ENGINE UNIT FOR AN AIRCRAFT

Description

TECHNICAL FIELD

[0001] The present invention relates to a propulsion assembly for an aircraft, said propulsion assembly comprising a propulsion system having an ejection nozzle ensuring the ejection of combustion gases from the propulsion system and a heat exchange system arranged at the level of the ejection nozzle to ensure a transfer of calories to the dihydrogen of the propulsion system, as well as an aircraft comprising at least one such propulsion system. PREVIOUS STATE OF THE ART

[0002] To move, an aircraft typically includes at least one propulsion system, comprising a propulsion unit housed in a nacelle, which can be either a turbojet or a turboprop engine. In each case, the propulsion system includes a rotating assembly that drives a fan or a propeller. The rotating assembly forms the core of the propulsion system and consists, from front to rear, of an air intake that allows air to be drawn into a channel within the core, a compressor that compresses the incoming air, a combustion chamber where the compressed air is mixed with fuel, and a turbine that expands the combustion gases and generates the rotation that is transmitted to the fan or propeller.

[0003] Downstream of the turbine, an ejection nozzle ensures the ejection of combustion gases.

[0004] It is also known, particularly in the case of dihydrogen, that the combustion efficiency of a fuel is improved if the fuel is heated before combustion. It is also known to use some of the hot combustion gases expelled from the exhaust nozzle to preheat the fuel.

[0005] Document FR 3 127 989 A1 discloses a propulsion assembly according to the prior art. DESCRIPTION OF THE INVENTION

[0006] One object of the present invention is to propose an alternative solution for safely heating dihydrogen before its combustion.

[0007] To this end, a propulsion system is proposed for an aircraft comprising: a nacelle, a propulsion system arranged inside the nacelle and comprising a fairing, a rotating assembly including a combustion chamber and housed in the fairing, an ejection nozzle located downstream of the combustion chamber and delimited by a rear portion of the fairing, called the nozzle wall, and ensuring the ejection of combustion gases from the combustion of dihydrogen in the combustion chamber, a dihydrogen tank, a supply pipe which connects the tank and the combustion chamber and which is a double-walled pipe with an inner wall delimiting an internal volume in which the dihydrogen circulates and around it an outer wall delimiting an external volume, and a deflection chamber arranged around the nozzle wall,where the nozzle wall is pierced with at least one upstream orifice arranged to allow the introduction of hot combustion gases into the deflection chamber and at least one downstream orifice arranged to allow the extraction of hot combustion gases from the deflection chamber, and where the supply pipe has a portion of pipe arranged within said chamber.

[0008] With such an arrangement, the calories from the combustion gases are transferred to the dihydrogen and the installation of a double-walled pipeline ensures a high level of safety even in the event of a leak.

[0009] According to a particular embodiment, the external volume contains a fluid.

[0010] Advantageously, the propulsion assembly includes a pump which is fluidly connected to the external volume and which is arranged to move the fluid in the external volume.

[0011] According to a particular embodiment, the external volume is evacuated.

[0012] Advantageously, the outer skin is equipped with fins.

[0013] According to a particular embodiment, the portion of piping surrounds the nozzle wall.

[0014] According to a particular embodiment, the portion of piping extends around the nozzle wall over an angular portion.

[0015] The invention also proposes an aircraft comprising at least one propulsion assembly according to one of the preceding variants. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which: There figure. 1 is a side view of an aircraft comprising a propulsion system according to the invention, The figure. 2 is a schematic representation, side view and cross-section, of a propulsion assembly according to the invention, and The figure. 3 is a schematic representation of detail III of the figure. 2 . DETAILED EXPLANATION OF IMPLEMENTATION METHODS

[0017] In the following description, terms relating to a position are taken with reference to an aircraft in a forward position, that is, as it is represented on the figure. 1 , where arrow F shows the direction of travel of the aircraft.

[0018] There figure. 1 shows an aircraft 100 which has a fuselage 102 on either side of which is fixed a wing 104. Under each wing 104 is fixed at least one propulsion assembly 151.

[0019] There figure. 2 Figure 151 shows the propulsion assembly comprising a nacelle 149 and a propulsion system 150 enclosed within the nacelle 149. In the embodiment of the invention presented here, the propulsion system 150 takes the form of a turboprop engine with a propeller 152 driven in rotation by a rotating assembly mounted inside a fairing 172 of the propulsion system 150 housed within the nacelle 149, but the propulsion system 150 can also take the form of a turbojet driving a fan. Thus, generally speaking, the propulsion system 150 comprises a rotating assembly and a moving element 152 (propeller or fan).

[0020] In the following description, and by convention, X is called the longitudinal axis which corresponds to the axis of rotation of the moving element 152 oriented positively in the direction of advance of the aircraft 100, Y is called the transverse axis which is horizontal when the aircraft is on the ground, and Z is called the vertical axis or vertical height when the aircraft is on the ground, these three axes X, Y and Z being orthogonal to each other.

