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This paper describes a laser-induced fluorescence (LIF) method for quantitative 2-D fuel concentration measurements in an SI engine. The combination of fluorescence tracer and excitation wavelength to lower the temperature and pressure effects on LIF intensity were evaluated. Each kind of fluorescence tracer selected from ketones, aldehydes and aromatics has been excited at 248 nm or 266 nm in a heated and pressurized constant volume vessel. For the promising candidates, further evaluation has been performed using a fired visualization engine. The results show that the optimum combination which gives the lowest effects of temperature and pressure on LIF intensity is acetone with 266 nm excitation. 3-pentanone, which is commonly used fluorescence tracer has been shown to be not suitable for the quantitative measurements, especially in a fired engine.

NO laser-induced fluorescence (LIF) imaging and quantitative fuel distribution measurements in aport-fuel-injected 4-valve stratified-charge single-cylinder SI engine have been conducted using a tunable KrF excimer laser. The correlations between NO formation region and fuel distribution have been investigated for the horizontal stratification realized by fuel (iso-octane) injection in only one intake port. The NO LIF intensity is proportional to the exhaust NOx emissions. The strong NO LIF intensity region in expansion stroke corresponds to the location of the region with equivalence ratio (ϕ) between 0.8 and 1.1 in the stratified fuel distributions at spark timing. The exhaust NOx concentration is proportional to the area of region with ϕ =0.8 - 1.1.