A Francis pump-turbine runner and a method for optimizing runner S characteristics

Abstract

The application relates to a mixed-flow pump-turbine runner and a runner S characteristic optimization method, and belongs to the technical field of hydraulic machinery.The application aims to solve the problems that the diameter of the high-pressure side of a pump-turbine runner of a high-head and large-capacity pumping and storing unit needs to be set larger, the runner inlet height needs to be lower, the S characteristic is more prominent, the frequency of starting and stopping and load shedding of pumping and storing units for intermittent energy such as wind and light is increased, and the risk of operation of the pumping and storing unit in the S area is increased, and the application comprises an upper crown, a lower ring and multiple blades; the upper crown is arranged above the lower ring, multiple blades are arranged in a passage between the upper crown and the lower ring, the multiple blades are arranged in a radial direction, and the high-pressure side of each blade is processed with a concave-convex knot airfoil type. The application further relates to a mixed-flow pump-turbine runner S characteristic optimization method, which comprises the following steps: step one, modeling through three-dimensional modeling software; and step two, forming a spatial curve by intersecting a circular pipe with blades in a blade middle surface. The application belongs to the technical field of runner design of a hydraulic turbine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic machinery, in particular to a Francis pump-turbine runner and a runner S characteristic optimization method, and belongs to the technical field of hydraulic turbine runner design. BACKGROUND

[0002] The runner of the pump-turbine is the core component of the pumped storage unit, and the S characteristic thereof in the water turbine working condition is related to whether the unit can be safely and stably operated. The runner with poor S characteristic will cause problems such as difficulty in grid connection when the unit is started at low water head and severe vibration when the unit is tripped. Therefore, sufficient safety margin needs to be left during the research and design of the runner. At present, the pumped storage unit is developing towards high water head and large capacity, and the diameter of the high pressure side of the runner needs to be designed to be larger, and the runner inlet height needs to be lower, which makes the S characteristic more prominent. In addition, the proportion of intermittent energy such as wind and light in the power grid is increasing year by year, and the frequency of starting and stopping and tripping of the pumped storage unit is increasing, which increases the risk of operation of the unit in the S region. SUMMARY

[0003] The purpose of the present application is to solve the problem that the diameter of the high pressure side of the runner of the high water head and large capacity pumped storage unit needs to be designed to be larger, the runner inlet height needs to be lower, which makes the S characteristic more prominent, and at the same time, the frequency of starting and stopping and tripping of the pumped storage unit for the intermittent energy such as wind and light is increasing, which increases the risk of operation of the pumped storage unit in the S region, and then a Francis pump-turbine runner and a runner S characteristic optimization method are provided.

[0004] The present application solves the above technical problems by the following scheme:

[0005] A Francis pump-turbine runner, comprising an upper crown, a lower ring and a plurality of blades, wherein the upper crown is arranged above the lower ring, a plurality of blades are arranged in the channel between the upper crown and the lower ring, the plurality of blades are arranged uniformly along the radial direction, and the high pressure side of each blade is processed with a concave-convex knot airfoil.

[0006] Further, the axial projection of the concave-convex knot airfoil is a wave-shaped structure, the concave-convex knot airfoil is linearly connected or smoothly arcuately connected with the upper crown above, and the concave-convex knot airfoil is linearly connected or smoothly arcuately connected with the high pressure side below.

[0007] A Francis pump-turbine runner S characteristic optimization method, the method is realized according to the following steps:

[0008] Step 1: modeling by UG three-dimensional modeling software, taking the high pressure side of the blade as the center, and taking the linear distance s from the wave crest to the wave trough of the concave-convex knot airfoil as the radius to make a circular tube feature;

[0009] Step two: the circular tube and the blade of the circular tube feature intersect in the blade to form a spatial curve, a geometric control point is set on the high-pressure side of the base runner blade and the spatial curve, and then a high-pressure side with concave-convex joints is generated by connecting the lines to form the high-pressure side with concave-convex joints, and the blade surface is refitted with the high-pressure side with concave-convex joints.

[0010] Further, on the runner axial plane, the distance of the high-pressure side along the X axis to the Z axis is s, s is the distance from the peak to the valley of the concave-convex joint airfoil, and the value range needs to meet 0.5‰D < s < 2t, wherein D is the diameter of the runner high-pressure side, t is the maximum thickness value of the runner blade, and the Z axis is the rotation axis of the runner.

[0011] Further, on the runner axial plane, the value range of the distance g1 of the starting point of the concave-convex joint airfoil to the intersection point of the high-pressure side and the upper crown along the Z axis needs to meet g1 < 0.2b, wherein b is the total height of the high-pressure side.

