NL2029810B1 - Judgment Method for Cavitation Inception of Hydraulic Turbine by Combining Vibration Test and Pressure Pulsation Test - Google Patents

Judgment Method for Cavitation Inception of Hydraulic Turbine by Combining Vibration Test and Pressure Pulsation Test Download PDF

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NL2029810B1
NL2029810B1 NL2029810A NL2029810A NL2029810B1 NL 2029810 B1 NL2029810 B1 NL 2029810B1 NL 2029810 A NL2029810 A NL 2029810A NL 2029810 A NL2029810 A NL 2029810A NL 2029810 B1 NL2029810 B1 NL 2029810B1
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cavitation
pressure pulsation
amplitude
signal
test
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NL2029810A
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NL2029810A (en
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Feng Jianjun
Luo Xingqi
Zhu Guojun
Li Kang
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Univ Xian Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M7/00—Vibration-testing of structures; Shock-testing of structures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H1/00—Measuring characteristics of vibrations in solids by using direct conduction to the detector
    • G01H1/003—Measuring characteristics of vibrations in solids by using direct conduction to the detector of rotating machines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H5/00—Measuring propagation velocity of ultrasonic, sonic or infrasonic waves, e.g. of pressure waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L23/00—Devices or apparatus for measuring or indicating or recording rapid changes, such as oscillations, in the pressure of steam, gas, or liquid; Indicators for determining work or energy of steam, internal-combustion, or other fluid-pressure engines from the condition of the working fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M99/00—Subject matter not provided for in other groups of this subclass
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/20—Hydro energy

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  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Aerodynamic Tests, Hydrodynamic Tests, Wind Tunnels, And Water Tanks (AREA)

Abstract

The invention discloses a judgment method for cavitation inception of hydraulic turbine by combining vibration test and pressure pulsation test. By collecting vibration speed and pressure pulsation signals of a hydraulic turbine under different working conditions, a method forjudging cavitation incipient by using the change of first-order differences AA,- and AB,- of amplitude of vibration speed and pressure pulsation signals along with cavitation coefficient 0 is proposed for the first time. When cavitation does not occur in the turbine, the first-order differences AA,- and AB,- between vibration speed and pressure pulsation signal amplitude increase slowly with the decrease of cavitation coefficient 0. After cavitation occurs, the amplitude of vibration speed and pressure pulsation signal will be enhanced. Hence, the cavitation inception point can be found through the derivatives of the curve of the pressure pulsation and vibration amplitudes change rate.

Description

Judgment Method for Cavitation Inception of Hydraulic Turbine by Combining Vibration
Test and Pressure Pulsation Test
TECHNICAL FIELD
The invention belongs to the field of hydraulic turbine technology, and involves a judgment method for cavitation inception of hydraulic turbine by combining vibration test and pressure pulsation test.
BACKGROUND
Hydraulic energy as a clean and efficient renewable energy is extremely important in the development of China's renewable energy business, and the hydraulic turbine is the core mechanical equipment for hydropower development. In the process of its operation, cavitation is one of the factors that endanger the stability of the turbine. Cavitation is a phenomenon that causes the formation, development and collapse of a vacuole after the local pressure inside the liquid decreases below the saturation vapor pressure of the liquid. When cavitation occurs, the fluid rapidly impacts the turbine components, resulting in cavitation, luminescence, vibration and noise, etc., which in severe cases causes the turbine efficiency to decrease and the components to be stripped. Therefore, in the field of hydraulic turbine, it is important to detect the generation of cavitation phenomenon for the safe operation of hydroelectric power system.
SUMMARY
The purpose of this invention is to provide a judgment method for cavitation inception of hydraulic turbine by combining vibration test and pressure pulsation test. This method can accurately determine the cavitation inception of hydraulic turbine by vibration velocity signal and pressure pulsation signal, and solve the problem of insufficient accuracy in determining the cavitation inception in the existing detection methods.
The technical scheme adopted in the invention is a judgment method for cavitation inception of hydraulic turbine by combining vibration test and pressure pulsation test, including the following steps:
Step 1, acquiring the vibration speed and pressure pulsation signals of the hydraulic turbine by the laser vibrometer and the pressure pulsation sensor respectively to obtain the time series x(t) of the hydraulic turbine after sampling the vibration speed signal and the time series y(t) of the pressure pulsation signal after sampling the vibration speed signal;
Step 2, intercepting the sampled time series x(t) of the vibration velocity signal and the sampled time series y(t) of the pressure pulsation signal obtained in step 1, respectively, to obtain the intercepted time series x:(f) of the vibration velocity signal and y:{f) of the pressure pulsation signal,
Step 3, using the low-pass filter to filter the intercepted vibration velocity signal x4(t) and the pressure pulsation signal y1(t) to obtain the filtered vibration velocity signal x2(f) and the pressure pulsation signal yz(t); and
Step 4, repeating steps 1-3 to obtain the turbine vibration speed signal
X=( x1(t),... xi(1),..., xn(t)) and pressure pulsation signal Y=(y.(1),...yi(t},...yn (1).
