Turbulent flame boundary and structure detection in an optical DISI engine using tracer-based two-line PLIF technique

Design and development of new combustion system for Spark Ignition Direct Injection (DISI) engines
requires thorough understanding of the flame as it develops from electric discharge and propagates
across the combustion chamber. The main purpose of this work was to develop an experimental setup
capable of investigating premixed and partially-premixed turbulent flame boundary and structure inside
combustion chamber of a DISI engine. For this purpose the tracer-based two-line Planar Laser Induced
Fluorescence (PLIF) technique was set up. In order to have a thermometry technique independent of photophysical
models of dopant tracer, a specially designed Constant Volume Chamber (CVC) was utilized for
quasi in situ calibration measurements. The thermometry technique was evaluated by measurements of
average in-cylinder charge temperature during compression stroke for both motoring and firing cycles
and comparing the results with temperature values calculated from in-cylinder pressure data. The developed
technique was successfully employed to detect flame boundary and structure during combustion
process in the optical engine. The present study demonstrated that as the two-line PLIF thermal images
are independent of species concentration and flame luminosity they can be utilized as accurate means for
flame segmentation. The proposed technique has the potential to be utilized for study of turbulent flames
in non-homogeneously mixed systems.