Shock-tube investigation of self-ignition of n-heptane-air mixtures under engine relevant conditions

To determine self-ignition characteristics under conditions relevant to piston engines combustion, n-heptane-air mixtures have been investigated in a high-pressure shock tube without use of the customary heat bath dilution. The initial pressure has been varied between 3.2 and 42 bar and the initial temperature between 660 and 1350 K, while the equivalence ratio covers the region between 0.5 and 3.0. In dependence upon these parameters the histories of pressure and CH-band emissions at 4315 Å show different ignition behavior. This can be related to different modes of ignition, as “strong” ignition and “weak” ignition and in part to two-stage-ignition. The dependence of the ignition delay times upon initial temperature, pressure and equivalence ratio is presented. A comparison with previous work is given.