AIRCRAFT EQUIPPED WITH AN ENGINE AND AN EXHAUST PORTION AROUND AN ENGINE JET NOZZLE

Description

[0001] The present invention relates to an aircraft provided with an engine and an exhaust duct around an ejection nozzle of the engine.

[0002] An aircraft, for example a rotorcraft, may include an engine that expels combustion gases through an exhaust nozzle.

[0003] The engine is usually housed in a compartment of the aircraft called the "engine compartment". The engine compartment may be delimited by one or more firewalls and / or at least one cowling.

[0004] The aircraft may then comprise an exhaust duct with circular sections which is open to the engine compartment and to an environment external to the aircraft. This exhaust duct locally surrounds the exhaust nozzle. This exhaust duct may allow the combustion gases from the exhaust nozzle of an engine to be mixed with fresh air from the engine compartment and / or the gases to be directed towards preferential zones. The exhaust nozzle may be referred to as the primary or main nozzle, the exhaust duct being able to be referred to as the secondary nozzle.

[0005] If the engine fails to start, unburned fuel may be ejected into the exhaust nozzle. Depending on the pitch and / or roll attitude of the aircraft, this unburned fuel may then fall by gravity into the exhaust duct and then into the engine compartment or may be ejected from the aircraft.

[0006] The engine compartment can accommodate a drainage system to evacuate unburned fuel in turn.

[0007] However, some unburned fuel may remain trapped in the exhaust pipe and may accumulate at a low point.

[0008] Certification requirements may allow a volume of unburned fuel to remain in an exhaust duct, provided that the volume of unburned fuel remaining in the exhaust duct is less than a prescribed volume. Such a volume may be referred to as an "undrainable volume."

[0009] To achieve this goal, an exhaust duct may include a low point leading to a drainage system. Such a drainage system is effective but in fact has a significant mass.

[0010] Document US2022 / 0154613 A1 describes a single-engine helicopter having a nozzle with a kidney-shaped section to direct exhaust gases away from the tail boom of the helicopter.

[0011] Document EP3381792 B1 describes an aerodynamic drainage device provided with a base connected to an upper part by an intermediate part.

[0012] Document EP3084187 describes a drainage device for an engine. This device comprises a collector, means for pumping fluids contained in the collector and monitoring means configured to signal abnormal collection of fluids by the collector.

[0013] Document CA 2 860 080 A1 is also known. Document CA 2 860 080 A1 describes an exhaust duct which covers an ejection nozzle over a longitudinal distance, forming a peripheral opening between the ejection nozzle and this exhaust duct.

[0014] The present invention therefore aims to propose an innovative exhaust duct aimed at minimizing the volume of unburned fuel in the exhaust duct.

[0015] Such an exhaust duct is configured to be arranged around an exhaust nozzle of an engine, the exhaust duct having a plurality of sections, said sections comprising an inlet section and an outlet section, the exhaust duct extending along a guideline from the inlet section to the outlet section, the outlet section being configured to expel gases ejected by the exhaust nozzle.

[0016] Furthermore, the sections are circular between the inlet section and the outlet section, with the exception of the sections of a deformed section, arranged between the included or non-included inlet section and the included or non-included outlet section, each section of the deformed section comprising a lower sector and an upper sector, the lower sector having a non-circular shape so that at least one volume of liquid that cannot reach the inlet section and the outlet section by gravity is less than a volume threshold in the presence of pitch and roll angles respectively within predetermined pitch and roll angular ranges.

[0017] Conventionally, an aircraft can be designed so that its roll and pitch attitude is always within predetermined limits, particularly on the ground or even under certain conditions. The expression "predetermined pitch and roll angular ranges" means that these ranges are imposed by the manufacturer and therefore represent a characteristic associated with the exhaust duct.

[0018] Compared to an exhaust duct with circular sections, the exhaust duct has a deformed section. This deformed section is modified, or even truncated, compared to a section with circular sections so that each volume of liquid that could not reach the inlet section or the outlet section by gravity, with common roll and pitch angles included in said predetermined roll and pitch angular ranges, is less than an imposed volume threshold. The deformed section may have a flat, a gutter, one or more bumps for example

[0019] Regardless of the roll and pitch attitude of the aircraft equipped with an exhaust duct on the ground and within the imposed attitude limits, the geometry of the exhaust duct ensures that any liquid volume retained in the exhaust duct is less than the permitted volume threshold. This permitted volume threshold may be imposed by certification requirements, and for example by a certification regulation and / or a supplement to a certification regulation.

