SU1747806A1 - Method of flame check - Google Patents

Abstract

The invention relates to a power system, namely the automation of combustion processes. The ultraviolet radiation of the flame is converted into electrical pulses by shutting off the radiation flux to the detector using an optical shutter, the number of pulses is measured with the shutter open and closed, the illumination time of the detector is controlled in inverse proportion, and the dimming control is directly proportional to the number of pulses at the detector output in the light and dark phases, respectively, form a signal of the presence of a flame upon reaching a predetermined amount of the cycles of radiation flow overlap per unit of vacuum and the malfunction signal at an overlap duration equal to the value of the permissible inertia of the control system of the flame. 1 silt

Description

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The invention relates to a power system, namely to the automation of combustion processes, and can also be used in gas, oil refining, chemical, metallurgical and other sectors of the national economy.

A known method of controlling the flame by ultraviolet radiation, in which the number of pulses at the detector output per unit of time is measured and generates a signal of the presence of a flame when a specified number of pulses are reached.

The disadvantage of this method is the low reliability of flame control due to the loss of key properties by the detector and the transition to the self-discharge mode due to the aging of the optical sensor under the influence of ultraviolet radiation of a high intensity flame.

characteristic of the regime of the nominal load of the controlled unit.

There is also known a method of controlling the flame by converting ultraviolet radiation into electrical pulses by blocking the radiation flux on the detector for a constant predetermined time using an optical shutter, measuring the number of pulses at the detector output with the shutter open and closed and generating a given number of pulses with the open shutter, and a malfunction signal - when the specified number of pulses is reached with the shutter closed

This method allows monitoring of the health of the detector. However, the increased current load of the detector reduces the reliability of the method

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The purpose of the invention is to increase reliability by reducing the current load of the detector while maintaining sensitivity.

To do this, in the flame monitoring method, by converting ultraviolet radiation into electrical pulses by blocking the radiation flux on the detector with an optical shutter, measuring the number of pulses at the detector output with the shutter open and closed, the illumination time of the detector is controlled in inverse proportion to - directly proportional to the number of pulses at the detector output in the light and dark phases, respectively, and the signal n Flame faults are formed when a specified number of cycles of radiation flow overlap per unit time is reached, and a malfunction signal is generated at an overlap duration equal to the value of the permissible inertia of the flame control system.

The drawing shows a diagram of the device control flame, implementing the proposed method.

The device contains an optical detector 1, one electrode of which through a resistor 2 is connected to terminal 3, to which an alternating voltage is supplied, and the other electrode through a matching circuit 4 is connected to the output of control key 5, performed on the thyristor b, in which the anode coil is connected the relay 7, and the cathode one - the load in the form of a resistor 8, the Electromagnetic relay 7 is connected to terminal 9, which is supplied with a pulsating voltage, the Device also contains a optical shutter in the form of a curtain 10 for a periodic attenuating detector 1, driven by winding 11, which is connected to electric pulse generator 12 by shutter 10, a second key 13 containing a thyristor 14, the anode of which is connected to the winding of electromagnetic relay 15, one of the outputs of key 13 is connected to generator 12, and the other - to key 5 controls. The anode of the light emitting diode 16 is connected to the matching circuit 4, and the cathode to the input of the integrator 17, consisting of resistors 18 and 19 and a capacitor 20, the output of which is connected to the threshold element 21 connected to the generator 12.

The method is carried out as follows.

In the presence of a flame, the luminous flux through the open optical shutter-shutter 10 acts on the optical detector 1 of the flame, which goes into conducting

condition. As a result, the electrical pulses are fed through the matching circuit 4 to the input of the control key 5 and through the light-emitting diode 16 to the input of the integrator 17. At the output of the integrator 17 under the influence of electrical pulses received through the light-emitting diode 1 b due to the charge of the capacitor 20 through the resistor 18, an increasing voltage is formed with a rate of increase directly proportional to the intensity of the radiation. When the voltage Ui reaches the upper switching level Urm of the threshold element 21, the latter switches on the generator

12 controls the shutter 10, which blocks the light flux. The optical detector goes to a non-conducting state, the flow of pulses to the inputs of the matching circuit and the integrator 4 stops.

