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Abstract: Experiments are conducted on n-decane and JP-10 flames, stabilized between two counterflowing streams—fuel stream and oxidizer stream. The fuel stream is a mixture of prevaporized fuel and nitrogen, and the oxidizer stream is air. Critical conditions of extinction are measured for n-decane and JP-10. Concentration profiles of , and hydrocarbons from to are measured. These measurements are made by removing gas samples from the flame using a quartz microprobe and analyzing the samples using a gas chromatograph. Temperature profiles are measured using a thermocouple. Numerical calculations are performed using detailed kinetic models to predict the flame structure and critical conditions of extinction and autoignition. The predicted values of the critical conditions of extinction and autoignition for n-decane agree well with experimental data for extinction and with previously measured autoignition data. For JP-10, for a given mass fraction of fuel in the fuel stream, the predicted strain rates at extinction are higher than the measurements. The predicted autoignition temperatures, however, agree well with previously measured experimental data. The predicted profiles and maximum mass fractions of the major species are found to agree with the measurements. There are, however, differences between the predicted and measured mass fractions of those species that have more than three carbon atoms. In general, the concentrations of saturated hydrocarbons in the n-decane flame are higher than those in the JP-10 flame. [ABSTRACT FROM AUTHOR]

Abstract: Experimental and numerical studies are carried out to develop a surrogate that can reproduce selected aspects of combustion of kerosene. Jet fuels, in particular Jet-A1, Jet-A, and JP-8 are kerosene type fuels. Surrogate fuels are defined as mixtures of few hydrocarbon compounds with combustion characteristics similar to those of commercial fuels. A mixture of n-decane 80% and 1,2,4-trimethylbenzene 20% by weight, called the Aachen surrogate, is selected for consideration as a possible surrogate of kerosene. Experiments are carried out employing the counterflow configuration. The fuels tested are kerosene and the Aachen surrogate. Critical conditions of extinction, autoignition, and volume fraction of soot measured in laminar non premixed flows burning the Aachen surrogate are found to be similar to those in flames burning kerosene. A chemical-kinetic mechanism is developed to describe the combustion of the Aachen surrogate. This mechanism is assembled using previously developed chemical-kinetic mechanisms for the components: n-decane and 1,2,4-trimethylbenzene. Improvements are made to the previously developed chemical-kinetic mechanism for n-decane. The combined mechanisms are validated using experimental data obtained from shock tubes, rapid compression machines, jet stirred reactor, burner stabilized premixed flames, and a freely propagating premixed flame. Numerical calculations are performed using the chemical-kinetic mechanism for the Aachen surrogate. The calculated values of the critical conditions of autoignition and soot volume fraction agree well with experimental data. The present study shows that the chemical-kinetic mechanism for the Aachen surrogate can be employed to predict non premixed combustion of kerosene. [Copyright &y& Elsevier]

An activation-energy asymptotic theory is developed that predicts autoignition of condensed hydrocarbon fuels in non-premixed flows. Steady, laminar, stagnation-point flow of an oxidizer stream, toward the vaporizing surface of a liquid fuel is considered. The analysis is restricted to the case where the temperature of the oxidizer stream, T2, is greater than the normal boiling point of the liquid fuel. The gas-phase chemical reaction is described by a one-step overall process. The chemical-kinetic rate parameters are the activation temperature, Ta, and the frequency factor, B. A Zel'dovich number, β, is constructed that is proportional to the ratio Ta/T2. The analysis is performed in the asymptotic limit of large values of β. It predicts the value of the Damkohler number, at autoignition. The Damkohler number is defined as the ratio of a characteristic flow time to a characteristic chemical reaction time. The flow time is the reciprocal of the strain-rate, and the chemical time depends on the chemical-kinetic rate parameters. To illustrate the application of the results of the analysis, experiments are conducted in the counterflow configuration. Fuels tested are n-heptane, n-octane, n-decane, n-dodecane, n-hexadecane, iso-octane, cyclohexane, methylcyclohexane, o-xylene, JP-10, JP-8, and diesel. The temperature of the oxidizer stream at autoignition is measured for various values of the strain-rate. The strain-rate, and the value of the Damkohler number at autoignition, obtained from the analysis, are used to obtain the chemical-kinetic rate parameters, for the fuels tested here. Critical conditions of extinction of flames burning these liquid fuels are also measured. A key finding of this work is that for the straight-chain alkanes tested here, at a given value of the strain-rate, n-heptane is the most difficult to ignite, followed by n-octane, n-decane, n-dodecane, and n-hexadecane. The order is reversed for extinction; here it is found that flames burning n-heptane and n-octane are the most difficult to extinguish followed by n-decane, n-dodecane, and n-hexadecane. [ABSTRACT FROM AUTHOR]