CN111350675A - Quantitative measurement system for hydraulic damping ratio of rotary centrifugal impeller - Google Patents
Quantitative measurement system for hydraulic damping ratio of rotary centrifugal impeller Download PDFInfo
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- CN111350675A CN111350675A CN202010162965.6A CN202010162965A CN111350675A CN 111350675 A CN111350675 A CN 111350675A CN 202010162965 A CN202010162965 A CN 202010162965A CN 111350675 A CN111350675 A CN 111350675A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
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Abstract
The invention relates to the technical field of the operation stability of hydraulic machinery, and discloses a quantitative measurement system of a hydraulic damping ratio of a rotary centrifugal impeller, which comprises a signal generator and an excitation signal amplifier, wherein the excitation signal amplifier is electrically connected with the signal generator; the quantitative measuring device of the hydraulic damping ratio of the rotary centrifugal impeller comprises a water storage container, a variable speed motor, a slip ring and the rotary centrifugal impeller; the excitation pieces are used for exciting the rotary centrifugal impeller to vibrate along the axial direction and obtaining the response of the rotary centrifugal impeller, and the excitation and response obtaining mode can be actively controlled; and the response signal processor can fit and calculate the slip ring output signal transmitted by the acquisition card to obtain the hydraulic damping ratio. The quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller has the advantage that the hydraulic damping ratio of the centrifugal impeller can be quantitatively measured under the rotary motion.
Description
Technical Field
The invention relates to the technical field of operation stability of hydraulic machinery, in particular to a quantitative measurement system for a hydraulic damping ratio of a rotary centrifugal impeller.
Background
Centrifugal pumps are widely used in the fields of agriculture, industry and domestic water supply, and have high requirements on the service life and the operation stability of impellers. When the centrifugal pump operates at a high speed, severe abnormal vibration may occur under a certain condition. To avoid such vibrations, it is necessary to predict the vibrations accurately in the design phase. Additional damping is a key input parameter to this pump type vibration prediction, with the hydraulic damping ratio being the most critical.
The internal flow regime of a rotating centrifugal impeller is much more complex than the non-rotating uniform flow conditions. Under the influence of dynamic and static interference, cavitation under non-design working conditions, rotating stall and the like, the centrifugal impeller inevitably generates forced vibration and even induces resonance, so that the impeller is damaged by fatigue in advance. To evaluate forced vibration of this pump type, it is particularly important to obtain a hydraulic damping ratio in a rotating environment.
At present, hydraulic damping measurement devices and methods for structures such as non-rotating hydrofoils, flat plates and cylinders are available, but the devices and methods do not involve rotation and do not need to consider signal transmission between moving and static parts. Also, for a rotating centrifugal impeller, conventional hydraulic damping ratio measurement experiments are difficult to excite and obtain a vibrational response.
Disclosure of Invention
Technical problem to be solved
The invention aims to provide a quantitative measurement system for the hydraulic damping ratio of a rotary centrifugal impeller, which aims to solve the technical problem that the hydraulic damping ratio of the centrifugal impeller cannot be quantitatively measured under rotary motion in the prior art.
(II) technical scheme
In order to solve the above technical problem, the present invention provides a system for quantitatively measuring a hydraulic damping ratio of a rotating centrifugal impeller, comprising: a signal generator; a driver signal amplifier electrically connected to the signal generator; the quantitative measuring device of the hydraulic damping ratio of the rotary centrifugal impeller comprises a water storage container, a variable speed motor arranged at the upper end of the water storage container, a slip ring arranged on an output shaft of the variable speed motor and the centrifugal impeller arranged on the output shaft of the variable speed motor; the excitation sheets are arranged on the rotary centrifugal impeller, are electrically connected with the slip ring, are used for exciting the rotary centrifugal impeller to vibrate along the axial direction and acquiring the response of the rotary centrifugal impeller, and can actively control excitation and response acquisition modes; the response signal processor can fit and calculate slip ring output signals transmitted by the acquisition card to obtain the hydraulic damping ratio.
The quantitative measuring device for the hydraulic damping ratio of the rotary centrifugal impeller further comprises a cover plate arranged at the upper port of the water storage container and a supporting seat arranged on the cover plate, and the variable speed motor is arranged on the supporting seat.
The supporting seat is a cover body with a downward opening, the lower edge of the cover body is fastened on the cover plate, the variable speed motor comprises a variable speed motor body arranged on the upper end surface of the top wall of the cover body, and the output shaft sequentially penetrates through the top wall of the cover body and the cover plate from top to bottom and extends into the bottom of the water storage container; the slip ring is disposed within the housing.
The quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller further comprises a flow guide cavity with an opening at the upper end, a flanging extending towards the outer side is formed at the opening part of the flow guide cavity, and the flanging is arranged on the lower end face of the cover plate through a fastening piece; a plurality of first diversion holes are formed on the peripheral side wall of the diversion cavity body at intervals along the circumferential direction, a plurality of second diversion holes are formed on the bottom wall of the diversion cavity body at intervals,
a cylinder body extending towards the bottom wall direction of the water storage container is constructed on the bottom wall of the diversion cavity, an upper end opening of the cylinder body is arranged at the periphery of each second diversion hole, a lower end opening of the cylinder body is arranged at the periphery of an upper end opening of an upper cover plate of the rotary centrifugal impeller, a lower cover plate of the rotary centrifugal impeller is fixed on the output shaft, the upper cover plate is connected with the lower cover plate through blades, and a liquid outflow channel is constructed between the upper cover plate and the lower cover plate;
the liquid in the water storage container can flow into the diversion cavity through the first diversion hole and flow out of the cylinder body through the second diversion hole, and the liquid in the cylinder body enters the rotary centrifugal impeller and flows out of the water storage container through the liquid outflow channel.
Wherein, a first wire groove is axially formed on the output shaft; a second line groove, an arc-shaped line dividing groove communicated with the second line groove and a groove communicated with the arc-shaped line dividing groove are respectively formed on the surface of the lower cover plate facing the bottom wall of the water storage container, the corresponding exciting sheet is embedded in the groove, and the first line groove is communicated with the second line groove; two solder point grooves are respectively formed in the grooves.
The positive electrode and the negative electrode of the connecting wire in the second wire groove are separated, a wire dividing element is formed between the arc wire dividing groove and the groove, the wire dividing element is constructed into a semi-cylinder, the diameter of the semi-cylinder is consistent with the width between the two welding point grooves, and the diameter direction of the semi-cylinder is parallel to the connecting line direction of the two welding point grooves.
After the vibration mode of the Nth-order mode is found, a large displacement area of the lower surface of the lower cover plate is positioned, the displacement of the vibration mode is subjected to non-dimensionalization, an area with the absolute value of the non-dimensionalized displacement larger than 2/3 is found, the number of the large displacement areas is j, and j is a positive integer; when j is more than or equal to 1 and less than or equal to 3, a groove is formed on the surface of each large displacement area, and 3j grooves are formed on the surface of the rotary centrifugal impeller according to the interval angle of 360 DEG/4 j in a circumferential interval angle distribution mode; when j is more than or equal to 4 and less than or equal to 10, a groove is formed on the surface of each large displacement area, and j grooves are formed on the surface of the rotary centrifugal impeller according to the interval angle of 360 DEG/2 j in a circumferential interval angle distribution mode; when j is more than or equal to 11, a groove is formed on the surface of each large displacement area.
The vibration exciting sheets are respectively welded with corresponding connecting wires, welding spots formed between the vibration exciting sheets and the connecting wires are embedded in the welding spot grooves, and the vibration exciting sheets are embedded in the grooves and are sealed by adopting insulating materials.
The vibration piece has the capability of positive and negative bidirectional work, and can actively control to generate excitation or record vibration response.
The excitation signal amplifier amplifies the voltage input to the vibration sheet to a rated range, and the excitation frequency range is as follows:
kfn≥fe≥0.1Hz，
wherein f isnIs the natural frequency of the Nth order mode in Hz, feThe unit is the excitation frequency in Hz, k is a constant and is more than or equal to 1.5;
the excitation time can be expressed as:
t≥m(1/fn)，
wherein t is the excitation time with the unit of s, 1/fnIs the vibration period of Nth order mode, m is the multiple of the vibration period of Nth order mode and is more than or equal to 100;
the sampling time coincides with the excitation time, and the sampling frequency can be expressed as:
fs≥ifn，
wherein f issIs the sampling frequency with the unit of Hz, i is the multiple of the natural frequency of the Nth order mode, and i is more than or equal to 10.
The method comprises the steps of carrying out fast Fourier transform on vibration response of 1 vibration piece and a Hanning window to obtain a frequency domain graph, finding out Nth-order natural frequency, extracting all discrete points corresponding to the Nth-order natural frequency which is 0.95-1.05 times of the frequency domain graph, fitting all the discrete points to obtain hydraulic damping ratio, and averaging the hydraulic damping ratios of at least 3 vibration pieces to obtain the final hydraulic damping ratio.
