CN113933219B - Wet steam droplet volume concentration measurement experiment system and method based on ultrasonic method - Google Patents
Wet steam droplet volume concentration measurement experiment system and method based on ultrasonic method Download PDFInfo
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Abstract
The invention belongs to the technical field of measurement of volume concentration of steam droplets, and particularly relates to a wet steam droplet volume concentration measurement experiment system and method based on an ultrasonic method. According to the invention, the power of the steam generator is regulated to be matched with the regulating valve, so that the steam with different liquid drop volume concentrations is generated, and the working condition of the steam in the actual industry is simulated; two pairs of ultrasonic probes with different frequencies are arranged at the same measuring position, so that the ultrasonic energy loss coefficients with different ultrasonic frequencies are collected under the same environment, and experimental data of waveforms after ultrasonic attenuation, steam pressure and temperature are recorded in real time by an acquisition system; the synchronous, real-time and non-interference measurement of the volume concentration of the vapor liquid drop and the particle diameter of the liquid drop is realized by collecting the energy attenuation coefficients of ultrasonic waves with different frequencies under the same wet vapor working condition and combining the inverse algorithm of an ECAH long waveform model.
Description
Technical Field
The invention belongs to the technical field of measurement of volume concentration of steam droplets, and particularly relates to a wet steam droplet volume concentration measurement experiment system and method based on an ultrasonic method.
Background
The wet steam working medium is widely applied to the related fields of nuclear industry, steam turbine, chemical industry, ship engineering and the like, and the volume concentration of steam droplets is an important physical parameter affecting the steam quality and the economical efficiency and safety of related industries. The volume concentration of the steam droplets is too large, so that the thermal efficiency of a power station can be reduced, the steam turbine is subjected to cavitation, the blades of the steam turbine are damaged, and the production efficiency of the chemical industry can be influenced by the change of the volume concentration of the steam droplets. The real-time accurate measurement of the volume concentration of the vapor liquid drops is realized, and operators can take corresponding measures according to the change of the volume concentration of the liquid drops in time, so that the economical efficiency and the safety of industry are ensured. Currently, optical methods, capacitance methods, conductivity methods, thermodynamic methods and the like are commonly used in industry to measure the volume concentration of liquid drops in steam. Compared with the traditional measuring method, the ultrasonic method has the advantages of being not easy to interfere, convenient to use, free from influencing the flow field in the pipeline, capable of conducting real-time online measurement, small in equipment size, convenient to arrange in a power station, quick in response, wide in application range, small in harm to people and the like, the energy loss coefficient of ultrasonic waves is related to the ultrasonic frequency, the volume concentration of liquid drops in steam in the pipeline is related to the particle size of the liquid drops, and the ultrasonic energy loss method is suitable for online measurement of the volume concentration of wet steam liquid drops. Therefore, it is necessary to further study the feasibility of the ultrasonic attenuation method in measurement application in wet steam working conditions, and an experimental system is designed to be capable of researching the steam droplet volume concentration measurement technology based on the ultrasonic method.
Disclosure of Invention
The invention aims to provide a wet steam liquid drop volume concentration measurement experiment system based on an ultrasonic method.
The aim of the invention is realized by the following technical scheme: comprises a steam generating device, a measuring section and an electrolyte solution heater; the output end of the steam generating device is connected with the inlet of the steam outlet section; the electrolyte solution heater is connected with an inlet of the steam outlet section through a solution atomization nozzle, a solution atomization nozzle valve is arranged on the solution atomization nozzle, and a regulating valve is arranged on the steam outlet section; after saturated steam is generated by the steam generating device, isothermal liquid drops of electrolyte are mixed and added into a steam outlet section through a solution atomizing nozzle, and wet steam with adjustable humidity is generated by adjusting a valve of the solution atomizing nozzle; the lower end of the measuring section is connected with the outlet of the steam outlet section through a connecting elbow, the upper end of the measuring section is connected with the steam discharge pipeline through a connecting elbow, and drain ports are arranged below the two connecting elbows; the measuring section is characterized in that a heat tracing belt is wound on the outer side of the measuring section, an ultrasonic probe pipe groove is respectively formed in the front, the back, the left and the right of the middle of the measuring section, a thermocouple and a pressure sensor are arranged above the ultrasonic probe pipe groove on one side of the measuring section, and a sampling port is respectively formed above and below the ultrasonic probe pipe groove on the other side of the measuring section; the two groups of ultrasonic transmitting probes and the two groups of ultrasonic receiving probes are respectively arranged in four ultrasonic probe tube slots of the measuring section, and the ultrasonic transmitting probes and the ultrasonic receiving probes are arranged on the same horizontal line by using opposite injection, so that the centers of the probes are ensured to be on the same straight line; the ultrasonic wave transmitting probes are connected with the ultrasonic wave generating device, and the ultrasonic wave frequencies transmitted by the two groups of ultrasonic wave transmitting probes are different; the ultrasonic receiving probe is connected in series with the noise shielding device and acquires sound wave signals through the data acquisition system; and a vortex shedding flowmeter is arranged on the steam discharge pipeline.
