CN114113815A - Device and method for measuring charge characteristics of particulate matters in ion flow field - Google Patents

Device and method for measuring charge characteristics of particulate matters in ion flow field Download PDF

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CN114113815A
CN114113815A CN202111402080.XA CN202111402080A CN114113815A CN 114113815 A CN114113815 A CN 114113815A CN 202111402080 A CN202111402080 A CN 202111402080A CN 114113815 A CN114113815 A CN 114113815A
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charge
polar plate
density
diffusion
field
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CN114113815B (en
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卢铁兵
郝福钦
申南轩
郭小江
申旭辉
赵瑞斌
孙栩
李春华
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Huaneng Clean Energy Research Institute
North China Electric Power University
Huaneng Group Technology Innovation Center Co Ltd
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Huaneng Clean Energy Research Institute
North China Electric Power University
Huaneng Group Technology Innovation Center Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
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Abstract

The invention relates to a device and a method for measuring the charge characteristics of particulate matters in an ionic flow field, belonging to the technical field of the ionic flow field, wherein field charge parameters are determined by using a least square method according to the electric field intensity of a lower polar plate when the ion current density is zero, and the space charge density of the particulate matters in field charge is determined according to the field charge parameters; according to the field charge parameters, the ion current densities and the synthetic electric field intensity of the lower polar plate corresponding to each ion current density, the diffusion charge parameters are determined by using a two-dimensional particle swarm algorithm, and further, the particulate diffusion charge space charge density is determined according to the diffusion charge parameters, so that the simultaneous measurement of the field charge characteristic component and the diffusion charge characteristic component is realized.

Description

Device and method for measuring charge characteristics of particulate matters in ion flow field
Technical Field
The invention relates to the technical field of ion flow fields, in particular to a device and a method for measuring the charge characteristics of particles in an ion flow field.
Background
Aiming at the problem of uneven energy distribution, a power transmission network comprising an extra-high voltage direct current transmission line is gradually built. The field intensity of the surface of the conducting wire of the extra-high voltage direct current transmission line exceeds the limit value of ionization of air, and corona discharge can be caused around the conducting wire. Compared with extra-high voltage alternating current transmission, space charges generated by extra-high voltage direct current transmission can be dispersed in the space around the conducting wire and the ground, and an ion flow field is formed. The space charge generated by corona can be combined with the space particles under the action of self thermal motion and space electric field to form charged particles, namely diffusion charge and field charge. Charged particles can cause distortion of the surrounding electric field, making the ion flow field problem more complex. The particulate matter components in the natural space are complex, and besides the mass concentration, the real-time measurement of parameters such as particle size, dielectric constant and mass density is difficult to realize, so that the field-induced and diffusion charge characteristics of the particulate matter cannot be directly predicted and analyzed through a particulate matter charge model. Meanwhile, the existing method for measuring the charged characteristics of the particles can obtain the total charged quantity of the particles, and cannot obtain field induced and diffused charged components. Therefore, in order to realize modeling and prediction of an ion flow field in an environment with particle charging, research on a method capable of simultaneously measuring particle field and diffusion charging characteristics is urgently needed.
Disclosure of Invention
The invention aims to provide a device and a method for measuring the charge characteristic of particulate matters in an ion flow field, which are used for simultaneously measuring field-induced and diffusion charge characteristic components.
In order to achieve the purpose, the invention provides the following scheme:
a device for measuring the charge characteristics of particulate matter in an ionic flow field, the device comprising: the device comprises a corona wire mesh, an upper polar plate, a lower polar plate, a field mill and an ion current plate;
the corona wire mesh, the upper polar plate and the lower polar plate are sequentially and correspondingly arranged from top to bottom; the field mill and the ion flow plate are both arranged on one side of the lower polar plate opposite to the upper polar plate;
the corona wire mesh is used for generating corona discharge after voltage is applied to generate ion flow, and ions in the ion flow are adsorbed on the particles between the upper polar plate and the lower polar plate to form charged particles;
the ion flow plate is used for measuring the density of the ion flow;
the lower polar plate is grounded, the upper polar plate is used for generating a nominal electric field between the upper polar plate and the lower polar plate after voltage is applied, and the nominal electric field, charged particles and ions jointly act to form a synthetic electric field;
the field mill is used for measuring the resultant electric field intensity at the lower polar plate.
