Method for measuring cavitation collapse pressure and Y-shaped optical fiber probe device thereof

Abstract

The invention provides a method for measuring cavitation collapse pressure and a Y-shaped optical fiber probe device thereof, and belongs to the field of cavitation collapse pressure measurement in multiphase flow. The method for measuring the cavitation collapse pressure mainly comprises the following steps of: 1, decomposing a voltage to be measured into an average direct current component voltage and an average alternating current component voltage; 2, obtaining the relation between the measured voltage and the liquid refractive index through the relation between the measured voltage and the liquid refractive index; and step 3, obtaining a group of liquid densities according to the relationship between the measured voltage and the liquid refractive index, finally obtaining the relationship between the cavitation collapse pressure in the to-be-measured liquid and the liquid density by combining a Tit equation or looking up an IAPWS table, and further obtaining the relationship between the measured voltage and the pressure generated by cavitation collapse in the to-be-measured liquid. According to the method, the pressure generated by cavitation collapse can be measured simply, efficiently and at high frequency.

Description

Technical Field

[0001] The invention belongs to the field of cavitation collapse pressure measurement in multiphase flow, and in particular relates to a method for measuring cavitation collapse pressure and a Y-type optical fiber probe device thereof. Background Art

[0002] Cavitation collapse refers to the phenomenon that cavitation bubbles formed in liquids collapse rapidly under pressure. This process will produce extremely high local pressure and temperature, causing severe impact and erosion and damage to materials and equipment.

[0003] At present, the cavitation collapse pressure measurement technology mainly includes the following methods:

[0004] (1) Piezoelectric sensor: When the piezoelectric material inside the piezoelectric sensor is subjected to external mechanical stress (such as impact load), it generates a charge signal through the piezoelectric effect, thereby measuring the pressure change. However, the poor static measurement capability, durability and anti-interference ability of this sensor restrict its application in the measurement of cavitation collapse pressure.

[0005] (2) Strain gauge sensor: Strain gauge sensors sense load changes by measuring the deformation and resistance changes of materials under pressure. Although this method is relatively stable, it is mainly used to measure static or low-frequency loads and is mainly suitable for measuring surface pressure of solid materials. It is relatively less used for pressure measurement in liquid environments.

[0006] (3) Optical measurement technology: including laser interferometry, laser scattering and phase formation. When a violent phenomenon such as impact or explosion occurs in a liquid, the sudden change in pressure will cause changes in the optical properties of the liquid. By detecting these changes in optical properties, the impact pressure in the liquid can be indirectly measured. Although these methods have the advantages of non-contact and high precision, they usually require complex optical systems and data processing algorithms.

[0007] Therefore, providing a simple, accurate and high-frequency method and device for measuring the pressure generated by cavitation collapse has become an urgent problem to be solved. Summary of the invention

[0008] The present invention is made to solve the above-mentioned problem, and aims to provide a method for measuring cavitation collapse pressure and a Y-type optical fiber probe device thereof.

[0009] The present invention provides a method for measuring cavitation collapse pressure, which is used to obtain a set of measurement voltages based on the light intensity signal of laser reflected back from the interface between water and optical fiber when cavitation collapses in the liquid to be measured by a Y-type optical fiber probe device to calculate the cavitation collapse pressure in the liquid to be measured, and has the following characteristics: S1, decomposing the measurement voltage into an average DC component voltage V dc and the average AC component voltage Vac ; S2, according to the average DC component voltage V dc and the average AC component voltage V ac The relationship between the measured voltage and the refractive index of the liquid to be tested is obtained by means of a column formula; S3, a corresponding set of liquid densities is obtained according to a set of relationships between the measured voltage and the liquid refractive index; S4, a relationship between the cavitation collapse pressure in the liquid to be tested and the liquid density is obtained according to a set of liquid densities combined with the Tait equation or by looking up the IAPWS table, and further the relationship between the measured voltage and the cavitation collapse pressure in the liquid to be tested is obtained.