(III) advantageous effects
Compared with the prior art, the quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller provided by the invention has the following advantages:
the method comprises the steps that the inlet annular quantity of the rotary centrifugal impeller is reduced through a flow guide cavity at the specific positions of an output shaft of a variable-speed motor and a lower cover plate of the rotary centrifugal impeller, a vibration excitation sheet can work in a positive and negative direction, the vibration excitation and response acquisition mode can be actively controlled, an electric signal of an excitation signal amplifier is transmitted to the vibration excitation sheet on the rotary centrifugal impeller through a slip ring, the vibration response of the rotary centrifugal impeller acquired by the vibration excitation sheet is transmitted to an acquisition card, a vibration response frequency domain diagram is obtained in a response signal processor based on fast Fourier transform, the Nth order natural frequency is found, all discrete points of the frequency domain diagram are extracted in the range of 0.95-1.05 times of the natural frequency, hydraulic damping is identified by fitting the extracted discrete points, and the results obtained by more than 3 vibration excitation sheets are averaged to obtain the final hydraulic damping. Therefore, the quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller can quantitatively identify the hydraulic damping ratio of the centrifugal impeller in a rotary underwater environment.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a quantitative measurement system of the hydraulic damping ratio of a rotary centrifugal impeller according to an embodiment of the present invention;
FIG. 2 is a schematic view of a connection structure of the guide cavity and the cylinder in FIG. 1;
FIG. 3 is a schematic view of the connection structure of the output shaft and the slip ring in FIG. 1;
FIG. 4 is a schematic view of the lower cover plate of FIG. 1 facing the bottom wall of the reservoir;
FIG. 5 is a frequency domain signal plot of the vibration response of a quantitative measurement system of the hydraulic damping ratio of a rotating centrifugal impeller according to an embodiment of the present application;
FIG. 6 is a hydraulic damping ratio identification graph of a quantitative measurement system of a hydraulic damping ratio of a rotating centrifugal impeller according to an embodiment of the present application.
Reference numerals:
1: a signal generator; 2: a driver signal amplifier; 3: a quantitative measuring device for the hydraulic damping ratio of the rotary centrifugal impeller; 31: a water storage container; 32: a variable speed motor; 321: an output shaft; 321 a: a first wire slot; 322: a variable speed motor body; 33: a slip ring; 34: rotating the centrifugal impeller; 341: a lower cover plate; 341 a: a second wire slot; 341 b: an arc-shaped wire dividing groove; 341 c: a groove; 341 d: a solder joint groove; 342: an upper cover plate; 343: a blade; 344: a liquid outflow channel; 35: a cover plate; 36: a supporting seat; 361: a cover body; 4: a vibration-exciting sheet; 5: a response signal processor; 6: collecting cards; 7: a flow guide cavity; 71: flanging; 72: a first flow guide hole; 73: a second flow guide hole; 8: and (4) a cylinder body.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
As shown in fig. 1 to 6, the quantitative measurement system for the hydraulic damping ratio of the rotating centrifugal impeller, which is schematically shown in the figures, comprises a signal generator 1, an excitation signal amplifier 2, a quantitative measurement device 3 for the hydraulic damping ratio of the rotating centrifugal impeller, an excitation sheet 4, a response signal processor 5 and an acquisition card 6.
In the exemplary embodiment of the application, the driver signal amplifier 2 is electrically connected to the signal generator 1.
The device 3 for quantitatively measuring the hydraulic damping ratio of the rotating centrifugal impeller comprises a water reservoir 31, a variable speed motor 32 disposed at the upper end of the water reservoir 31, a slip ring 33 disposed on an output shaft 321 of the variable speed motor 32, and a rotating centrifugal impeller 34 disposed on the output shaft 321 of the variable speed motor 32.
The plurality of excitation pieces 4 are provided on the rotary centrifugal impeller 34 and electrically connected to the slip ring 33, and are used for exciting the rotary centrifugal impeller 34 to vibrate in the axial direction of the output shaft 321 and for acquiring the response of the rotary centrifugal impeller 34, and excitation and response acquisition modes can be controlled. At least 1 of the excitation plates 4 is used to excite the rotating centrifugal impeller 34, and at least 3 excitation plates are used to obtain the response of the rotating centrifugal impeller 34.
The response signal processor 5 is electrically connected with the acquisition card 6, the acquisition card 6 is electrically connected with the slip ring 33, and the response signal processor 5 can fit the slip ring output signal transmitted by the acquisition card 6 to calculate and obtain the hydraulic damping ratio. Specifically, a slip ring 33 is formed by slotting on an output shaft 321 of a variable speed motor 32 and a lower cover plate 341 of a rotary centrifugal impeller 34 to be connected with an excitation piece 4, the specific position of the installation of the excitation piece 4 is determined according to the vibration mode, the inlet ring amount of the rotary centrifugal impeller 34 is reduced through a guide cavity 7, the excitation piece 4 can work in both forward and reverse directions and can actively control the excitation and response acquisition mode, an electric signal of an excitation signal amplifier 2 is transmitted to the excitation piece 4 on the rotary centrifugal impeller 3 through the slip ring 33, the vibration response of the rotary centrifugal impeller 34 acquired by the excitation piece 4 is transmitted to an acquisition card 6, a vibration response frequency domain diagram is obtained in a response signal processor 5 based on fast Fourier transform, the Nth order natural frequency is found, all discrete points of a frequency domain diagram are extracted in the range of 0.95-1.05 times of the natural frequency, the extracted discrete points are fitted to identify the hydraulic damping, and averaging results obtained by more than 3 vibration exciting sheets 4 to obtain the final hydraulic damping ratio. Therefore, the quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller can quantitatively identify the hydraulic damping ratio of the centrifugal impeller in a rotary underwater environment.
