Design method of two-stage low-temperature deep-well pump

Abstract

The invention discloses a design method of a two-stage low-temperature deep-well pump. The two-stage low-temperature deep-well pump comprises an inducer, a first-stage impeller, a space guide vane, a second-stage impeller and a radial guide vane which are arranged on a rotating shaft from front to back. The inducer comprises a hub connected with the rotating shaft and inducer blades connected with the hub, the space guide blades are divided into a plurality of flow channels through the blades of the space guide blades, and the radial guide blades only comprise positive blades; the design method comprises the following steps that S1, the inducer is designed; s2, designing a first-stage impeller and a second-stage impeller; s3, designing the space guide vane; and S4, the radial guide blade is designed. The method can be used for designing the high-efficiency two-stage LNG low-temperature deep-well pump, the cavitation resistance can be guaranteed by improving the shape and size parameters of the inducer, the matched first-stage impeller is designed with the size parameters of the inducer as the standard, then the space guide vane, the second-stage impeller and the radial guide vane are designed, and the hydraulic efficiency of the designed product is high.

Description

Technical Field

[0001] The invention relates to the technical field of liquid transportation, and in particular to a design method for a two-stage low-temperature deep well pump. Background Art

[0002] The cryogenic deep well pump is a unique centrifugal pump structure, specially used for handling cryogenic fluids, liquefied natural gas (LNG), liquefied petroleum gas (LPG), liquid ethylene, propylene, ethane and various other cryogenic liquids. As one of the clean energy sources currently recognized by the world, LNG has become a rapidly developing emerging industry in my country's energy field, and its demand is increasing worldwide. The cryogenic pump is a key equipment in the transportation process of the LNG receiving station. It is mainly used for the loading, unloading, transportation and pressurization of LNG. The cryogenic pump for transporting LNG must not only meet the requirements of general cryogenic liquid pumps, but also have high requirements for the sealing performance and explosion-proof performance of the pump. Submersible electric pumps are generally used for LNG transportation in domestic and foreign receiving stations. It is a centrifugal liquid pump that is practical in low temperature environments, and its impeller works below the liquid surface.

[0003] Marine deep well pumps are cargo pumps commonly used on small liquefied petroleum gas (LPG) ships. They 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 placed on the top deck of the tank, and the pump body is placed in the suction well at the bottom of the liquid cargo tank. The drive motor is an explosion-proof motor, which is installed on the top outside the blade bin, and the transmission shaft is supported by the intermediate guide bearing in the drainage vertical pipe. At present, marine deep well pumps can also be used for main engine supply, and have a wide range of uses.

[0004] At present, the research on ultra-low temperature deep well pumps in China is limited to the research on water media, which are widely used in rivers, reservoirs, farmland irrigation, water supply and drainage of industrial and mining enterprises, water for people and livestock in plateaus and mountainous areas, and oil field exploitation. There are no relevant research reports on ultra-low temperature media such as LNG and LPG.

[0005] Most cryogenic pumps for large LNG ships and LNG storage tanks are multi-stage centrifugal pumps, which are fully immersed. Their main components include: guide, motor, diffuser, impeller, main shaft, bearing, vibration detector, thrust equalizing mechanism (TEM), etc. The difficulty in the development of LNG pump technology is that since the pump is immersed in 111K LNG liquid, its motor, claws, impeller and lead cable must also withstand low temperature; and during the transportation process, LNG is near the saturation temperature, and even a small temperature will cause LNG to vaporize, which may cause "cavitation" to affect the pump's transportation performance. Therefore, the existing LNG cryogenic deep well pumps have low efficiency. At present, the overall research and development goal of domestic LNG submersible pumps is to develop pumps with strong anti-cavitation performance and high hydraulic efficiency suitable for the physical properties of LNG. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a two-stage cryogenic deep well pump design method, which can be used to design a high-efficiency two-stage LNG cryogenic deep well pump, and by improving the shape and size parameters of the inducer, the anti-cavitation performance can be guaranteed. Moreover, based on the size parameters of the inducer, a matching first-stage impeller is designed, and then the space guide vanes, the second-stage impeller and the radial guide vanes are designed, and the hydraulic efficiency of the designed product is high.

