Two-stage cryogenic deep well pump design method

Abstract

This invention discloses a design method for a two-stage cryogenic deep well pump. The two-stage cryogenic deep well pump includes, from front to back, an inducer wheel, a first-stage impeller, a spatial guide vane, a second-stage impeller, and radial guide vanes arranged on a rotating shaft. The inducer wheel includes a hub connected to the rotating shaft and inducer wheel blades connected to the hub. The spatial guide vanes divide the flow channels into several channels through their own blades, and the radial guide vanes contain only positive blades. The design method includes the following steps: S1, designing the inducer wheel; S2, designing the first-stage impeller and the second-stage impeller; S3, designing the spatial guide vanes; S4, designing the radial guide vanes. This invention can be used to design high-efficiency two-stage LNG cryogenic deep well pumps. By improving the shape and size parameters of the inducer wheel, cavitation resistance can be guaranteed. Furthermore, based on the size parameters of the inducer wheel, a matching first-stage impeller is designed, followed by the design of the spatial guide vanes, the second-stage impeller, and the radial guide vanes. The resulting product has high hydraulic efficiency.

Description

Technical Field

[0001] This invention relates to the field of liquid transportation technology, and specifically to a design method for a two-stage cryogenic deep well pump. Background Technology

[0002] Cryogenic deep well pumps are unique centrifugal pumps specifically designed for handling cryogenic fluids, including liquefied natural gas (LNG), liquefied petroleum gas (LPG), liquid ethylene, propylene, ethane, and various other cryogenic liquids. Cryogenic pumps are key equipment in LNG receiving terminal processes, primarily used for loading, unloading, transporting, and pressurizing LNG. Cryogenic pumps for LNG transport not only need to meet the requirements of general cryogenic liquid pumps but also have high requirements for sealing and explosion-proof performance. Submersible electric pumps are commonly used for LNG transport in domestic and international receiving terminals. These are centrifugal liquid pumps practical for cryogenic environments, with their impellers operating below the liquid surface.

[0003] Marine deep-well pumps are commonly used cargo pumps on small liquefied petroleum gas (LPG) ships, and can also be used on small liquefied natural gas (LNG) ships with a capacity of less than 50,000 cubic meters. The drive motor is mounted on the top deck of the cargo tank, while the pump body is placed inside the suction well at the bottom of the cargo tank. The drive motor is an explosion-proof motor, located on top outside the impeller, and the drive shaft is supported by a central guide bearing inside the discharge riser. Currently, marine deep-well pumps can also be used for main engine power supply, demonstrating their wide range of applications.

[0004] Cryogenic pumps used in large LNG carriers and LNG storage tanks are mostly multi-stage centrifugal pumps, belonging to the fully immersed type. Their main components include: guide vanes, motors, diffusers, impellers, main shafts, bearings, vibration detectors, and a thrust balancing mechanism (TEM). The challenges in LNG pump technology development lie in the fact that, because the entire pump is immersed in LNG liquid at 111K, its motor, actuators, impeller, and lead cables must also withstand extremely low temperatures. Furthermore, during transportation, LNG is near its saturation temperature; even a slight temperature change can cause LNG vaporization, which may lead to cavitation and affect the pump's transport performance. Therefore, existing LNG cryogenic deep well pumps have relatively low efficiency. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a design method for a two-stage cryogenic deep well pump, which can be used to design a high-efficiency two-stage LNG cryogenic deep well pump. By improving the shape and size parameters of the inducer, cavitation resistance can be guaranteed. Furthermore, based on the size parameters of the inducer, a matching first-stage impeller is designed, followed by the design of spatial guide vanes, second-stage impellers, and radial guide vanes, resulting in a product with high hydraulic efficiency.

[0006] The present invention discloses a design method for a two-stage cryogenic deep well pump, wherein the two-stage cryogenic deep well pump includes an inducer wheel, a first-stage impeller, a spatial guide vane, a second-stage impeller, and a radial guide vane arranged from front to back on a rotating shaft; the inducer wheel includes a hub connected to the rotating shaft and inducer wheel blades connected to the hub; the spatial guide vane divides several flow channels through its own blades; and the radial guide vane contains only positive blades.