It should be noted that the structure and the operation principle of the so-called "rotating centrifugal impeller 34" are consistent with those of the "centrifugal impeller" in the related art, and the "rotating centrifugal impeller 34" is capable of being rotated in the circumferential direction by the variable speed motor 32.
As shown in fig. 1 to 4, in a preferred embodiment of the present application, the device 3 for quantitatively measuring the hydraulic damping ratio of the rotary centrifugal impeller further comprises a cover plate 35 disposed at the upper port of the water reservoir 31, a support seat 36 disposed on the cover plate 35, and the variable speed motor 32 is disposed on the support seat 36. Specifically, the variable speed motor 32 may be fastened to the cover plate 35 by screws.
It should be noted that the rotation speed of the variable speed motor 32 is in the range of 0-2000r/min (revolutions per minute), the voltage is 200V (volts), the rotation speed of the variable speed motor 32 is adjusted by the motor control box, and the diameter of the output shaft 321 is 25mm (millimeters).
The degree of freedom of the output shaft 321 in the radial direction and the axial direction is constrained by a transmission end bearing and a non-transmission end bearing which are arranged at the upper end and the lower end of the output shaft 321, and the transmission end bearing comprises a bearing seat, two deep groove ball bearings, a spacer bush between the bearings, a sealing ring, 2 elastic check rings and a fixed snap ring.
The non-drive end bearing includes a bearing gland and a deep groove ball bearing.
The rotary centrifugal impeller 34 is mounted on the output shaft 321 by a double-thread screwing manner, the rotary centrifugal impeller 34 is made of an aluminum alloy, the inlet diameter of the rotary centrifugal impeller 34 is 100mm (mm), the outlet diameter is 300mm (mm), the outlet width is 8mm (mm), the number of blades is 5, and the specific rotation speed is 60.
As shown in fig. 1 to 4, in a preferred embodiment of the present application, the supporting seat 36 is configured as a cover 361 with an opening facing downward, a lower edge of the cover 361 is fastened to the cover plate 35, the variable speed motor 32 includes a variable speed motor body 322 disposed on an upper end surface of a top wall of the cover 361, and the output shaft 321 sequentially penetrates through the top wall of the cover 361 and the cover plate 35 from top to bottom and extends into a bottom of the water storage container 31.
The slip ring 33 is disposed within the housing 361. Specifically, the lower edge of the cover 361 may be fastened to the cover plate 35 by screws or rivets. It should be noted that the water storage container 31 contains liquid, and the water level of the liquid is higher than the level of the upper edge of the first diversion hole 72 described below.
The rotation of the output shaft 321 drives the rotating centrifugal impeller 34 to rotate, so that the liquid in the water storage container 31 is agitated by the rotation of the rotating centrifugal impeller 34, and the liquid in the water storage container 31 is stirred in the rotating direction of the rotating centrifugal impeller 34.
The slip ring 33 is an electrical component responsible for communicating with the rotating body and transmitting power and signals. The slip rings 33 are classified into electrical slip rings, fluid slip rings, and optical slip rings according to the transmission medium, and may also be commonly referred to as "rotary communication" or "rotary communication". The slip ring 33 is usually mounted at the center of rotation of the apparatus and is mainly composed of two parts, rotating and stationary. The rotating part is connected to and moves rotationally with the rotating structure of the device, called the "rotor", and the stationary part is connected to the energy source of the stationary structure of the device, called the "stator".
In a preferred embodiment of the present application, the system for quantitatively measuring the hydraulic damping ratio of the rotary centrifugal impeller further comprises a flow guide cavity 7 with an opening at the upper end, the opening part of the flow guide cavity 7 is configured with a flange 71 extending towards the outside, and the flange 71 is arranged on the lower end surface of the cover plate 35 through a fastener.
A plurality of first guiding holes 72 are formed on the circumferential side wall of the guiding cavity 7 at intervals along the circumferential direction, and a plurality of second guiding holes 73 are formed on the bottom wall of the guiding cavity 7 at intervals, wherein the liquid in the water storage container 31 can flow into the inside of the guiding cavity 7 through the first guiding holes 72 and flow out to the rotary centrifugal impeller 34 through the second guiding holes 73. Specifically, when the output shaft 321 rotates in the circumferential direction, the liquid in the water storage container 31 flows into the diversion cavity 7 through the first diversion hole 72 and flows out through the second diversion hole 73 on the bottom wall of the diversion cavity 7, so that the liquid flows into the diversion cavity 7 from the first diversion hole 72 and flows out through the second diversion hole 73 on the bottom wall of the diversion cavity 7 in a circular and reciprocating manner.
As shown in fig. 1 to 4, in a preferred embodiment of the present application, a cylinder 8 extending toward the bottom wall of the water storage container 31 is formed on the bottom wall of the flow guide cavity 7, an upper end opening of the cylinder 8 is provided at the periphery of each of the second flow guide holes 73, a lower end opening of the cylinder 8 is provided at the periphery of an upper end opening of an upper cover plate 342 of the rotary centrifugal impeller 34, a lower cover plate 341 of the rotary centrifugal impeller 34 is fixed on the output shaft 321, the upper cover plate 342 and the lower cover plate 341 are connected by a vane 343, and a liquid outflow channel 344 is formed between the upper cover plate 342 and the lower cover plate 341.
Thus, the liquid flows through the second guide holes 73, flows into the rotating centrifugal impeller 34 through the cylinder 8, and flows into the reservoir 31 through the liquid outflow passage 344.
In a preferred embodiment of the present application, a first linear groove 321a is formed on the output shaft 321 in the axial direction.
A second slot 341a, an arc-shaped slot 341b communicated with the second slot 341a, and a groove 341c communicated with the arc-shaped slot 341b are respectively formed on the surface of the lower cover plate 341 facing the bottom wall of the water reservoir 31, the corresponding exciting piece 4 is embedded in the groove 341c, and the first slot 321a is communicated with the second slot 341 a.
Two solder grooves 341d are also formed in the recesses 341 c. Specifically, electric wires are embedded in both the first wire groove 321a and the second wire groove 341a, and the slip ring 33 is electrically connected to the exciting piece 4 through the electric wires.
In a preferred embodiment of the present application, the positive and negative poles of the connection line in the second line groove 341a are separated, and a line dividing element is formed between the arc-shaped line dividing groove 341b and the groove 341c, the line dividing element is configured as a semi-cylinder, the diameter of the semi-cylinder is consistent with the width between the two welding point grooves 341d, and the diameter direction of the semi-cylinder is parallel to the connection line direction of the two welding point grooves 341 d.
The positive and negative poles of the electric wire are separated, the member surrounded by the arc-shaped dividing groove 341b is a semi-cylindrical body, the diameter of the semi-cylindrical body is equal to the width between the two welding point grooves 341d, and the diameter direction is parallel to the connecting line direction of the two welding point grooves 341 d.
This water conservancy diversion cavity 7 passes through threaded connection to be fixed on apron 35, and the internal diameter cover of barrel 8 inlays in the upper end open-ended periphery of upper cover plate 342, and the upper portion diameter of this water conservancy diversion cavity 7 is 190mm (millimeter), and is high for 86mm (millimeter), and the diameter of barrel 8 is 105mm (millimeter), and is high for 50mm (millimeter), and the centre is separated for the diapire of 14mm (millimeter) through thickness. The thickness of the diversion cavity 7 is 18mm (millimeter), the fluid flows in through 10 first diversion holes 72 with the diameter of 40mm (millimeter) on the side wall of the diversion cavity 7, and each first diversion hole 72 is distributed on the side wall according to a 36-degree circumferential angle; 12 second guide holes 73 with the diameter of 10mm (millimeter) are arranged in the bottom wall and are distributed on the circumference with the diameter of 86mm (millimeter) according to the circumferential angle of 30 degrees.
In a preferred embodiment of the present application, after the mode shape of the nth-order mode is found, a region of large displacement of the lower surface of the lower cover 341 is located, the displacement amount of the mode shape is dimensionless, and a region of which the absolute value of the dimensionless displacement amount is greater than 2/3 is found, where j is a positive integer and the number of the regions of large displacement is j.
One groove is formed on the surface of each large displacement area of the lower cover 341, and the grooves 341c are formed on the lower surface of the lower cover 341 at circumferential angular intervals according to the angular intervals.
When j is more than or equal to 1 and less than or equal to 3, a groove 341c is formed on the surface of each large displacement region of the lower cover plate 341, and 3j grooves 341c are further formed on the lower surface of the lower cover plate 341 in the circumferential interval angle distribution according to the interval angle of 360 DEG/4 j.
