Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
Numerical studies of fuel-rich micro combustion: effect of N2 dilution on NOx emissions
Submission Author:
Alexandre Afonso , Portugal
Co-Authors:
Pedro Resende, Carlos Pinho, Mohsen Ayoobi, Alexandre Afonso, Alexandre Afonso
Presenter: Pedro Resende
doi://10.26678/ABCM.COBEM2017.COB17-1830
Abstract
Combustion characteristics at small scales have been studied continuously due to the potential applications in micro devices systems as power supply, because of the high energy density when compared with the typical batteries. It is known that heat release at micro scales result in different flame behavior as compared to conventional scales, leading to several practical limitations in both design and performance. For this reason the study of geometry, mixture stoichiometry, flow rates, wall temperatures are widely studied in literature to better understand the limits of a stable flame. Due to the important role on controlling the flame behavior and subsequent pollutants emissions at micro scales, the dilution effects still needs further studied. In this work the effects of the dilution levels on the combustion characteristics of premixed hydrogen/air, for different equivalence ratios in the fuel-rich regime were studied. More specifically, detailed results obtained for the ignition process, for the flame dynamics and stabilization, and NOx emissions are reported for the different operating conditions. The premixed hydrogen/oxygen and N2 combustion is simulated at an axis-symmetric micro channel (diameter 0.8mm and length 8mm), using detailed chemical kinetics (32 species and 173 reactions). The heat transfer at the wall is considered by imposing a hyperbolic temperature profile, where the wall temperature increases from 300 K at the inlet to 1300 K at 3/8 of channel length, a typical boundary condition used in both experiments and simulation. For all simulations, the inlet mean velocity was 4 m/s, assuming fully developed profile, and a mesh resolution for the computational domain with 30×200 cells. With this setup, a range of equivalence ratios from lower to high flammability limits of hydrogen (φ=1.6 and 6.4) was investigated. For each equivalence ratio, excess dilution (using N2) is gradually increased.
Keywords
Micro combustion, numerical simulations, Hydrogen-rich, NOx emissions
