Revue de prescription des tests QuantiFERON® au CHU de Nantes en 2009

Abstract

Results are given of experiments carried out on a test rig which has been developed to produce damage of a type similar to that found in the nozzles of rocket motors. The experiments were, in the main, concerned with the erosive action of abrasive particles carried by the gas stream, although ablation effects at the nozzle wall due to wall heating were also investigated. The results indicated that the degree and pattern of damage within a nozzle of a given material depended on (a) the particle velocity, (b) the particle flow pattern, (c) the particle distribution in the flow area and (d) the size and type of the particles. The angle of attack of the particle stream on the wall is an important factor in erosion. For hard brittle substances maximum damage occurs with normal impact, whereas with ductile materials maximum erosion takes place when the angle of attack is small. This angle for maximum erosion appears to depend only on the physical properties of the material under attack. Experimental data are given showing that high local temperatures are induced in the surface layers of the material under attack. For a given size of particle it was found that the particle velocity in the nozzle efflux remained virtually constant as the ratio of particle mass flow rate to air mass flow rate was increased up to a certain critical value. Beyond this value particle velocity and erosion damage decreased. During the tests it was observed that for all particles used the particle velocity in the nozzle efflux was very much less than the theoretical efflux velocity of the unladen air stream.