A method for designing a mixed flow pump impeller

Abstract

The application discloses a mixed-flow mixed-conveying pump impeller design method and belongs to the technical field of deep-sea oil and gas exploitation. First, front and back cover plate contour lines are designed; then, an axial surface flow line capable of passing through a water section area verification is drawn according to the designed front and back cover plate contour lines; then, a blade contour is designed according to the drawn axial surface flow line and combined with blade design parameters; finally, a wood mold drawing is drawn, and a complete impeller is obtained by modeling by using three-dimensional software. The application can realize the structural design of the mixed-flow mixed-conveying pump impeller under the condition of a given working condition, thereby providing theoretical guidance for the design optimization of a pressure boosting structure. Moreover, the impeller obtained by the mixed-conveying pump impeller design method according to the application can meet the characteristic process requirement, and the application fills the blank in the mixed-conveying pump field.

Description

Technical Field

[0001] This invention belongs to the field of deep-sea oil and gas extraction technology, specifically relating to a design method for a mixed-flow mixed-transport pump impeller. Background Technology

[0002] Multiphase pumps are used to pressurize multiphase working fluids in production and transportation pipelines, enabling long-distance transportation of multiphase working fluids from wellhead to platform, platform to platform, or platform to land. As deep-sea oil and gas field development gradually extends into the deep sea, the quality of oil becomes increasingly viscous, and the gas content gradually increases. This places high demands on the R&D and manufacturing teams of deep-sea multiphase pumps. They must ensure both high-efficiency pressurization and safety and reliability, and prevent pressurization failure or abnormal vibration due to excessive gas content. Otherwise, it could lead to serious consequences, ranging from ineffective transportation to damage to mechanical components or even marine pollution.

[0003] There are three types of deep-sea mixed-flow pumps: centrifugal, axial-flow, and mixed-flow. Centrifugal pumps cannot accommodate gas contents exceeding 10%, and axial-flow pumps cannot provide efficient pressurization. Therefore, mixed-flow pumps are currently the best choice for deep-sea oil and gas exploration. Developed countries such as the UK (North Sea oil fields) and the US (Prezioso oil fields) began research and development of mixed-flow pumps in the 1980s.

[0004] The design and manufacturing of the core components of mixed-flow pumps are extremely difficult, and there is currently no mature design method for the impeller of mixed-flow pumps. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a design method for a mixed-flow pump impeller, which enables the structural design of the impeller under given operating conditions, achieving high design accuracy and meeting specific process requirements.

[0006] This invention is achieved through the following technical solution:

[0007] This invention discloses a design method for a mixed-flow mixed-transfer pump impeller, wherein the mixed-flow mixed-transfer pump impeller includes a front cover plate, a rear cover plate, and a number of blades arranged in a circumferential array between the front cover plate and the rear cover plate.

[0008] Design methods include:

[0009] S1: Determine the design parameters of the front cover and rear cover, and draw the outline of the front cover and rear cover according to the design parameters;

[0010] S2: Based on the outlines of the front and rear cover plates drawn in S1, draw the axial streamlines that can be verified by the cross-sectional area of ​​the water passage.

[0011] S3: Determine the design parameters of the blade and design the blade profile line in conjunction with the axial streamline drawn in S2;

[0012] S4: Draw the wooden model of the impeller based on the outlines of the front and rear cover plates drawn in S1, the axial streamlines drawn in S2, and the blade outlines drawn in S3, and perform three-dimensional modeling to complete the design of the impeller of the mixed-flow pump.

[0013] Preferably, S1 specifically refers to the design parameters of the front cover and the rear cover, including: inlet inner diameter. , inlet outer diameter Outlet inner diameter Outer diameter of the outlet Angle of the front cover outlet section and the exit angle ;

[0014] Calculate the specific speed based on the given operating conditions. :

[0015]

[0016] in: For a given single-phase boost, For a given flow rate; Given the impeller speed;

[0017] Inlet inner diameter Determined by the dimensions of the motor shaft used to drive the blades;

[0018] Inlet outer diameter for:

[0019]

[0020] in: The effective diameter of the inlet. k is the size factor;

[0021] Outlet inner diameter The value of is related to the inlet outer diameter Consistent;

[0022] Outer diameter for:

[0023]

[0024] in: The average diameter at the outlet. ; This is the correction factor for the export diameter;

[0025] Draw the outlines of the front cover (1) and the rear cover (2).