[0012] Further, on the runner axial plane, the value range of the distance g2 of two adjacent wave crests along the Z axis needs to meet L / 10 < g2 < L / 2, and the maximum value of the total height L of the concave-convex joint airfoil in the Z axis direction needs to meet L < 0.6b-g1.

[0013] Further, the circular tube feature in step one is a circle formed by rotating the high-pressure side on the blade as the center and s as the radius.

[0014] The most prominent feature and significant beneficial effect of the present application is:

[0015] 1. Research shows that the S characteristic of the pump-turbine is related to the runner inlet recirculation zone. The runner inlet recirculation zone is formed on the upper crown side, and gradually expands to the lower ring side as the operating condition deepens into the braking zone, causing the resistance of the runner passage to the upstream flow to increase. By optimizing the control parameters of the runner blade airfoil, the S characteristic can be optimized.

[0016] 2. After the concave-convex joint airfoil 6 is added to the high-pressure side 4 of the runner blade, the fluid flow through the high-pressure side, the flow separation causes the flow lines to converge along the convex structure of the concave-convex joint airfoil 6 to the concave structure valley bottom, which can suppress or improve the occurrence and development of the runner inlet recirculation zone when the pump-turbine operates in the S zone. At the same time, the distribution of the concave-convex joint airfoil 6 is mainly concentrated on the upper crown 1 side, which can ensure that the influence on other performances (pump and turbine energy, pump hump characteristic) is small. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic view of the mixed-flow pump-turbine runner assembly according to the present application.

[0018] Figure 2 It is a schematic view of the mixed-flow pump-turbine runner blade arrangement according to the present application.

[0019] Figure 3 The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application.

[0020] Figure 4 The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application.

[0021] Figure 5 The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application.

[0022] Figure 6 The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application.

[0023] Figure 7 The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application.

[0024] The axial section view of the runner blade of the conventional mixed-flow pump turbine according to the present application. DETAILED DESCRIPTION

[0025] Embodiment I: in combination with Figures 1-4 The present embodiment is described, the runner of the mixed-flow pump turbine given by the present embodiment comprises an upper crown 1, a lower ring 2 and a plurality of blades 3; the upper crown 1 is arranged above the lower ring 2, a plurality of blades 3 are arranged in the passage between the upper crown 1 and the lower ring 2, the plurality of blades 3 are arranged uniformly along the radial direction, the high-pressure side 4 of each blade 3 is processed with a concave-convex knot airfoil 6, and the low-pressure side 5 of each blade 3 is respectively fixedly connected with the rotating shaft.

[0026] Embodiment II: in combination with Figures 1-4 The present embodiment is described, the runner of the mixed-flow pump turbine given by the present embodiment, the axial projection of the concave-convex knot airfoil 6 is a wave-shaped structure, the concave-convex knot airfoil 6 is linearly connected or smoothly arcuately connected with the upper crown 1 above, and the concave-convex knot airfoil 6 is linearly connected or smoothly arcuately connected with the high-pressure side 4 below. The other structure connection relationship is the same as that of embodiment I.

[0027] Embodiment III: in combination with Figures 1-7 The present embodiment is described, the runner of the mixed-flow pump turbine S characteristic optimization method given by the present embodiment, the method is realized according to the following steps:

[0028] Step one: three-dimensional modeling is carried out through UG modeling software, taking the high-pressure side 4 of the blade 3 as the center and taking the linear distance value s of the concave-convex knot airfoil 6 from the wave crest to the wave trough as the radius to make a circular tube feature;

[0029] Step two: the circular tube feature intersects with the blade 3 at the blade mid-surface 7 to form a spatial curve 8, a geometric control point is set at the base runner blade high pressure side 4 and the spatial curve 8, and then a high pressure side with concave-convex nodes is generated by connecting the line segments, and the blade surface is refitted with the high pressure side with concave-convex nodes.

[0030] Specific implementation four: combination Figures 1-6 The present embodiment is described, and the S characteristic optimization method of the mixed-flow pump turbine runner given in the present embodiment is that, on the runner axial surface, the distance of the high pressure side 4 along the X axis to the Z axis is s, s is the distance from the peak to the trough of the concave-convex node airfoil, and the value range thereof needs to satisfy 0.5‰D < s < 2t, wherein D is the diameter of the runner high pressure side, t is the maximum thickness value of the runner blade 3, and the Z axis is the rotation axis of the runner. The other structural connection relationships are the same as those in the third specific implementation.

[0031] Specific implementation five: combination Figure 6 and Figure 7 The present embodiment is described, and the S characteristic optimization method of the mixed-flow pump turbine runner given in the present embodiment is that, on the runner axial surface, the value range of the distance g1 of the starting point of the concave-convex node airfoil to the intersection point of the high pressure side 4 and the upper crown 1 along the Z axis needs to satisfy g1 < 0.2b, wherein b is the total height of the high pressure side. The other structural connection relationships are the same as those in the fourth specific implementation.

