Metering sheet and iso-grid arrangement for a non axi-symmetric shaped cooling liner within a gas turbine engine exhaust duct

#The present invention relates to gas turbine engines having a dual wall cooling liner, and more particularly to an exhaust duct cooling liner for a non-axi symmetric cooling liner.

#In order to improve gas turbine engine operation and performance, the usage of exhaust duct cooling air is carefully rationed. The cooling air is generally extracted from the engine fan flow, this extracted cooling air is a penalty to the overall performance of the engine. In current gas turbine engine exhaust ducts, a liner is disposed between the engine's working medium (exhaust gas path) and the engine outer casing or vehicle exhaust duct. Cooling air typically extracted from the engine's compressor is flowed within the liner and duct then discharged over the nozzle located at the end of the exhaust duct. A relatively significant quantity of cooling air is required to properly cool the exhaust duct and to maintain a positive pressure within the cooling liner while being subjected to large core pressure gradients at various operating conditions.

#Advanced gas turbine engine exhaust systems are tending toward non axi-symmetric shapes. These shapes advantageously facilitate low observability and vectoring capabilities but generate a non-uniform core pressure field on the cooling liner. As the liner is film cooled, the non-uniform core pressure distribution posses a relatively significant challenge in the maintenance of a minimum pressure ratio between the local maximum core pressure and the cooling airflow supply pressure so as to prevent the high temperature core gases from being ingested into the liner system. If the cooling supply pressure cannot be spatially adjusted to match the non-uniform core pressure field, a greater quantity of cooling air may be required to achieve the minimum cooling to core pressure ratio than would otherwise be necessary to cool the liner as the cooling airflow is typically baselined for the most adverse pressure gradient during the most adverse operating condition. The non axi-symmetric and non-linear shaped exhaust duct further complicates the consistent preservation of a positive pressure gradient.

#The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

#FIG. 1 is a cross sectional side elevation view of an exhaust system;

#FIG. 2 is a perspective partial phantom view of a cooling liner of an exhaust system;

#FIG. 1 illustrates a sectional view of an exhaust duct assembly 20 for a gas turbine engine (illustrated schematically at E). The exhaust duct assembly 20 is of a non axi-symmetric and non-linear geometry. The exhaust duct assembly 20 includes an annular upstream portion (best seen in FIG. 1) which receives a core combustion gas flow F from the engine E, communicates the core combustion gas flow through a series of non-linear serpentines, then exhausts the core combustion gas flow through a generally rectilinear exhaust nozzle 22 (illustrated schematically).

#A cooling liner 24 (also illustrated in FIG. 2) is mounted within a vehicle structure 25. It should be understood that various mounting arrangements as well as vehicles would benefit from the present invention. The cooling liner 24 preferably includes a liner hot sheet 26 separated from an outer pressure vessel 28 by a multitude of cooling liner stiffeners 30 (also illustrated in FIG. 3).

#Cooling airflow C, such as from an engine compressor or ambient intakes flows through a cooling liner volume 32 defined between the liner hot sheet 26 and the outer pressure vessel 28. The cooling airflow C traversing the volume 32 cools the liner 24 through convection. The cooling airflow is typically sourced from fan bypass airflow and/or other airflow that is different from a core combustion gas airflow.