Optionally, the apparatus further comprises: a first high voltage direct current power supply and a second high voltage direct current power supply;
the first high-voltage direct-current power supply is connected with the corona wire mesh and used for applying first voltages with different magnitudes to the corona wire mesh;
and the second high-voltage direct current power supply is connected with the upper polar plate and is used for applying a second voltage to the upper polar plate.
Optionally, the apparatus further comprises: a plurality of fixed brackets;
the plurality of fixing supports are used for fixing the corona wire mesh, the upper polar plate and the lower polar plate.
A method for measuring the charging characteristics of particles based on the device for measuring the charging parameters of the particles in an ionic flow field comprises the following steps:
acquiring the synthetic electric field intensity of the lower polar plate when the ion current density is zero;
determining field charge parameters by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero;
determining the field charge space charge density of the particulate matters according to the field charge parameters;
acquiring a plurality of ion current densities when the upper polar plate applies voltage and the corona wire mesh applies voltages of different magnitudes and the resultant electric field intensity at the lower polar plate corresponding to each ion current density;
determining diffusion charge parameters by using a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity of the lower polar plate corresponding to each ion current density; the diffusion charge parameters comprise a first diffusion charge parameter and a second diffusion charge parameter;
determining the diffusion charge space charge density of the particulate matter according to the diffusion charge parameters;
and determining the sum of the particulate matter field charge space charge density and the particulate matter diffusion charge space charge density as the particulate matter space charge density.
Optionally, the obtaining the composite electric field intensity at the lower plate when the ion current density is zero further includes:
determining a field charge parameter as
Figure BDA0003365144780000031
In the formula, thetaEIs a field charge parameter,. epsilon0Is the dielectric constant of air, epsilonpIs the relative dielectric constant of the particulate matter, d is the particle size of the particulate matter, and ρ is the mass density of the particulate matter;
according to the space charge density expression of the particulate matter generated by diffusion charge, determining the diffusion charge parameter as
Figure BDA0003365144780000032
In the formula, thetad1、θd2Respectively a first diffusion charge parameter and a second diffusion charge parameter, KBIs Boltzmann constant, T is the absolute temperature of the environment, e is the electronic charge, T is the charge time, mjIs the jth ion mass;
constructing an expression of the space charge density of the particulate matter as rho according to the field charge parameter and the diffusion charge parameterw＝θEmcE+θd1mcln(1+θd2ρe) (ii) a In the formula, ρwIs the space charge density of the particles, E is the electric field strength at the lower plate, mcIs the mass concentration of the particulate matter, peIs the ion space charge density.
Optionally, determining field charge parameters by using a least square method according to the synthesized electric field intensity at the lower plate when the ion current density is zero, specifically including:
the expression of the synthesized electric field intensity at the lower polar plate when the ion current density is determined to be zero is
Figure BDA0003365144780000033
In the formula, EgThe resultant electric field intensity, U, at the lower plate when the ion current density is zero2The voltage applied to the upper polar plate is h, and the distance between the upper polar plate and the lower polar plate is h;
and solving the expression of the synthetic electric field intensity at the lower polar plate when the ion current density is zero by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero to obtain field charge parameters.
Optionally, determining the field charge space charge density of the particulate matter according to the field charge parameter specifically includes:
according to the field charge parameters, using a formula rhoE＝θEmcEgDetermining the field charge space charge density of the particulate matters;
in the formula, ρEIs the particulate field charge space charge density.
Optionally, the determining the diffusion charge parameters by using a two-dimensional particle swarm algorithm according to the field-induced charge parameters, the multiple ion current densities and the synthetic electric field intensity at the lower plate corresponding to each ion current density specifically includes:
according to the control equation of ion flow field
Figure BDA0003365144780000041
And the expression of the space charge density of the particles, and the function of constructing the synthesized electric field at the lower polar plate as a diffusion charge parameter is Ek＝f(θd1,θd2) (ii) a In the formula (I), the compound is shown in the specification,
Figure BDA0003365144780000042
for potential, J is ion current density, k is ion mobility, EkA composite electric field;
establishing an error function of
Figure BDA0003365144780000043
Wherein S () is an error function, EkiAnd E'kiRespectively a measured value and a calculated value of the ith time of the synthesized electric field intensity at the lower polar plate, wherein n is the total number of times of measurement;
and determining the diffusion charge parameters by using a two-dimensional particle swarm algorithm based on the function and the error function of the diffusion charge parameters of the synthesized electric field at the lower plate according to the field charge parameters, the ion current densities and the synthesized electric field intensity at the lower plate corresponding to each ion current density.