[0010] The method for measuring cavitation collapse pressure provided by the present invention may also have the following characteristics: in step S1, the average DC component voltage V dc The expression is: Average AC component voltage V ac The expression is: Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

[0011] The method for measuring cavitation collapse pressure provided by the present invention may also have the following characteristics, wherein the expression for the relationship between the measured voltage and the refractive index of the liquid in step S2 is: The expression between R0 and the measured voltage is: The expression between δR(t) and the measured voltage is: δR(t)=(R0+S)V ac (t) / V dc (t), where n1 is the refractive index of the liquid, R is the reflectivity of the liquid, R0 is the static refractive index of the liquid, G is the photodetector conversion efficiency, I0 is the laser diode intensity, S is the signal-to-noise ratio, and n1(t) is an array of liquid refractive index changes over time.

[0012] The method for measuring cavitation collapse pressure provided by the present invention may also have the following characteristics: in step S3, the expression of liquid density is: Where ρ0 is the static liquid density, is the static liquid refractive index, where The expression is: Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

[0013] The present invention provides a Y-type optical fiber probe device for measuring cavitation collapse pressure, which is used to measure the light intensity signal of laser reflected back at the interface between water and optical fiber when cavitation collapses in a liquid to be measured, obtain a group of measurement voltages, and store the group of measurement voltages. The device has the following characteristics: a laser transmitter part, which is used to provide laser signals; a probe part, one end of which is communicatively connected with the laser transmitter part and is used to receive laser signals, and the other end of which is in contact with the liquid to be measured and is used to receive laser signals reflected back by the liquid to be measured; a sensor part, which is communicatively connected with the probe part and is used to receive laser reflected back by the liquid to be measured at the probe part, and convert the light intensity signal of the laser into a voltage signal; and a data acquisition part, which is connected with the sensor part and is used to store the voltage signals.

[0014] The Y-type optical fiber probe device for measuring cavitation collapse pressure provided by the present invention may also have the following features: the probe part is a multi-mode optical fiber core with a smooth flat port, surrounded by a metal protective layer, the laser emitter is a diode laser emitter, the sensor is a photoelectric sensor, the photoelectric sensor is coupled with a fiber optic collimator, and the data acquisition card is a high-frequency data acquisition card.

[0015] The Y-type optical fiber probe device for measuring cavitation collapse pressure provided by the present invention may also have the following characteristics: the Y-type optical fiber probe device also includes a Y-type optical fiber part for emitting, receiving and transmitting laser signals; the Y-type optical fiber part is composed of three optical cores, and the three optical cores are connected by fusion connection; the Y-type optical fiber part contains three ports, namely, a laser emission end, a probe end and a laser output end.

[0016] The Y-type optical fiber probe device for measuring cavitation collapse pressure provided by the present invention may also have the following features, wherein the laser emitting end is connected to the laser emitter part for receiving the laser signal emitted by the laser emitter, the probe end is connected to the probe part through an optical fiber adapter for emitting the signal emitted by the laser emitter part and receiving the laser signal emitted by the laser emitting pole part and the laser signal reflected back from the interface between water and optical fiber of the probe part, and the laser output end is connected to the sensor part for connecting the laser signal reflected back from the interface between water and optical fiber of the probe part to the sensor part.

[0017] The Y-type optical fiber probe device for measuring cavitation collapse pressure provided by the present invention may also have the following characteristics, wherein the laser transmitter part actively emits a laser signal, the laser signal passes through the Y-type optical fiber, and is reflected by the liquid to be measured at the probe part, the laser reflected back by the liquid to be measured is received by the sensor part, and the laser light intensity signal is converted into a voltage signal, which is transmitted to the data acquisition part for storage.

