FR2880328A1 - On-board oxygen generating system operation verifying method for e.g. cargo aircraft, involves deducting information about operation of oxygen generating system from result obtained by controlling one sub-component of system - Google Patents

Abstract

The method involves controlling a sub-component chosen among pressure sensors (5, 6), temperature sensors, oxygen analyzers (17, 18), logic controller (25) managing an oxygen concentrator, inlet and outlet valves and zeolitic adsorbent of an on-board oxygen generating system. Information about operation of the system is deducted from a result obtained by the control. The system is stopped when the controlling and deduction are executed. An independent claim is also included for an on-board oxygen generating system for an aircraft.

Description

The present invention relates to a method for checking or

  control of the proper functioning of an oxygen concentration system

  OBOGS-type aircraft type aircraft, in particular for long-haul or very wide-body airliners with a long radius of action, but also for transport and / or military aircraft, which does not need to make the system work. onboard oxygen concentration to perform this check.

  Currently, the sending of gaseous oxygen to pilots and passengers of a civilian commercial airliner is done in case of decompression of the cabin of the aircraft, whereas its sending only to the pilots is done in the case of protection against smoke and other toxic gases, or prior to a cruise at high altitude.

  In addition, pilots of military weapons planes need a permanent supply of oxygen during their flight missions. The same is true for military tactical transport aircraft and helicopter crews during certain specific missions.

  However, the constraints imposed by the aviation environment lead to the design of the lightest equipment possible and able to provide the largest amount of oxygen possible with significant autonomy, which generates, therefore, a logistics as small as possible.

  In modern fighter planes, the pilot (s) are continuously supplied by an onboard oxygen generation system, commonly called OBOGS (for On-Board Oxygen Generating System), using the technology of separation of air gases by molecular sieves of zeolite type.

  The document EP-A-391607 thus describes an OBOGS-type oxygen concentration system that can be used to feed the crew members of an aircraft employing a molecular sieve adsorbent.

  Other OBOGS type systems are also described by US-A-4,651,728 and EP-A-364283.

  On the other hand, in civil airplanes, the supply of gaseous oxygen to passengers and pilots is usually provided by pressurized oxygen containers, in particular on big-carrier airplanes, or by chemical oxygen generators, in particular particularly on medium-haul aircraft.

  Currently, these civil oxygen production systems are designed and sized to ensure the supply of oxygen passengers, for a period of about 30 minutes, mainly following a loss of pressurization of the cabin.

  However, like the weapons planes, it is now envisaged to equip the new airliners, including the very large wide-area long-range aircraft, as well as business aircraft, embedded systems. OBOGS type adsorbent molecular sieve.

  As such, reference can be made in particular to EP-A-1358911 which proposes using lithium exchanged X zeolites as an adsorbent for OBOGS type system.

  Indeed, a use of a molecular sieve OBOGS type system with respect to oxygen storage in gas containers has the advantage of a saving in mass, when the use times typically exceed 30 minutes, such as this is frequently the case when aircraft are being diverted on new, longer air routes, but also lead to much smaller logistics and unlimited operating autonomy.

  However, an existing problem is recurrently that of the preventive verification of the proper functioning of these OBOGS type oxygen generation systems.

  Indeed, the commissioning of the oxygen concentrator, when the aircraft is on the ground, requires the additional use of an air compressor and possibly a vacuum pump if we want to test the system in a configuration. similar to the usual operating conditions, as well as the connection of this or these machines to the supply and exhaust networks of the waste nitrogen gas of the aircraft and it is therefore necessary to provide, at the output of the OBOGS system, to have a valve whose purge function enables the oxygen production to be ventilated outside the aircraft rather than in the distribution line of the oxygen circuit of the airplane, this purge line being usually connected to the line of exhaust, that is to say nitrogen, the OBOGS system to avoid having to drill several orifices in the fuselage of the aircraft.

  Indeed, in flight, the supply air is taken from the compressed air by the reactor of the aircraft and the nitrogen gas waste is directly discharged outside the aircraft due to the external vacuum prevailing altitude.

  It is immediately understood that applying such a procedure on the ground is not or hardly possible and that, therefore, any preventive verification of the OBOGS system carried out on the ground is costly in terms of time and means to implement and all this more, when it must be done frequently.