[0020] Therefore, it is not necessary to arrange a specific drainage system to drain this volume of liquid within the exhaust duct.

[0021] Under these conditions, the mass of the system can be optimized.

[0022] Furthermore, the development of an exhaust duct is complex due in particular to the high temperature of the ejected gases of the order of several hundred degrees Celsius, the pressures to be supported, as well as the vibration constraints.

[0023] Modifying an exhaust duct is therefore tricky. However, a maximum and local deviation of one to two centimeters compared to an exhaust duct with circular sections can be sufficient to limit each maximum volume of unburned fuel in the exhaust duct to a permitted volume. The aerodynamics of the exhaust duct can then be slightly impacted, or within acceptable margins.

[0024] From another financial aspect, the exhaust duct can keep a reasonable cost.

[0025] The exhaust duct may include one or more of the following features, alone or in combination.

[0026] Thus, the exhaust duct may comprise two half-shells joined to each other, one of the two half-shells comprising the lower sector of each section and the other half-shell comprising the upper sector of each section. The half-shell comprising the upper sectors may be of semi-cylindrical shape. Only the half-shell comprising the lower sectors is then deformed. The impact of truncating the exhaust duct is then minimized.

[0027] Alternatively, the exhaust duct may comprise two identical half-shells joined to each other, the two half-shells being symmetrical with respect to a plane containing said guideline, one of the two half-shells comprising the lower sectors of said sections of the deformed section and the other half-shell comprising the upper sectors of said sections of the deformed section.

[0028] In the case of a twin-engine aircraft, the two half-shells can allow the production of any of the exhaust ducts. This solution makes it possible to limit manufacturing tools.

[0029] The lower half-shell and the upper half-shell of one exhaust duct may form the upper half-shell and the lower half-shell of the other exhaust duct, respectively.

[0030] According to a possibility compatible with the previous ones, at least the inlet section or the outlet section can be circular.

[0031] Optionally, the deformed section is between the non-inclusive inlet section and the non-inclusive outlet section, or may include one of these sections.

[0032] According to a possibility compatible with the previous ones, each section of the deformed section can have a non-circular shape arranged between two arcs of a circle.

[0033] The non-circular shape corresponds to the modified area of ​​the exhaust duct, compared to an exhaust duct with circular sections.

[0034] Optionally, the non-circular shape can be a flat shape.

[0035] Therefore, the exhaust duct has at least one flat part, which makes it possible to avoid having an area forming a receptacle which does not allow fuel to escape.

[0036] In another aspect, each section may be orthogonal to the guideline

[0037] Optionally, said guideline may be curved.

[0038] Furthermore, an aircraft may be equipped with at least one engine, the engine comprising an exhaust nozzle for at least ejecting gases, said aircraft comprising an exhaust duct according to the invention arranged at least partially around the exhaust nozzle.

[0039] The invention also relates to a method for designing an exhaust duct configured to be arranged around an ejection nozzle of an engine, the exhaust duct having a plurality of sections, said sections comprising an inlet section and an outlet section, the exhaust duct extending along a guideline from the inlet section to the outlet section, the outlet section being configured to expel gases ejected by the ejection nozzle.

[0040] The design method comprises the definition of a circular section hose extending from the inlet section to the outlet section, the design method comprising at least one modification phase comprising the following steps: determining at least one undrainable volume delimited by the hose and in which a liquid cannot reach by gravity the inlet section and the outlet section for pitch and roll angles respectively included in predetermined pitch and roll angular ranges, if no undrainable volume is greater than or equal to a volume threshold, assigning a geometry of the hose to the exhaust duct, if at least one undrainable volume is greater than or equal to the volume threshold: (i) positioning a predetermined shape intersecting the hose, said at least one undrainable volume being present between the hose and the predetermined shape, (ii) modifying the hose, the part of the hose located under the predetermined shape and comprising said at least one undrainable volume being cut and replaced locally by the predetermined shape, (iii) carrying out a new modification phase with the hose obtained following said modification of the hose.

