A double-suction impeller structure for a multistage centrifugal pump and its design method

Abstract

The present invention discloses a double-suction impeller structure for a multistage centrifugal pump, which includes a first blade, a first cover plate, a first outlet, a first wearing ring, a first impeller flow passage, a second blade, a second cover plate, a second outlet, a second wearing ring, a second impeller flow passage, and a hub. The axial two ends of the first outlet are flush with the axial two ends of the second outlet respectively and have the same axial width. In the circumferential direction, the first outlet and the second outlet are arranged alternately / spaced apart. It is characterized in that: the first wearing ring (13) has a first wearing ring outer edge (131) and a first wearing ring inner edge (132), the first wearing ring outer edge is circular, the first wearing ring inner edge is a first ellipse, the second wearing ring (23) has a second wearing ring outer edge and a second wearing ring inner edge (232), the second wearing ring outer edge is circular, the second wearing ring inner edge is a second ellipse, and the major axis of the first ellipse is perpendicular to the major axis of the second ellipse. The present invention can effectively improve the cavitation resistance performance of the centrifugal pump.

Description

Technical Field

[0001] The present invention relates to the technical field of multistage centrifugal pumps, and particularly to a double-suction impeller structure for a multistage centrifugal pump and a design method thereof. Background Art

[0002] As Figure 1 shown, the prior art JP2018-105298A discloses an efficient double-suction impeller structure. The outlet end of the first impeller passage has a first outlet, and the outlet end of the second impeller passage has a second outlet. The axial two ends of the first outlet are flush with the axial two ends of the second outlet respectively and have the same axial width. In the circumferential direction, the first outlet and the second outlet are arranged alternately / spaced apart, which can reduce the axial dimension of the double-suction impeller. However, while reducing the axial dimension of the double-suction impeller, the corresponding cavitation resistance performance of the existing double-suction impeller structure is reduced. Summary of the Invention

[0003] The object of the present invention is to overcome the deficiencies existing in the prior art, and provide a double-suction impeller structure for a multistage centrifugal pump and a design method thereof. Through the design of the inner edge of the stuffing box and the concave-convex part, the cavitation resistance performance of the centrifugal pump can be effectively improved. Through this design method, the cavitation resistance performance of the centrifugal pump can be improved, thereby improving the overall efficiency of the centrifugal pump.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A double-suction impeller structure for a multistage centrifugal pump, which includes a first blade (10), a first cover plate (11), a first outlet (12), a first wearing ring (13), a first impeller flow passage (P1), a second blade (20), a second cover plate (21), a second outlet (22), a second wearing ring (23), a second impeller flow passage (P2), and a hub (30). The hub includes a symmetrically arranged first hub portion (31) and a second hub portion (32). The first blade and the second blade are symmetrically arranged. The first impeller flow passage (P1) is formed between two adjacent first blades, and the second impeller flow passage (P2) is formed between two adjacent second blades (20). The outlet end of the first impeller flow passage has a first outlet, and the outlet end of the second impeller flow passage has a second outlet. The axial two ends of the first outlet and the axial two ends of the second outlet are respectively flush and have the same axial width. In the circumferential direction, the first outlet and the second outlet are alternately / spaced. The end of the first cover plate has a first wearing ring, and the end of the second cover plate has a second wearing ring. It is characterized in that: the first wearing ring (13) has a first wearing ring outer edge (131) and a first wearing ring inner edge (132). The first wearing ring outer edge is circular, and the first wearing ring inner edge is a first ellipse. The second wearing ring (23) has a second wearing ring outer edge and a second wearing ring inner edge (232). The second wearing ring outer edge is circular, and the second wearing ring inner edge is a second ellipse. The major axis (2a) of the first ellipse is perpendicular to the major axis of the second ellipse.

[0006] Further, the axial end of the hub (30) has a hub axial end outer edge (33). The hub axial end outer edge has a radius R. The first ellipse and / or the second ellipse has a major semi-axis a and a minor semi-axis b, and a = (1.05 - 1.2)b, R = (0.5 - 0.65)a.

[0007] Further, a plurality of grooves (331) are provided on the outer peripheral surface of the hub axial end outer edge (33), and the plurality of grooves are circumferentially distributed.

