Experimental investigation of methanol and ethanol flames in nonuniform flows

Abstract

Experimental studies are conducted on extinction and autoignition of methanol and ethanol flames in laminar, nonuniform flows. Two flame types are considered: nonpremixed and premixed. The studies are performed in the counterflow configuration. The burner used in the experiments is made up of two ducts. Studies in the nonpremixed configuration are carried out by injecting a stream comprised of fuel vapors and nitrogen from one duct, and a stream of air from the other duct. In the premixed configuration a premixed-reactant stream made up of fuel vapors, air, and nitrogen, is injected from one duct, and a nitrogen stream from the other duct. Numerical calculations are performed using detailed chemistry at conditions corresponding to those used in the experiments. For the nonpremixed systems considered here, the calculated values of the critical conditions of extinction agree well with experimental data. At given values of the strain rate and temperature of the fuel stream, the calculated temperature of the oxidizer stream at autoignition is found to be higher than the measured values. In the premixed configuration the strain rate at extinction is measured for various values of the equivalence ratio of the mixture in the premixed-reactant stream, ϕ 1. The value of ϕ 1, at which the calculated extinction strain rate is the highest, is found to be larger than the value of ϕ 1 at which the measured extinction strain rate is the highest. Sensitivity analysis is carried out to test the influence of various elementary reactions on critical conditions of extinction. The structure of a nonpremixed methanol flame is investigated. Concentration profiles of stable species and temperature profiles are measured. The flame structure is calculated using detailed chemistry. The results of numerical calculations agree well with experimental data.