[0041] The hose used to initiate the process can have the shape of a standard exhaust duct with circular sections.

[0042] The term "undrainable volume" refers to a volume in which a liquid remains trapped in the presence of the permitted roll and pitch angles.

[0043] According to the method, an operator defines a geometric shape called a "casing". A predetermined shape is moved relative to the casing, in order to position the non-drainable volume between this predetermined shape and the casing. The part of the casing included in this predetermined shape and comprising the non-drainable volume is then removed and replaced locally by the predetermined shape to form a new casing. The modification phase is then carried out iteratively until an non-drainable volume is obtained that is lower than a volume imposed by the manufacturer and / or a certification requirement. The exhaust duct to be manufactured is then defined so as to have the final shape of the casing obtained at the end of the design process.

[0044] Optionally, the predetermined shape can be a plane.

[0045] Optionally, the determination of at least one undrainable volume delimited by the hose and in which a liquid cannot reach by gravity the inlet section and the outlet section for pitch and roll angles respectively included in said predetermined pitch and roll angular ranges may comprise the following step: for a plurality of attitudes of the exhaust duct permitted by the predetermined roll and pitch angular ranges, each attitude being associated with a roll angle and a pitch angle, determination of an intermediate volume in which a liquid cannot reach the inlet section and the outlet section by gravity, said at least one undrainable volume being equal to a sum of said intermediate volumes.

[0046] This feature allows multiple attitudes to be taken into consideration.

[0047] The invention also relates to a method of manufacturing an exhaust duct configured to be arranged around an ejection nozzle of an engine.

[0048] This manufacturing method comprises a definition of a geometry of the exhaust duct by applying the aforementioned design method, then a step of manufacturing the exhaust duct to give this exhaust duct said geometry.

[0049] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there figure 1 , a sectional view of an exhaust duct within an aircraft according to the invention, the figure 2 , a diagram illustrating an exhaust duct according to the invention, the figure 3 , a diagram illustrating an aircraft comprising two exhaust ducts according to the invention, the figure 4 , a diagram illustrating a step of determining at least one undrainable volume during the manufacturing process of an exhaust duct according to the invention, the figure 5 , a diagram illustrating a step of positioning a predetermined shape cutting the hose during the manufacturing process of an exhaust duct according to the invention, the figure 6 , a diagram illustrating a step of modification of the hose during the manufacturing process of an exhaust duct according to the invention, the figure 7 , a diagram illustrating a step of manufacturing said exhaust duct during the method of manufacturing an exhaust duct according to the invention.

[0050] Elements present in several distinct figures are assigned a single reference.

[0051] There figure 1 has an exhaust duct 30 according to the invention. This exhaust duct 30 can be arranged on a vehicle and in particular an aircraft 1. The exhaust duct 30 and the aircraft 1 are configured to be able to reach, in particular on the ground, a roll angle contained within a roll angular range imposed by the manufacturer and a pitch angle contained within a pitch angular range imposed by the manufacturer.

[0052] Such an aircraft 1 comprises an airframe 3 in which there is also at least one engine 10. This engine 10 is housed at least partially in an engine compartment 5.

[0053] The engine compartment 5 is delimited by at least one wall 6, 7, 8 and 9. The wall(s) 6, 7, 8 and 9 may be fireproof walls, for example fireproof. For example, the engine compartment 5 is delimited along a longitudinal axis by at least one longitudinal wall 6, 8. For example, the engine compartment 5 is delimited along a transverse axis by at least one transverse wall 7 and a cowl, and vertically at least by a bottom wall 9. According to the example illustrated, the aircraft 1 comprises a bottom wall 9 and a transverse wall 7 which extend between two longitudinal walls 6, 8.

[0054] Optionally, the engine compartment 5 may comprise a conventional drainage system. This drainage system may comprise at least one orifice 90 provided in the bottom wall 9, at least one pipe, at least one inclined plane provided in the bottom wall 9, etc.

[0055] Furthermore, the motor(s) 10 may each comprise a power shaft, connected to a mechanical power transmission chain 4, possibly passing through a longitudinal wall 8. This mechanical power transmission chain 4 may set at least one rotor in motion, and for example a rotary wing 2.

[0056] The engine(s) 10 may be heat engines capable of burning fuel to drive each power shaft. According to one possibility, the engine(s) 10 may be turboshaft engines. Alternatively, the engine(s) 10 may be piston engines, for example.

[0057] Regardless of the nature of the engine(s) 10 and their arrangement, each engine 10 comprises an ejection nozzle 20 for at least ejecting gases resulting from the combustion of the fuel according to arrow F1. For example, the ejection nozzle 20 passes through a longitudinal wall 6.

[0058] Therefore, an exhaust duct 30 according to the invention surrounds the ejection nozzle 20, namely the entire ejection nozzle 20 or a section of the ejection nozzle 20 and for example at least one end zone of the ejection nozzle 20 through which gases are expelled. For example, the exhaust duct 30 surrounds at least a portion of the ejection nozzle 20 located outside the engine compartment 5.

[0059] The exhaust duct 30 may comprise a peripheral wall 31. The peripheral wall 31 delimits an internal volume 33 located inside the exhaust duct 30 and accommodating at least one section of the exhaust nozzle 20.

[0060] Furthermore, the exhaust duct 30 has a succession of sections 32 aligned along a guideline 40. The term “section” designates a section of the exhaust duct in a plane.

[0061] Each section 32 may extend orthogonally to the guideline 40. Furthermore, the guideline 40 may be a straight line segment, or may be curved according to the illustrated examples.

[0062] Therefore, the exhaust duct 30 extends along the guideline from an inlet section 35, possibly opening onto the engine compartment 5, to an outlet section 36, possibly opening onto an EXT medium located outside the aircraft 1. Therefore, air present in the compartment 5 can be sucked into the exhaust duct 30, then is expelled outside the vehicle with gases coming from the ejection nozzle 20 via the outlet section 36.

[0063] Furthermore, all sections 32 are circular, with the exception of sections 310 of a deformed section 50. In other words, sections 310 of the deformed section 50 are not circular, sections 320 not belonging to the deformed section 50 being circular.

[0064] Reference 32 is assigned to any section, references 310, 320, 311, 312, 35, 36 designating particular sections if necessary.

[0065] The deformed section 50 extends along the guideline 40 between a first section 311 and a second section 312.

[0066] The deformed section 50 is arranged between the inlet section 35, included or not included, and the outlet section 36, included or not included. Therefore, the first section 311 may be the inlet section 35 or another section downstream of the inlet section 35 according to the example illustrated. Similarly, the second section 312 may be the outlet section 36 or another section upstream of the outlet section 36 according to the example of the figure 1 In other words, the inlet section 35 and / or the outlet section 36 may be circular depending on the location of the deformed section 50.

[0067] Each section 310 of the deformed section 50 extends from a lower sector 55 to an upper sector 56, the upper sector 56 being located above the lower sector 55 in the eyes of an individual when the vehicle is resting on the ground in a normal position, namely not turned over and for example on its landing gear in the context of an aircraft 1.

[0068] Reference 55 is assigned to any lower sector of the deformed section 50 and reference 56 is assigned to any upper sector of the deformed section 50.

[0069] Therefore, at least the lower sector 55 of each section of the deformed section 50 has a non-circular shape. This non-circular shape has the function of maintaining at least one volume of liquid below a volume threshold, this volume of liquid not being able to reach by gravity the inlet section 35 and the outlet section 36 in the presence of pitch and roll angles respectively included in said predetermined pitch and roll angular ranges.

[0070] Thus, regardless of the current roll and pitch angles and as long as these current roll and pitch angles remain within the predetermined roll and pitch angular ranges, the exhaust duct does not contain any continuous volume of liquid greater than or equal to the volume threshold. For example, the exhaust duct 30 may comprise one or more distinct volumes of liquid, each of these volumes of liquid being less than the volume threshold.

[0071] In reference to the figure 2 , each section of the deformed section 50 can thus have a non-circular shape 70, possibly arranged between two arcs of a circle 71, 72. This non-circular shape is notably present in the lower sectors 55 of the sections 310 of the deformed section 50.

[0072] In particular, the non-circular shape 70 may be a flat shape, namely straight.

[0073] Therefore, the exhaust duct 30 has a generally cylindrical shape, flattened locally at least in the lower part to avoid having a lower zone which cannot be drained and which is capable of accommodating a volume of liquid greater than or equal to an imposed volume threshold.

