Patent Description:
In aircraft engines, centrifugal compressor stages typically have in fluid flow sequence an intake, a centrifugal impeller extending axially from the intake to a centrifugal impeller outlet, a diffuser extending radially outwardly from the centrifugal impeller outlet, and a collector receiving the air from the outlet of the diffuser and guiding it to an outlet. The role of the diffuser is to gradually slow the gas velocity to convert a portion of the flow's high kinetic energy at the outlet of the impeller into static pressure at the collector.

The design of aircraft engine components is typically very complex in nature, since many different, and often competing, factors are to be taken into consideration. Indeed, while durability and reliability of components typically receives a very significant degree of attention, many other considerations cannot be ignored, such as manufacturing constraints, production costs, maintenance, and weight. Weight has always been a significant consideration in aircraft engines since it is directly related to fuel efficiency during flight, and can directly affect aircraft range and capacity for instance. Weight is receiving an ever-increasing degree of attention in a context of increasing environmental awareness. While existing centrifugal compressor stages have been satisfactory to a certain degree, there remained room for improvement.

<CIT> discloses a compressor section according to the preamble of claim <NUM>.

According to the invention, there is provided a compressor section comprising: a centrifugal impeller operable to rotate around an axis extending between a front and a rear, the centrifugal impeller having blades extending between a compressor inlet and a compressor outlet, the compressor inlet oriented towards the front and axially relative the axis, the compressor outlet oriented radially outwardly relative the axis; a diffuser having a diffusion flow path extending radially between a diffuser inlet and a diffuser outlet, the diffuser inlet in fluid flow communication with the compressor outlet, the diffusion flow path between a rear wall and a front wall; a collector extending circumferentially around the axis, having a collector inlet in fluid communication with the diffuser outlet, and a collector outlet; and hollow structural members protruding rearwardly from the rear wall, the hollow structural members being circumferentially interspaced from one another, each hollow structural member having a length extending radially along the rear wall and having an internal conduit extending radially inwardly along the length, between a conduit inlet in fluid communication with the diffuser outlet and a conduit outlet located radially inwardly from the conduit inlet.

In some embodiments of the above compressor section, the hollow structural members extend radially between an inner structural ring and an outer structural ring, the inner structural ring and the outer structural ring being concentric to the axis, pockets being delimited between corresponding pairs of the hollow structural members, between the inner structural ring and the outer structural ring, each pocket leading to a corresponding web portion of the rear wall.

In some embodiments of any of the above, the hollow structural members each form, with the rear wall, a corresponding hollow structural section.

In some further embodiments of the above embodiment, the hollow structural section has a rectangular cross-section with rounded corners.

In some further embodiments of any of the two above embodiments, the conduit inlets are formed of corresponding open ends of the hollow structural sections.

In some embodiments of any of the above, the rear wall, the front wall, and the hollow structural members all form part of a diffuser core, the diffuser core being a monolithic component.

In some further embodiments of the above embodiment, the conduit outlets are formed of corresponding apertures, the apertures defined across a portion of the diffuser core.

In some further embodiments of any of the two above embodiments, the diffuser core has vanes, the vanes circumferentially interspaced from one another relative the axis and each extending axially between the front wall and the rear wall, the diffusion flow path including diffusion flow passages each extending between a corresponding pair of said vanes.

In some embodiments of any of the above, the collector is a scroll, the scroll having a radial-axial cross-sectional area which progressively increases along a circumferential flow path leading to the collector outlet.

In some embodiments of any of the above, the blades are rooted to a hub, the compressor section further comprising a shroud, the shroud and the hub delimiting a compressor flow path, the compressor flow path tapering between the compressor inlet and the compressor outlet.

According to a further aspect of the invention, there is provided an aircraft engine comprising in sequential flow communication an intake, a compressor section according the above described first aspect and corresponding embodiments, and a combustor.

The invention relates to the diffuser of the above described compressor section. Such a diffuser comprises a diffusion flow path defined circumferentially around an axis and extending radially between a diffuser inlet and a diffuser outlet, the diffuser inlet in fluid flow communication with the compressor outlet, the diffusion flow path between a rear wall and a front wall, and hollow structural members protruding rearwardly from the rear wall, the hollow structural members being circumferentially interspaced from one another, each hollow structural member having a length extending radially along the rear wall and having an internal conduit extending radially inwardly along the length, between a conduit inlet in fluid communication with the diffuser outlet and a conduit outlet located radially inwardly from the conduit inlet.