The invention also provides an experimental method for measuring the volume concentration of the wet steam liquid drops based on the ultrasonic method, which comprises the following steps:
step 1: arranging a wet steam droplet volume concentration measurement experiment system based on an ultrasonic method;
step 2: saturated steam is generated by a steam generating device, isothermal liquid drops of electrolyte are mixed and added into a steam outlet section through a solution atomizing nozzle, and wet steam with adjustable humidity is generated by adjusting a valve of the solution atomizing nozzle;
step 3: wet steam enters the measuring section through the connecting elbow, and accumulated liquid generated by the wet steam due to wall collision or liquid drop gravity sedimentation is discharged from the drain port; because the measuring section is heated by the heat tracing belt, the wet steam can not generate condensation phenomenon in the flowing process of the measuring section; the two groups of ultrasonic wave transmitting probes transmit ultrasonic waves with different frequencies, the ultrasonic waves pass through wet steam in the measuring section and are acquired by the corresponding ultrasonic wave receiving probes, and then signals are synchronously transmitted to the data acquisition system in real time; the thermocouple and the pressure sensor above the ultrasonic emission probe respectively collect the temperature and the pressure of the wet steam;
step 4: the wet steam flows out of the measuring section, enters the steam discharge pipeline, and records the flow in real time through the vortex shedding flowmeter;
step 5: obtaining a measurement value of the wet steam droplet volume concentration;
step 5.1: the data acquisition system acquires the super-ultrasonic wave received by the two groups of ultrasonic wave receiving probesReceiving amplitude F after attenuation of sound wave 1 、F 2 Two groups of ultrasonic attenuation coefficients alpha are calculated 1 、α 2 ；
F 1 ＝F 10 exp(-α 1 L 1 )
F 2 ＝F 20 exp(-α 2 L 2 )
Wherein F is 10 、F 20 Respectively the initial amplitudes of the ultrasonic waves transmitted by the two groups of ultrasonic wave transmitting probes; l (L) 1 、L 2 The single-pass propagation path distances of the two groups of ultrasonic waves respectively;
step 5.2: obtaining a ratio alpha according to the ultrasonic attenuation coefficient ratio-particle size spectrum 1 /α 2 The corresponding average droplet size D;
step 5.3: according to the ultrasonic attenuation coefficient alpha 1 Or alpha 2 Calculating the volume concentration of wet steam liquid drops；
If according to the ultrasonic attenuation coefficient alpha 1 And (3) calculating:
wherein omega 1 For the angular frequency, c, of the ultrasonic waves emitted by the first set of ultrasonic emission probes 1 Sound velocity for the ultrasonic wave; k (k) cg Is the wave number of the gas phase compression wave; k is the complex wave number, k=ω 1 /c 1 +iα 1 ；
z＝(1+i)D/2δ ts
Wherein subscript g represents the gas phase and subscript s represents the liquid phase; ρ g Representing the density of the gas phase ρ s Representing the density of the liquid phase; k (k) cs Representing the wave number of the liquid phase compression wave; t is absolute temperature; kappa (kappa) g Is the gas phase heat conductivity coefficient; kappa (kappa) s Is the coefficient of thermal conductivity of liquid phase; beta g Indicating the thermal expansion coefficient of the gas phase beta s Representing the coefficient of thermal expansion of the liquid phase; c (C) Pg Represents the constant pressure specific heat capacity of the gas phase, C Ps The constant pressure specific heat capacity of the liquid phase is represented; mu is the shear modulus, and both the gas and liquid shear moduli are zero.
The invention has the beneficial effects that:
according to the invention, the power of the steam generator is regulated to be matched with the regulating valve, so that the steam with different liquid drop volume concentrations is generated, and the working condition of the steam in the actual industry is simulated; and performing measurement on the volume concentration and the particle size of the liquid drops of the steam by adopting an ultrasonic energy loss method and an ECAH-based ultrasonic particle size inversion algorithm. According to the invention, two pairs of ultrasonic probes with different frequencies are arranged at the same measuring position, so that the ultrasonic energy loss coefficients with different ultrasonic frequencies are collected under the same environment, and the experimental data of waveform, steam pressure and temperature after ultrasonic attenuation are recorded in real time by an acquisition system; the synchronous, real-time and non-interference measurement of the volume concentration of the vapor liquid drop and the particle diameter of the liquid drop is realized by collecting the energy attenuation coefficients of ultrasonic waves with different frequencies under the same wet vapor working condition and combining the inverse algorithm of an ECAH long waveform model. The invention has simple structure, real-time performance and sensitivity, accurate and convenient data acquisition, wherein the volume and concentration of the steam liquid drop can be calibrated, the working condition research range of wet steam is wide, and the invention can be applied to various industrial aspects.
