Low-noise parallel impeller and design method thereof

Abstract

The invention belongs to the technical field of centrifugal pumps, and particularly relates to a low-noise parallel impeller and a design method thereof.When the impeller rotates, high-speed outflow of a front-side impeller located on the front side of a separator and high-speed outflow of a rear-side impeller located on the rear side of the separator interfere with a separation tongue in sequence, induced high-amplitude blade frequency signals are staggered within the sampling time, and the high-speed outflow of the front-side impeller located on the front side of the separator and the high-speed outflow of the rear-side impeller located on the rear side of the separator interfere with the separation tongue in sequence; a certain phase difference existing in pressure pulsation induced by intensity overlapping and dynamic and static interference is avoided in the time domain, the parallel staggered impeller structure can effectively restrain pressure pulsation energy, vibration noise generated by dynamic and static interference can be weakened easily, and therefore the operation stability of the pump is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of centrifugal pumps, and in particular relates to a low-noise parallel impeller and a design method thereof. Background Art

[0002] As an important fluid machinery with a wide range of applications, centrifugal pumps are developing towards high efficiency, stability and low noise, while vibration noise has a great impact on their safe and stable operation. Therefore, it is of great significance to focus on the unsteady flow structure and excitation characteristics in the pump under the action of dynamic-static interference and explore the dynamic-static interference suppression mechanism based on phase difference control.

[0003] The hydraulic excitation factors inside the centrifugal pump mainly include static-dynamic interference, cavitation, secondary flow, backflow, and flow separation, and the excitation characteristics of different flow structures are different. Among them, the pressure pulsation caused by static-dynamic interference triggers the alternating hydraulic excitation force, which is the main factor inducing centrifugal pump vibration, noise and other phenomena. As the most important hydraulic excitation source in the pump, static-dynamic interference is externally characterized by strong and periodic pressure signal fluctuations, and the spectrum shows discrete excitation frequency characteristics.

[0004] There are means for suppressing dynamic-static interference in the prior art, but such means are not effective enough in suppressing the pressure pulsation energy at the interference frequency in the pump. Summary of the invention

[0005] The object of the present invention is to provide a low-noise parallel impeller and a design method thereof to solve the above-mentioned problems.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A low-noise parallel impeller, comprising: a separator, wherein the side of the separator facing the impeller water inlet is the front side, a plurality of first blades are fixedly connected to the front side of the separator, the plurality of first blades constitute a front impeller, the plurality of first blades are arranged at equal intervals in the circumferential direction, a front cover plate is fixedly connected to the side of the front impeller away from the separator, and the front cover plate is arranged coaxially with the separator;

[0008] A plurality of second blades are fixedly connected to the rear side of the separator, the plurality of second blades constitute a rear impeller, the plurality of second blades are arranged at equal intervals in the circumferential direction, a rear cover plate is fixedly connected to the side of the rear impeller away from the separator, the rear cover plate and the separator are arranged at equal intervals in the circumferential direction, and the outlet flow of the rear impeller is equal to the outlet flow of the front impeller;

[0009] The separator divides the water inlet of the impeller into a front flow channel and a rear flow channel, the front flow channel is connected to the front impeller, and the rear flow channel is connected to the rear impeller;

[0010] The number of the first blades is equal to the number of the second blades, and the first blades and the second blades are arranged alternately.

[0011] Preferably, a flow optimization groove is opened on the front side of the separator, and the flow optimization groove is spirally arranged in a direction away from the axis, and the flow optimization groove is coaxially arranged with the separator.

[0012] A design method for a low-noise parallel impeller comprises the following steps:

[0013] Determine the number z of the second blades according to the specific speed;

[0014] Determine the first parameter and the second parameter of the conventional impeller blade according to the design flow Q and the design speed n of the centrifugal pump, determine the third parameter of the rear impeller according to the preset relationship between the first parameter and the third parameter, determine the fourth parameter of the rear impeller according to the preset relationship between the second parameter and the fourth parameter, determine the streamline parameter of the rear side of the divider according to the third parameter and the fourth parameter of the rear impeller, determine the fifth parameter of the front impeller according to the preset relationship between the third parameter and the fifth parameter, determine the sixth parameter of the front impeller according to the preset relationship between the fourth parameter and the sixth parameter, and determine the streamline parameter of the front side of the divider according to the fifth parameter and the sixth parameter of the front impeller;

[0015] The first parameter is the diameter D of the conventional impeller blade inlet end. 1 , the second parameter is the width b of the conventional impeller blade outlet 2 , the third parameter is the diameter D of the rear impeller inlet 1 ', the fourth parameter is the width b of the rear impeller outlet 2 ', the fifth parameter is the diameter D of the front impeller inlet 1 ", the sixth parameter is the width b of the front impeller outlet 2 ”.