[0007] A design method for a two-stage cryogenic deep well pump in the present invention comprises an inducer, a first-stage impeller, a space guide vane, a second-stage impeller and a radial guide vane arranged on a rotating shaft from front to back; the inducer comprises a hub connected to the rotating shaft and inducer blades connected to the hub, the space guide vane divides a plurality of flow channels through its own blades, and the radial guide vane only contains positive blades;

[0008] The design method comprises the following steps:

[0009] S1. Design the inducer; design the leading edge of the inducer blade to be tip-shaped, design the actual leading edge radius based on the maximum thickness of the inducer, grind the inlet back of the inducer blade to make the blade tip sharp, grind the inlet fillet of the inlet back and the outlet fillet of the outlet working surface of the inducer blade, and grind the inlet length and outlet length of the inducer based on the blade edge thickness; design the outlet edge shape of the inducer blade, the inducer diameter size, the inlet and outlet angles of the inducer blade, and the number of inducer blades;

[0010] S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller is matched with the inducer; the second-stage impeller is designed in the same manner as the first-stage impeller;

[0011] S3. Designing the space guide vane; the space guide vane matches the first-stage impeller;

[0012] S4. Design the radial guide vanes; the radial guide vanes are matched with the secondary impeller.

[0013] Further, the step S1 comprises:

[0014] S101, the leading edge of the inducer blade is tip-shaped, and the maximum thickness of the inducer is δ max , the actual radius of the leading edge is Grind the inlet back side of the inducer blade to make its blade tip sharp, grind the inlet fillet R1 of the inlet back side to be 0.1mm-0.4mm, and grind the inlet length L1 of the inducer to be 8δ-12δ; grind the outlet fillet R2 of the outlet working surface of the inducer blade to be 0.2mm-0.8mm, and grind the outlet length L2 to be 6δ-8δ, where δ is the blade edge thickness;

[0015] S102, determine the inlet and outlet edge shapes of the inducer blades: the outlet edges of the inducer blades are located on the same axial plane, and the inducer blade sweep angle is is the angle at which the radius of the inlet edge rotates in the opposite direction; the rim wrap angle of the inducer blade is The hub wrap angle of the inducer blade is in,

[0016] S103, determine the diameter size of the inducer: the inducer is a cylindrical variable pitch inducer, the inlet diameter of the inducer blade Inducer hub diameter Where Q is the flow rate of the pump, n is the speed of the pump, φ = 0.1 ~ 0.14,

[0017]

[0018] S104. Determine the inlet and outlet angles of the inducer blades: the inlet angle of the inducer blades β y1 =β y ′1+Δβ y1 , inducer blade outlet angle β y2 =β y ′2+Δβ y2 ; Among them, β y ′1 is the relative flow angle of the rim inlet diameter, Δβ y1 =0°~5°; =β y ′2+ is the relative flow angle of the outlet diameter, Δβ y1 =1°~3°;

[0019] S105. Determine that the number of blades of the inducer is 3.

[0020] Further, the step S2 comprises:

[0021] S201, determining that the number of blades of the first-stage impeller or the second-stage impeller is twice the number of blades of the inducer;

[0022] S202. Determine the inlet diameter of the first-stage impeller or the second-stage impeller

[0023] in, k0 = 4.5 ~ 5.5, Q is the flow rate of the pump, d h is the inducer hub diameter;

[0024] 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, Q is the pump flow rate, k D3 =1.022~1.024, n s1 is the specific speed of the first-stage impeller, H1 is the head of the first-stage impeller; n s2 is the specific speed of the secondary impeller, H2 is the head of the secondary impeller;

[0025] S204, determine the outlet width of the first-stage impeller Or the outlet width of the second-stage impeller

[0026] in, k b3 =1.078~1.055,n s1 is the specific speed of the first-stage impeller in step S203; n s2 is the specific speed of the secondary impeller in step S203;

[0027] S205. Determine the inlet angle β1 and outlet angle β2 of the first-stage impeller; the blade inlet angle of attack Δβ of the first-stage impeller is Δβ=β1-β1′, wherein the blade inlet angle of attack Δβ is the positive angle of attack, and β1′ is the relative liquid flow angle of the blade inlet; the outlet angle β2 is 22°~30°.