[0026] More preferably, the angle of the front cover outlet section The value range is 50° to 80°, and the exit angle is [missing information]. The value is 60°.

[0027] More preferably, the outlet width L of the front cover plate and the rear cover plate is... out Replace the exit angle The design parameters for the front and rear cover plates include: inlet inner diameter. , inlet outer diameter Outlet inner diameter Outer diameter of the outlet Angle of the front cover outlet section and the outlet width L out ;

[0028] Export width The calculation method is as follows:

[0029]

[0030] in The export width correction factor is calculated using the following formula:

[0031] .

[0032] Preferably, S2 specifically comprises:

[0033] Using the outlines of the front and rear covers as baselines, draw multiple inscribed circles between the two baselines along the flow direction. Let A be the point of tangency between the inscribed circle and the rear cover outline, and B be the point of tangency with the front cover outline. Let O be the center of the inscribed circle. Connect the two tangency points A and B, and trisect the line segment OC between the midpoint C of the line AB and the center O. Let D and E be the two points used to trisect the line segment OC. Point D is the point closest to the center O. Point E is used to verify the cross-sectional area of ​​the water passage. If the difference in the cross-sectional area of ​​the water passage calculated at each point E is within a set threshold range, then point D is considered to be the point through which the streamline passes. Connecting all points D forms the axial streamline. Otherwise, adjust the outlines of the front and rear covers until the difference in the cross-sectional area of ​​the water passage calculated at each point E is within a set threshold range.

[0034] More preferably, multiple axial streamlines are drawn between the outlines of the front cover and the rear cover. When drawing the axial streamlines, the outline of the front cover and the adjacent drawn axial streamlines are used as reference lines, or the outline of the rear cover and the adjacent drawn axial streamlines are used as reference lines, or two adjacent drawn axial streamlines are used as reference lines; thus, axial streamlines are drawn between two reference lines.

[0035] Preferably, in S3, determining the blade design parameters includes: blade inlet angle and outlet angle. , wrap angle and blade thickness;

[0036] The blade inlet angle is determined by the inlet fluid flow angle. with blade angle of attack The inlet flow angle is obtained by adding them together. From the velocity triangle, we can deduce:

[0037]

[0038] in: The inlet axial velocity of the blade. The circumferential velocity; from this, the streamline inlet angle of each axial streamline plotted by S2 can be obtained. .

[0039] More preferably, the blade angle of attack The value ranges from 0 to 15°, and the exit angle is... The value range is 20±5°; the wrap angle is 360° / number of blades, and the number of blades is 4 to 8; the blade thickness is selected based on the bearing capacity.

[0040] More preferably, after determining the design parameters of the blade, streamlines are divided into points using the conformal grid method, and the profiles of each axial streamline, as well as the front and rear cover plate outlines, are drawn. Then, the integer wrap angle positions are restored from the profile drawing to the axial drawing, and the blade cross-sections at different wrap angles are drawn in combination with the calculated blade thickness. Then, it is checked whether the blade profile is perpendicular to the axial streamline. If it is not perpendicular, fine adjustments are made on the profile drawing to finally obtain a uniform blade profile.

[0041] Compared with the prior art, the present invention has the following beneficial technical effects:

[0042] The design method for the impeller of the mixed-flow pump disclosed in this invention determines the design parameters of the front and rear cover plates based on the principles of fluid mechanics. It allows for precise calculations tailored to specific external dimensional requirements and the characteristics of the materials being transported, outperforming empirical formulas used in the design of other types of pumps. The method for drawing and detecting axial streamlines allows for fine adjustment of the flow channel cross-sectional parameters and the expected streamline direction, eliminating the need for trial and error, significantly increasing accuracy and reducing rework rates. Drawing multiple axial streamlines between the determined front and rear cover plate contours allows for control of fluid flow along radially arranged expected streamlines, reducing backflow and flow separation losses, and improving design accuracy and operational stability. This invention enables the structural design of the impeller for the mixed-flow pump under given operating conditions, providing theoretical guidance for the design optimization of booster structures. Furthermore, the impeller designed using the method of this invention meets specific process requirements, filling a gap in the field of mixed-flow pumps. Attached Figure Description