Optionally, determining the particulate diffusion charge space charge density according to the diffusion charge parameter specifically includes:
according to the diffusion charge parameters, using a formula rhod＝θd1mcln(1+θd2ρe) Determining the diffusion charge space charge density of the particulate matters;
in the formula, ρdThe charge space charge density is the particle diffusion charge.
A particulate matter charge characteristic measurement system, the system comprising:
the first synthetic electric field intensity acquisition module is used for acquiring the synthetic electric field intensity of the lower polar plate when the ion current density is zero;
the field charge parameter determination module is used for determining field charge parameters by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero;
the particle field charge space charge density determining module is used for determining the particle field charge space charge density according to the field charge parameters;
the second synthetic electric field intensity acquisition module is used for acquiring a plurality of ion current densities when the upper polar plate applies voltage and the corona wire mesh applies voltages of different magnitudes and synthetic electric field intensity at the lower polar plate corresponding to each ion current density;
the diffusion charge parameter determining module is used for determining diffusion charge parameters by utilizing a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity at the lower polar plate corresponding to each ion current density; the diffusion charge parameters comprise a first diffusion charge parameter and a second diffusion charge parameter;
the particle diffusion charge space charge density determining module is used for determining the particle diffusion charge space charge density according to the diffusion charge parameters;
and the particle space charge density determining module is used for determining the sum of the particle field charge space charge density and the particle diffusion charge space charge density as the particle space charge density.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a device and a method for measuring the charge characteristics of particulate matters in an ionic flow field, wherein field charge parameters are determined by using a least square method according to the electric field intensity synthesized by a lower polar plate when the ion current density is zero, and the space charge density of the particulate matters in the field charge is determined according to the field charge parameters; according to the field charge parameters, the ion current densities and the synthetic electric field intensity of the lower polar plate corresponding to each ion current density, the diffusion charge parameters are determined by using a two-dimensional particle swarm algorithm, and further, the particulate diffusion charge space charge density is determined according to the diffusion charge parameters, so that the simultaneous measurement of the field charge characteristic component and the diffusion charge characteristic component is realized.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a structural diagram of a device for measuring the charge characteristics of particulate matters in an ion flow field, provided by the invention;
fig. 2 is a flowchart of a method for measuring the charge characteristics of particles in an ion flow field according to the present invention;
FIG. 3 is a schematic diagram of a method for measuring the charge characteristics of particles in an ion flow field according to the present invention;
FIG. 4 is a graph of the results of measurements of the ion flow field of the lower plate under different humidity conditions according to an embodiment of the present invention;
fig. 4(a) is a lower plate ion flow field measurement result diagram of a positive polarity experiment under different humidity conditions, and fig. 4(b) is a lower plate ion flow field measurement result diagram of a negative polarity experiment under different humidity conditions;
FIG. 5 is a graph of field charge parameter measurements at different humidities, according to an embodiment of the present invention;
FIG. 6 is a graph of diffusion charge parameter measurements at different humidities, according to an embodiment of the present invention; fig. 6(a) is a graph of first diffusion charge parameter measurements at different humidities, and fig. 6(b) is a graph of second diffusion charge parameter measurements at different humidities.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a device and a method for measuring the charge characteristic of particulate matters in an ion flow field, which are used for simultaneously measuring field-induced and diffusion charge characteristic components.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention provides a device for measuring the charge characteristics of particulate matters in an ion flow field, which comprises the following components in percentage by weight as shown in figure 1: corona wire mesh, upper polar plate, lower polar plate, field mill and ion current board.
The corona wire mesh, the upper polar plate and the lower polar plate are sequentially and correspondingly arranged from top to bottom; the field mill and the ion flow plate are both arranged on one side of the lower polar plate opposite to the upper polar plate.
The corona wire mesh is used for generating corona discharge after voltage is applied to generate ion flow, and ions in the ion flow are adsorbed on the particles between the upper polar plate and the lower polar plate to form charged particles.
Ion flow plates are used to measure the density of an ion stream.
The lower polar plate is grounded, the upper polar plate is used for generating a nominal electric field between the upper polar plate and the lower polar plate after voltage is applied, and the nominal electric field, the charged particles and ions jointly act to form a synthetic electric field.
The field mill is used for measuring the resultant electric field intensity at the lower plate.
