Ignition thresholds and flame propagation of methane-air mixture: detailed kinetic study coupled with electrical measurements of the nanosecond repetitively pulsed plasma discharges

Abstract

A disk-ring nanosecond pulsed discharges plasma actuator was developed to be applied in a rectangular cross-section burner. The measured reduced electric field (EN), power dissipation and energy per pulse were used for validation of the plasma kinetic code ZDPlaskin. Then the effect of plasma discharges dynamics on methane/air flames, were numerically estimated. Firstly, plasma chemistry computations based on an extended kinetic mechanism of methane/air mixtures were performed by ZDPlasKin. Then, the results obtained by the ZDPlasKin in the form of kinetic effects (concentrations of O, OH, O3, CH, CH3 and H) and thermal effects (rise in temperature) were used in CHEMKIN to evaluate the combustion enhancement. The flame speed was improved by increasing both reduced electric field and repetition rates. Assuming EN = 200Td (as in experiments), and pulse repetition rate equal to 100Hz, the flame speed was increased of 26% in comparison with the case without the plasma actuation. Furthermore, at 10000 Hz, the flame speed was three times higher than at 100Hz. The ignition delay time greatly reduced from 1.2×10-3s (without plasma) up to 3.0×10-5s at 10000Hz repetition rate. The plasma assisted ignition n (PAI) permits ignition of the mixture at lower inlet temperature than in the case of self-ignition, meaning that ignition is possible in cold flow condition, with a possible application for the re-ignition problems at high altitude conditions. Finally, higher repetition rate leads to lower number of required pulses for the ignition of the CH4-air mixture and lower peak flame temperature.

Direct HCN synthesis via plasma-assisted conversion of methane and nitrogen

“…Plasma-assisted CH 4 conversion chemistry has received considerable attention, with emphasis on excited species (17,(19)(20)(21). Zerodimensional (0D) plasma kinetic models typically consider many vibrationally and rotationally excited and metastable species, radicals, and charged and neutral molecules (22)(23)(24)(25). For our DBD plasma, e-impact dissociation is the primary excitation channel (23).…”

Identification of flow structures in a closed chamber in the presence of a needle plasma actuator

“…Because of the hydrodynamic effects of flow, the plasma actuation could be restrained as quasi-steady. 6,7 The LDV system allowed simultaneous measurement of two velocity components. Specifically, the two velocity components are LDA1 for the x-component and LDA4 for the y-component.…”

“…4,5 Many studies investigated the applications of NTPs to enhance the ignition and combustion processes. [6][7][8][9][10][11] The basic principle of NTPs is to produce plasma in which electrical energy is transformed to fuel in the form of highenergy electrons without increasing the gas temperature. 12 NTPs are produced through a variety of electrical plasma discharges, for example, radio frequency discharge, direct current glow discharge (DCGD), corona discharge, microwave discharge, atmospheric pressure discharge, surface discharge, pulsed corona discharge, and dielectric barrier discharge (DBD).…”