Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry

Three Dimensional Coupled Simulation of Furnaces and Reactor Tubes for the Thermal Cracking of Hydrocarbons

Thermal cracking of hydrocarbons has gone through a significant evolution over the past 20 years. Improved metallurgical properties together with a better understanding of the chemical aspects have led to new configurations for furnace and reactor, all aiming for high severity cracking. A full 3D CFD model containing transport equations for mass, momentum and energy has been implemented in the software code FLOWSIM, together with the k-epsilon turbulence model. It has been coupled with the appropriate kinetic models (the radical reaction scheme CRACKSIM for the reactor and combustion kinetics for the furnace) and an overall iteration scheme has been developed for a coupled furnace-reactor simulation allowing to simulate industrial units. This approach has been applied for a propane cracking furnace, providing detailed understanding of the transport mechanisms taking place

Three Dimensional Coupled Simulation of Furnaces and Reactor Tubes for the Thermal Cracking of Hydrocarbons Simulation tridimensionnelle et couplée des fours et des tubes de réacteurs pour le craquage thermique des hydrocarbures

Thermal cracking of hydrocarbons has gone through a significant evolution over the past 20 years. Improved metallurgical properties together with a better understanding of the chemical aspects have led to new configurations for furnace and reactor, all aiming for high severity cracking. A full 3D CFD model containing transport equations for mass, momentum and energy has been implemented in the software code FLOWSIM, together with the k-epsilon turbulence model. It has been coupled with the appropriate kinetic models (the radical reaction scheme CRACKSIM for the reactor and combustion kinetics for the furnace) and an overall iteration scheme has been developed for a coupled furnace-reactor simulation allowing to simulate industrial units. This approach has been applied for a propane cracking furnace, providing detailed understanding of the transport mechanisms taking place. Le craquage thermique des hydrocarbures a évolué d'une manière significative au cours des 20 dernières années. Des progrès dans les métallurgies associés à une meilleure compréhension des mécanismes de réaction ont conduit à de nouvelles configurations pour les fours et les réacteurs qui s'orientent toutes vers des conditions de craquage plus sévères. Une modélisation directe et tridimensionnelle comprenant des équations de transport de masse, de moment et d'énergie a été implantée dans le code FLOWSIM, en même temps que le modèle k-epsilon de turbulence. Cette modélisation a été couplée avec les modèles cinétiques appropriés (le schéma CRACKSIM pour les réactions radicalaires dans le réacteur et les cinétiques de combustion dans le four) et un schéma itératif global a été développé pour la simulation couplée four-réacteur permettant de simuler des unités industrielles. Cette approche a été appliquée à un four de craquage pour le propane, apportant une compréhension détaillée des mécanismes de transport qui s'y déroulent

Surface temperature measurement in the medium and long wavelength infrared range on MAST

19th International Conference on Plasma-Surface Interactions in Controlled Fusion Devices (PSI), Univ Calif, Gen Atom, San Diego, CA, MAY 24-28, 2010International audienceExperiments and theoretical investigations of surface temperature measurement in the medium and long wavelength infrared range carried out on MAST show that a nonhomogenous surface temperature distribution due to the surface state (micro-metric hot-spots and/or surface roughness) can lead to a significant difference (up to similar to 40%) between both wavelengths. The over-estimation of the bulk temperature decreases with wavelength and the discrepancy observed on MAST can be reproduced using a hot-spot simulation model, by varying the dust size and the dust coverage such that a coverage of 0.2 parts per thousand with 1 mu m dust size which is consistent with the observations. The over-estimation of the bulk temperature is assessed at medium and long wavelength as a function of dust contribution (coverage/size). The effect is also assessed in different conditions (temperature of the bulk as well as the incident power flux). (C) 2010 Elsevier B.V. All rights reserved