Numerical investigation on the ignition and flame characteristics of n-dodecane-n-butanol spray under diesel engine conditions

•Effects of diesel-n-butanol blend on ignition and flame characteristics were investigated.•First-stage ignition site is at spray periphery except for Bu20 at 800 K.•OH, CH2O, HO2 and H2O2 species are shifted towards the fuel-lean.•M-LTC mode is dominant during the first-stage ignition.•M-HTC and M-HTC-diff modes are dominant from the second-stage ignition onwards.