Device and method for observing internal flow of runner of mixed-flow water turbine

Abstract

The invention discloses a mixed-flow water turbine runner internal flow observation device and observation method, and the device comprises identifiable silk threads which are disposed in an inlet flow field and an outlet flow field of a runner of a mixed-flow water turbine; the device comprises an inlet flow field, a visual top cover, a visual window, and a first camera shooting assembly which is arranged at the visual top cover, is connected with an endoscope extending to the visual top cover, and is used for shooting recognizable silk threads at the inlet flow field, and a second camera shooting assembly which is arranged at the visual top cover, is connected with an endoscope extending to the visual top cover, and is used for shooting the recognizable silk threads at the inlet flow field; and the second camera shooting assembly is arranged at the visual window and is used for shooting the recognizable silk threads at the outlet flow field. The observation device can effectively observe the flow characteristics of the flow field in the runner of the mixed-flow water turbine, and the whole observation device is simple in structure, easy to install and use, low in cost, low in requirement for the measurement environment and convenient to implement and popularize.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic machinery visualization, and in particular to a device and method for observing the internal flow of a Francis turbine runner. Background Art

[0002] Francis turbine is the most widely used hydroelectric power generation device at present, and its power generation accounts for 60% of the global hydroelectric power generation. In recent years, new renewable energy sources (such as solar energy, wind energy and tidal energy) have been vigorously developed. Due to the intermittent characteristics of this type of new energy mode, higher requirements are placed on the peak and frequency regulation of the power grid. In order to maintain the stability of the power grid system, hydroelectric generators need to operate frequently under non-design conditions. When the unit is operating under non-design conditions, complex flows such as vortices will form inside it, which seriously affect the safe, stable and efficient operation of the unit. It is very necessary to further carry out the internal flow analysis of the unit, which has important reference value for optimizing, ensuring the safety of unit operation and improving the unit design scheme. At present, the internal flow analysis of the unit is usually carried out by numerical simulation method. This method can present the internal flow characteristics of the unit more comprehensively, but its reliability and accuracy need to be further verified; the experimental method is relatively complex to observe the internal flow characteristics of the unit, but it can provide an important reference for the verification of numerical calculation results. Conventional flow field measurement methods include: particle image velocimetry technology and Doppler velocimeter. The above method is relatively expensive and has high requirements on the measurement environment, etc. In addition, due to the compactness of the Francis turbine structure and the rotation characteristics of the runner, the above method is difficult to apply to the observation test of the flow inside the runner.

[0003] In summary, there is a lack of a visualization method in this field that is low-cost, has low requirements on the measurement environment, and is applicable to the flow inside the impeller. Summary of the invention

[0004] The purpose of the present invention is to provide a device and method for observing the internal flow of a Francis turbine runner in view of the problems existing in the prior art.

[0005] To achieve the above object, the technical solution adopted by the present invention is: A device for observing the internal flow of a Francis turbine runner, comprising: An identifiable thread, wherein the identifiable thread is arranged in the region where the inlet flow field and the outlet flow field of the runner of the Francis turbine are located; A visualization top cover, wherein the visualization top cover is arranged on the top of the runner of the Francis turbine; A visualization window, wherein the visualization window is arranged at the tailwater cone of the Francis turbine; A first camera assembly, which is disposed at the visualization top cover and connected to an endoscope extending to the visualization top cover, and is used to photograph identifiable threads at the inlet flow field; A second camera assembly is arranged at the visualization window and is used for photographing the identifiable silk thread at the outlet flow field.

[0006] The internal flow observation device for a mixed flow turbine runner can effectively observe the flow characteristics of the internal flow field of a mixed flow turbine runner through the arrangement of the identifiable silk thread, the visualization top cover, the visualization window and the camera assembly. Moreover, the entire observation device has a simple structure, is easy to install and use, has a low cost, has low requirements for the measurement environment, and is easy to implement and promote.

