Prediction of electron and ion concentrations in low-pressure premixed acetylene and ethylene flames

Abstract

Flame stabilisation and extinction in a number of different flows can be affected by application of electric fields. Electrons and ions are present in flames, and because of charge separation, weak electric fields can also be generated even when there is no externally applied electric field. In this work, a numerical model incorporating ambipolar diffusion and plasma kinetics has been developed to predict gas temperature, species, and ion and electron concentrations in laminar premixed flames without applied electric fields. This goal has been achieved by combining the existing CHEMKIN-based PREMIX code with a recently developed methodology for the solution of electron temperature and transport properties that uses a plasma kinetics model and a Boltzmann equation solver. A chemical reaction set has been compiled from seven sources and includes chemiionisation, ion-molecule, and dissociative–recombination reactions. The numerical results from the modified PREMIX code (such as peak number densities of positive ions) display good agreement with previously published experimental data for fuel-rich, non-sooting, low-pressure acetylene and ethylene flames without applied electric fields.

Keywords:

• plasma
• premixed flames
• one-dimensional laminar flames
• electron
• numerical simulations

Acknowledgments

We thank Professor Alexander Burcat of the Israel Institute of Technology for providing thermodynamic data for some of the ionic species used in these calculations. We also thank Dr. Sergey Pancheshnyi of the University of Toulouse for his helpful discussions on statistical mechanics and plasmas. Lastly, we thank Dr. Arthur Phelps of the University of Colorado for his helpful discussions on electron collision cross-section data. This material is based upon work partially supported by the US Department of Energy Office of Basic Energy Services under Grant No. DE-FG02–88ER13966 (MDS and BAVB). The Department of Energy's support does not constitute their endorsement of the views expressed in this paper.