Flame Imaging Studies of Cycle-by-Cycle Combustion Variation in a SI Four-Stroke Engine 892086

Sets of sequential-cycle instantaneous flame images are used to study cycle-by-cycle variation of lean combustion in a spark-ignition four-stroke optical engine. Stereo gated image-intensified NTSC video cameras record flame radiation to show three-dimensional structure, while flame development is measured in each cycle by super-imposing early and later flame images.
A variety of physical causes for cyclic variation are identified from the images. Correlations of flame geometry with mass burned fraction show that a larger initial flame kernel size results in a faster early burn in the cycle, and that flames that are flatter on a large scale cause lower peak burn rates than round flames. The early flame kernel is shown to vary greatly in size, shape, and location. This kernel has a major effect on combustion by setting the basic flame shape in mid-cycle. Large scale unstable flows appear to cause major cyclic variation in flame shape and combustion, an effect seen at 500 rpm, but which has disappeared at 1000 rpm.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.