[0043] Figure 1This is a schematic diagram of the axial surface of the impeller of the mixed-flow mixed-transport pump of the present invention;

[0044] Figure 2 This is a schematic diagram of the water passage section of the impeller;

[0045] Figure 3 To draw a schematic diagram of multiple axial streamlines;

[0046] Figure 4 The diagram shows the design process of the blade, where (a) is a cross-sectional view of the blade, (b) is a schematic diagram of the streamline division points, and (c) is a schematic diagram of the blade profile.

[0047] Figure 5 This is a diagram of a wooden mold.

[0048] Figure 6 Here are schematic diagrams of the designed blades and impeller, where (a) is a schematic diagram of a single blade, (b) is a schematic diagram of an array of blades, and (c) is a schematic diagram of an impeller;

[0049] Figure 7 A three-dimensional view of the designed impeller;

[0050] Figure 8 The designed impeller is shown in the single-phase booster schematic diagram (a) and 80m. 3 Schematic diagram of two-phase pressurization at a liquid flow rate of / h (b);

[0051] Wherein: 1-front cover plate, 2-rear cover plate, 3-blade. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. This description is intended to explain the invention and not to limit it.

[0053] This embodiment provides a design method for a mixed-flow pump impeller, which enables the structural design of the mixed-flow pump impeller under given operating conditions.

[0054] The impeller of the mixed-flow pump includes a front cover plate 1, a rear cover plate 2, and several blades 3 arranged in a circumferential array between the front and rear cover plates. Therefore, the structural design of the impeller includes the design of the structural parameters of the front cover plate 1, the rear cover plate 2, and the blades 3; and this design is based on the structural design of a given working condition.

[0055] In this example, the given operating conditions are: when the impeller rotates at a speed n of 3500 rpm, the single-phase booster is at 80 m... 3 At a flow rate of / h, it can reach 17m (that is, when the flow rate is / h). =80m 3 / h, single-phase boost =17m), the designed impeller must be able to stably pressurize the gas under the given operating conditions, with a gas volume fraction of less than 40% in a two-phase configuration.

[0056] The specific steps of this method are as follows:

[0057] Step 1: Determine the design parameters of the front and rear cover plates to obtain their outlines:

[0058] First, determine the design parameters of the front and rear cover plates, such as... Figure 1 As shown, to obtain the outlines of the front and rear cover plates, the design parameters of the front and rear cover plates should include: inlet inner diameter. , inlet outer diameter Outlet inner diameter Outer diameter Angle of the front cover outlet section (i.e., the angle between the front cover outlet section and the impeller axis) and the outlet angle Or use the outlet width L out (i.e., the distance between the front and rear cover plate outlet ends) Replace outlet bevel angle That is, the exit angle and the outlet width L out Choose one of the two.

[0059] First, calculate the specific speed based on the given operating conditions. :

[0060] (1)

[0061] in: For single-phase boosting under given operating conditions, The flow rate under a given operating condition; The impeller speed is given under a given operating condition.

[0062] Due to the outer diameter of the inlet The design is mainly based on the inlet inner diameter The size is obtained by using Bernoulli's principle to determine the effective inlet diameter. for:

[0063] (2)

[0064] Where: k is a size factor. Since the mixed-flow pump involved in this example is mainly used for transporting multiphase fluids, there is almost no cavitation problem. The value of k should be 4 to 4.25.