<FIG> illustrates an aircraft engine <NUM> of a type preferably provided for use in subsonic flight, generally comprising, in sequential flow communication, an intake, a compressor section <NUM>, a combustion engine <NUM> in which compressed air is mixed with fuel and ignited delivering power and exhaust gasses, and a gas turbine <NUM>. In the illustrated embodiment, the combustion engine <NUM> can have one or more combustion engine units such as piston engine units, and/or Wankel engine units for instance.

In this embodiment, a compressor section <NUM> is also provided. The compressor section <NUM> is a centrifugal compressor and can be used to boost the pressure of air from the environment in order to feed higher pressure air to the intake of the combustion engine <NUM>. More specifically, compressed air can be collected from the compressor section <NUM> by a compressed air pipe, such as via a suitable collector <NUM> (e.g. a helical scroll) for instance, and fed to the combustion engine <NUM>, optionally via an intake manifold <NUM>. The compressor section <NUM> can be powered by the gas turbine <NUM>, by the combustion engine <NUM>, and/or by an auxiliary electric engine, to name some examples.

Most of the compressed gas from the compressor section <NUM> can be conveyed to a combustor, such as combustion engine units, or the like where its temperature and pressure can be further increased by the energy of combusting fuel, but a portion of the compressed gas may be bled along an auxiliary pressurized gas passage <NUM> and used for other uses, such as supplying pressure to a bearing seal <NUM> or limiting exhaust gas ingestion across a gap <NUM> between stator and rotor elements of a gas turbine <NUM> for instance.

In the illustrated embodiment, the exhaust gasses are collected from the combustion engine <NUM> and directed to a gas turbine <NUM>. The gas turbine <NUM> can convert energy in the form of heat, pressure and/or velocity of the exhaust gasses into angular velocity of a rotor <NUM>, and the rotor <NUM> can be used to direct power to one or more other device, such as a compressor section <NUM>, a propulsor <NUM> (e.g. propeller, fan), and/or an electric machine acting as a generator. The transfer of power can be direct, or via a clutch and/or a gearbox.

The exhaust gasses can be collected from one or more exhaust gas outlet of the combustion engine <NUM> via an exhaust conduit <NUM> such as an exhaust pipe, optionally via an exhaust manifold <NUM> which connects an exhaust pipe to individual engine units. The exhaust conduit <NUM> can be straight, continuously curved, or made of straight sections interconnected via one or more elbows, to name some examples. The exhaust conduit <NUM> can provide a linear flow of exhaust gasses, whereas the gas turbine <NUM> can be configured for receiving an annular stream of exhaust gasses. A gas turbine intake <NUM> can be provided for connecting the exhaust conduit <NUM> to the gas turbine <NUM>. The gas turbine intake <NUM> can be configured for receiving the linear flow of exhaust gasses from the exhaust conduit <NUM>, distributing it circumferentially, re-orienting its velocity from a circumferential to an axial orientation, and feeding it as an axially-oriented annular stream to the gas turbine <NUM>. The turbine is optional.

It will be noted that the embodiment presented in <FIG> is provided solely to present one possible example embodiment. Other embodiments than the embodiment illustrated in <FIG> can integrate a centrifugal compressor stage, as known in the art, such as turbofan engines, turboprop engines and turboshaft engines, to name some additional examples.

An embodiment of a compressor section is presented in <FIG>. In this embodiment, the compressor section <NUM> has a centrifugal impeller <NUM> integrated to a rotor <NUM>. The rotor <NUM> can be rotatably mounted within non-rotary portions of an aircraft engine <NUM> via bearings <NUM>, for rotation around an axis <NUM>. For the purpose of providing relative references, the axis <NUM> will be said to extend between a front and a rear, and is used as a reference to define axial (along the axis), radial (transversally away or towards the axis), and circumferential (around the axis) orientations.

The centrifugal impeller <NUM> has a plurality of blades <NUM> rooted to a hub <NUM>. The blades <NUM> extend along a compressor flow path which extends between a compressor inlet <NUM> and a compressor outlet <NUM>. The blades <NUM> are circumferentially interspaced from one another. The blades <NUM> not only curve from axial to radial but typically also twist circumferentially around the axis <NUM> to a certain degree, as known in the art. The hub <NUM> extends from an axially oriented tip to a radially oriented tip. The portion of the hub <NUM> leading to the radially oriented tip is sometimes referred to as a back plate, with reference to the rear direction introduced above. The compressor flow path extends between a curved face of the hub <NUM> and a shroud <NUM>, and tapers between the compressor inlet <NUM> and the compressor outlet <NUM>. The compressor flow path can be said to be formed of a plurality of circumferentially interspaced segments each defined between a corresponding pair of blades <NUM>.