[0007] The setting of the identifiable silk thread can display the flow characteristics of the flow field at the inlet and outlet of the rotor, and display the originally invisible flow characteristics of the water flow in the form of silk threads, so that the camera component can photograph it to form an observable and recordable feature; the posture of the identifiable silk thread can reflect the flow characteristics of the inlet and outlet of the rotor.

[0008] The visualization top cover replaces the metal top cover originally arranged above the runner, so that the runner inlet flow field area can be observed from above the runner. This replacement only changes the material of the top cover, and there is no need to add or reduce other parts. The installation of the visualization top cover can be completed according to the existing disassembly and assembly methods.

[0009] The visualization window is arranged at the tailwater cone, and the flow field at the runner outlet can be observed from below. This position has a good field of view and is not easily blocked. The arrangement is also relatively simple, and the original metal cover can be replaced with the visualization window.

[0010] Furthermore, the runner includes a runner upper crown and a runner lower ring, and a plurality of runner blades arranged between the runner upper crown and the runner lower ring, and a plurality of fluid channels are formed, the area of ​​the fluid channel close to the periphery is the inlet flow field, and the area close to the center is the outlet flow field, and 1 to 2 of the fluid channels are selected to arrange the identifiable silk threads respectively.

[0011] Furthermore, the identifiable thread at the inlet flow field is connected to the inlet of the runner lower ring; the identifiable thread at the outlet flow field is connected to the pressure surface side of the runner blade, and the tail end of the identifiable thread at the outlet flow field does not exceed the outlet end surface of the runner blade.

[0012] Furthermore, the identifiable thread is a fluorescent thread, and one end of the identifiable thread is connected to the rotating wheel by gluing.

[0013] Furthermore, the fluorescent thread is a cotton thread with a diameter of 0.1 to 0.5 mm that has been treated with fluorescence.

[0014] Furthermore, the identifiable threads arranged at the inlet flow field are arranged at intervals of 3 to 10 mm between adjacent threads and have a length of 10 to 30 mm.

[0015] Furthermore, the identifiable threads arranged at the outlet flow field are arranged at intervals of 3 to 10 mm between adjacent threads and have a length of 20 to 60 mm.

[0016] Furthermore, the first camera assembly and the second camera assembly both include a camera and a stroboscopic light source, the stroboscopic light source having a stroboscopic frequency consistent with the rotation frequency of the rotating wheel, so that the camera can clearly capture the identifiable thread when the rotating wheel rotates to a shooting position.

[0017] Furthermore, a bottom ring is provided on the outer periphery of the runner, a plurality of connecting rods are arranged circumferentially on the bottom ring, the visualization top cover is installed above the connecting rods, and movable guide vanes are also provided on the connecting rods; the visualization window is provided on the outer peripheral surface of the tailwater cone pipe.