Step 5, calculating the amplitude A; of the vibration velocity signal X=(xi(t),...x(t),...xn(t)) and the amplitude B; of the pressure pulsation signal Y=(y:(t),...yi(t),...yn(t)) for different cavitation coefficients;
Step 6, calculating the first-order differences AA; and AB; of the amplitude of vibration velocity signal o; and the amplitude of pressure pulsation signal B; with cavitation coefficient o;, i=1,2,...N, and obtain the experimental data ((0:,4A+),(02,AA2), … (0; AA), … (On, AAN) #1 ((0+,4B1),(02,4B2), … (0; AB), … (On, ABN);
Step 7, fitting the first-order difference AA; of the amplitude of the turbine vibration velocity signal as a function of the cavitation coefficient.
Step 8, fitting the first-order difference AB; of the turbine pressure pulsation signal amplitude as a function of the cavitation coefficient.
Step 9, based on the fitting results of Step 7 and Step 8, solving for the turbine incipient cavitation coefficients to obtain cavitation coefficients oc and Oc.
Step 10, determining the cavitation coefficients of the hydraulic turbine.
The invention is also characterized in the following content: the specific process of Step 4 is as follows: constantly changing the cavitation coefficient of the hydraulic turbine, and collecting the vibration velocity signal and pressure pulsation signal of the hydraulic turbine with laser vibrometer and pressure pulsation sensor under different cavitation coefficients; repeating steps
1-3 until cavitation occurs in the hydraulic turbine, that is, bubbles appear in the hydraulic turbine, and obtaining the vibration velocity signal X=( x(t), ..., x(t), ..., xn(t)) and pressure pulsation signals Y=( y(t), ..., yt), ..., yn(t)) of the hydraulic turbine under different cavitation coefficients, where in i=0, 1, 2, ..., N.
The specific process of Step 5 is as follows:
The amplitude A; of vibration velocity signal X=0x(t),...x{t),...xn(t)) is calculated by the following formula (1):
T
DOT.
AAE
N (1); xX, is the average value of the i-th vibration speed signal sequence, and N is the number of samples. x, is the i-th vibration speed signal sequence;
The amplitude B; of pressure pulsation signal Y=( y(t), ..., yt), ..., yn(t)) adopts the following formula (2): 7
DO)
RB, =A]
N (2);
Vv is the average value of the j-th pressure pulsation signal sequence; Vl) is the i-th pressure pulsation signal sequence.
The specific process of step 6 is as follows:
The following formula (3) is used to calculate the first-order difference A; of the amplitude AA; of the vibration velocity signal varying with the cavitation coefficient:
AA: _ Aia1- A (3)
Oi+1— Oi
Wherein A; is the amplitude of the j-th vibration speed signal and A: is the amplitude of the i-th vibration speed signal; oj is the cavitation coefficient of the i-th test, and 0; is the cavitation coefficient of the i-th test;
Using the following formula (4) to calculate the first-order difference AB; between the amplitude B; of the pressure pulsation signal and the cavitation coefficient:
Bivi—Bi
AB = (4;
Oi+1 Ot wherein B; is the amplitude of the i-th pressure pulsation signal and B: is the amplitude of the B: pressure pulsation signal; c; is the cavitation coefficient of the j-th test, and 0 is the cavitation coefficient of the i-th test.
The specific process of step 7 is as follows:
Step 7.1, according to the test data ((01,444),(02,4A2),... (0, 44A),... (on, AAm)) in Step 6, the relationship ¢n between the first-order difference AA; of vibration velocity signal amplitude and cavitation coefficient is fitted according to the least square method, as shown in the following formula (5):
G1 = (5+ BT EE = 3 (ae)
J=£ (5);
In step 7.2, calculate the first derivative of the function variation relationship between the first-order difference of vibration velocity signal amplitude and cavitation coefficient fitted in step 7.1 to obtain the first-order derivative function, as shown in formula (6):
Gf = 1+ RT +t == Vig) oT (6).
The specific process of Step 8 is as follows:
Step 8.1, According to the test data in Step 6 ((0:,4B+),(02,4B2), … (0;,AB), … (On, ABn)), the least square method is used to fit the relation between the first-order difference of pressure pulsation signal amplitude AB; as a function of cavitation coefficient, as shown in formula (7) below. r= Drin + In vis + bei = > {ho } = 7)
Wherein, 2 represents the first-order difference of pressure fluctuation signal amplitude; bi is the coefficient of the term of degree j in the polynomial function, j= 1, 2, 3,..., m; mis the power of the independent variable;
In Step 8.2, calculating the first derivative of the function variation relationship 2 of the first-order difference of the pressure fluctuation signal amplitude fitted in step 8.1 with the cavitation coefficient to obtain the first-order derivative ¢:', as shown in formula (8):
©, = bb + bee = 3 he} i= (8).
