Nitromethane ignition behind reflected shock waves: Experimental and numerical study

Abstract

Ignition delay times for nitromethane have been measured behind reflected shock waves over wide ranges of temperature (875-1595 K); pressure (2.0-35 atm); equivalence ratio (0.5, 1.0, and 2.0); and dilution (99, 98, 95, and 90% Ar by volume) using a L9 Taguchi array. Emission from excited-state hydroxyl radials (OH*) was the primary diagnostic for determining the ignition delay times from the experiments. Results showed that nitromethane's ignition delay time is very sensitive to most of the experimental parameters that were varied. In addition, the OH* profile for nitromethane presents an interesting double feature, with the relative intensity between the two peaks varying greatly depending on the experimental conditions. A detailed chemical kinetics mechanism was assembled from previous work by the authors and from sub-mechanisms from the literature. The latest theoretical work on nitromethane decomposition was used, and the final mechanism satisfactorily reproduces the ignition delay time data from the present study, as well as nitromethane and CH 4 /NOx ignition delay time data available from the literature.

Insights into nitromethane combustion from detailed kinetic modeling – Pyrolysis experiments in jet-stirred and flow reactors

“…A positive sensitivity means that the reaction promotes the reactivity and negative sensitivity means that the reaction inhibits the reactivity. It can be seen for both pressures that the most sensitive reactions are HCO + NO ⇋ HNO + CO and O2 + H ⇋ OH + O which is in line with the results from the work of Mathieu et al [29]. Unlike for the PFR and JSR experiments, the thermal dissociation reaction of CH3NO2 is not among the most sensitive reactions.…”

“…Figure 18 compares the predicted ignition delay times against shock tube experimental data from the literature. Figure 18(a) shows results of the shock tube experiments by Mathieu et al [29] at three different equivalence ratios (ϕ = 0.5, 1.0 and 2.0) at 2 atm for CH3NO2/O2/Ar mixtures. The model captures the equivalence ratio dependency of ignition delay times very well and agrees with the experimental data for the temperature range studied.…”

“…Balance Ar and N2 for above mixtures. Symbols: experiments from [29] (a) and [27] (b); lines: simulations of this model.…”

“…were not available in literature. Nauclér et al [27] performed ignition delay time experiments of CH3NO2/O2/N2 in a shock tube and used two mechanisms from literature [28,29] to compare against their experimental data and mechanism predictions. Similarly, Brackmann et al [30] measured the burning velocity of CH3NO2/O2 diluted with CO2 and the concentrations of NO, CO and CH2O in two CH3NO2 flames (experimental condition shown in Table 1).…”

“…Similarly, Brackmann et al [30] measured the burning velocity of CH3NO2/O2 diluted with CO2 and the concentrations of NO, CO and CH2O in two CH3NO2 flames (experimental condition shown in Table 1). They used the same two mechanisms [28,29] as Nauclér et al and compared model predictions and measurements. It was concluded in both studies that none of the mechanisms is able to accurately predict the experimental data [27,30].…”