[0018] A method for observing the internal flow of a Francis turbine runner, the method comprising the following steps: Opening the Francis turbine, and arranging a plurality of the identifiable threads in the region where the inlet flow field and the outlet flow field of the runner are located; The visualization top cover is installed on the runner, and the visualization window is installed on the outer periphery of the tailwater cone; Assemble the Francis turbine, start the Francis turbine, and operate it under set working conditions; Inserting an endoscope from the outside of the Francis turbine and extending it to the visualization top cover near the outer periphery, connecting the first camera assembly to the endoscope and photographing the identifiable silk thread at the runner inlet flow field through the visualization top cover; The second camera assembly is used to photograph the identifiable silk thread at the outlet flow field of the runner through the visualization window.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The internal flow observation device of the runner of a mixed flow turbine can effectively observe the flow characteristics of the internal flow field of the runner of a mixed flow turbine through the arrangement of the identifiable silk thread, the visual top cover, the visual window and the camera assembly, and the entire observation device has a simple structure, is easy to install and use, has a low cost, has low requirements for the measurement environment, and is easy to implement and promote; 2. The arrangement of the identifiable silk thread can display the flow characteristics of the flow field at the inlet and outlet of the runner, and display the originally invisible flow characteristics of the water flow in the form of silk thread, so that the camera assembly can photograph it to form an observable and recordable feature; the identifiable silk thread is arranged at the outlet flow field and the inlet flow field, and it will change with the water flow, or flow, or swing, or twist, or entangle, or separate, etc., so as to reflect the flow characteristics of the inlet and outlet of the runner; 3. The visualization top cover replaces the metal top cover originally set above the runner, so that the runner inlet flow field area can be observed from above the runner. This replacement only changes the material of the top cover, and there is no need to add or reduce other parts. The visualization top cover can be installed according to the existing disassembly and assembly methods; 4. The visualization window is set at the tailwater cone pipe, which can observe the situation of the runner outlet flow field from the bottom up. This position has a good field of view and is not easily blocked. The setting is also relatively simple, and the original metal cover can be replaced with the visualization window; 5. The setting of the stroboscopic light source can provide a light source that can be photographed, so that the camera can clearly capture the pen shaft to shoot the identifiable silk thread, and the flash frequency of the stroboscopic light source is consistent with the rotation frequency of the runner. Whenever the runner rotates to a shooting position, the stroboscopic light source also automatically flashes to assist shooting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is an overall schematic diagram of a Francis turbine runner internal flow observation device of the present invention; Figure 2 It is a schematic diagram of arranging fluorescent threads in the region where the flow field of the runner inlet is located in the present invention; Figure 3 It is a schematic diagram of arranging fluorescent threads in the region where the outlet flow field of the runner is located according to the present invention; Figure 4 The runner inlet flow field observation result provided in the embodiment of the present invention; Figure 5 The runner outlet flow field observation result provided in the embodiment of the present invention; In the figure: 1. Visual top cover; 2. Runner; 3. Movable guide vane; 4. Visual window; 5. Camera; 6. Endoscope; 7. Stroboscopic light source; 8. Runner upper crown; 9. Runner blades; 10. Runner lower ring; 11. Identifiable silk thread; 12. Inlet flow field; 13. Outlet flow field; 14. Tailwater cone; 15. Bottom ring; 16. Connecting rod. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] like Figure 1 to Figure 3 As shown, a device for observing the internal flow of a Francis turbine runner comprises: An identifiable thread 11, wherein the identifiable thread 11 is arranged in the region where the inlet flow field 12 and the outlet flow field 13 of the runner 2 are located; A visualization top cover 1, wherein the visualization top cover 1 is arranged on the top of the runner of the Francis turbine; A visualization window 4, wherein the visualization window 4 is arranged at the tailwater cone 14 of the Francis turbine; A first camera assembly, which is disposed at the visualization top cover 1 and connected to an endoscope 6 extending to the visualization top cover 1 and is used to photograph the identifiable thread 11 at the inlet flow field 12; A second camera assembly is disposed at the visualization window 4 and is used for photographing the identifiable thread 11 at the outlet flow field 13 .

[0024] The internal flow observation device for a mixed flow turbine runner can effectively observe the flow characteristics of the internal flow field of a mixed flow turbine runner through the arrangement of the identifiable silk thread 11, the visualization top cover 1, the visualization window 4 and the camera assembly. Moreover, the entire observation device has a simple structure, is easy to install and use, has a low cost, has low requirements for the measurement environment, and is easy to implement and promote.

[0025] The setting of the identifiable thread 11 can display the flow characteristics of the flow field at the inlet and outlet of the runner, and display the originally invisible flow characteristics of the water flow in the form of a thread, so that the camera component can photograph it to form an observable and recordable feature; the identifiable thread 11 is set at the outlet flow field 13 and the inlet flow field 12, it will change with the water flow, or flow, or swing, or twist, or entangle, or separate, etc., so as to reflect the flow characteristics of the inlet and outlet of the runner.

