RU2335761C1 - Acoustooptical indicator of dangerous gas critical concentration - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: indicator unit contains ultrasonic generator, piezoceramic converter, narrow band optical filter, photosensitive device, electronic amplifier, indicators of dangerous gas critical concentration and independent supply unit. Output of ultrasonic generator is connected to input of piezoceramic converter. And output of photosensitive device is connected to input of electronic amplifier output of which is connected to input of dangerous gas indicator in gas mix.

EFFECT: higher indication reliability and efficiency.

4 cl, 1 dwg

Description

The invention relates to devices for the rapid detection of critical concentrations of hazardous industrial gases and can be used mainly in the chemical, oil and gas, coal and other industries.

Technical solutions of a similar nature are well known in the art.

Thus, prior art devices are known for determining the concentration of components of industrial gases, for example, an acoustic gas analyzer, which is a working chamber made in the form of a resonator — a hollow cylinder with a height equal to an odd number of sound half-waves, and with holes located in the middle of the height, and the source and sound receiver mounted at the ends of the resonator. The acoustic gas analyzer also has an electronic circuit for generating, receiving sound and measuring frequency, see, for example, description of application No. 2142131, G01N 29/00, 1998.

Also known are methods including, for example, dividing the gas composition into individual components in a chromatographic column, followed by measuring their concentrations and identifying the components that are produced using an acoustic resonator — a torsional vibration resonator, see, for example, description to application No. 93037030, G01N 30/76, 1996.

In addition, methods and devices based on them for determining the composition of microimpurities of various substances in gases are known from the prior art, in particular by chromatography, which increase the sensitivity and resolution of detecting microimpurities of substances in a gas. Thus, a device is known in which a synchronization unit and a coupled multi-frequency oscillatory system are introduced. One of the capacitors of the system are two parallel electrodes. The coupled multi-frequency oscillatory system, the pulse shaper and the synchronization unit form a closed feedback loop, see, for example, description of application No. 1412447, G01N 27/62, 1998.

The disadvantages of such devices and methods include the relative complexity of their technical implementation, the obvious high requirements for the accuracy and stability of elements (resonators, collimators, etc.) and parameters (frequency of the acoustic wave), etc., which can make their use difficult and unreasonable, especially in mass production.

In addition, technologies of a similar purpose disclosed in the descriptions of foreign security documents, for example, SU 832447 A, 05.23.81, are known from the prior art. SU 853520 A, 08/07/81. SU 661327 A, 05/15/79. RU 2039971 C1, 07.20.95. FR 2091258 A, 01/14/72. EP 0180068 A2, 05/07/86.

In addition, devices for spectral analysis of gases are known from the prior art, see, for example, description to application No. 94037443, G01N 21/61, 1997 (closest analogue). The optical gas analyzer under consideration contains n optical channels, each of which contains a collimator, a controlled interference polarizing filter, a photodetector, and n measuring channels, each of which contains an automatic signal level control circuit, an amplifier, a synchrodetector, and an oscillator. To improve the operational characteristics and expand the functionality of the gas analyzer, it is additionally equipped with movable reference measuring cuvettes with a control unit, executive control units for the automatic signal level control circuit, amplifiers, an oscillator, a signal encoding unit, an interrogating unit, computing and software devices. The operation of the entire gas analyzer as a whole is controlled by a computing device. The presence of additional devices allows normalization of the output signal, eliminating the influence of optical noise on its value, recording the value of the zero signal, excluding its drift, increasing the degree of measurement reliability by improving the signal quality and eliminating the inadequate response of the device to the degree of illumination of the path, as well as to changes in power supply stresses.