The specific process of Step 9 is as follows:
Set the value of the first-order derivative function @1 of the relation formula 1 that the first-order difference of vibration velocity amplitude changes with cavitation coefficient as tan(®8), 5 substitute tan(8) into formula (6), and solve to obtain the corresponding cavitation coefficient o; as oc; In which 8 represents the angle between the tangent of the primary cavitation point C and the horizontal line on the curve ¢ of the first-order difference of vibration velocity amplitude versus cavitation coefficient;
At the same time, set the first derivative function 2 of the relation formula 2 of pressure pulsation amplitude variation with cavitation coefficient as tan(8'), and substitute tan(8') into formula (8), and solve to obtain the corresponding cavitation coefficient o; as op, wherein 8' represents the angle between the tangent of the primary cavitation point d and the horizontal line in the curve @: of pressure pulsation amplitude variation with cavitation coefficient.
The specific process of step 10 is as follows:
When |oc-0p|<0.00001, the cavitation incipient coefficient is the larger of oc and op; When oc-0p|=0.00001, the cavitation incipient coefficient is oc or op; When |oc-o5|>0.00001, the cavitation incipient coefficient is (oct+op)/2.
The method has the advantages as follows: by collecting vibration speed and pressure pulsation signals of a water turbine under different working conditions, a method for judging cavitation inception by utilizing the change of the first-order difference AA; and AB; of the amplitude of the vibration speed and pressure pulsation signals along with the cavitation coefficient sigma is firstly proposed. When cavitation does not occur in the turbine, the first-order differences AA; and AB; between vibration speed and pressure fluctuation signal amplitude increase slowly with the decrease of cavitation coefficient o. At the beginning of cavitation, the micro bubbles in the hydraulic turbine played a buffering role, which reduced the impact of water flow on the hydraulic turbine wall, resulting in lower amplitude of vibration speed and pressure pulsation signal, while when cavitation became more serious, the vibration speed and pressure pulsation signal amplitude of the hydraulic turbine would be intensified, so there was a certain law between the variation of vibration speed and pressure pulsation signal amplitude and cavitation coefficient, so the cavitation incipient point could be found through vibration test and pressure pulsation test.
BRIEF DESCRIPTION OF THE FIGURES
Fig. 1 is the algorithm flow chart of the cavitation inception judgment method of the hydraulic turbine integrating vibration test and pressure pulsation test of the invention;
Fig. 2 is the vibration signal diagram collected in the cavitation inception judgment method of the hydraulic turbine integrating vibration test and pressure pulsation test of the present invention;
Fig. 3 is the pressure pulsation signal diagram collected in the cavitation inception judgment method of hydraulic turbine integrating vibration test and pressure pulsation test of the present invention;
Fig. 4 is the variation curve of the first-order difference of vibration velocity amplitude with cavitation coefficient in the cavitation inception judgment method of hydraulic turbine integrating vibration test and pressure pulsation test of the invention;
Fig. 5 is the variation curve of the first-order difference of the pressure fluctuation amplitude with the cavitation coefficient in the hydraulic turbine cavitation inception judgment method integrating vibration test and pressure fluctuation test of the invention.
DESCRIPTION OF THE INVENTION
The invention will be described in detail below in combination with the accompanying drawings and specific embodiments.
The method for determining the cavitation inception of a hydraulic turbine by integrating vibration test and pressure pulsation test specifically comprises the following steps, and the flow is shown in Fig. 1:
Step 1: collecting the vibration velocity data of the hydraulic turbine by the laser vibrometer, and the collected vibration velocity data are sent to the console through the data acquisition card to obtain the time series x(t) after vibration velocity signal sampling; the pressure pulsation sensor is used to collect the pressure pulsation signal data of the turbine, and the collected pressure pulsation signal data are sent to the console through the data acquisition card to obtain the time series y(t) of the pressure pulsation signal after sampling.
Step 2: intercepting the time series after sampling of vibration velocity signal x(f) and pressure pulsation signal y(t) obtained in Step 1, and the intercepted time series are filtered by low-pass filter to obtain the filtered vibration velocity signal x:(f and pressure pulsation signal yi{f), as shown in Fig. 2 and Fig. 3.
Step 3: repeating step 1-2 to obtain vibration speed signal X=(xi(t),...xit),...xn(t)) and pressure pulsation signal Y=( yi(t),...y(t),... yn(t)} of hydraulic turbine under different cavitation coefficients.
