These high-speed natural combustion luminosity and OH* chemiluminescence images are taken through the bottom of the piston at a frame rate of 25 kfps. For each energizing dwell tested, images are available from the first five skip-fired cycles from four different runs, so there are 20 cycles' worth of images for each dwell. The images have been distortion corrected and background subtracted as described in (Park and Busch, 2017). The processed images have been saved in .mat files for each of 20 fired cycles, and for the ensemble averaged cycle. Each .mat file contains two variables. The first variable, "cad" is the crank angle at which each image has been taken. The second variable, "images", is a 3-dimensional matrix. The first two dimensions are the image size, and the third dimension is the crank angle.

The images have been taken from the bottom, and the orientation is described in Injector Clocking and Labels.png. The scaling of the distortion corrected images is 3 pixels/mm.

The first image is taken just after the start of solenoid energizing for the pilot injection. Natural luminosity images are available until 30 CAD ATDC. OH* chemiluminescence images are intended to show high temperature reaction zones during the pilot combustion and main ignition events, so they are available until 6 CAD ATDC.