Experimental Investigation of the Stabilization and Structure of Turbulent Cool Diffusion Flames

Abstract

Although recent studies of laminar cool flames have provided important advances in understanding the low-temperature chemistry of both hydrocarbons and oxygenates, there has been limited experimental insight into how interactions between turbulence and chemistry occur in cool flames. To address this, a new Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner has been developed and characterized in this investigation for the purpose of directly studying turbulent cool flames. A methodology for establishing stable turbulent cool diffusion flames under well-defined conditions is proposed. The structure of dimethyl ether flames is examined using both formaldehyde planar laserinduced fluorescence and Rayleigh scattering. It is found that weak turbulence produces wrinkled turbulent cool flames in which fluctuations occur mainly on the fuel side of the flame. However, at increased levels of turbulence, large pockets of unburned reactants appear in the vicinity of the cool flame, and structural fluctuations extend to both sides of the flame. This study offers a well-defined experimental platform for the study of turbulence-chemistry interactions at low temperatures.

Experimental and Kinetic Study on the Cool Flame Characteristics of Dimethyl Ether

“…2 The turbulent cool diffusion flames are also studied experimentally with a Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner. 34 Therefore, it is urgent to improve the mechanism for the cool flame and enrich the experimental data for the ignition and flame structure in the cool flame region.…”

“…In these counterflow experiments, the flame is typically ignited by preheating one side of the oxidant and fuel, and different flame states are measured by varying the strain rate, the equivalence ratio, the boundary temperature, and so on. In addition, Gao 29 and Reuter et al 34 also performed cool flame measurements in glass tubes and turbulent coaxial jets, respectively. In summary, the DME counterflow cool flames structure in different configurations is shown in Table 2.…”

“…It is found that a proper residence time corresponding to an appropriate strain rate is essential to a steady-state cool flame in a premixed DME/N 2 /O 2 mixture in the counterflow configuration . The turbulent cool diffusion flames are also studied experimentally with a Co-flow Axisymmetric Reactor-Assisted Turbulent (CARAT) burner . Therefore, it is urgent to improve the mechanism for the cool flame and enrich the experimental data for the ignition and flame structure in the cool flame region.…”