Two-dimensional laboratory-scale DNS for knocking experiment using n-heptane at engine-like condition

Abstract

A two-dimensional laboratory-scale DNS of a knocking experiment using a stoichiometric n-C7H16/O2/Ar mixture at engine-like condition with the latest reduced SIP isooctane kinetics was conducted. A compressible reactive flow solver PeleC combined with an in-house efficient chemical kinetics solver MACKS was used. The results of DNS were compared with a “knocking experiment by Kyushu University” conducted in a 14 × 14 × 80 mm rectangular constant volume chamber for the same mixture at an initial temperature of 480 K and pressure of 0.33 MPa. The comparisons showed the present DNS with the latest, validated reduced chemical kinetics successfully reproduced the knock onset timing within an error of 2% as well as the overall features of the experimental observations seen in the Schlieren images such as flame shape transitions, pressure history, and the characteristic faint increase in pressure due to the flame front attachment with the chamber wall. In addition, the present DNS captured that the cool flame ignition occurred homogeneously but accompanied by the rapid formation of density gradients vertical to the side walls in the unburned gas region.