An axial flow pump structure based on import pre-whirl and impeller outlet without circulation quantity design
By setting a front guide vane on the inlet bell tube of the axial flow pump to form a pre-rotation motion, combined with the impeller outlet non-circulation design, the problems of flow instability and structural complexity of traditional axial flow pumps are solved, and more efficient and stable fluid transportation is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI KAIQUAN PUMP IND GROUP
- Filing Date
- 2025-05-12
- Publication Date
- 2026-06-02
AI Technical Summary
Traditional axial flow pumps suffer from problems such as flow instability, cavitation-induced efficiency reduction, mechanical vibration, high structural complexity, large installation space, and high cost during fluid transportation, which affect their adaptability and stability in modern industrial scenarios.
The axial flow pump structure adopts a design that generates pre-swirl with a front guide vane and has no circulation at the impeller outlet. By setting circumferentially distributed front guide vanes on the inlet bell tube, the fluid motion is optimized, eliminating the traditional matching structure between the guide vane and the impeller, and directly connecting the impeller outlet to the cylinder.
It optimizes cavitation performance, reduces unsteady excitation force, shortens axial length, reduces cost and installation space, and improves fluid transport efficiency and stability.
Smart Images
Figure CN224315187U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to an axial flow pump structure, specifically to an axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design, which provides a certain circulation compensation through pre-swirl generated by a front guide vane and matches the impeller with an outlet no-circulation design. Background Technology
[0002] Traditional axial flow pumps, as core equipment in fluid transport, have long faced the following key technical challenges in practical applications. These shortcomings not only affect pump efficiency and operational stability but also restrict their adaptability in modern industrial scenarios. The inlet bell-shaped tube employs a simple tapered flow channel design, lacking fluid dynamics optimization. When high-speed fluid enters, the absence of guide vanes or a flow grid causes disordered movement of fluid particles in the radial and tangential directions, forming local eddies and abrupt velocity gradient changes. This flow instability leads to a sharp decrease in the effective net positive suction head (NPSHa) at the impeller inlet. When the local pressure falls below the fluid's saturated vapor pressure, cavitation bubbles periodically collapse on the impeller surface, causing fatigue erosion of the metal material. Statistics show that cavitation-induced efficiency reduction can reach 15%-20%, accompanied by severe vibration and noise pollution. Secondly, the residual circulation of the fluid at the impeller outlet (i.e., the rotational kinetic energy component that is not completely converted into pressure energy) forms secondary vortices in the guide vanes. According to Navier-Stokes equations, when this circumferential velocity component does not match the guide vane profile, it will cause boundary layer separation and impact losses, resulting in additional hydraulic losses of approximately 8%-12%. To suppress residual circulation, traditional designs are forced to adopt multi-stage guide vane structures (usually 4-7 vanes). This not only increases the complexity of precision casting (increasing mold costs by more than 30%), but also leads to a large number of welds and assembly gaps inside the flow channel, forming sources of turbulent kinetic energy dissipation. More seriously, the gap flow between the guide vanes and the impeller can induce unsteady excitation forces, threatening the dynamic stability of the rotor.
[0003] The traditional series layout of impeller-guide vane assemblies requires an axial installation space of at least 1.5-2 times the impeller diameter to complete the stepwise conversion of kinetic energy to pressure energy. This linear structure results in the overall pump length generally exceeding 40% of that of a mixed-flow pump with the same parameters. In space-sensitive scenarios such as ship propulsion and mobile pumping stations, compromise solutions such as bent flow channels or external guide vanes are forced, which in turn increases local resistance losses (typically 5%-8%). At the same time, the long shaft structure amplifies the difficulty of matching thermal deformation with critical speed, and is prone to mechanical seal failure under high temperature or variable operating conditions. Utility Model Content
[0004] To address the aforementioned problems, the main objective of this utility model is to provide an axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design, which provides a certain amount of circulation compensation through pre-swirl generated by the front guide vane and matches the impeller with no-circulation design at the outlet.
[0005] This utility model solves the above-mentioned technical problems through the following technical solution: an axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design, the axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design includes: a front guide vane, an impeller, and a cylinder; the front guide vane is set on the inlet bell tube, the front guide vane is provided with circumferentially evenly distributed front guide vane blades, and the impeller outlet is directly connected to the cylinder.
[0006] In a specific embodiment of this utility model, the front guide vane is provided with 4 to 8 circumferentially distributed front guide vane blades.
[0007] In a specific embodiment of this utility model, the installation angle α of the front guide vane blade is 15° to 45°.
[0008] In a specific embodiment of this utility model, the front guide vane has an airfoil cross section with a chord length to pipe diameter ratio L / D1 = 1:8 to 1:12, and the pre-rotation direction of the front guide vane is opposite to the impeller rotation direction; where D1 is the diameter of the front guide vane.
[0009] In a specific embodiment of this utility model, the axial distance between the front guide vane and the impeller is L = 0.08D2 to 0.15D2, where D2 is the impeller diameter.
