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A recently developed spark plug equipped with fiber-optic flame-arrival detectors has been used to measure the motion and rate of growth of the early flame kernel. The cylinder pressure and gas velocity in the spark gap were measured simultaneously with the flame kernel measurements, permitting the data to be analyzed on a cycle-by-cycle basis to identify cause-and-effect correlations between the measured parameters. The data were obtained in a homogeneous-charge research engine that could be modified to produce three very different flow fields: (1) high swirl with high turbulence intensity, (2) tumble vortex with moderate turbulence intensity, and (3) negligible bulk motion with low turbulence intensity. The results presented show a moderate correlation between the combustion duration and the rate of growth of the flame kernel, but virtually no correlation with either the magnitude or direction of movement of the flame kernel away from the spark gap.

Two tests of composite shells loaded under half-cosine impulsive loadings are discussed. One cylinder which included no other materials was modeled successfully such that calculated results matched test results out to late times. The other cylinder, which included an inner annulus of an elastomeric material, was less successfully modeled, even though the composite material was modeled similarly in both instances. A viscoelastic model and an elastic model were both used to model the elastomeric material, and the viscoelastic model produced significantly better results.