Patent Application
20180195416
The present invention relates to a turbine engine exhaust casing for an aircraft, the lifetime of which is increased.
More precisely, it relates to an exhaust casing allowing the forces created by the temperature differences between a shroud and a hub of said exhaust casing to be limited.
The lifetime of an exhaust casing (or Turbine Rear Frame, TRF) is highly impacted by the forces created by temperature differences between a shroud and a hub of said exhaust casing. More particularly these forces are created at the arms which connect the external shroud to the internal hub.
Thus, during the takeoff of the aircraft or acceleration phases, the shroud is heated faster than the hub which is more massive, and this temperature difference between the two parts creates tension forces at the arms which connect the shroud to the hub because, under the influence of heat, the shroud dilates faster than the hub.
On the contrary, upon stopping the turbomachine, the shroud cools faster than the hub, thus creating compression forces at said arms which connect the shroud to the hub.
One general goal of the invention is to propose a solution allowing the forces created by the temperature differences between the shroud and the hub to be limited, so as to increase the lifetime of the arms connecting the shroud to the hub, and thus that of the entire exhaust casing. Moreover, this solution must be simple so as to be able to be easily implemented on an aircraft turbine engine, without incurring a considerable excess cost.
More particularly, according to a first aspect, the invention proposes an exhaust casing for an aircraft turbine engine comprising a shroud, a hub forming a cavity, hollow arms connecting said shroud to said hub, and at least one mouth situated on the shroud and which is suitable to be connected to an outlet tube of a transient-operation valve of the turbine engine, characterized in that said at least one mouth is attached to the shroud in the extension of a hollow arm, so that an air flow exiting the outlet tube of the transient-operation valve penetrates into the hollow arm and circulates in the cavity of the hub.
Such a device allows the temperature difference between the hub and the shroud during takeoff or acceleration phases of the aircraft to be limited by heating said hub, and thus allows an increase in the lifetime of the exhaust casing.
According to an additional feature, the exhaust casing comprises at least one yoke arm and a hollow arm adjoining said yoke arm comprises a deflector so as to deflect the air flow exiting said hollow arm toward a stiffener of the yoke arm.
According to a supplementary feature, the hollow arm adjoining the yoke arm comprises a stiffener which comprises a side orifice, and the deflector is situated inside the stiffener of said hollow arm so as to deflect at least a portion of the air flow exiting said hollow arm toward the stiffener of the yoke arm through said side orifice.
According to a particular feature, the hollow arm which adjoins the yoke arm comprises a stiffener which comprises a front orifice, and the deflector is situated at said front orifice.
According to another feature, the deflector is a curved sheet-metal part.
According to an additional feature, the exhaust casing is an exhaust casing with tangential arms.
According to a second aspect, the invention proposes a turbine engine comprising an exhaust casing according to one of the aforementioned features, in which said turbine engine comprises a transient bleed valve comprising an outlet tube which is connected to a mouth of said exhaust casing.
According to a third aspect, the invention proposes an aircraft comprising a turbine engine according to the aforementioned feature.
Other characteristics, aims and advantages of the present invention will appear upon reading the detailed description which follows, and with reference to the appended drawings, given as non-limiting examples and in which:
Shown in
The exhaust casing 2 comprises a shroud 4 and a hub 5 which are connected by a plurality of arms 6, as well as mouths 3 which are situated on the shroud 4, forming an extension of several arms 6. The hub 5 comprises a cavity at its center.
Among this plurality of arms 6, the exhaust casing 2 comprises yoke arms 61 (three in the embodiment represented in
The exhaust casing 2 also comprises oil utility arms 62 in which are installed oil circulation circuits feeding the hydraulic circuits for controlling utilities (such as flaps, brakes, the landing gear). In the embodiment illustrated in
Finally, the exhaust casing 2 also comprises hollow arms 63 which each comprise a cavity which is open at both ends, hence at the shroud 4 and the hub 5. In the first embodiment, all the hollow arms 63 are connected to a mouth 3. More precisely, a mouth 3 is applied to the shroud 4 (by welding for example) in the extension of each hollow arm 63, so that when an outlet tube 30 is attached to the mouth 3, the air flow 7 exiting said outlet tube 30 penetrates directly into the cavity of the hollow tube 63. The mouth 3 is an applied part which is attached to the shroud 4 of the exhaust casing 2, and which makes it possible to ensure the attachment of the outlet tube 30 on the shroud 4, and its sealing.
As illustrated in
The transient-operation valve being a valve which allows a high-pressure compressor of the turbine engine to discharge during starting and acceleration, the air flow 7 is a hot air flow which allows the hub 5 to be heated, and thus to limit the temperature difference between the hub 5 and the shroud 4 during takeoff and acceleration phases of the aircraft.
Thus, the appearance of tension forces at the arms 6 which occur during takeoff or acceleration phases of the aircraft is limited, and the lifetime of the exhaust casing 2 is therefore increased.
Advantageously, despite the fact that the oil circulation circuits present in the oil utility arms 62 are heated by the air flow 7, there is no increase in the risk of coking of the oil. In fact, the high-pressure compressor discharging through the transient-operation valve only during starting or acceleration phases of the aircraft, the oil is not heated during the periods during which it no longer circulates, and thus the risk of coking is not increased.
Thus, this can be easily implemented on turbine engines without requiring costly adaptation work, and does not bring with it an oil coking problem. In fact, generally on known turbine engines, the mouths 3 to which are connected the outlet tubes 30 are disposed on the shroud 4 of the exhaust casing 2, so as to eject the air flow 7 between the arms 6 connecting the shroud to the hub 5. Thus, only a slight adaptation of the exhaust casing 2 is necessary.
In the first embodiment of the invention, so as to improve the homogeneity of the heating of the hub 5, and as illustrated in
The arms 6 each comprise a stiffener 60 which is situated inside the hub 5. As illustrated in
In the embodiment, the air flow 7 which leaves a hollow arm 63 which adjoins a yoke arm 61 is deflected toward the stiffener 60 of said yoke arm 61 by a deflector 8. The deflector 8 can be implemented by a curved sheet-metal part which is disposed at the stiffener 60 of said hollow arm 63 adjoining said yoke arm 61.
In the first embodiment illustrated in
According to a first variant of the first embodiment, which is illustrated in
In the first variant of the first embodiment, the deflector 8 is disposed at the front orifice 601 so as to deflect the air flow 7 toward the reinforcement 60 of the yoke arm 61.
According to a second variant of the first embodiment, which is illustrated in
Preferably, in the first embodiment, the air flow 7 exiting the hollow arms 63 is not directly deflected toward the oil utility arms 62, so as not to bring about overheating of the oil.
According to a second embodiment illustrated in
Thus, the arms 6 being inclined with respect to the normal with respect to the outer surface of the hub 5, the air flow 7 arrives in the interior of the hub 5 with an inclination with respect to the normal, which forms the vortex 9 under the influence of centrifugal force.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1556893 | Jul 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2016/051870 | 7/20/2016 | WO | 00 |