When j is more than or equal to 4 and less than or equal to 10, a groove 341c is formed on the surface of each large displacement region of the lower cover plate 341, and j grooves 341c are formed on the lower surface of the lower cover plate 341 in the circumferential interval angle distribution according to the interval angle of 360 DEG/2 j.
When j is more than or equal to 11, a groove 341c is formed on the surface of each large displacement area of the lower cover plate 341. Specifically, the embodiment of the present application can excite the rotary centrifugal impeller 34 and obtain a vibration response according to a specific vibration mode of each stage of the rotary centrifugal impeller 34, and can excite and obtain a vibration response more easily in a large deformation region.
As shown in fig. 4, in a preferred embodiment of the present application, each of the excitation sheets 4 is soldered to a corresponding connection line, a solder formed between the excitation sheet 4 and the connection line is embedded in the solder groove 341d, and the excitation sheet 4 is embedded in the groove 341c and sealed with an insulating material. Specifically, the excitation sheet 4 in the corresponding groove 341c is sealed by using an insulating material, so that the effect of sealing the excitation sheet 4 can be achieved on one hand, and the situation of electric leakage can be avoided on the other hand.
In a preferred embodiment of the present application, the excitation plate 4 is capable of reversible operation and is capable of active control to produce excitation or record vibrational response.
As shown in fig. 5 and 6, in a preferred embodiment of the present application, the excitation signal amplifier 2 amplifies the voltage input to the excitation plate 4 to within a rated range, and the excitation frequency range is:
kfn≥fe≥0.1Hz，
wherein f isnIs the natural frequency of the Nth order mode in Hz, feThe unit is the excitation frequency in Hz, k is a constant and is more than or equal to 1.5;
the excitation time can be expressed as:
t≥m(1/fn)，
wherein t is the excitation time with the unit of s, 1/fnIs the vibration period of Nth order mode, m is the multiple of the vibration period of Nth order mode and is more than or equal to 100;
the sampling time coincides with the excitation time, and the sampling frequency can be expressed as:
fs≥ifn，
wherein f issIs the sampling frequency with the unit of Hz, i is the multiple of the natural frequency of the Nth order mode, and i is more than or equal to 10.
In the embodiment of the present application, 4 second linear grooves 341a having a width of 2mm (mm) and a depth of 1mm (mm) are formed on the lower surface of the lower cover plate 341, the included angle between the 4 second linear grooves 341a is 90 °, the 4 th order mode shape of the rotating centrifugal impeller 34 has 1 large displacement region on the lower cover plate 341, a groove 341c is formed in the large displacement region, and 3 more grooves 341c, 1/4 are formed in the lower surface of the lower cover plate 341 so as to be circumferentially spaced at an angle of 90 degrees as shown in fig. 4, on the lower cover plate 341 of the rotary centrifugal impeller 34, 4 wire grooves with a length of 20mm (millimeter), a groove width of 2mm (millimeter) and a groove depth of 1mm (millimeter) are radially formed, and the wire dividing groove of the arc-shaped wire dividing groove 341b has a wire dividing groove width of 1mm (millimeter) and a wire dividing groove depth of 1mm (millimeter); the length of the groove for placing the vibration piece 4 is 65mm (millimeter), the width is 40mm (millimeter), and the depth is 1mm (millimeter), the diameter of the welding spot groove 341d is 3mm (millimeter), and the depth is 1mm (millimeter); the wires with positive and negative poles led out from the slip ring 33 are buried in the first wire groove 321a and the second wire groove 341a, and are separated in the arc-shaped wire dividing groove 341b, and the wires and the exciting piece 4 are completely sealed in the grooves by using an insulating material.
For impeller excitation and response signal acquisition, 4 excitation pieces 4 are placed on the lower surface of a lower cover plate 341 of the rotary centrifugal impeller 34, the interval angle between each excitation piece 4 is 90 degrees, one excitation piece 4 is used for exciting the rotary centrifugal impeller 34, and the other 3 excitation pieces 4 are used for acquiring vibration response; an external signal generator 1 controls the excitation frequency range to be 0-3000Hz, the excitation time is 30s, and the voltage range is 2-12V; the rated voltage range of the exciting sheet 4 is 20-120V, and the amplification factor of the exciting signal amplifier 2 is 10 times; the vibration response signal is acquired by the vibration exciting sheet 4 and then transmitted to the acquisition card 6, the sampling frequency of the acquisition card 6 is controlled to be 30000Hz by the response signal processor, and the recording time is 30 s.
In a preferred embodiment of the present application, a fast fourier transform is performed on the vibration response of 1 excitation plate 4 and a hanning window to obtain a frequency domain diagram and find an nth order natural frequency, all discrete points corresponding to 0.95-1.05 times of the nth order natural frequency in the frequency domain diagram are extracted, all the discrete points are fitted to obtain a hydraulic damping ratio, and the hydraulic damping ratios obtained by at least 3 excitation plates 4 are averaged to obtain a final hydraulic damping ratio.