[0074] According to another characteristic, the exhaust duct 30 can be manufactured using two half-shells 60, 61, 62 joined to each other. One of the two half-shells 61 comprises the lower sectors 55 of the sections 310 of the deformed section 50 and the other half-shell 62 comprises the upper sectors 56 of the sections 310 of the deformed section 50.

[0075] Optionally, the two half-shells 61, 62 are identical. Once joined to form the exhaust duct 30, the half-shells 61, 62 are symmetrical with respect to a plane 100 containing the guideline 40.

[0076] In reference to the figure 3 , a vehicle 1 may comprise two engines 10 and two respective exhaust ducts 301, 302. The two exhaust ducts 301, 302 may then be identical, and for example arranged symmetrically with respect to a vertical plane 101.

[0077] THE figures 4 à 6 illustrate a method of designing and manufacturing an exhaust duct 30 according to the invention.

[0078] In reference to the figure 4 , the method comprises the definition STP1 of a hose 81 with circular sections extending from the inlet section 35 to the outlet section 36, for example with a CAD computer-aided design system.

[0079] In addition, the method comprises at least one modification phase PHAS. Each modification phase PHAS comprises a determination STP2 of one or more undrainable volumes 82 delimited in the hose 81 and in which a liquid cannot reach by gravity the inlet section 35 and the outlet section 36 for pitch and roll angles respectively included in said predetermined pitch and roll angular ranges.

[0080] For example, for a plurality of attitudes of the exhaust duct 30, each attitude corresponding to an inclination of the exhaust duct 30 according to a roll angle and a pitch angle authorized by the predetermined roll and pitch angular ranges, the modification phase PHAS comprises a determination STP2.1 of at least one intermediate volume in which a liquid cannot reach by gravity the inlet section 35 and the outlet section 36, for example with the computer-aided design system CAD. Each undrainable volume is then equal to a sum of the corresponding intermediate volumes.

[0081] If no undrainable volume 82 is greater than or equal to a volume threshold, the method comprises fixing the definition. In particular, the design method comprises the allocation STP5 of the final geometry of the hose, namely its shape, to the exhaust duct 30.

[0082] In reference to the figure 5 , if at least one undrainable volume is greater than or equal to the volume threshold, the modification phase PHAS comprises a positioning STP3 of a predetermined shape 83 which cuts the hose 81, for example with the computer-aided design system.

[0083] For example, the predetermined shape 83 may be a plane.

[0084] The predetermined shape 83 is positioned so that each undrainable volume is present between the hose 81 and this predetermined shape 83. The predetermined shape 83 may be tangent to at least one undrainable volume. The predetermined shape may extend horizontally in the aircraft reference frame.

[0085] In reference to the figure 6 , the modification phase PHAS then comprises a modification STP4 of the casing 81. The casing 81 is deformed so that the part of the casing 81 located under the predetermined shape 83 and comprising the undrainable volume(s) is cut and replaced locally by the predetermined shape 83. According to the example illustrated, a flat bottom then replaces the entire truncated area of ​​the casing 81.

[0086] From then on, the design process involves carrying out a new PHAS modification phase with the modified hose, and so on until each undrainable volume is lower than the imposed volume threshold.

[0087] In reference to the figure 7 , the design process includes, at the end of the PHAS modification phase(s), the STP5 allocation of the final geometry of the hose to the future exhaust duct 30.

[0088] Subsequently, the exhaust duct 30 is manufactured. For example, the STPF manufacturing of the exhaust duct 30 based on the modified hose comprises the manufacturing of two half-shells, and the stamping of at least one of the half-shells.

[0089] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is of course possible to replace a means described by an equivalent means without departing from the scope of the present invention and the claims.

Claims

1. Exhaust duct (30) configured to be disposed around an ejection nozzle (20) of an engine (10), the exhaust duct (30) featuring a plurality of sections (32), said sections comprising an inlet section (35) and an outlet section (36), the exhaust duct (30) extending along a guiding line (40) from the inlet section (35) to the outlet section (36), the outlet section (36) being configured to expel gases ejected by the ejection nozzle (20), characterised in that said sections are circular between the inlet section (35) and the outlet section (36), with the exception of the sections (310) of a deformed length (50), each section of the deformed length (50) comprising a lower section (55) and an upper section (56), the lower section (55) having a non-circular shape so that at least one volume of liquid unable by gravity to reach the inlet section (35) and the outlet section (36) is less than a volume threshold in the presence of pitch and roll angles contained respectively within the predetermined angular ranges in pitch and in roll.