Specifically, the cavitation coefficient 6=(01,02,03,...0n) of the hydraulic turbine is constantly changed, and the vibration velocity signal and pressure pulsation signal of the hydraulic turbine are collected by laser vibrometer and pressure pulsation sensor under different cavitation coefficients, and then steps 1 to 2 are repeated until cavitation occurs in the hydraulic turbine, that is, bubbles are observed inside the hydraulic turbine.
Step 4: calculating amplitude A; and B; of vibration velocity signal X=( x:(t),...x4t),... xn(t)) and pressure pulsation signal Y=( y4(1),...yit),... yn{t)) under different cavitation coefficients;
The formula for calculating the amplitude of vibration signal and pressure pulsation signal in step 4 is as follows: 7 > 0-X 0)
Ay y (1); 7
IS yo-yo 2);
N
Step 5: calculating the first-order differences AA; and AB; between vibration velocity signal amplitude A; and pressure pulsation signal amplitude B; with cavitation coefficient o;to obtain experimental data ((o1,4A9), (02,445), ... (0, 4A), … (On, AAR) and ((0:, AB) ‚(02,AB2), … (6;,AB)), … (On, ABN).
Specific formula is as follows.
MIA 9)
Ci+1— Ci
BBB 4
Ci+1—0i
A: is the amplitude of the i-th vibration speed signal, and Ai, is the amplitude of the /+7-th vibration speed signal. c; is the cavitation coefficient of the /-th test, and 01 is the cavitation coefficient of the j+7-th test; B; is the amplitude of the ith pressure pulsation signal, and B is the amplitude of the i+7-th pressure pulsation signal.
Step 6: fitting the first-order difference of turbine vibration speed signal amplitude AA; as a function of cavitation coefficient;
Step 6. 1: according to the experimental data ((01,4A4),(02,4A5),...(0,4A),...,(0n,4A)) in
Step 5: the relationship between the first-order difference AA; of vibration velocity signal amplitude and cavitation coefficient was fitted according to the least square method, as shown in the following formula (5):
EE
Oz (i+ Meme ++ eT = + {ay = (5); wherein, ¢ represents the first-order difference of amplitude of vibration velocity signal; a; is the coefficient of the term of degree j in polynomial function; m is the power of the independent variable;
Step 6.2: calculating the first derivative of the function variation relationship between the first-order difference of vibration velocity signal amplitude and cavitation coefficient ¢n fitted in step 6.1 to obtain the first-order derivative function ¢:, as shown in formula (6): @ =De ie = 3 (igad™ = (6);
Step 7: fitting the first-order difference of the amplitude of the hydraulic turbine pressure fluctuation signal A Functional variation formula of Bi with cavitation coefficient;
Step 7.1: according to the experimental data ((0:,4B1),(02,4B2), …(0;,4B), … (On, ABn)) in step 5, the relationship between the first-order difference AB; of pressure pulsation signal amplitude and cavitation coefficient is fitted according to the least square method, as shown in
Formula (7): gibson = 37 hod 2 js (7); wherein, 92 represents the first-order difference of the amplitude of the pressure pulsation signal; 5, is the coefficient of the term of degree j in polynomial function; m is the power of the independent variable;
Step 7.2: Calculating the first derivative of the function variation relationship between the first-order difference of pressure fluctuation signal amplitude and cavitation coefficient fitted in
Step 7.1 to obtain the first-order derivative function, as shown in formula (8): ©. = balie + bee = 3 {iho i= (8);
Step 8: Solving the primary cavitation coefficient of hydraulic turbine. The specific methods are as follows:
Setting the value of the first-order derivative function ge: of the relation formula gt: that the first-order difference of vibration velocity amplitude changes with cavitation coefficient as tan(8), substitute tan(B) into formula (8), and solve to obtain the corresponding cavitation coefficient 0; as oc; In which 8 represents the angle between the tangent of the primary cavitation point C and the horizontal line on the curve ¢ of the first-order difference of vibration velocity amplitude versus cavitation coefficient as shown in Fig. 4;
At the same time, set the first derivative function 2 of the relation formula 2 of pressure pulsation amplitude variation with cavitation coefficient as tan(8'), and substitute tan(8') into formula (8), and solve to obtain the corresponding cavitation coefficient o; as op, wherein ©' represents the angle between the tangent of the primary cavitation point d and the horizontal line in the curve ¢@: of pressure pulsation amplitude variation with cavitation coefficient, as shown in
Fig. 5.