  A simple solution would be to check the OBOGS-type oxygen system only when the aircraft is in flight. However, it is easy to understand that this way also has a certain number of disadvantages, or even presents non-negligible risks, in particular since: the control is necessarily a posteriori, that is to say after take-off, and may therefore require a preventive landing, or even an emergency, in case of detection of a malfunction of the OBOGS system, - the operating test consumes power due to a removal of a fraction of the compressed air to reactors, - putting into service creates a noise nuisance for passengers, and - it adds an additional task to the crew in an already busy phase.

  The problem that arises in this context is therefore to propose a simple method to implement, especially on the ground, and for the verification and control of the proper functioning of an OBOGS type aircraft oxygen concentration system for aircraft , in particular for long-range airliners or very large long-range airliners, but also for transport and / or military aircraft, which does not require operating the onboard oxygen concentration system to perform this verification, so as to reduce the frequency of checks carried out in flight, or even to delete them if the period between two checks is a few months and makes possible the use of machines outside the aircraft, such as air compressor or vacuum pumps.

  The solution of the invention is then a method for verifying the operation of an OBOGS type oxygen production system embarked on an aircraft using at least the following sub-elements: an oxygen concentrator containing at least an adsorbent for producing oxygen from air by preferential adsorption of nitrogen on said adsorbent, a calculator managing the oxygen concentrator, a pressure and / or temperature sensor connected to the computer, an oxygen analyzer, and - one or more valves arranged upstream, that is to say on the input side, and / or downstream, that is to say on the side of the outlet, of the oxygen concentrator, characterized in that: a) at least one control of at least one of said sub-elements selected from the pressure and / or temperature sensor, the oxygen analyzer, the calculator managing the concentrator, the valve and the adsorbent, and b) one deduces from the result was obtained in step a), an operating information of the OBOGS-type onboard oxygen production system.

  Depending on the case, the method of the invention may comprise one or more of the following characteristics: the operating control of the pressure and / or temperature sensor comprises the steps of: i) detecting a given signal delivered by the sensor to be tested, ii) comparing the value of the delivered signal with an expected or desired value, and ii) inferring from the comparison of step ii) an operating state of said sensor.

  the operation control of the oxygen analyzer comprises the steps of: measuring an oxygen content value by means of the analyzer in a gas or gas mixture containing a known oxygen content, ii ') compare the oxygen content value measured in step i ') with the expected oxygen content value, and iii') deduce from the comparison of step ii ') an operating state of the analyzer.

  steps a) and b) are implemented when the OBOGS system is stopped.

  in step a), a number of OBOGS sub-elements selected from the pressure and / or temperature sensor, the oxygen analyzer, the calculator managing the concentrator, the valve and adsorbent.

  - the operation check is carried out when the aircraft is in flight or placed on the ground, preferably when it is placed on the ground.

  - the functional verification is carried out periodically or continuously.

  the valve or valves are electrically powered valves.

  the operation of the adsorber is controlled by controlling the moisture content of the adsorbent, preferably by means of a humidity sensor or a hygrometer.

  the adsorbent is a zeolite, preferably an X-type zeolite. The invention also relates to a system for verifying the operation of an aircraft oxygen generating equipment (OBOGS) using at least one concentrator oxygen composition containing at least one adsorbent for producing oxygen from air by preferential adsorption of nitrogen on said adsorbent, comprising at least: first means for controlling at least one pressure sensor and / or temperature, - second control means of the oxygen analyzer, - third control means of the calculator managing the concentrator, - fourth control means of at least one valve, and / or - fifth means controlling the adsorbent.

  More specifically, the analysis of the causes of failure of an OBOGS type system has led the inventors of the present invention to select five points to be subject to a particular control and this, taking into account the particular characteristics of this type of units on board, namely that the vacuum is physical at altitude and that the compressed air is not supplied by a dedicated machine but by the compressed air network within the reactors.

  More precisely, the five points to be checked according to the invention are: - the pressure sensor (s) and / or temperature sensor (s). Indeed, these sensors placed upstream of the concentrator serve to verify the conditions of compressed air received by the system.

  - the oxygen analyzer. This sensor placed downstream of the concentrator serves to verify the good oxygen enrichment of the gas produced by the OBOGS system.

  the computer managing the concentrator and the other electromechanical devices, the valve or valves including the distributors of each concentrator and the outlet purge and regulation valve of the system, and the state of the adsorbent, more particularly the the zeolite adsorb 20 preferably nitrogen from the air to produce a flow rich in gaseous oxygen.

  All of these components are shown in Figure 1 which is a block diagram of an OBOGS system according to the invention.