[0026] The visualization top cover 1 replaces the metal top cover originally arranged above the runner, so that the runner inlet flow field area can be observed from above the runner 2. This replacement only changes the material of the top cover, and there is no need to add or reduce other parts. The installation of the visualization top cover can be completed according to the existing disassembly and assembly methods.

[0027] The visualization window 4 is arranged at the tailwater cone 14, and the flow field at the runner outlet can be observed from below. This position has a good field of view and is not easily blocked. The arrangement is also relatively simple, and the original metal cover can be replaced with the visualization window.

[0028] The first camera assembly and the second camera assembly are both used to photograph the identifiable thread 11 at the flow field. In practice, two sets of camera assemblies can simultaneously photograph the inlet flow field and the outlet flow field, or one set of camera assembly can photograph the inlet flow field and the outlet flow field successively.

[0029] Furthermore, the runner 2 includes a runner upper crown 8 and a runner lower ring 10, and a plurality of runner blades 9 arranged between the runner upper crown 8 and the runner lower ring 10, and form a plurality of fluid channels, the area of ​​the fluid channel close to the periphery is the inlet flow field 12, and the area close to the center is the outlet flow field 13, and 1 to 2 of the fluid channels are selected to arrange the identifiable silk threads 11 respectively.

[0030] These fluid channels are not straight and the outlet cannot be seen directly from the inlet. Therefore, the identifiable threads need to be set at the inlet flow field 12 and the outlet flow field 13 respectively. In order to be observable, the inlet and outlet of the same fluid channel are not selected to set the identifiable threads. The structures of these fluid channels are basically the same, and the characteristics of the fluid flow in each channel are also basically the same. Therefore, it is feasible to select the inlets and outlets of different fluid channels to set the identifiable threads, which can also accurately reflect their flow characteristics.

[0031] Furthermore, the identifiable thread 11 at the inlet flow field 12 is connected to the inlet of the runner lower ring 10; the identifiable thread 11 at the outlet flow field 13 is connected to the pressure surface side of the runner blade 9, and the tail end of the identifiable thread 11 at the outlet flow field 13 does not exceed the outlet end surface of the runner blade 9. In this embodiment, the tail end of the identifiable thread at the outlet flow field is flush with the outlet end surface of the runner blade.

[0032] Furthermore, the identifiable thread 11 is a fluorescent thread, and one end of the identifiable thread 11 is connected to the rotating wheel 2 by gluing.

[0033] Preferably, the fluorescent thread is a fluorescent-treated cotton thread with a diameter of 0.1 to 0.5 mm.

[0034] Furthermore, the identifiable threads 11 arranged at the inlet flow field 12 are arranged at intervals of 3 to 10 mm between adjacent threads and have a length of 10 to 30 mm. The length is arranged inwardly along the inlet direction of the fluid channel, and the interval can be calculated according to the spacing between the pasted ends.

[0035] Furthermore, the identifiable threads 11 arranged at the outlet flow field 13 are arranged at intervals of 3 to 10 mm between adjacent threads, have a length of 20 to 60 mm, and are arranged along the pressure surface of the runner blade toward the outlet of the fluid channel.

[0036] Furthermore, the first camera assembly and the second camera assembly both include a camera 5 and a stroboscopic light source 7, and the stroboscopic light source 7 has a stroboscopic frequency that is consistent with the rotation frequency of the rotating wheel 2. The camera can be used to continuously shoot instead of intermittently.

[0037] The setting of the stroboscopic light source 7 can provide a light source for filming, so that the camera can clearly capture the pen holder and film the identifiable silk thread. For the assembled Francis turbine, the interior is dark and the visibility is relatively low, and an external light source is required to increase visibility. In addition, the position of the camera is relatively fixed, and the area that can be observed is limited. In addition, the runner rotates continuously after starting. In order to allow the camera to clearly film the identifiable silk thread when the runner rotates to a filmable position, the flash frequency of the stroboscopic light source is consistent with the rotation frequency of the runner, that is, whenever the runner rotates to a filmable position, the stroboscopic light source also automatically flashes to assist filming.

