RU2711186C1 - Method of signaling presence of combustion in augmenter of air-jet engine - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measurement equipment, and can be used, for example, to signal the presence of combustion in afterburner combustion chamber of an air-jet engine. Method of signaling presence of combustion in augmenter combustion chamber of an air-jet engine, which includes registration of radiation from the combustion zone, processing of the received signal and making a decision on presence of combustion. Generated during registration of radiation during engine operation common electric signal is divided into broadband in frequency range 0–5,000 Hz and narrowband, wherein the narrow-band frequency range is selected based on the acoustic and geometric characteristics of the afterburner combustion chamber, selecting in these intervals the average values of signal amplitude amplitudes and comparing them with the reference values obtained before the engine operation for each interval, in case of simultaneous excess of signal oscillation amplitudes above reference values in both frequency ranges conclusion is made on presence of combustion in afterburner.EFFECT: higher reliability of control over afterburner combustion process.1 cl, 1 dwg

Description

The invention relates to measuring equipment and heat engineering, and can be used, for example, to signal the presence of combustion in an afterburner combustion chamber (FCC) of an air-jet engine (WFD).

When creating and operating the combustion chambers (CS) of aircraft engines, it is necessary to control the presence of combustion in them to ensure the safety of their work with automatic ignition control systems. Widely used electro-ionization sensors located in the zone of combustion stabilizers fundamentally have the locality of diagnosing combustion zones around the electrode of the sensitive probe.

In modern annular KS, which can operate in modes with lean combustible fuel-air mixtures, the flame can drift in the working area of the stabilizers and go beyond the scope of the probe, which leads to instability of the automation of the fuel supply and ignition systems of the KS and false signals about the extinguishment of the KS.

Attempts to apply optical methods as a signaling device for combustion in a compressor station have been undertaken for a long time. From SU 523554, 1973, a differential method is known for recording the thermal radiation of combustion products (without limiting the spectral range), before and behind combustion stabilizers. However, with modern high-enthalpy modes of operation of the main CS and the use of small modes in afterburner CS, the differences in the recorded integral radiation are insignificant and the reliability of this method is insufficient.

A flame detector is known according to patent EP 0157644, 1985, which uses a photodetector based on a GaAsP heterostructure with sensitivity to ultraviolet radiation in order to reduce the influence of infrared radiation.

Such a detector well perceives the above radiation characterizing the combustion zone. However, the specifics of the FCC operation in flight suggests the possibility of the rays of the sun entering the jet nozzle. In this case, the flame sensor will give a false signal about the presence of combustion in the COP.

The closest analogue of the proposed invention is known from US 4029966, 1977, a method for detecting a flame in the FCC engine, including the registration of radiation from the combustion zone, processing the received signal and deciding on the presence of combustion. To register radiation, a sensor is used based on a gas-discharge photocell, the sensitivity spectrum of which lies in the range 180 ... 300 nm. However, the processes characterizing combustion are accompanied by local radiation of OH radicals (308-320 nm), CH (431-438 nm), C ₂ (467-470 nm; 513-516 nm) during chemiluminescence in chemical reactions of hydrocarbon fuel oxidation. Therefore, the sensitivity of the device for detecting combustion in the known method is low. Another disadvantage of the known method is the low information reliability, since during the flight of the aircraft the rays of the sun may enter the jet nozzle, while the flame sensor can give a false signal about the presence of combustion in the COP.

The aim of the invention is to increase the reliability of control over the process of starting the FCC.

This goal is achieved by the fact that in the known method of signaling the presence of combustion in the afterburner of the combustion engine of an aircraft-jet engine, including registering radiation from the combustion zone, processing the received signal and signaling the presence of combustion, according to the proposal, the total electric received when registering radiation during engine operation the signal is divided into broadband, in the frequency range 0-5000 Hz and narrowband, while the narrowband frequency range is selected based on acoustic and geometric characteristics of the afterburner, select the average values of the amplitudes of the oscillations of the signal in these intervals and compare them with the reference values obtained before starting the engine for each interval, if the amplitudes of the oscillations of the signal exceed the benchmarks in both frequency ranges, we conclude that there is burning in the afterburner the camera.

