Auto-Ignition of DME/DMM Fuel Blends. Part I: Minimizing Temperature Dependency by Blend Optimization
2022
Vinkeloe, J. | Zander, L. | Djordjevic, N.
Combustion concepts based on auto-ignition are prone to detonation formation and premature ignition in the presence of local spots with increased reactivity, which can be caused by unavoidable temperature inhomogeneities in real technical applications. In this study, a fuel blend optimization approach using a fuel component with negative temperature coefficient (NTC) behavior (dimethyl ether, DME) and a fuel component without NTC behavior (dimethoxymethane, DMM) is employed to reduce the temperature sensitivity of ignition delay times and therefore reduce the tendency of premature ignition and detonation development. First, ignition delay times and first stage ignition of a DMM/air mixture are measured behind reflected shock waves in a high-pressure shock tube (20 and 35 bar, stoichiometric conditions) to select a suited chemical kinetic model. Using these data and additional literature data, a mechanism is chosen, which is used to numerically optimize the blending ratio of DME and DMM to minimize the temperature sensitivity of ignition delay times in the temperature range between 800 and 900 K for both considered pressures. The two optimized fuel blends are investigated in the shock tube regarding their ignition characteristics as before (20 and 35 bar, stoichiometric conditions). Finally, the impact of pressure, equivalence ratio, and temperature range on the optimization result is investigated numerically.
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