[0008] Further, the radial depth of the groove (331) is 0.25 - 0.4 times the radial thickness of the first hub portion (31), and the axial depth of the groove (331) is 0.5 - 2 times the radial thickness of the first hub portion (31).

[0009] Further, the first cover plate (11) has a first cover plate inner side wall (111). On the surface of the first cover plate inner side wall and within the first impeller flow passage (P1), there are provided uneven portions (112). The uneven portions are wavy and extend from the downstream of the first wearing ring (13) to the first outlet (12).

[0010] Further, in the circumferential direction, the uneven portions (112) are only provided in the area corresponding to the minor axis of the first ellipse, and this area is 60 - 150° in the circumferential direction.

[0011] Further, the second cover plate (21) has an inner side wall of the second cover plate. On the surface of the inner side wall of the second cover plate and within the second impeller passage (P2), there are provided second concave-convex portions which are wavy. The second concave-convex portions extend from the downstream of the second wearing ring to the second outlet; in the circumferential direction, the second concave-convex portions are only provided in the area corresponding to the minor axis of the second ellipse, and this area is 60-150° in the circumferential direction. This structure has the same concave-convex portion structure as the inner side wall of the first cover plate.

[0012] A design method for a double-suction impeller structure of a multistage centrifugal pump, characterized in that it includes the following steps:

[0013] When designing / calculating, the numerical parts of each parameter / each variable are taken for design / calculation;

[0014] 1) Determine the specific speed n of the double-suction impeller q , and calculate it in the following manner:

[0015]

[0016] In the formula: f q - The number of impeller suction inlets; Q BEP - The rated flow rate of the multistage pump; n - The rated speed; H BEP - The designed head;

[0017] 2) Determine the center line r of the impeller passage; the center line of the passage is a variant Archimedean spiral and is calculated according to the following equation:

[0018]

[0019] In the formula: r - The original center line of the passage; D2 - The outlet diameter of the passage; θ - The polar angle; - The included angle of the center line of the passage;

[0020] 3) Determine the outlet width b, the inclination angle T1 of the suction inlet cover plate on the first side of the impeller, the inclination angle T2 of the suction inlet cover plate on the second side of the impeller, the inlet diameter D’1 of the impeller, and the outlet diameter D'2 of the impeller; calculate in the following manner:

[0021]

[0022]

[0023]

[0024] T1 = T2 = 80° - 87°;

[0025] In the formula: g - The acceleration of gravity, H - The head of the first stage of the pump, Q - The flow rate of the first stage of the pump;

[0026] 4) Determine the blade thickness σ1, blade outlet angle β1, and blade wrap angle of the impeller flow path Wrap angle of the flow path center line Calculate according to the following formula:

[0027] σ1 = 4 - 8 mm;

[0028] β1 = 10° - 30°;

[0029]

[0030]

[0031] 5) Keep the impeller outlet velocity c2 and the outlet dynamic flow angle α2 unchanged;

[0032] 6) Ensure that the absolute flow angle α3 at the inlet of the first-stage volute is a constant value;

[0033] 7) Keep the impeller having a slightly lower head coefficient ψ to prevent rotating stall. The head coefficient ψ is calculated in the following way:

[0034]

[0035] Where: g - acceleration due to gravity, H - head of the first stage of the pump, u2 - circumferential velocity at the outer diameter of the impeller;

[0036] 8) The blades on both sides of the double-suction impeller are arranged alternately and crosswise at the outer diameter, including the blade pressure surface on the first side of the double-suction impeller, the blade suction surface on the first side of the double-suction impeller, the blade pressure surface on the second side of the double-suction impeller, and the blade suction surface on the second side of the double-suction impeller, strictly control the hydrodynamic reaction force on the blade, and introduce two functions of the local pressure coefficient C p and the overall lift coefficient C L for control. The pressure coefficient C p is calculated according to the following formula:

[0037]

[0038] The pressure coefficient C L is calculated according to the following formula:

[0039]

[0040] Where: c u - tangential velocity component, Z - number of impeller blades, r - radial component in the cylindrical coordinate system, x - axial component in the cylindrical coordinate system, B - blade height, f b - new blade distribution coefficient, w 1tip 、w2 - relative velocity vectors, u2 - circumferential velocity at the outer diameter of the impeller, L - impeller height;

[0041] 9) Two groups of flow channels are opened at the suction inlets at both ends of the double-suction impeller, symmetrically arranged with respect to the central plane of the double-suction impeller, and deflected by a certain angle γ. The deflection angle γ is calculated according to the following formula:

[0042] γ = 2π / Z;

[0043] In the formula: Z - the number of blades;

[0044] 10) Determine the flow coefficient The efficiency η and the power coefficient λ are calculated according to the following formula:

[0045]

[0046]

[0047]

[0048] In the formula: C - the shaft power, ΔP tot - the total pressure, ω - the rotational angular velocity.

