Analysis of ECN spray A ignition in a Rapid Compression Machine using simultaneous OH* chemiluminescence and formaldehyde PLIF

Abstract

The canonical diesel spray A is characterized in an optical Rapid Compression Machine (RCM) at high temperature and density conditions (900 K and 850 K, ρ = 23 kg/m3) using simultaneous high-speed OH* chemiluminescence and two-pulse 355 nm Planar Laser Induced Fluorescence (PLIF). The focus is on the time evolution and the repeatability of the early stages of both cool flame and hot ignition phenomena, and on the time evolution of the fluorescing formaldehyde region in between. In particular, time resolved data related to the cool flame are provided. They show the development of several separated kernels on the spray sides at the onset of formaldehyde appearance. Shortly after this phase, the cool flame region expands at high velocity around the kernels and further downstream towards the richer region at the spray head, reaching finally most of the vapor phase region. The position of the first high temperature kernels and their growth are then characterized, with emphasis on the statistics of their location. These time-resolved data are new and they provide further insights into the dynamics of the spray A ignition. They bring some elements on the underlying mechanisms, which will be useful for the validation and improvement of numerical models devoted to diesel spray ignition.

Editorial: Main results from Engine Combustion Network – France project: characterization of new experimental facilities and study of Diesel evaporation and combustion processes using advanced optical diagnostics

“…This special issue presents results from this collaborative project with five new papers [3][4][5][6][7] covering all aspects of the work performed, from standardization issues to advanced optical diagnostic developments.…”

“…The three other papers are dedicated to the results obtained to provide new insights on the physical processes occurring during the atomization of the dense liquid spray [5], the combustion process [6] and soot formation [7] by implementing advanced measurement techniques.…”

“…Strozzi et al [6] used simultaneous high-speed OH* chemiluminescence and two-pulse 355 nm planar laser induced fluorescence to provide unique data on the time evolution and the repeatability (and stochasticity) of the early stages of both cool flame and hot ignition phenomena. These new time-resolved data provide further insights into the dynamics of the spray A ignition and bring some elements on the underlying mechanisms to help the validation and improvement of numerical models devoted to diesel spray ignition.…”