Initial characterisation of an auto-ignition burner with dense spray boundary conditions

An initial characterization of a dense-spray auto-ignition burner is presented. The burner, which consists of a multiple-stage atomizer developed earlier in [1-2], is now placed in a vitiated co-flow of hot combustion products. The geometry adopted here simulates the thermal conditions of an engine. An understanding of the flame structure is acquired through examination of digital photographs and microscopic high-speed shadowgraph imaging. The flame stability is dictated either by predominantly mixing and chemical kinetics in the `dilute regime’ or by mixing, chemical kinetics and atomization in the `dense regime’. The degree of atomization at the exit plane is characterized here by calculating the amount of blocked light in a particular measurement volume as a function of both liquid loading and carrier air flow- rate. When the flame is in the dilute regime, an increase in the blockage area results in adecrease in lift-off height, however, in the dense regime the opposite is observed.