[0038] Furthermore, a mark, such as a number, may be provided at the fluid channel of the rotating wheel so that when photographing, it is possible to know which fluid channel it is.

[0039] Furthermore, a bottom ring 15 is provided on the outer periphery of the runner 2, and a plurality of connecting rods 16 are arranged circumferentially on the bottom ring 15. The visualization top cover 1 is installed above the connecting rods 16, and movable guide vanes 3 are also provided on the connecting rods 16; the visualization window 4 is provided on the outer peripheral surface of the tailwater cone 14.

[0040] In this embodiment, the visualization top cover 1 may be a transparent tempered glass top cover, and the visualization window 4 may be a transparent tempered glass window.

[0041] A method for observing the internal flow of a Francis turbine runner, the method comprising the following steps: Open the Francis turbine, and arrange a plurality of identifiable threads 11, that is, the fluorescent threads, in the inlet flow field and the outlet flow field of the runner 2 respectively; The visualization cover 1 is installed on the runner 2, and the visualization window 4 is installed on the outer periphery of the tailwater cone 14; Assemble the Francis turbine, start the Francis turbine, and operate it under set working conditions; Insert the endoscope 6 from the outside of the mixed flow turbine and extend it to the visualization top cover 1 near the periphery, connect the first camera assembly to the endoscope 6 to photograph the identifiable silk thread 11 at the runner inlet flow field 12 through the visualization top cover 1; since the assembled mixed flow turbine also has other components, the runner makes it difficult to photograph its internal components directly using a camera, so the endoscope is set to enter through a channel on the body, so that the external camera can photograph the runner under the visualization top cover, and its stroboscopic light source can be integrated at the end of the endoscope for lighting.

[0042] By using the second camera assembly, the identifiable silk thread 11 at the outlet flow field 13 of the runner can be photographed directly through the visualization window 4, and the operation is relatively simple. Example 1

[0043] The top cover of the mixed flow turbine is made of transparent organic glass material, and the tailwater cone 14 has a transparent window, and the window area is made of organic glass material. 0.2mm cotton fluorescent thread (identifiable thread 11) is evenly arranged in the inlet and outlet areas of the runner 2. The length of the cotton fluorescent thread (identifiable thread 11) in the inlet flow field area of ​​the runner 2 is L=20mm, and its head is pasted on the inlet of the lower ring 10 of the runner, and the cotton fluorescent thread is arranged at an interval of W=5mm. The length of the cotton fluorescent thread (identifiable thread 11) in the outlet flow field area of ​​the runner is L=40mm, and its head is pasted on the pressure side of the runner blade 9. The tail of the cotton fluorescent thread is flush with the outlet of the runner blade 9, and the cotton fluorescent thread is arranged at an interval of W=5mm.

[0044] Further adopting the above-mentioned specific implementation method to carry out the runner inlet and outlet flow field observation test when the turbine unit is running under partial load condition has demonstrated the feasibility of the present invention.

[0045] a. Start the Francis turbine and make the unit operate under the set working conditions; b. Using a camera-equipped endoscope 6 to shoot the inlet flow field of the runner 2 through the transparent top cover (visualized top cover 1), using a stroboscopic light source 7 for lighting, setting the stroboscopic light source 7 to have the same stroboscopic frequency as the runner 2; c. Use camera 5 to shoot the outlet flow field of runner 2 through the transparent window (visualization window 4) of tailwater cone 14, use stroboscopic light source 7 for lighting, and set the stroboscopic light source 7 to have the same stroboscopic frequency as the rotation frequency of runner 2.

