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A comparative study on the auto-ignition of non-premixed dimethyl ether and ethanol counterflow flames


In this study, combustion behaviors and characteristics of ethanol, dimethyl ether (DME) and their blends are investigated. Dimethyl ether and ethanol, the two fuels used for the study, are isomers of C2H6O, which have the same molecular formula but distinct chemical structures. The goal is to investigate and comprehend the differences, similarities and their interaction in fuel mixtures. The chemical kinetic software tool Cantera is used for numerical computations in the study. Prior experimental research data are reproduced and detailed analyses are conducted. Counterflow diffusion flame simulations are employed in the study as the experimental research utilizes a counterflow burner design. Auto-ignition simulation studies are conducted using San Diego mechanism as chemical kinetic mechanism. The San Diego Mechanism is a condensed chemical-kinetic mechanism utilized in combustion modeling applications, and it is developed and hosted by the University of California San Diego combustion group. For the computational studies a sub-mechanism for dimethyl ether(DME) is implemented to the main mechanism. Across the simulations, fuels with various partial percentages are used but the overall mass fraction remained constant at 0.4. For each fuel mixture, the oxidizer stream’s temperature at autoignition is noted. Additionally, thorough investigations of the heat release rate analyses and reaction rate analyses are done to identify the dominant reactions in various mixtures. Low and high strain rate analyses are elucidated considering the dominant reactions identified in the heat release rate analyses and reaction rate analyses. In low strain rate analyses, there is a series of reactions related from CH3OCH3(DME) with OH. The decrease of DME in the mixtures and increasing competition of OH from ethanol decreases the magnitude of heat release. High strain rate analyses show that, the dominance of ethanol related reaction, CH3CHOH reacts with O2, decreases from pure ethanol to pure DME. On the other hand, the additional DME reacts with OH which increases its dominance.

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