The device still includes: a first high voltage dc power supply and a second high voltage dc power supply. The first high-voltage direct-current power supply is connected with the corona wire mesh and used for applying first voltages U with different sizes to the corona wire mesh1(ii) a The second high-voltage DC power supply is connected with the upper polar plate and is used for applying a second voltage U to the upper polar plate2。
The device still includes: a plurality of fixed brackets; the plurality of fixing supports are used for fixing the corona wire mesh, the upper polar plate and the lower polar plate.
Referring to fig. 1, the particulate matter charge parameter measuring device is a three-layer parallel polar plate structure. The uppermost layer is called corona wire mesh and is pressed U1Corona discharge is generated to generate ion current required in experiment, and injection ion can be controlled by adjusting voltage of corona wire meshWhen particles exist in the space, the particles between the upper and lower polar plates can adsorb ions generated by corona discharge of the corona wire mesh to form charged particles; the middle layer is called as an upper polar plate and is pressurized U2The lower polar plate and the lowest layer of the lower polar plate jointly generate a nominal electric field, the nominal electric field, charged particles and ions jointly act to form a synthetic electric field, and the lower polar plate is grounded; a field mill for measuring an electric field is arranged in the middle of the lower polar plate, and an ion flow plate for measuring the size of ion flow is arranged beside the field mill.
The device for measuring the charge parameters realizes the measurement of the field charge parameters and the diffusion charge parameters of the particles.
The ion flow field control equation of the measuring platform designed by the invention is as follows:
Figure BDA0003365144780000071
the field-diffusion charge parameters of the particulate matter defined by the invention are as follows:
in order to realize the measurement of the charge characteristics of the particulate matters in the ion flow field, a characterization method of the charge characteristics of the particulate matters needs to be explained. When particles exist in the space, ions generated by corona discharge collide with the particles under the action of an electric field, so that the particles are charged, and the charging mode is called field charging. When the electric field generated by the charged particles can counteract the external electric field, the particles are considered to reach a saturated field charge state, and the space charge density expression generated by field charge is as follows:
Figure BDA0003365144780000072
in the formula ofpIs the relative dielectric constant of the particles, d is the particle size of the particles; m iscIs the mass concentration of the particulate matter; ρ is the mass density of the particulate matter.
The ions generated by corona discharge not only collide with the particulate matter under the action of an electric field, but also collide with the particulate matter under the action of self-thermal motion, and the charging mode is called diffusion charging. Because the thermal energy of the ions has no upper limit, the diffusion charge theoretically has no saturated diffusion charge quantity, and the space charge density of the particulate matters generated by the diffusion charge quantity is as follows:
Figure BDA0003365144780000081
wherein T is the absolute temperature of the environment; t is the charging time; kBBoltzmann constant; and e is the electronic electricity quantity.
The particles in the space under the natural environment are a mixture of various types. Besides the mass concentration, the real-time measurement of parameters such as particle size, dielectric constant and mass density is difficult to realize, so that the prediction and analysis of the field-induced and diffusion charge characteristics of the particulate matter cannot be realized by directly using the formulas (2) to (3). In order to solve the problems, the field-induced and diffusion charge characteristics of the particles are simultaneously represented, the influence of the parameters on the field-induced and diffusion charge characteristics of the particles is comprehensively considered, and a field-induced charge parameter theta is definedEAnd diffusion charge parameter θd1、θd2：
Determining a field charge parameter as
Figure BDA0003365144780000082
In the formula, thetaEIs a field charge parameter,. epsilon0Is the dielectric constant of air, epsilonpIs the relative dielectric constant of the particulate matter, d is the particle size of the particulate matter, and ρ is the mass density of the particulate matter;
according to the space charge density expression of the particulate matter generated by diffusion charge, determining the diffusion charge parameter as
Figure BDA0003365144780000083
In the formula, thetad1、θd2Respectively a first diffusion charge parameter and a second diffusion charge parameterScattering electrical charge parameter, KBIs Boltzmann constant, T is the absolute temperature of the environment, e is the electronic charge, T is the charge time, mjIs the jth ion mass;
according to the field charge parameters and the diffusion charge parameters, an expression of the space charge density of the particles is constructed as
ρw＝θEmcE+θd1mcln(1+θd2ρe) (6)
In the formula, ρwIs the space charge density of the particles, E is the electric field strength at the lower plate, mcIs the mass concentration of the particulate matter, peIs the ion space charge density.