[0018] Functions and Effects of the Invention

[0019] According to a method for measuring cavitation collapse pressure and a Y-type optical fiber probe device thereof involved in the present invention, in the method for measuring cavitation collapse pressure, the measuring voltage is first decomposed into an average DC component voltage and an average AC component voltage, and the relationship between the measuring voltage and the reflectivity of the liquid to be measured is constructed. Then, the relationship between the measuring voltage and the reflectivity of the liquid to be measured is constructed through the relationship between the reflectivity of the liquid to be measured and the refractive index of the liquid to be measured. The relationship between the density of the liquid to be measured and the measuring voltage is constructed by the change of the density of the liquid to be measured with the change of the refractive index. Further, the relationship between the measuring voltage and the cavitation collapse pressure in the liquid to be measured is constructed through the functional relationship between the density and pressure of the liquid to be measured. This method can achieve accurate and high-frequency measurement of the pressure generated by cavitation collapse by constructing the relationship between the measuring voltage and the cavitation collapse pressure in the liquid to be measured, thereby more accurately evaluating the impact of the cavitation collapse pressure on the wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a general structural diagram of a Y-type optical fiber probe device in an embodiment of the present invention;

[0021] Figure 2 is a structural diagram of a laser transmitter unit in an embodiment of the present invention;

[0022] Figure 3 is a structural diagram of a Y-shaped optical fiber portion in an embodiment of the present invention;

[0023] Figure 4 is a structural diagram of a probe portion in an embodiment of the present invention;

[0024] Figure 5 is a structural diagram of a sensor portion in an embodiment of the present invention;

[0025] Figure 6 is a structural diagram of a data acquisition unit in an embodiment of the present invention;

[0026] Figure 7 It is the relationship diagram between the measured voltage and the reflectivity of the liquid to be measured;

[0027] Figure 8 It is the relationship diagram between the density of the liquid to be measured and the measured pressure;

[0028] Fig. 9 It is a structural diagram of an experimental device for measuring the pressure of cavitation bubbles generated by electric spark discharge when they collapse in an embodiment of the present invention;

[0029] Fig.10 This is a measurement diagram of the pressure wave when bubbles are generated and collapsed during the spark discharge process. DETAILED DESCRIPTION

[0030] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the following embodiments and the accompanying drawings specifically illustrate a method for measuring cavitation collapse pressure and a Y-type optical fiber probe device of the present invention.

[0032] Figure 1 is a general structural diagram of a Y-type optical fiber probe device in an embodiment of the present invention;

[0033] like Figure 1 As shown, the Y-type optical fiber probe device 100 for measuring cavitation collapse pressure provided in this embodiment includes a laser transmitter part 10 , a Y-type optical fiber part 20 , a probe part 30 , a sensor part 40 and a data acquisition part 50 .

[0034] Figure 2 It is a structural diagram of the laser emitter part in an embodiment of the present invention.

[0035] like Figure 2 As shown, the laser emitter unit 10 includes a laser emission port 11 and a laser driving kit 12, which is used to emit an infrared laser signal with a wavelength of 808nm and an intensity of 1W. In this embodiment, the laser emission unit is a diode laser emitter.

[0036] Figure 3 2 is a structural diagram of a Y-type optical fiber portion in an embodiment of the present invention.

[0037] like Figure 3 The Y-shaped optical fiber portion 20 shown has three ports, a laser emission end 21, a probe end 23 and a laser output end 22.

[0038] Each port corresponds to an optical core, and the three optical cores are connected by melting.

[0039] The diameter of the optical core where the laser emitting end 21 and the laser output end 22 are located is 2 microns, and the diameter of the optical core where the probe end 23 is located is 4 microns.

[0040] like Figure 1 and Figure 3 As shown, the laser emitting end 21 is connected to the laser emitting port 11 of the laser emitting device 10, and is used to receive the laser signal emitted by the laser emitting port 11.

[0041] The probe end 23 is connected to the probe part 30 through an optical fiber adapter, which is used to send signals sent by the laser emission port 11 of the laser emitter part 10 and receive signals sent by the laser emission port 11 of the laser emitter part 10 and laser signals reflected back from the interface between water and optical fiber of the probe part 30.

[0042] The laser output end 22 is connected to the sensor part 40 and is used to connect the laser signal reflected back by the probe part 30 to the sensor part 40 .

[0043] Figure 4 2 is a structural diagram of a probe portion in an embodiment of the present invention.

