Patent Application
20130232949
The present invention relates to gas turbine engines and, more particularly, to nozzles therefor.
A typical gas turbine engine operates in an extremely harsh environment characterized by very high temperatures and vibrations. A conventional gas turbine engine includes a compressor for compressing entering air, a combustor for mixing and burning the compressed gases that emerge from the compressor with fuel, a turbine for expanding the hot gases to generate thrust to propel the engine, and an exhaust nozzle for allowing hot gases to exit the engine. Thus, the exhaust nozzle must accommodate extremely hot gases exiting the engine.
In military operations, design of planes to avoid detection by radar is an important issue. The ability of the plane to remain undetected depends on the overall geometry of the plane and its engine. To minimize detection, it is preferable to minimize the detectability (i.e., the signature) of the engine.
According to an embodiment disclosed herein an apparatus for minimizing signature of an engine having an exhaust gas path and a fan gas path includes a casing, and a liner disposed within the casing. The exhaust gas path passes within the liner and the fan gas path passes between the liner and the casing. The casing is disconnected into an upstream portion and a downstream portion, each portion in registration with the liner, such that there are minimum pressure imbalances caused by the exhaust gas path, the fan gas path and ambient on the downstream portion.
In one example embodiment that includes the elements of the foregoing embodiment, a flexible seal disposed between the upstream portion and the downstream portion.
In another example embodiment that includes the elements of the foregoing embodiment, the casing and the liner comprise an exhaust nozzle.
In another example embodiment that includes the elements of the foregoing embodiment, the casing and the liner further comprise a forward portion and an aft portion wherein a flexible seal is disposed between the casing forward portion and the casing aft portion.
In another example embodiment that includes the elements of the foregoing embodiment, casing and the liner further have a convergent portion disposed between the forward portion and the aft portion.
In another example embodiment that includes the elements of the foregoing embodiment, the flexible seal is disposed within the casing divergent portion.
In another example embodiment that includes the elements of the foregoing embodiment, there are no supports between the upstream segment and the downstream segment.
According to a further embodiment disclosed herein, a nozzle for minimizing signature of a gas turbine engine having an exhaust gas path and a fan gas path, includes a casing and a liner disposed within the casing. The exhaust gas path passes within the liner and the fan gas path passes between the liner and the casing. The casing is disconnected into an upstream portion and a downstream portion, each portion in registration with the liner, such that there are minimum pressure imbalances caused by the exhaust gas path, the fan gas path and ambient on the downstream portion.
In another example embodiment that includes the elements of the foregoing embodiment, a flexible seal disposed between the upstream portion and the downstream portion.
In another example embodiment that includes the elements of the foregoing embodiment, the casing and the liner further comprise a forward portion and an aft portion wherein a flexible seal is disposed between the casing forward portion and the casing aft portion.
In another example embodiment that includes the elements of the foregoing embodiment, the casing and the liner further have a convergent portion disposed between the forward portion and the aft portion.
In another example embodiment that includes the elements of the foregoing embodiment, the flexible seal is disposed within the casing divergent portion.
In another example embodiment that includes the elements of the foregoing embodiment, there are no supports upstream of the flexible seal between the casing and the liner.
In another example embodiment that includes the elements of the foregoing embodiment, there are no supports between the upstream segment and the downstream segment.
According to a further embodiment disclosed herein, a method for designing a nozzle for minimizing signature of a gas turbine engine having an exhaust gas path and a fan gas path, includes the steps of providing a casing, providing a liner disposed within the casing, the exhaust gas path passing within the liner and the fan gas path passing between the liner and the casing, wherein the casing is disconnected into an upstream portion and a downstream portion, each portion in registration with the liner, such that there are minimum pressure imbalances caused by the exhaust gas path, the fan gas path and ambient on the downstream portion.
In another example embodiment that includes the elements of the foregoing embodiment, the method includes providing a flexible seal between the upstream portion and the downstream portion.
In another example embodiment that includes the elements of the foregoing embodiment, determining an inward load on the liner, determining an outward load on the downstream portion, and determining a net of the inward load and the outward load.
In another example embodiment that includes the elements of the foregoing embodiment, the method includes adjusting a length of the downstream portion if the net does not approximate zero.
In another example embodiment that includes the elements of the foregoing embodiment, the method includes adjusting a length of the upstream portion if the net does not approximate zero.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
Referring to
The engine 10 has an exterior casing 22 that extends a length of the engine and an interior casing 24 that encloses the compressor 12, the combustor 14 and the turbine 16. The fan 26 drives a second air flow 28 through an area 30 between the exterior casing 22 and the interior casing 24. A gap 32 exists between the interior casing 24 and a nozzle liner 35. The second air flow 28 flows between the nozzle liner 35 and a case 40 of the exterior casing 22.
Referring now to
Similarly, the exterior case 40 has a cross-portional shape mimicking the shape of the liner 35. The exterior case 40 has a case forward portion 75, a case converging portion 80 and a case aft portion 85 that is approximately in parallel to the case forward portion 75 and disposed radially inwardly thereof. As will be seen infra, this exhaust nozzle 20 flattens so the case aft portion 85 may vary as to its radial relationship with the case forward portion 75 about a perimeter of the nozzle 20. A plurality of supports 90 extend between the liner forward portion 55 and the case forward portion 75, supports 95 extend between the liner converging portion 60 and the case converging portion 80, and supports 100 extend between the liner aft portion 65 and the liner aft portion 85. The supports 90, 95, 100 act to maintain the nozzle liner 35 and exterior case 40 at a roughly equal distance apart.
Referring now to
A flexible seal 405, made of an elastomer reinforced fabric or the like, is disposed between attached to an upstream side 410 and a downstream side of the case converging portion 380. The supports 90 that extend between the liner forward portion 55 and the case forward portion 75 in the prior art are removed. A bumper 415 may be disposed between the case forward portion 375 and the liner forward portion to minimize contact between the parts. The supports 395 upstream of the seal 405 on the case converging portion 380 are also removed.
By separating the case 340 into a first segment 420 upstream of the seal 405 and a second segment 425 downstream of the seal, the second segment 425 is free to move without being affected by the expansion of the first segment 420. Given particular geometries of the liner 335 and the case 340; the relative lengths and circumferences; and the particular pressure differences between the liner 335 and the case 340 regarding the first air flow 318, the second air flow 328 and ambient, the pressure imbalances on the second segment 125 tend to equalize such that the net load results in a liner displacement which meets a pre-determined criteria.
Referring now to
Although a preferred 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.
