Air inlet of an aircraft turboprop engine and method of using the same when the aircraft is on the ground

Abstract

An air inlet (1) of an aircraft turboprop (20) comprising an intake duct (2) for an air flow opening, at a bifurcation (5), into a supply duct (3) towards a turbine (25) and into a discharge duct (4) for foreign bodies from the air flow comprising a heat exchanger (7) for cooling a heat transfer fluid, a closing member (8) being controllable at the bifurcation (5) in: - a stowed position (P0) in which the air flow circulates in the discharge duct (4) from the bifurcation (5) towards a discharge outlet (6), a first deployed position in which the closing member (8) completely obstructs the discharge duct (4), and a second deployed position in which the closing member (8) partially obstructs the intake duct (2) to suck a reverse air flow into the discharge duct (4) when the aircraft is on the ground. Abstract figure: Figure 1

Description

Title of the invention: Air intake of an aircraft turboprop and method of using it when the aircraft is on the ground Technical field

[0001] The present invention relates to the field of aircraft turboprop engines.

[0002] In a known manner, an aircraft turboprop comprises one or more compressors, a combustion chamber and one or more turbines in which circulates a flow of air admitted at an air inlet of the turboprop. The rotational drive of the turbine by the air flow is transmitted to a propeller via a reduction gear in order to ensure the propulsion of the aircraft.

[0003] In a known manner, the air inlet of the aircraft turboprop comprises an intake duct opening, at a bifurcation zone, on the one hand into a supply duct and on the other hand into a discharge duct. The supply duct makes it possible to guide the air flow towards the compressor, the combustion chamber and the turbine. The discharge duct makes it possible to capture any foreign bodies in the air flow, such as ice or birds, and to guide them into a discharge outlet outside the aircraft turboprop.

[0004] It is known from patent application FR3029240A1 to mount an air-oil type surface heat exchanger in the discharge duct. The circulation of the air flow loaded with possible foreign bodies in the discharge duct thus makes it possible to cool the lubrication circuit which has been heated in contact with the equipment of the aircraft turboprop, such as the reducer.

[0005] In practice, when the aircraft is on the ground, for example during a holding phase or during a taxiing phase, known to those skilled in the art as "taxiing" or "ground idling", the air flow admitted into the intake duct of the air inlet is very low, which does not allow the heat exchanger to effectively cool the lubricating oil. This has the effect of increasing the temperature of the lubrication circuit and reducing the performance of the aircraft turboprop.

[0006] It has been proposed by the aforementioned patent application to extend the discharge duct to the aircraft nozzle to form a depression at the discharge outlet when the aircraft is on the ground. This makes it possible to increase the proportion of the air flow from the intake duct joining the discharge duct but does not make it possible to significantly increase the cooling performance.

[0007] The invention thus aims to increase the cooling performance of an aircraft turboprop air intake, in particular when the aircraft is on the ground. PRESENTATION OF THE INVENTION

[0008] The invention relates to an air inlet of an aircraft turboprop comprising an intake duct configured to admit an air flow into the aircraft turboprop, the air inlet comprising a supply duct and a discharge duct into which the intake duct opens at a bifurcation zone, the supply duct being configured to guide the air flow into at least one compressor of the aircraft turboprop, the discharge duct being configured to inertially capture foreign bodies in the air flow and guide them into a discharge outlet out of the aircraft turboprop, the discharge duct comprising a heat exchanger extending between the bifurcation zone and the discharge outlet and configured to cool a heat transfer fluid of the aircraft turboprop from the circulation of the air flow in the discharge duct.

[0009] The invention is remarkable in that the air inlet comprises at least one closing member mounted movably at the bifurcation zone and controllable in: • A stowed position, in which the air flow admitted into the intake duct is adapted to circulate in the discharge duct from the bifurcation zone towards the discharge outlet, to evacuate foreign bodies and cool the heat transfer fluid, • A first deployed position, in which the closing member completely obstructs the discharge duct, to maximize the flow of air admitted into the supply duct, and • A second deployed position, in which the closing member partially obstructs the intake duct, to draw into the discharge duct a reverse air flow circulating from the discharge outlet towards the bifurcation zone, so as to supply the supply duct and cool the heat transfer fluid when the aircraft is on the ground.

[0010] According to a preferred aspect, the second deployed position is suitable for a ground holding phase or for a ground taxiing phase of the aircraft, known to those skilled in the art respectively under the terms “ground idle” or “taxiing”.