  FIG. 1 shows an OBOGS system according to the invention comprising an inlet 1 of compressed air, for example air coming from the engines, the temperature of which is measured by the redundant temperature sensors 2 and 3 and feeding a inlet valve 4. This inlet valve 4 is of three-position type: regulating, closed and drain. In the regulation position, the pressure regulated by the redundant pressure sensors 5 and 6 is measured.

  The air is then directed through an inlet filter 7 before being distributed, via a set of distribution valves 8 and elution valves 9, into one or the other of the two adsorbers 50, which operate alternately, that is to say that one is in the adsorption phase, while the other is in the regeneration phase.

  At the outlet of the adsorbers 50, the oxygen-enriched gas passes through the non-return valves 12, 13 and the outlet filter 14.

  The outlet gas pressure is measured by redundant sensors 15, 16 and the concentration of the gas by redundant analyzers 17, 18. Part of the oxygen enriched air can also be sent to the cabin 20 via a conveyor line appropriate.

  The outlet valve 19 distributes the gas to the masks 30 or venting it through an appropriate exhaust line 21.

  Monitoring and control of the system is done through a calculator 25 managing the oxygen concentrator.

  The calculator also makes it possible to relay the information relating to the OBOGS, such as performances, failures, etc., to other higher-level computers of the aircraft, such as the maintenance, air supply, maintenance computers. display in cabin etc ...

  Figure 2 illustrates, more precisely, the flow of air in adsorbers 50 of Figure 1, each of which contains a zeolitic adsorbent bed 51.

  The inlet side compressed air is dispensed through (arrow direction) an open rib bottom 52 before passing through the bed 51 of zeolite particles.

  At the adsorber head, the oxygen-enriched air is collected at the dead volume 53 of each adsorber 50 and in the central tube 54, which is also used for the overall mechanical strength of the adsorbers 50.

  In other words, the inventors of the invention have realized that the overall control of good operation of the OBOGS type of onboard oxygen production system, that is to say the measurement of quality and quantity of oxygen produced, can be advantageously replaced by a verification of the various points mentioned above, thus ensuring the degree of reliability required for this equipment.

  The actual tests of the oxygen concentrator can therefore take place with a reduced frequency making possible a ground control using additional machines or a non-systematic flight test and programmed on particular flights, for example.

  The invention therefore relates to the procedure of the checks carried out preferably on the ground and on equipment modified or added to the conventional device of the OBOGS type to enable these verifications.

  As explained, the principle of these checks is that they can be made while the onboard oxygen concentrator, that is to say the OBOGS system, is not in operation, preferably when the aircraft is on the ground , but could at least partly be also done during a flight according to the selected control policy.

  Some of the checks to be carried out can be done continuously or only for periods.

  Thus, it is possible for example to let the pressure sensors, temperature and oxygen content analysis probe in service, and to automatically check, continuously or periodically, if the indications issued by these devices are those expected .

  In the same way, it is possible to operate the valves or distributors and to check the positions taken by these organs while the aircraft is in flight. It will be noted that then the adsorbers could be depressurized and possibly re-pressurized although there is generally, upstream, one or more valves for sectioning the compressed air which would then remain closed, because of the external vacuum and the network of air, without the normal oxygen production cycle being started.

  This type of static flight check can also complete or complete a procedure previously performed on the ground. It then makes it possible to test the equipment forming part of the control protocol under different conditions, for example maneuvering the valves with a differential pressure, a sub-atmospheric pressure or under other conditions.

  This test procedure can of course be part of a more complete procedure including, for example at a given time interval of a few months, an oxygen production test with purity and flow measurement carried out on the ground with the appropriate equipment or in flight. The various control tests to be performed in the context of the invention will be detailed below.

  Functional test of the pressure and temperature sensors The operating test of the pressure sensor (s) 5, 6, 15, 16 and of temperature 2, 3 consists of detecting a given signal of pressure or, as the case may be, of temperature, when put into service on the ground, that is to say when the circuit is uncut, and to compare the received indication with an expected value of pressure or, as the case may be, of temperature, for example the ambient temperature and the ambient atmospheric pressure at the place where the verification is carried out and / or with the value of other probes having the same function.

  Maximum deviation criteria make it possible to deduce whether the information is ready to operate or not.

  Functional test of the oxygen analyzer The proper functioning of (or) the oxygen analyzer 17, 18 can likewise be detected with respect to the oxygen content of the air and , if necessary, by injecting at the zirconia probe of the analyzer 17, 18 a given amount of pure oxygen or known content, from a capacity under pressure.