Drawings
FIG. 1 is a top view of a measurement section in an experimental system of the present invention.
Fig. 2 is a front view of a measurement section in the experimental system of the present invention.
Fig. 3 is a left cross-sectional view of a measurement section in an experimental system of the invention.
FIG. 4 is a schematic view of a portion of a connecting tube connecting an elbow in an experimental system of the invention.
Fig. 5 is a schematic diagram of the elbow portion of a connecting elbow in the experimental system of the invention.
FIG. 6 is a diagram of a head and flow meter piping in the experimental system of the present invention.
Fig. 7 is an overall construction diagram of the experimental system of the present invention.
FIG. 8 is a graph of volume concentration versus ultrasonic attenuation coefficient.
FIG. 9 is a graph showing the relationship between droplet size and ultrasonic attenuation coefficient.
FIG. 10 is a flow chart of inversion of droplet size and volume concentration.
FIG. 11 is a plot of calibration volume concentration versus inversion volume concentration at 100k/200 kHz.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention relates to an on-line measurement technology research experiment system for the volume concentration of liquid drops in a wet steam medium based on ultrasonic energy loss, which is applied to the research of propagation characteristics of ultrasonic waves with different frequencies in wet steam, and mainly relates to the related technical fields of nuclear industry, steam turbine safety, measurement of the volume concentration of the liquid drops of the steam, ship engineering and the like.
The invention is an experimental system which has simple structure and low cost, and can measure the volume concentration of the flowing steam liquid drop in the pipeline and the ultrasonic propagation characteristic on line, in real time and without interference and with high sensitivity based on the ultrasonic method.
An experimental system for measuring the volume concentration of wet steam liquid drops based on an ultrasonic method comprises a steam generating device 1, a measuring section 7 and an electrolyte solution heater 15; the output end of the steam generating device 1 is connected with the inlet of the steam outlet section; the electrolyte solution heater 15 is connected with an inlet of a steam outlet section through a solution atomization nozzle, a solution atomization nozzle valve 14 is arranged on the solution atomization nozzle, and a regulating valve 2 is arranged on the steam outlet section; after saturated steam is generated by the steam generating device 1, isothermal liquid drops of electrolyte are mixed and added in a steam outlet section through a solution atomizing nozzle, and humidity-adjustable wet steam is generated by adjusting a valve 14 of the solution atomizing nozzle; the lower end of the measuring section 7 is connected with the outlet of the steam outlet section through a connecting elbow, the upper end of the measuring section 7 is connected with a steam discharge pipeline through a connecting elbow, and drain ports 3 are arranged below the two connecting elbows; the outside of the measuring section 7 is wound with a heat tracing belt 9, an ultrasonic probe tube slot is respectively formed in the front, the back, the left and the right of the middle of the measuring section 7, a thermocouple 5 and a pressure sensor 6 are arranged above the ultrasonic probe tube slot on one side of the measuring section 7, and a sampling port 8 is respectively arranged above and below the ultrasonic probe tube slot on the other side; the two groups of ultrasonic transmitting probes 4 and the two groups of ultrasonic receiving probes are respectively arranged in four ultrasonic probe tube slots of the measuring section 7, the ultrasonic transmitting probes 4 and the ultrasonic receiving probes are arranged on the same horizontal line by using opposite rays, and the centers of the probes are ensured to be on the same straight line; the ultrasonic wave transmitting probes 4 are connected with the ultrasonic wave generating device 10, and the ultrasonic wave frequencies transmitted by the two groups of ultrasonic wave transmitting probes 4 are different; the ultrasonic receiving probe is connected in series with the noise shielding device and acquires sound wave signals through the data acquisition system 11; a vortex shedding flowmeter 13 is arranged on the steam discharge pipeline.
Saturated steam is generated by a steam generator, isothermal droplets of electrolyte are added by mixing through an atomizing nozzle at a steam outlet, and humidity-adjustable wet steam is generated. And the added electrolyte liquid drops are used for calibrating the volume concentration of the steam liquid drops by combining the sampled electrolyte liquid drops with a conductivity meter, so that the steam with the calibrated volume concentration of the liquid drops is obtained.
