Turbojet engine case, notably intermediate case

Abstract

The present invention relates to an annular case (20) of a multi-flow turbojet engine comprising a first element (22) forming a hub, a second element (24) forming a cylindrical casing, radially on the outside of and concentric with the first element, radial arms (23) connecting the first element (22) to the second element (24), at least part of said arms being structural and having an aerodynamic flow straightener vane profile, characterized in that it comprises a first ring sector (20C) of the case and a second ring sector (20T), the first ring sector being made of composite material and the second ring sector of metal, said radial arms (23T) of the second ring sector (20T) being structural.

Description

[0001]The present invention relates to the field of multi-flow turbojet engines and is aimed more particularly at a case element which is usually termed the intermediate case.PRIOR ART[0002]A multi-flow turbojet engine such as a front fan twin spool turbofan engine comprises an air intake fixed to a fan case itself bolted to the outer shroud of the case known as the intermediate case. The duct downstream of the fan communicates with two concentric ducts: the primary flow duct and the secondary or bypass flow duct. The primary flow duct leads to the compression stages and to the combustion chamber. The latter opens into the flowpath for the hot gases comprising the turbine wheels driving the compressors including the fan rotor. Following expansion, the gases of the primary flow are discharged via a central nozzle. The secondary flow duct which is annularly on the outside of the duct for the primary flow is straightened axially then passes between the arms of the intermediate case bef...

AI Technical Summary

Benefits of technology

The invention aims to improve the weight and aerodynamic efficiency of existing solutions. It does this by concentrating most of the load transmission into the metal part of the second ring sector, and avoiding bolted connections in the first ring sector, which reduces mass.

Problems solved by technology

The problem is therefore that of finding an intermediate case structure that is light enough in weight that it can be incorporated notably by way of intermediate case in a high bypass ratio engine without impairing the specific consumption thereof.

This solution is undesirable for high bypass ratio engines because the structural arms of the intermediate case introduce an aerodynamic pressure drop and thus impair the propulsion efficiency of the engine.

However, despite the presence of the bolts, these vanes cannot be removed without the engine being dismantled from the wing structure of the airplane.

The disadvantage of this solution is that it adds the mass of the bolted connections.

However, this solution would be complicated to produce and it would be difficult to guarantee a quality that was repeatable from one case to another.

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