After the charge parameters are defined, physical parameters such as particle size, dielectric constant, mass density and the like do not need to be measured independently. The charge characteristics of the particles and the space charge density generated by the particles under the current environment can be obtained by directly measuring the charge parameters.
From the formula (4), the field charge parameter θEThe capacity of trapping space charge by a field charge mode of particulate matters with unit mass concentration under unit electric field intensity is characterized. The larger the field charge parameter, the stronger the ability of the particles to be field charged in the electric field.
From the formula (5), the diffusion charge parameter θd1The capacity of capturing space charge density by means of diffusion charge of particulate matter with unit mass concentration is characterized. Diffusion charge parameter theta under the same ion space charge densityd1The larger the particle capture capacity to space charge density. Diffusion charge parameter thetad2Reflecting the coupling relation between the particle diffusion charge quantity and the ion space charge density. Diffusion charge parameter thetad2The larger the mass concentration of the particulate matter, the stronger the capacity of trapping space charge by diffusion charge under the unit ion space charge density.
Based on the device for measuring the particle charge parameters in the ionic flow field, the invention also provides a method for measuring the particle charge characteristics according to defined expressions of field charge parameters, diffusion charge parameters and particle space charge density, as shown in fig. 2-3, the method comprises the following steps:
step 101, obtaining the composite electric field intensity at the lower polar plate when the ion current density is zero.
And 102, determining field charge parameters by using a least square method according to the synthesized electric field intensity of the lower polar plate when the ion current density is zero.
The method specifically comprises the following steps:
as can be seen from the formula (6), when there is no ion space charge in the space, that is, when the ion current density J is 0, the particulate charging method is field charging. From the control equation (1) of the measurement platform, we can derive:
Figure BDA0003365144780000091
the expression of the synthesized electric field intensity at the lower polar plate when the ion current density is determined to be zero is
Figure BDA0003365144780000101
It can be seen that when the ion current density J is 0, the electric field intensity E at the lower plate is highgWith field charge parameter θ onlyE(ii) related;
in the formula, EgThe resultant electric field intensity, U, at the lower plate when the ion current density is zero2The voltage applied to the upper polar plate is h, and the distance between the upper polar plate and the lower polar plate is h;
and solving the expression of the synthetic electric field intensity at the lower polar plate when the ion current density is zero by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero to obtain field charge parameters.
And 103, determining the space charge density of the field charge of the particulate matters according to the field charge parameters.
The method specifically comprises the following steps:
according to field charge parameters, using the formula rhoE＝θEmcEgDetermining the field charge space charge density of the particulate matters;
in the formula, ρEField-induced charge space charge for particulate matterDensity.
And 104, acquiring a plurality of ion current densities when the upper plate is applied with voltage and the corona wire mesh is applied with voltage of different magnitudes and the resultant electric field intensity at the lower plate corresponding to each ion current density.
105, determining diffusion charge parameters by using a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity of the lower polar plate corresponding to each ion current density; the diffusion charge parameters include a first diffusion charge parameter and a second diffusion charge parameter.
The method specifically comprises the following steps:
according to the control equation of ion flow field
Figure BDA0003365144780000102
And the expression of the space charge density of the particles, and the function of constructing the synthesized electric field at the lower polar plate as the diffusion charge parameter is Ek＝f(θd1,θd2) (ii) a In the formula (I), the compound is shown in the specification,
Figure BDA0003365144780000103
for potential, J is ion current density, k is ion mobility, EkIn order to synthesize the electric field,
Figure BDA0003365144780000104
is a vector differential operator;
establishing an error function of
Figure BDA0003365144780000111
Wherein S () is an error function, EkiAnd E'kiRespectively a measured value and a calculated value of the ith time of the synthesized electric field intensity at the lower polar plate, wherein n is the total number of times of measurement;
and determining the diffusion charge parameters by using a two-dimensional particle swarm algorithm based on the function and the error function of the diffusion charge parameters of the synthesized electric field at the lower plate according to the field charge parameters, the ion current densities and the synthesized electric field intensity at the lower plate corresponding to each ion current density.
Wherein the position vector defining the particle is:
x＝(x1,x2)
in the formula
Figure BDA0003365144780000112
The subscripts max and min represent the maximum and minimum values of the diffusion charge parameter values, respectively.