The 4 ultrasonic probe tube slots are arranged at the same position of the measuring section, so that the volume concentration of the steam liquid drops under the same working condition can be measured more accurately by using different types of ultrasonic probes. The method adopts various high-frequency temperature-resistant ultrasonic probes, can work for a long time at 100 ℃ after heat insulation by using a heat insulation layer, adopts a correlation type installation ultrasonic probe, and adopts an ultrasonic energy attenuation method to measure the volume concentration of vapor droplets, thus realizing real-time, non-interference and online measurement. The ultrasonic probes with different frequencies are adopted to measure at the same position of the measuring section, so that the measuring result of the volume concentration of the vapor liquid drop can be more accurate.
The drainage ports are arranged at the inlet and the outlet of the measuring pipeline, so that accumulated liquid generated due to the reasons of wall collision, gravity sedimentation and the like of wet steam is discharged, the accumulated water is prevented from flowing backwards, and the ultrasonic measurement is influenced. The power-adjustable heat tracing belt and the heat insulation layer are arranged on the outer side of the measuring pipeline, so that the measuring pipeline and the wet steam in the pipeline can not generate condensation when the temperature is equal, and the accuracy of calibrating the volume concentration of the wet steam liquid drops by the conductivity method is improved. The electrolyte solution added with the wet steam is prepared in the electrolyte solution heating container in advance, and the temperature of liquid drops sprayed by the spray head is controlled to be the same as that of saturated steam by adjusting the power of the heating container, so that the saturated steam cannot be condensed.
Fig. 1 to 7 show the structural composition of an experimental body, and the experimental body comprises a steam generating device 1, a steam generating device 2, a regulating valve 3, a drain port 4, an ultrasonic probe 5, a thermocouple 6, a pressure sensor 7, a measuring section 8, a sampling port 9, a heat tracing band 10, an ultrasonic generating device 11, a data acquisition system 13, a computer 13, a vortex shedding flowmeter 14, a water spray head regulating valve 15, an electrolyte solution heater 16, a power supply, a filter and a conductivity meter. As shown in fig. 7, a power adjusting knob is provided on the steam generator 1. The regulating valve 2 is positioned at the outlet section of the steam generating device 1 and is positioned in the middle of the connecting pipeline. The upper and lower ends of the measuring section 7 are connected with a connecting pipeline and a connecting elbow. The middle position of the measuring section is provided with 4 ultrasonic probes 4 pipe slots in the front, back, left and right, and the ultrasonic probes 4 with different frequencies can be used for simultaneous measurement at the same horizontal position. The thermocouple 5 is arranged on the upper side of the installation position of the ultrasonic probe 4 of the measuring section 7, the pressure sensor 6 is arranged on the upper side of the thermocouple 5, the sampling port 8 is arranged on the upper and lower sides of the ultrasonic probe 4 on the other side, the saturated steam is mixed with isothermal water added with electrolyte to generate wet steam, the wet steam is condensed by the condenser and sampled by the sampling port 8, the conductivity is measured by using the conductivity meter, and the volume concentration of liquid drops of the wet steam is calibrated. Winding a heat tracing band 9 on the outer side of the measuring section 7, and carrying out heat preservation and heating on steam in the measuring section; the connecting elbow is positioned behind a connecting pipeline connected with the inlet of the measuring section 7 and the outlet of the measuring section 7, and a drain port 3 is arranged below the connecting elbow; the vortex shedding flowmeter 13 is positioned behind the connecting elbow and is used for recording the flow of the steam droplet volume concentration measuring device in real time; the ultrasonic probes 4 are arranged on the same horizontal line in a correlation mode, and two pairs of receiving and transmitting ultrasonic probes are respectively arranged in the front-back left-right direction in the middle of the measuring section, so that the centers of the probes are ensured to be on the same straight line; the data acquisition system 11 consists of a filter and a data acquisition device, and uses an 8-channel 100M/s high-frequency data acquisition board card for acquisition, so that the accurate calculation of the energy loss of an ultrasonic wave receiving signal is ensured; the computer 12 is externally provided with a signal amplifier which can process the pressure, temperature, flow and ultrasonic attenuation signals of the steam at the same time.
As shown in fig. 2, the upper part of the pipeline of the measuring section 7 and the connecting elbow are welded and fixed to ensure the strength and the tightness of the measuring pipeline. In the measuring section pipeline, the steam generator 1 generates saturated steam, isothermal water containing electrolyte is added through a spray head for mixing, and wet steam is generated after the isothermal water is evenly mixed and enters the measuring section pipeline. The experimental condition of the volume concentration of the steam liquid drop in the pipeline of the measuring section 7 is changed by adjusting the isothermal water solution amount of the electrolyte and the saturated steam. A thermocouple 5 and a pressure sensor 6 are arranged above the ultrasonic probe 4 to collect the pressure and temperature of steam. After the ultrasonic wave is transmitted by the transmitting end of the ultrasonic probe 4, the ultrasonic wave passes through the wet steam in the measuring section 7 and is collected by the receiving end of the ultrasonic probe 4, and then the signal is synchronously transmitted to the filter and data collection system 11 in real time.
