Moving blade for a high pressure turbine, the blade having a trailing edge of improved thermal behavior

Abstract

A moving blade for a high pressure turbine of a turbomachine, the blade having at least one cooling circuit comprising at least one cavity extending radially between a tip and a base of the blade, at least one air admission opening at a radial end of the cavity(ies) to feed the cooling circuit(s) with cooing air, and a plurality of slots opening out into the cavity(ies) and opening out into the concave side of the blade between the base and the tip of the blade in a manner that is substantially perpendicular to a longitudinal axis of the blade, a connection zone being provided between a slot closest to the base of the blade and a top surface of a platform defining an inside wall for a stream of combustion gas flowing through the high pressure turbine, and the moving blade further comprising an additional cooling air exhaust slot opening out into said cavity and opening out into said connection zone in line with the trailing edge.

Description

[0001] The present invention relates to the general field of moving blades for a high pressure turbine in a turbomachine, and more particularly it relates to slots for exhausting cooling air from the moving blades of a high pressure turbine.[0002] In conventional manner, a turbomachine has a combustion chamber in which air and fuel are mixed together prior to being burned therein. The gas that results from this combustion flows downstream in the combustion chamber and then feeds a high pressure turbine. The high pressure turbine has one or more rows of moving blades that are circumferentially spaced apart all around the rotor of the turbine. The moving blades of the high pressure turbine are thus subjected to the very high temperatures of the combustion gases. These temperatures reach values that are well above those that can be withstood without damage by the blades which are in contact with said gases, and as a result their lifetime is limited.[0003] In order to solve this problem...

AI Technical Summary

Benefits of technology

[0006] The present invention thus seeks to mitigate that drawback by proposing a moving blade for a high pressure turbine that presents a novel shape that avoids cracking. The invention also seeks to avoid degrading the general mechanical strength of the blade, which is a part that is subjected to very high levels of mechanical stress. Finally, the invention also seeks to provide a high pressure turbine for a turbomachine, which turbine is equipped with such moving blades having improved thermal behavior.

[0008] As a result, the cooling air exhausted via said additional slot is guided to the vicinity of the trailing edge over the entire surface of the connection zone so as to avoid cracks appearing therein. This particular shape for the blade base makes it possible to lower the local temperature in said zone by about 10% while conserving the aerodynamic performance obtained by having exhaust slots in the concave side. Under such circumstances, it is no longer necessary for the closest slot of the blade to present dimensions that are greater than those of the other slots since it is now the additional slot which is subjected to the pressure effects due to casting the metal. In addition, because the closest slot has been returned to normal dimensions, the problem posed by cooling air being deflected by centrifugal force is eliminated and the resulting losses in terms of flow rate are therefore reduced. Finally, the ability of the blade to withstand the various mechanical stresses to which it is subjected is not degraded by this special shape.

Problems solved by technology

These temperatures reach values that are well above those that can be withstood without damage by the blades which are in contact with said gases, and as a result their lifetime is limited.

Unfortunately, in practice, the connection zone situated between the slot and the platform supporting the blade is very poorly cooled, particularly since the air exhausted via the slot tends to be deflected towards the tip of the blade because of the large dimensions of the slot and because of the centrifugal force generated by the blade rotating.

This gives rise to large temperature gradients in the trailing edge which, by conduction, give rise to cracking in the vicinity of the connection zone, which cracking is particularly harmful for the lifetime of the blade.

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