ISSN Online: 2688-7231
ISBN Online: 978-1-56700-478-6
Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017)
CFD STUDIES OF FLAMELESS COMBUSTION
要約
Clean combustion technologies are necessary to be
researched and implemented to address the raising energy
demands and environmental concerns. Flameless combustion
technology is one of such technologies. As the name suggests, no visible or audible flame is observed during flameless operation. Absence of high temperature zones in the combustion chamber and lower adiabatic flame temperatures accounts for reduction in NOx emissions. Flameless combustion is characterized by a Damköhler number of order 1. Reducing the chemical reaction rate and increasing the diffusion (mixing) rate are the two prominent ways of achieving the desired slow turbulence-chemistry interaction (TCI). While higher exhaust gas recirculation (EGR) percentage brings the reaction rates significantly down, increased turbulence improves the diffusion rates. In order to explain the flameless combustion process further, the following hypotheses are proposed that explains the impact of higher EGR on reaction zone: (a) Mass effect - overall combustion temperature reduction due to dilution (b) Thermal effect - auto ignition due to the enthalpy addition to reactants, and (c) Kinetic effect - water and radicals affect auto ignition
mechanism. This paper attempts to verify the above hypothesis by performing Computational Fluid Dynamics (CFD)
simulations of flameless combustion process.