[0007] The design method includes the following steps:

[0008] S1. Design the inducer wheel; design the leading edge of the inducer wheel blades to be knife-edge shaped, design the actual radius of the leading edge based on the maximum thickness of the inducer wheel, grind the back of the inducer wheel blade inlet to make the blade tip sharp, grind the inlet radius on the back of the inlet and the outlet radius on the working surface of the inducer wheel blade outlet, and grind the inlet length and outlet length of the inducer wheel based on the blade edge thickness; design the inlet and outlet edge shapes of the inducer wheel blades, the inducer wheel diameter, the inlet and outlet angles of the inducer wheel blades, and the number of inducer wheel blades;

[0009] S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller is matched with the inducer; the design method of the second-stage impeller is the same as that of the first-stage impeller;

[0010] S3. Design the spatial guide vane; the spatial guide vane is matched with the first-stage impeller;

[0011] S4. Design the radial guide vane; the radial guide vane is matched with the secondary impeller.

[0012] Furthermore, step S1 includes:

[0013] S101, The leading edge of the inducer blade is knife-edge shaped, and the maximum thickness of the inducer is δ. max The actual radius of the leading edge is The back surface of the inlet of the inducer blade is ground to make the blade tip sharp. The inlet radius R1 of the back surface of the inlet is ground to be 0.1mm to 0.4mm, and the inlet length of the inducer is ground to be L1 to 8δ to 12δ. The outlet radius R2 of the outlet working surface of the inducer blade is ground to be 0.2mm to 0.8mm, and the outlet length is ground to be L2 to 6δ to 8δ, where δ is the blade edge thickness.

[0014] S102. Determine the inlet and outlet edge shapes of the inducer blades: the outlet edge of the inducer is located on the same axial plane, and the sweep angle of the inducer is... It is the angle of rotation of the inlet edge radius in the opposite direction; the wrap angle of the inducer blade rim is... The hub wrap angle of the inducer blade is in,

[0015] S103. Determine the diameter of the inducer wheel: The inducer wheel is a cylindrical variable pitch inducer wheel, and the inlet diameter of the inducer wheel blades is... Inducer wheel hub diameter Where Q is the pump flow rate, n is the pump speed, and φ = 0.1 to 0.14.

[0016] S104. Determine the inlet and outlet angles of the inducer blades: Inlet angle β of the inducer blades y1 =β′ y1 +Δβ y1 Inducer blade exit angle β y2 =β′ y2 +Δβ y2 ; where β y ′1 is the angle between the rim inlet diameter and the fluid flow angle, Δβ y1 =0°~5°; β' y2 Δβ is the angle between the outlet diameter and the liquid flow angle. y2 =1°-3°;

[0017] S105. Determine that the number of blades of the inducer wheel is 3.

[0018] Furthermore, step S2 includes:

[0019] S201. Determine that the number of blades of the first-stage impeller or the second-stage impeller is twice the number of blades of the inducer wheel;

[0020] S202. Determine the inlet diameter of the first-stage or second-stage impeller.

[0021] in, k0 = 4.5~5.5, n is the pump speed, Q is the pump flow rate, d h The diameter of the induction wheel hub;

[0022] S203. Determine the outlet diameter of the first-stage impeller. Or the outlet diameter of the second-stage impeller Where n is the pump speed and Q is the pump flow rate. k D3 =1.022~1.024, n s1 The specific speed of the first-stage impeller. H1 is the head of the first stage impeller; n s2 The specific speed of the second-stage impeller. H2 is the head of the second-stage impeller;

[0023] S204. Determine the outlet width of the first-stage impeller. Or the outlet width of the second-stage impeller

[0024] in, k b3 =1.078~1.055, n s1 The specific speed of the first-stage impeller in step S203; n s2 The specific speed of the second-stage impeller in step S203;

[0025] S205. Determine the inlet angle β1 and outlet angle β2 of the first-stage impeller; the blade inlet angle of attack Δβ = β1 - β1′ of the first-stage impeller, where the blade inlet angle of attack Δβ is the positive angle of attack and β1′ is the relative angle of liquid flow at the blade inlet; the outlet angle β2 = 22° to 30°.

