Probing the antagonistic effect of toluene as a component in surrogate fuel models at low temperatures and high pressures. A case study of toluene/dimethyl ether mixtures

The fundamental low-temperature ignition (T < 900 K) behavior of toluene was studied using dimethyl ether (DME) as a radical initiator to induce ignition. The influence of DME on the combustion of toluene ignition was investigated in both shock tube and rapid compression machines as a function of temperature (624 K-1459 K) pressure (20-40 atm) equivalence ratio (0.5-2.0) and blending ratio (100% toluene 76% toluene (76T/24D) 58% toluene (58T/42D) 26% toluene (26T/74D) and 100% DME). Model analyses suggested that although the initial reaction of the fuel was dominated by single-step H-atom abstraction reactions from both the benzylic and phenylic sites the subsequent reaction of the allylic and vinylic radicals formed was much more complex. An updated chemical kinetic model which is better able to predict the antagonistic effect of toluene on more reactive components was introduced and subsequently can be used in gasoline surro-gate fuel formulations without the need for major revisions to existing surrogates.