[0021] There figure. 2 Figure 150 shows the propulsion system in the case of a turboprop engine. A rotating assembly 160 forms the core of the propulsion system 150 and comprises, from front to back, an air intake 162 which allows air to be introduced into a channel 164 of the core, a compressor 166 which compresses the air thus introduced, a combustion chamber 168 in which the compressed air and dihydrogen mix and burn, and a turbine 170 which expands the combustion gases and generates the rotation which is transmitted to the moving element, here the propeller 152. The elements of the rotating assembly 160 are surrounded by the fairing 172 formed of structural housings mounted around the elements of the rotating assembly 160 and which stiffen it in order to limit its distortions during operation.

[0022] The fairing 172 is, on the one hand, open at the front at the level of the air inlet 162 and delimits the duct 164 and is, on the other hand, open at the rear at the level of an ejection nozzle 174 which is downstream of the turbine 170 and therefore of the combustion chamber 168 and ensures the ejection of the combustion gases resulting from the combustion of dihydrogen and air in the combustion chamber 168. The rear part of the fairing 172 which surrounds the ejection nozzle 174 forms the nozzle wall 180.

[0023] The space between the nacelle 149 and the fairing 172 is occupied by various systems enabling the operation of the propulsion system 150. In particular, in order to supply the combustion chamber 168 with dihydrogen, the propulsion assembly 151 includes a dihydrogen tank 178, which is housed here in the wing 104, a supply line 176 that connects the tank 178 and the combustion chamber 168, and a pump 179 that moves the dihydrogen from the tank 178 to the combustion chamber 168 through the supply line 176. Without departing from the scope of the invention, the dihydrogen tank 178 can also be housed in another part of the aircraft 100, for example in the fuselage 102.

[0024] In order to heat the dihydrogen before its injection into the combustion chamber 168, and to obtain better combustion, the propulsion assembly 151 also includes a heat exchanger system 200, which is arranged in the space between the nacelle 149 and the fairing 172, and which is arranged, when the propulsion system 150 is in operation, to ensure an exchange of heat between the hot combustion gases circulating in the ejection nozzle 174 and the cooler dihydrogen circulating in the supply pipe 176.

[0025] The propulsion assembly 151 includes a cowling 210 which is fixed, preferably in a sealed manner, to the nozzle wall 180 and on its outside, and where the cowling 210 and the nozzle wall 180 define between them a deflection chamber 212 which is thus arranged around the nozzle wall 180. The fixing of the cowling 210 is carried out for example by welding or riveting along the periphery of the cowling 210.

[0026] The nozzle wall 180 is pierced with at least one upstream orifice 214 forming an air inlet to the deflection chamber 212 and at least one downstream orifice 216 forming an air outlet from the deflection chamber 212 to ensure the circulation of hot combustion gases in the deflection chamber 212.

[0027] Each upstream orifice 214 is arranged to allow the introduction of hot combustion gases from the ejection nozzle 174 into the deflection chamber 212 and each downstream orifice 216 is arranged to allow the extraction of hot combustion gases from the deflection chamber 212 to the ejection nozzle 174.

[0028] Each upstream orifice 214 is located at a front part of the cover 210 and each downstream orifice 216 is located at a rear part of the cover 210.

[0029] The heat exchanger system 200 includes a portion of piping 202 which is a portion of the supply piping 176 arranged in said diversion chamber 212 and the heat exchange takes place at the level of this portion of piping 202.

[0030] The section of pipe 202 thus passes a first time through the casing 210 coming from the dihydrogen tank 178 to enter the diversion chamber 212 and passes a second time through the casing 210 to exit the diversion chamber 212 and join the combustion chamber 168.

[0031] Thus, the portion of piping 202 is fixed in the deflection chamber 212 in the vicinity of the nozzle wall 180 and the heating of the dihydrogen takes place directly in the supply piping 176.

[0032] The hot combustion gases thus enter the deflection chamber 212 to heat the dihydrogen circulating in the supply pipe 176 before arriving at the combustion chamber 168.

[0033] In addition, for safety reasons, it is planned that the supply pipeline 176, and in particular the portion of pipeline 202, is a double-walled pipeline with an inner wall delimiting an internal volume in which dihydrogen circulates and an outer wall which is around the inner wall and where is delimited between the inner and outer walls an external volume not containing dihydrogen under normal operating conditions, i.e. without leakage.

[0034] Thus, even in the event of a leak at the level of the inner skin, the dihydrogen will spread into the outer volume while remaining isolated.

[0035] The outer volume can be evacuated or it can be filled with a fluid that is neutral with respect to dihydrogen, such as dinitrogen for example.

[0036] In the event of a leak at the outer skin level, the neutral fluid will spread out of the outer volume or the outer volume will fill with hot combustion gases.

[0037] To prevent a hydrogen leak at pipe section 202, the heat exchanger system 200 may include leak detection means and a control unit connected to the leak detection means. The heat exchanger system 200 also includes a valve mounted on the supply pipe 176 upstream of pipe section 202 relative to the direction of hydrogen flow, and controlled to open and close by the control unit. The control unit closes the valve when the leak detection means detect a leak.

