A Comparison of Two Quantitative Laser Induced Fluorescence Techniques Applied to a New Air Guided Direct Injection SI Combustion Chamber

The important break-through introduced by Direct Injection SI engines in the car industry has undoubtedly lead to a fantastic acceleration in using very up to date investigation tools as 3D simulation codes or advanced optical techniques, such as Laser Induced Fluorescence.

The aim of this paper is to discuss and compare the conventional single tracer Fuel Air Ratio Laser Induced Fluorescence (FARLIF) and its Exciplex version. Basis of this comparison are given by a new Tumble Guided Direct Injection medium size engine developed by Renault.

While using a 93% iso-octane, and an adjusted proportion of benzene and tri-ethyl-amine (TEA) mixture as fuel for an optical engine, the LIEF technique has proved to be quantitative for the lambda determination even if a high amount of liquid is present. An accuracy of ±3% can be achieved in the interesting range of 0.8 - 1.2.

Besides an obvious interest for understanding the engine behaviour for different injection and ignition timings, FARLIEF measurements have also been used to secure 3D simulation results.