17. At the output of the integrator 17, the voltage Ui is reduced by discharging the capacitor 20 through the resistor 19 to the value of the lower switching level Unn of the threshold element 21, which turns off the generator

12, the shutter 10 goes into the open state and, if a flame is present, the cycle repeats. At a certain number of shutter switching cycles per unit of time, specified by the delay value

on switching on the relay 7, the latter switches, producing a flame presence signal. During the period of darkening of the detector 1, the relay 7 remains in the excited state due to the effect of a shutdown delay.

When the shutter 10 overlaps the luminous flux, a monitoring mode of the optical detector 1 of the flame is provided. An electric pulse from the output of the generator 12 simultaneously enters and

one of the inputs of the second key 13. However, when the detector has a dim detector 1 and is in good condition, there are no pulses on the other input of the second key 13. Therefore, the second key 13 is in a disabled state. If, with a darkened detector 1, the second key 13 is in the on state, this indicates that the detector 1 is faulty and generates pulses in the absence of a flame. Insofar as

through the winding of the electromagnetic relay 15, the anode of the thyristor 14 receives pulses from the generator 12, and the control electrode pulses from the cathode of the thyristor b of the control key 5, the thyristor 14 switches on the electromagnetic relay 15, whose contacts are used in the protection circuit of the combustion chamber. Under conditions of varying intensity of radiation, the device ensures the constancy of the light exposure due to

control of the optical detector illumination time in inversely proportional dependence, and darkening time - in direct proportional dependence on the number of pulses at the detector output in the light and dark phases, respectively. The mean value of the detector current is kept constant at a level corresponding to the critical flame detection intensity, which is dictated by the required noise immunity of the system. The time of the illuminated state of the detector is determined by the formula

 SRl8 C20 2f (1)

where E is the amplitude of the pulses at the output of the matching circuit 4;

Ris, € 20 parameters of the integrator charge chain 17;

f is the frequency of the supply voltage.

Since Una, E, Ria, € 20, f are constants, we have

toes n COtlSt OR t0CB l COnSt, (2)

where I is the radiation intensity, determined by the number of pulses о at the output of matching circuit 4 per unit time (cps).

The dark time of the detector is determined by the formula

t; Una-UnHtRi9.C20 ((3)

where Rig, € 20 are the integrator 18 parameters.

Since Une, and ™. E, Rig, Cao - constants, we have the equality

t3 const

The above equality is valid for the case when detector 1 is healthy. It is recommended to choose, 5 tu, where tu is the delay for switching on the relay 15, which determines the permissible inertia of the flame control system.

If the detector 1 generates pulses when the light curtain 10 overlaps, then the darkening time ta due to additional feeding of the integrator 17 through the light-emitting diode 16 pulses from the output of the matching system 4 increases by

value equal to the sum of the durations of these pulses. When the darkening time reaches the value, the relay 15 turns on, signaling that the detector 1 is inoperable.

Thus, the proposed method provides higher reliability of flame control by creating a lightweight mode of operation of the optical detector while maintaining sensitivity. Introducing the inversely proportional dependence of the illumination time toce of the detector on the radiation intensity, moreover, it allows to carry out monitoring of the optical path condition in the nominal load of the aggregates (at the radiation intensity close to the value of the radiation intensity at which the detector reaches saturation). The criterion of the need for routine maintenance to restore the optical path cleanliness is the achievement of the detector illumination time value (the inertia of the flame control system is permissible).

25 Comparative tests confirmed the relatively high reliability of the device implementing the proposed flame control method, namely, the operating time of the IF-1 detector in the proposed mode increased by 3 times without any visible deterioration of the parameters.

Claims (1)

Claim Method A flame control method by converting ultraviolet radiation to 35 electric pulses by overlapping the radiation flux on the detector using an optical shutter and measuring the number of pulses at the detector output with the shutter open and closed, distinguishing; 40 in order to increase reliability by reducing the current load of the detector while maintaining sensitivity, the control time of the detector’s illumination is inversely proportional to 45 dependences, and the time control of the darkening is directly proportional to the number of pulses at the detector output in the light and dark phases, respectively, and the flame signal 50 is formed when the specified number of cycles of radiation flow overlap per unit of time is reached, and the malfunction signal is formed at an overlap duration equal to the value of the permissible inertia of the flame control system.