Search Results

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.

To provide fuel/air ratio quantitative measurements in an S.I engines, a transparent cylinder engine is investigated with the Fuel-Air Ratio Laser Induced Fluorescence (FARLIF) technique. In a homogeneous mixture, the two dimensional distribution for the fuel/air ratio is calibrated and measured during the compression stroke for different equivalence ratios. After spark ignition, the combustion zone and the flame front are visualized by laser sheet LIF. The direct-injection stratified-charge, new concept for gasoline engines is investigated with FARLIF. In the direct injection gasoline engine where the fuel is directly injected into a cylinder and the flow is highly turbulent, two injection timings are used: -early injection (i.e. during the intake stroke) to promote a homogeneous distribution; -late injection during the compression stroke, to generate a ultra-lean stratified charge.