Open AccessChemical response of methane/air diffusion flames to unsteady strain rate
Author(s) -
Hong G. Im,
Jacqueline H. Chen,
Jyh-Yuan Chen
Publication year - 1998
Language(s) - English
Resource type - Reports
DOI - 10.2172/671890
Subject(s) - methane , mechanics , extinction (optical mineralogy) , strain rate , chemistry , volumetric flow rate , thermodynamics , diffusion , materials science , analytical chemistry (journal) , physics , mineralogy , organic chemistry , chromatography
Effects of unsteady strain rate on the response of methane/air diffusion flames are studied. The authors use the finite-domain opposed flow configuration in which the nozzle exit velocity is imposed as a function of time. The GRI mechanism v2.11 is used for the detailed methane/air chemistry. The response of individual species to monochromatic oscillation in strain rate with various frequencies reveals that the fluctuation of slow species, such as CO and NO{sub x}, is more rapidly suppressed as the flow time scale decreases. It is also observed that the maximum CO concentration is very insensitive to the variation in the scalar dissipation rate. An extinction event due to an abrupt imposition of high strain rates is also simulated by an impulsive velocity with various frequencies. For a fast impulse, a substantial overshoot in NO{sub 2} concentration is observed after extinction. Finally, the overall fuel burning rate shows a nonmonotonic response to the variation in characteristic unsteady time scale, while the emission indices for NO{sub x} shows monotonic decay in response as frequency is increased