[0038] Leak detection methods include, for example, pressure sensors placed in the outer volume. A leak in the inner or outer wall will be detected by the pressure sensors due to a change in pressure in the outer volume: for example, a leak in the inner wall will be detected if the pressure in the outer volume is approximately equal to the hydrogen pressure in the inner volume, and a leak in the outer wall will be detected if the pressure in the outer volume is approximately equal to the atmospheric pressure outside the pipe section 202.

[0039] When the external volume is evacuated, the external volume is, for example, fluidly connected to a vacuum pump.

[0040] When an external volume is filled with a fluid, the fluid can be static or in motion. When static, the fluid is not moving within the external volume, and in this case, the external volume is preferably fluidically connected to an expansion vessel that allows the pressure to be adjusted to the fluid temperature.

[0041] According to another embodiment, the heat exchanger system 200 includes a pump 220 which is fluidly connected to the external volume and which is arranged to move the fluid in the external volume.

[0042] There figure. 3 shows an enlargement of zone III for a particular embodiment.

[0043] The 202 pipeline section can consist of several channels, each double-walled, and the channels are supplied by a double manifold, where a first manifold supplies the different external volumes with fluid and where a second manifold supplies the different internal volumes with dihydrogen.

[0044] To improve heat exchange between the hot combustion gases and the dihydrogen, the outer skin is equipped with 302 fins made of a material with high thermal conductivity and bonded to the outer skin. The fins are immersed in the hot combustion gases.

[0045] According to a particular embodiment, the portion of the pipe 202 surrounds the nozzle wall 180 and thus has at least one spiral which goes around the nozzle wall 180. Such an arrangement increases the transfer of heat from the hot combustion gases.

[0046] According to another particular embodiment, the portion of piping 202 extends around the nozzle wall 180 but only over an angular portion around the longitudinal axis X.

[0047] In the embodiment of the invention presented to the figure. 3 , the nozzle wall 180 which is between the upstream orifice 214 and the downstream orifice 216 takes the form of an aerodynamic profile having at the upstream orifice 214 and downstream of it, a rounded leading edge 304 and at the downstream orifice 216, and upstream of it, a trailing edge 306.

[0048] To ensure good penetration of hot combustion gases through the upstream orifice 214, the leading edge 304 is offset inwards from the ejection nozzle 174 relative to the nozzle wall 180, which is upstream of the upstream orifice 214, to allow passage for the hot combustion gases. The distance 'd' shows this offset.

[0049] At the upstream orifice 214, the cowling 210 has an angle α of 10° to 15° relative to the nozzle wall 180 which is upstream of the upstream orifice 214.

[0050] At the downstream orifice 216, the cowling 210 has an angle β of 30° to 40° with respect to the nozzle wall 180 which is downstream of the downstream orifice 216.

Claims

1. Propulsion assembly (151) for an aircraft (100), comprising: - a nacelle (149), - a propulsion system (150) arranged inside the nacelle (149) and comprising a fairing (172), a rotary assembly (160) comprising a combustion chamber (168) and housed in the fairing (172), an exhaust nozzle (174) positioned downstream of the combustion chamber (168) and delimited by a rear portion of the fairing (172), referred to as nozzle wall (180), and configured to discharge the combustion gases produced by the combustion of the dihydrogen in the combustion chamber (168), - a dihydrogen tank (178), - a supply duct (176) which connects the tank (178) and the combustion chamber (168) and is a double-walled duct with an inner wall delimiting an inner volume in which the dihydrogen flows and, around it, an outer wall delimiting an outer volume, and - a bypass chamber (212) positioned around the nozzle wall (180), wherein at least one upstream orifice (214), arranged to allow the introduction of the hot combustion gases into the bypass chamber (212), and at least one downstream orifice (216), arranged to allow the discharge of the hot combustion gases from the bypass chamber (212), are formed in the nozzle wall (180), and wherein the supply duct (176) has a duct portion (202) arranged in said bypass chamber (212).

2. Propulsion assembly (151) according to Claim 1, characterized in that the outer volume contains a fluid.

3. Propulsion assembly (151) according to Claim 2, characterized in that it comprises a pump (220) which is fluidically connected to the outer volume and is arranged to set the fluid in the outer volume in motion.

4. Propulsion assembly (151) according to Claim 1, characterized in that the outer volume is under vacuum.

5. Propulsion assembly (151) according to one of Claims 1 to 4, characterized in that the outer wall is equipped with fins (202).

6. Propulsion assembly (151) according to one of Claims 1 to 5, characterized in that the duct portion (202) surrounds the nozzle wall (180).

7. Propulsion assembly (151) according to one of Claims 1 to 5, characterized in that the duct portion (202) extends around the nozzle wall (180) over an angular portion.

8. Aircraft (100) having at least one propulsion assembly (151) according to one of the preceding claims.