Patent Application
20180149114
Exemplary embodiments of the invention relate to rotary-wing aircraft and, more particularly, to an exhaust system for reducing infrared energy from the engine exhaust of rotary wing aircraft.
The exhaust ducting from a gas turbine engine of a rotary wing aircraft is a source of infrared (IR) energy which may be detected by heat seeking missiles and/or various forms of infrared imaging systems for targeting/tracking purposes. With respect to the former, generally speaking, a heat-seeking missile obtains directional cues from the infrared energy generated by the engine exhaust such that the amount of infrared energy given off is one of the primary determining factors of missile accuracy. Regarding the latter, infrared imaging systems detect and amplify the infrared energy for detection and/or targeting.
Current IR suppression systems are utilized on many rotary wing aircraft to provide IR signature reduction. Generally. IR suppression systems are designed to; reduce the infrared energy below a threshold level of a perceived threat, maintain engine performance, and reduce weight and packaging associated therewith. Other consequences may include reducing system or configuration complexity to reduce fabrication and maintainability costs and reducing the external aerodynamic drag produced by such IR suppressor systems.
According to one embodiment of the invention, an exhaust infrared signature reduction arrangement includes an exhaust duct, a first vane support disposed within the exhaust duct and a second vane support disposed within the exhaust duct downstream from the first vane support. The first vane support and the second vane support are movable between a first configuration and a second configuration.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first vane support and the second vane support are substantially identical.
In addition to one or more of the features described above, or as an alternative, in further embodiments the first vane support includes a first plurality of turning vanes and the second vane support includes a second plurality of turning vanes.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the first vane support and the second vane support are in the first configuration, the first plurality of turning vanes and the second plurality of turning vanes are substantially aligned.
In addition to one or more of the features described above, or as an alternative, in further embodiments in the first configuration an engine exhaust and air mixture are configured to flow linearly through the first vane support and the second vane support.
In addition to one or more of the features described above, or as an alternative, in further embodiments when the first vane support and the second vane support are in the second configuration, the first plurality of turning vanes are staggered relative to the second plurality of turning vanes.
In addition to one or more of the features described above, or as an alternative, in further embodiments in the second configuration, a line of sight through the first vane support and the second vane support is blocked.
In addition to one or more of the features described above, or as an alternative, in further embodiments the exhaust duct includes a plurality of holes formed through a wall of the exhaust duct.
In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a mechanism for selectively controlling a supply of air to the exhaust duct.
In addition to one or more of the features described above, or as an alternative, in further embodiments the mechanism is a fan.
In addition to one or more of the features described above, or as an alternative, in further embodiments the mechanism is operable to actively cool the exhaust duct.
According to another embodiment, an exhaust infrared signature reduction arrangement includes an exhaust duct and a mechanism associated with the exhaust duct operable to control an amount of cooling within the exhaust duct.
In addition to one or more of the features described above, or as an alternative, in further embodiments the cooling generated by the mechanism is directly dependent on an amount of power supplied to the mechanism.
In addition to one or more of the features described above, or as an alternative, in further embodiments in the absence of power being provided to the mechanism, the exhaust duct is passively cooled.
In addition to one or more of the features described above, or as an alternative, in further embodiments the exhaust duct is passively cooled through air inlets.
In addition to one or more of the features described above, or as an alternative, in further embodiments when power is provided to the mechanism, the exhaust duct is actively cooled.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
The dual, counter-rotating, coaxial rotor system 12 includes an upper rotor system and a lower rotor system. Rotor system 12 includes a plurality of rotor blades 20 mounted to a rotor hub 22, 24 for rotation about rotor axis of rotation A. A plurality of the main rotor blades 20 project substantially radially outward from the hubs 22, 24. Any number of blades 20 may be used with the rotor system 12. The rotor system 12 includes a rotor hub fairing 36 generally located between and around the upper and lower rotor systems such that the rotor hubs 22, 24 are at least partially contained therein. The rotor hub fairing 36 provides drag reduction.
A main gearbox 26 may be located above the aircraft cabin 28 and drives the rotor system 12. The translational thrust system 30 may be driven by the same main gearbox 26 which drives the rotor system 12. The main gearbox 26 is driven by one or more engines (illustrated schematically at E).
The translational thrust system 30 may be mounted to the rear of the airframe 14 with a translational thrust axis, T, oriented substantially horizontal and parallel to the aircraft longitudinal axis L to provide thrust for high-speed flight. The translational thrust system 30 includes a pusher propeller 32 mounted at an aerodynamic tail fairing 33. The translational thrust axis, T, corresponds to the axis of rotation of propeller 32. Although a tail mounted translational thrust system 30 is disclosed in this illustrated non-limiting embodiment, it should be understood that any such system or other translational thrust systems may alternatively or additionally be utilized.
Referring to
The exhaust system 40 is disposed in communication with each gas turbine engine E of the aircraft 10. The exhaust system 40 is configured to suppress the IR signature radiating from the high-temperature exhaust generated by the gas turbine engines E. In the context used herein, “suppress” means that the IR signature emanating from the gas turbine engine E after passage through the exhaust system 40 is less than the IR signature of the exhaust gas expelled from the gas turbine engine E.
With reference now to
As best shown in
Immediately adjacent the engine outlet 54, the engine exhaust 42 is configured to mix with cooling air, identified as 58 in
The position of the first vane support 60a relative to the second vane support 60b may be controlled in response to a selected mode of operation. In an embodiment, when a first mode is selected, as shown in
In a second mode of operation, illustrated in
With reference to
One or more mechanisms 70 may be configured to provide a supply of air into the exhaust duct 46 for reducing the temperature of the engine exhaust 42. In an embodiment, as illustrated in
The fans 70 may be operated to control the cooling of the exhaust duct 46. Further, the active cooling of the exhaust duct that occurs in response to the fans is dependent on the amount of power provided to the fans 70. In embodiments where no power is applied to the fans 70, all film cooling of the exhaust duct 46 that occurs is passive and results from the movement of air through the duct 46. When power is supplied to the fans 70, forced air is applied to the exhaust duct 46 at a position generally adjacent each of the fans 70 to actively cool the exhaust duct. Accordingly, the amount of cooling necessary to reduce the IR signature of the exhaust flow must be balanced with the amount of power available for use by the fans 70 in a given scenario or application.
The exhaust system illustrated and described herein allows an operator of the aircraft to balance achieving a lower infrared signature with losses in efficiency without a substantial weight increase to the aircraft.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