Wherein, ¢ represents the relationship between the first-order difference AA; of vibration velocity signal amplitude and cavitation coefficient, 92 represents the relationship between the first-order difference AB; of the amplitude of the pressure pulsation signal and the cavitation coefficient; IE represents the first-order derivative function of formula ¢: of the relationship between the first-order difference of vibration velocity amplitude and cavitation coefficient; 2 represents the first-order derivative function of the relationship 2 between the first-order difference of pressure fluctuation amplitude and cavitation coefficient.
Step 9: judgment of initial cavitation coefficient of hydraulic turbine:
When |o¢c-0p|<0.00001, the cavitation incipient coefficient is the larger of oc and op; When oc-0p|=0.00001, the cavitation incipient coefficient is oc or op; When |cc-0p|>0.00001, the cavitation incipient coefficient is (Cctop)/2.
The invention relates to a judgment method for cavitation inception of hydraulic turbine by combining vibration test and pressure pulsation test, which firstly proposes a method for judging cavitation incipient by utilizing the change of first-order differences AA; and AB; of amplitude of vibration speed and pressure pulsation signals along with cavitation coefficient sigma by collecting vibration speed and pressure pulsation signals of the hydraulic turbine under different working conditions. When cavitation does not occur in the turbine, the first-order differences AA; and AB; between vibration speed and pressure fluctuation signal amplitude increase slowly with the decrease of cavitation coefficient co. At the beginning of cavitation, micro bubbles in the turbine play a buffering role, which reduces the impact of water flow on the turbine wall, resulting in lower amplitude of vibration speed and pressure pulsation signal. When cavitation is further serious, the vibration speed and pressure pulsation signal amplitude of the turbine will be intensified, so there is a certain rule between the variation of vibration speed and pressure pulsation signal amplitude and cavitation coefficient, so the cavitation incipient point can be found through vibration test and pressure pulsation test.

Claims (1)

CONCLUSIESCONCLUSIONS 1. Een werkwijze voor het beoordelen van initiële cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest, met kenmerk dat de werkwijze de volgende stappen omvat: Stap 1: het verzamelen van de trillingssnelheid en drukpulsatiesignalen van de hydraulische turbine met behulp van een laser-vibrometer en een drukpulsatiesensor, om een tijdreeks x{f van de hydraulische turbine na monstername van het trillingssnelheidssignaal, en een tijdreeks y(f) van het drukpulsatiesignaal na monstername van het vibratiesnelheidssignaal te verkrijgen; Stap 2: het onderscheppen van respectievelijk de tijdreeks x(t) na monstername van het trillingssnelheidssignaal en de tijdreeks y(f) na monstername van het drukpulsatiesignaal verkregen in stap 10m een onderschepte tijdreeks x 7(f) van het trillingssnelheidssignaal en van het drukpulsatiesignaal y1(f) te verkrijgen; Stap 3: toepassen van een laagdoorlaatfilter om het onderschepte trillingssnelheids- signaal x7( en het drukpulsatiesignaal y7(f) te filteren om het gefilterde trillingssnelheidssignaal x2(t} en het drukpulsatiesignaal y2(t} te verkrijgen; Stap 4: het herhalen van stappen 1 tot en met 3 om het trillingssnelheidssignaal van de turbine X = (x4(t),....xi(t),....xn(1)) en drukpulsatiesignaal Y = (y+(t),...vi(1),...yn(1)) te verkrijgen; Stap 5: het berekenen de amplitude A; van het trillingssnelheidssignaal X=(x(t),...x(t),.. xn(t)) en de amplitude B; van het drukpulsatiesignaal Y=(y1(1),...yi(t),...yn(t)) voor verschillende cavitatie coëfficiënten; Stap 6: het berekenen van de eerste-orde verschillen AA; en AB; van de amplitude van het trillingssnelheidssignaal co; en de amplitude van het drukpulsatie signaal B; met cavitatie coëfficiënt g;, i=1,2,...N, en het verkrijgen van de experimentele gegevens ((01, AA), (02, AA), … (0; AA), … ‚(On AAN) en ((01,4B1),(02,4B2), …(0,4B), … (On, AB) ; Stap 7: het inpassen van het eerste-orde verschil AA; van de amplitude van het turbine trilling snelheid signaal als functie van de cavitatie coëfficiënt; Stap 8: het inpassen van het eerste-orde verschil AB; van de amplitude van het pulsatie signaal van de turbinedruk als functie van de cavitatie coëfficiënt; Stap 9: op basis van de aangepast berekeningsresultaten van stap 7 en stap 8, het oplossen van de initiële cavitatie coëfficiënt van de turbine om de cavitatie coëfficiënt oc en Oc te verkrijgen; Stap 10: het bepalen van de cavitatie coëfficiënt van de hydraulische turbine.CLAIMS 1. A method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test, characterized in that the method comprises the following steps: Step 1: collecting the vibration velocity and pressure pulsation signals of the hydraulic turbine using of a laser vibrometer and a pressure pulsation sensor, to obtain a time series x{f of the hydraulic turbine after sampling the vibration speed signal, and a time series y(f) of the pressure pulsation signal after sampling the vibration speed signal; Step 2: intercepting the time series x(t) after sampling the vibration speed signal and the time series y(f) after sampling the pressure pulsation signal, respectively, obtained in step 10m and an intercepted time series x 7(f) of the vibration speed signal and the pressure pulsation signal y1 (f) obtain; Step 3: applying a low-pass filter to filter the intercepted vibration velocity signal x7( and the pressure pulsation signal y7(f) to obtain the filtered vibration velocity signal x2(t} and the pressure pulsation signal y2(t}; Step 4: repeating steps 1 to 3 to determine the turbine vibration speed signal X = (x4(t),....xi(t),....xn(1)) and pressure pulsation signal Y = (y+(t),...vi (1),...yn(1)); Step 5: calculating the amplitude A; of the vibration velocity signal X=(x(t),...x(t),.. xn(t)) and the amplitude B; of the pressure pulsation signal Y=(y1(1),...yi(t),...yn(t)) for different cavitation coefficients; Step 6: calculating the first-order differences AA; and AB; of the amplitude of the vibration velocity signal co; and the amplitude of the pressure pulsation signal B; with cavitation coefficient g;, i=1,2,...N, and obtaining the experimental data ((01, AA) , (02, AA), … (0; AA), … ‚(On ON) and ((01,4B1),(02,4B2), …(0,4B), … (On, AB) ; Step 7 : fitting the first-order difference AA; of the amplitude of the turbine vibration speed signal as a function of the cavitation coefficient; Step 8: fitting the first-order difference AB; of the amplitude of the pulsation signal of the turbine pressure as a function of the cavitation coefficient; Step 9: based on the adjusted calculation results of step 7 and step 8, solving the initial cavitation coefficient of the turbine to obtain the cavitation coefficient oc and Oc; Step 10: determining the cavitation coefficient of the hydraulic turbine. 2. De werkwijze voor het beoordelen van initiéle cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest, volgens conclusie 1, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 4 als volgt is: het constant veranderen van de cavitatie coëfficiënt van de hydraulische turbine, en het verzamelen van het trillingssnelheidssignaal en het drukpulsatiesignaal van de hydraulische turbine met de laservibrometer en de drukpulsatiesensor onder verschillende cavitatiecoéfficiénten; herhalen van de stappen 1-3 totdat er cavitatie optreedt in de hydraulische turbine, dat wil zeggen dat er blaasvorming in de hydraulische turbine optreedt en het verkrijgen van het trillingssnelheidssignaal X=( x1(t), ..., xt), ..., xn(t)) en drukpulsatiesignalen Y=( y(t), ..., vit), ..., yn(t)) van de hydraulische turbine onder verschillende cavitatie coëfficiënten.2. The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test, according to claim 1, characterized in that the method comprises the following steps and the specific process of step 4 is as follows: the constant changing the cavitation coefficient of the hydraulic turbine, and collecting the vibration speed signal and the pressure pulsation signal of the hydraulic turbine with the laser vibrometer and the pressure pulsation sensor under different cavitation coefficients; repeating steps 1-3 until cavitation occurs in the hydraulic turbine, that is, bubble formation occurs in the hydraulic turbine and obtaining the vibration speed signal X=( x1(t), ..., xt), .. ., xn(t)) and pressure pulsation signals Y=( y(t), ..., vit), ..., yn(t)) of the hydraulic turbine under different cavitation coefficients. 3. De werkwijze voor het beoordelen van initiële cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest volgens conclusie 2, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 5 als volgt is: het berekenen van de amplitude A; van het trillingssnelheidssignaal X=(xi(t),... xi(t),... xn(t)) met de volgende formule (1): 7The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test according to claim 2, characterized in that the method comprises the following steps and the specific process of step 5 is as follows: calculating the amplitude A; of the vibration speed signal X=(xi(t),... xi(t),... xn(t)) with the following formula (1): 7 12. XO XN A: — i=] N (1); waarbij Xx de gemiddelde waarde van de /-de trillingssnelheidssignaal volgorde is, en N staat voor het aantal monsters. x0) is de /-de trillingssnelheidssignaal volgorde; waarbij voor de amplitude B; van drukpulsatiesignaal Y={ y:(t), ..., vit), ..., yn(t)) de volgende formule(2) wordt gebruikt: 7 pt yo-yo) Bi — i=l N (2); waarbij yo de gemiddelde waarde van de /-de druk pulsatie signaal volgorde is; en yn staat voor de /-® drukpulsatiesignaal volgorde.12. XO where Xx is the average value of the /-th vibration speed signal sequence, and N represents the number of samples. x0) is the /-th vibration speed signal order; where for the amplitude B; of pressure pulsation signal Y={ y:(t), ..., vit), ..., yn(t)) the following formula(2) is used: 7 pt yo-yo) Bi — i=l N (2 ); where yo is the average value of the /-th pressure pulsation signal sequence; and yn represents the /-® pressure pulsation signal sequence. 