As shown in FIG. 3, the steam generator generates saturated steam, and the electrolyte solution heating container 15 is sprayed into the saturated steam outlet of the steam generator by the solution atomizer, so that uniform and stable wet steam can be generated. The wet steam flowing through the measuring section 7 wound around the heat tracing band 9 can not generate condensation phenomenon, so that the wet steam containing electrolyte is sampled at the sampling port 8 and compared with the electrolyte concentration according to the conductivity measured by the conductivity meter, and the volume concentration of the steam liquid drops can be calibrated with high precision. Meanwhile, according to the adjustment of the solution spray nozzle adjusting valve 14, vapors with different humidity can be provided for experimental analysis.
As shown in fig. 7, saturated steam is generated from the steam generator 1, isothermal droplets 15 of electrolyte are mixed at the steam outlet through a solution atomizer, and humidity-adjustable wet steam is generated by adjusting the solution atomizer valve 14. Enters the connecting pipeline and the connecting elbow, and the accumulated liquid generated by wet steam due to wall collision or liquid drop gravity sedimentation is discharged from the drain port 3, so that the influence of the accumulated liquid backflow on the acquisition of ultrasonic signals in the measuring section 7 is prevented. The wet steam enters the measuring section 7, and as the measuring section pipeline 7 is heated by the heat tracing belt 9, the wet steam cannot generate condensation phenomenon in the flowing process of the measuring section 7, and the flowing wet steam flows out after being measured by the ultrasonic probe 4, the thermocouple 5 and the pressure sensor 6.
The ECAH model comprehensively accounts for various losses of ultrasound in a two-phase medium. Ultrasonic waves propagate in a gas-liquid two-phase medium and interact with liquid-phase particles. Because of the different acoustic characteristic impedances of liquid phase particles and gas phase, the incident compression wave will generate a set of compression waves inside and outside the particles simultaneously, and the thermal and shear waves will cause acoustic attenuation of the ultrasonic waves.
The ECAH model obtains a set of helmholtz wave equations for the complex numbers of compression waves, thermal waves and shear waves by mass, momentum, energy conservation equations, stress strain equations and thermodynamic equations:
wherein k is C 、k T 、k S And compression wave number, shear wave number and thermal wave number, respectively, ω being the ultrasonic angular frequency.
Solving the wave equation under the spherical coordinates, expanding according to the series of the spherical Bessel function and the spherical harmonic function, and bringing boundary conditions on the interface of two phases of media, thereby obtaining a 6-order linear equation set, and further solving the scattering coefficient about complex wave numbers. Since shear and thermal waves decay rapidly in a two-phase medium, the complex wave numbers are only related to the compressed wave scattering coefficient. The final complex number expression is:
wherein k is cg Is the wave number of the gas phase compression wave,is the liquid phase particle concentration, and R is the liquid phase particle radius. A is that n Is the amplitude of the compressional wave scattered by a single particle.
In gas-liquid two-phase flow media, viscosity loss, heat loss and scattering loss dominate in ultrasonic attenuation. The ultrasonic attenuation coefficient is expressed by the following formula:
α η for the attenuation coefficient of viscosity alpha ξ Alpha is the thermal conduction attenuation coefficient s For the scattering attenuation coefficient, α is the sum of the three attenuation coefficients.
The energy loss coefficient of the ultrasonic wave and the ultrasonic wave amplitude change relation can be expressed by the following formula:
F＝F 0 exp(-αL) (4)
f is the receiving amplitude after the attenuation of the ultrasonic wave, F 0 Is the initial amplitude of the ultrasonic wave, wherein alpha is the ultrasonic attenuation coefficient, and L is the single-pass propagation path distance of the ultrasonic wave.
In the gas-liquid two-phase flow medium, the ECAH model considers the viscosity attenuation, heat dissipation attenuation, acoustic scattering attenuation and absorption attenuation energy loss factors, and can calculate the ultrasonic energy loss generated after the liquid drop medium in the gas-liquid two-phase flow is permeated.
The complex wave number of the particle two-phase system is expressed as follows:
wherein D is the particle size of the liquid drops; k is the complex wave number, k=ω/c(f)+iα(f)；k c Wavenumbers in the continuous medium; f is the acoustic frequency;is the volume concentration of the particles; alpha is the attenuation coefficient; c is the speed of sound.
The attenuation coefficient can be expressed as:
for the medium-low frequency ultrasonic wave with 40 kHz-300 kHz, the model can be simplified according to the long wave form of McClements, and only the coefficient A needs to be considered n Mainly considering viscosity damping and heat dissipation damping. According to the calculation, the long-wave model lambda meeting McClements>Conditions of 20R.