[0016] Preferably, the angle between two adjacent first blades / two adjacent second blades is θ 1 ,θ 1 The calculation formula is:

[0017] θ 1 =360 / z;

[0018] Wherein, z is the number of the front impellers / rear impellers.

[0019] Preferably, the misalignment angle between the adjacent first blade and the second blade is θ 2 ,θ 2 The calculation formula is:

[0020]

[0021] Preferably, the thickness parameter b of the separator is determined according to a preset relationship between the thickness parameter δ of the first blade / the second blade and the thickness parameter b of the separator.

[0022] Preferably, the calculation formula of the third parameter of the rear impeller is:

[0023]

[0024] Preferably, the calculation formula of the fourth parameter of the rear impeller is:

[0025] b′ 2 =0.5b 2 .

[0026] Preferably, the calculation formula of the fifth parameter of the front impeller is:

[0027]

[0028] Preferably, the calculation formula of the sixth parameter of the front impeller is:

[0029] b″ 2 = b′ 2 .

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] When the impeller of the present invention rotates, the high-speed outflows of the front impeller located on the front side of the separator and the rear impeller located on the rear side of the separator interfere with the partition tongue respectively, and the induced high-amplitude blade frequency signals are staggered within the sampling time, thereby avoiding intensity overlap in the time domain. The pressure pulsation induced by dynamic and static interference has a certain phase difference, so that the parallel staggered impeller structure can effectively suppress the pressure pulsation energy, which is beneficial to reducing the vibration noise generated by dynamic and static interference, thereby improving the operation stability of the pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor:

[0033] Figure 1 It is an overall schematic diagram of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of the separator in the present invention;

[0035] Figure 3 is a front view of the separator in the present invention;

[0036] Figure 4 is a cross-sectional view of the flow optimization groove in the present invention;

[0037] Figure 5 It is a front view of the front impeller and the rear impeller in the present invention;

[0038] Figure 6 It is a flow chart of the design method of the low-noise parallel impeller in the present invention;

[0039] Figure 7 This is a comparison chart of the hydraulic performance of a conventional impeller and three types of staggered angle impellers;

[0040] Figure 8 This is a frequency domain comparison diagram of pressure pulsation at the monitoring point near the tongue of a conventional impeller and three types of staggered impellers;

[0041] Among them, 1. front cover plate; 3. front impeller; 4. separator; 6. rear impeller; 7. rear cover plate. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Reference Figures 1 to 6 The present invention discloses a low-noise parallel impeller, comprising: a separator 4, the side of the separator 4 facing the impeller water inlet is the front side, a plurality of first blades are fixedly connected to the front side of the separator 4, the plurality of first blades constitute a front impeller 3, the plurality of first blades are arranged at equal intervals in the circumferential direction, a front cover plate 1 is fixedly connected to the side of the front impeller 3 away from the separator 4, and the front cover plate 1 is coaxially arranged with the separator 4;

[0045] A plurality of second blades are fixedly connected to the rear side of the separator 4, and the plurality of second blades constitute a rear impeller 6, and the plurality of second blades are arranged at equal intervals in the circumferential direction. A rear cover plate 7 is fixedly connected to the side of the rear impeller 6 away from the separator 4, and the rear cover plate 7 and the separator 4 are arranged at equal intervals in the circumferential direction. The outlet flow rate of the rear impeller 6 is equal to the outlet flow rate of the front impeller 3;

[0046] The separator 4 divides the water inlet of the impeller into a front flow channel and a rear flow channel, the front flow channel is connected to the front impeller 3, and the rear flow channel is connected to the rear impeller 6;

[0047] The number of the first blades is equal to the number of the second blades, and the first blades and the second blades are arranged alternately.

[0048] As a further optimization solution, a flow optimization groove is opened on the front side of the separator 4 , the flow optimization groove is spirally arranged in a direction away from the axis, and the flow optimization groove is coaxially arranged with the separator 4 .

[0049] A design method for a low-noise parallel impeller comprises the following steps:

[0050] Determine the number of blades z of the rear impeller 6 according to the specific speed;

[0051] When 30≤n s <45, z = 8-10;

[0052] When 45≤n s <60, z = 7-8;

[0053] When 60≤n s <120, z = 6-7;

[0054] When 120≤n s <300, z = 4-6;

[0055] n s is the specific speed;

[0056] Determine the first parameter and the second parameter of the conventional impeller blade according to the design flow Q and the design speed n of the centrifugal pump, determine the third parameter of the rear impeller 6 according to the preset relationship between the first parameter and the third parameter, determine the fourth parameter of the rear impeller 6 according to the preset relationship between the second parameter and the fourth parameter, determine the streamline parameter of the rear side of the divider 4 according to the third parameter and the fourth parameter of the rear impeller 6, determine the fifth parameter of the front impeller 3 according to the preset relationship between the third parameter and the fifth parameter, determine the sixth parameter of the front impeller 3 according to the preset relationship between the fourth parameter and the sixth parameter, and determine the streamline parameter of the front side of the divider 4 according to the fifth parameter and the sixth parameter of the front impeller 3;

[0057] The first parameter is the diameter D of the conventional impeller blade inlet end. 1 , the second parameter is the width b of the conventional impeller blade outlet 2 The third parameter is the diameter D of the inlet end of the rear impeller 6 1 ', the fourth parameter is the width b of the outlet end of the rear impeller 6 2 ', the fifth parameter is the diameter D of the inlet end of the front impeller 3 1 ", the sixth parameter is the width b of the outlet end of the front impeller 3 2 ”.

[0058] Further optimization scheme, the angle between two adjacent first blades / two adjacent second blades is θ 1 ,θ 1 The calculation formula is:

[0059] θ 1 =360 / z;

[0060] Wherein, z is the number of front impellers 3 / rear impellers 6.

[0061] Further optimization scheme, the misalignment angle between the adjacent first blade and the second blade is θ 2 ,θ 2 The calculation formula is:

[0062]

[0063] θ 2 Preferred are 15°, 30°, 45°;

[0064] In a further optimization scheme, the thickness parameter b of the separator 4 is determined according to a preset relationship between the thickness parameter δ of the first blade / the second blade and the thickness parameter b of the separator 4 .

[0065] Further optimizing the solution, the calculation formula of the third parameter of the rear impeller 6 is:

[0066]

[0067] Further optimizing the scheme, the calculation formula of the fourth parameter of the rear impeller 6 is:

[0068] b′ 2 =0.5b 2 .

[0069] Further optimizing the scheme, the calculation formula of the fifth parameter of the front impeller 3 is:

[0070]

[0071] Further optimizing the scheme, the calculation formula of the sixth parameter of the front impeller 3 is:

[0072] b″ 2 = b′ 2 .

[0073] Design Methodology:

[0074] Determine the traditional impeller inlet diameter D according to the design flow Q and design speed n 1 , outlet width b 2 , according to the diameter D of the conventional impeller blade inlet 1 The diameter D of the inlet end of the rear impeller 6 1 'The preset relationship between Obtain Outlet flow rate Q at the rear impeller 6 2 The outlet flow rate Q at the front impeller 3 1 Equal, design flow Q = Q 2 +Q 1 , so the width b of the outlet of the rear impeller 6 is 2 'Compared to the conventional impeller blade outlet width b 2 The default relationship is b′ 2 =0.5b 2 ;

[0075] According to the diameter D of the inlet end of the rear impeller 6 1 ' and the width b of the outlet end of the rear impeller 6 2 'Determine the rear streamline parameters of the separator 4;

[0076] According to the diameter D of the inlet end of the rear impeller 6 1 'Diameter D of the inlet end of the front impeller 3 1 The preset relationship between Determine the diameter D of the inlet end of the front impeller 3 1 ", according to the width b of the outlet end of the rear impeller 6 2 'Width b of the outlet end of the front impeller 3 2 "The preset relationship between b" 2 = b′ 2 Determine the width b of the outlet end of the front impeller 3 2 ", according to the diameter D of the inlet end of the front impeller 3 1 " and the width b of the outlet end of the front impeller 3 2 "Determine the front streamline parameters of the separator 4 to ensure that the flow area of ​​the impeller flow channel is monotonically increasing and the flow area of ​​the front side of the separator 4 is equal to the flow area of ​​the rear side;

[0077] The outlet placement angle and wrap angle of the front impeller 3 and the rear impeller 6 are the same; when the highest efficiency point of the impeller is biased towards a small flow rate, the blade inlet placement angle or throat area is adjusted.

