RU2536355C2 - Pyrometric sensor of coordinates of fire source with field stop - Google Patents

Abstract

FIELD: fire safety.

SUBSTANCE: pyrometric sensor comprises a light flux splitter, light filters with different transmission spectra, and radiation receivers consistently mounted and optically connected into an optical system, it additionally comprises a field stop with a variable distribution law of transparent and opaque areas, mounted after the light flux splitter in one of the optical channels, the executive circuit additionally comprises a stop control unit, and single-element non-coordinate radiation receivers are used as the radiation receivers.

EFFECT: ensuring the possibility of recording radiation of fire sources shifted relative to the optical axis of the sensor, increasing the probability of correct detection of the fire source, increasing the sensor operation speed and reliability of determining coordinates of the fire source, increase in sensitivity, reliability and interference immunity of the sensor, which enables to improve the efficiency of a fire-extinguishing system or explosion-suppression.

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Description

The invention relates to the field of hazard warning systems, in particular to fire alarm and explosion suppression devices, and is intended to detect a source of ignition in gas-dispersed media by radiation from a source of elevated temperature and to determine two-dimensional coordinates of a source of ignition by thermal radiation. The pyrometric sensor as part of an active fire extinguishing or explosion suppression system can be used in all areas of production dangerous for fires and explosions of a gas-dispersed medium. Such industries include coal mining, flour milling, woodworking, paint and varnish, metallurgical, oil and gas.

In connection with the widespread occurrence of potentially hazardous industries, it becomes necessary to develop sensors capable of detecting a source of ignition by its radiation at an early stage, which is located in any zone of the sensor’s angular field.

Known photoelectronic scanning systems for scanning images in space [1]. The lens of the receiving optical system builds an image of the entire field of view in the plane of the sensitive layer of the radiation detector of the photoelectronic scanning system.

The disadvantages of these scanning systems are the low speed associated with the long reading time of the electrical signal from the coordinate photoelectric radiation receiver, as well as the influence of the optical characteristics of the medium on the correct determination of the brightness (temperature) of the object. This makes it impossible to use such sensors in explosion suppression systems in gas dispersed environments.

Known pyrometric coordinates of the ignition source [2, prototype], in which the listed disadvantages are eliminated. The sensor contains a sequentially installed optical system, a luminous flux separator, filters with different transmission spectra, single-axis radiation detectors (OPI) located perpendicular to each other and the optical axis of the sensor, and the outputs of the receivers are connected to the input of the executive circuit, but this sensor also has a drawback that the image from a point emitter (for example, a fire at the initial stage) displaced relative to the optical axis of the sensor does not fall (is not projected) onto one or ba OPI, which leads to the omission of the initial moment of ignition.

Known pyrometric coordinates of the ignition source with cylindrical lenses [3], built on the basis of the OPI. The disadvantage of this sensor is that, as a result of introducing two cylindrical lenses into the optical system, the level of energy supplied to the optical arrester when determining the initial stage of ignition is comparable to the receiver’s own noise, which significantly reduces the probability of a signal being detected correctly and can lead to the ignition being ignored or fire detection after an unacceptably long period of time.

In addition, the prototype and analogues have a number of disadvantages due to the use of multi-element OPI [1]. At the same time, the use of multi-element impedance arrays with full electrical isolation of individual sensitive elements leads to the following sensor disadvantages:

- low resolution caused by the significant overall dimensions of the individual elements of the IPI;

- a decrease in the reliability of the sensor due to the large number of independent elements of the OI;

- the need for the introduction of correction factors to ensure the identity of the parameters of individual elements of the IPI.

The use of multi-element impedance arrays with internal electrical connections leads to the following sensor disadvantages:

- a decrease in the reliability of the sensor due to the need to take into account the mutual influence and dispersion of the parameters of individual elements of the arrester, the presence of switching transients and leaks on live busbars and substrates, as well as the influence of specific noise of the arrester;

- a decrease in the reliability of the sensor due to failure of the entire arrester in the event of loss of sensitivity of one of the elements of the arrester;

- restriction on the choice of the algorithm for polling the OPI due to the impossibility of arbitrary sampling of a signal from any element.

The essence of the proposed technical solution consists in introducing into the pyrometric sensor the coordinates of the source of ignition of the field diaphragm with a variable distribution law of transparent and opaque sections located after the light flux separator in one of the optical channels. Field diaphragm is a set of independently controlled devices that provide temporary overlap and subsequent transmission of the light flux for a certain period of time - optical shutters.

The proposed pyrometric coordinate sensor of the ignition source with a field diaphragm is shown in the diagram (Fig. 1).

