An Efficient CAE Method for the Prediction of the Thermomechanical Stresses during Diesel Particulate Filters Regeneration

The safe soot limit is crucial for the optimization and regeneration management of Diesel Particulate Filters (DPF). Coupled exhaust after-treatment and stress models can largely substitute the ‘inherently’ destructive and cost-intensive experiments with, however, increased time/computational needs. The target of this work is to demonstrate that the role of DPF geometrical and thermomechanical properties on soot mass limit can be analyzed systematically with efficient solvers and advanced meshing methodologies. Application examples for cases of uncontrolled DPF regeneration mode with and without accumulated ash are discussed. The soot limit is not directly correlated with peak temperature as often assumed

CFD-based modelling of the residence time distribution in structured fixed beds

Fixed bed reactors are well known in chemical industry. These reactors are usually modelled using a pseudo-homogeneous approach and experimentally determined correlations. This simplified description does not permit a detailed analysis of the liquid flow between the particles, where local phenomena are particularly important, significantly influencing the overall reactor performance. In this work, complex local flow field patterns in fixed bed reactors are studied. Two different regular arrangements of spheres are investigated using the commercial computational fluid dynamics code CFX by ANSYS Inc. To validate the simulation results, Ergun and Carman pressure drop correlations are used. Numerical simulations are in a good agreement with both correlations. Furthermore, the residence time distribution is estimated using two different methods

Mg-Ti-H thin films as switchable solar absorbers

The reflection and transmission spectra of Pd capped MgyTi1??y thin films (y ¼ 0:7; 0:8 and 0.9) are measured in the 0.5–5.5 eV energy range, both in the as-prepared and hydrogenated states. Upon hydrogenation these films switch reversibly from a shiny metallic state into a ‘‘black’’ absorbing one. The composition and thicknesses can be tailored to achieve high solar absorptance and low thermal emittance in the hydrogenated state. The combination of these two characteristics is interesting for the application of this material as switchable absorber in solar collectors. The use of a MgyTi1??y switchable absorber in solar collectors allows to lower the stagnation temperature from 180 to 80 1C. The collector efficiency is affected only minimally