[0078] The thickness of the separator 4 is b=0.5δ~1.0δ, where δ is the thickness of the front impeller 3 / rear impeller 6;

[0079] The flow optimization groove is set to be spiral, the inner wall of the flow optimization groove is set to be a smooth surface, and the radius of the flow optimization groove is r from the center of the separator 4 to the surroundings. 1 、r 2 、r 3 、r 4 The inlet and outlet sections of the optimized slot are both provided with fillets, and the radius of the fillets is r 5 ;

[0080] r 1 =1.1~1.2R 1 , R 1 is the inner diameter of the separator 4,

[0081] r i+1 =1.1~1.2r i , where (i=1, 2, 3);

[0082] m = 1.1 to 1.2b; m is the width of the flow optimization groove;

[0083] r 5 =0.5m;

[0084] t=0.1~0.15b; t is the maximum depth of the flow optimization groove;

[0085] The cross section of the flow optimization groove consists of three arcs. The radius of the arc in the middle is r, and the radius of the arcs at both ends is r'.

[0086] r=0.5~0.6(r i+1 -r i );

[0087] r'=r i+1 -r i ;

[0088] i=1, 2, 3.

[0089] One specific example:

[0090] The design parameters Q, H, and n of a single-stage centrifugal pump are known. The rear impeller 6 is designed first, and then the front impeller 3 is designed. During the design, the key characteristic parameters that affect the head and efficiency, such as the number of blades, blade outlet placement angle, wrap angle, and volute throat area, are adjusted in a targeted manner to meet the design requirements, and finally the parallel staggered impeller scheme is determined.

[0091] With a specific speed n s = 69 single-stage single-suction centrifugal pump impeller design as a reference, its design parameters are: Q = 55m 3 / h, H=20m, n=1450r / min, D 1 =80mm, b 2 =15mm, D 2 =250mm.

[0092] Determine the hydraulic parameters of the rear impeller of the parallel impeller:

[0093] Rear impeller inlet diameter D' 1 :

[0094] Rear impeller outlet diameter D'2 :D′ 2 =D 2 ;

[0095] Rear impeller outlet width b' 2 :b′ 2 =0.5b 2 =7.5mm; the specific value of the blade inlet and outlet angle is

[0096] Span <![CDATA[β 1 (°)]]> <![CDATA[β 2 (°)]]> Hub 1 33.4 30 2 31.5 30 Middle 3 29.5 30 4 27.6 30 Shroud 5 25.6 30

[0097] The number of first blades / second blades z=6.

[0098] After determining the rear impeller 6, calculate the inlet diameter D of the front impeller 3 1 ”, making D″ 1 =84.34mm, wheel hub diameter D″ H =D' 1 +2b=62.57mm, where b=3mm.

[0099] Front impeller outlet width b″ 2 =b' 2 =7.5mm.

[0100] The thickness of the separator 4 is 3 mm, and the angle between two adjacent first blades / two adjacent second blades is 60°;

[0101] When θ 2 The hydraulic performance of the pump is optimal when the displacement is 30°, that is, half the angle.

[0102] According to the streamline of the front cover of the rear impeller, the thickness of the baffle is reserved so that the thickness of the baffle is basically uniform from the impeller inlet to the outlet, thereby determining the streamline of the rear cover of the front impeller. Adjust the streamline of the front cover of the front impeller to ensure that the flow area of ​​the impeller flow channel is monotonically increasing, and the flow area is basically consistent with the flow area of ​​the rear impeller; when designing the blades, keep the outlet placement angle and wrap angle of the front and rear impellers the same; perform numerical calculations on the parallel staggered impellers. If the highest efficiency point is biased towards a small flow rate, adjust the blade inlet placement angle or throat area. Determine the hydraulic parameters of the final impeller scheme: Z = 6, the outlet width of the parallel staggered impeller is 18mm, the inlet diameter is 84.34mm, and the wrap angle Φ = 115°.

[0103] The present invention reconstructs the conventional impeller structure based on the phase difference effect. Figure 7 and 8As shown in the figure, through numerical calculation, it is found that the hydraulic performance of the parallel impeller is better than that of the conventional impeller, and the amplitude of the impeller outlet is reduced. When the impeller rotates, the high-speed outflow of the front and rear impellers interfere with the diaphragm tongue respectively, and the induced high-amplitude impeller frequency signals are staggered in the sampling time, avoiding the intensity overlap in the time domain. The pressure pulsation induced by the dynamic and static interference has a certain phase difference, so that the parallel impeller structure can effectively suppress the pressure pulsation energy, which is conducive to reducing the vibration noise generated by the dynamic and static interference, thereby improving the operation stability of the pump and providing a certain reference for the design of low-noise pumps.

