This is an image of a spherical diffusion flame of ethylene burning in air in the NASA GRC 2.2 s drop tower. The image was recorded about 1.4 s after ignition. The ethylene flowrate is 1.5 mg/s and the scale is revealed by the 6.5 mm porous sphere visible in the image. The image was recorded using a Nikon D100 digital single-lens reflex camera with a 125 ms exposure.
Credit: P.B. Sunderland (University of Maryland), D.L. Urban and D.P. Stocker (NASA Glenn Research Center), B.H. Chao (University of Hawaii) and R.L. Axelbaum (Washington University)