at one atmospheric pressure. what is phsical state of matter at 298k and 398k??
Answers
A detailed chemical kinetic mechanism consisting of 2059 reactions and 391 species has been constructed to describe the oxidation of 2MF and is used to simulate experiment. Rate of production and sensitivity analyses have been carried out to identify important consumption pathways of the fuel and key kinetic parameters under these conditions.
Three different mixtures were prepared using the method of partial pressures.
The heat–flux method was first proposed by de Goey et al. [27] in 1993. This method does not require stretch correction or extrapolation of the data as stretching of the flame does not occur.
Uncertainties of around 1% were also present when determining the equivalence ratio due to mass flow effects, as given by the manufacturer. The temperature of the unburned gas mixture before and after it flowed through the plenum chamber was measured with a thermocouple. An error of 2 K was estimated. Errors in gas and liquid fuel purity were not significant as high purity compounds were used.
Given the presence of weak side chain C-H bonds (Figure 1), the kinetics of the reactions of the Ḣ atom with the fuel and abstraction reactions from this site are pertinent.
For Ḣ atom addition at C2, C3, C4 and C5 the respective high pressure limiting rate constants (in cm3 mol−1 s−1) are calculated as:
k(C2) = 7.53 × 108T1.51exp(−956.1 ∕ T)
k(C3) = 1.00 × 109T1.44exp(−2, 178 ∕ T)
k(C4) = 1.37 × 105T2.50exp(−1, 907 ∕ T)
k(C5) = 1.29 × 109T1.48exp(−1, 026 ∕ T)
Rate constants for abstraction of the methyl hydrogens by the ȮH and ĊH3 radicals are taken as half of those calculated in the case of 25DMF [22], with the rate constant for abstraction by the HȮ2 radical similarly determined. A simple factor of two division of the A-factor for these rate constants is appropriate given the corresponding reduction in the number of abstractable hydrogens.
At 1 atmosphere, the formation of vinylacetylene (C4H4) and Ḣ occurs with a rate constant of 1.02 × 1051T−11.42exp(−27, 284/T) s−1 and for the formation of C2H2 + Ċ2H3 we calculate a rate constant of 4.52 × 1044T−9.65exp(−25, 618/T) s−1.
Simulations were carried out using Chemkin-Pro [43] with the Aurora package under constant volume conditions utilised for the simulation of shock tube ignition delay times.
Sensitivity analyses are carried out in order to identify the key reactions which control the ignition delay time and laminar burning velocity under the experimental conditions presented.
with a negative sensitivity coefficient indicative of a reaction which promotes reactivity and vice versa. The first order sensitivity of the mass flow rate to the A-factor of each rate constant is used to determine those reactions which control the calculated laminar burning velocities.
Experimental ignition delay times and those calculated by the current model are defined in Figure 2. Experimentally, the effect of increasing O2 concentrations from 3% (Φ = 2.0) through 6% (Φ = 1.0) to 12% (Φ = 0.5) is clearly visible in the form of increased reactivity characterised by reduced ignition delay times.
Hydrogen atom addition at C2 consumes 15.4% of the fuel at Φ = 0.5 with 7.5% of this forming furan and methyl radical and 7.8% CO and 1-buten-1-yl (Ċ4H7-n or ĊH = CH − CH2 − CH3).
Sensitivity analyses (Figure 4) have shown these hydrogen atom addition reactions to inhibit reactivity for a number of reasons. These reactions prevent Ḣ atoms from reacting with O2 to form hydroxyl radicals and atomic oxygen by consuming 48.6% and 53.2% of the total hydrogen atoms in the system under lean and rich conditions respectively. This is clear in the increased sensitivity of these reactions under lean conditions.
Increasing the rate of abstraction by O2 is seen to promote reactivity, particularly under fuel lean conditions, as it provides a source of HȮ2 radicals which can react with methyl to produce CH3Ȯ and ȮH, with CH3Ȯ primarily undergoing decomposition to form formaldehyde and hydrogen atom.
Flame speeds are controlled by the reactions of hydrogen with molecular oxygen, although under lean conditions the oxidation of CO by the ȮH radical to produce CO2 and the Ḣ atom is equally as important.
A detailed chemical kinetic model consisting of 2059 reactions and 391 species which describes the combustion of 2-methyl furan .
Sensitivity and rate of production analyses have been carried out to identify important reactions of the fuel. Kinetics of the reactions of the Ḣ atom with the fuel are seen to be amongst the most sensitive in terms of predicting ignition delay times and flame speeds under the conditions studied and are therefore important in terms of predicting the global reactivity of the system.