[0011] Thanks to the different positions of the closing member, the invention makes it possible to promote the cooling of a heat transfer fluid while improving the performance of the aircraft turboprop. The invention is of particular interest when the aircraft is on the ground, in particular during a waiting phase, in that the particular position of the closing member makes it possible to form a depression in the bifurcation zone which makes it possible to reverse the direction of the air flow in the discharge duct. The circulation of the reverse air flow makes it possible both to ensure sufficient cooling of the heat transfer fluid and then to supply air to the supply duct parallel to the intake duct. The first deployed position makes it possible to promote the supply of air to the supply duct in the absence of conditions icing or risk of bird ingestion, while reducing aerodynamic losses induced by air circulation in the discharge outlet.

[0012] According to one aspect of the invention, the closing member is mounted at a joint between the intake duct and the discharge duct. The closing member thus mounted at the upstream end of the inlet of the discharge duct makes it possible to obstruct both the intake duct and the discharge duct according to the commanded position. The first deployed position and the second deployed position can be implemented by a single closing member in a simple and practical manner.

[0013] According to one aspect of the invention, the closing member is pivotally mounted between the stowed position, the first deployed position and the second deployed position. This ensures simple and practical movement.

[0014] According to one aspect of the invention, in the second deployed position, the closing member forms a deployment angle relative to the intake duct of between 5° and 180°, preferably of between 5° and 60° or between 120° and 175°. This makes it possible to generate a depression in the air flow downstream of the closing member, i.e. at the bifurcation zone, and promotes the suction of the reverse air flow.

[0015] According to a preferred aspect, in the stowed position, the closing member extends against the intake duct in a simple and practical manner. This avoids the need to provide a housing.

[0016] According to one aspect of the invention, the heat exchanger is of the surface type, namely the heat exchange interface between the air flow and the heat transfer fluid is formed by the wall of the discharge duct. The surface heat exchanger is devoid of fins. Such a heat exchanger has the advantage of not disturbing the flow of the air flow in the discharge duct. This allows in particular easy evacuation of foreign bodies and avoids any damage during the ingestion of foreign bodies.

[0017] The invention also relates to an aircraft turboprop comprising a propeller, an air inlet as described above and at least one turbine configured to drive the propeller from the circulation of the air flow. According to a preferred aspect of the invention, the intake duct of the air inlet is in the form of a scoop. According to a preferred aspect, the propeller extends upstream of the air inlet. According to another preferred aspect, the propeller extends downstream of the aircraft turboprop.

[0018] According to one aspect of the invention, the discharge outlet of the air inlet extends upstream of the turbine, and preferably upstream of a combustion chamber of the aircraft turboprop. The discharge duct thus has a reduced length facilitating the generation of the reverse air flow when the closing member is in the second deployed position.

[0019] According to one aspect of the invention, the aircraft turboprop comprises a second heat exchanger mounted downstream of the discharge outlet on an outer wall of the aircraft turboprop, the second heat exchanger being configured to cool the heat transfer fluid from the circulation of the air flow against the outer wall of the aircraft turboprop. The second heat exchanger advantageously ensures minimal continuous cooling of the heat transfer fluid while the heat exchanger mounted in the discharge duct provides additional cooling only when needed, in particular when the aircraft is on the ground, in particular during a waiting or taxiing phase, or during extreme hot outside temperature conditions. This makes it possible to undersize the second heat exchanger and not to provide a valve for regulating the air flow circulating in the second heat exchanger.

[0020] According to a preferred aspect of the invention, the second heat exchanger is of the matrix type, also known as a "volume exchanger". The second heat exchanger comprises a frame housing a bundle of tubes in which the heat transfer fluid circulates. The air flow circulates in the frame outside the tubes, which promotes heat exchange.

[0021] The invention also relates to a method of using an air inlet as described above, comprising, when the aircraft is on the ground, a step of controlling the second deployed position in which the closing member partially obstructs the intake duct, to suck into the discharge duct a reverse air flow circulating from the discharge outlet towards the bifurcation zone, so as to supply the supply duct and cool the heat transfer fluid.

[0022] The invention is particularly advantageous when the aircraft is on the ground, in particular during the taxiing or waiting phase of the aircraft on the ground, in which it makes it possible to improve the cooling of the heat transfer fluid thanks to the circulation of the reverse air flow.