[0046] Figure 4 The results of the runner inlet flow field observation show that when the unit is running at partial load, obvious flow separation occurs on the pressure side of the runner inlet blades. Figure 5 The results of the runner outlet flow field observation show that when the unit is running at partial load, an obvious blade vortex structure is formed at the runner outlet, which is located near the lower ring of the runner blade outlet, accompanied by the twisting and winding of fluorescent threads. The above results fully demonstrate that the runner internal flow observation device and method provided in the present invention can effectively observe the flow characteristics of the runner inlet and outlet.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A Francis turbine runner internal flow observation device, characterized in that: include: An identifiable thread, wherein the identifiable thread is arranged in the region where the inlet flow field and the outlet flow field of the runner of the Francis turbine are located; A visualization top cover, wherein the visualization top cover is arranged on the top of the runner of the Francis turbine; A visualization window, wherein the visualization window is arranged at the tailwater cone of the Francis turbine; A first camera assembly, which is disposed at the visualization top cover and connected to an endoscope extending to the visualization top cover, and is used to photograph identifiable threads at the inlet flow field; A second camera assembly is arranged at the visualization window and is used for photographing the identifiable silk thread at the outlet flow field.

2. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: The runner includes a runner upper crown and a runner lower ring, and a plurality of runner blades arranged between the runner upper crown and the runner lower ring, and a plurality of fluid channels are formed, wherein the area of ​​the fluid channel close to the periphery is the inlet flow field, and the area close to the center is the outlet flow field, and 1 to 2 of the fluid channels are selected to arrange the identifiable silk threads respectively.

3. The Francis turbine runner internal flow observation device according to claim 2, characterized in that: The identifiable thread at the inlet flow field is connected to the inlet of the runner lower ring; the identifiable thread at the outlet flow field is connected to the pressure surface side of the runner blade, and the tail end of the identifiable thread at the outlet flow field does not exceed the outlet end surface of the runner blade.

4. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: The identifiable thread is a fluorescent thread, and one end of the identifiable thread is connected to the rotating wheel by gluing.

5. The Francis turbine runner internal flow observation device according to claim 4, characterized in that: The fluorescent silk thread is a cotton silk thread with a diameter of 0.1 to 0.5 mm after being treated with fluorescence.

6. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: The identifiable threads arranged at the inlet flow field are arranged at intervals of 3 to 10 mm between adjacent threads and have a length of 10 to 30 mm.

7. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: The identifiable threads arranged at the outlet flow field are arranged at intervals of 3 to 10 mm between adjacent threads and have a length of 20 to 60 mm.

8. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: The first camera assembly and the second camera assembly both include a camera and a stroboscopic light source, and the stroboscopic frequency of the stroboscopic light source is consistent with the rotation frequency of the rotating wheel.

9. The Francis turbine runner internal flow observation device according to claim 1, characterized in that: A bottom ring is provided on the outer periphery of the runner, and a plurality of connecting rods are arranged circumferentially on the bottom ring. The visualization top cover is installed above the connecting rods, and movable guide vanes are also provided on the connecting rods. The visualization window is provided on the outer peripheral surface of the tailwater cone.

10. The observation method of the Francis turbine runner internal flow observation device according to any one of claims 1 to 9, characterized in that: The observation method comprises the following steps: Opening the Francis turbine, and arranging a plurality of the identifiable threads in the region where the inlet flow field and the outlet flow field of the runner are located; The visualization top cover is installed on the runner, and the visualization window is installed on the outer periphery of the tailwater cone; Assemble the Francis turbine, start the Francis turbine, and operate it under set working conditions; Inserting an endoscope from the outside of the Francis turbine and extending it to the visualization top cover near the outer periphery, connecting the first camera assembly to the endoscope and photographing the identifiable silk thread at the runner inlet flow field through the visualization top cover; The second camera assembly is used to photograph the identifiable silk thread at the outlet flow field of the runner through the visualization window.

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