SPATIAL-RESOLUTION OF FUEL DISTRIBUTION IN AN ENGINE USING INFRARED-ABSORPTION

We describe a novel method of obtaining the fuel concentration at vari ous points along the longitudinal axis of a spark ignition engine. Thi s allows us to measure the effect of various engine and fuel parameter s on charge stratification in the combustion chamber. The technique is based on sampling the infrared (IR) absorption spectrum through the t ransparent sapphire engine cylinder. The absorbance is measured at fou r points down the chamber axis using four IR launching fibers, each of which is matched to a collection fiber. The spectra are simultaneousl y dispersed and stacked on a diode array detector. We subtract the bac kground from the absorption peak to obtain the absorbance which is sho wn to be directly proportional to fuel concentration. We find that the axial charge stratification and its evolution during the induction an d compression strokes is a sensitive function of injection timing and swirl valve setting. The technique is also applicable to gas phase rea ctors and any system where spatially homogeneous mixing of reactants i s required. (C) 1997 American Institute of Physics. [S0034-6748(97)039 11-7].