Adhesion of volcanic ash particles under controlled conditions and implications for their deposition in gas turbines

A particular (representative) type of ash has been used in this study, having a particle size range of ~10-70 µm. Experimental particle adhesion rate data are considered in conjunction with CFD modeling of particle velocities and temperatures. This ash becomes soft above ~700˚C and it has been confirmed that a sharp increase is observed in the likelihood of adhesion as particle temperatures move into this range. Particle size is important and those in the approximate range 10-30 µm are most likely to adhere. This corresponds fairly closely with the size range that is most likely to enter a combustion chamber and turbine.This work forms part of a research programme funded by EPSRC (EP/K027530/1). In conjunction with this project, a consortium of partners has been set up under the PROVIDA ("PROtection against Volcanic ash Induced Damage in Aeroengines") banner and information about its operation is available at http://www.ccg.msm.cam.ac.uk/initiatives/provida. The invaluable assistance of Kevin Roberts (Materials Department in Cambridge) with operation of the plasma spray facility is gratefully acknowledged. The authors are also grateful to Dr. Margaret Hartley, of the University of Manchester, for kindly collecting the Laki ash (and several other types) during field trips to Iceland, which were funded by EasyJet.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/adem.201500371 In compliance with current EPSRC requirements, input data for the modelling described in this paper, including meshing and boundary condition specifications, are available at the following URL: www.ccg.msm.cam.ac.uk/publications/resources. These files can be downloaded and used in COMSOL Multiphysics packages. Data supplied are for a representative case

LPCVD Pyrocarbon Coating on Unidirectional Carbon Fiber Yarns : an Efficient Interphase for Aluminium Matrix Composites

In order to optimize the interfaces in carbon fiber (high resistance Toray T800) reinforced aluminium matrix composites, a pyrolytic carbon (Cp) layer has been developed by a CVD process using a hot wall reactor operating at reduced pressure. The Cp, which has a weak shear strength, is introduced to promote adequate debonding at the fiber/matrix interface. In a first step, classical CVD studies are conducted on planar carbon substrates with a parametric investigation of the effects of temperature, pressure, reactant flow rates on the growth rate and morphology of the coating. For Cp, obtained form thermal decomposition of ethylene, a very high activation energy (310 kJ/mol) and a decrease in coating growth rate with the reactant residence time indicate that the reaction limiting step occurs in the gaseous phase. The carbon coatings exhibit a macroscopic stratified morphology which could promote internal delamination. In a second step, deposition parameters have been optimized to ensure a good infiltration of 6000 filaments yarns. Finally, the influence of carbon underlayer on the mechanical properties of coated fibers is determined by tensile tests on monofilaments and interpreted in terms of Weibull distribution. The results on aluminium composites confirm the beneficial role of mechanical fuse played by the Cp coating

Hi-Nicalon Reinforced Silicon Nitride Matrix Composites

The present paper reports on the fabrication and the mechanical properties of SiC (Hi-Nicalon) fibre-reinforced Si3Nu matrix composites. The composite was fabricated by liquid infiltration of an aqueous Si3N4 slurry followed by hot-pressing. The effect of fibre pre-coating with a 400 nm thick pyrolitic carbon layer was investigated. The fibre coating was found to have a significant effect on the frictional stress of the fibre-matrix interface and consequently on the fracture behaviour of the composite.JRC.(IAM)-Institute For Advanced Material

A single fibre test technique for titanium MMC's

Extrait de : Proceedings of the meeting 'Test techniques for metal matrix composites', London (UK), November 28, 1991. Published in Institute of physics short meetings series No 28SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1991 n.225 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Influence of the microstructure of the pyrocarbon coating on the mechanical properties of a SiC/Ti-6242 composite

Communication to : MMC VIII (Metallic composites + foams), Londres (Grande Bretagne), 26-27 novembre 2001SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2002 n.121 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc