Flame Imaging Studies of Cycle-by-Cycle Combustion Variation in a SI Four-Stroke Engine
892086
09/01/1989
- Event
- Content
- 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.
- Pages
- 30
- Citation
- Bates, S., "Flame Imaging Studies of Cycle-by-Cycle Combustion Variation in a SI Four-Stroke Engine," SAE Technical Paper 892086, 1989, https://doi.org/10.4271/892086.