Wednesday, April 29 at 9:00 a.m.
BlueJeans (https://bluejeans.com/587024806)
Bin Wu
(Advisor: Prof. Wenting Sun)
Investigation of Ozone Assisted Ethylene Combustion at Low-Temperature: Kinetics and Dynamics
Abstract
With increasing demands on high-efficiency fuel-energy conversion at harsh environments, great attentions have been drawn by novel combustion concepts. Among many, ozone (O3) assisted combustion has shown great potential in active combustion enhancement and control at extreme conditions. Unlike saturated hydrocarbon, whose reaction with O3 is virtually negligible at low temperature conditions, the reaction between O3 and unsaturated hydrocarbon has intrinsically very low activation energy barrier and high heat release. Using non-premixed C2H4 jet and O2/O3/N2 co-flow configuration, continuous formation of auto-ignition kernels was observed even at room temperature and pressure, and the equivalent flame front propagation speed could be hundred times faster than the regular laminar flame speed. However, the detailed kinetics behind such auto-ignitive phenomenon is unclear. Although the mechanism of C2H4 ozonolysis reaction, i.e. C2H4+O3, has been extensively investigated for decades among atmospheric chemistry community, studies under conditions align with combustion applications are sparse, where secondary reactions are believed to be significant.
In this work, detailed kinetic study of C2H4/O3/O2 reaction system is conducted experimentally at T = 298 K. Many new products and intermediates are characterized using an online fast-mixing flow reactor system coupled with synchrotron radiation VUV photoionization mass spectrometry (SRVUV-PIMS). Groups of peroxy radicals are detected in considerable abundances for the first time and might be the key to rationalize the observed auto-ignitive phenomenon from chemical kinetic point of view. In parallel, the effect of O3 addition on flame dynamics of C2H4 is investigated using non-premixed laminar lifted flame. It appears the steady lifted flame could either ascend or descend with O3 addition, depending on the initial flame liftoff height before O3 is added. This outcome is inconsistent with similar experiment using saturated fuel, in which only flame liftoff height decrease was observed. The corresponding kinetic/dynamic interaction is proposed and qualitatively supported by numerical simulations.
Committee