Effects of non-equilibrium plasma discharge on ignition and NTC chemistry of DME/O₂/Ar mixtures: A numerical investigation

The effects of non-equilibrium plasma discharge on ignition characteristics and low-temperature chemistry (LTC) of DME/O2/Ar mixture are numerically investigated through a self-consistent simulation in a plane-to-plan geometry at reduced pressures of 76 Torr. One-dimensional, nano-second plasma discharge model is used the first time to study the two-stage ignition process and negative-temperature coefficient (NTC) behavior of DME mixtures. This kinetic mechanism consists total number of 69 species, and 414 reactions, which is a combination of plasma kinetic model and DME combustion kinetic model. The initial temperatures are set to be 550K and 800K. With initial temperature of 550K, the negative temperature coefficient (NTC) regime where LTC dominates, the ignition delay time for plasma-assisted case is improved by ∼250 times for the first-stage, and 15 times for the second-stage or overall. With the initial temperature of 800K, the intermediate temperature regime, the overall ignition delay time is shorten by ∼75 times with plasma addition. Moreover, the results suggest that, plasma not only enhance DME ignition characteristic time dramatically by orders of magnitudes, but also alters reaction pathway and makes the disappeared two-stage ignition behavior for 800K case reappeared. In addition, for 800K case, the intermediate temperature regime, the enhancements bring by plasma addition on ignition delay time and LTC are non-linear; there exists a range of optimized pulse number, 35-40 pulses in this work, where accumulative energy input brings the most efficient enhancement.