[0028] Further, the step S3 comprises:

[0029] S301, determine the axial distance between the blade 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 is the outlet width of the first-stage impeller in step S204;

[0030] S302, determining that the number of blades of the spatial guide vane is twice the number of blades of the first-stage impeller minus one;

[0031] S303, determine the axial length of the space guide vane L3 = 0.5D 2m ~0.7D 2m , where D 2m is the outlet diameter of the first-stage impeller in step S203;

[0032] S304: Determine the blade wrap angle of the spatial guide vane

[0033] Further, the step S4 comprises:

[0034] Step S401, determining that the number of blades of the radial guide vane is 9;

[0035] Step S402: Determine the radial guide vane base circle diameter D3, D 2n +2mm≤D3≤D 2n +10mm, where D 2n is the outlet diameter of the secondary impeller in step S203;

[0036] Step S403: Determine the radial guide vane positive blade inlet width b3, b 2n +2mm≤b3≤b 2n +5mm, where b 2n is the outlet width of the secondary impeller in step S204;

[0037] Step S404, determining the radial guide vane positive blade diffusion section length L4 = 2.4b3;

[0038] Step S405, determine the radial guide vane positive blade outlet width b4 = b3 + 12 mm.

[0039] The beneficial effects of the present invention are as follows: the present invention can be used to design a high-efficiency two-stage LNG cryogenic deep well pump, and can ensure anti-cavitation performance by improving the shape and size parameters of the inducer. Moreover, based on the size parameters of the inducer, a matching first-stage impeller is designed, and then a space guide vane, a second-stage impeller and a radial guide vane are designed, and the radial guide vane only includes positive blades, so as to facilitate connection with the subsequent outflow section and reduce local hydraulic losses; when the first-stage and second-stage impellers are hydraulically designed, a head margin is reserved to facilitate subsequent cutting of the impeller; when the first-stage impeller is assembled with the space guide vane and the second-stage impeller is assembled with the radial guide vane, the first-stage and second-stage impellers are cut to increase the assembly gap between the first-stage and second-stage impellers and the corresponding guide vanes, increase the transition section, and improve the hydraulic efficiency of the flow-through components after assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0041] Figure 1 It is a schematic diagram of the flow path of the two-stage cryogenic deep well pump of the present invention;

[0042] Figure 2 It is a schematic diagram of the flow passage of the two-stage cryogenic deep well pump of the present invention in which the inducer and the first-stage impeller are assembled;

[0043] Figure 3 It is a schematic diagram of the flow passage of the first-stage impeller and the space guide vane assembly of the two-stage cryogenic deep well pump of the present invention;

[0044] Figure 4 It is a schematic diagram of the flow passage of the second-stage impeller and radial guide vane assembly of the two-stage cryogenic deep well pump of the present invention;

[0045] Figure 5 It is a schematic diagram of the flow passage of the inducer of the two-stage cryogenic deep well pump of the present invention;

[0046] Figure 6 It is a schematic diagram of the flow passage of the first-stage impeller of the two-stage cryogenic deep well pump of the present invention;

[0047] Figure 7 It is a schematic diagram of the flow passage of the space guide vane of the two-stage cryogenic deep well pump of the present invention;

[0048] Figure 8 It is a schematic diagram of the flow passage of the radial guide vanes of the two-stage cryogenic deep well pump of the present invention.

[0049] The markings in the accompanying drawings are as follows: 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 cutting section, 4-space guide vane fluid domain, 41-increased gap of space guide vane, 42-space guide vane design flow channel, 5-secondary impeller fluid domain, 6-radial guide vane fluid domain, 61-increased gap of radial guide vane, radial guide vane positive blade flow channel 62, 7-outlet section fluid domain. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0051] A two-stage cryogenic deep well pump design method is provided in this embodiment, wherein the two-stage cryogenic deep well pump comprises an inducer, a first-stage impeller, a spatial guide vane, a second-stage impeller and a radial guide vane arranged on a rotating shaft from front to back; the inducer comprises a hub connected to the rotating shaft and inducer blades connected to the hub, the spatial guide vane divides a plurality of flow channels by its own blades, and the radial guide vane contains only positive blades. Figure 1It is a schematic diagram of the flow path of a two-stage cryogenic deep well pump, which includes, from front to back, the inlet section fluid domain 1, the inducer fluid domain 2, the first-stage impeller fluid domain 3, the spatial guide vane fluid domain 4, the second-stage impeller fluid domain 5, the radial guide vane fluid domain 6 and the outlet section fluid domain 7. Figure 2 It is a schematic diagram of the flow passage of the inducer and the first-stage impeller of a two-stage cryogenic deep well pump; Figure 3 It is a schematic diagram of the flow passage of the first-stage impeller and the space guide vane assembly of a two-stage cryogenic deep well pump; Figure 4 It is a schematic diagram of the flow path of the secondary impeller and radial guide vane assembly of the two-stage cryogenic deep well pump. Through Boolean operation, the physical model of the assembly of the two-stage cryogenic deep well pump can be obtained according to the above fluid domain.

