SiC‐Matrix Composites: Nonbrittle Ceramics for Thermo‐Structural Application

Non-oxide ceramic matrix composites are potential candidates to replace the current nickel-based alloys for a variety of high temperature applications in the aerospace field. The durability of a SiC ( f ) /PyC ( i ) /[Si,C,B] ( m ) composite with a sequenced self-sealing matrix and Hi-Nicalon fibers was investigated at 600 °C for exposure durations up to 600 h. The specimens are aged in a variety of slow-flowing air/steam gas mixtures and total pressures, ranging from atmospheric pressure with a 10–50% water vapor content to 1 MPa with 10–20% water vapor content. The degradation of the composite was determined from the measurement of residual strength and strain to failure on post-exposure specimens and correlated with microstructural observations, weight changes and characterizations of the generated oxides. All of the post-exposure characterizations demonstrate the ability of the sequenced [Si,C,B] matrix to protect the PyC interphase from environmental attacks. Two different oxidation modes of the matrix, depending on the total pressure are discussed in terms of the reactivity of the boron-containing layers, and their relative positions in the sequenced matrix. In high pressure environments, a strong localized dissolving of a small amount of SiC fibers in the boria-containing oxide is evidenced at 600 °C.

Self-healing mechanisms of a SiC fiber reinforced multi-layered ceramic matrix composite in high pressure steam environments

A mixer for a turbofan engine (100) includes a centerbody (144) and a mixer nozzle (146). The mixer nozzle (146) surrounds at least a portion of the centerbody (144) and is spaced apart to define a core flow path between the mixer nozzle (146) and the centerbody (144). The mixer nozzle (146) is configured, when bypass air flows through the turbofan engine (100), to direct at least a portion of the bypass air to impinge on the centerbody (144). The mixer nozzle (146) includes a plurality of circumferentially spaced mixer lobes (206) that extend axially in a rearward direction and have a cross-section shape defined by a set of equations.

Turbofan gas turbine engine aerodynamic mixer

Thermostructural composites (TSC) improvement is one of the key factors to ensure future competitiveness of aeronautical and space engines The TSC technology developed in Snecma Propulsion Solide is based on continuous fiber-reinforced composites and carbon or ceramics matrices deposited by chemical vapor infiltration This article presents a status of the latest improvements for cost savings of composite reinforcements (so-called texture) and specific matrices developed to increase both durability and temperature capability of previous ceramic composites, operating in oxidative environments

A Global Approach to Fiber nD Architectures and Self-Sealing Matrices: From Research to Production

An exhaust mixer for a gas turbine engine includes an annular wall having upstream end adapted to be fastened to an engine case and a downstream end forming a plurality of inner and outer mixer lobes A support member interconnects at least a number of the inner lobes, and includes a circumferentially extending stiffener ring located radially inwardly from the inner lobes and a series of circumferentially spaced apart mixer struts radially extending from the inner lobes to the stiffener ring The mixer struts have a radial length at least equal to a width of a main gas path defined between the inner lobes and the exhaust cone such that the mixer struts extend entirely through the main gas path The stiffener ring being fixed solely to the mixer struts such as to float with respect to the exhaust cone and permit relative movement therebetween

Gas turbine engine exhaust mixer

The invention relates to a mixer for a separate-flow nozzle of a turbojet engine, said mixer comprising, following a longitudinal axis (X-X'), a fixing collar (10) for connecting the mixer to the exhaust housing of the nozzle, and a lobe structure (20) comprising a succession of inner lobes (22) and outer lobes (21) which are peripherally distributed about the longitudinal axis (X-X') of the mixer. The lobe structure (20) consists of a ceramic matrix composite material, and comprises a mid-span snubber (30) forming a connection between the inner lobes of the structure. In this way, the main part of the mixer, that is the lobe structure, consists of a ceramic matrix composite material, which enables the mass of the mixer, and thus the nozzle, to be significantly reduced.

Mixer for separate-flow nozzle

The invention relates to an exhaust system (100) for directing the flow from a gas turbine, that comprises a flow directing nozzle and an exhaust casing (110) for connecting the duct nozzle to the outlet of the gas turbine. The duct nozzle includes a primary duct (120) attached to the exhaust casing (110) and a secondary nozzle (130) arranged about the primary nozzle. The exhaust system further includes a means for directly attaching the secondary nozzle (130) to the exhaust casing (110), the secondary nozzle being held by the exhaust casing independently from the primary nozzle (120).

Exhaust system for gas turbine

Mixer for separate-stream nozzle

A new concept of Ceramic Matrix Composite (CMC), mainly based on the use of a self–sealing technology for matrix and the use of a multilayer woven reinforcement, has been developed by Snecma for achieving high performance levels targeted by future jet engines. The driving force for this development has been to increase both lifetime and temperature capability of previous C/SiC and SiC/SiC materials using a monolithic SiC Chemical Vapor Infiltration (CVI) matrix and finishing treatment against oxidation. The first material, which has been developed with this new approach, is CERASEP® A410, using Hi-Nicalon™ fibers from Nippon Carbon. It has been submitted to a comprehensive characterization in order to determine thermo-mechanical properties and to evaluate lifetime duration, using fatigue and creep testing. Further material development is investigating the use of carbon fiber for economical objectives. The combination of such fibers with the new self-sealing matrix is providing promising results for long duration application at high temperature. Such results are permitted by the very high potential of the new matrix.Copyright © 2002 by ASME

An Improved Long Life Duration CMC for Jet Aircraft Engine Applications

Melangeur pour tuyere a flux separes de turboreacteur comprenant, suivant un axe longitudinal (X-X'), une virole de fixation (10) pour raccorder le melangeur au carter d'echappement de la tuyere et une structure a lobes (20) comportant une succession de lobes internes (22) et externes (21) repartis de facon circonferentielle autour de l'axe longitudinal (X-X') du melangeur. La structure a lobes (20) est realisee en materiau composite a matrice ceramique et comprend en outre un anneau raidisseur (30) qui forme une liaison entre les lobes internes de la structure. Ainsi, la majeure partie du melangeur, a savoir la structure a lobes, est realisee en un materiau composite a matrice ceramique, ce qui permet de diminuer de facon significative la masse du melangeur et, par consequent, celle de la tuyere.

Laurent Baroumes

Papers

Mixer for separate-flow nozzle

Exhaust system for gas turbine

Mixer for separate-stream nozzle

An Improved Long Life Duration CMC for Jet Aircraft Engine Applications

Melangeur pour tuyere a flux separes