SU550560A1 - Device for measuring the dispersed composition of aerosols - Google Patents

Description

one

This invention relates to an analysis of variance.

A device for determining the size distribution of particles is known. The test gas is pumped over the surface of the liquid to saturate it with condensable vapors, after which it enters the bubble chamber, where a three-dimensional AC field is created using three electrodes (grids). Two electrodes have the form of flat disks, and the third is made in the form of a cylindrical surface. The charged particles, which have a charge-to-mass ratio, are placed in a certain range of e, are fixed in the volume of the chamber, the rest are scattered and deposited on the walls of the chamber. With a subsequent decrease in temperature, the steam condenses on the particles. The concentration of the resulting droplets is measured using a photomultiplier light source recording the scattered radiation. By varying the voltage on the electrodes and the frequency, it is possible to take a curve of the distribution of particles with respect to charge-to-mass ratios. In the case of neutral particles, the ionizing radiation source 1 is used for charging.

The known device is characterized by the complexity of the setting in operation.

A known spectrometer for determining the size distribution of electrically charged aerosol particles. The jet spray is blown between two plates to which an electrical voltage is applied. The distance from the point of entry to the point of collision of particles with the surface of the plate depends on the diameter of the particles 2.

The device does not provide a wide range of measured aerosols.

The closest technical solution.

is a device containing corona discharge electrodes, deposition electrode for charged particles, a measuring electrode installed in series in an aerosol stream moving at a constant speed,

as well as an electrometer connected to the measuring electrode, and a recorder, the input of which is connected to the output of the electrometer. Aerosol particles acquire electric charge in the field of corona discharge.

The space of the deposition electrodes, to which a constant voltage is applied, precipitates a part of the aerosol particles, depending on the dispersed composition and magnitude of the voltage. Unsettled particles are carried along stream

measuring electrode. The charge of these particles Q, proportional to their concentration, is measured by an electrometer, the output of which is fed to the recorder. All particles are retained on the deposition electrodes,

having diameters greater than the limiting magnitude of the capacitance determined by the voltage across these electrodes, as well as some of the particles having diameters smaller than the limiting one. The charge of this particle is the measurement error, which is caused by the difference in coordinates of the entry of individual particles into the space of the deposition electrodes.

In the known device for reducing the error, the aerosol is passed through a system of electrodes in the form of a narrow beam, the area whose cross section is not more than 5% of the area covered by the outer deposition electrode. According to the results of a series of consecutive measurements of the charge Q, carried out at different values of the voltage on the deposition electrodes, the dispersed composition 3 is judged.

The known device is characterized by low accuracy and sensitivity. The low accuracy is due to the replacement of the continuous distribution function by its stepwise approximation, and also the fact that the error due to the difference in the input coordinates of the individual particles is not completely eliminated. The low sensitivity is due to the low representativeness of the aerosol sample, which is determined for the device in question by the cross-sectional area of the aerosol stream, which cannot be increased without decreasing the measurement accuracy.

In order to increase the accuracy and sensitivity of the measurement of the aerosol dispersion composition, the power supply unit for the deposition electrodes is made in the form of an exponential voltage generator, the output of which is connected to one of the recorder inputs, its other input through the adder is connected to an electrometer, and it is equipped with a charge differentiator that arrives to the electrometer, the input of this unit is connected to the measuring electrode, and the output is to the summator.

The charge q q of those particles with diameters smaller than the limiting ones that emerge from the flow under the action of the besieging field is equal to

dQ

dQ

,

before

Pre d (In bpred) au

Due to the fact that the voltage U on the deposition electrodes is an exponential function of time with a constant τ, the value of bpred varies in time with the law

1n (5 "red) -.

This makes it possible

dQ

charge measurement q equal to

with dd

the power of the charge determination unit introduced into the device and the registration of the total charge of all particles with sizes smaller than the limiting, as a continuous function of the charge to measuring the charge q, the error of the charge is due to the difference in the input coordinates of the individual

particles in the space of the deposition electrodes is completely eliminated, so it is possible to increase the sensitivity of the measurement, the flow of aerosol through the electrode system,

having a cross section equal to the cross section bounded by the external deposition electrode.

The drawing shows a diagram of an apparatus for measuring the dispersion composition of aerosols.

In the aerosol flow, the outer and inner corona discharge electrodes 1 and 2 are installed, the outer and inner electrodes 3 and 4 of the deposition of charged particles, and the measuring electrode 5, to which are connected

the inputs of the electrometer 6 and the block 7 of differentiation of the charge supplied to the electrometer. The outputs of the electrometer 6 and block 7 are connected to the inputs of the adder 8. The electrodes 3 and 4 are connected to an exponential voltage generator 9. The output of the adder and the output of the generator are connected to the inputs of the recorder 10.

A stream of aerosol is passed through the electrode system throughout its cross-section at a constant rate. In the space of electrodes 1 and 2 is carried out, the corona discharge. The aerosol particles, the passage between these electrodes, acquire an electric charge. All charged particles, the diameters of which exceed the value of bpred, determined by the intensity of the electric field between the electrodes 3 and 4, are deposited on one of these electrodes. An electric field is generated by an exponential voltage generator 9 with a constant time t.

Particles remaining in the flow arrive at the measuring electrode 5 and their charge Q is recorded by the electrometer 6. To determine the charge, the input of unit 7 is connected to the measuring electrode, which differentiates the charge Q by time and amplifies the resulting magnitude in times. The signal at the input of the adder 8 is proportional to

the sum of the charges Q and, and, consequently, is proportional to the concentration of particles having diameters smaller than bpred. This signal is continuously recorded by the recorder 10.

At the same time, the second input of the recorder receives a signal proportional to the current value of the generator voltage 9, which makes it possible to assign to each value a value of this voltage and,

therefore, each value is the concentration of particles.

The proposed device allows to improve the measurement accuracy by registering the dispersion composition as a continuous

the functions of particle size and elimination of the error due to the difference in the coordinates of the entry of particles into the space of the deposition electrodes and increase the sensitivity by at least 20 times due to an increase in the representativeness

aerosol samples.

Claims (1)

Formula of inventions A device for measuring the dispersed composition of aerosols containing successively installed corona discharge aerosols in the flow of the electrode, deposition electrodes of charged particles with a power supply unit, a measuring electrode, an electrometer connected to the measuring electrode, and a recorder, characterized in that, in order to improve accuracy and measurement sensitivity, the power supply unit of the deposition electrodes is made in the form of an exponential voltage generator, the output of which is connected to one of the recorder inputs, the other er The input through the adder is connected to the electrometer, and it is equipped with a charge differentiation unit supplied to the electrometer, the input of this unit is connected to the measuring electrode, and the output to the adder. / O771Of aerosis