[0049] A double-suction impeller structure for a multistage centrifugal pump and its design method according to the present invention can effectively improve the cavitation resistance performance of the centrifugal pump through the design of the inner edge of the wearing ring and the concave-convex part. Through this design method, the cavitation resistance performance of the centrifugal pump can be improved, thereby improving the overall efficiency of the centrifugal pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic diagram of the double-suction impeller structure of the prior art;

[0051] Figure 2 is a schematic diagram of the double-suction impeller structure of the present invention;

[0052] Figure 3 is a schematic diagram of the double-suction impeller structure of the present invention;

[0053] Figure 4 is a schematic diagram of the double-suction impeller structure of the present invention;

[0054] Figure 5 is a schematic diagram of the double-suction impeller structure of the present invention;

[0055] Figure 6 is a schematic diagram of the double-suction impeller structure of the present invention;

[0056] Figure 7 is a schematic diagram of the double-suction impeller structure of the present invention;

[0057] Figure 8 is a schematic diagram of the double-suction impeller structure of the present invention.

[0058] In the figure: the first blade 10, the first cover plate 11, the first outlet 12, the first impeller ring 13, the first impeller flow path P1, the outer edge 131 of the first impeller ring, the inner edge 132 of the first impeller ring, the inner side wall 111 of the first cover plate, the concave-convex part 112, the second blade 20, the second cover plate 21, the second outlet 22, the second impeller ring 23, the second impeller flow path P2, the hub 30, the first hub part 31, the second hub part 32, the outer edge 33 of the axial end of the hub part, the groove / notch 331. Detailed implementation mode

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0060] The present invention will be further described in detail below with reference to the accompanying drawings.

[0061] As Figure 2-7 shown, a double-suction impeller structure for a multistage centrifugal pump includes a first blade 10, a first cover plate 11, a first outlet 12, a first impeller ring 13, a first impeller flow path P1, a second blade 20, a second cover plate 21, a second outlet 22, a second impeller ring 23, a second impeller flow path P2, and a hub 30. The hub 30 includes symmetrically arranged first hub part 31 and second hub part 32. The first blade 10 and the second blade 20 are symmetrically arranged. The first impeller flow path P1 is formed between adjacent first blades 10, and the second impeller flow path P2 is formed between adjacent second blades 20. The outlet end of the first impeller flow path P1 has a first outlet 12, and the outlet end of the second impeller flow path P2 has a second outlet 22. The axial two ends of the first outlet 12 and the axial two ends of the second outlet 22 are respectively flush and have the same axial width. In the circumferential direction, the first outlet 12 and the second outlet 22 are alternately / spaced apart. The end of the first cover plate 11 has a first impeller ring 13, and the end of the second cover plate 21 has a second impeller ring 23. It is characterized in that: the first impeller ring 13 has an outer edge 131 of the first impeller ring and an inner edge 132 of the first impeller ring. The outer edge 131 of the first impeller ring is circular, and the inner edge 132 of the first impeller ring is a first ellipse. The second impeller ring 23 has an outer edge of the second impeller ring and an inner edge 232 of the second impeller ring. The outer edge of the second impeller ring is circular, and the inner edge 232 of the second impeller ring is a second ellipse. The major axis (2a) of the first ellipse is perpendicular to the major axis of the second ellipse.

[0062] As Figure 4-6As shown, further, the axial end of the hub 30 has an outer edge 33 of the axial end of the hub portion. The outer edge 33 of the axial end of the hub portion has a radius R. The first ellipse and / or the second ellipse have a major semi-axis a and a minor semi-axis b, where a = (1.05 - 1.2)b, preferably 1.1; and R = (0.5 - 0.65)a, preferably 0.6.