The compressor section <NUM> further has a diffuser <NUM>. The diffuser <NUM> has a diffusion flow path <NUM> extending radially between a diffuser inlet <NUM> and a diffuser outlet <NUM>. The diffuser inlet <NUM> is in fluid flow communication with the compressor outlet <NUM>. The diffusion flow path <NUM> is positioned, in the axial orientation, between a rear wall <NUM> and a front wall <NUM>. The diffuser <NUM> can have a plurality of diffuser vanes <NUM> operable to more efficiently convert kinetic energy of the gasses at the compressor outlet <NUM> into pressure at the collector <NUM> than if vanes <NUM> were not used. The diffuser vanes <NUM> can be circumferentially interspaced from one another relative the axis and each bridge, in the axial orientation, the front wall <NUM> to the rear wall <NUM>, and the vanes <NUM> can be wedged, as known in the art. The diffusion flow path <NUM> can be said to be formed of a plurality of diffusion flow passages with each diffusion flow passage extending circumferentially between a corresponding pair of vanes <NUM>. In an embodiment, the front wall <NUM>, the rear wall <NUM>, and the vanes <NUM> can all be integral to one another and form part of a component which can be referred to as a diffuser core, and is provided as a monolithic component in this embodiment, though it will be understood that this is optional and other configurations are possible.

The compressor section <NUM> further has a collector <NUM>. The collector <NUM> extends circumferentially around the axis <NUM>, and can be said to define a circumferential flow path in this embodiment.

The collector <NUM> has an internal volume in fluid communication with the diffuser outlet <NUM> at a collector inlet, and a collector outlet (not shown). The collector <NUM> can be in the form of a plenum or of a volute or scroll, for instance. In the case of a scroll, the cross-sectional area of the internal volume of the collector <NUM>, taken in a plane extending both axially and radially (e.g. such as shown in <FIG>, later referred to as a radial-axial cross-sectional area), can progressively increase along the circumferential orientation and terminate at a tangential outlet, as known in the art.

The pressure can be relatively high in the diffusion flow path <NUM>, and this pressure can exert mechanical stress at the rear wall <NUM>. One way to address structural resistance to the pressure is to thicken the rear wall <NUM>, but it will be understood that this can lead to a significant weight penalty. In the illustrated embodiment, another strategy is used at the rear wall <NUM> to address the structural resistance to the pressure in the diffusion flow path <NUM>.

As perhaps best seen in <FIG>, the compressor section <NUM> is provided with a plurality of hollow structural members <NUM> protruding rearwardly from the rear wall <NUM> of the diffuser <NUM>. The hollow structural members <NUM> have a length extending radially along the rear wall <NUM>, and are circumferentially interspaced from one another. The hollow structural members <NUM> provide additional structural resistance to the structure of the rear wall <NUM> at a lower weight penalty compared to the approach of thickening the entirety of the wall evoked above. In this embodiment, the hollow structural members <NUM> extend radially between an inner structural ring <NUM> and an outer structural ring <NUM>, both also protruding rearwardly from the rear wall <NUM>. A plurality of pockets are thus formed between corresponding pairs of hollow structural members <NUM>, between the inner structural ring <NUM> and the outer structural ring <NUM>, the pockets leading to corresponding web portions of the rear wall <NUM>. It will be understood that in alternate embodiments, either one, or both, of the inner structural ring <NUM> and of the outer structural ring <NUM> can be omitted.

As shown in <FIG>, the hollow structural members <NUM> each form, with the rear wall <NUM>, a corresponding hollow structural section. In the embodiment illustrated in <FIG>, the hollow structural section has a rectangular cross-section with rounded internal and external corners, but it will be understood that other cross-sectional shapes are possible in alternate embodiments, such as triangular cross-sections and circular or semi-circular cross-sections for instance, the details of which can be left to the designer in view of a specific embodiment. More specifically, in this embodiment, the hollow structural member <NUM> can generally have a C shape having two legs leading to forward-facing ends and a closed rear, the two forward-facing ends meeting and merging into the rear wall, leaving an internal cavity between the two legs, and between the rear wall and the closed rear.