2. Exhaust duct according to claim 1, characterised in that the exhaust duct (30) includes two identical half shells (61, 62) coupled together, the two half shells (61, 62) being symmetrical with respect to a plane (100) containing said guiding line (40), one of the two half shells (61) comprising the lower sections of said sections of the deformed length (50) and the other half shell (62) comprising the upper sections of said sections of the deformed length (50).

3. Exhaust duct according to either one of claims 1 or 2, characterised in that at least the inlet section (35) or the outlet section (36) is circular.

4. Exhaust duct according to any one of claims 1 to 3, characterised in that each section of the deformed length (50) features a non-circular shape (70) disposed between two arcs of a circle (71, 72).

5. Exhaust duct according to claim 4, characterised in that the non-circular shape (70) is flat in shape.

6. Exhaust duct according to any one of claims 1 to 5, characterised in that each section is orthogonal to the guiding line (40).

7. Exhaust duct according to any one of claims 1 to 6, characterised in that said guiding line (40) is curved.

8. Aircraft (1) equipped with at least one engine (10), the engine (10) comprising an ejection nozzle (20) for at least ejecting gases, said aircraft (1) comprising an exhaust duct (30) disposed at least partially around the ejection nozzle (20), characterised in that the exhaust duct (30) is according to any one of claims 1 to 7.

9. Method for designing an exhaust duct (30) configured to be disposed around an ejection nozzle (20) of an engine (10), the exhaust duct (30) featuring a plurality of sections, said sections comprising an inlet section (35) and an outlet section (36), the exhaust duct (30) extending along a guiding line (40) from the inlet section (35) to the outlet section (36), the outlet section (36) being configured to expel gases ejected by the ejection nozzle (20), characterised in that the design method includes (STP1), defining a flexible pipe (81) with circular sections extending from the inlet section to the outlet section, the design method including at least one modification phase (PHAS) comprising the following steps: - (STP2) determining at least one non-drainable volume (82) delimited by the flexible pipe (81) and in which a liquid cannot by gravity reach the inlet section (35) and the outlet section (36) with pitch and yaw angles contained respectively within the predetermined angular ranges in pitch and in roll, - if no non-drainable volume is greater than or equal to a volume threshold, (STP5) assigning a flexible pipe (81) geometry to the exhaust duct (30), - if at least one non-drainable volume is greater than or equal to the volume threshold: (i) (STP3) positioning a predetermined shape (83) intersecting the flexible pipe (81), said at least one non-drainable volume being present between the flexible pipe (81) and the predetermined shape (83), (ii) (STP4) modifying the flexible pipe (81), the part of the flexible pipe (81) situated under the predetermined shape (83) and comprising said at least one non-drainable volume being locally intersected and replaced by the predetermined shape (83), (iii) performing a new modification phase (PHAS) with the flexible pipe obtained further to said modification (STP4) of the flexible pipe (81).

10. Method according to claim 9, characterised in that the predetermined shape is a plane.

11. Method according to either one of claims 9 or 10, characterised in that said determination (STP2) of at least one non-drainable volume delimited by the flexible pipe (81) and in which a liquid cannot by gravity reach the inlet section (35) and the outlet section (36) with pitch and roll angles contained respectively within said predetermined angular ranges in pitch and in roll includes: - for a plurality of attitudes of the exhaust duct (30) authorised by the predetermined angular ranges in pitch and roll, (STP2.1) determining an intermediate volume in which a liquid cannot by gravity reach the inlet section (35) and the outlet section (36), said at least one non-drainable volume being equal to a sum of said intermediate volumes.

12. Method for manufacturing an exhaust duct (30) configured to be disposed around an ejection nozzle (20) of an engine (10), characterised in that the manufacturing method includes defining a geometry of the exhaust duct (30) by applying the design method according to any one of claims 9 to 11, then a stage of manufacturing the exhaust duct in order to confer said geometry to this exhaust duct.