Given diffusion charge parameter θd1And thetad2The value ranges are respectively as follows: 6.85X 10-4-0.267C/kg、2.51×108-1.26×1010m3and/C. Charge parameter theta due to particulate matter diffusiond1And thetad2Are of a large order of magnitude. In order to facilitate the particle swarm algorithm to search the optimal value of the diffusion charge parameter, the per-unit value of the diffusion charge parameter is used in the data processing process, and the minimum value of the diffusion charge parameter value is selected as the reference value.
The fitness calculation formula and the required limit value of the particle swarm algorithm are respectively as follows:
f(x1,x2)＝S(θd1,θd2)
Figure BDA0003365144780000113
in the solving process, the population size N is 10, and the acceleration factor c1＝c21.5, and 0.8.
And 106, determining the diffusion charge space charge density of the particles according to the diffusion charge parameters.
The method specifically comprises the following steps:
according to the diffusion charge parameters, using the formula rhod＝θd1mcln(1+θd2ρe) Determining the diffusion charge space charge density of the particulate matters;
in the formula, ρdThe charge space charge density is the particle diffusion charge.
And step 107, determining the sum of the particulate matter field charge space charge density and the particulate matter diffusion charge space charge density as the particulate matter space charge density.
Based on the principle of field-diffusion charge parameter separation and measurement of particulate matters in the ion flow field, field-induced and diffusion charge parameters can be obtained by measuring electric field intensities corresponding to different ion current densities (including ion current density J equal to 0), so that separation and measurement of particle field-induced and diffusion charge characteristics are realized.
Aiming at the phenomenon that space charge generated during the operation of an extra-high voltage direct current transmission line is combined with particles in the air to generate particle charge, the influence of various parameters on the field-induced and diffusion charge characteristics of the particles is comprehensively considered, and a field-induced charge parameter theta is defined by the methodEAnd diffusion charge parameter θd1And thetad2. And a field-diffusion charge characteristic measuring method based on ion flow field data is provided by using a particle charge characteristic measuring device with a parallel flat plate electrode structure. By measuring the ion flow field under different humidity conditions, the charge parameters capable of representing the charge characteristics of the particles are obtained.
The following description will explain the method for measuring the charge characteristics of the particulate matters according to the present invention by using specific examples, which can be used for measuring the charge characteristics of the particulate matters under different environments.
The specific measurement protocol and results for different humidity conditions are as follows:
the particle environment is simulated by using a mode of igniting and burning incense, an experimental platform is placed in a temperature and humidity controllable artificial climate chamber in the experimental process, and the parameters of the artificial climate chamber are shown in table 1.
TABLE 1 phytotron parameters
Parameter name Parameter value
Model of the device Labonce-22000GS
Temperature setting (. degree. C.) 15-30℃
Humidity setting (RH) 10-90％
Degree of temperature fluctuation (. degree. C.) ±0.5
Temperature deviation (. degree. C.) ±1.0
Deviation of humidity (RH) ±1％
Inner container size (mm) WXDXH 2500×4000×2200
Dimension (mm) WXDXH 2650×4150×2350
Adjusting the temperature and humidity of the climate chamber to required temperature and humidity value, and after the temperature and humidity in the climate chamber are stable, filling the mass concentration of 2mg/m into the climate chamber by igniting incense3The particulate matter of (1). And after waiting for a period of time, measuring and recording the mass concentration of the particulate matters at different positions by using a laser dust measuring instrument so as to ensure the uniform distribution of the particulate matters. 5kV voltage is applied to the upper polar plate, and the corona wire mesh is pressurized to be corona. And adjusting the ion current density at the lower plate from high to low by adjusting the voltage of the corona wire mesh, and recording the composite electric field strength values corresponding to different ion current densities until the ion current density value J is 0. The relative humidity of a constant-temperature and constant-humidity laboratory and the polarities of voltages applied to a corona wire mesh and an upper polar plate are changed, and multiple experiments are carried out.
Fig. 4 shows the measurement results of the ion flow field under different humidity conditions when both the voltages applied to the corona wire mesh and the upper plate are positive or negative.
Processing the ion flow field data in the graph 4 by using a charge parameter measurement principle to obtain charge field parameters theta of the aroma burning particles under different humidityEThe results are shown in FIG. 5.
Under the condition that the field charge parameters are known, the ion flow field data in fig. 5 are processed to obtain the diffusion charge parameters of the particulate matters under different humidity conditions, and the result is shown in fig. 6.