[0052] The design method comprises the following steps:

[0053] S1. Design the inducer; design the leading edge of the inducer blade to be tip-shaped, design the actual leading edge radius based on the maximum thickness of the inducer, grind the inlet back side of the inducer blade to make the blade tip sharp, grind the inlet fillet of the inlet back side and the outlet fillet of the outlet working surface of the inducer blade, and grind the inlet length and outlet length of the inducer based on the blade edge thickness; design the outlet edge shape of the inducer blade, the inducer diameter size, the inlet and outlet angles of the inducer blade, and the number of inducer blades.

[0054] Specifically, the step S1 includes:

[0055] S101. To improve the cavitation resistance, the leading edge of the inducer blade is tip-shaped, and the maximum thickness of the inducer is δ max , the actual radius of the leading edge is In order to reduce the cavitation number of the inducer blade cascade and improve the anti-cavitation performance, the inlet back side of the inducer blade is polished to make the blade tip sharp, the inlet fillet R1 of the inlet back side is polished to be 0.1mm~0.4mm, and the inlet length L1 of the inducer is polished to be 8δ~12δ; the outlet fillet R2 of the outlet working surface of the inducer blade is polished to be 0.2mm~0.8mm, and the outlet length L2 is polished to be 6δ~8δ, where δ is the blade edge thickness.

[0056] R1 can take any value from 0.1mm to 0.4mm (including 0.1mm and 0.4mm), R2 can take any value from 0.2mm to 0.8mm (including 0.2mm and 0.8mm), L1 is 8 to 12 times the leaf edge thickness δ, and L2 is 6 to 8 times the leaf edge thickness δ.

[0057] Blade edge thickness δ and inducer maximum thickness δ maxIt is obtained through the rated parameters and empirical values ​​of the two-stage cryogenic deep well pump. The empirical value refers to setting an initial value artificially based on experience, calculating with the initial value and establishing the assembly object model for simulation optimization, obtaining the optimized optimal value, calculating with the optimal value and establishing the assembly object model for simulation optimization again, and iterating repeatedly until the final value that meets the design requirements is obtained. The empirical value below is the same as this principle.

[0058] S102, determine the inlet and outlet edge shapes of the inducer blades: the outlet edges of the inducer blades are located on the same axial plane, and the inducer blade sweep angle is is the angle at which the radius of the inlet edge rotates in the opposite direction; the rim wrap angle of the inducer blade is The hub wrap angle of the inducer blade is in, Such an inlet edge is also called the inlet rounded part. The swept-back rounded inlet edge of the blade can improve the cavitation resistance by 10% to 25%. Even if primary cavitation occurs at the outer edge inlet, the cavitation will be compressed, causing condensation and difficulty in diffusion.

[0059] The inducer sweep angle is And the inducer blade rim angle is The hub angle of the inducer blade is obtained through the rated parameters and experience of the two-stage cryogenic deep well pump. pass Obtained by calculation.

[0060] S103, determine the diameter size of the inducer: the inducer is a cylindrical variable pitch inducer, the inlet diameter of the inducer blade Inducer hub diameter Where Q is the flow rate of the pump, n is the speed of the pump, φ = 0.1 ~ 0.14,

[0061] The pump flow rate Q and the 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 (including 0.1 and 0.14). It can be any value between 0.3 and 0.4 (inclusive).

[0062] S104. Determine the inlet and outlet angles of the inducer blades: the inlet angle of the inducer blades β y1 =β′ y1 +Δβ y1 , inducer blade outlet angle β y2 =β′ y2 +Δβ y2 ; where β′ y1 is the relative flow angle of the rim inlet diameter, Δβ y1 =0°~5°; β′y2 is the outlet diameter relative to the liquid flow angle, Δβ y1 =1°~3°.