  Again, criteria of maximum deviation, response time, ... indicate the ready to operate or not.

  ECU Function Test The ECU 25 can be operated by running an internal self-test program generating a ready-to-run signal if all tests are positive. Typically, the following features of the computer are verified: inputs / outputs, watchdog system, CPU and memory.

  Functional test of the valves The verification of the proper functioning of the or each valve 4, 19 requires the replacement of the usual pneumatic devices by control valves and electrically powered gas flow distributors.

  Thus, the valves can be operated without requiring minimum instrument air pressure unavailable until the reactors are in a sufficient operating regime.

  Position transmitters then make it possible to check whether the opening / closing / positioning of the valves is in accordance with an expected opening / closing scheme.

  Functional test of the adsorber Once the geometric dimensions of each adsorber 50 are adapted to the physical characteristics of the adsorbent and the valves selected, a pressure and temperature control makes it possible to ensure that the flows involved are consistent with the flow rates. desired and thus avoid any risk of moving the adsorbent.

  It is also desirable to control the pollution of the zeolite of the adsorbent 51 with water generally from atmospheric moisture. The effects and causes of this pollution in the case of large industrial unit are described in EP-A1095689.

  The verification of the good state of the adsorbent can therefore relate to a verification of the absence of water in the adsorption zone where the zeolite intended for the nitrogen / oxygen separation of the air is located.

  The detection of a zeolite polluted by water can be carried out by taking advantage of the modification of one or more intrinsic properties of the material. Among the properties modified by the presence of water, there is the electrical conductivity which is a function of the voltage and frequency of alternating current; the dielectric permittivity which is a function of the AC frequency; the density; the rate of propagation of sound that is a function of frequency; and the magnetic properties that are a function of frequency.

  As an illustration, it is known that the zeolite consists of a crystalline lattice comprising a negatively charged alumino-silicate microporous framework in which are located most often metallic cations whose position in the crystallographic sites is not absolutely rigid. As a result, the zeolite is sensitive to the presence of an electric field which causes a polarization or induces an electric current by transporting the cations. The water molecules have a very strong molecular electric dipole (dielectric constant of the liquid water of the order of 80) and, moreover, they strongly interact with the cations of the zeolite.

  It accordingly appears that the electrical properties can be modified by the presence of water molecules both by their specific properties and by their influence on the cations.

  Of course, as in any phenomenon of forced movement of particles subjected to a restoring force, the frequency has a preponderant role in the intensity of the response to the applied alternating field.

  It can also be noted that the presence of water increases the zeolite at the same time as it changes its mechanical properties by modifying the interaction between the charges of the framework and the cations, which changes for example the Young's modulus and the phonon frequency of the crystal.

  As a result, it is expected that the speed of propagation of the modified sound, most often diminished, will be seen for both transverse and longitudinal vibrations. In the same way as for electrical phenomena, the frequency of the applied sound must be taken into account.

  We can also mention the detection of water molecules by their signal in nuclear magnetic resonance (NMR), which can lead to distinguish water molecules in different positions in the zeolite crystal.

  The localization of the water pollution can be done by local probe measuring the water located in its vicinity or by triangulation between different detectors measuring the property of the material located between them, and by reconstructing the properties of the material by mathematical treatment of the responses of the set of detectors. The triangulation can be done by plane cutting or on the whole volume, the choice of the method being dictated by the number of probes, their sensitivity and the available mathematical processing capacity.

  A method for real-time monitoring of the water pollution of a bed of zeolite and in-situ rapid measurement of water is described in document FR 0304546, which consists in installing electrodes in the volume of water. adsorbent and measure the resistance thereof continuously. The knowledge of the resistance graph between the electrodes makes it possible to locate the areas where water pollution occurs.

  A similar device is described in US-A-6,593,747 where the resistance measurement applies to either a portion of the adsorbent bed or to a single adsorbent bead, which in this case is taken as a control of the global state.

  In general, all the characteristics of the signals can be used, attenuation or phase shift, depending on the frequency.

  The probes may be of any shape, linear, annular, cylindrical, they may be placed in alignment, in a circle, in polygons, in polyhedra or even arranged randomly.

  It is possible to use a part of the adsorber made of metal to form at least one of said probes, another part of the adsorber then being made of a non-conductive material serving as an insulator.

  To increase the sensitivity of the probes present in the solid phase, it is possible to associate a local heating capable of desorbing all or part of the water present in the zeolite and thus make it accessible to the detectors.