[0023] The invention also relates to a method of using an aircraft turboprop engine as described previously comprising: • A step of controlling the first deployed position in which the closing member completely obstructs the discharge duct, to maximize the flow of air admitted into the supply duct, and • A step of cooling the heat transfer fluid by the second heat exchanger.

[0024] The invention allows better regulation of the temperature of the heat transfer fluid while promoting the performance of the aircraft turboprop. Indeed, the second heat exchanger can advantageously be undersized to limit its impact on drag, the additional cooling being provided by the heat exchanger mounted in the discharge duct. PRESENTATION OF FIGURES

[0025] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0026] [Fig.l] is a schematic representation in longitudinal section of an aircraft turboprop engine according to one embodiment of the invention.

[0027] [Fig. 2] is a schematic representation in longitudinal section of an air intake of the aircraft turboprop of [Fig. 1], in which the closure member is in a stowed position.

[0028] [Fig. 3] is a schematic representation in longitudinal section of the air inlet of the aircraft turboprop of [Fig. 1], in which the closing member is in a first deployed position.

[0029] [Fig.4] is a schematic representation in longitudinal section of the air inlet of the aircraft turboprop of [Fig.l], in which the closure member is in a second deployed position.

[0030] [Fig.5] is a schematic perspective representation of the air inlet of [Fig.4],

[0031] [Fig. 6] is a schematic representation in longitudinal section of the air intake of the aircraft turboprop engine illustrating the second deployed position of the closing member according to another embodiment of the invention.

[0032] [Fig.7] is a schematic perspective representation of the air inlet discharge duct of [Fig.l] according to one embodiment of the invention.

[0033] [Fig.8] is a schematic perspective representation of the wall of the air inlet discharge duct of [Fig.l] according to another embodiment of the invention.

[0034] [Fig.9] is a schematic perspective representation of the wall of the air inlet discharge duct of [Fig.l] according to another embodiment of the invention.

[0035] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0036] With reference to [Fig.l], the invention relates to an aircraft turboprop 20 comprising from upstream to downstream an air inlet 1, one or more compressors 23, a combustion chamber 24 and one or more turbines 25. The air inlet 1 is configured to admit an air flow coming from outside the aircraft turboprop 20 and flowing from upstream to downstream in the aircraft turboprop 20. The rotational drive of the turbine 25 by the air flow is transmitted to a propeller 21 via a reduction gear 22 in order to provide propulsion of the aircraft. The propeller 21 is in this example mounted upstream of the air inlet 1. The propeller 21 is alternatively mounted downstream of the turboprop 20. The air inlet 1 preferably has a scoop shape.

[0037] Still with reference to [Fig.l], the air inlet 1 of the aircraft turboprop 20 comprises an intake duct 2 opening, at a bifurcation zone 5, on the one hand into a supply duct 3 and on the other hand into a discharge duct 4. The supply duct 3 makes it possible to guide the air flow towards the compressor(s) 23, the combustion chamber 24 and the turbine(s) 25, called hot parts. The discharge duct 4 extends radially outwardly relative to the supply duct 3 and makes it possible to capture by inertia any foreign bodies in the air flow, such as frost or birds. The discharge duct 4 makes it possible to guide foreign bodies from the radially inner bifurcation zone 5 towards a radially outer discharge outlet 6, opening out of the aircraft turboprop 20, to protect the hot part(s) 23, 24, 25.

[0038] Still with reference to [Fig.l], the air inlet 1 also comprises a heat exchanger 7 mounted in the discharge duct 4 and configured to cool a heat transfer fluid from the circulation of the air flow in the discharge duct 4. The heat transfer fluid is typically in the form of a lubricating fluid, such as oil, having been heated in contact with moving equipment of the aircraft turboprop, such as the reduction gear. The heat transfer fluid is alternatively in the form of a cooling fluid for equipment of the aircraft turboprop, such as an electrical machine. The heat exchanger 7 is typically of the surface type without fins to allow the circulation of foreign bodies in the discharge duct 4 without damaging the exchanger.

[0039] According to the invention and still with reference to [Fig.l], the air inlet 1 comprises a closing member 8 mounted to move at the level of the bifurcation zone 5 and controllable in: • A stored position PO illustrated in [Fig.2], in which the air flow F admitted into the intake duct 2 is adapted to circulate in the discharge duct 4 from the bifurcation zone 5 towards the discharge outlet 6, to evacuate the foreign bodies E and cool the heat transfer fluid L, • A first deployed position PI illustrated in [Fig.3], in which the closing member 8 completely obstructs the discharge conduit 4, for maximize the air flow F admitted into the supply duct 3, and • A second deployed position P2 illustrated in figures 4 to 6, in which the closing member 8 partially obstructs the intake duct 2, to suck into the discharge duct 4 a reverse air flow F-INV circulating from the discharge outlet 6 towards the bifurcation zone 5, so as to supply the supply duct 3 and cool the heat transfer fluid L when the aircraft is on the ground.