[0026] Furthermore, step S3 includes:

[0027] S301. Determine the axial distance between the inlet edge of the space guide vane and the rear cover plate at the outlet edge of the first-stage impeller as ΔL = 1.5b. 2m , where b 2m The outlet width of the first-stage impeller in step S204;

[0028] S302. Determine that the number of blades of the spatial guide vane is twice the number of blades of the first-stage impeller minus one.

[0029] S303. Determine the axial length L3 of the spatial guide vane as 0.5D. 2m ~0.7D 2m , where D 2m The outlet diameter of the first-stage impeller in step S203;

[0030] S304. Determine the blade wrap angle of the spatial guide vane.

[0031] Furthermore, step S4 includes:

[0032] Step S401: Determine that the number of blades of the radial guide vane is 9;

[0033] Step S402: Determine the base circle diameter D3 of the radial guide vane. 2n +2mm≤D3≤D 2n +10mm, where D 2n The outlet diameter of the secondary impeller in step S203;

[0034] Step S403: Determine the inlet width b3 of the radial guide vane positive blade. 2n +2mm≤b3≤b 2n +5mm, where b 2n The outlet width of the secondary impeller in step S204;

[0035] Step S404: Determine the length L4 of the diffuser section of the radial guide vane positive blade = 2.4b3;

[0036] Step S405: Determine the exit width b4 of the radial guide vane positive blade as b3 + 12 mm.

[0037] The beneficial effects of this invention are as follows: This invention can be used to design high-efficiency two-stage LNG cryogenic deep well pumps, and can ensure cavitation resistance by improving the shape and size parameters of the inducer. Furthermore, based on the size parameters of the inducer, a matching first-stage impeller is designed, followed by the design of spatial guide vanes, second-stage impellers, and radial guide vanes. The radial guide vanes only contain positive blades to facilitate connection with the subsequent outflow section and reduce local hydraulic losses. When hydraulically designing the first and second-stage impellers, a head margin is retained to facilitate subsequent impeller cutting. During the assembly of the first-stage impeller with the spatial guide vanes and the second-stage impeller with the radial guide vanes, the first and second-stage impellers are cut to increase the assembly gap between the first and second-stage impellers and the corresponding guide vanes, enlarging the transition section and improving the hydraulic efficiency of the assembled flow components. Attached Figure Description

[0038] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0039] Figure 1 This is a schematic diagram of the flow channel of the two-stage cryogenic deep well pump of the present invention;

[0040] Figure 2 This is a schematic diagram of the flow channel assembly of the inducer and the first-stage impeller of the two-stage cryogenic deep well pump of the present invention;

[0041] Figure 3 This is a schematic diagram of the flow channel assembly of the first-stage impeller and the space guide vane of the two-stage cryogenic deep well pump of the present invention.

[0042] Figure 4 This is a schematic diagram of the flow channel assembly of the second-stage impeller and radial guide vanes in the two-stage cryogenic deep well pump of the present invention;

[0043] Figure 5 This is a schematic diagram of the flow channel of the inducer wheel of the two-stage cryogenic deep well pump of the present invention;

[0044] Figure 6 This is a schematic diagram of the flow channel of the first-stage impeller of the two-stage cryogenic deep well pump of the present invention;

[0045] Figure 7 This is a schematic diagram of the flow channel of the spatial guide vane of the two-stage cryogenic deep well pump of the present invention;

[0046] Figure 8 This is a schematic diagram of the flow channel of the radial guide vanes of the two-stage cryogenic deep well pump of the present invention.

