Ricerc@Sapienza

The dynamics and structure of two turbulent H2/air premixed flames, representative of the corrugated flamelet (Case 1) and thin reaction zone (Case 2) regimes, are analyzed and compared, using the computational singular perturbation (CSP) tools, by incorporating the tangential stretch rate (TSR) approach. First, the analysis is applied to a laminar premixed H2/air flame for reference. Then, a two-dimensional (2D) slice of Case 1 is studied at three time steps, followed by the comparison between two representative 2D slices of Case 1 and Case 2, respectively.

Laminar diffusion jet flames are subjected to buoyant instabilities when the Froude number is lower than a critical value. In the present work, a numerical study on syngas laminar jet diffusion flames at elevated pressures (1, 2, 4, 8 and 12 bar) and buoyant instabilities is presented. Since the Reynolds number is kept constant, the velocity and Froude number diminish as pressure is increased. For pressures from 1 to 4 bar the flames display a steady behavior with a progressive reduction of the thickness, while for 8 and 12 bar the flames oscillate and pulsate.

Standard propulsive applications, such as liquid and hybrid rocket engines, are characterized by highly turbulent purely non-premixed flames. Mixing and combustion of propellants occur under severe thermodynamic conditions, and the numerical characterization of such class of devices is made difficult by the highly non linear thermodynamic and transport properties of the reacting mixture. In this framework, reliable simplified/skeletal chemical kinetic mechanisms and accurate calculation of thermochemical properties, are required for high fidelity simulations.

The causal link between ambient PM2.5 and adverse health effects is still not clear enough, nor it is clear what factors (physical and/or chemical) contribute to PM2.5 toxicity and by what mechanism(s).