The disadvantages of all of the above analogues should include their increased overall mass characteristics and power consumption, as well as lack of efficiency. This is due primarily to the fact that the use of acoustic waves in devices requires the creation of resonators that are comparable in size to at least the length of the acoustic wave, and the excitation of an acoustic wave requires appropriate energy consumption. When solving a specific task of prompt notification of the presence of specific dangerous gas components (for example, natural gas, methane, etc.) in a gas mixture (for example, air), the use of such devices is either impossible (a time interval for a technical analysis of the composition of the gas mixture is required), or unreasonably expensive .

The problem to which the invention is directed, is to create a device suitable for mass production with the ability to quickly detect and signal the presence of critical concentrations of hazardous gases in the air.

When implementing this invention, several technical results are achieved, one of which is to increase the degree of reliability of detecting the presence of critical concentrations of hazardous gases in the air while reducing overall weight and mass characteristics and energy consumption.

This problem is solved by using the method of spectral analysis of a luminous gas mixture for the presence of dangerous gas spectral lines in it. Excitation of the gas mixture to the level of luminescence is realized using a new phenomenon called acoustoluminescence in physics. This ensures the safety and efficiency of the indication of maximum concentrations of hazardous gases. As detecting devices, photosensitive devices are used that are configured in advance to detect spectral lines of hazardous gases in the acoustoluminescence spectrum of a gas mixture.

The physical basis for the operation of such an acoustic gas analyzer is the emission of light by the analyzed gas upon excitation of surface acoustoluminescence by ultrasonic vibrations / 1 /. During the propagation of an ultrasonic (hereinafter referred to as ultrasound) wave along the surface of a piezoelectric crystal, the piezoelectric field accompanying the ultrasound penetrates outside the crystal into the surrounding space. If the crystal is surrounded by air, then it can be excited to the level of microdischarges. The easiest way to excite intense ultrasonic vibrations in thin plates called resonators.

The piezoelectric field associated with ultrasonic vibrations in a piezoelectric crystal can be significantly stronger than the exciting applied to the resonator. When oscillating at a resonant frequency, half the wavelength of the ultrasound fits within the plate thickness. The calculation gives such a value of the piezoelectric field E _n / 1 /.

,

,

where the strength of the external applied field is V / 2h, Q is the mechanical Q factor, and K is the electromechanical coupling coefficient of the crystal.

Therefore, E _n can be stronger than the applied field. In good piezoelectrics, E _n can be tens or hundreds of times higher than applied. It is not possible to make contact on the entire surface of the piezoelectric, and then the piezoelectric field penetrates from the piezoelectric plate into the environment. This field is capable of supporting the glow of a gas discharge. The experiments on the initiation of a gas discharge at atmospheric pressure were carried out with LiNbO ₃ resonators 0.14-3 mm thick with a length and width from a few millimeters to several centimeters / 1 /. When an exciting voltage was applied to the LiNbO ₃ plate, ultrasonic vibrations were excited in it due to the intrinsic piezoelectric effect. At frequencies close to the resonance and a voltage greater than a certain threshold value, a gas discharge in the form of violet dots is excited at the surface of the sample. The studies were conducted in the frequency range of 0.4-16 MHz using continuous and pulsed excitation modes of ultrasound. In all cases, a gas breakdown and a gas discharge were observed around the air sample. In the spectrum of the luminous discharge, the lines of nitrogen and oxygen that make up the air / 1 / are confidently distinguished.

The appearance of additional lines in the spectrum of the glowing gas discharge will indicate the presence in the gas itself, in this case air, of additional components, including hazardous gases.

Thus, additional lines in the spectrum of a gas discharge are an identification sign of the presence of additional components in air.

The detection of this identification characteristic is carried out using a photo-recording device having a sensitivity at the level of maximum permissible concentrations of dangerous gases and spectral selectivity at frequencies characteristic of the spectral lines of dangerous gases.

Below is a description of the graphic materials, in no way limiting all possible embodiments of the claimed invention.

The drawing shows a variant of the block diagram of the device, the numbering of blocks and elements and the abbreviations used below.