[0063] A double-suction impeller structure for a multistage centrifugal pump according to the present invention can effectively improve the cavitation resistance performance of the centrifugal pump through the design of the inner edge of the wearing ring.

[0064] Further, a plurality of grooves 331 are provided on the outer peripheral surface of the outer edge 33 of the axial end of the hub portion. The plurality of grooves 331 are evenly distributed in the circumferential direction. The radial depth of the groove 331 is 0.25 - 0.4 times the radial thickness of the first hub portion 31, and the axial depth of the groove 331 is 0.75 - 1.5 times the radial thickness of the first hub portion 31.

[0065] A double-suction impeller structure for a multistage centrifugal pump according to the present invention can further / better improve the cavitation resistance performance of the centrifugal pump through the cooperation of the groove 331 and the design of the inner edge of the wearing ring.

[0066] Further, the first cover plate 11 has an inner side wall 111 of the first cover plate. On the surface of the inner side wall 111 of the first cover plate and within the first impeller flow passage P1, there are provided uneven portions 112. The uneven portions 112 are in a wavy shape and extend from the downstream of the first wearing ring 13 to the first outlet 12.

[0067] Further, in the circumferential direction, the uneven portions 112 are only provided in the region / position corresponding to the minor axis of the first ellipse, and this region is 60 - 150° in the circumferential direction.

[0068] Further, the second cover plate 21 has an inner side wall of the second cover plate. On the surface of the inner side wall of the second cover plate and within the second impeller flow passage P2, there are provided second uneven portions. The second uneven portions are in a wavy shape and extend from the downstream of the second wearing ring 23 to the second outlet 22, having the same uneven portion structure as the inner side wall 111 of the first cover plate.

[0069] A double-suction impeller structure for a multistage centrifugal pump according to the present invention can further improve the cavitation resistance performance of the centrifugal pump through the design of the uneven portions 112.

[0070] A design method for a double-suction impeller structure for a multistage centrifugal pump includes the following steps:

[0071] When designing / calculating, the numerical parts of each parameter / variable are taken for design / calculation;

[0072] 1) Determine the specific speed n of the double-suction impeller q , and calculate according to the following method:

[0073]

[0074] Where: f q - Number of impeller suction inlets; Q BEP - Rated flow rate of multi-stage pump; n - Rated speed; H BEP - Designed head;

[0075] 2) Determine the center line r of the impeller flow passage; the center line of the flow passage is a variant Archimedean spiral and is calculated according to the following equation:

[0076]

[0077] Where: r - Original center line of the flow passage; D2 - Outlet diameter of the flow passage; θ - Polar angle; - Wrap angle of the center line of the flow passage;

[0078] 3) Determine the outlet width b, the inclination angle T1 of the first side suction inlet cover plate of the impeller, the inclination angle T2 of the second side suction inlet cover plate of the impeller, the impeller inlet diameter D1', and the impeller outlet diameter D'2; calculate according to the following method:

[0079]

[0080]

[0081]

[0082] T1 = T2 = 80° - 87°;

[0083] Where: g - Acceleration due to gravity, H - Head of the first stage of the pump, Q - Flow rate of the first stage of the pump, n - Rated speed;

[0084] 4) Determine the blade thickness σ1, blade outlet angle β1, and blade wrap angle of the impeller flow passage Wrap angle of the center line of the flow passage Calculate according to the following formula:

[0085] σ1 = 4 - 8 mm;

[0086] β1 = 10° - 30°;

[0087]

[0088]

[0089] 5) Keep the impeller outlet velocity c2 and the outlet dynamic flow angle α2 unchanged;

[0090] 6) Ensure that the absolute flow angle α3 at the inlet of the first-stage volute is a constant value;

[0091] 7) Keep the impeller having a slightly lower head coefficient ψ to prevent rotating stall. The head coefficient ψ is calculated as follows:

[0092]

[0093] Where: g - acceleration due to gravity, H - head of the first stage of the pump, u2 - circumferential velocity at the outer diameter of the impeller;