[0065] The inlet inner diameter of the front and rear cover plates is determined based on the dimensions of the motor shaft used to drive the blades. In this example, the inlet inner diameter is taken as... The diameter is 64mm, which can be considered the diameter of the central hub of the motor shaft. This is to maintain the effective flow area at the inlet. , inlet outer diameter It should be:

[0066] (3)

[0067] Because the impeller of a mixed-flow pump differs from that of a traditional centrifugal pump, its outlet is often located at a different radial position, typically using an average diameter... To characterize it, it is defined as:

[0068] (4)

[0069] The value of is obtained from the following:

[0070] (5)

[0071] in: This is the export diameter correction factor. The larger the impeller blade, the more upward the outlet, making it more similar to a centrifugal pump. Because its blades cannot fully spread the gas, it can withstand a lower gas content. Conversely, The smaller the value, the worse its boost performance. (Regarding specific speed) Recommended for 200-1000 Choose 1.0 to 1.2.

[0072] Outlet inner diameter The value is usually related to the inlet outer diameter. To maintain consistency, the outlet outer diameter can be calculated using the above formula (4). .

[0073] Exit section angle Generally, an exit angle of 50–80 degrees is selected. In engineering, 60° is generally used.

[0074] When the exit angle is not used Instead, calculate the exit width. At that time, the width of the outlet The calculation method is as follows:

[0075] (6)

[0076] in The export width correction factor is calculated using the following formula:

[0077] (7)

[0078] There are no absolute requirements for the axial length of the front and rear cover plates. In principle, the longer the axial length, the stronger its gas-bearing capacity, but the frictional resistance increases and the efficiency decreases. The shorter the axial length, the lower its gas-bearing capacity. Generally, a length close to the specified value is chosen. This can be done, or it can be fully verified in subsequent simulations for different fluid properties.

[0079] Based on the above calculations, the initial outlines of the front and rear cover plates are drawn. In this example, the initial outlines of the front and rear cover plates are as follows: Figure 1 As shown.

[0080] Step 2: Draw the axial streamlines that can be verified by the cross-sectional area of ​​the water passage.

[0081] After verifying the change in the cross-sectional area of ​​the axial flow channel, which is the same as that of a centrifugal pump, the axial streamlines are drawn. The process is as follows:

[0082] like Figure 2 As shown, multiple inscribed circles are drawn along the flow direction between the outline of the front cover plate 1 and the outline of the rear cover plate 2, i.e., the inscribed circle is tangent to the outline of the front cover plate 1 and the outline of the rear cover plate 2, respectively; let A be the point of tangency between the inscribed circle and the outline of the rear cover plate 2, and B be the point of tangency with the outline of the front cover plate 1, with the center of the inscribed circle being O; then connect the two points of tangency A and B, and trisect the line segment OC between the midpoint C of the connecting line AB and the center O, let D and E be the two points used to trisect the line segment OC; where point D is the trisection point closest to the center O; point E is used to verify the cross-sectional area of ​​the water passage. If the cross-sectional area of ​​the water passage calculated at each point E is... If the surface areas are nearly identical and there are no significant differences (e.g., the difference between the calculated maximum and minimum cross-sectional areas is within a set threshold range), then point D is considered the point through which the streamline passes, and connecting points D yields the axial streamline. If there are significant differences (e.g., the difference between the calculated maximum and minimum cross-sectional areas exceeds a set threshold range), then the contour lines of the front and rear covers are adjusted (i.e., while keeping the designed parameters of the front and rear covers unchanged, the curvature of the front and rear cover contour lines is finely adjusted) until the calculated cross-sectional areas at each point E are nearly identical. This allows for the production of front and rear covers with appropriate contour curvature.

[0083] Step 2 yields axial streamlines that can be verified by the cross-sectional area of ​​the water passage, thereby determining the approximate flow direction and path of the fluid within the cavity.

[0084] To improve design accuracy, in step 2, multiple axial streamlines are drawn between the front and rear cover plate outlines using the same method described above. For example... Figure 3As shown, firstly, multiple inscribed circles are drawn along the flow direction between the outline of the front cover plate 1 and the outline of the rear cover plate 2, thereby obtaining an axial streamline, denoted as axial streamline A1; then, multiple inscribed circles are drawn along the flow direction between the outline of the front cover plate 1 and the axial streamline A1, and the same method is used to obtain the axial streamline between the outline of the front cover plate 1 and the axial streamline A1, denoted as axial streamline A2; multiple inscribed circles are drawn along the flow direction between the axial streamline A1 and the outline of the rear cover plate 2, and the same method is used to obtain the axial streamline between the axial streamline A1 and the outline of the rear cover plate 2, denoted as axial streamline A3; and so on, multiple axial streamlines can be obtained.

