Patent Description:
Many modern aircraft, as well as other vehicles and industrial processes, employ gas turbine engines for generating energy and propulsion. Such engines include a fan, compressor, combustor and turbine provided in serial fashion and arranged along a central longitudinal axis. Air enters the gas turbine engine through the fan and is pressurized in the compressor. This pressurized air is mixed with fuel in the combustor. The fuel-air mixture is then ignited, generating hot combustion gases that flow downstream to the turbine. The turbine is driven by the exhaust gases and mechanically powers the compressor and fan via a central rotating shaft. Energy from the combustion gases not used by the turbine is discharged through an exhaust nozzle, producing thrust to power the aircraft.

Gas turbine engines contain an engine core and fan surrounded by a fan case, forming part of a nacelle. The nacelle is a housing that contains the engine. The fan is positioned forward of the engine core and within the fan case. The engine core is surrounded by an engine core cowl and the area between the nacelle and the engine core cowl is functionally defined as a bypass duct. The bypass duct is substantially annular in shape to accommodate the airflow from the fan and around the engine core cowl. The airflow through the bypass duct, known as bypass air, travels the length of the bypass duct and exits at the aft end of the bypass duct at an exhaust nozzle.

In addition to thrust generated by combustion gasses, the fan of gas turbine engines also produces thrust by accelerating and discharging ambient air through the exhaust nozzle. Various parts of the gas turbine engine generate heat while operating, including the compressor, combustor, turbine, central rotating shaft and fan. To maintain proper operational temperatures, excess heat is often removed from the engine (via oil coolant loops, including air/oil or fuel/oil heat exchangers) and dumped into the bypass duct airflow for removal from the system.

As compressed air travels downstream from the compressor, it passes through a pre-diffuser prior to entering the combustor. The pre-diffuser directs the airflow through passages with expanding areas, slowing the airflow and allowing for a more efficient combustion process. The pre-diffuser may include inner diameter and outer diameter walls connected by a plurality of struts. The passages are defined by the walls and struts.

As the gas turbine engine operates, various components may absorb different amounts of heat energy. This absorption, along with part location, build loading and part material, may cause different degrees of thermal expansion. This thermal expansion may cause stresses on certain gas turbine engine parts or locations, such as the leading edge of a strut, or the junction between a strut and an inner or outer diameter wall. Prior strut arrangements can adversely localize strains or hinder air flow through the passages.

Accordingly, there is a need for an improved pre-diffuser strut for a gas turbine engine. <CIT> discloses a gas turbine diffuser having strut sections inclined to the flow direction. Other examples of stationary vanes are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Viewed from one aspect the present invention provides a pre-diffuser of a gas turbine engine according to claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the upper contour may include more than two radii.

In a further embodiment of any of the foregoing embodiments, the strut may be made of a nickel alloy.

In a further embodiment of any of the foregoing embodiments, the strut may be made of Inconel <NUM>™.

In a further embodiment of any of the foregoing embodiments, the strut may be a casting.

In a further embodiment of any of the foregoing embodiments, the strut may be machined.

In an embodiment, the present invention also provides a gas turbine engine according to claim <NUM>.

Viewed from another aspect the invention provides a method of forming a pre-diffuser of a gas turbine engine according to claim <NUM>.

These, and other aspects and features of the present disclosure, will be better understood upon reading the following detailed description when taken in conjunction with the accompanying drawings.

For further understanding of the disclosed concepts and embodiments, reference may be made to the following detailed description, read in connection with the drawings, wherein like elements are numbered alike, and in which:.

It is to be noted that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting with respect to the scope of the claims. Rather, the concepts of the present disclosure may apply within other equally effective embodiments. Moreover, the drawings are not necessarily to scale, emphasis generally being placed upon illustrating the principles of certain embodiments.

Turning now to the drawings, and with specific reference to <FIG>, a gas turbine engine constructed in accordance with the present disclosure is generally referred to by reference numeral <NUM>. The gas turbine engine <NUM> includes a compressor <NUM>, combustor <NUM> and turbine <NUM>, known as the engine core <NUM>, lying along a central longitudinal axis <NUM>, and surrounded by an engine core cowl <NUM>. The compressor <NUM> is connected to the turbine <NUM> via a central rotating shaft <NUM>. Additionally, in a typical multi-spool design, plural turbine <NUM> sections are connected to, and drive, corresponding plural sections of the compressor <NUM> and a fan <NUM> via the central rotating shaft <NUM> and a concentric rotating shaft <NUM>, enabling increased compression efficiency.