[0094] 8) The blades on both sides of the double-suction impeller are arranged alternately and crosswise at the outer diameter, including the blade pressure surface on the first side of the double-suction impeller, the blade suction surface on the first side of the double-suction impeller, the blade pressure surface on the second side of the double-suction impeller, and the blade suction surface on the second side of the double-suction impeller. Strictly control the hydrodynamic reaction force on the blades, and introduce two functions of the local pressure coefficient C p and the overall lift coefficient C L for control. The pressure coefficient C p is calculated according to the following formula:

[0095]

[0096] The pressure coefficient C L is calculated according to the following formula:

[0097]

[0098] Where: c u - tangential velocity component, Z - number of impeller blades, r - radial component in the cylindrical coordinate system, x - axial component in the cylindrical coordinate system, B - blade height, f b - new blade distribution coefficient, w 1tip , w2 - relative velocity vectors, u2 - circumferential velocity at the outer diameter of the impeller, L - impeller height;

[0099] 9) Two groups of flow channels opened at the suction inlets at both ends of the double-suction impeller are symmetrically arranged about the central plane of the double-suction impeller and deflected by a certain angle γ. The deflection angle γ is calculated according to the following formula:

[0100] γ = 2π / Z;

[0101] Where: Z - number of blades;

[0102] 10) Determine the flow coefficient efficiency η, and power coefficient λ, which are calculated according to the following formulas:

[0103]

[0104]

[0105]

[0106] Where: C - shaft power, ΔP tot - total pressure, ω - rotational angular velocity.

[0107] A double-suction impeller structure for a multistage centrifugal pump and a design method thereof according to the present invention can effectively improve the cavitation resistance performance of the centrifugal pump through the design of the inner edge of the wearing ring and the concave-convex part. Through this design method, the cavitation resistance performance of the centrifugal pump can be improved, thereby improving the overall efficiency of the centrifugal pump.

[0108] The above embodiments are illustrative of the present invention and not restrictive thereof. It can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A double-suction impeller structure for a multistage centrifugal pump, which comprises a first blade (10), a first cover plate (11), a first outlet (12), a first wearing ring (13), a first impeller flow passage (P1), a second blade (20), a second cover plate (21), a second outlet (22), a second wearing ring (23), a second impeller flow passage (P2), and a hub (30). The hub includes symmetrically arranged first hub portions (31) and second hub portions (32). The first blade and the second blade are symmetrically arranged. The first impeller flow passage (P1) is formed between two adjacent first blades, and the second impeller flow passage (P2) is formed between two adjacent second blades (20). The outlet end of the first impeller flow passage has a first outlet, and the outlet end of the second impeller flow passage has a second outlet. The axial two ends of the first outlet and the axial two ends of the second outlet are respectively flush and have the same axial width. In the circumferential direction, the first outlet and the second outlet are alternately / spaced apart. The end of the first cover plate has a first wearing ring, and the end of the second cover plate has a second wearing ring. It is characterized in that: The first mouth ring (13) has a first mouth ring outer edge (131) and a first mouth ring inner edge (132). The first mouth ring outer edge is circular, and the first mouth ring inner edge is a first ellipse. The second mouth ring (23) has a second mouth ring outer edge and a second mouth ring inner edge (232). The second mouth ring outer edge is circular, and the second mouth ring inner edge is a second ellipse. The major axis (2a) of the first ellipse is perpendicular to the major axis of the second ellipse.

2. The double-suction impeller structure for a multistage centrifugal pump according to claim 1, characterized in that, The axial end of the hub (30) has a hub axial end outer edge (33). The hub axial end outer edge has a radius R. The first ellipse and / or the second ellipse has a major semi-axis a and a minor semi-axis b, where a = (1.05 - 1.2)b and R = (0.5 - 0.65)a.

3. The double-suction impeller structure for a multistage centrifugal pump according to claim 2, wherein, A plurality of grooves (331) are provided on the outer peripheral surface of the hub axial end outer edge (33), and the plurality of grooves are circumferentially distributed.

4. The double-suction impeller structure for a multistage centrifugal pump according to claim 3, characterized in that, The radial depth of the groove (331) is 0.25 - 0.4 times the radial thickness of the first hub portion (31), and the axial depth of the groove (331) is 0.5 - 2 times the radial thickness of the first hub portion (31).

