Centrifugal pump semi-open type impeller with annular cover plate and design method of centrifugal pump semi-open type impeller

Abstract

The invention relates to the field of centrifugal pumps, in particular to a centrifugal pump semi-open type impeller with annular cover plates and a design method thereof.The centrifugal pump semi-open type impeller comprises an impeller body, the impeller body is provided with a rear cover plate, a plurality of blades which are evenly arranged at intervals in the circumferential direction are arranged on the front side of the rear cover plate, and an inter-blade cover plate is fixedly installed between every two adjacent blades; the inter-blade cover plate is in an arc shape which is coaxial with the impeller; by means of the annular cover plate composed of the multiple inter-blade cover plates, the function of a front cover plate can be partially replaced, backflow of liquid in channels between the blades is effectively restrained, and therefore the volume loss is reduced, and the lift and efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of centrifugal pumps, and more specifically to a semi-open impeller for a centrifugal pump with an annular cover plate and its design method. Background Technology

[0002] A semi-open impeller in a centrifugal pump is an impeller type that removes the front cover plate. Due to its structural characteristics, the semi-open impeller has advantages such as strong anti-clogging properties, low manufacturing cost, and ease of maintenance and cleaning. However, it also has significant disadvantages, mainly lower efficiency, lower head, and the tendency for backflow of liquid between the blades, resulting in substantial volumetric losses.

[0003] In order to overcome the inefficiency of semi-open impellers while retaining their advantages, especially for low-flow-rate retrofitting of existing pumps without changing the original pump casing, an innovative impeller structure and corresponding optimization design method are needed. Summary of the Invention

[0004] The purpose of this invention is to provide a semi-open impeller for a centrifugal pump with an annular cover plate and its design method. The annular cover plate, composed of multiple inter-impeller cover plates, is used to improve the pump's head and efficiency under low flow conditions, thereby solving the defects mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A centrifugal pump semi-open impeller with an annular cover plate includes an impeller, the impeller is provided with a rear cover plate, the front side of the rear cover plate is provided with a plurality of blades evenly spaced in the circumferential direction, and an inter-blade cover plate is fixedly installed between two adjacent blades, the inter-blade cover plate being arc-shaped and coaxial with the impeller.

[0006] As a further improvement, the blade includes long blades and short blades arranged at intervals, and the outer ends of the long blades and the short blades are flush with the edge of the rear cover plate.

[0007] As a further improvement, the impeller has a diameter of D, the inlet diameter of the short blade is D0, the inner diameter of the inter-blade cover is D1, the outer diameter is D2, and D0≤D1<D2≤D.

[0008] As a further improvement, the inter-blade cover is fixedly installed between the leading edges of two adjacent blades.

[0009] As a further improvement, the inter-blade cover plate is arranged parallel to the rear cover plate; the thickness of the inter-blade cover plate is consistent at all positions.

[0010] As a further improvement, the inner edge of the leaf cover is rounded.

[0011] A design method for a semi-open impeller of a centrifugal pump with an annular cover plate includes the following steps: S1: Determine the key design parameters of the inter-blade cover, including: the thickness T of the inter-blade cover and its inner diameter D1 and outer diameter D2; S2: Based on the original impeller design, under rated speed and rated flow conditions, performance data of impeller head H and efficiency η under multiple sets of different (D1, D2, T) parameter combinations are obtained through computational fluid dynamics (CFD) simulation. S3: Fit the performance data obtained in step S2 to establish a quantitative relationship model between the impeller performance parameters and the blade cover plate structural parameters; S4: Determine the target head H_target and target efficiency η_target based on the target operating point requirements; S5: Substitute H_target and η_target into the quantitative relationship model established in step S3, and solve or optimize to obtain one or more sets of (D2, T) parameter values ​​that meet the performance requirements, which are used as the final design dimensions of the leaf cover plate.

[0012] As a further improvement, in step S3, the quantification relationship model is a linear regression model, specifically in the following form: Head H = H0 - H1 × D1 – H2 × D2 - H T ×T; Efficiency η = η0-η1 × D1 + η2 × D2 + η T ×T; Among them, H 0、 H1, H2, H T η0, η1, η2, η T These are the regression coefficients obtained by fitting CFD data.

[0013] As a further improvement, the regression coefficients are obtained by least squares fitting, and the goodness-of-fit R is used as the setpoint. 2 Evaluate the reliability of the model, where R 2 =1-(SSE / SST), where SSE is the sum of squares of the residuals and SST is the total sum of squares.

[0014] Compared with the prior art, the beneficial effects of the present invention are: An annular cover plate composed of multiple blade cover plates can partially replace the function of the front cover plate, effectively suppressing backflow of liquid in the inter-blade channel, thereby reducing volumetric loss and improving head and efficiency. Without altering the original pump casing, existing pumps can be modified for low-flow operation by installing inter-blade cover plates, meeting specific user requirements and demonstrating high application value. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural schematic diagram of an embodiment of the present invention; Figure 2 yes Figure 1 Schematic diagram of the AA section; Figure 3 yes Figure 1 A three-dimensional schematic diagram.

[0017] In the diagram: 1-Impeller; 2-Rear cover plate; 3-Long blade; 4-Short blade; 5-Inter-blade cover plate. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figures 1 to 3 As shown, a semi-open impeller of a centrifugal pump with an annular cover plate includes an impeller 1. The impeller 1 is provided with a rear cover plate 2. The front side of the rear cover plate 2 is welded or integrally formed with a plurality of blades evenly spaced in the circumferential direction. The blades include long blades 3 and short blades 4 spaced apart. The outer ends of the long blades 3 and the short blades 4 are flush with the edge of the rear cover plate 2. The inlet diameter of the long blades 3 is smaller than the inlet diameter of the short blades 4.

[0020] An inter-blade cover plate 5 is fixedly installed between adjacent long blades 3 and short blades 4. The inter-blade cover plate 5 is welded between the leading edges of adjacent long blades 3 and short blades 4, and the inter-blade cover plate 5 is arranged parallel to the rear cover plate 2. The thickness of the inter-blade cover plate 5 is consistent along the axial direction of the impeller 1 at all positions.

[0021] The blade cover 5 is an arc shape coaxial with the impeller 1. Multiple blade cover plates 5 are located on the same ring, and the multiple blade cover plates 5 together form an annular cover plate. The annular cover plate composed of multiple blade cover plates can partially replace the function of the front cover plate, effectively suppress the backflow of liquid in the channel between blades, thereby reducing volume loss and improving head and efficiency.

[0022] The main design parameters of the blade cover plate 5 include the inner diameter D1, the outer diameter D2, and the thickness T. The diameter of the impeller is D, and the inlet diameter of the short blade 4 is D0. The following conditions must be met: D0≤D1<D2≤D, to ensure sufficient flow passage and take into account the impeller's passability. The thickness T of the blade cover plate 5 is uniform at all positions. The thickness T of the blade cover plate 5 is close to or equal to the thickness of the blade of the impeller 1, and can be thickened as needed to adjust the performance.

[0023] The inner edge of the leaf cover 5 is rounded, and the radius R of the rounded corner is preferably 0.5T to reduce flow resistance.

[0024] A design method for a semi-open impeller of a centrifugal pump with an annular cover plate includes the following steps: S1: Determine the key design parameters of the inter-blade cover plate 5, including: the thickness T, inner diameter D1, and outer diameter D2 of the inter-blade cover plate 5; S2: Based on the original impeller design, under rated speed and rated flow conditions, performance data of impeller head H and efficiency η under multiple sets of different (D1, D2, T) parameter combinations are obtained through computational fluid dynamics (CFD) simulation. S3: Fit the performance data obtained in step S2 to establish a quantitative relationship model between the impeller performance parameters and the structural parameters of the blade cover plate 5. S4: Determine the target head H_target and target efficiency η_target based on the target operating point requirements; S5: Substitute H_target and η_target into the quantitative relationship model established in step S3, and solve or optimize to obtain one or more sets of (D2, T) parameter values ​​that meet the performance requirements, which are used as the final design dimensions of the leaf cover 5.

[0025] In step S3, the quantitative relationship model is a linear regression model, with the following specific form: Head H = H0 - H1 × D1 – H2 × D2 - H T ×T; Efficiency η = η0-η1 × D1 + η2 × D2 + η T ×T; Among them, H 0、 H1, H2, H T η0, η1, η2, η T These are the regression coefficients obtained by fitting CFD data.

[0026] The regression coefficients were obtained by fitting using the least squares method, and the goodness of fit R was used as the metric. 2 Evaluate the reliability of the model, where R 2 =1-(SSE / SST), where SSE is the sum of squares of the residuals and SST is the total sum of squares.