The hydraulic damping ratio identification formula can be expressed as:
wherein U is the voltage corresponding to the discrete point, U0For voltages corresponding to natural frequencies, UrIs a relative voltage, feFor excitation frequency, fnIs the natural frequency, frζ is the hydraulic damping ratio, relative frequency.
In summary, a slip ring 33 is formed by slotting on an output shaft 321 of a variable speed motor 32 and a lower cover plate 341 of a rotary centrifugal impeller 34 to connect with an excitation plate 4, a specific position for installing the excitation plate 4 is determined according to a vibration mode, an inlet ring amount of the rotary centrifugal impeller 34 is reduced through a diversion cavity 7, the excitation plate 4 can work in both forward and reverse directions, and an excitation and response acquisition mode can be actively controlled, an electric signal of an excitation signal amplifier 2 is transmitted to the excitation plate 4 on the rotary centrifugal impeller 3 through the slip ring 33, a vibration response of the rotary centrifugal impeller 34 acquired by the excitation plate 4 is transmitted to an acquisition card 6, a vibration response frequency domain diagram is obtained in a response signal processor 5 based on fast Fourier transform, a 4 th order natural frequency is found, all discrete points of a frequency domain diagram are extracted in a range of 0.95-1.05 times of the natural frequency, and the extracted discrete points are fitted to identify hydraulic damping, and averaging results obtained by more than 3 vibration exciting sheets 4 to obtain the final hydraulic damping ratio. Therefore, the quantitative measurement system for the hydraulic damping ratio of the rotary centrifugal impeller can quantitatively identify the hydraulic damping ratio of the centrifugal impeller in a rotary underwater environment.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A system for quantitative measurement of the hydraulic damping ratio of a rotating centrifugal impeller, comprising:
a signal generator;
a driver signal amplifier electrically connected to the signal generator;
the quantitative measuring device of the hydraulic damping ratio of the rotary centrifugal impeller comprises a water storage container, a variable speed motor arranged at the upper end of the water storage container, a slip ring arranged on an output shaft of the variable speed motor and the rotary centrifugal impeller arranged on the output shaft of the variable speed motor;
the excitation sheets are arranged on the rotary centrifugal impeller, are electrically connected with the slip ring, are used for exciting the rotary centrifugal impeller to vibrate along the axial direction and acquiring the response of the rotary centrifugal impeller, and can actively control excitation and response acquisition modes; and
the response signal processor can fit and calculate slip ring output signals transmitted by the acquisition card to obtain the hydraulic damping ratio.
2. The system of claim 1, further comprising a cover plate disposed at an upper port of the reservoir, a support seat disposed on the cover plate, and the variable speed motor disposed on the support seat;
the supporting seat is a cover body with a downward opening, the lower edge of the cover body is fastened on the cover plate, the variable speed motor comprises a variable speed motor body arranged on the upper end surface of the top wall of the cover body, and the output shaft sequentially penetrates through the top wall of the cover body and the cover plate from top to bottom and extends into the bottom of the water storage container;
the slip ring is disposed within the housing.
3. The system for quantitatively measuring the hydraulic damping ratio of the rotary centrifugal impeller according to claim 2, further comprising a flow guide cavity having an opening at an upper end thereof, wherein the opening of the flow guide cavity is configured with a flange extending outward, and the flange is disposed on a lower end surface of the cover plate by a fastener;
a plurality of first guide holes are formed in the peripheral side wall of the guide cavity at intervals along the circumferential direction, a plurality of second guide holes are formed in the bottom wall of the guide cavity at intervals, a cylinder body extending towards the bottom wall direction of the water storage container is formed in the bottom wall of the guide cavity, an upper end opening of the cylinder body is arranged on the periphery of each second guide hole, a lower end opening of the cylinder body is arranged on the periphery of an upper end opening of an upper cover plate of the rotary centrifugal impeller, a lower cover plate of the rotary centrifugal impeller is fixed on the output shaft, the upper cover plate and the lower cover plate are connected through blades, and a liquid outflow channel is formed between the upper cover plate and the lower cover plate;
the liquid in the water storage container can flow into the diversion cavity through the first diversion hole and flow out of the cylinder body through the second diversion hole, and the liquid in the cylinder body enters the rotary centrifugal impeller and flows out of the water storage container through the liquid outflow channel.
4. A quantitative measurement system of the hydraulic damping ratio of a rotary centrifugal impeller according to claim 3, wherein a first wire groove is configured on the output shaft in the axial direction;
a second line groove, an arc-shaped line dividing groove communicated with the second line groove and a groove communicated with the arc-shaped line dividing groove are respectively formed on the surface of the lower cover plate facing the bottom wall of the water storage container, the corresponding exciting sheet is embedded in the groove, and the first line groove is communicated with the second line groove;
two solder point grooves are respectively formed in the grooves.