4. De werkwijze voor het beoordelen van initiële cavitatie van een hydraulische turbine door het combineren van een ftrillingstest en een drukpulsatietest volgens conclusie 3, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 6 als volgt is: het toepassen van de volgende formule (3) om het verschil van de eerste orde A; van de amplitude AA; van het trillingssnelheidssignaal variërend met de cavitatie coéfficiént te berekenen: Ad, = Aiv1— Ai Oi+1=0i (3); waarbij A; de amplitude van de i-* trillingssnelheid signaal is en A+ de amplitude van het i- trillingssnelheidssignaal is; o; staat voor de cavitatie coëfficiënt van de j-% test, en gj staat voor de cavitatie coëfficiënt van de j-% test; het berekenen met behulp van de volgende formule: (4) van het verschil van de eerste orde AB; tussen de amplitude B; van het drukpulsatiesignaal en de cavitatie coëfficiënt : AB — Bis1- B: Ci+1-0 (4); waarbij B; de amplitude van de i-%¢ druk pulsatie signaal is en B: de amplitude van de B: druk pulsatie signaal is; o; staat voor de cavitatie coëfficiënt van de j-% test, en 01 staat voor de cavitatie coëfficiënt van de /-® test.The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test according to claim 3, characterized in that the method comprises the following steps and the specific process of step 6 is as follows: applying the following formula (3) to find the first order difference A; of the amplitude AA; of the vibration speed signal varying with the cavitation coefficient to calculate: Ad, = Aiv1— Ai Oi+1=0i (3); where A; is the amplitude of the i-* vibration speed signal and A+ is the amplitude of the i- vibration speed signal; O; represents the cavitation coefficient of the j-% test, and gj represents the cavitation coefficient of the j-% test; calculating using the following formula: (4) the first order difference AB; between the amplitude B; of the pressure pulsation signal and the cavitation coefficient: AB — Bis1- B: Ci+1-0 (4); where B; is the amplitude of the i-%¢ pressure pulsation signal and B: the amplitude of the B: pressure pulsation signal is; O; represents the cavitation coefficient of the j-% test, and 01 represents the cavitation coefficient of the /-® test. 5. De werkwijze voor het beoordelen van initiële cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest conclusie 4, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 7 als volgt is: in stap 7.1, het volgens de testgegevens ((0:,AA:),(02,AA2), … (0; AA), … ‚{On, AAn)) in Stap 6, inpassen van de relatie ¢n tussen het eerste-orde verschil AA; van trillingssnelheid signaal amplitude en cavitatie coëfficiënt volgens de kleinste kwadratenmethode, zoals weergegeven in de volgende formule (5): Piz COT + TE + der = (aai 3 = (5); in stap 7.2, het berekenen van de eerste afgeleide van de functievariatierelatie tussen het eerste-orde verschil van trillingssnelheid signaalamplitude en cavitatiecoéfficiént die in stap 7.1 om de eerste-orde afgeleide functie te verkrijgen, zoals weergegeven in formule (6): @, = m+ 2m + rma = (aos) i= (6).5. The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test claim 4, characterized in that the method comprises the following steps and the specific process of step 7 is as follows: in step 7.1, according to the test data ((0:,AA:),(02,AA2), … (0; AA), … '{On, AAn)) in Step 6, fitting the relationship ¢n between the first-order difference AA; of vibration velocity, signal amplitude and cavitation coefficient according to the least square method, as shown in the following formula (5): Piz COT + TE + der = (aai 3 = (5); in step 7.2, calculate the first derivative of the function variation relation between the first-order difference of vibration speed, signal amplitude and cavitation coefficient used in step 7.1 to obtain the first-order derivative function, as shown in formula (6): @, = m+ 2m + rma = (aos) i= (6). 6. De werkwijze voor het becordelen van initiële cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest volgens conclusie 5, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 8 als volgt is: in stap 81, het volgens de testgegevens in stap 6 ((0:,4B%, (02,4B2), …(6,4B),… (on, AB), toepassen van de kleinste kwadraten methode om de relatie tussen het eerste-orde verschil van drukpulsatiesignaal amplitude AB; in te passen als functie van de cavitatiecoéfficiént, zoals weergegeven in onderstaande formule (7); gr= ber hig ae ++ Der = 3 hoy =e (7); waarbij 2 staat voor het eerste-orde verschil van de amplitude van het drukfluctuatiesignaal;; 2; staat voor de coëfficiënt van de term van graad j in de polynoom functie, j= 1, 2, 3,..., m; M staat voor de macht van de