Effect of Plasma-Enhanced Low-Temperature Chemistry on Deflagration-to-Detonation Transition in a Microchannel

This study examines low-temperature chemistry (LTC) enhancement by nanosecond dielectric barrier discharge (ns-DBD) plasma on a dimethyl ether (DME)/oxygen (O-2)/argon (Ar) premixture for deflagration-to-detonation transition (DDT) in a microchannel. It is found that non-equilibrium plasma generates active species and kinetically accelerates LTC of DME and DDT. In situ laser diagnostics and computational modeling examine the influence of the ns-DBDs on the LTC of DME and DDT using formaldehyde (CH2O) laser-induced fluorescence (LIF) and high-speed imaging. Firstly, high-speed imaging in combination with LIF is used to trace the presence of LTC throughout the flame front propagation and DDT. Then, competition between plasma-enhanced LTC of ignition and reduced heat release rate of combustion due to plasma-assisted partial fuel oxidation is studied with LIF. Observations of plasma-enhanced LTC effects on DDT are interpreted with the aid of detailed kinetic simulations. The results show that an appropriate number of ns-DBDs enhances LTC of DME and increases CH2O formation and low-temperature ignition, accelerating DDT. Moreover, it is found that, with many ns-DBDs, CH2O concentration decreases, indicating that excessive discharges may accelerate fuel oxidation in the premixture, reducing heat release and weakening shock-ignition coupling, inhibiting DDT.