5. The double-suction impeller structure for a multistage centrifugal pump according to claim 2, characterized in that, The first cover plate (11) has a first cover plate inner side wall (111). On the surface of the first cover plate inner side wall and within the first impeller flow passage (P1), there are provided uneven portions (112). The uneven portions are wavy and extend from the downstream of the first mouth ring (13) to the first outlet (12).

6. The double-suction impeller structure for a multistage centrifugal pump according to claim 5, characterized in that, Circumferentially, the uneven portions (112) are only provided in the region corresponding to the minor axis of the first ellipse, and this region is 60 - 150° in the circumferential direction.

7. The double-suction impeller structure for a multistage centrifugal pump according to claim 6, characterized in that, The second cover plate (21) has a second cover plate inner side wall. On the surface of the second cover plate inner side wall and within the second impeller flow passage (P2), there are provided second uneven portions. The second uneven portions are wavy and extend from the downstream of the second mouth ring to the second outlet; circumferentially, the second uneven portions are only provided in the region corresponding to the minor axis of the second ellipse, and this region is 60 - 150° in the circumferential direction.

8. A design method for a double-suction impeller structure of a multistage centrifugal pump according to claim 7, characterized in that, It includes the following steps: When designing / calculating, take the numerical part of each parameter / each variable for design / calculation; 1) Determine the specific speed n of the double-suction impeller q , and calculate it in the following way: where: f q - number of impeller suction inlets; Q BEP - rated flow rate of multi-stage pump; n - rated speed; H BEP - designed head 2) Determine the flow path center line r of the impeller flow passage; the flow path center line is a variant Archimedean spiral and is calculated according to the following equation: Where: r - original center line of the flow channel; D2 - diameter of the flow channel outlet; θ - polar angle; - included angle of the center line of the flow channel; 3) Determine the outlet width b, the impeller first-side suction inlet cover plate inclination angle T1, the impeller second-side suction inlet cover plate inclination angle T2, the impeller inlet diameter D'1, and the impeller outlet diameter D'2; calculate according to the following method: T1 = T2 = 80° - 87°; Where: g - gravitational acceleration, H - the head of the first stage of the pump, Q - the flow rate of the first stage of the pump, n - rated speed; 4) Determine the blade thickness σ1, blade outlet angle β1, and blade wrap angle of the impeller flow path Wrap angle of the center line of the flow path Calculate according to the following formula: σ1 = 4 - 8mm; β1＝10°～30°； 5) Keep the impeller outlet velocity c2 and the outlet dynamic liquid flow angle α2 unchanged; 6) Ensure that the absolute liquid flow angle α3 at the inlet of the first-stage volute is a constant value; 7) Keep the impeller having a slightly lower head coefficient ψ to prevent rotating stall. The head coefficient ψ is calculated according to the following method: Where: g - gravitational acceleration, H - the head of the first stage of the pump, u2 - the circumferential velocity at the outer diameter of the impeller.

9. The design method according to claim 8, wherein It also includes: 8) The blades on both sides of the double-suction impeller are arranged alternately and crosswise at the outer diameter, including the blade pressure surface on the first side of the double-suction impeller, the blade suction surface on the first side of the double-suction impeller, the blade pressure surface on the second side of the double-suction impeller, and the blade suction surface on the second side of the double-suction impeller. The hydrodynamic reaction force on the blades is strictly controlled, and two functions of the local pressure coefficient C p and the overall lift coefficient C L are introduced for control. The pressure coefficient C p is calculated according to the following formula: Pressure coefficient C L Calculated according to the following formula: Where: c u - tangential velocity component, Z - number of impeller blades, r - radial component in the cylindrical coordinate system, x - axial component in the cylindrical coordinate system, B - blade height, f b - new blade distribution coefficient, w 1tip 、w2 - relative velocity vectors, u2 - circumferential velocity at the outer diameter of the impeller, L - impeller height; 9) Two groups of flow passages opened at both suction inlets of the double-suction impeller are symmetrically arranged about the central plane of the double-suction impeller and deflected by a certain angle γ. The deflection angle γ is calculated according to the following formula: γ = 2π / Z; Where: Z - number of blades; 10) Determine the flow coefficient The efficiency η and power coefficient λ are calculated according to the following formulas: Where: C - shaft power, ΔP tot - total pressure, ω - rotational angular velocity.

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