[0047] The following labels are used in the attached diagram: 1-Inlet section fluid domain, 2-Inducer wheel fluid domain, 3-First stage impeller fluid domain, 31-First stage impeller final flow channel, 32-First stage impeller outlet edge cut section, 4-Spatial guide vane fluid domain, 41-Increased clearance of spatial guide vane, 42-Spatial guide vane design flow channel, 5-Second stage impeller fluid domain, 6-Radial guide vane fluid domain, 61-Increased clearance of radial guide vane, 62-Radial guide vane positive blade flow channel, 7-Outlet section fluid domain. Detailed Implementation

[0048] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0049] This embodiment provides a design method for a two-stage cryogenic deep well pump. The two-stage cryogenic deep well pump includes an inducer wheel, a first-stage impeller, a spatial guide vane, a second-stage impeller, and radial guide vanes arranged from front to back on a rotating shaft. The inducer wheel includes a hub connected to the rotating shaft and inducer wheel blades connected to the hub. The spatial guide vane divides several flow channels through its own blades, and the radial guide vane contains only positive blades. Figure 1 This is a schematic diagram of the flow channel of a two-stage cryogenic deep well pump. From front to back, the flow channels are: inlet section fluid domain 1, inducer wheel fluid domain 2, first stage impeller fluid domain 3, space guide vane fluid domain 4, second stage impeller fluid domain 5, radial guide vane fluid domain 6, and outlet section fluid domain 7. Figure 2 This is a schematic diagram of the flow channel assembly between the inducer and the first-stage impeller of a two-stage cryogenic deep well pump. Figure 3 This is a schematic diagram of the flow channel assembly of the first-stage impeller and the space guide vanes of a two-stage cryogenic deep well pump. Figure 4 This is a schematic diagram of the flow channel assembly of the second-stage impeller and radial guide vanes of a two-stage cryogenic deep well pump. Through Boolean operations, a physical model of the two-stage cryogenic deep well pump assembly can be obtained based on the aforementioned fluid domain.

[0050] The design method includes the following steps:

[0051] S1. Design the inducer wheel; design the leading edge of the inducer wheel blades to be knife-point shaped, design the actual radius of the leading edge based on the maximum thickness of the inducer wheel, grind the back of the inducer wheel blade inlet to make the blade tip sharp, grind the inlet radius on the back of the inlet and the outlet radius on the working surface of the inducer wheel blade outlet, and grind the inlet length and outlet length of the inducer wheel based on the blade edge thickness; design the inlet and outlet edge shapes of the inducer wheel blades, the inducer wheel diameter, the inlet and outlet angles of the inducer wheel blades, and the number of inducer wheel blades.

[0052] Specifically, step S1 includes:

[0053] S101. To improve cavitation resistance, the leading edge of the inducer blade is knife-edge shaped, and the maximum thickness of the inducer is δ. max The actual radius of the leading edge is To reduce the cavitation number of the inducer blade cascade and improve its cavitation resistance, the back surface of the inducer blade inlet is ground to make the blade tip sharp. The inlet radius R1 of the ground inlet back surface is 0.1mm to 0.4mm, and the inlet length of the inducer is L1 = 8δ to 12δ. The outlet radius R2 of the working surface of the inducer blade outlet is ground to 0.2mm to 0.8mm, and the outlet length is L2 = 6δ to 8δ, where δ is the blade edge thickness.

[0054] R1 can take any value from 0.1mm to 0.4mm (inclusive), R2 can take any value from 0.2mm to 0.8mm (inclusive), L1 is 8 to 12 times the leaf edge thickness δ, and L2 is 6 to 8 times the leaf edge thickness δ.

[0055] Leaf edge thickness δ and maximum inducer thickness δ max The empirical values ​​are obtained through the rated parameters of a two-stage cryogenic deep well pump and empirical values. Empirical values ​​refer to initially setting a value based on experience, then using this initial value to calculate and build an assembly model for simulation optimization. After obtaining a slightly better optimized value, this process is repeated until a final value meeting the design requirements is obtained. The empirical values ​​discussed below follow the same principle.