5. The system of claim 4, wherein the positive and negative poles of the connection line in the second wire slot are separated, and a wire dividing element is formed between the arc-shaped wire dividing slot and the groove, the wire dividing element is configured as a semi-cylinder, the diameter of the semi-cylinder is consistent with the width between the two welding point slots, and the diameter direction of the semi-cylinder is parallel to the connection line direction of the two welding point slots.
6. The system according to claim 5, wherein the vibration mode of the nth order mode is found, a region of large displacement of the lower surface of the lower cover plate is positioned, the displacement of the vibration mode is dimensionless, and a region of larger absolute value than 2/3 is found, the number of the regions of large displacement is j, j is a positive integer;
when j is more than or equal to 1 and less than or equal to 3, a groove is formed on the surface of each large displacement area, and 3j grooves are formed on the surface of the rotary centrifugal impeller according to the interval angle of 360 DEG/4 j in a circumferential interval angle distribution mode;
when j is more than or equal to 4 and less than or equal to 10, a groove is formed on the surface of each large displacement area, and j grooves are formed on the surface of the rotary centrifugal impeller according to the interval angle of 360 DEG/2 j in a circumferential interval angle distribution mode;
when j is more than or equal to 11, a groove is formed on the surface of each large displacement area.
7. The system of claim 6, wherein each of the vibration exciter pieces is welded to a corresponding connecting wire, a welding point formed between the vibration exciter piece and the connecting wire is embedded in the welding point groove, and the vibration exciter pieces are embedded in the grooves and sealed with an insulating material.
8. A system for quantitative measurement of the hydraulic damping ratio of a rotating centrifugal impeller according to claim 1, wherein the said exciter plate has the capability of positive and negative bi-directional operation, enabling active control of the excitation or recording of the vibrational response.
9. A system for quantitative measurement of the hydraulic damping ratio of a rotating centrifugal impeller in accordance with claim 1, wherein the excitation signal amplifier amplifies the voltage input to the excitation plate to within a nominal range, and the excitation frequency range is:
kfn≥fe≥0.1Hz，
wherein f isnIs the natural frequency of the Nth order mode in Hz, feThe unit is the excitation frequency in Hz, k is a constant and is more than or equal to 1.5;
the excitation time can be expressed as:
t≥m(1/fn)，
wherein t is the excitation time with the unit of s, 1/fnIs the vibration period of Nth order mode, m is the multiple of the vibration period of Nth order mode and is more than or equal to 100;
the sampling time coincides with the excitation time, and the sampling frequency can be expressed as:
fs≥ifn，
wherein f issIs the sampling frequency with the unit of Hz, i is the multiple of the natural frequency of the Nth order mode, and i is more than or equal to 10.
10. The system of claim 1, wherein the vibration response of 1 of the vibration plates is subjected to fast fourier transform with a hanning window to obtain a frequency domain diagram, an nth-order natural frequency is found, all discrete points corresponding to 0.95-1.05 times of the nth-order natural frequency in the frequency domain diagram are extracted, all the discrete points are fitted to obtain the hydraulic damping ratio, and the hydraulic damping ratios of at least 3 of the vibration plates are averaged to obtain the final hydraulic damping ratio.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112924154A (en) * | 2021-03-09 | 2021-06-08 | 中国农业大学 | Method and device for extracting damping ratio of structural response signal in high-noise flowing environment |
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| CN104075795A (en) * | 2014-06-18 | 2014-10-01 | 北京金风科创风电设备有限公司 | Method and system for monitoring vibration state of impeller of wind generating set |
| CN108593229A (en) * | 2018-03-26 | 2018-09-28 | 上海交通大学 | Integral impeller blade vibration measurement device and measurement method |
| CN108680322A (en) * | 2018-03-29 | 2018-10-19 | 合肥通用机械研究院有限公司 | A kind of centrifugal impeller vibration damping test system and method |
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| US4523479A (en) * | 1983-08-22 | 1985-06-18 | Cadillac Meter Company | Fluid flow measuring device |
| CN104075795A (en) * | 2014-06-18 | 2014-10-01 | 北京金风科创风电设备有限公司 | Method and system for monitoring vibration state of impeller of wind generating set |
| CN108593229A (en) * | 2018-03-26 | 2018-09-28 | 上海交通大学 | Integral impeller blade vibration measurement device and measurement method |
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| CN112924154A (en) * | 2021-03-09 | 2021-06-08 | 中国农业大学 | Method and device for extracting damping ratio of structural response signal in high-noise flowing environment |
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