1 - piezocrystal (PC),

2 - ambient gas environment (OGS),

3 - conditionally shown spectral lines of the luminous OGS,

4 - ultrasonic generator (UZG),

5 - photo-recording device (FRU),

6 - narrow-band optical filter (UOF),

7 - electronic amplifier (EU),

8 - sound generator (ZG),

9 - sound indicator (ZI),

10 - matching amplifier (SU),

11 - light indicator (SI),

12 - self-contained power supply (ABP),

13 - "network" output (CB),

14 - the central control point (CCP),

15 - contact plates (KP) PC.

The current state of the art makes it possible to carry out equipment for a device for detecting the limiting concentration of hazardous gas in both stationary and portable versions.

As photographic equipment recording the spectral line and the limiting concentration of hazardous gas, one can use, for example, a photomultiplier tube (PMT) or another device, for example, based on charge-coupled devices (CCDs) equipped with a narrow-band filter configured to pass the hazardous spectral line gas. The sequence of operation of the device. The signal from the output of the ultrasonic ultrasonic wave (4) enters through the CP (15) to the input of the PC (1) and excites ultrasonic vibrations in it. At the same time, the acoustoluminescence of the near-surface OGS layer is excited (2).

Since a narrow-band optical filter is configured to transmit light of a certain spectrum, namely the spectral line of a hazardous gas, if it is not included in the OGS (2), there is no signal at the output of the switchgear (5). When the near-surface OGS layer (2) appears in the acoustoluminescence spectrum of the hazardous gas component and the integral intensity of its spectral line characterizing the critical concentration of the hazardous gas, an electrical signal is generated at the output of the switchgear (5), which is amplified by an electric amplifier (7) and supplied through the control system (10 ) on SI (11) and through ЗГ (8) on ЗИ (9), which leads to the formation of a light and sound signal “Danger!”.

When using the device as a sensor in a network of similar sensors covering some protected space (for example, a large chemical workshop), a signal is also formed at its CB (13). Any interface can be connected to the output of the CB (13), for example, a wired or wireless electric or fiber-optic channel for communication with the CPC (14) of the presence of hazardous impurities in the controlled gas mixture.

Thus, the use of the proposed device provides reliable and prompt notification of the presence in the working gas mixture, for example, in the air of additional components, in particular, hazardous gases. Due to the lack of expensive elements in the structure of the device and the possibility of its mass production, such devices can be made in the form of wearable individual sensors or cover the protected space with a network of sensors. As an example, we can recommend the use of a network of such indicators in coal mines, gas producing, gas processing and gas pumping enterprises and in chemical industry facilities, etc.

Information sources

1. Ostrovsky I.V. Acoustoluminescence is a new phenomenon of acoustooptics. Soros Educational Journal, 1998, No. 1.

Claims (4)

1. An acousto-optic indicator of critical concentrations of hazardous gases based on the analysis of the spectral composition of the gas mixture, characterized in that, for the rapid detection and indication of the presence of hazardous gases in the gas mixture, an ultrasonic generator, a piezoceramic transducer, a narrow-band optical filter, and a photosensitive device are introduced into it , an electronic amplifier, indicators of critical concentrations of hazardous gases and an autonomous power supply, the output of the ultrasonic generator connected to move the piezoceramic converter and the output of the photosensitive device is connected to the input of the electronic amplifier, whose output is connected to the input of the indicator in the presence of a gas mixture of hazardous gases. 2. The acousto-optic indicator of critical concentrations of hazardous gases according to claim 1, characterized in that the luminescence of the surface layer of the surrounding gas mixture is caused by using the optical effect of acoustoluminescence. 3. The acousto-optic indicator of critical concentrations of hazardous gases according to claim 1, characterized in that the level of critical concentration of hazardous gas is determined by the intensity of its spectral line. 4. The acousto-optic indicator of critical concentrations of hazardous gases according to claim 1, characterized in that optical and audible alarms can be used as an indicator of critical concentration of hazardous gas.