Referring back to <FIG>, in the illustrated embodiment, the hollow structural members <NUM> are harnessed as fluid passages in addition to being harnessed for structural resistance. The internal cavity is used as an internal conduit <NUM> extending radially inwardly along the length of the hollow structural member <NUM>. The internal conduit <NUM> extends between a conduit inlet <NUM> and a conduit outlet <NUM>. The conduit inlet <NUM> is in fluid flow communication with the diffuser outlet <NUM>. The conduit outlet <NUM> is located radially inwardly relative the conduit inlet <NUM>. The conduit outlet <NUM> can be in fluid flow communication with a cavity <NUM> or plenum formed in casing of the engine, for instance, and which can act as another portion of a pressurized gas passage. The internal conduits <NUM> can form portions of the pressurized gas passage which can lead to bearing seals, such as to pressurize bearing cavities, and/or to gaps between turbine rotor and stator elements, such as to prevent exhaust gas ingestion, and/or to any other area of the engine where pressurized gas can be useful. In the illustrated embodiment, the rear wall <NUM> extends radially inwardly behind a portion of the centrifugal impeller <NUM>, and the conduit outlet <NUM> is at the end of an aperture which leads obliquely into a cavity <NUM>, at an intermediary location along the radial length of the rear wall <NUM>. In other embodiments, the conduit outlet <NUM> can lead farther along the radially inward direction, or the radially inward extension of the rear wall <NUM> behind the centrifugal impeller <NUM> can be absent, to name some other examples.

Referring now to <FIG> and <FIG>, it will be noted that in this embodiment, the conduit inlets <NUM> are provided in the form of radially-outer open ends of the hollow structural members <NUM>, and these radially-outer open ends are open to a gap <NUM> which is in fluid communication with the internal volume of the collector <NUM>, and are thus in fluid flow communication with the diffuser outlet <NUM> via the collector <NUM> and the gap <NUM>. The radially-outer open ends <NUM> are provided across the radially outer structural ring <NUM>. Many other embodiments are possible.

<FIG> present two alternate embodiments of cross-sectional shapes for the hollow structural members <NUM>, <NUM>. In the embodiment presented in <FIG>, the hollow structural member <NUM> has a generally triangular cross-sectional shape. In the embodiment presented in <FIG>, the hollow structural member <NUM> still has a generally triangular cross-sectional shape, but two internal webs <NUM> are provided which extend along the length of the hollow structural members <NUM>, and axially (partially obliquely) between the rear wall <NUM> and the closed rear of the hollow structural member <NUM>. The internal webs <NUM> can delimit three internal cavities, and in this embodiment, only a central one of the three internal cavities may be used as a conduit, for instance.

Claim 1:
A compressor section (<NUM>) comprising :
a centrifugal impeller (<NUM>) operable to rotate around an axis (<NUM>) extending between a front and a rear, the centrifugal impeller (<NUM>) having blades (<NUM>) extending between a compressor inlet (<NUM>) and a compressor outlet (<NUM>), the compressor inlet (<NUM>) oriented towards the front and axially relative the axis (<NUM>), the compressor outlet (<NUM>) oriented radially outwardly relative the axis (<NUM>),
a diffuser (<NUM>) having a diffusion flow path (<NUM>) extending radially between a diffuser inlet (<NUM>) and a diffuser outlet (<NUM>), the diffuser inlet (<NUM>) in fluid flow communication with the compressor outlet (<NUM>), the diffusion flow path (<NUM>) between a rear wall (<NUM>; <NUM>) and a front wall (<NUM>); and
a collector (<NUM>) extending circumferentially around the axis (<NUM>), having a collector inlet in fluid communication with the diffuser outlet (<NUM>), and a collector outlet;
characterized in that the compressor section (<NUM>) further comprises hollow structural members (<NUM>; <NUM>; <NUM>) protruding rearwardly from the rear wall (<NUM>; <NUM>), the hollow structural members (<NUM>; <NUM>; <NUM>) being circumferentially interspaced from one another, each hollow structural member (<NUM>; <NUM>; <NUM>) having a length extending radially along the rear wall (<NUM>; <NUM>) and having an internal conduit (<NUM>) extending radially inwardly along the length, between a conduit inlet (<NUM>) in fluid communication with the diffuser outlet (<NUM>) and a conduit outlet (<NUM>) located radially inwardly from the conduit inlet (<NUM>).