CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application No. 61/807,359, filed April 2, 2013.

BACKGROUND OF THE INVENTION

[0002] This application relates to a bifurcated inlet for delivering air into a gas turbine engine.

[0003] Gas turbine engines and typically include a compressor compressing air, and delivering it into a combustor. The air is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors, driving them to rotate, and in turn rotate the compressor.

[0004] Miniature gas turbine engines are known and may be defined as engines supplying 180 lbf. of thrust or less, or may also be defined as being of an axial length less than 15 inches (38.1 centimeters). Such miniature gas turbine engines are utilized to power small aircraft, such as drones or missiles.

[0005] Historically, a miniature gas turbine engine is mounted within a fuselage of the aircraft. A single scoop inlet in the fuselage delivered air into a compressor section. More recently, it has been proposed to have a bifurcated inlet, having two scoop inlets through the housing. In the known aircraft, there are two separate flow paths leading from the two scoop inlets, and reaching a duct that combines the flow into a single cylindrical flow before it reaches the engine.

[0006] This has sometimes resulted in an unduly long space required on the aircraft for mounting the engine.

SUMMARY

[0007] In a featured embodiment, a gas turbine engine has a nose cone including a nose cone upstream end. An inlet housing includes a plurality of separate flow paths at a housing upstream end, which is downstream of the nose cone upstream end. The inlet housing includes a mixing portion downstream of the housing upstream end, which mixes airflow from separate flow paths. A rotor and a turbine drive a shaft to drive the rotor. The shaft includes a bearing mounted at a location downstream of the nose cone upstream end. The airflow generally surrounds 360 degrees of a rotational axis of the gas turbine engine.

[0008] In another embodiment according to the previous embodiment, the gas turbine engine is a miniature gas turbine engine.

[0009] In another embodiment according to any of the previous embodiments, the gas turbine engine delivers less than or equal to 180 lbf . of thrust.

[0010] In another embodiment according to any of the previous embodiments, the gas turbine engine is of an axial length less than 15 inches (38.1 centimeters) in length from the upstream end to a downstream end.

[0011] In another embodiment according to any of the previous embodiments, there are two of the plurality of separate flow paths.

[0012] In another embodiment according to any of the previous embodiments, the inlet housing defines two spaced flow areas to separate the separate flow paths. The flow areas have semi-cylindrical radially inner boundaries and generally rectangular radially outer boundaries. Two spaced flow areas are separated by webs, which support the bearing within an outer housing portion.

[0013] In another featured embodiment, an aircraft has a fuselage including at least two scoop inlets for delivering inlet air to an included gas turbine engine. The gas turbine engine includes a nose cone including a nose cone upstream end. The inlet housing includes at least two separate flow paths at a housing upstream end which is downstream of the nose cone upstream end. The inlet housing includes a mixing portion downstream of the housing upstream end which mixes airflow from the separate flow paths. A rotor and a turbine drive a shaft to drive the rotor. The shaft includes a bearing mounted at a location downstream of the nose cone upstream end. The airflow generally surrounds 360 degrees of a rotational axis of the gas turbine engine.

[0014] In another embodiment according to the previous embodiment, the gas turbine engine is a miniature gas turbine engine.

[0015] In another embodiment according to any of the previous embodiments, the gas turbine engine delivers less than or equal to 180 lbf. of thrust.

[0016] In another embodiment according to any of the previous embodiments, the gas turbine engine is of an axial length less than 15 inches (38.1 centimeters) in length from the upstream end to a downstream end. [0017] In another embodiment according to any of the previous embodiments, there are two of the plurality of separate flow paths.

[0018] In another embodiment according to any of the previous embodiments, the inlet housing defines two spaced flow areas to separate the separate flow paths. The flow areas have semi-cylindrical radially inner boundaries and generally rectangular radially outer boundaries. The two spaced flow areas are separated by webs which support the bearing within the outer housing portion.

[0019] These and other features may be best understood from the following drawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 shows a prior art aircraft.

[0021] Figure 2 shows a prior art inlet arrangement.

[0022] Figure 3 shows an inlet arrangement according to an embodiment.

[0023] Figure 4 is a cross-sectional view through an engine and aircraft, in embodiment.

[0024] Figure 5A shows one portion of an inlet housing, according to embodiment.

[0025] Figure 5B shows another view of the Figure 5A inlet, according to embodiment.