[0010] In a specific embodiment of this utility model, the absolute velocity angle α3 at the outlet of the impeller is 87° to 93°.
[0011] The positive and progressive effects of this utility model are as follows: Compared with common technologies, the axial flow pump structure based on inlet pre-swirl and impeller outlet non-circulation design provided by this utility model has the following advantages:
[0012] 1. The inlet bell tube is equipped with a front guide vane. When high-speed fluid enters, the guide vane causes the fluid particles to move in an orderly manner in the radial and tangential directions, forming a pre-swirl, which effectively optimizes the cavitation performance of the axial flow pump.
[0013] 2. The traditional impeller-guide vane matching structure is eliminated, directly eliminating the unsteady flow-induced unsteady excitation force between the guide vane and the impeller. At the same time, the axial length is optimized, greatly reducing installation space and cost. Attached Figure Description
[0014] Figure 1 This is a cross-sectional view of the front guide vane and impeller structure.
[0015] Figure 2 This is a schematic diagram showing the matching of the guide vane blades and the impeller blades.
[0016] Figure 3 This is a schematic diagram of velocity triangle analysis.
[0017] Figure 4-1 This is one of the three-dimensional schematic diagrams of the guide vane and impeller blades.
[0018] Figure 4-2 This is the second three-dimensional schematic diagram of the guide vane and impeller blades.
[0019] Figure 4-3 This is the third three-dimensional schematic diagram of the guide vane and impeller blades.
[0020] The following are the names corresponding to the reference numerals in this utility model:
[0021] Front guide vane (1), impeller (2), cylinder (3). Detailed Implementation
[0022] The preferred embodiments of this utility model are given below with reference to the accompanying drawings to illustrate the technical solution of this utility model in detail.
[0023] Figure 1 This is a cross-sectional view of the front guide vane and impeller structure. Figure 2 This is a schematic diagram showing the matching of the guide vane blades and the impeller blades, as shown below. Figure 1-2 As shown, this utility model proposes an axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design includes: a front guide vane 1, an impeller 2, and a cylinder 3; the front guide vane 1 is set on the inlet bell tube, and the front guide vane 1 is provided with circumferentially evenly distributed front guide vane blades, and the outlet of the impeller 2 is directly connected to the cylinder 3.
[0024] The front guide vane 1 of this invention is provided with 4 to 8 circumferentially distributed front guide vane blades, preferably 6. The installation angle α of the front guide vane blades is 15° to 45°. The front guide vane blades have an airfoil cross-section, with a chord length to pipe diameter ratio L / D1 of 1:8 to 1:12. The pre-rotation direction of the front guide vane blades is opposite to the impeller rotation direction; where D1 is the diameter of the front guide vane blade. The axial distance between the front guide vane and the impeller is L of 0.08D2 to 0.15D2, where D2 is the impeller diameter. The outlet absolute velocity angle α3 of the impeller 2 is 87° to 93°. Other values or ranges of the above parameters can be selected according to specific requirements.
[0025] The specific design steps of this utility model can be as follows:
[0026] 1. Generate a pre-rotated guide vane
[0027] The horn-shaped tube section is equipped with Z = 4 to 8 circumferentially distributed front guide vanes (preferably 6), with an installation angle α = 15° to 45°. Alternatively, a mature airfoil section can be used for guide vane placement, with a chord length to tube diameter ratio L / D = 1:8 to 1:12, providing a certain inlet relative velocity circulation, and the pre-rotation direction is opposite to the impeller rotation direction.
[0028] 2. Impeller outlet non-circulating design
[0029] When designing the impeller, the outlet absolute velocity angle α3 = 87° to 93° is set to ensure that the circumferential component is eliminated in the axial outflow.
[0030] 3. Axial flow pump structural integration optimization
[0031] The traditional guide vane structure is eliminated, and the impeller outlet is directly connected to the cylinder; the axial distance between the trumpet tube and the impeller is L = 0.08D~0.15D (D is the impeller diameter); the overall axial length is reduced by more than 35%, and the weight and cost will be greatly reduced.
[0032] This invention features a front guide vane installed in the inlet bell-shaped tube. When high-speed fluid enters, the guide vane causes the fluid particles to move in an orderly manner in the radial and tangential directions, forming a pre-swirl, which effectively optimizes the cavitation performance of the axial flow pump.
[0033] This invention eliminates the traditional impeller-guide vane matching structure, directly eliminating the unsteady flow-induced unsteady excitation force between the guide vane and the impeller, while optimizing the axial length, greatly reducing installation space and cost.
[0034] The following are the specific steps of an example:
[0035] Figure 2 This is a schematic diagram showing the matching of the guide vane blades and the impeller blades. Figure 3 A schematic diagram of velocity triangle analysis, as shown below. Figure 2 and 3 The above design was implemented using a DN300 axial flow pump as described in the embodiment.