The measurement method provided by the invention can be used for measuring the charge characteristics of the particles in different environments, can measure field induced and diffused charge characteristic components, and provides a theoretical basis for analyzing the ion flow field characteristics of the high-voltage direct-current transmission line in different humidity and particle environments.
The invention also provides a system for measuring the charge characteristics of the particulate matters, which comprises:
the first synthetic electric field intensity acquisition module is used for acquiring the synthetic electric field intensity of the lower polar plate when the ion current density is zero;
the field charge parameter determination module is used for determining field charge parameters by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero;
the particle field charge space charge density determination module is used for determining the particle field charge space charge density according to the field charge parameters;
the second synthetic electric field intensity acquisition module is used for acquiring a plurality of ion current densities when the upper polar plate applies voltage and the corona wire mesh applies voltages of different magnitudes and synthetic electric field intensity at the lower polar plate corresponding to each ion current density;
the diffusion charge parameter determining module is used for determining diffusion charge parameters by utilizing a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity at the lower polar plate corresponding to each ion current density; the diffusion charge parameters comprise a first diffusion charge parameter and a second diffusion charge parameter;
the particle diffusion charge space charge density determining module is used for determining the particle diffusion charge space charge density according to the diffusion charge parameters;
and the particle space charge density determining module is used for determining the sum of the particle field charge space charge density and the particle diffusion charge space charge density as the particle space charge density.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. An apparatus for measuring the charge characteristics of particulate matter in an ionic flow field, the apparatus comprising: the device comprises a corona wire mesh, an upper polar plate, a lower polar plate, a field mill and an ion current plate;
the corona wire mesh, the upper polar plate and the lower polar plate are sequentially and correspondingly arranged from top to bottom; the field mill and the ion flow plate are both arranged on one side of the lower polar plate opposite to the upper polar plate;
the corona wire mesh is used for generating corona discharge after voltage is applied to generate ion flow, and ions in the ion flow are adsorbed on the particles between the upper polar plate and the lower polar plate to form charged particles;
the ion flow plate is used for measuring the density of the ion flow;
the lower polar plate is grounded, the upper polar plate is used for generating a nominal electric field between the upper polar plate and the lower polar plate after voltage is applied, and the nominal electric field, charged particles and ions jointly act to form a synthetic electric field;
the field mill is used for measuring the resultant electric field intensity at the lower polar plate.
2. The device of claim 1, further comprising: a first high voltage direct current power supply and a second high voltage direct current power supply;
the first high-voltage direct-current power supply is connected with the corona wire mesh and used for applying first voltages with different magnitudes to the corona wire mesh;
and the second high-voltage direct current power supply is connected with the upper polar plate and is used for applying a second voltage to the upper polar plate.
3. The device of claim 1, further comprising: a plurality of fixed brackets;
the plurality of fixing supports are used for fixing the corona wire mesh, the upper polar plate and the lower polar plate.
4. A method for measuring the charge characteristics of particles based on the device for measuring the charge parameters of the particles in the ionic flow field according to any one of claims 1 to 3, wherein the method comprises the following steps:
acquiring the synthetic electric field intensity of the lower polar plate when the ion current density is zero;
determining field charge parameters by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero;
determining the field charge space charge density of the particulate matters according to the field charge parameters;
acquiring a plurality of ion current densities when the upper polar plate applies voltage and the corona wire mesh applies voltages of different magnitudes and the resultant electric field intensity at the lower polar plate corresponding to each ion current density;
determining diffusion charge parameters by using a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity of the lower polar plate corresponding to each ion current density; the diffusion charge parameters comprise a first diffusion charge parameter and a second diffusion charge parameter;
determining the diffusion charge space charge density of the particulate matter according to the diffusion charge parameters;
and determining the sum of the particulate matter field charge space charge density and the particulate matter diffusion charge space charge density as the particulate matter space charge density.
5. The method of measuring the charge characteristics of particulate matter according to claim 4, wherein the step of obtaining the resultant electric field strength at the bottom plate when the ion current density is zero further comprises:
determining a field charge parameter as
Figure FDA0003365144770000021
In the formula, thetaEIs a field charge parameter,. epsilon0Is the dielectric constant of air, epsilonpIs the relative dielectric constant of the particulate matter, d is the particle size of the particulate matter, and ρ is the mass density of the particulate matter;
according to the space charge density expression of the particulate matter generated by diffusion charge, determining the diffusion charge parameter as
Figure FDA0003365144770000022
In the formula, thetad1、θd2Respectively a first diffusion charge parameter and a second diffusion charge parameter, KBIs Boltzmann constant, T is the absolute temperature of the environment, e is the electronic charge, T is the charge time, mjIs the jth ion mass;
constructing an expression of the space charge density of the particulate matter as rho according to the field charge parameter and the diffusion charge parameterw＝θEmcE+θd1mcln(1+θd2ρe) (ii) a In the formula, ρwIs the space charge density of the particles, E is the electric field strength at the lower plate, mcIs the mass concentration of the particulate matter, peIs the ion space charge density.