DETAILED DESCRIPTION

[0026] An aircraft 20 is illustrated in Figure 1 and includes an aircraft body or fuselage 22, and aerodynamic guide structures, such as wings 24 and tail 25. A payload 126 is included on the vehicle 20 and may be a missile or communication equipment, such as may be utilized on an unmanned drone. In the prior art Figure 1 , there was one scoop inlet 28. An engine 26 may be a miniature gas turbine engine, and scoop inlet 28 extends through the fuselage 22 to deliver air to the engine 26. A nozzle 130 is downstream of engine 26.

[0027] A miniature gas turbine engine may be defined as an engine delivering less than or equal to 180 lbf. of thrust, and/or it may also be defined as being of an axial length less than 15 inches (38.1 centimeters) in length from an upstream end of the engine to a downstream end. While the teachings of the disclosure extend to any gas turbine engine application, it has particular value for a miniature gas turbine engine.

[0028] As shown in Figure 2 in another prior art aircraft 11 , there were two scoop inlets 42 through the fuselage 22 delivering air to an engine 30. The engine 30 has a nose cone 46 defining an upstream end 99 of the engine 30. The two scoop inlets 42 deliver air downstream to merge into a common cylindrical airflow path at 44, at a location upstream of upstream end 99 of the nose cone 46. Thus, when the airflow reached an inlet 48 to the engine 30, the airflow was already across a full 360 degree area about an engine rotational axis Z.

[0029] This has sometimes resulted in the requirement for a long axial length for the aircraft 11 to receive or mount engine 30.

[0030] Figure 3 shows the disclosed engine 100 mounted within the fuselage 22 of an aircraft 13. As shown, the nose cone 104 has an upstream end at Xi. The airflow from the scoop inlets 102 reaches a location X ₂ downstream of the upstream end of the nose cone 104, and is still separate. Location X ₂ is the inlet to the engine 100. An inlet housing 106 has an upstream end 210 downstream of the upstream end Xi to define the inlet to the engine 100. The inlet housing 106 mixes the flow from the two separate flows into a common flow over 360 degrees about an engine rotational axis Y.

[0031] The novel inlet housing 106 results in an aircraft 13 that requires a shorter overall length to mount the engine 100. Said another way, the distance from the scoop inlets 142 to engine 100 is shorter than between the Figure 2 prior art scoop inlets 42 and engine 30.

[0032] Figure 4 shows the fuselage 22 and the engine 100 somewhat schematically. The inlet housing 106 is positioned upstream of a first rotor stage 108. The first rotor or impeller 108 is driven by a shaft 116. The engine 100 may include a compressor section 110 delivering compressed air into a combustor section 112, and products of the combustion pass downstream over a turbine rotor 114. The turbine rotor 114 will drive the shaft 116 to rotate the rotor 108 and rotors in the compressor 110.

[0033] As shown, a bearing 105 mounts shaft 116 adjacent to the nose cone 104.

[0034] As shown in Figure 5A, the nose cone 104 extends from upstream end Xi, which is upstream of the bearing 105. The inlet housing 106 has a full flow portion 111 which extends about 360 degrees around axis Y and is reached by the airflow prior to the airflow reaching the rotor 108 (see Figure 4).

[0035] As shown in Figure 5B, the inlet housing 106 has separate inlet flow areas 120, each to be associated with one of the scoop inlets 102, and downstream of the upstream end Xi of the nose cone 104. Thus, when the air reaches the inlet housing 106, it is still maintained as two separate airflows.

[0036] As can be seen in Figure 5 A, the full flow portion 111 is spaced downstream and serves to mix the air such that when the air reaches the impeller 108, it will be a full flow around 360 degrees about axis Y.

[0037] Stated another way, the airflow within the engine 100 is maintained as two separate circumferentially spaced airflows 120, separated by housing portions or webs 122. Downstream of the upstream end 210 of inlet housing 106, the airflows mix, such that the airflow is generally about 360 degrees about a rotational axis Y of the engine 100. Of course, various struts may be placed within the airflow, such as shown schematically at 113 in Figure 5B, so that the airflow is not necessarily completely over 360 degrees. However, the air from the two separate airflows 120 does not mix until reaching the area 111, within the inlet housing 106 and at a location downstream of the point Xi.

[0038] The inlet housing 60 defines two spaced flow areas 120, with semi- cylindrical radially inner portions 300 and generally rectangular outer portions 301. Of course, other shapes may be used. The two spaced flow areas are separated by webs 122 that support a bearing (105, see Figure 4) within an outer housing portion 305.

[0039] Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.