[0040] The invention advantageously makes it possible to promote the cooling of the heat transfer fluid L when the aircraft is on the ground, in particular during a ground holding or taxiing phase, known to those skilled in the art under the terms of "taxiing" or "ground idling", and corresponding to the phase preceding takeoff and following landing during which the aircraft is adapted to move on the ground by means of the turboprop engine(s) 20. Such a taxiing or holding phase is characterized by a low intake of the air flow F at the intake duct 2. Thanks to the second deployed position P2 of the closing member 8 according to the invention, a local depression is formed at the bifurcation zone 5, which creates a pressure difference between the inside and the outside of the aircraft turboprop engine 20 and causes the suction of an inverse air flow F-INV into the discharge duct 4.The reverse air flow F-INV is sucked in at the discharge outlet 6 and circulates to the level of the bifurcation zone 5 where it joins the supply duct 3 with the air flow F coming from the intake duct 2. The suction of the reverse air flow F-INV into the discharge duct 4 advantageously makes it possible to ensure sufficient heat exchanges with the heat transfer fluid L in the heat exchanger 7 for efficient cooling, while contributing to supplying air to the supply duct 3.

[0041] The first deployed position PI of the closing member 8 also makes it possible, when the risk of ingestion of foreign bodies and the cooling requirements are low, typically during cruising speed, to promote the performance of the aircraft turboprop 20 by guiding the entire air flow F admitted into the supply duct 3.

[0042] Preferably and as illustrated in [Fig.l], the discharge outlet 6 of the discharge duct 4 extends upstream of the turbine(s) 25, preferably upstream of the combustion chamber 24, and preferably upstream of the compressor(s) 23. The discharge duct 4 thus has a reduced length which facilitates the suction of the reverse air flow F-INV when the closing member 8 is in the second deployed position P2. The size of the discharge duct 4 is further reduced.

[0043] According to another preferred aspect illustrated in [Fig.l], the heat exchanger 7 mounted in the discharge duct 4 is called "first heat exchanger 7" and the aircraft turboprop 20 comprises a second heat exchanger 27 mounted on the outer wall 26 of the aircraft turboprop 20 and also dedicated to cooling the heat transfer fluid L. The second heat exchanger 27 is preferably of the matrix type, also known as a "volume exchanger" to promote heat exchanges. The second heat exchanger 27 comprises a frame housing a bundle of tubes in which the heat transfer fluid L circulates. The air flow F circulates in the frame outside the tubes, which promotes heat exchanges. The second heat exchanger 27 is preferably mounted downstream of the discharge outlet 6. The second heat exchanger 27 allows the heat transfer fluid L to be continuously cooled while the first heat exchanger 7 provides intermittent cooling when the closing member 8 is in the stowed position PO or in the second deployed position P2.

[0044] The first heat exchanger 7 thus makes it possible to provide additional cooling at specific times, for example in the event of a high outside temperature, which makes it possible to undersize the second heat exchanger 27. The second heat exchanger 27 thus has a reduced size and mass, which promotes the aerodynamics of the aircraft turboprop 20. This also makes it possible not to provide a valve for regulating the flow rate of the air flow F circulating in the second heat exchanger 27, the regulation being implemented in the invention by the closing member 8 which regulates the performance of the first heat exchanger 7. This also provides a saving in mass and cost, and advantageously does not require any control of the second heat exchanger 27.

[0045] According to one aspect of the invention illustrated in [Fig. 1], the closing member 8 is pivotally mounted between the stowed position PO, the first deployed position PI and the second deployed position P2. The movement of the closing member 8 is controlled by a control member 9, such as a computer. The closing member 8 is preferably mounted at the joint 10 between the intake duct 2 and the discharge duct 4, namely at the upstream end of the inlet of the discharge duct 4. This allows the closing member 8 to alternately partially obstruct the intake duct 2 or completely obstruct the discharge duct 4. The closing member 8 is preferably in the form of a flap or a hatch. The closing member 8 is preferably unique, allowing the discharge duct 4 to be closed on its own.