At kaAt 1, consider only A n Is represented by formula (6) as the first term and the second term of
z＝(1+i)D/2δ ts (11)
Wherein subscript g represents the gas phase and subscript s represents the liquid phase; ρ g Representing the density of the gas phase ρ s Representing the density of the liquid phase; k (k) cs Representing the wave number of the liquid phase compression wave; t is absolute temperature (K); kappa (kappa) g Is the gas phase heat conductivity coefficient; kappa (kappa) s Is the coefficient of thermal conductivity of liquid phase; beta g Indicating the thermal expansion coefficient of the gas phase beta s Represents the coefficient of thermal expansion (K) of the liquid phase -1 )；C Pg The specific heat capacity of the gas phase at constant pressure (J.kg) -1 *K -1 )，C Ps The constant pressure specific heat capacity of the liquid phase is represented; mu is the shear modulus, and both the gas and liquid shear moduli are zero.
As shown in fig. 8, under the condition of low volume concentration with single particle size, the ultrasonic attenuation coefficient is approximately linearly related to the volume concentration, the ultrasonic attenuation coefficient can be regarded as a linear function of the volume concentration, under the same condition, two or more ultrasonic probes with different frequencies are used for measuring the ultrasonic attenuation coefficient under the same working condition, and the ultrasonic attenuation coefficient (alpha 1 、α 2 ) The volume concentration can be eliminated. From the formulas (4) and (8), the ultrasonic attenuation coefficient alpha is the volume concentrationA function related to the droplet size D, and thus the ratio (alpha 1 /α 2 ) As a single variable function of droplet size. And then the average droplet size D corresponding to the frequency attenuation coefficient ratio is obtained according to the attenuation coefficient ratio-particle size spectrum.
As shown in FIG. 9, the ratio of the attenuation coefficients of two ultrasonic frequencies is known to determine the particle diameter D of the liquid droplet and other physical parameters, based on the attenuation coefficient alpha of the ultrasonic 1 Or alpha 2 The volume concentration of wet steam liquid drops can be calculatedHere with an ultrasonic attenuation coefficient alpha 1 The calculation is as follows:
referring to fig. 10, for the inversion flow chart of the volume concentration of the liquid drop, ultrasonic attenuation coefficient measurement is performed on the gas-liquid two-phase flow under the same volume concentration by using ultrasonic waves with different frequencies, and the two attenuation coefficients with different frequencies are compared and brought into a model, and the average liquid drop particle size can be obtained by inverse calculation. And then the sound attenuation coefficient and the inverse calculation particle size result are put into a model, so that the volume concentration of the two-phase flow liquid drops can be inversely calculated.
Referring to fig. 11, the volume concentration of the liquid droplets of the gas-liquid two-phase flow is calculated inversely by combining the collected ultrasonic attenuation coefficients after the liquid droplet size obtained by the inversion algorithm. Through measurement experiments, the ultrasonic energy loss method can be used for measuring the volume concentration of the liquid drops of the gas-liquid two-phase flow on line within a certain error range (less than 25 percent), and the volume concentration accuracy obtained by carrying out the inverse calculation on the ratio of the acoustic attenuation coefficient by using the ultrasonic wave with larger frequency span is higher.
In summary, the experimental method for measuring the volume concentration of the wet steam liquid drops based on the ultrasonic method comprises the following steps:
step 1: arranging a wet steam droplet volume concentration measurement experiment system based on an ultrasonic method;
step 2: saturated steam is generated by the steam generating device 1, isothermal liquid drops of electrolyte are mixed and added in a steam outlet section through a solution atomization nozzle, and humidity-adjustable wet steam is generated by adjusting a valve 14 of the solution atomization nozzle;
step 3: wet steam enters the measuring section 7 through the connecting elbow, and accumulated liquid generated by the wet steam due to wall collision or liquid drop gravity sedimentation is discharged from the water drain port 3; because the measuring section 7 is heated by the heat tracing belt 9, the wet steam cannot generate condensation phenomenon in the flowing process of the measuring section 7; the two groups of ultrasonic wave transmitting probes 4 transmit ultrasonic waves with different frequencies, the ultrasonic waves pass through wet steam in the measuring section 7 and are acquired by the corresponding ultrasonic wave receiving probes, and then signals are synchronously transmitted to the data acquisition system 11 in real time; the thermocouple 5 and the pressure sensor 6 above the ultrasonic emission probe 4 respectively collect the temperature and the pressure of the wet steam;
step 4: the wet steam flows out of the measuring section 7 and enters a steam discharge pipeline, and the flow is recorded in real time through a vortex shedding flowmeter 13;
step 5: obtaining a measurement value of the wet steam droplet volume concentration;
step 5.1: the data acquisition system 11 acquires the receiving amplitude F after the attenuation of the ultrasonic waves received by the two groups of ultrasonic receiving probes 1 、F 2 Two groups of ultrasonic attenuation coefficients alpha are calculated 1 、α 2 ；
F 1 ＝F 10 exp(-α 1 L 1 )
F 2 ＝F 20 exp(-α 2 L 2 )