As is well known by those skilled in the art, ambient air enters the compressor <NUM> at an inlet <NUM>, is pressurized, and is then directed to the combustor <NUM>, mixed with fuel and combusted. This generates combustion gases that flow downstream to the turbine <NUM>, which extracts kinetic energy from the exhausted combustion gases. The turbine <NUM>, via central rotating shaft <NUM> and concentric rotating shaft <NUM>, drives the compressor <NUM> and the fan <NUM>, which draws in ambient air. Thrust is produced both by ambient air accelerated aft by the fan <NUM> and by exhaust gasses exiting from the engine core <NUM>.

As air enters the compressor <NUM>, it is accelerated aft at high speed and pressure. Prior to reaching a combustor assembly <NUM> and an inner diffuser case <NUM>, as shown in <FIG>, the compressed air passes through a pre-diffuser <NUM>. The pre-diffuser <NUM> may contain passages <NUM> allowing air to flow through to the combustor assembly <NUM>. These passages <NUM>, as further shown in <FIG>, include expanding areas to slow the airflow from the compressor <NUM> and allow a more efficient combustion in the combustor assembly <NUM>. One or more struts <NUM> may be employed for use as structural pre-diffuser <NUM> members and to partition the passages <NUM>.

The pre-diffuser <NUM> may include an inner diameter wall <NUM> and an outer diameter wall <NUM>, as best shown in <FIG>. The inner diameter wall <NUM> and outer diameter wall <NUM> may be connected by a plurality of struts <NUM>. Further, the passages <NUM> may be bounded by the inner and outer diameter walls <NUM>, <NUM> and adjacent struts <NUM>. The forward edge of the strut <NUM> may be defined as the leading edge <NUM>
As the gas turbine engine <NUM> operates, various components may absorb different amounts of heat energy. This absorption, along with part location, build loading and part material, may cause different degrees of thermal expansion. This thermal expansion may cause stresses on certain gas turbine engine <NUM> parts or locations, including the strut <NUM>, leading edge <NUM> or the juncture between the strut <NUM> and the inner or outer diameter wall <NUM>, <NUM>. In conventional pre-diffusers, stresses due to thermal expansion, or other causes, may gradually weaken a part, leading to increased acquisition or maintenance costs, increased repair times or part fatigue.

According to the claimed invention, to improve on prior designs, a strut <NUM> as shown in <FIG> has a leading edge <NUM> with an upper contour <NUM> and a lower contour <NUM>. The upper contour <NUM> has a forward end <NUM> and an aft end <NUM>. As shown, in <FIG> and <FIG>, the upper contour <NUM> may include a first radius <NUM> and a second radius <NUM>. The first and second radii <NUM>, <NUM> are associated with the forward end <NUM> and the aft end <NUM>, respectively. The first radius <NUM> is located farther forward than the second radius <NUM>.

Further, the lower contour <NUM> has a lower contour forward end <NUM> and a lower contour aft end <NUM>, as shown in <FIG>. The lower contour <NUM> has a first lower radius <NUM> and a second lower radius <NUM>. The first and second lower radii <NUM>, <NUM> are associated with the lower contour forward end <NUM> and the lower contour aft end <NUM>, respectively. The first lower radius <NUM> is located farther forward than the second lower radius <NUM>.

The first radius <NUM> is larger than the second radius <NUM>, as best shown in <FIG> and <FIG>. Including the larger first radius <NUM> forward of the smaller second radius <NUM> allows a greater contact area between the outer diameter wall <NUM> and the strut <NUM>. This larger contact area may better disperse loads between the two parts than would a smaller contact area, lessening the strain experienced at a single particular point at the juncture. The use of a larger radius forward and a smaller radius aft allows this larger contact area while minimizing the material used in the part, leading to lower weight, lower costs and increased performance. Further, the more gradual airflow transition from the parallel (with respect to the airflow) outer diameter wall <NUM> to the perpendicular portion of the leading edge <NUM> provided by the larger forward radius smooths the airflow through the passages <NUM> and reduces internal drag losses.