[0056] S102. Determine the inlet and outlet edge shapes of the inducer blades: the outlet edge of the inducer is located on the same axial plane, and the sweep angle of the inducer is... It is the angle of rotation of the inlet edge radius in the opposite direction; the wrap angle of the inducer blade rim is... The hub wrap angle of the inducer blade is in, Such an inlet edge is also called the inlet rounding part. The inlet edge of the blade is swept back and rounded, which can improve the cavitation resistance by 10% to 25%. Even if primary cavitation occurs at the outer edge inlet, the cavitation bubble will be compressed, causing it to condense and not easily diffuse.

[0057] The sweep angle of the inducer is and the rim wrap angle of the inducer blades is The induced wheel blade hub wrap angle was obtained through the rated parameters of the two-stage cryogenic deep well pump and empirical values. pass Obtained through calculation.

[0058] S103. Determine the diameter of the inducer wheel: The inducer wheel is a cylindrical variable pitch inducer wheel, and the inlet diameter of the inducer wheel blades is... Inducer wheel hub diameter Where Q is the pump flow rate, n is the pump speed, and φ = 0.1 to 0.14.

[0059] The pump flow rate Q and pump speed n are the rated parameters of the two-stage cryogenic deep well pump, and φ can be any value between 0.1 and 0.14 (inclusive). It can be any value between 0.3 and 0.4 (inclusive).

[0060] S104. Determine the inlet and outlet angles of the inducer blades: Inlet angle β of the inducer blades y1 =β′ y1 +Δβ y1 Inducer blade exit angle β y2 =β′ y2 +Δβ y2 ; where β′ y1 Δβ is the angle between the rim inlet diameter and the fluid flow angle. y1 =0°~5°; β' y2 Δβ is the angle between the outlet diameter and the liquid flow angle. y2 =1°-3°.

[0061] Δβ y1 : can be any value between 0° and 0.5° (inclusive), Δβ y2 It can be any value between 1° and 3° (inclusive), β′ y1 and =β′ y2 + Obtained through the quota parameters of the two-stage cryogenic deep well pump and empirical values.

[0062] S105, such as Figure 5 As shown, the number of blades of the inducer wheel is determined to be 3, which can prevent alternating blade cavitation.

[0063] S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller is matched with the inducer; the design method of the second-stage impeller is the same as that of the first-stage impeller. The design method of the second-stage impeller being the same as that of the first-stage impeller means that the calculation methods are similar, but the values ​​of some dimensional parameters are different.

[0064] Specifically, step S2 includes:

[0065] S201, such as Figure 6 As shown, the number of blades of the first-stage impeller or the second-stage impeller is determined to be twice the number of blades of the inducer; that is, the number of blades of the first-stage impeller or the second-stage impeller is 6. During installation, the outlet edge of the inducer blades is staggered from the inlet edge of the first-stage impeller blades, which can increase the symmetry of the flow.

[0066] S202. Determine the inlet diameter of the first-stage or second-stage impeller.

[0067] in, k0 = 4.5~5.5, n is the pump speed, Q is the pump flow rate, d h The diameter of the induction wheel hub;

[0068] S203. Determine the outlet diameter of the first-stage impeller. Or the outlet diameter of the second-stage impeller

[0069] Where n is the pump speed and Q is the pump flow rate. k D3 =1.022~1.024, n s1 The specific speed of the first-stage impeller. H1 is the head of the first stage impeller; n s2 The specific speed of the second-stage impeller. H2 is the head of the second-stage impeller;

[0070] S204. Determine the outlet width of the first-stage impeller. Or the outlet width of the second-stage impeller

[0071] in, k b3 =1.078~1.055, n s1 The specific speed of the first-stage impeller in step S203; n s2 The specific speed of the second-stage impeller in step S203;

[0072] S205. Determine the inlet angle β1 and outlet angle β2 of the first-stage impeller; the blade inlet angle of attack Δβ = β1 - β1′ of the first-stage impeller, where the blade inlet angle of attack Δβ is the positive angle of attack and β1′ is the relative angle of liquid flow at the blade inlet; the outlet angle β2 = 22° to 30°.