During combustion in the CS, due to the turbulence of the gas flow, there are pressure pulsations and corresponding pulsations of the luminosity of the combustion products associated with acoustic vibrations in the CS. These pulsations can serve as an additional diagnostic criterion for the combustion process in the FCC, which is not affected by the influence of solar radiation on the operation of the combustion signaling device.

The specificity of the radiation perceived by the sensor lies in the fact that at maximum, after-engine operating modes of the engine, in the gas stream in the FCC, local formations of dying fuel components from the main CS can be contained, giving some small, pulsating component in the narrow-band information processing channel. At the same level, the pulsation component can also appear during maximum combustion in the PCF due to the fact that the optical density of the medium increases and the gas flow becomes almost opaque throughout the volume. The total radiation energy from the FCC volume is significantly larger than the pulsation (in the resonance region) component, which is received from the small, in thickness, relatively transparent peripheral region of the combustion volume, close to the window of the receiving sensor.

Experimental studies of the power density spectrum of an electric signal from a pressure sensor and an optical radiation detector installed on the FCC showed that at a level of 20 dB the total energy of the signal is in the range up to 5 kHz, which determines the choice of a broadband frequency range of 0-5000 Hz.

The choice of a specific narrow-band channel filtering range is assigned based on bench studies of an engine with a specific FCC in all boost modes. For example, the characteristic value of the range for modern FCC is 500-700 Hz. The average values of the electric signal for each channel are also determined for all boosting modes, and the minimum values with the corresponding safety factor are selected as reference values.

The oscillation amplitudes in the narrow-band and wide-band intervals vary greatly, therefore, the averaged oscillation values of each interval are compared with the reference values obtained experimentally for each engine type in tests. The presence of simultaneous excess in both intervals gives a guaranteed indicator of the presence of combustion in the FCC, because in the narrow-band interval, the signal in the FCC may be false due to the influence of the main combustion chamber with its gas flow pressure fluctuations, and in the wide-band interval the false signal may appear due to another source of short-wave radiation, incl. sunshine.

The drawing shows a variant of the structure of the device that implements the claimed method, where:

1 - combustion chamber;

2 - stabilizers;

3 - combustion zone;

4 - fiber light guide;

5 - photodiode;

6 - transimedance amplifier;

7 - band-pass filter;

8 - amplitude detector;

9 - reference unit of reference levels;

10 and 11 are comparators;

12 - logical cell "AND";

13 - binary output of the signaling device.

In the combustion chamber 1, behind the stabilizers 2, a combustion zone 3 is located, to which the input end of the fiber 4 is oriented, the output end of the fiber 4 is optically coupled to the photodiode 5. The photocurrent of the latter is converted to voltage by a transimpedance amplifier 6, the signal from which is fed to the comparator of the complete information signal 11 and on a narrow-band pass filter 7, where the pulsating component of the signal is proportional to and amplified, proportional to the radiation from the combustion zone. Further, this signal is detected by the node 8, the voltage from which is compared by the second comparator 10 with a predetermined level set on the setter 9.

Claims (1)

A method for signaling the presence of combustion in an afterburner of a combustion engine of an aircraft-jet engine, including registering radiation from the combustion zone, processing the received signal and signaling about the presence of combustion, characterized in that the common electrical signal obtained when registering radiation during engine operation is divided into broadband in the frequency range 0-5000 Hz and narrowband, while the narrowband frequency range is selected based on the acoustic and geometric characteristics of the afterburner, I highlight in these intervals, the average values of the amplitudes of the oscillations of the signal and compare them with the reference values obtained before starting the engine for each interval, in the case of simultaneous excess of the amplitudes of the oscillations of the signal over the reference values in both frequency ranges, it is concluded that there is burning in the afterburner.

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