Deposition of small particles from turbulent flows

This paper deals with particle deposition onto solid walls from turbulent flows. The aim of the study is to model particle deposition in industrial flows, such as the one in gas turbines. The numerical study has been carried out with a two fluid approach. The possible contribution to the deposition from Brownian diffusion, turbulent diffusion and shear-induced lift force are considered in the study. Three types of turbulent two-phase flows have been studied: turbulent channel flow, turbulent flow in a bent duct and turbulent flow in a turbine blade cascade. In the turbulent channel flow case, the numerical results from a two-dimensional code show good agreement with numerical and experimental results from other resources. Deposition problem in a bent duct flow is introduced to study the effect of curvature. Finally, the deposition of small particles on a cascade of turbine blades is simulated. The results show that the current two fluid models are capable of predicting particle deposition rates in complex industrial flows.

Autoignition of monodisperse biodiesel and diesel sprays in turbulent flows

A new experimental configuration has been developed to examine the effects of flow on the autoignition of dilute diesel and biodiesel sprays, where the spray is injected in the form of monodisperse individual droplets at right angles to a hot air turbulent flow. The ignition location has been measured by monitoring the OH * chemiluminescence. A qualitative comparison of the flame behaviour between ethanol, acetone, heptane and biodiesel as fuels has also been carried out. With decreasing volatility of the fuel, the flame showed progressively a higher number of individual droplets burning, with the first autoignition spots appearing at random locations but in general earlier than the intense droplet-flame emission. The time-averaged autoignition length increased with increasing air velocity and with increasing intensity of the turbulence, while it decreased with the temperature and the droplet size. The data can be used for validating models for two-phase turbulent combustion. © 2012 Elsevier Inc.