[0044] like Figure 1 and Figure 4 As shown, the probe part 30 and the probe part 31 are multi-mode optical fiber cores with smooth flat ports, surrounded by a metal protective layer, which are communicatively connected to the laser emitting part 10 for receiving laser signals, and the other end is in contact with the liquid to be tested in actual use for receiving the laser signal reflected back by the liquid to be tested.

[0045] Figure 5 It is a structural diagram of the sensor part in an embodiment of the present invention.

[0046] like Figure 5 As shown, the sensor part 40 has a laser signal receiving terminal 41 and a measurement voltage output terminal 42. In this embodiment, the sensor 40 is a photoelectric sensor coupled with a fiber collimator.

[0047] like Figure 1 and Figure 5 As shown, the laser signal receiving end 41 of the sensor part 40 is in communication connection with the probe part 30 and is used to receive the laser reflected by the liquid to be tested. The sensor part converts the laser light intensity signal into a voltage signal and outputs it through the output end 42 .

[0048] Figure 6 It is a structural diagram of a data acquisition unit in an embodiment of the present invention.

[0049] like Figure 1 and Figure 6 As shown, the data acquisition unit 50 has a voltage measurement receiving port 51 connected to the voltage measurement output terminal 42 of the sensor unit 40 for collecting and storing voltage signals. In this embodiment, the data acquisition unit 50 is a high-frequency data acquisition card.

[0050] Finally, the measured voltage stored in the general-purpose computer is calculated through a program to realize conversion of the measured voltage signal into a pressure signal of cavitation collapse in the liquid to be measured.

[0051] This embodiment also provides a method for measuring cavitation collapse pressure, specifically, constructing a relationship between the measured voltage and the cavitation collapse pressure in the liquid to be measured in a general-purpose computer, and further calculating the cavitation collapse pressure in the liquid to be measured. The specific steps of the calculation method in the general-purpose computer are as follows:

[0052] S1, decomposes the measured voltage into the average DC component voltage V dc and the average AC component voltage V ac ;

[0053] S2, according to the average DC component voltage V dc and the average AC component voltage V ac The relationship between the measured voltage and the refractive index of the liquid is obtained by the column formula;

[0054] S3, obtaining a corresponding set of liquid densities according to a relationship between a set of measured voltages and a liquid refractive index;

[0055] S4, according to a set of liquid densities combined with the Tait equation or looking up the IAPWS table, the relationship between the cavitation collapse pressure in the liquid to be tested and the liquid density is obtained, and further the relationship between the measurement voltage and the cavitation collapse pressure in the liquid to be tested is obtained.

[0056] Among them, in step S1, the average DC component voltage V dc The expression is:

[0057]

[0058] Average AC component voltage V ac The expression is:

[0059]

[0060] Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

[0061] The expression for the relationship between the measured voltage and the refractive index of the liquid in step S2 is:

[0062]

[0063] The expression between R0 and the measured voltage is:

[0064] The expression between δR(t) and the measured voltage is: δR(t)=(R0+S)V ac (t) / V dc (t),

[0065] Where n1 is the refractive index of the liquid, R is the reflectivity of the liquid, R0 is the static refractive index of the liquid, G is the photodetector conversion efficiency, I0 is the laser diode intensity, S is the signal-to-noise ratio,

[0066] n1(t) is an array of liquid refractive index changes over time.

[0067] In step S3, the expression of liquid density is:

[0068]

[0069] Where ρ0 is the static liquid density, is the static liquid refractive index,

[0070] in, The expression is:

[0071]

[0072] Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

[0073] Figure 7 This is a graph showing the relationship between the measured voltage and the reflectivity of the liquid to be tested.

[0074] Figure 8 This is a graph showing the relationship between the density of the liquid to be measured and the measured pressure.

[0075] like Figure 7 As shown in the figure, the relationship between reflectivity and photodetection voltage can be obtained by monitoring the voltage change. The mathematical relationship is:

[0076] like Figure 8 As shown in the figure, the relationship between water density and pressure. The calculated ρ(t) can be used to obtain the pressure p(t) of the pressure wave generated by the bubble collapse propagating to the fiber optic probe. There are three common methods to obtain the water density-pressure relationship, such as fitting the speedy and tait equations, or looking up the table IAPWS-95.

