https://backend.orbit.dtu.dk/ws/files/145750384/Nreview_revised.pdf

Modeling nitrogen chemistry in combustion

Kinetics of pollutant formation and destruction in combustion

Current interest in high-temperature N/H/O kinetics stems primarily from the practical importance of combustion-generated emissions of nitrogen oxides (NOx). The recognition of air pollution as a problem of societal concern has prompted a concentrated research effort on the kinetics of NOx formation and decomposition and has led to a considerable expansion in the fundamental data base for rate constants of elementary reactions in the N/H/O system. The objectives of this survey are twofold: (1) to provide critical rate constant evaluations of reactions for which high-temperature data have been recently acquired, with due consideration given to previous evaluations, particularly the widely used survey at Leeds University (Baulch, et al., 1973); and (2) to provide an extensive compilation of N/H/O reactions and rate constants including both nonevaluated and evaluated reactions, that is, reactions for which limited or no rate data are available currently as well as reactions which have undergone critical reviews previously or in this study.

Survey of Rate Constants in the N/H/O System

The existing experimental data on the rate coefficients for the chemical reactions in nonequilibrium high temperature air are reviewed and collated, and a selected set of such values is recommended for use in hypersonic flow calculations. For the reactions of neutral species, the recommended values are chosen from the experimental data that existed mostly prior to 1970, and are slightly different from those used previously. For the reactions involving ions, the recommended rate coefficients are newly chosen from the experimental data obtained more recently. The reacting environment is assumed to lack thermal equilibrium, and the rate coefficients are expressed as a function of the controlling temperature, incorporating the recent multitemperature reaction concept.

A review of reaction rates in high temperature air

A detailed quasiclassical trajectory study of the O2+N→NO+O reaction is performed based on ab initio potential-energy surfaces of the 2A′ and 4A′ states. The study is aimed at generating a database of thermally averaged and O2 state-specific rate constants needed for accurate simulations of NO kinetics in high-temperature flow processes. The rate constants obtained show good agreement with the available experimental data and with other quasiclassical trajectory calculations. It is found that the reactant internal energy of the O2+N→NO+O reaction is less effective in enhancing the rate than in the N2+O→NO+N reaction. An analysis of the product vibrational energy shows that NO formed by the O2+N→NO+O reaction has a non-Boltzmann distribution. It is also found that the most populated NO vibrational level is determined by the reactant vibrational energy, while the terminal slope of the NO vibrational distribution is a strong function of the reactant translational temperature.

Thermal rate constants of the O2+N→NO+O reaction based on the A2′ and A4′ potential-energy surfaces

Experimental results are presented for the formation of oxides of nitrogen in the burned gas region of premixed oxy-propane flames burning at atmospheric pressure. The majority of the experiments were conducted using argon-shielded laminar flames, and a lean and a rich flame were studied each containing two different amounts of nitrogen. Data are also presented for a rich oxy-propane flame burning unshielded on a commercial glass blowing torch. The use of mathematical modelling of the rate of nitric oxide in the laminar flames has been investigated. It has been shown that reasonable agreement between experimental and computed profiles can be obtained simply by the use of the two reactions. coupled with K1=107.93cm3 mole-1 sec-1 at 2880 K.

The Formation of Oxides of Nitrogen in some Oxy-Propane Flames

The properties and behaviour of the post-reaction zones of three fuel-rich propane/oxygen flames burning on a commercial torch have been investigated. Flame temperatures were measured by a number of methods, and the rotational temperatures of ground state hydroxyl radicals were found to be the most reliable. The concentrations of the major combustion products were in good agreement with computed values, although the concentrations of hydroxyl radicals in the richer flames were greatly influenced by air entrainment.

A. L. Roberts

Papers

The Formation of Oxides of Nitrogen in some Oxy-Propane Flames

Some Properties of Oxy-Propane Flames