[0085] Step 3: Determine the blade design parameters:

[0086] Perform blade inlet angle and outlet angle Calculation of parameters such as the wrap angle and blade thickness; where the blade inlet angle is determined by the inlet flow angle. with blade angle of attack The inlet flow angle is obtained by adding them together. This can be derived from the velocity triangle:

[0087] (8)

[0088] in: Let be the axial velocity at the blade inlet, which can be obtained from the flux formula. The circumferential velocity is determined by the inlet diameter of the axial streamline (the diameter of the circle obtained by rotating the inlet point of the axial streamline around the impeller axis) and the rotational speed (i.e., the impeller speed under a given operating condition). From this, the streamline inlet fluid flow angle of each axial streamline drawn in step 2 can be obtained. .

[0089] Under normal circumstances, the blade angle of attack The angle of attack is 0 to 15°. In this example, 5° is selected as the commonly used blade angle of attack.

[0090] Exit Angle Choose an angle of approximately 20±5° or use the same method as the inlet angle calculation to calculate the velocity triangle, striving for a smooth curve.

[0091] Choose the wrap angle as 360° / number of blades. The number of blades is generally 4 to 8. When drawing the profile, you can make appropriate adjustments to ensure that the blade surface is smooth.

[0092] The blade thickness is selected based on the bearing capacity. Local increases in thickness can be calculated using a local velocity triangle or obtained through simulated pressure contour plots. At this point, all parameters of the blade have been calculated.

[0093] like Figure 4As shown, streamlines are divided into points using a conformal grid method, and the profile lines of each axial streamline, as well as the outlines of the front cover 1 and the rear cover 2, are drawn; Figure 4 As shown in (c), when there is only one axial streamline, draw the profile of the axial streamline, the outline of the front cover plate 1, and the outline of the rear cover plate 2; then restore the integer wrap angle position from the profile drawing to the axial drawing, and draw the blade cross-section at different wrap angles in combination with the calculated blade thickness. Then check whether the blade profile is perpendicular to the axial streamline. If it is not perpendicular, make fine adjustments on the profile drawing to finally obtain a uniform blade profile.

[0094] Step 4: As Figure 5 As shown, the final step is to draw the wooden model and then model it using 3D software, as follows: Figure 6 and Figure 7 As shown, the impeller is replicated in an array based on the number of blades, and finally front and rear cover plates are added to obtain a complete impeller.

[0095] like Figure 8 As shown, fluid simulation of the impeller under this design condition yielded single-phase and 80m... 3 The two-phase pressurization curve at a liquid flow rate of / h is consistent with expectations. Practical verification has shown that the designed impeller can withstand higher gas content under higher pressurization conditions.

[0096] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, should all be covered within the scope of protection of the present invention.