[0073] In the above steps, k0 can be any value between 4.5 and 5.5 (inclusive), the pump flow rate Q and the pump speed n are the rated parameters of the two-stage cryogenic deep well pump, and the induced wheel hub diameter d... h The blade inlet angle of attack Δβ, the blade inlet relative fluid flow angle β1′, and the outlet placement angle β2 are calculated through step S103. These are obtained using the rated parameters and empirical values ​​of the two-stage cryogenic deep well pump. The inlet placement angle β1 of the first-stage impeller is calculated using Δβ = β1 - β1′. D3 k can be any value between 1.022 and 1.024 (inclusive). b2It can be any value between 1.078 and 1.055 (inclusive), where H is the head of the first-stage impeller H1, which is obtained from the rated parameters of the two-stage cryogenic deep well pump and empirical values. The head of the second-stage impeller H2 is calculated after obtaining the size parameters of the first-stage impeller, as detailed below.

[0074] The first-stage impeller and the second-stage impeller have different heads, thus causing the first-stage impeller n s1 The specific speed n of the second-stage impeller s2 The difference lies in the experience gained regarding the head H1 and k of the first-stage impeller. D2 By taking values, the specific speed n of the first-stage impeller can be calculated. s1 This allows us to calculate the k of the first-stage impeller. D1 And then through The outlet diameter D of the first-stage impeller was calculated. 2m .like Figure 6 As shown, the final flow channel 31 of the first-stage impeller and the cut section 32 at the outlet edge of the first-stage impeller together form the fluid domain 3 of the first-stage impeller. Because a head margin is reserved during the design of the first-stage and second-stage impellers, the outlets of the first-stage and second-stage impellers are cut when assembling the first-stage impeller with the spatial guide vanes, or the second-stage impeller with the radial guide vanes, respectively. After obtaining the outlet diameter of the first-stage impeller, the head H2 of the second-stage impeller is obtained according to the following calculation ratio: The head decreases proportionally to increase the clearance between the impeller and the guide vanes, thus obtaining the head H2 of the second-stage impeller, which allows for the calculation of the specific speed n of the second-stage impeller. s2 This allows us to calculate the k of the second-stage impeller. D2 And then through The outlet diameter D of the second-stage impeller was calculated. 2n .

[0075] S3. Design the spatial guide vane; the spatial guide vane is matched with the first-stage impeller.

[0076] Specifically, step S3 includes:

[0077] S301. Determine the axial distance between the inlet edge of the space guide vane and the rear cover plate at the outlet edge of the first-stage impeller as ΔL = 1.5b. 2m , where b 2m This refers to the outlet width of the first-stage impeller in step S204. Generally, it is better for the inlet edge of the spatial guide vane to be slightly farther from the outlet edge of the first-stage impeller. The first-stage impeller is the impeller cut in step S203, which increases the gap 41 between the first-stage impeller and the spatial guide vane. The increased gap 41 of the spatial guide vane and the designed flow channel 42 of the spatial guide vane together form the fluid domain 4 of the spatial guide vane. Figure 7 As shown.

[0078] S302. Determine that the number of blades of the space guide vane is twice the number of blades of the first-stage impeller minus one, that is, the number of blades of the space guide vane is 11.

[0079] S303. Determine the axial length L3 of the spatial guide vane as 0.5D. 2m ~0.7D 2m , where D 2m L3 is the outlet diameter of the first-stage impeller in step S203; that is: L3 is the outlet diameter D of the first-stage impeller. 2m 0.5 to 0.7 times.

[0080] S304. Determine the blade wrap angle of the spatial guide vane. Right now: It can take any value from 60° to 95° (inclusive).

[0081] S4. Design the radial guide vane; the radial guide vane is matched with the secondary impeller.

[0082] Specifically, step S4 includes:

[0083] Step S401: Determine that the number of blades of the radial guide vane is 9.

[0084] Step S402: Determine the base circle diameter D3 of the radial guide vane. 2n +2mm≤D3≤D 2n +10mm, where D 2n The outlet diameter of the second-stage impeller in step S203; that is: the radial guide vane base circle diameter D3 is greater than the outlet diameter D of the second-stage impeller. 2n The size ranges from 2mm to 10mm.