6. The method for measuring the charge characteristics of the particulate matters according to claim 5, wherein the field charge parameters are determined by a least square method according to the synthetic electric field intensity at the polar plate when the ion current density is zero, and the method specifically comprises the following steps:
the expression of the synthesized electric field intensity at the lower polar plate when the ion current density is determined to be zero is
Figure FDA0003365144770000031
In the formula, EgThe resultant electric field intensity, U, at the lower plate when the ion current density is zero2The voltage applied to the upper polar plate is h, and the distance between the upper polar plate and the lower polar plate is h;
and solving the expression of the synthetic electric field intensity at the lower polar plate when the ion current density is zero by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero to obtain field charge parameters.
7. The method for measuring the charge characteristics of the particulate matters according to claim 6, wherein the step of determining the field charge space charge density of the particulate matters according to the field charge parameters specifically comprises the following steps:
according to the field charge parameters, using a formula rhoE＝θEmcEgDetermining the field charge space charge density of the particulate matters;
in the formula, ρEIs the particulate field charge space charge density.
8. The method for measuring the charge characteristics of the particulate matters according to claim 7, wherein the determining of the diffusion charge parameters by using a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the resultant electric field intensity at the lower plate corresponding to each ion current density specifically comprises:
according to the control equation of ion flow field
Figure FDA0003365144770000032
And the expression of the space charge density of the particles, and the synthetic electric field at the lower polar plate is constructed asA function of diffusion charge parameter of Ek＝f(θd1,θd2) (ii) a In the formula (I), the compound is shown in the specification,
Figure FDA0003365144770000033
for potential, J is ion current density, k is ion mobility, EkA composite electric field;
establishing an error function of
Figure FDA0003365144770000034
Wherein S () is an error function, EkiAnd E'kiRespectively a measured value and a calculated value of the ith time of the synthesized electric field intensity at the lower polar plate, wherein n is the total number of times of measurement;
and determining the diffusion charge parameters by using a two-dimensional particle swarm algorithm based on the function and the error function of the diffusion charge parameters of the synthesized electric field at the lower plate according to the field charge parameters, the ion current densities and the synthesized electric field intensity at the lower plate corresponding to each ion current density.
9. The method for measuring the charge characteristics of the particulate matters according to claim 8, wherein the step of determining the diffusion charge space charge density of the particulate matters according to the diffusion charge parameters specifically comprises the following steps:
according to the diffusion charge parameters, using a formula rhod＝θd1mcln(1+θd2ρe) Determining the diffusion charge space charge density of the particulate matters;
in the formula, ρdThe charge space charge density is the particle diffusion charge.
10. A particulate matter charge characteristic measurement system, comprising:
the first synthetic electric field intensity acquisition module is used for acquiring the synthetic electric field intensity of the lower polar plate when the ion current density is zero;
the field charge parameter determination module is used for determining field charge parameters by using a least square method according to the synthetic electric field intensity at the lower polar plate when the ion current density is zero;
the particle field charge space charge density determining module is used for determining the particle field charge space charge density according to the field charge parameters;
the second synthetic electric field intensity acquisition module is used for acquiring a plurality of ion current densities when the upper polar plate applies voltage and the corona wire mesh applies voltages of different magnitudes and synthetic electric field intensity at the lower polar plate corresponding to each ion current density;
the diffusion charge parameter determining module is used for determining diffusion charge parameters by utilizing a two-dimensional particle swarm algorithm according to the field charge parameters, the ion current densities and the synthetic electric field intensity at the lower polar plate corresponding to each ion current density; the diffusion charge parameters comprise a first diffusion charge parameter and a second diffusion charge parameter;
the particle diffusion charge space charge density determining module is used for determining the particle diffusion charge space charge density according to the diffusion charge parameters;
and the particle space charge density determining module is used for determining the sum of the particle field charge space charge density and the particle diffusion charge space charge density as the particle space charge density.
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