Claims

1. A method for designing an impeller for a mixed-flow pump, characterized in that, The impeller of the mixed-flow pump includes a front cover plate (1), a rear cover plate (2), and a number of blades (3) arranged in a circumferential array between the front cover plate (1) and the rear cover plate (2). Design methods include: S1: Determine the design parameters of the front cover (1) and the rear cover (2) and draw the outline of the front cover (1) and the rear cover (2) according to the design parameters; S2: Based on the outlines of the front cover plate (1) and the rear cover plate (2) drawn in S1, draw the axial streamlines that can be verified by the cross-sectional area of ​​the water passage. S3: Determine the design parameters of the blade (3) and design the profile of the blade (3) in conjunction with the axial streamline drawn in S2; S4: Draw the wooden model and perform 3D modeling to complete the design of the impeller of the mixed-flow pump; S2 specifically refers to: Using the outline of the front cover plate (1) and the outline of the rear cover plate (2) as reference lines, draw multiple inscribed circles between the two reference lines along the flow direction. Let the point of tangency between the inscribed circle and the outline of the rear cover plate be A, and the point of tangency between the inscribed circle and the outline of the front cover plate (1) be B. Let the center of the inscribed circle be O. Connect the two points of tangency A and B, and divide the line segment OC between the midpoint C of the connecting line AB and the center O into three equal parts. Let the two points used to divide the line segment OC into three equal parts be D and E respectively. Among them, point D is the dividing point close to the center O. Point E is used to verify the cross-sectional area of ​​the water passage. If the difference in the cross-sectional area of ​​the water passage calculated at each point E is within the set threshold range, then point D is considered to be the point through which the streamline passes. Connecting all points D is the axial streamline. Otherwise, adjust the outlines of the front cover plate (1) and the rear cover plate (2) until the difference in the cross-sectional area of ​​the water passage calculated at each point E is within the set threshold range. Multiple axial streamlines are drawn between the outlines of the front cover (1) and the rear cover (2). When drawing the axial streamlines, the outline of the front cover (1) and the adjacent drawn axial streamlines are used as the reference lines, or the outline of the rear cover (2) and the adjacent drawn axial streamlines are used as the reference lines, or two adjacent drawn axial streamlines are used as the reference lines; thus, axial streamlines are drawn between the two reference lines.

2. The impeller design method for a mixed-flow pump according to claim 1, characterized in that, S1 specifically refers to the design parameters of the front cover plate (1) and the rear cover plate (2), including: inlet inner diameter. , inlet outer diameter Outlet inner diameter Outer diameter Front cover plate (1) Exit section angle and the exit angle ; Calculate the specific speed based on the given operating conditions. : in: For a given single-phase boost, For a given flow rate; Given the impeller speed; Inlet inner diameter Determined by the dimensions of the motor shaft used to drive the blades; Inlet outer diameter for: in: The effective diameter of the inlet. k is the size factor; Outlet inner diameter The value of is related to the inlet outer diameter Consistent; Outer diameter for: in: The average diameter at the outlet. ; This is the correction factor for the export diameter; Draw the outlines of the front cover (1) and the rear cover (2).

3. The impeller design method for a mixed-flow pump according to claim 2, characterized in that, Front cover plate (1) outlet section angle The value range is 50° to 80°, and the exit angle is [missing information]. The value is 60°.

4. The impeller design method for a mixed-flow pump according to claim 2, characterized in that, The outlet width L of the front cover plate (1) and the rear cover plate (2) out Replace the exit angle The design parameters for the front cover (1) and the rear cover (2) include: inlet inner diameter , inlet outer diameter Outlet inner diameter Outer diameter Front cover plate (1) Exit section angle and the outlet width L out ; Export width The calculation method is as follows: in The export width correction factor is calculated using the following formula: 。 5. The impeller design method for a mixed-flow pump according to claim 1, characterized in that, In S3, the design parameters for blade (3) include: blade inlet angle and outlet angle. , wrap angle and blade thickness; The blade inlet angle is determined by the inlet fluid flow angle. with blade angle of attack The inlet flow angle is obtained by adding them together. From the velocity triangle, we can deduce: in: The inlet axial velocity of the blade. The circumferential velocity; from this, the streamline inlet angle of each axial streamline plotted by S2 can be obtained. .

6. The impeller design method for a mixed-flow pump according to claim 5, characterized in that, blade angle of attack The value ranges from 0 to 15°, and the exit angle is... The value range is 20±5°; the wrap angle is 360 / number of blades, and the number of blades (3) is 4 to 8; the blade thickness is selected by the bearing strength.

7. The impeller design method for a mixed-flow pump according to claim 5, characterized in that, After determining the design parameters of the blade (3), streamlines are divided by the grid conformal method, and the profiles of each axial streamline, the front cover plate (1) profile, and the rear cover plate (2) profile are drawn. Then, the integer wrap angle positions are restored from the profile drawing to the axial drawing. Combined with the calculated blade thickness, the blade cross-sections at different wrap angles are drawn. Then, check whether the blade profile is perpendicular to the axial streamline. If it is not perpendicular, make fine adjustments on the profile drawing to finally obtain a uniform blade profile.

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