Direct Numerical Simulation of Turbulent Spray Autoignition of n-Heptane/Air Under Low Initial Air Temperature

2D-Direct numerical simulation (2D-DNS) with complex chemistry is carried out to study the spray autoignition process of n-heptane/air under low initial air temperature, i.e. \(T_{{{\text{air}}}} = 740{\text{K}}\) . The ignition process presents three-stage, and there exist three types of propagation flames controlled by low-, intermediate- and high-temperature chemical (LTC, ITC and HTC) reactions respectively. The low temperature ignition occurs in the lean mixture, and LTC stage lasts about 13 ms. However, the intermediate- and high- temperature ignition occur successively in the rich mixture due to the propagating cool flame, and the value of the most reactive mixture fraction is larger than the homogeneous simulations.