[0063] Δβ y1 It can be any value between 0° and 0.5° (including 0° and 0.5°), Δβ y1 It can be any value between 1° and 3° (inclusive), β′ y1 and β′ y2 Obtained through the rated parameters and experience values ​​of the two-stage cryogenic deep well pump.

[0064] S105, such as Figure 5 As shown, determining the number of blades of the inducer to be 3 can prevent alternating blade cavitation.

[0065] S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller matches the inducer; the second-stage impeller is designed in the same way as the first-stage impeller. The second-stage impeller and the first-stage impeller are designed in the same way, which means that the calculation method is similar but the values ​​of some size parameters are different.

[0066] Specifically, step S2 includes:

[0067] 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 blade is staggered with the inlet edge of the first-stage impeller blade, which can increase the symmetry of the flow.

[0068] S202. Determine the inlet diameter of the first-stage impeller or the second-stage impeller

[0069] Among them, among them, k0 = 4.5 ~ 5.5, Q is the flow rate of the pump, d h is the inducer hub diameter;

[0070] S203, determine the outlet diameter of the first-stage impeller Or the outlet diameter of the second-stage impeller

[0071] Where n is the pump speed, Q is the pump flow rate, k D3 =1.022~1.024, n s1 is the specific speed of the first-stage impeller, H1 is the head of the first-stage impeller; n s2 is the specific speed of the secondary impeller, H2 is the head of the secondary impeller;

[0072] S204, determine the outlet width of the first-stage impeller Or the outlet width of the second-stage impeller

[0073] in, k b3 =1.078~1.055,n s1 is the specific speed of the first-stage impeller in step S203; n s2 is the specific speed of the secondary impeller in step S203;

[0074] S205. Determine the inlet angle β1 and outlet angle β2 of the first-stage impeller; the blade inlet angle of attack Δβ of the first-stage impeller is Δβ=β1-β1′, wherein the blade inlet angle of attack Δβ is the positive angle of attack, and β1′ is the relative liquid flow angle of the blade inlet; the outlet angle β2 is 22°~30°.

[0075] In the above steps, k0 can be any value between 4.5 and 5.5 (including 4.5 and 5.5), the pump flow Q and the pump speed n are the rated parameters of the two-stage low-temperature deep well pump, and the inducer hub diameter d h The blade inlet angle of attack Δβ, the blade inlet relative flow angle β1′ and the outlet placement angle β2 are obtained through the rated parameters and empirical values ​​of the two-stage cryogenic deep well pump, and the inlet placement angle β1 of the first-stage impeller is calculated by Δβ=β1-β1′. D3 Can be any value between 1.022 and 1.024 (inclusive), k b2 It can be any value between 1.078 and 1.055 (including 1.078 and 1.055). H is the head H1 of the first-stage impeller. H1 is obtained through the rated parameters and empirical values ​​of the two-stage cryogenic deep well pump. The head H2 of the second-stage impeller is calculated after obtaining the size parameters of the first-stage impeller. See below for details.

[0076] The lift of the first-stage impeller and the second-stage impeller is different, so the first-stage impeller n s1 and the specific speed n of the secondary impeller s2 Different, through experience, 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 , so that the k of the first-stage impeller can be calculated D1 , and then through Calculate the outlet diameter D of the first-stage impeller 2m .like Figure 6As shown, the first-stage impeller final flow channel 31 and the first-stage impeller outlet edge cutting section 32 together form the first-stage impeller fluid domain 3. Because head margin is reserved when designing the first-stage impeller and the second-stage impeller, when the first-stage impeller is assembled with the space guide vane, or the second-stage impeller is assembled with the radial guide vane, the first-stage impeller outlet and the second-stage impeller outlet are cut respectively, and 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 according to the ratio to increase the gap between the impeller and the guide vane, and the head H2 of the secondary impeller can be obtained, so that the specific speed n of the secondary impeller can be calculated. s2 , so that the k of the secondary impeller can be calculated D2 , and then through The outlet diameter D of the second-stage impeller is calculated 2n .

[0077] S3. Design the space guide vane; the space guide vane is matched with the first-stage impeller.