[0077] Fig. 9 It is a structural diagram of an experimental device for measuring the pressure of cavitation bubbles generated by spark discharge when they collapse in an embodiment of the present invention.

[0078] like Fig. 9As shown, in this embodiment, a Y-type optical fiber probe device for measuring cavitation collapse pressure is built in a transparent water tank 60, a high-energy laser or a high-voltage discharger 70 generates cavitation bubbles 71, and the laser emitting unit 10 actively emits a laser signal, which reaches the probe portion 31 of the probe unit 30 through the Y-type optical fiber unit 20. After the cavitation collapses, the laser signal reaching the probe portion 31 is reflected back at the junction of water and the optical fiber in the transparent water tank 60 and is received by the laser signal receiving end 41 of the sensor unit 40. The processing end of the sensor unit 40 converts the laser light intensity signal into a voltage signal and transmits it to the data acquisition unit 50 for storage. Finally, a program is used in a general-purpose computer to calculate and convert the voltage signal into a pressure signal in water.

[0079] Fig.10 This is a measurement diagram of the pressure wave when bubbles are generated and collapsed during the spark discharge process.

[0080] like Fig.10 As shown, in the experiment of measuring the pressure of cavitation bubbles generated by spark discharge when they collapse, the Y-type optical fiber probe device measured two pressure wave signals. The first peak came from the pressure wave signal induced when the cavitation bubbles were generated, and the second peak came from the pressure wave signal generated when the cavitation bubbles collapsed.

[0081] Functions and Effects of the Embodiments

[0082] According to a method for measuring cavitation collapse pressure and a Y-type optical fiber probe device thereof involved in an embodiment of the present invention, in the method for measuring cavitation collapse pressure, the measuring voltage is first decomposed into an average DC component voltage and an average AC component voltage, and the relationship between the measuring voltage and the reflectivity of the liquid to be measured is constructed. Then, the relationship between the measuring voltage and the reflectivity of the liquid to be measured is constructed through the relationship between the reflectivity of the liquid to be measured and the refractive index of the liquid to be measured. The relationship between the density of the liquid to be measured and the measuring voltage is constructed by the change of the density of the liquid to be measured with the change of the refractive index. Further, the relationship between the measuring voltage and the cavitation collapse pressure in the liquid to be measured is constructed through the functional relationship between the density and pressure of the liquid to be measured. This method can achieve accurate and high-frequency measurement of the pressure generated by cavitation collapse by constructing the relationship between the measuring voltage and the cavitation collapse pressure in the liquid to be measured, thereby more accurately evaluating the impact of the cavitation collapse pressure on the wall.

[0083] In addition, the probe part of the Y-type probe device adopts a separate structure, which is convenient for timely replacement of the probe after it is damaged.

[0084] In addition, through the experimental verification of cavitation bubbles generated by spark discharge, it is found that the pressure wave signal measured is best when the optical fiber probe is in the normal direction of the pressure wave generated when the cavitation bubble is generated and when the cavitation bubble collapses.

[0085] In addition, the Y-type fiber optic probe device can be placed on the wall and performs better than traditional strain gauges or piezoelectric pressure sensors when detecting high-frequency and large-amplitude pressure pulsations.

[0086] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for measuring cavitation collapse pressure, for obtaining a set of measurement voltages based on a laser light intensity signal reflected from the interface between water and optical fiber when cavitation collapses in the liquid to be measured by a Y-type optical fiber probe device to calculate the cavitation collapse pressure in the liquid to be measured, characterized in that: The following steps are included: S1, decomposing the measured voltage into an average DC component voltage V dc and the average AC component voltage V ac ; S2, according to the average DC component voltage V dc and the average AC component voltage V ac The relationship between the measured voltage and the refractive index of the liquid is obtained by the column formula; S3, obtaining a corresponding set of liquid densities according to a set of relationships between the measured voltages and the liquid refractive index; S4, according to a set of liquid densities combined with the Tait equation or looking up the IAPWS table, obtain the relationship between the cavitation collapse pressure in the liquid to be tested and the liquid density, and further obtain the relationship between the measurement voltage and the cavitation collapse pressure in the liquid to be tested.

