Shock tube ignition delay times and methane time-histories measurements during excess CO2 diluted oxy-methane combustion

Abstract

The combustion of methane in air results in large amounts of CO 2 and NO X emissions. In order to reduce the NO X emissions, one possible solution is the oxy-methane combustion with large CO 2 dilution so that the combustion products can be reduced mainly to CO 2 and H 2 O. However, there are very few studies on the chemical kinetics of oxy-methane combustion in a CO 2 diluted environment. In this study, methane time-histories, CH* emission profiles, and pressure time-histories measurements were conducted behind reflected shock waves to gain insight into the effects of CO 2 dilution of the gas mixtures on the ignition of methane. The measurements were carried out for mixtures of CH 4 , CO 2 and O 2 in argon bath gas at temperatures of 1577-2144 K, pressures of 0.53-4.4 atm, equivalence ratios (Φ) of 0.5, 1, and 2, and CO 2 mole fractions (X CO2) of 0, 30%, and 60%. The laser absorption measurements were conducted using a continuous wave distributed feedback interband cascade laser (DFB ICL) centered at 3403.4 nm. The results showed the decrease of activation energy and the increase of ignition delay time as the amount of CO 2 dilution was increased. However, the changes were minor and within the experimental uncertainties of the measurements. Also, the results were compared to the predictions of two different natural gas mechanisms: GRI 3.0 and AramcoMech 1.3 mechanisms. In general the predictions were reasonable when compared to the experimental data; however, there were discrepancies at some conditions. Three different influences of CO 2 addition to the argon bath gas in regards to chemistry, collision efficiencies, and heat capacities were examined. In addition, the present study included experimentally obtained correlations for absorption cross sections of methane for its P(8) line in the v 3 band in argon bath gas with and without carbon-dioxide dilutions at temperatures between 1200 < T < 2000 K and pressures between 0.7 < P <1.2 atm. 1. INTRODUCTION Energy consumption has increased dramatically as the world advances and becomes more industrialized. Over the next twenty five years, the U.S. Department of Energy expects the energy demand to increase by 29% with almost all of the new energy from natural gas [1]. A problem is that current methods for the combustion of natural gas (e.g., gas turbines) result in large amounts of CO 2 and NO X emissions. In order to reduce the greenhouse gases, one possible solution is the oxy-methane

Experimental Design for Discrimination of Chemical Kinetic Models for Oxy-Methane Combustion

“…Figure 10present comparisons between models 5-7 and data reported byKoroglu et al 3. For all the data sets investigated, the GRI mechanism predicts smaller ignition delay times than the ITV and the Aramco mechanisms over a wide temperature range.…”

“…CO 2 not only has different specific heat and effective Lewis number compared to nitrogen, it is also chemically more active. [2][3][4] The excess CO 2 can participate in reactions either as a reactant or as a third body for collision and thus strongly affects fuel oxidation pathways. For example, the reaction of H radical with CO 2 is promoted due to the CO 2 enrichment.…”

“…Symbols denote the experimental measurements by Koroglu et al3 Solid lines show the numerical results with models.…”

“…Symbols denote the experimental measurements by Koroglu et al3 Solid lines show the numerical results with models. ) p = 0.75 atm, X CO 2 = 0) p = 0.75 atm, X CO 2 = 0.Ignition delay times for oxy-methane mixtures at 0.75 atm.…”

Progress in Rapidly-Tunable External Cavity Quantum Cascade Lasers with a Frequency-Shifted Feedback

“…Using a micro opto-electro-mechanical systems (MOEMS) scanning grating, Grahmann et al achieved a scanning rate of 1 kHz [5]. The improvement in tuning speed demonstrated for these devices, while impressive, is still insufficient for many important laboratory applications, including combustion/explosion diagnostics where a full spectral scan needs to be performed on the order of tens of microseconds (see, for example, Reference [6]). In practical situations, for applications involving optical detection of improvised explosive devices (IEDs) demand sub-millisecond spectral scan of a remote object.…”