The device comprises an optical system 1 intended for focusing the light flux on the sensitive windows of the radiation detectors, a light flux divider 2, a field diaphragm with a variable distribution law of transparent and opaque sections 3, filters 4 and 4 'with different transmission spectra, single-element non-coordinate radiation receivers 5, Executive circuit 6, comprising a diaphragm control unit (ECU), a calculation unit (BV), and an electric pulse generation unit (FFE).

Pyrometric coordinates of the source of ignition with a field diaphragm operates as follows.

The radiation of the controlled area is collected using the optical system 1 and is divided by the light flux separator 2 into two streams (optical channels). Each of these flows is focused on single-element non-coordinate radiation detectors, at the same time, a narrow energy spectrum is extracted with filters 4 and 4 'to provide the possibility of determining the temperature of the source of ignition by the spectral ratio method. The coordinates of the source of ignition are determined using a field diaphragm 3 installed in one of the optical channels, each optical shutter of which, according to a certain algorithm, transmits or blocks the light flux. The coordinates of the radiation source are determined by the number of the optical shutter of the field diaphragm, when opened, the signal at the output of the radiation receiver reaches its maximum value.

Signals from non-coordinate single-element radiation receivers are fed into the executive circuit 6 to a calculation unit (BV), which converts them to digital values, performs software filtering of interference, calculates the coordinates of the source of ignition, calculates the ratio of electrical signals from single-element non-coordinate radiation receivers and compares the obtained ratio with a predefined set value for deciding on the occurrence (or absence) of a fire. The diaphragm control unit (ECU) controls the optical shutters of the field diaphragm in accordance with the algorithm specified by the calculation unit (IW). In the event of a fire, the actuating circuit 6 generates a control signal to the corresponding explosion suppressing device using the electric pulse forming unit (BFE).

An example of an optical shutter satisfying the performance requirement is a liquid crystal optical shutter built on the basis of a double pi cell. The response period of a double pi cell (opening time, open time, and closing time) is 0.25 ms [4]. According to the technical requirements for an optoelectronic sensor for detecting a source of ignition at an early stage, the time for a sensor to make a decision about the occurrence (absence) of ignition should not exceed 3 ms [5, 6]. Thus, the interrogation time of the field diaphragm, composed of nine independent optical shutters built on the basis of a double pi-cell, meets the technical requirement for speed.

The introduction of a field diaphragm and a diaphragm control unit provides selective transmission of radiation from predetermined sections of the controlled object (object scanning). As a result of scanning:

- it becomes possible to register the coordinates of the radiation of the fires, offset relative to the optical axis of the sensor, by non-coordinate radiation receivers, which increases the likelihood of correct detection of the fire at an early stage and its location;

- improves the speed of the sensor and the reliability of determining the coordinates of the source of ignition through the use of a field diaphragm, which allows for arbitrary sampling of the signal.

The use of single-element non-coordinate radiation detectors has a number of indisputable advantages, namely, it increases the sensitivity, reliability and noise immunity of the sensor.

The absence of the influence of the intermediate medium (such characteristics as humidity and dust) and the distance to the source of ignition on the reliability of the sensor will allow the device to be used in environments characterized by complex optical conditions.

The pyrometric coordinate sensor of the ignition source with a field diaphragm has successfully passed laboratory tests.

Currently, BTI AltGTU is actively cooperating with coal mines of the Kemerovo region in the field of development and implementation of fire detection sensors.

Information sources

1. Yakushenkov Yu.G. Theory and calculation of optoelectronic devices. [Text] // Yu.G. Yakushenkov. - 3rd ed. - M.: Engineering 1989. 360 s: silt.

2. RF patent No. 2318242.

3. RF patent No. 2459269.

4. Products of the Research Institute "Photon" [Electronic resource] / Access mode: http://lcd-foton.com/products/konstrukciya/.

5. Optoelectronic device for detecting the initial stage of explosion development in gas dispersed systems. The dissertation for the degree of candidate of technical sciences. Sypin E.V. - Biysk: 2007 .-- 144 p.

6. Optoelectronic system for determining the three-dimensional coordinates of the explosion in gas dispersed systems at the initial stage. The dissertation for the degree of candidate of technical sciences. Pavlov A.N. - Biysk: 2010 .-- 134 p.

Claims (1)

A pyrometric sensor of coordinates of the source of ignition, containing a sequentially mounted and optically coupled optical system, a light splitter, filters with different transmission spectra and radiation detectors, the outputs of the radiation detectors are connected to the input of the actuator circuit, characterized in that it further comprises a variable field diaphragm installed after the separator luminous flux in one of the optical channels and representing a set of independently controlled optical shutters c, the actuating circuit further comprises a diaphragm control unit with the ability to control the optical shutters of the field diaphragm according to an arbitrary algorithm, and single-element non-coordinate radiation receivers are used as radiation detectors.