impeller pump.

5. The pump body inlet structure according to claim 1, characterized in that, The axial extension length L1, circumferential extension length L2, and arc length S of the arc segment satisfy the following relationship: L1 = (0.7 ~ 0.9)D2; L2={(2~3) π∙D2} / X y ; S = (1.1 ~ 1.3)D²; Where D2 is the outer diameter of the blade of the axial flow impeller pump, and X y The number of impeller blades in the axial flow impeller pump.

6. The pump body inlet structure according to claim 1, characterized in that, The axial distance L3 between the end of the arc segment near the outlet end and the inlet edge of the blade of the axial flow impeller pump satisfies the following relationship: L3 = (0.2 ~ 0.4)D1; Wherein, D1 is the hub diameter of the axial flow impeller pump.

7. An axial flow impeller pump, characterized in that, Includes the pump body inlet structure according to any one of claims 1 to 6.

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