[0078] Specifically, step S3 includes:

[0079] S301, determine the axial distance between the blade 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 is the outlet width of the first-stage impeller in step S204; in general, it is better that the inlet edge of the spatial guide vane is slightly farther away from the outlet edge of the first-stage impeller. The first-stage impeller is the impeller cut in step S203, and the gap 41 between the first-stage impeller and the spatial guide vane is increased. The increased gap 41 of the spatial guide vane and the designed flow channel 42 of the spatial guide vane together form a spatial guide vane fluid domain 4, such as Figure 7 shown.

[0080] 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, that is, the number of blades of the spatial guide vane is 11.

[0081] S303, determine the axial length of the space guide vane L3 = 0.5D 2m ~0.7D 2m , where D 2m 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.

[0082] S304: Determine the blade wrap angle of the spatial guide vane Right now: It can take any value between 60° and 95° (including 60° and 95°).

[0083] S4. Design the radial guide vanes; the radial guide vanes are matched with the secondary impeller.

[0084] Specifically, step S4 includes:

[0085] Step S401, determining that the number of blades of the radial guide vane is 9.

[0086] Step S402: Determine the radial guide vane base circle diameter D3, D 2n +2mm≤D3≤D 2n +10mm, where D 2n is the outlet diameter of the secondary impeller in step S203; that is, the radial guide vane base circle diameter D3 is greater than the outlet diameter D 2n 2mm to 10mm larger.

[0087] Step S403: Determine the radial guide vane positive blade inlet width b3, b 2n +2mm≤b3≤b 2n +5mm, where b 2n is the outlet width of the secondary impeller in step S204; that is, the radial guide vane positive blade inlet width b3 is greater than the outlet diameter b of the secondary impeller. 2n 2mm to 5mm larger.

[0088] Step S404, determine the radial guide vane positive blade diffusion section length L4 = 2.4b3; b3 is the radial guide vane positive blade inlet width in step S403.

[0089] Step S405, determine the radial guide vane positive blade outlet width b4 = b3 + 12mm; b3 is the radial guide vane positive blade inlet width in step S403. That is, the radial guide vane positive blade outlet width b4 is 12mm larger than the radial guide vane positive blade inlet width b3.

[0090] By increasing the radial guide vane base circle diameter, the radial guide vane positive blade inlet width, the radial guide vane positive blade diffusion section length and the radial guide vane positive blade outlet width on the basis of the secondary impeller, it is possible to ensure that the gap between the radial guide vane and the secondary impeller is increased, and the increased gap 61 of the radial guide vane and the radial guide vane positive blade flow channel 62 together form a radial guide vane fluid domain 6, as shown in FIG. Figure 8 shown.

[0091] The two-stage cryogenic deep well pump design method in this embodiment can be used to design a high-efficiency two-stage LNG cryogenic deep well pump, and can ensure anti-cavitation performance by improving the shape and size parameters of the inducer. In addition, based on the size parameters of the inducer, a matching first-stage impeller is designed, and then the space guide vanes, the second-stage impeller and the radial guide vanes are designed, and the radial guide vanes only include positive guide vanes, so as to facilitate connection with the subsequent outflow section and reduce local hydraulic losses; when the first-stage and second-stage impellers are hydraulically designed, a head margin is reserved to facilitate subsequent cutting of the impeller; when the first-stage impeller is assembled with the space guide vanes and the second-stage impeller is assembled with the radial guide vanes, the first-stage and second-stage impellers are cut to increase the assembly gap between the first-stage and second-stage impellers and the corresponding guide vanes, increase the transition section, and improve the hydraulic efficiency of the flow-through components after assembly.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A two-stage cryogenic deep well pump design method, characterized in that: The two-stage cryogenic deep well pump comprises an inducer, a first-stage impeller, a space guide vane, a second-stage impeller and a radial guide vane arranged on the rotating shaft from front to back; the inducer comprises a hub connected to the rotating shaft and inducer blades connected to the hub, the space guide vane divides a plurality of flow channels through its own blades, and the radial guide vane only contains positive blades; The design method comprises the following steps: S1. Design the inducer; design the leading edge of the inducer blade to be tip-shaped, design the actual leading edge radius based on the maximum thickness of the inducer, grind the inlet back of the inducer blade to make the blade tip sharp, grind the inlet fillet of the inlet back and the outlet fillet of the outlet working surface of the inducer blade, and grind the inlet length and outlet length of the inducer based on the blade edge thickness; design the outlet edge shape of the inducer blade, the inducer diameter size, the inlet and outlet angles of the inducer blade, and the number of inducer blades; S2. Design the first-stage impeller and the second-stage impeller; the first-stage impeller is matched with the inducer; the second-stage impeller is designed in the same manner as the first-stage impeller; S3. Designing the space guide vane; the space guide vane matches the first-stage impeller; S4. Design the radial guide vanes; the radial guide vanes are matched with the secondary impeller.