  Another way of highlighting water pollution is to place detectors in the gaseous phase upstream or downstream of the zeolite, provided that they are sensitive to the residual pressure of water vapor in the phase. gas.

  For example, hygrometers can be placed in the zeolite or at both ends of the bed. Among the most efficient hygrometers are those with capacitive measurement, or those with cooled mirror, or with P2O5. The probe can be used as an indicator and integrator of pollution over a period of time.

  The development of micro-sensors based on impurity-sensitive polymers, such as water in the present case, can also be used to fulfill this detection function. In addition, these micro-sensors can be equipped with miniaturized electronic systems allowing remote communication without wire connection thus simplifying the transfer of information.

  Another method is to place detectors on possible paths of water pollution, for example near valves or gaskets. In this case, the hygrometers can be used, possibly associated with bodies particularly eager for water that can in addition serve as a water trap. It is then possible to practice a preventive action if one arranges so that almost all the water is stopped in this trap at the moment when the detection by hygrometers becomes positive.

  The methods described may be applied in such a way as to lead to a quantitative measurement of water pollution, for example to obtain the distribution of the water content of the zeolite in the total volume, or to an evaluation of the total quantity of water. water present.

  It can also give rise to an 'all or nothing' result which leads to alarming the presence of water in the zeolite, for example by detecting the presence of water at strategic points of the system.

Claims (10)

  1. A method for verifying the operation of an OBOGS oxygen production system embarked on an aircraft using at least the following sub-elements: an oxygen concentrator (50, 51, 52, 53, 54 ) containing at least one adsorbent (51) for producing oxygen from air by preferential adsorption of nitrogen on said adsorbent (51), - a calculator (25) managing the oxygen concentrator (50, 51, 52, 53, 54), - a pressure sensor (5, 6; 15, 16) and / or temperature sensor (2, 3) connected to the computer, - an oxygen analyzer (17, 18), and one or more valves (4, 19) arranged upstream and / or downstream of the oxygen concentrator (50, 51, 52, 53, 54), characterized in that: a) at least one control of at least one of said sub-elements selected from the pressure sensor (5, 6; 15, 16) and / or temperature sensor (2, 3), the oxygen analyzer (17, 18), the computer (25) managing the concentrator, the valve (4, 19) e t the adsorbent (51), and b) is deduced from the result obtained in step a), an operating information of the OBOGS-type onboard oxygen production system.   2. Method according to claim 1, characterized in that the operating control of the pressure and / or temperature sensor comprises the steps of: i) detecting a given signal delivered by the sensor to be monitored, ii) comparing the value of the signal delivered with an expected or desired value, and ii) derive from the comparison of step ii) an operating state of said sensor.   3. Method according to claim 1, characterized in that the operating control of the oxygen analyzer comprises the steps of: i ') measuring an oxygen content value by means of the analyzer in a gas or gas mixture containing a known oxygen content, ii ') comparing the oxygen content value measured in step i') with the expected oxygen content value, and iii ') inferring from the comparison of step ii') an operating state of the analyzer.   4. Method according to claim 1, characterized in that steps a) and b) are implemented when the OBOGS system is stopped.   5. Method according to claim 1, characterized in that in step a), a plurality of the OBOGS system sub-elements selected from the pressure and / or temperature sensor, the analyzer of oxygen, the calculator managing the concentrator, the valve and the adsorbent.   6. Method according to claim 1, characterized in that the functional verification is performed when the aircraft is in flight or placed on the ground, preferably when it is placed on the ground.   7. Method according to claim 1, characterized in that the functional verification is carried out periodically or continuously.   Method according to Claim 1, characterized in that the valves are electrically powered valves.   9. Method according to claim 1, characterized in that the operating control of the adsorber is done by controlling the moisture content of the adsorbent, preferably by means of a humidity sensor or a hygrometer .   10. Process according to Claim 1, characterized in that the adsorbent is a zeolite, preferably an X-type zeolite. 11. System for verifying the operation of an on-board oxygen production equipment (OBOGS) for an aircraft putting into effect at least one oxygen concentrator containing at least one adsorbent for producing oxygen from air by preferential adsorption of nitrogen on said adsorbent, comprising at least: first control means of at least one at least one pressure and / or temperature sensor; second means for controlling the oxygen analyzer; third control means for the computer managing the concentrator; fourth control means for at least one valve; and / or fifth means for controlling the adsorbent.