Wherein F is 10 、F 20 Respectively the initial amplitudes of the ultrasonic waves emitted by the two groups of ultrasonic emission probes 4; l (L) 1 、L 2 The single-pass propagation path distances of the two groups of ultrasonic waves respectively;
step 5.2: obtaining a ratio alpha according to the ultrasonic attenuation coefficient ratio-particle size spectrum 1 /α 2 The corresponding average droplet size D;
step 5.3: according to the ultrasonic attenuation coefficient alpha 1 Or alpha 2 Calculating the volume concentration of wet steam liquid drops
If according to the ultrasonic attenuation coefficient alpha 1 And (3) calculating:
wherein omega 1 For the angular frequency, c, of the ultrasonic waves emitted by the first set of ultrasonic emission probes 4 1 Sound velocity for the ultrasonic wave; k (k) cg Is the wave number of the gas phase compression wave; k is the complex wave number, k=ω 1 /c 1 +iα 1 ；
z＝(1+i)D/2δ ts
Wherein subscript g represents the gas phase and subscript s represents the liquid phase; ρ g Representing the density of the gas phase ρ s Representing the density of the liquid phase; k (k) cs Representing the wave number of the liquid phase compression wave; t is absolute temperature; kappa (kappa) g Is the gas phase heat conductivity coefficient; kappa (kappa) s Is the coefficient of thermal conductivity of liquid phase; beta g Indicating the thermal expansion coefficient of the gas phase beta s Representing the coefficient of thermal expansion of the liquid phase; c (C) Pg Represents the constant pressure specific heat capacity of the gas phase, C Ps The constant pressure specific heat capacity of the liquid phase is represented; mu is the shear modulus, and both the gas and liquid shear moduli are zero.
According to the invention, the power of the steam generator is regulated to be matched with the regulating valve, so that the steam with different liquid drop volume concentrations is generated, and the working condition of the steam in the actual industry is simulated; and performing measurement on the volume concentration and the particle size of the liquid drops of the steam by adopting an ultrasonic energy loss method and an ECAH-based ultrasonic particle size inversion algorithm. For the convenience of experiments, two pairs of ultrasonic probes with different frequencies are arranged at the same measuring position. The ultrasonic energy loss coefficients of different ultrasonic frequencies are collected under the same environment, and experimental data of waveforms after ultrasonic attenuation, steam pressure and steam temperature are recorded in real time by the collecting system. The synchronous, real-time and non-interference measurement of the volume concentration of the vapor liquid drop and the particle diameter of the liquid drop is realized by collecting the energy attenuation coefficients of ultrasonic waves with different frequencies under the same wet vapor working condition and combining the inverse algorithm of an ECAH long waveform model. The invention has simple structure, real-time performance and sensitivity, accurate and convenient data acquisition, wherein the volume and concentration of the steam liquid drop can be calibrated, the working condition research range of wet steam is wide, and the invention can be applied to various industrial aspects.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. An experimental system for measuring the volume concentration of wet steam liquid drops based on an ultrasonic method is characterized in that: comprises a steam generating device (1), a measuring section (7) and an electrolyte solution heater (15); the output end of the steam generating device (1) is connected with the inlet of the steam outlet section; the electrolyte solution heater (15) is connected with an inlet of the steam outlet section through a solution atomization nozzle, a solution atomization nozzle valve (14) is arranged on the solution atomization nozzle, and the steam outlet section is provided with a regulating valve (2); after saturated steam is generated by the steam generating device (1), isothermal liquid drops of electrolyte are mixed and added in a steam outlet section through a solution atomizing nozzle, and humidity-adjustable wet steam is generated by adjusting a valve (14) of the solution atomizing nozzle; the lower end of the measuring section (7) is connected with the outlet of the steam outlet section through a connecting elbow, the upper end of the measuring section (7) is connected with a steam discharge pipeline through a connecting elbow, and drain ports (3) are arranged below the two connecting elbows; the measuring section (7) is wound with a heat tracing belt (9), an ultrasonic probe tube slot is respectively formed in the front, the back, the left and the right of the middle of the measuring section (7), a thermocouple (5) and a pressure sensor (6) are arranged above the ultrasonic probe tube slot on one side of the measuring section (7), and a sampling port (8) is respectively formed above and below the ultrasonic probe tube slot on the other side; two groups of ultrasonic transmitting probes (4) and two groups of ultrasonic receiving probes are respectively arranged in four ultrasonic probe tube slots of a measuring section (7), the ultrasonic transmitting probes (4) and the ultrasonic receiving probes are arranged on the same horizontal line by using opposite rays, and the centers of the probes are ensured to be on the same straight line; the ultrasonic wave transmitting probes (4) are connected with the ultrasonic wave generating device (10), and the ultrasonic wave frequencies transmitted by the two groups of ultrasonic wave transmitting probes (4) are different; the ultrasonic receiving probe is connected in series with the noise shielding device and acquires sound wave signals through the data acquisition system (11); the steam discharge pipeline is provided with a vortex shedding flowmeter (13).