2. The two-stage cryogenic deep well pump design method according to claim 1 is characterized in that: The step S1 comprises: S101, the leading edge of the inducer blade is tip-shaped, and the maximum thickness of the inducer is δ max , the actual radius of the leading edge is Grind the inlet back side of the inducer blade to make its blade tip sharp, grind the inlet fillet R1 of the inlet back side to be 0.1mm-0.4mm, and grind the inlet length L1 of the inducer to be 8δ-12δ; grind the outlet fillet R2 of the outlet working surface of the inducer blade to be 0.2mm-0.8mm, and grind the outlet length L2 to be 6δ-8δ, where δ is the blade edge thickness; S102, determine the inlet and outlet edge shapes of the inducer blades: the outlet edges of the inducer blades are located on the same axial plane, and the inducer blade sweep angle is is the angle at which the radius of the inlet edge rotates in the opposite direction; the rim wrap angle of the inducer blade is The hub wrap angle of the inducer blade is in, S103, determine the diameter size of the inducer: the inducer is a cylindrical variable pitch inducer, the inlet diameter of the inducer blade Inducer hub diameter Where Q is the flow rate of the pump, n is the speed of the pump, (φ=0.1~0.14, S104. Determine the inlet and outlet angles of the inducer blades: the inlet angle of the inducer blades β y1 =β y ′1+Δβ y1 , inducer blade outlet angle β y2 =β y ′2+Δβ y2 ; Among them, β y ′1 is the relative flow angle of the rim inlet diameter, Δβ y1 =0°~5°; =β y ′2+ is the angle of the outlet diameter relative to the liquid flow, Δβ y1 =1°~3°; S105. Determine that the number of blades of the inducer is 3.

3. The two-stage cryogenic deep well pump design method according to claim 2 is characterized in that: The step S2 comprises: S201, determining that the number of blades of the first-stage impeller or the second-stage impeller is twice the number of blades of the inducer; S202. Determine the inlet diameter of the first-stage impeller or the second-stage impeller in, k0 = 4.5 ~ 5.5, Q is the flow rate of the pump, d h is the inducer hub diameter; 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, Q is the pump flow rate, k D3 =1.022~1.024, n s1 is the specific speed of the first-stage impeller, H1 is the head of the first-stage impeller; n s2 is the specific speed of the secondary impeller, H2 is the head of the secondary 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 is the specific speed of the first-stage impeller in step S203; n s2 is the specific speed of the secondary 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 of the first-stage impeller is Δβ=β1-β1′, wherein the blade inlet angle of attack Δβ is the positive angle of attack, and β1′ is the relative liquid flow angle of the blade inlet; the outlet angle β2 is 22°~30°.

4. The two-stage cryogenic deep well pump design method according to claim 3 is characterized in that: The step S3 comprises: S301, determine the axial distance between the blade 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 is the outlet width of the first-stage impeller in step S204; S302, determining 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 of the space guide vane L3 = 0.5D 2m ~0.7D 2m , where D 2m is the outlet diameter of the first-stage impeller in step S203; S304: Determine the blade wrap angle of the spatial guide vane 5. The two-stage cryogenic deep well pump design method according to claim 3 is characterized in that: The step S4 comprises: Step S401, determining that the number of blades of the radial guide vane is 9; Step S402: Determine the radial guide vane base circle diameter D3, D 2n +2mm≤D3≤D 2n +10mm, where D 2n is the outlet diameter of the secondary impeller in step S203; Step S403: Determine the radial guide vane positive blade inlet width b3, b 2n +2mm≤b3≤b 2n +5mm, where b 2n is the outlet width of the secondary impeller in step S204; Step S404, determining the radial guide vane positive blade diffusion section length L4 = 2.4b3; Step S405, determine the radial guide vane positive blade outlet width b4 = b3 + 12 mm.

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