DEVICE AND DETECTOR RECEIVING SET OF RADIATIONS COMPRISING A FILTER

The present invention relates to the radiation detector of the type in which a sensor receives radiation through a filter.

Have previously been described type radiation detectors for controlling the combustion in a gas turbine engine, and more particularly to the control of the flame holding in the engine. It has proposed such detectors for such engines used on an aircraft in which a warning or other response is to be transmitted when the flame is extinguished so that the motor can be ignited again and that the power can be restored, without undesirable delay. However, the sensor response tends generally to be disturbed by the thermal radiation received from the engine. Furthermore, during the test of a flame, the detector must be substantially insensitive to radiation of the incandescent portions of the engine so that it takes a rapid response to the conditions created when extinguishing the flame. It has been found that these problems could be solved in large part by use of a filter removing the infrared component of the radiation received by the sensor. However, the infrared filters normal that allow the transmission of ultraviolet radiation to the sensor have not been satisfactory at high temperatures implemented by the motors.

A radiation detection apparatus of the aforementioned type which can be used to control the flame in a turbine engine.

More specifically, the invention relates to a radiation detection apparatus of the aforementioned type, comprising a filter formed by a thin film of gold that attenuates the infrared component larger than the UV component of the transmitted radiation to the sensor.

The thickness of the gold film is generally between 10 & s and 200. The film eSbépais More and more 1' atténuatien of the infrared component is large, but the UV component is also reduced so that the choice of the thickness of the film depends on a compromise between the desired sensitivity for the infrared detector and the intensity of the infrared radiation that can be tolerated.

The filter formed by the gold film can be carried by a sapphire window. The window may be planar but it may also be in the form of a lens.

The invention also relates to a radiation detection apparatus wherein a radiation detector device is interrogated repeatedly so that in that a level of radiation corresponding to a predetermined condition is detected is determined, a warning device or other being controlled in the case where the condition no longer exists. It may also have utility in the context indicated previously from the combustion control in a gas turbine engine, the sensor device being interrogated repeatedly to enable the transmission of a warning or taking a measurement compensation, rapidly whenever the flame goes out.

However, known apparatus provided therefor transmit a warning or trigger a compensating action unnecessarily after very short interruptions of the response of the device ' detector, which may be in practice. A radiation detection apparatus can be used and suppresses or at least reduces such disturbing operations.

More specifically, the invention relates to an apparatus for detection of radiation in which a radiation detector device is interrogated repeatedly so that in that a level of radiation corresponding to a predetermined condition is detected is determined, killed warning device or other being controlled in the case where the condition no longer exists; the apparatus is characterized in that it comprises a counter, Registry in that the warning device or other operates when a predetermined number is exceeded in the counter, in that the number of the counter progresses to the indicated value in each successive poll the sensor device, and that the counter is reset to zero whenever the existence of the predetermined condition is notified by the response of the sensor device during a query.

Therefore, in the case of such an apparatus, the operation of the warning device or other takes place ςμ' after the meaning by the detector device absence of the condition for a predetermined number of successive interrogations. The suitable choice of this number makes it possible to suppress operations undesirable and preserves but the positive and rapid operation which would otherwise be required.

The predetermined condition detected may be the absence of radiation so that the warning device or other is to operate when radiation are detected. On the other hand, in the context of the detection of a flame, as described above, that condition can be the presence of a suitable flame in the area of combustion.

Other features and advantages of a radiation detection apparatus and an apparatus comprising such a device, " for the detection of a flame in a gas turbine engine for aircraft, shall become apparent better still from the description which will follow, made with reference to the accompanying drawings on which ':

-figure 1 represents an apparatus comprising a sensor device, mounted on a gas turbine engine; and

figure 2-is a longitudinal section of the radiation detection apparatus.

Although the flame detecting apparatus described in the following the present memory may be used for the detection of extinction of the flame of the main combustion zone of a gas turbine engine, it is also suitable for the same function in the case of the flame of a device for the post-combustion of the engine. It is in the latter context the apparatus is shown and described in the following. On Figure 1, the post-combustion device which is mounted between the turbine and the propulsion nozzle of the engine, includes a housing 1 surrounding the ring 2 fuel delivery (the engine can present more rings) and the exhaust cone 3 of the engine. The housing 1 is connected by an annular support 4 to the nozzle 5 and the tube 6 of flame of the afterburner.

The post-combustion device is operated with a increased thrust is required, by pumping fuel in the ring 2. A device 7 of flame holding downstream of the ring 2, creates turbulence for tin good mixing the fuel with the hot exhaust gases normally flowing on the cone 3, from the combustion chamber of the engine. The combustion of the mixture surrounds the device 7 of a flame and it is the existence of the flame to be checked in one embodiment. Control is performed with tin sensor 8 screwed into a mounting block 9 carried by the support 4 and which is directed in a way that it may view the device 7 and receives the radiation of the combustion zone of the afterburner.

It is necessary that the detector 8 to distinguish between the radiation of the flame and incandescent metal elements of the engine and that it is not affected by the solar radiation that may flow through the nozzle 5" so that the detector 8 can respond quickly and positively to extinction of the flame afterburner. Satisfying of these criteria is performed using a detector 8 which is especially sensitive to the ultraviolet radiation component that it receives and which is directed in a way that the tube 6 and 7 the device prevents the passage of solar radiation through the nozzle 5. The details of construction of the detector are shown in Figure 2.