2. The method for measuring cavitation collapse pressure according to claim 1, characterized in that: in, In step S1, the average DC component voltage V dc The expression is: The average AC component voltage V ac The expression is: Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

3. The method for measuring cavitation collapse pressure according to claim 1, characterized in that: in, The expression for the relationship between the measured voltage and the refractive index of the liquid in step S2 is: The expression between R0 and the measured voltage is: The expression between δR(t) and the measured voltage is: δR(t)=(R0+S)V ac (t) / V dc (t), Where n1 is the refractive index of the liquid, R is the reflectivity of the liquid, R0 is the static refractive index of the liquid, G is the photodetector conversion efficiency, I0 is the laser diode intensity, S is the signal-to-noise ratio, and n1(t) is an array of liquid refractive index changes over time.

4. The method for measuring cavitation collapse pressure according to claim 1, characterized in that: in, In step S3, the expression of liquid density is: Where ρ0 is the static liquid density, is the static liquid refractive index, Said The expression is: Where t1 is the start time of voltage measurement, and t2 is the end time of voltage measurement.

5. A Y-type optical fiber probe device for measuring cavitation collapse pressure, used to measure the light intensity signal of laser reflected back from the interface between water and optical fiber when cavitation collapses in the measured liquid to obtain a set of measurement voltages, and store the set of measurement voltages, characterized in that: include: A laser transmitter unit, used for providing a laser signal; A probe part, one end of which is in communication connection with the laser emitting part for receiving the laser signal, and the other end of which is in contact with the liquid to be tested for receiving the laser signal reflected by the liquid to be tested; A sensor part, which is in communication connection with the probe part, and is used to receive the laser reflected by the liquid to be tested from the probe part, and convert the light intensity signal of the laser into a voltage signal; as well as The data acquisition unit is connected to the sensor unit and is used to collect and store the voltage signal.

6. The Y-type optical fiber probe device for measuring cavitation collapse pressure according to claim 5, characterized in that: in, The probe part is a multi-mode optical fiber core with a smooth flat end, surrounded by a metal protective layer. The laser transmitter is a diode laser transmitter, The sensor is a photoelectric sensor, The photoelectric sensor is coupled with a fiber collimator, The data acquisition unit is a high-frequency data acquisition unit.

7. The Y-type optical fiber probe device for measuring cavitation collapse pressure according to claim 5, characterized in that: It also includes a Y-shaped optical fiber part for sending, receiving and transmitting laser signals. The Y-shaped optical fiber portion is composed of three optical cores, and the connection method of the three optical cores is fusion connection. The Y-shaped optical fiber part has three ports, a laser emission end, a probe end and a laser output end.

8. The Y-type optical fiber probe device for measuring cavitation collapse pressure according to claim 7, characterized in that: in, The laser emitting end is connected to the laser emitter part and is used to receive the laser signal emitted by the laser emitter. The probe end is connected to the probe part through an optical fiber adapter, and is used to send out the signal sent by the laser transmitter part and receive the laser signal sent by the laser transmitter part and the laser signal reflected back from the interface between the water and the optical fiber of the probe part. The laser output end is connected to the sensor part and is used to connect the laser signal reflected from the interface between the water in the probe part and the optical fiber to the sensor part.

9. The Y-type optical fiber probe device for measuring cavitation collapse pressure according to claim 8, characterized in that: in, The laser transmitter actively emits a laser signal. The laser signal passes through the Y-type optical fiber and is reflected by the liquid to be measured at the probe part. The laser reflected by the liquid to be tested is received by the sensor part, and the light intensity signal of the laser is converted into a voltage signal. The voltage signal is transmitted to the data acquisition unit for acquisition and storage.

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