The invention relates to a turbine ring assembly for a turbine engine, the assembly comprising a plurality of ring sectors, each made of a single piece of ceramic matrix composite (CMC) material, together with a ring support structure.
The field of application of the invention is in particular that of gas turbine aeroengines. Nevertheless, the invention is applicable to other turbine engines, for example industrial turbines.
In gas turbine aeroengines, improving efficiency and reducing polluting emissions lead to reducing the weight of parts constituting the engine and to operating at ever-higher temperatures.
Ceramic matrix composite (CMC) materials are known for their good mechanical properties, which make them suitable for constituting structural elements, and they are also known for conserving those properties at high temperatures, thus constituting a viable alternative to the traditional use of metal to make parts.
The use of CMC parts in the hot portions of such engines has already been envisaged, for the above-mentioned reasons.
In particular, Document WO 2010/103213 discloses a turbine ring assembly for a turbine engine that comprises a plurality of ring sectors, each made of a single piece of CMC, each ring sector having a first portion forming an annular base with an inside face defining the inside face of the turbine ring and an outside face from which there extend two tab-forming portions having their ends engaged in housings in the ring support structure, the ring sectors possessing a section that is substantially π-shaped, and the ends of the tabs are held without radial clearance by the ring support structure.
In that document, the ring support structure is made of metal and is close to the flow passage for hot gas so that it is subjected to a considerable temperature rise. The metal structures are thus in a danger of being damaged by the high temperature of the gas in the passage.
Furthermore, CMC ring sectors can accept only very low levels of stress, they have high stiffness, and they expand much less than the metal ring support structure. Consequently, since according to the above-mentioned document the ring sectors are held without radial clearance, if ever they are subjected to very high temperatures they are weakened as a result of the mechanical stresses imposed by the differential expansion relative to the ring support structure.