[0046] In the stowed position PO illustrated in [Fig. 2], the closing member 8 is oriented upstream and extends against the wall of the intake duct 2, so as not to disturb the circulation of the air flow F in the air inlet 1. In the stowed position PO, the closing member 8 thus guides the air flow F in the continuity of the wall of the intake duct 2 in an aerodynamic manner. The stowed position PO corresponds to the extreme upstream pivoting position of the closing member 8, the wall of the intake duct 2 forming a stop.

[0047] In the first deployed position PI illustrated in [Fig. 3], the closing member 8 is oriented downstream and closes the inlet of the discharge duct 4. The closing member 8 connects the intake duct 2 upstream and the supply duct 3 downstream to guide the entire flow of air F admitted towards the compressor(s) 23. The first deployed position PI corresponds to the extreme downstream pivoting position of the closing member 8.

[0048] As illustrated in Figures 4 and 5, the second deployed position P2 corresponds to a controlled intermediate position between the stowed position PO and the first deployed position PL. In the second deployed position P2, the closure member 8 projects into the intake duct 2 to induce a depression in the air flow F downstream of the closure member 8 at the bifurcation zone 5. The closure member 8 forms a deployment angle α relative to the wall of the intake duct 2, namely relative to the stowed position PO, which is preferably between 5° and 180°. In the example of Figures 4 and 5, the closure member 8 is oriented upstream in the second deployed position P2, the deployment angle α being between 5° and 60°. This allows the generation of depression at the bifurcation zone 5 to promote the generation of the reverse air flow F-INV. Alternatively, as illustrated in [Fig.6], the closing member 8 is oriented downstream in the second deployed position P2, the deployment angle a being between 120° and 175°. This makes it possible to promote the guidance of the reverse air flow F-INV from the discharge duct 4 to the supply duct 3.

[0049] With reference to [Fig. 7], the first heat exchanger 7 is preferably surface-mounted, namely the heat exchange interface between the air flow and the heat transfer fluid is formed by the wall of the discharge duct 4. The surface heat exchanger comprises in this example channels fixed to the external face of the wall of the discharge duct 4 in which the heat transfer fluid L circulates. The heat exchanger 7 thus does not form an obstacle in the discharge duct 4, which allows easy evacuation of foreign bodies E. The channels extend along the length of the discharge duct 4 and allow circulation of the heat transfer fluid L in co-current or counter-current with the air flow F, in this example in co-current (and therefore in counter-current with the reverse air flow F-INV).The channels extend in this example over a portion of the discharge conduit 4 starting downstream of the bifurcation zone 5, to avoid a collision with the foreign bodies E, and extending to the air outlet 6.

[0050] Alternatively, as illustrated in Figures 8 and 9, the first heat exchanger 7 is in the form of a double wall between which the heat transfer fluid L circulates, one of the walls preferably being formed by the discharge duct 4. The first heat exchanger 7 preferably comprises elements for guiding the air flow F mounted between the two walls, such as honeycomb (see [Fig.8]), spacers (see [Fig.9]) and / or fins to ensure circulation of the heat transfer fluid L in one or more round trips depending on the length of the discharge duct 4.

[0051] With reference to figures 2, 3 and 4, the method of using the aircraft turboprop 20 consists of alternately controlling one of the stowed position PO, the first deployed position PI and the second deployed position P2 of the closing member 8, by means of the control member 10, depending on the speed of the aircraft and the external conditions.

[0052] The second deployed position P2 is preferably controlled when the aircraft is on the ground, in particular during a taxiing or waiting phase of the aircraft, preceding takeoff and following landing. This makes it possible to maintain a sufficient level of cooling of the heat transfer fluid L, in particular in the event of a high temperature of the heat transfer fluid L.

[0053] The first deployed position PI is preferably commanded during cruising speed, at high altitude, when the risk of ingestion of foreign bodies E, such as birds, is low. The first deployed position PI is also suitable in the absence of icing conditions. This makes it possible to concentrate all of the air flow F in the supply duct 3 to promote the propulsion of the aircraft.

[0054] The stowed position PO preferably corresponds to the default position of the closing member 8. The stowed position PO is for example controlled during takeoff or landing. This makes it possible to capture and evacuate any foreign bodies E while cooling the heat transfer fluid L.