[0027] Example: Taking the JHXL20-40 pump as an example (D=295mm, H=30mm, D0=185mm, blade thickness 7mm), with a speed of 1450RPM, the original design was for a head of 30 meters at a flow rate Qc of 50 cubic meters. Based on the customer's operating point requirements, the rated flow rate was changed to 20 cubic meters. The CFD results at this flow rate are as follows: <![CDATA[Inner diameter D1 (mm) of the blade cover plate]]> <![CDATA[Outer diameter D2 (mm) of the interblade cover plate]]> Inter-blade cover thickness T (mm) Head H (m) Efficiency η% 120 200 8 50.77 24.61 120 200 10 50.32 24.82 120 200 12 49.93 24.91 120 220 8 49.53 25.01 120 220 10 49.57 25.12 120 220 12 49.05 25.40 120 240 8 47.55 25.50 120 240 10 47.34 25.90 120 240 12 47.36 26.15 120 260 8 46.94 25.82 120 260 10 46.35 26.33 120 260 12 46.25 26.54 140 200 8 50.69 24.60 140 200 10 50.45 24.68 140 200 12 50.29 24.78 140 220 8 49.08 25.07 140 220 10 48.62 25.29 140 220 12 48.25 25.37 140 240 8 47.23 25.76 140 240 10 47.13 25.95 140 240 12 47.09 26.08 140 260 8 47.27 25.76 140 260 10 46.15 26.28 140 260 12 45.99 26.59 160 200 8 50.63 24.53 160 200 10 50.45 24.62 160 200 12 50.23 24.64 160 220 8 49.52 25.00 160 220 10 49.06 25.01 160 220 12 49.09 25.05 160 240 8 48.58 25.25 160 240 10 47.99 25.67 160 240 12 47.43 25.79 160 260 8 47.53 25.61 160 260 10 46.96 25.95 160 260 12 46.52 26.39 The following relationship was obtained through CFD data processing: Head H = 62.62 - 0.005 × D1 – 0.05 × D2 – 0.2 × T, goodness of fit (R²) 2 The value is 0.95; Efficiency η = 20.37 - 0.002 × D1 + 0.02 × D2 + 0.075 × T, goodness of fit (R²) 2 The value is 0.90.

[0028] Among them, R 2 =1-(SSE / SST) SSE (Sum of Squared Errors); SST (Total Sum of Squares).

[0029] The model shows that increasing the outer diameter D2 of the blade cover 5 will improve efficiency, but will slightly reduce the head; decreasing the inner diameter D1 of the blade cover 5 has a positive effect on both head and efficiency; increasing the thickness T of the blade cover 5 will improve efficiency, but will reduce the head.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A centrifugal pump semi-open impeller with a ring-shaped cover plate, characterized in that: The impeller (1) is provided with a rear cover plate (2), the front side of the rear cover plate (2) is provided with a plurality of blades uniformly and evenly arranged in a circle, and an inter-blade cover plate (5) is fixedly installed between adjacent two blades, and the inter-blade cover plate (5) is arranged in an arc shape coaxial with the impeller (1).

2. A semi-open impeller for a centrifugal pump having a ring cover as defined in claim 1, characterized in that: The blades include long blades (3) and short blades (4) arranged at intervals, and the outer ends of the long blades (3) and the outer ends of the short blades (4) are flush with the edges of the rear cover plate (2).

3. A semi-open impeller for a centrifugal pump having a ring cover as defined in claim 2, characterized in that: The diameter of the impeller (1) is D, the inlet diameter of the short blade (4) is D0, the inner diameter of the inter-blade cover plate (5) is D1, and the outer diameter is D2, and D0≤D1<D2≤D.

4. A semi-open impeller for a centrifugal pump having a ring cover as defined in claim 1, characterized in that: The inter-blade cover plate (5) is fixedly installed between the leading edges of adjacent two blades.

5. A semi-open impeller for a centrifugal pump having a ring cover as defined in claim 1, characterized in that: The inter-blade cover plate (5) is arranged in parallel with the rear cover plate (2); the thickness of the inter-blade cover plate (5) at each position is consistent.

6. A semi-open impeller for a centrifugal pump having a ring cover as defined in claim 1, characterized in that: The inner side edge of the inter-blade cover plate (5) is chamfered.

7. A method of designing a semi-open impeller for a centrifugal pump with a ring cover as claimed in any one of claims 1-6, characterized in that, The method comprises the following steps: S1: determining the key design parameters of the inter-blade cover plate (5), including the thickness T, the inner diameter D1 and the outer diameter D2 of the inter-blade cover plate (5); S2: based on the original design of the impeller, under the rated speed and rated flow condition, through computational fluid dynamics (CFD) simulation, a plurality of groups of performance data of impeller head H and efficiency η under different (D1, D2, T) parameter combinations are obtained; S3: fitting the performance data obtained in step S2 to establish a quantitative relationship model between the performance parameters of the impeller and the structure parameters of the inter-blade cover plate (5); S4: determining the target head H_target and the target efficiency η_target according to the target working condition point requirement; S5: substituting H_target and η_target into the quantitative relationship model established in step S3 to solve or optimize a group or more groups of (D2, T) parameter values meeting the performance requirements as the final design size of the inter-blade cover plate (5).

8. The method of designing a semi-open impeller for a centrifugal pump with a ring cover as claimed in claim 7, characterized in that: In step S3, the quantitative relationship model is a linear regression model, and the specific form is as follows: Lift H = H0- H1x D1- H2x D2- H T x T; Efficiency η = η0- η1x D1+ η2x D2+ η T x T; where H 0、 H1, H2, H T η0, η1, η2, η T are regression coefficients obtained by fitting the CFD data.

9. The method of designing a semi-open impeller for a centrifugal pump with a ring cover as claimed in claim 8, characterized in that: The regression coefficients are fitted by least squares and the goodness of fit is given by the R 2 The reliability of the model is assessed where R 2 =1-(SSE / SST), SSE is the sum of squares of residuals and SST is the total sum of squares.

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