[0085] Step S403: Determine the inlet width b3 of the radial guide vane positive blade. 2n +2mm≤b3≤b 2n +5mm, where b 2n The outlet width of the second-stage impeller in step S204; that is: the inlet width b3 of the radial guide vane positive blade is greater than the outlet diameter b of the second-stage impeller. 2n Larger by 2mm to 5mm.

[0086] Step S404: Determine the length L4 of the diffuser section of the radial guide vane positive blade = 2.4b3; b3 is the inlet width of the radial guide vane positive blade in step S403.

[0087] Step S405: Determine the exit width b4 of the radial guide vane positive blade = b3 + 12 mm; b3 is the inlet width of the radial guide vane positive blade in step S403. That is, the exit width b4 of the radial guide vane positive blade is 12 mm larger than the inlet width b3 of the radial guide vane positive blade.

[0088] By increasing the base circle diameter of the radial guide vane, the inlet width of the radial guide vane's positive blade, the length of the diffuser section of the radial guide vane's positive blade, and the outlet width of the radial guide vane's positive blade based on the second-stage impeller, the clearance between the radial guide vane and the second-stage impeller can be increased. The increased clearance 61 of the radial guide vane and the flow channel 62 of the radial guide vane's positive blade together form the radial guide vane fluid domain 6, such as... Figure 8 As shown.

[0089] The two-stage cryogenic deep well pump design method in this embodiment can be used to design high-efficiency two-stage LNG cryogenic deep well pumps. By improving the shape and size parameters of the inducer, cavitation resistance can be guaranteed. Furthermore, based on the inducer's size parameters, a matching first-stage impeller is designed, followed by spatial guide vanes, a second-stage impeller, and radial guide vanes. The radial guide vanes only include positive guide vanes to facilitate connection with the subsequent outflow section and reduce local hydraulic losses. When hydraulically designing the first and second-stage impellers, a head margin is retained to facilitate subsequent impeller cutting. During the assembly of the first-stage impeller with the spatial guide vanes and the second-stage impeller with the radial guide vanes, the first and second-stage impellers are cut to increase the assembly gap between the first and second-stage impellers and the corresponding guide vanes, enlarging the transition section and improving the hydraulic efficiency of the assembled flow components.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A design method for a two-stage cryogenic deep well pump, characterized in that: The two-stage cryogenic deep well pump includes an inducer wheel, a first-stage impeller, a spatial guide vane, a second-stage impeller, and radial guide vanes arranged from front to back on a rotating shaft; the inducer wheel includes a hub connected to the rotating shaft and inducer wheel blades connected to the hub, the spatial guide vane divides several flow channels through its own blades, and the radial guide vane contains only positive blades; The design method includes the following steps: S1. Design the inducer wheel; design the leading edge of the inducer wheel blades to be knife-edge shaped, design the actual radius of the leading edge based on the maximum thickness of the inducer wheel, grind the back of the inducer wheel blade inlet to make the blade tip sharp, grind the inlet radius on the back of the inlet and the outlet radius on the working surface of the inducer wheel blade outlet, and grind the inlet length and outlet length of the inducer wheel based on the blade edge thickness; design the inlet and outlet edge shapes of the inducer wheel blades, the inducer wheel diameter, the inlet and outlet angles of the inducer wheel blades, and the number of inducer wheel blades; S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller is matched with the inducer; the design method of the second-stage impeller is the same as that of the first-stage impeller; S3. Design the spatial guide vane; the spatial guide vane is matched with the first-stage impeller; S4. Design the radial guide vane; the radial guide vane is matched with the secondary impeller; Step S1 includes: S101, The leading edge of the inducer blade is knife-edge shaped, and the maximum thickness of the inducer is δ. max The actual radius of the leading edge is The back surface of the inlet of the inducer blade is ground to make the blade tip sharp. The inlet radius R1 of the back surface of the inlet is ground to be 0.1mm to 0.4mm, and the inlet length of the inducer is ground to be L1 to 8δ to 12δ. The outlet radius R2 of the outlet working surface of the inducer blade is ground to be 0.2mm to 0.8mm, and the outlet length is ground to be L2 to 6δ to 8δ, where δ is the blade edge thickness. S102. Determine the inlet and outlet edge shapes of the inducer blades: the outlet edge of the inducer is located on the same axial plane, and the sweep angle of the inducer is... It is the angle of rotation of the inlet edge radius in the opposite direction; the wrap angle of the inducer blade rim is... The hub wrap angle of the inducer blade is in, S103. Determine the diameter of the inducer wheel: The inducer wheel is a cylindrical variable pitch inducer wheel, and the inlet diameter of the inducer wheel blades is... Inducer wheel hub diameter Where Q is the pump flow rate, n is the pump speed, and φ = 0.1 to 0.