[0055] Preferably, the method of use also comprises a step of cooling the heat transfer fluid L by the second heat exchanger 27. The second heat exchanger 27 advantageously makes it possible to ensure continuous minimal cooling of the heat transfer fluid L. The first heat exchanger 7 makes it possible to ensure additional intermittent cooling when the closing member 8 is in the stowed position PO or in the second deployed position P2. The second heat exchanger 27 can thus be undersized to limit aerodynamic losses. The invention thus makes it possible both to improve the cooling performance of the heat transfer fluid and to promote the propulsion performance of the aircraft.

Claims

Claims

1. An air inlet (1) of an aircraft turboprop (20) comprising an intake duct (2) configured to admit an air flow (F) into the aircraft turboprop (20), the air inlet (1) comprising a supply duct (3) and a discharge duct (4) into which the intake duct (2) opens at a bifurcation zone (5), the supply duct (3) being configured to guide the air flow (F) into at least one compressor (23) of the aircraft turboprop (20), the discharge duct (4) being configured to inertially capture foreign bodies (E) in the air flow (F) and guide them into a discharge outlet (6) out of the aircraft turboprop (20), the discharge duct (4) comprising a heat exchanger (7) extending between the bifurcation zone (5) and the discharge outlet (6) and configured to cool a heat transfer fluid (L) of the aircraft turboprop from the circulation of the air flow (F) in the discharge duct (4),the air inlet (1) being characterized in that it comprises at least one closing member (8) mounted movably at the bifurcation zone (5) and controllable in:, • A stowed position (PO), in which the air flow (F) admitted into the intake duct (2) is adapted to circulate in the discharge duct (4) from the bifurcation zone (5) towards the discharge outlet (6), to evacuate the foreign bodies (E) and cool the heat transfer fluid (L), • A first deployed position (PI), in which the closing member (8) completely obstructs the discharge duct (4), to maximize the air flow (F) admitted into the supply duct (3), and • A second deployed position (P2), in which the closing member (8) partially obstructs the intake duct (2), to suck into the discharge duct (4) a reverse air flow (F-INV) circulating from the discharge outlet (6) towards the bifurcation zone (5), so as to supply the supply duct (3) and cool the heat transfer fluid (L) when the aircraft is on the ground.

2. An air inlet (1) according to claim 1, wherein the air inlet member closure (8) is mounted at a joint (10) between the inlet duct (2) and the outlet duct (4).

3. Air inlet (1) according to one of claims 1 and 2, in which the closing member (8) is pivotally mounted between the stowed position (PO), the first deployed position (PI) and the second deployed position (P2).

4. Air inlet (1) according to one of claims 1 to 3, in which, in the second deployed position (P2), the closing member (8) forms a deployment angle (a) relative to the intake duct (2) of between 5° and 180°, preferably of between 5° and 60° or between 120° and 175°.

5. Air inlet (1) according to one of claims 1 to 4, in which the heat exchanger (7) is of the surface type.

6. Aircraft turboprop (20) comprising a propeller (21), an air inlet (1) according to one of claims 1 to 5 and at least one turbine (25) configured to drive the propeller (21) from the circulation of the air flow (F), the intake duct (2) of the air inlet (1) preferably being in the form of a scoop.

7. An aircraft turboprop (20) according to claim 6, wherein the discharge outlet (6) of the air inlet (1) extends upstream of the turbine (25), and preferably upstream of a combustion chamber (24) of the aircraft turboprop (20).

8. Aircraft turboprop (20) according to one of claims 6 and 7, comprising a second heat exchanger (27) mounted downstream of the discharge outlet (6) on an outer wall (26) of the aircraft turboprop (20), the second heat exchanger (27) being configured to cool the heat transfer fluid (L) from the circulation of the air flow (F) against the outer wall (26) of the aircraft turboprop (20).

9. Method of using an air inlet (1) according to one of claims 1 to 5, comprising, when the aircraft is on the ground, a step of controlling the second deployed position (P2) in which the closing member (8) partially obstructs the intake duct (2), to suck into the discharge duct (4) a reverse air flow (F-INV) circulating from the discharge outlet (6) towards the bifurcation zone (5), so as to supply the supply duct (3) and cool the heat transfer fluid (L).

10. A method of using an aircraft turboprop engine (20) according to claim 1, wherein the turboprop engine is a turboprop engine of an aircraft (20). claim 8, comprising: • A step of controlling the first deployed position (PI) in which the closing member (8) completely obstructs the discharge duct (4), to maximize the air flow (F) admitted into the supply duct (3), and • A step of cooling the heat transfer fluid (L) by the second heat exchanger (27).

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