An experimental study of natural ionization in hydrocarbon flames, using the negative electrostatic probe at atmospheric pressure I. A technique for measurement of ion density

Abstract

A technique is described for the measurement of ion density in atmospheric pressure H2-O2-N2 flames containing hydrocarbon gases. A highly negative spherical electrostatic probe is used and is calibrated in unseeded flames of ion density 108-109 ions/cm3. The probe current-ion density characteristic is shown to be of the form n=κI1·45±0·08 where, in this case, κ=(7·9±3·2)×1018 (n is in ions/cm3 and I is in amperes). The expression is compared with a theoretical probe law deduced from the high pressure, continuum theory of Su and Lam.The experiment provides extensive data on the dependence of ion density and recombination rates on flame composition. This material is given in Part II of this paper.