2. The experimental method for measuring the volume concentration of wet steam liquid drops based on the ultrasonic method according to claim 1 is characterized by comprising the following steps:
step 1: arranging a wet steam droplet volume concentration measurement experiment system based on an ultrasonic method;
step 2: saturated steam is generated by a steam generating device (1), isothermal liquid drops of electrolyte are added into a steam outlet section through a solution atomizing nozzle in a mixing way, and humidity-adjustable wet steam is generated by adjusting a valve (14) of the solution atomizing nozzle;
step 3: wet steam enters the measuring section (7) through the connecting elbow, and accumulated liquid generated by the wet steam due to wall collision or liquid drop gravity sedimentation is discharged from the water drain port (3); because the measuring section (7) is heated by the heat tracing belt (9), the wet steam can not generate condensation phenomenon in the flowing process of the measuring section (7); the two groups of ultrasonic wave transmitting probes (4) transmit ultrasonic waves with different frequencies, the ultrasonic waves pass through wet steam in the measuring section (7) and are collected by the corresponding ultrasonic wave receiving probes, and then signals are synchronously transmitted to the data collecting system (11) in real time; a thermocouple (5) and a pressure sensor (6) above the ultrasonic emission probe (4) respectively collect the temperature and the pressure of the wet steam;
step 4: the wet steam flows out of the measuring section (7) and enters a steam discharge pipeline, and the flow is recorded in real time through a vortex shedding flowmeter (13);
step 5: obtaining a measurement value of the wet steam droplet volume concentration;
step 5.1: the data acquisition system (11) is used for acquiring the receiving amplitude F after the attenuation of the ultrasonic waves received by the two groups of ultrasonic receiving probes 1 、F 2 Two groups of ultrasonic attenuation coefficients alpha are calculated 1 、α 2 ；
F 1 ＝F 10 exp(-α 1 L 1 )
F 2 ＝F 20 exp(-α 2 L 2 )
Wherein F is 10 、F 20 Respectively the initial amplitudes of the ultrasonic waves emitted by the two groups of ultrasonic emission probes (4); l (L) 1 、L 2 The single-pass propagation path distances of the two groups of ultrasonic waves respectively;
step 5.2: obtaining a ratio alpha according to the ultrasonic attenuation coefficient ratio-particle size spectrum 1 /α 2 The corresponding average droplet size D;
step 5.3: according to the ultrasonic attenuation coefficient alpha 1 Or alpha 2 Calculating the volume concentration of wet steam liquid drops
If according to the ultrasonic attenuation coefficient alpha 1 And (3) calculating:
wherein omega 1 For the angular frequency, c, of the ultrasonic waves emitted by the first set of ultrasonic emission probes (4) 1 Sound velocity for the ultrasonic wave; k (k) cg Is the wave number of the gas phase compression wave; k is the complex wave number, k=ω 1 /c 1 +iα 1 ；
z＝(1+i)D/2δ ts
Wherein subscript g represents the gas phase and subscript s represents the liquid phase; ρ g Representing the density of the gas phase ρ s Representing the density of the liquid phase; k (k) cs Representing the wave number of the liquid phase compression wave; t is absolute temperature; kappa (kappa) g Is the gas phase heat conductivity coefficient; kappa (kappa) s Is the coefficient of thermal conductivity of liquid phase; beta g Indicating the thermal expansion coefficient of the gas phase beta s Representing the coefficient of thermal expansion of the liquid phase;represents the specific heat capacity of the gas phase at constant pressure +.>The constant pressure specific heat capacity of the liquid phase is represented; mu is the shear modulus, and both the gas and liquid shear moduli are zero.
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| FR2657693A1 (en) * | 1990-01-26 | 1991-08-02 | Commissariat Energie Atomique | Method for ultrasonic detection of the appearance of a gas phase in a liquid phase contained in a chamber |
| CN104297112A (en) * | 2014-11-05 | 2015-01-21 | 上海理工大学 | Measuring method and measuring device for liquid drop particles in wet-steam region |
| CN104849183A (en) * | 2015-04-29 | 2015-08-19 | 上海理工大学 | Ultrasonic attenuation spectrum based mixed solid particle size and concentration measurement method |
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