Thermochemical oscillation of methane MILD combustion diluted with N₂/CO₂/H₂O

Abstract

Strict environmental rules endorse moderate or intense low oxygen dilution (MILD) combustion as a promising technology to increase efficiency while reducing pollutants emission. The experimental and theoretical investigation of oscillatory behaviours in methane MILD combustion is of interest to prevent undesired unstable combustion regimes. In this study new speciation measurements were obtained in a jet-stirred flow reactor (JSR) for stoichiometric mixtures of CH 4 and O 2 , diluted in N 2 , CO 2 and N 2-H 2 O, at p = 1.1 atm and T = 720-1200 K. Oscillations were experimentally detected under specific temperature ranges, where system reactivity is sufficient to promote ignition, but not high enough to sustain complete methane conversion. A thorough kinetic discussion highlights reasons for the observed phenomena, mostly focusing on the effects of different dilutions.

Jet-Stirred Reactor Study of Low-Temperature Neopentane Oxidation: A Combined Theoretical, Chromatographic, Mass Spectrometric, and PEPICO Analysis

“…Figure presents the conversion of neopentane measured at ϕ = 0.5 and the temperature range T = 500–850 K, and it compares the experimental data with predictions by the kinetic model. It should be noted that neopentane oxidation was studied for temperatures up to 1100 K. However, oscillatory behaviors were observed at temperatures above 1000 K. This transient evolution of the mole fractions of reactants and products during oscillating limited cycles have already been observed in the literature during fuel combustion at high temperatures. − Because oscillatory chemistry is not the subject of this work, only data up to 850 K are considered.…”

Oscillatory Behavior in Methane Combustion: Influence of the Operating Parameters

“…This occurs because the predicted temperature oscillations are characterized by spike variations in less than 10 ms, and even though the response time of the thermocouples is very short (≅30 ms), the temperature increase cannot be properly resolved in time. A detailed analysis of numerical temperature profiles can be found in the study by Bagheri et al…”

“…The experimental conditions are summarized in Table 1. Data for cases S1, S2, and S3 are from Bagheri et al 28 Furthermore, the data collected for each data set are provided in the Supporting Information.…”

“…Recently, Bagheri et al . explored thermochemical oscillations of methane from a kinetic modeling perspective, also focusing on the effect of different dilution gases (N 2 , H 2 O, and CO 2 ) in promoting or inhibiting such instabilities.…”

A comprehensive investigation of acoustic power level in a moderate or intense low oxygen dilution in a jet-in-hot-coflow under various working conditions

“…This technology is a promising option for practical applications and a significanat amount of research effort has been already devoted to further understand various aspects of MILD combustion. For instance, Parente et al [1][2][3][4][5] conducted a series of studies on reactive flows pertinent to MILD combustion. Mousavi et al [6][7][8][9] examined MILD (flameless oxidation) regime under various working conditions such as angled injection and reported that angled injection leads to an increase in turbulence intensity and reduces the emission of air pollutants.…”