二甲醚/乙烷混合气低温着火延迟特性

To investigate the ignition delay characteristics of dimethyl ether (DME)/ethane (C₂H₆) mixtures at low temperatures, the ignition delays were measured at compressed temperatures of 627~912 K, compressed pressures of 16~30 bar, equivalence ratios of 0.5~1 and C₂H₆ blending ratios of 0~70 % based on a rapid compression machine (RCM). Meanwhile, the simulation was conducted at the same conditions as those in experiments using CHEMKIN-PRO software. Both experimental and simulation results show that the total ignition delay exhibits obvious negative temperature coefficient (NTC) behavior, especially at lower compressed pressures. Increasing compressed pressure and equivalence ratio lead to decrease the first-stage and total ignition delays, especially at NTC region. C₂H₆ addition inhibits the ignition process significantly, thus prolongs the first-stage and total ignition delays. Chemistry kinetics analysis indicates that C₂H₆ competes for OH radicals predominately produced by the DME's low-temperature oxidation, thus the ignition process of DME is delayed while the ignition process of itself is promoted and even presents evident two-stage characteristic. With the increase of C₂H₆ blending ratio, the ignition process of whole mixtures is inhibited, the accumulation of heat release rate and active free radicals is decreased and the ignition delays are prolonged.