14. S104. Determine the inlet and outlet angles of the inducer blades: Inlet angle β of the inducer blades y1 =β′ y1 +Δβ y1 Inducer blade exit angle β y2 =β′ y2 +Δβ y2 ; where β′ y1 Δβ is the angle between the rim inlet diameter and the fluid flow angle. y1 =0°~5°; β' y2 Δβ is the angle between the outlet diameter and the liquid flow angle. y2 =1°-3°; S105. Determine that the number of blades of the inducer wheel is 3.

2. The design method for a two-stage cryogenic deep well pump according to claim 1, characterized in that, Step S2 includes: S201. Determine that the number of blades of the first-stage impeller or the second-stage impeller is twice the number of blades of the inducer wheel; S202. Determine the inlet diameter of the first-stage or second-stage impeller. in, k0 = 4.5~5.5, n is the pump speed, Q is the pump flow rate, d h The diameter of the induction wheel hub; S203. Determine the outlet diameter of the first-stage impeller. Or the outlet diameter of the second-stage impeller Where n is the pump speed and Q is the pump flow rate. k D3 =1.022~1.024, n s1 The specific speed of the first-stage impeller. H1 is the head of the first stage impeller; n s2 The specific speed of the second-stage impeller. H2 is the head of the second-stage impeller; S204. Determine the outlet width of the first-stage impeller. Or the outlet width of the second-stage impeller in, k b3 =1.078~1.055, n s1 The specific speed of the first-stage impeller in step S203; n s2 The specific speed of the second-stage impeller in step S203; S205. Determine the inlet angle β1 and outlet angle β2 of the first-stage impeller; the blade inlet angle of attack Δβ = β1 - β1′ of the first-stage impeller, where the blade inlet angle of attack Δβ is the positive angle of attack and β1′ is the relative angle of liquid flow at the blade inlet; the outlet angle β2 = 22° to 30°.

3. The design method for a two-stage cryogenic deep well pump according to claim 2, characterized in that, Step S3 includes: S301. Determine the axial distance between the inlet edge of the space guide vane and the rear cover plate at the outlet edge of the first-stage impeller as ΔL = 1.5b. 2m , where b 2m The outlet width of the first-stage impeller in step S204; S302. Determine that the number of blades of the spatial guide vane is twice the number of blades of the first-stage impeller minus one. S303. Determine the axial length L3 of the spatial guide vane as 0.5D. 2m ~0.7D 2m , where D 2m The outlet diameter of the first-stage impeller in step S203; S304. Determine the blade wrap angle of the spatial guide vane.

4. The design method for a two-stage cryogenic deep well pump according to claim 2, characterized in that, Step S4 includes: Step S401: Determine that the number of blades of the radial guide vane is 9; Step S402: Determine the base circle diameter D3 of the radial guide vane. 2n +2mm≤D3≤D 2n +10mm, where D 2n The outlet diameter of the secondary impeller in step S203; Step S403: Determine the inlet width b3 of the radial guide vane positive blade. 2n +2mm≤b3≤b 2n +5mm, where b 2n The outlet width of the secondary impeller in step S204; Step S404: Determine the length L4 of the diffuser section of the radial guide vane positive blade = 2.4b3; Step S405: Determine the exit width b4 of the radial guide vane positive blade as b3 + 12 mm.

Images