onafhankelijke variatie; in stap 8.2, het berekenen van de eerste afgeleide van de functievariatierelatie ¢: van het eerste-orde verschil van de amplitude van het drukfluctuatiesignaal ingepast in stapThe method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test according to claim 5, characterized in that the method comprises the following steps and the specific process of step 8 is as follows: in step 81 , according to the test data in step 6 ((0:,4B%, (02,4B2), …(6,4B),… (on, AB), applying the least squares method to determine the relationship between the first-order difference of pressure pulsation signal amplitude AB; to be fitted as a function of the cavitation coefficient, as shown in formula (7) below; gr= ber hig ae ++ Der = 3 hoy =e (7); where 2 stands for the first-order difference of the amplitude of the pressure fluctuation signal;; 2; represents the coefficient of the term of degree j in the polynomial function, j= 1, 2, 3,..., m; M represents the power of the independent variation; in step 8.2, calculating the first derivative of the function variation relation ¢: of the first-order difference of the amplitude of the pressure fluctuation signal fitted in step 8.1 met de cavitatie coëfficiënt om de eerste-orde afgeleide ¢:' te verkrijgen, zoals weergegeven in formule (8): @, =D nbr = 3 {ih ei 3 = (8).8.1 with the cavitation coefficient to obtain the first-order derivative ¢:', as shown in formula (8): @, =D nbr = 3 {ih ei 3 = (8). 7. De werkwijze voor het beoordelen van initiële cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest volgens conclusie 6, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap 9 als volgt is: het instellen van de waarde van de afgeleide functie van de eerste orde 9: van de relatieformule ‘9: zodat het eerste-orde verschil van trillingssnelheidsamplitude verandert met cavitatie coëfficiënt als tan(8), het substitueren van tan(8) in formule (6), en oplossen om de bijbehorende cavitatiecoéfficiént o; als oc te verkrijgen; waarbij @ de hoek voorstelt tussen de raaklijn van het primaire cavitatiepunt C en de horizontale lijn op de curve ¢ van het eerste-orde verschil van trillingssnelheidsamplitude versus cavitatie coëfficiënt; het tegelijkertijd instellen van de eerste afgeleide-functie ©: van de relatieformule 2 van drukpulsatie amplitudevariatie met cavitatiecoéfficiént als tan{8'), en het substitueren van tan(8') in formule (8), en oplossen om de bijbehorende cavitatie coëfficiënt a; als op te verkrijgen, waarbij 8' staat voorde hoek tussen de raaklijn van het primaire cavitatiepunt d en de horizontale lijn in de curve @: van drukpulsatie amplitude variatie met cavitatie coéfficiént.The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test according to claim 6, characterized in that the method comprises the following steps and the specific process of step 9 is as follows: setting the value of the derivative function of the first order 9: of the relationship formula '9: so that the first-order difference of vibration velocity amplitude changes with cavitation coefficient as tan(8), substituting tan(8) in formula (6), and solve to find the corresponding cavitation coefficient o; available as oc; where @ represents the angle between the tangent of the primary cavitation point C and the horizontal line on the curve ¢ of the first-order difference of vibration velocity amplitude versus cavitation coefficient; simultaneously setting the first derivative function ©: of the relation formula 2 of pressure pulsation amplitude variation with cavitation coefficient as tan{8'), and substituting tan(8') in formula (8), and solving to get the corresponding cavitation coefficient a ; as to obtain, where 8' represents the angle between the tangent of the primary cavitation point d and the horizontal line in the curve @: of pressure pulsation amplitude variation with cavitation coefficient. 8. De werkwijze voor het beoordelen van initiéle cavitatie van een hydraulische turbine door het combineren van een trillingstest en een drukpulsatietest volgens conclusie 7, met kenmerk dat de werkwijze de volgende stappen omvat en het specifieke proces van stap als volgt is: wanneer |G¢-0p| < 0.00001, is de initiële cavitatie coëfficiënt de grotere waarde van oc en Op; wanneer |Oc-op| = 0.00001, is de initiële cavitatie coëfficiënt gelijk aan oc of op; wanneer |oc-0p| > 0.00001, is de initiële cavitatie coëfficiënt is (oc+op)/2.8. The method for assessing initial cavitation of a hydraulic turbine by combining a vibration test and a pressure pulsation test according to claim 7, characterized in that the method comprises the following steps and the specific process of step is as follows: when |G¢ -0p| < 0.00001, the initial cavitation coefficient is the larger value of oc and Op; when |Oc-on| = 0.00001, the initial cavitation coefficient is oc or op; when |oc-0p| > 0.00001, the initial cavitation coefficient is (oc+op)/2.
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