On Figure 2, the radiation sensor of the detector 8 is a gas discharge tube 10 elastically mounted in a silicone rubber element 11, in a stainless steel casing 12. The radiation penetrate the pipe 10 by the upper part of the glass envelope 13, from within a tubular nose 14 titanium which is brazed to the shell 12. A window 15 in the form of a plano-convex lens in sapphire is brazed to the front end of the nose 14 and seals the device and thus protects the tube 10 from the exhaust gas of the autrès and combustion products of the engine.

The window 15 can support the high temperature prevailing in the post combustion zone and is highly transparent to ultraviolet radiation. However, radiation received are filtered by a gold film 16 which coats the planar back face of the window 15. The film 16 having a thickness of about 100 %, attenuates relatively little ultraviolet radiation transmitted, but reflects the radiationsinfrarouges much so that it is essentially an ultraviolet component of the radiation received which is transmitted to the tube 10.

The arrangement of the attenuating filter the infrared radiation transmitted to the tube 10, in fact the reduced Heating undergone by the tube 10 subjected to the radiation of the flame. The tube 10 has a maximum working temperature of 300 °C for example, and the filter allows the arrangement of the tube closer to the post-combustion zone so that the field of view of this area is greater than, with respect to the case where the temperature is not so limited. The field of view is further enlarged in the present case for the window 15 by use of a plano-convex lens; the window 15 can however be as flat.

The sensitivity of the detector 8 to the radiation transmitted by the window 15 is coated with gold from the post-combustion zone, is increased by a reflective coating 17 formed on the inner face of the nose 14, so that as much as possible of the radiation reaches the curved top portion of the glass envelope 13. Specifically, ion reflective coating 18 which is silver or aluminium as

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the coating 17 and which has a thickness of 10,000 A, is for-

meq to the outside of the shell 13, except in the curved top portion. The coating 18 is such that the ultraviolet radiation which penetrate the pipe 10 with any inclination reach, optionally after multiple reflections in the shell 13, in the discharge space between two electrodes 19 of the tube 10.

The electrodes 19 extend out of the encasement 13 of the tube 10 and are soldered to wires 20 which are wound and rubber coated for supporting the shock and vibration forces. The external electrical connection wires 20 supplying the electrodes 19 is provided by a bayonet base 21 which is welded on the shell 12 of the detector. As shown in Figure 1, the energization of the electrodes 19 is provided by a rectangular wave generator 22 £through mth frequency of 400 Hz) which is connected to the cap 21.

The amplitude of the voltage of the rectangular waveform applied between the electrodes 19 of the tube 10 by the generator 22 is not sufficient by itself to initiating the discharge.

It occurs in a applied pulse of the waveform that when the ultraviolet radiation received in the tube 10 are sufficient for producing a minimum ionization préliminairedu gas between the electrodes 19.

That ionisation is created only when the flame is present at the maintenance device 7.

The pulses synchronized to the excitation pulses transmitted between the electrodes 19 by the generator 22, is transmitted by a potentiometer 23 to a counter 25 through a transistor 24. The counter 25 counts pulses but is reset to 'zero each time that' me discharge appears in the vessel 10. To this end, m operational amplifier 26 compares the potential of one of the electrodes 19 of the tube to m potential established by me stabilized voltage source 27, so that the variation of the electrode potential due to the creation of discharge causes me ' me reset pulse for the counter 25. The-potential change is due to the discharge current to flow and reduces the voltage between the electrodes 19 through mth amount less than that which is necessary in order the maintenance of the discharge. Therefore, each time that 'me flame exists at the maintenance 7 and transmits ultraviolet radiation which are suitable for the setting' me minimum preliminary ionization in the tube 10, the discharge between the electrodes 19 is performed but only transiently, to each successive pulse transmitted by the generator 22. The counter. 25 is therefore reset repeatedly to each transmitted pulse by the transistor 24.

In the case where the flame goes out or when the discharge in the tube 10 is interrupted further, the counter 25 is not reset so that the number that it contains progresses to each pulse of the generator 22.

When the interrupt is transient and of very short duration, so that a discharge appears in the vessel 10 before the maximum number (e.g. 8) is exceeded in the counter 25, 1 *' pulse transmitted by the amplifier 26 resets the counter 25 to zero once more. However, when the number is exceeded, the overflow of the counter 25 triggers the conduction of a transistor 28 that controls a relay 29. The contacts 30 of the relay 29 are thus closed and indicates in that the flame has gone out to a command 31. This can simply alerting the pilot of the aircraft of the sensed condition, but may also, in addition to, or further, trigger an automatic action, for example the reignition of the post-combustion device.

The in that the relay 29 is energized only when the tube 10 has no discharge following a number of successive cycles of the waveform exciter is advantageous because it avoids the harmful operating of the control 31. Though the number indicated previously is 8, it may be desirable and quite acceptable that it is carried for example 16.

A semiconductor sensor can replace the discharge tube 10 and, in this case, a tubular guide can be used so that it directs the ultraviolet radiation to the sensitive area of the detector. A glass tube having a reflective coating that ultraviolet rays, its outer face, or a metal tube having a reflective coating to the inner face, is suitable for the formation of the guide.

Another of guide is the use of a solid slug of material transmitting ultraviolet rays (for example sapphire) having a reflective coating to the outside.

It is well understood that the invention has been described and illustrated as a preferred example and that can be provide equivalence technique in its constituent elements without departing from its frame, which is defined in the appended claims.