The present invention generally relates to engine cooling systems, and more particularly relates to engine oil cooling systems for rotorcraft.
Most aircraft engines use oil for lubricating engine components. Heat generated by an aircraft engine is largely absorbed by this oil as it circulates through the engine, and the oil should be cooled, generally, with a cooling system. Conventional cooling systems are relatively complex and may adversely affect the overall efficiency of the engine. Various heat sink sources have been utilized and include fan or compressor bleed air and even engine fuel. Conventional cooling systems may include an air-oil heat exchanger such that air passes through the heat exchanger to cool the oil. Such an oil cooler generally requires a separate air flow feed which directs cooling air from the exterior of the engine to the oil cooler disposed therewithin.
As such, oil cooling systems generally require supplemental cooling air. The source of air commonly used for cooling engine oil is air bled from the initial stages of the compressor of the engine, or, in a turbofan engine, fan air from behind the fan. The air from each of these sources has pressure increased by the compressor or fan, and is thus warmer and consequently a less desirable source of cooling air.
Accordingly, it is desirable to provide improved engine cooling systems. In addition, it is desirable to provide engine cooling systems that do not require supplemental cooling air driven by an auxiliary fan. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
In one exemplary embodiment, a cooling system is provided for an engine of a rotorcraft configured to generate a downwash into an atmosphere during operation. The system includes an inlet coupled to the engine and configured to receive a liquid from the engine; an outlet coupled to the engine and configured to return the liquid to the engine; and a body defining a conduit having a first end coupled to the inlet and a second end coupled to the outlet such that the liquid flows from the inlet to the outlet through the conduit and transfers heat to the atmosphere via the downwash from the rotorcraft.
In another exemplary embodiment, a rotorcraft includes an airframe; a rotor system coupled to the airframe and configured to generate a downwash during operation; an engine assembly configured to power the rotor system, the engine assembly configured to use oil for lubrication; and a cooling system comprising a conduit in flow communication with the engine assembly such that the oil is received by the cooling system, cooled by the cooling system, and returned to the engine assembly, the conduit being in heat transfer communication with the downwash to transfer heat from the oil to the downwash.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
Broadly, exemplary embodiments discussed herein include engine cooling systems for cooling oil from a rotorcraft engine. In particular, the engine cooling systems are arranged on the nacelle of the rotorcraft such that downwash from the rotors during operation may be used to transfer heat from the oil to the atmosphere. The engine cooling system may include a conduit that transports the oil near the surface of the nacelle to improve heat transfer efficiency.
As noted above, in this exemplary embodiment, the engine cooling system 120 receives heated oil from the engine and returns cooled oil to the engine. In particular, the engine cooling system 120 is a heat exchanger that transfers heat from the oil to the atmosphere. Particularly, the position of the engine cooling system 120 on the nacelle 300 exposes the engine cooling system 120 to the downwash 216 and enables a more efficient heat transfer to the atmosphere. The atmosphere generally has a much lower temperature than the heated oil, and the downwash 216 provides fresh air to the engine cooling system 120. The continual supply of cooler air from the atmosphere enables a more efficient heat transfer. In general, the cooling system 120 should be positioned to receive maximum flow from the rotor downwash 216.
The engine cooling system 120 may include surface-increasing devices, such as fins 122, to increase the efficiency of heat transfer. The number, arrangement, shape, and orientation of the fins 122 may be adjusted based on heat transfer efficiency, weight, and aerodynamic considerations. In illustrated exemplary embodiments, the fins 122 are generally perpendicular to the direction of travel and parallel to the general direction of the downwash 216.
The engine cooling system 120 includes a body 124 that defines a conduit 126. In one exemplary embodiment, the body 124 is a plate-like structure that integrally defines the conduit 126. An inlet 128 couples a first end of the conduit 126 to the engine 110 (
The conduit 126 is generally U-shaped and extends the length of the body 124 to maximize the path of the oil within the engine cooling system 120. In further embodiments, the conduit 126 may be serpentine-shaped and traverse the length of the body 124 more than twice to increase cooling time. As noted above, the conduit 126 may be integrally formed with the body 124 to improve heat transfer characteristics. The overall length of the conduit 126 may be dictated by the cooling requirements of the engine oil. Generally, a longer conduit 126 will provide increased cooling.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.