[0036] Design parameters: Q = 380 L / s, head H = 6 m, speed n = 1450 r / min, NPSHa = 7 m.
[0037] 1. Front guide vane design
[0038] The front guide vane generates a controllable pre-rotation circulation (Γ1 = 2.44 m² / s) through the NACA65-010 airfoil (chord length 30 mm, installation angle α = 22°), which compensates for the impeller inlet energy and reduces the impeller load.
[0039] Number of blades: Z = 6, evenly distributed circumferentially.
[0040] Pre-swirl velocity: Cu2=Γ1*2πR=2.44*2π×0.15≈2.58m / s, where Γ1 is circulation, m2 / s; R is impeller radius.
[0041] Axial velocity: Cm=Q / π(D2-dh2)4≈6.4m / s, where D is the impeller diameter and dh is the hub diameter.
[0042] The outlet angle of the guide vane is: β1=arctan(Cm1 / U1)≈22°, where U1 is the tangential component of the inlet circumference velocity; Cm1 is the axial velocity, m / s.
[0043] Lead guide vane chord length: L = 30mm, (L / D = 1:1.8~1:12)
[0044] Pre-selected direction: opposite to the impeller installation direction, such as... Figure 2 As shown in the velocity triangle at point C, ensure inlet circulation compensation.
[0045] 2. Impeller Design
[0046] Impeller diameter D = 300mm, hub ratio dh / D = 0.4, number of blades Z = 4 (determined based on specific speed ns≈850).
[0047] In order to precisely match the flow field at the guide vane outlet with the impeller inlet blade placement angle (β2 = 22°), reduce inlet impact loss, and ensure efficient transfer of pre-swirl energy to the impeller.
[0048] Blade outlet angle: β3=arctan(Cm / u3)≈15.7°, forcibly eliminating the circumferential velocity component Cu3=0, achieving theoretically pure axial flowout as shown in the attached figure. Figure 2 The velocity triangle at point -D is shown.
[0049] The density of the leaf stalk is l / t = 0.96~0.73 (rim-hub).
[0050] 3. Installation of the front guide vane and impeller
[0051] The distance d between the outlet edge of the guide vane and the inlet edge of the impeller is 0.08D to 0.15D = 30mm, as shown in the attached figure. Figure 1 As shown.
[0052] 4. Theoretical head calculation and verification
[0053] The hydraulic efficiency ηh = 0.85 - 0.0012ns = 0.85 - 0.0012 × 850 ≈ 83.8%, where ns is the specific speed.
[0054] Euler's equation: H = (u2vu2 - u1vu1) / g = 6m, where u2 is the exit circumferential velocity, vu2 is the tangential component of the exit circumferential velocity, u1 is the inlet circumferential velocity, and vu1 is the tangential component of the inlet circumferential velocity;
[0055] NPSHr=Cm2 / 2g+Λ*U22 / 2g=5.2m,
[0056] Where Cm2 / (2g) represents the dynamic head corresponding to the absolute velocity at the impeller inlet, Cm is the absolute velocity of the fluid at the impeller inlet, and g is the acceleration due to gravity; U22 / (2g) represents the dynamic head corresponding to the circumferential velocity at the impeller outlet, U2 is the circumferential velocity at the impeller outlet; Λ is a correction coefficient, which is usually related to the pump geometry and internal flow losses.
[0057] The above theoretical design meets the requirements for head and cavitation performance. The pre-rotation compensation of the front guide vane reduces the impact loss at the impeller inlet, optimizes the process structure, and the absence of a rear guide vane optimizes the axial length of the entire pump, reducing installation space and cost.
[0058] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection of this utility model as defined by the appended claims and their equivalents.
Claims
1. An axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design, characterized in that: The axial flow pump structure based on inlet pre-swirl and impeller outlet non-circulation design includes: a front guide vane (1), an impeller (2), and a cylinder (3); the front guide vane (1) is installed on the inlet bell pipe, and the front guide vane (1) is provided with circumferentially evenly distributed front guide vane blades; the outlet of the impeller (2) is directly connected to the cylinder (3).
2. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design according to claim 1, characterized in that: The front guide vane (1) is provided with 4 to 8 circumferentially distributed front guide vane blades.
3. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design according to claim 2, characterized in that: The installation angle α of the guide vane blades is 15° to 45°.
4. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design according to claim 1, characterized in that: The guide vane blade has an airfoil cross section with a chord length to pipe diameter ratio L / D1 = 1:8 to 1:
12. The pre-rotation direction of the guide vane blade is opposite to that of the impeller; where D1 is the diameter of the guide vane blade.
5. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design according to claim 1, characterized in that: The axial distance between the guide vane and the impeller is L = 0.08D2 to 0.15D2, where D2 is the impeller diameter.
6. The axial flow pump structure based on inlet pre-swirl and impeller outlet no-circulation design according to claim 1, characterized in that: The absolute velocity angle α3 at the outlet of the impeller (2) is 87° to 93°.