Aeronautics and astronautics – Aircraft structure – Ice prevention
Reexamination Certificate
1998-11-12
2001-06-05
Poon, Peter M. (Department: 3643)
Aeronautics and astronautics
Aircraft structure
Ice prevention
Reexamination Certificate
active
06241189
ABSTRACT:
The present invention relates to the deicing of air inlet cowls of jet engines, particularly aircraft engines.
It is known that, if need be (to prevent the formation of ice or remove ice that has already formed), the leading edge of the air inlet cowl of such engines is deiced by heating with pressurized hot air tapped from said engine and conveyed to said leading edge by a hot air circulation circuit.
To this end, such an air inlet cowl comprises:
a hollow leading edge delimiting an internal peripheral chamber closed by a first internal partition (or frame) and equipped with at least one orifice placing said internal chamber in communication with the outside; and
a pipe which can be connected, at its rear end away from said leading edge and passing through a second internal partition, to said pressurized hot air circulation circuit and, at its front end toward the leading edge, to an injector injecting said pressurized hot air into said internal chamber.
The pressurized hot air tapped from the engine is at a high temperature, for example of the order of 400° C., which means that said pipe radiates heat and that the nearby structures in said air inlet cowl which are sensitive to heat (for example the acoustic panels which are made of a composite material) need to be protected against the heat. Furthermore, for obvious safety reasons, it is also necessary to provide some protection for said nearby structures, in case pressurized hot air should leak or said pipe should burst.
In the current state of the art, there are essentially three known methods for protecting said structures near to the pipe that conveys the hot air for deicing. These are:
first of all, protection by spraying a coating of thermally-insulating foam or paint onto said temperature-sensitive structures. Such protection is, of course, restricted to the surfaces coated. For this reason, the thermally-insulating coating needs to be sprayed either over all of the components inside the air inlet cowl, which increases their mass and has the risk of making inspections and repairs difficult, or onto just that part of said components which are in the immediate vicinity of said pipe, the consequence of this being that the unprotected components do not age well under the effect of the heat and often need repair. Furthermore, given the limited life of such thermally-insulating coatings, the protection they afford is only temporary and frequent periodic inspections, which are difficult to conduct because of the poor accessibility to the inside of said air inlet cowl, have to be performed. Finally, for safety reasons, it is necessary to provide in said cowl a device for detecting the bursting of the pipe, such as a vent door, this device having to be specially attached to the deicing cowl;
or, a double-wall protection. However, given the complications involved in producing double walls around pipe connections, such protection is often limited to the pipes themselves. This then results in a thermal protection which is either very partial, or complicated, costly and cumbersome. However, even if the connections are produced as double-walled connections, heat is still radiated toward the sensitive structures, because no heat energy is taken away. Finally, here too, safety requires there to be a device for specially detecting that the pipe has burst;
or, alternatively, as described in document EP-A-0 205 283, a protection using an enclosing metal structure which also serves to remove the deicing air leaving the peripheral chamber inside the leading edge. However, the temperature, which is still high (about 200° C.) of the deicing air leaving the leading edge, causes excessive radiation of the heat from the enclosing metal structure to said nearby structures. Furthermore, a device for detecting that said pipe has burst is very difficult if not impossible to install, even though it is essential to safety, because of the shape and design of such a protection.
The object of the present invention is to overcome these drawbacks.
To this end, according to the invention, the air inlet cowl for a jet engine especially for an aircraft, said air inlet cowl being equipped with means for deicing its leading edge and comprising, for this purpose:
a hollow leading edge delimiting an internal peripheral chamber closed by a first internal partition and equipped with at least one orifice placing said internal chamber in communication with the outside; and
a pipe which can be connected, at its rear end away from said leading edge and passing through a second internal partition, to a pressurized hot air circuit and, at its front end toward said leading edge, to an injector injecting said pressurized hot air into said internal chamber,
is noteworthy in that it comprises:
an internal casing cooperating with said first and second internal partitions and with the internal face of the external wall of said cowl to delimit a volume enclosing said pipe;
at least one orifice for letting air into said volume; and
at least one orifice for extracting air from said volume.
Thus, by virtue of the present invention, said internal casing, which is continuous and integral, allows the nearby structures to be protected against the radiation of heat and leaks of pressurized hot air and against said pipe exploding. The pipe, with its connections and flanges, is isolated from the rest of the inside of the air inlet cowl. By virtue of the air inlet and outlet orifices, the inside of the casing is permanently ventilated, and this limits the amount of heat radiated by it. The heat-sensitive nearby structures are thus protected from any temperaturelinked deterioration or aging.
All the parts that make up said internal casing, which have a specific function and are located in and limited to the precise environment that needs to be protected, can be made of metal or of any other fire-resistant material, without this having too unfavorable an influence on the mass of said air inlet cowl. Thus, the present invention makes it possible to provide solutions to all the problems encountered in engine air inlet cowls, as far as the following are concerned:
resistance to high temperatures; and
ease of repair and inspection; indeed, by making the way in which said casing is mounted in said air inlet cowl removable, the parts that make up the thermal protection and the nearby parts (structure and systems) can be inspected.
In order to further increase this ease of repair and inspection, it is advantageous that, at the same end as the wall of said cowl, said internal casing should be fixed to a part of said wall that forms a removable panel.
Furthermore, in order to tolerate the thermal expansions and the relative movements, it is preferable that, at least at one of its ends, said internal casing should rest against the corresponding internal partition via an elastic seal.
One of said ventilation orifices may be made in said external wall of said air inlet cowl, near to said internal partition.
When the engine is of the bypass type and has a peripheral annular space delimited between said engine and its lateral cowling, in the region of the engine fan, it is advantageous that another of said ventilation orifices should be made in said second internal partition so as to place said volume and said peripheral annular space in communication. Thus, should said pipe burst, the pressurized hot air can be evacuated toward said peripheral annular space and the resulting rise in pressure is detected by the vent door, generally provided in this peripheral annular space. It is not therefore necessary to provide an overpressure detector specific to the air inlet cowl deicing system.
Of course, said ventilation orifices are calibrated in such a way that in normal operation (that is to say when said pipe has not burst), said casing is appropriately ventilated. This ventilation may be from the first internal partition toward the second or alternatively from said second internal partition toward the first.
REFERENCES:
patent: 2425630 (1947-08-01), McCollum
patent: 4674714 (1987-06-01), Cole et al.
pat
Aerospatiale - Societe Nationale Industrielle
Fisher Christen & Sabol
Gellner Jeffrey L.
Poon Peter M.
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