Journal of the Society of Motion Picture Engineers (1930-1949)

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Motion Photography for Combustion Research By F. W. BOWDITCH The history of the use of semi-high-speed photography as a research tool for the study of the combustion process in gasoline engines at General Motors Research Laboratories is presented. The investigations consist of direct photography of the luminous combustion process as seen through quartz windows in the heads of several gasoline internal combustion engines. Both commercial cameras and cameras designed and built in these laboratories were used. JL HE USE OF photography to study the combustion process as it occurs in a gasoline internal combustion engine was first successfully attempted1 at the Research Laboratories Division of General Motors Corp. in 1930. Until then practically all information known about gasoline engine combustion had been obtained from pressure-time cards and from sampling valve studies. The results of the pressure card and sampling valve studies indicated that these methods alone could not completely describe the physical aspects of the combustion process. It was decided that by taking photographs of the combustion process through a quartz window mounted in the head of a single-cylinder engine a physical picture of the combustion process could be obtained. Since the use of a quartz window in the head of an engine was entirely new, it was decided that a Presented on October 9, 1952, at the Society's Convention at Washington, D.C., by F. W. Bowditch, Research Laboratories Division, General Motors Corp., Detroit 2, Mich. long, narrow quartz window would be the easiest to install and seal. Such a window 5 in. long and 0.375 in. wide was built into the head of a singlecylinder engine in a manner shown in Fig. 1. A film drum was mounted over the engine, with the axis of the cylinder parallel to the major axis of the quartz window, and a Meyer Plasmat //1. 5 lens was used to focus the quartz window on the drum. The drum and a focal-plane type shutter were driven from the camshaft of the engine in a direction normal to the direction of flame travel in the engine. The engine and camera equipment are shown in Fig. 2. Eastman Portrait Panchromatic cut film was wrapped around the drum, sufficient circumferential drum space for the film being provided so that enough film for one explosion could be used at a time. Examples of knocking and nonknocking type of flame record obtained are the upper parts of Fig. 3. Photographs of the ignition sparks appear at A and of timing sparks at B, 20° later. The flame photographs were taken with the film moving toward the left and the 472 December 1952 Journal of the SMPTE Vol. 59