[0032] Specific implementation six: combination Figure 6 and Figure 7 The present embodiment is described, and the S characteristic optimization method of the mixed-flow pump turbine runner given in the present embodiment is that, on the runner axial surface, the value range of the distance g2 of two adjacent wave crests along the Z axis needs to satisfy L / 10 < g2 < L / 2, and the maximum value of the total height L occupied by the concave-convex node airfoil in the Z axis direction needs to satisfy L < 0.6b-g1. The other structural connection relationships are the same as those in the fifth specific implementation.

[0033] Specific implementation seven: combination Figure 5 The present embodiment is described, and the S characteristic optimization method of the mixed-flow pump turbine runner given in the present embodiment is that, in step one, the circular tube feature is a circle formed by rotating the high pressure side 4 on the blade 3 as the center and s as the radius. The other structural connection relationships are the same as those in the third specific implementation.

[0034] Working principle: when the unit is running in S area, the backflow area is formed on the upper crown 1 side of the runner inlet, and as the working condition goes deep into the braking area, the backflow area gradually develops to the lower ring 2 side. By adding the concave-convex knot wing type 6 on the high pressure side of the runner inlet close to the upper crown 1 side, the range of the attack angle of the upstream flow to the runner blade inlet when the pump-turbine is running can be increased; at the same time, due to the flow separation effect, the flow lines converge to the lower concave structure along the convex structure, generating counter-direction separation vortex, which can inhibit or improve the appearance and development of the runner inlet backflow area, and then play a role in optimizing the runner S characteristic.

[0035] The above disclosed embodiments of the present application are only used to help explain the present application. The embodiments do not describe all the details, nor limit the present application to the specific embodiments described. According to the content of the present application, many modifications and changes can be made. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application.

Claims

1. A Francis pump-turbine runner S characteristic optimization method, the Francis pump-turbine runner comprising an upper crown (1), a lower ring (2) and a plurality of blades (3); the upper crown (1) is arranged above the lower ring (2), a plurality of blades (3) are arranged in the passage between the upper crown (1) and the lower ring (2), the plurality of blades (3) are arranged uniformly along the radial direction, a concave-convex knot airfoil (6) is processed on the high-pressure side (4) of each blade (3), the axial plane projection of the concave-convex knot airfoil (6) is a wave-shaped structure, the concave-convex knot airfoil (6) is linearly connected or smoothly arcuately connected with the upper crown (1) above, and the concave-convex knot airfoil (6) is linearly connected or smoothly arcuately connected with the high-pressure side (4) below, characterized in that: The method is realized according to the following steps: Step one: modeling by three-dimensional modeling software, taking the high-pressure side (4) on the blade (3) as the center, and the linear distance value s from the peak to the valley of the concave-convex knot airfoil (6) as the radius to form a circular tube feature; Step two: the circular tube of the circular tube feature intersects with the blade (3) at the middle surface (7) of the blade to form a spatial curve (8), geometric control points are set on the basis runner blade high-pressure side (4) and the spatial curve (8), and then a high-pressure side with concave-convex knots is generated by connecting lines, and the blade surface is refitted with the high-pressure side with concave-convex knots; On the runner axial surface, the distance of the high-pressure side (4) along the X-axis to the Z-axis is s, s is the distance from the peak to the valley of the concave-convex knot airfoil, and the value range thereof needs to meet 0.5‰D<s<2t, wherein D is the diameter of the runner high-pressure side, t is the maximum thickness value of the runner blade (3), and the Z-axis is the rotation axis of the runner.

2. The method for optimizing the performance of a Francis pump-turbine runner S according to claim 1, characterized in that: On the runner axial surface, the value range of the distance g1 of the starting point of the concave-convex knot airfoil to the intersection point of the high-pressure side (4) and the upper crown (1) along the Z-axis needs to meet g1<0.2b, wherein b is the total height of the high-pressure side.

3. The method for optimizing the performance of a Francis pump-turbine runner S according to claim 2, characterized in that: On the runner axial surface, the value range of the distance g2 of two adjacent peaks along the Z-axis needs to meet L / 10<g2<L / 2, and the maximum value of the total height L of the concave-convex knot airfoil in the Z-axis direction needs to meet L<0.6b-g1.

4. The method for optimizing the performance of a Francis pump-turbine runner S according to claim 1, characterized in that: In step one, the circular tube feature is a circle formed by rotating a circle with the high-pressure side (4) on the blade (3) as the center and s as the radius.

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