According to the invention, as shown in <FIG>, the lower contour <NUM> may also have a larger and relatively forward first lower radius <NUM> and a smaller and relatively aft second lower radius <NUM>. This arrangement, along the lower contour <NUM>, is conceptually the same as that of the upper contour <NUM> curvature described above. However, in this variant, the transition and contact are between the inner diameter wall <NUM> and the strut <NUM>.

In another embodiment not encompassed by the wording of the claims, the upper contour <NUM> may include more than two radii, as shown in <FIG>. A third radius <NUM> may enable a more finely-tuned design, as the more than two radii may be shaped to more effectively distribute stresses and loads than an upper contour <NUM> with only two radii.

In yet another embodiment not encompassed by the wording of the claims, the upper contour <NUM> may include a constantly decreasing radius <NUM>, as shown in <FIG>. In this embodiment, the upper contour <NUM> may include a non-constant and decreasing radius to distribute stresses and decrease internal aerodynamic drag.

According to the invention, the upper contour <NUM> includes an infinite radius <NUM>, as best shown in <FIG>. The upper contour <NUM> includes a straight and linear section with a radius value equal to infinity.

With respect to materials, the strut <NUM> may be formed from a nickel alloy, although many other materials are possible. With specific reference to nickel alloy, however, the nickel alloy may be Inconel <NUM>™. Further the strut <NUM> may be a casting or a machined part.

A method for forming a strut <NUM> of a gas turbine engine <NUM> not encompassed by the wording of the claims can best be understood by referencing the flowchart in <FIG>. The method may comprise including a pre-diffuser incorporating a strut, the strut may have a leading edge with an upper contour having a forward end and an aft end <NUM>, and shaping the strut such that the forward end has a larger radius than the aft end <NUM>. Further, the leading edge may include a lower contour having a lower contour forward end and a lower contour aft end, the lower contour forward end may have a larger radius than the lower contour aft end <NUM>.

While the present description contains exemplary embodiments, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the scope of the invention as defined by the claims. Further, where these exemplary embodiments (and other related derivations) are described with reference to a certain number of elements it will be understood that other exemplary embodiments may be practiced utilizing either less than or more than the certain number of elements.

In operation, the present disclosure sets forth a pre-diffuser <NUM> which can find industrial applicability in a variety of settings. For example, the disclosure may be advantageously employed in reinforcing various parameters and reducing internal drag characteristics in a gas turbine engine <NUM>.

More specifically, the pre-diffuser <NUM> may include a plurality of struts <NUM>, and each strut may have a leading edge <NUM>. The upper contour <NUM> of the leading edge <NUM> may have a forward end <NUM> and an aft end <NUM>, and may include a first radius <NUM> and a second radius <NUM>. The first and second radii <NUM>, <NUM> may be associated with the forward end <NUM> and the aft end <NUM>, respectively. The first radius <NUM> may also be located farther forward than the second radius <NUM>.

Claim 1:
A pre-diffuser (<NUM>) of a gas turbine engine (<NUM>), comprising:
an air passage (<NUM>) bounded by an inner diameter wall (<NUM>), an outer diameter wall (<NUM>), a first strut (<NUM>) and an annularly adjacent second strut (<NUM>);
each strut (<NUM>) including:
a forward edge defining a leading edge (<NUM>), characterised by:
an upper contour (<NUM>) with an upper contour forward end (<NUM>), which has a larger upper contour first radius (<NUM>), and an upper contour aft end (<NUM>), which has a smaller upper contour second radius (<NUM>) that is smaller than, and located aft of, the larger upper contour first radius (<NUM>), wherein the upper contour (<NUM>) includes a straight and linear section with a radius value equal to infinity;
a lower contour (<NUM>), that differs from the upper contour, with a lower contour forward end (<NUM>), which has a larger lower contour first radius (<NUM>), and a lower contour aft end (<NUM>), which has a smaller lower contour second radius (<NUM>)
that is smaller than, and located aft of, the larger lower contour first radius (<NUM>); wherein both the upper contour (<NUM>) and lower contour (<NUM>) transition from parallel to airflow, to perpendicular to airflow, defining a gradual airflow transition from the parallel, with respect to airflow, outer diameter wall (<NUM>) to the perpendicular portion of the leading edge (<NUM>) provided by the larger upper contour first radius (<NUM>) that smooths an airflow through the air passage (<NUM>) and reduces internal drag losses.