[0104] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0105] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-noise parallel impeller, characterized in that: include: A separator (4), wherein the side of the separator (4) facing the impeller water inlet is the front side, a plurality of first blades are fixedly connected to the front side of the separator (4), the plurality of first blades constitute the front impeller (3), the plurality of first blades are arranged at equal intervals in the circumferential direction, a front cover plate (1) is fixedly connected to the side of the front impeller (3) away from the separator (4), and the front cover plate (1) is arranged coaxially with the separator (4); A plurality of second blades are fixedly connected to the rear side of the separator (4), the plurality of second blades forming a rear impeller (6), the plurality of second blades being arranged at equal intervals in the circumferential direction, a rear cover plate (7) is fixedly connected to the side of the rear impeller (6) away from the separator (4), the rear cover plate (7) and the separator (4) being arranged at equal intervals in the circumferential direction, and the outlet flow rate of the rear impeller (6) is equal to the outlet flow rate of the front impeller (3); The separator (4) divides the water inlet of the impeller into a front flow channel and a rear flow channel, the front flow channel is connected to the front impeller (3), and the rear flow channel is connected to the rear impeller (6); The number of the first blades is equal to the number of the second blades, and the first blades and the second blades are arranged alternately.

2. A low-noise parallel impeller according to claim 1, characterized in that: A flow optimization groove is provided on the front side of the separator (4), the flow optimization groove is spirally arranged in a direction away from the axis, and the flow optimization groove is coaxially arranged with the separator (4).

3. A design method for a low-noise parallel impeller according to any one of claims 1 to 2, characterized in that: The following steps are involved: Determine the number z of the second blades according to the specific speed; Determining the first parameter and the second parameter of the conventional impeller blade according to the design flow Q and the design speed n of the centrifugal pump, determining the third parameter of the rear impeller (6) according to the preset relationship between the first parameter and the third parameter, determining the fourth parameter of the rear impeller (6) according to the preset relationship between the second parameter and the fourth parameter, determining the streamline parameter of the rear side of the separator (4) according to the third parameter and the fourth parameter of the rear impeller (6), determining the fifth parameter of the front impeller (3) according to the preset relationship between the third parameter and the fifth parameter, determining the sixth parameter of the front impeller (3) according to the preset relationship between the fourth parameter and the sixth parameter, and determining the streamline parameter of the front side of the separator (4) according to the fifth parameter and the sixth parameter of the front impeller (3); The first parameter is the diameter D1 of the inlet end of the conventional impeller blade, the second parameter is the width b2 of the outlet end of the conventional impeller blade, the third parameter is the diameter D1' of the inlet end of the rear impeller (6), the fourth parameter is the width b2' of the outlet end of the rear impeller (6), the fifth parameter is the diameter D1'' of the inlet end of the front impeller (3), and the sixth parameter is the width b2'' of the outlet end of the front impeller (3).

4. The design method of a low-noise parallel impeller according to claim 3 is characterized in that: The angle between two adjacent first blades / two adjacent second blades is θ1, and the calculation formula of θ1 is: θ1=360 / z; Wherein, z is the number of the front impellers (3) / rear impellers (6).

5. The design method of a low-noise parallel impeller according to claim 3 is characterized in that: The misalignment angle between the adjacent first blade and the second blade is θ2, and the calculation formula of θ2 is:

6. The design method of a low-noise parallel impeller according to claim 3 is characterized in that: The thickness parameter b of the separator (4) is determined according to a preset relationship between the thickness parameter δ of the first blade / the second blade and the thickness parameter b of the separator (4).

7. The design method of a low-noise parallel impeller according to claim 6 is characterized in that: The calculation formula of the third parameter of the rear impeller (6) is:

8. The design method of a low-noise parallel impeller according to claim 7, characterized in that: The calculation formula of the fourth parameter of the rear impeller (6) is: b′2=0.5b2.

9. The design method of a low-noise parallel impeller according to claim 8, characterized in that: The calculation formula of the fifth parameter of the front impeller (3) is:

10. The design method of a low-noise parallel impeller according to claim 8, characterized in that: The calculation formula of the sixth parameter of the front impeller (3) is: b″2=b′2.

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