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The schlieren visualization of in-cylinder processes from the side of an engine cylinder is useful to understand the phenomena which change along the cylinder axis. A transparent collimating cylinder, TCC, permits schlieren observation inside the cylinder through its transparent wall. In this study, a single cylinder visualization engine with the TCC was applied to a direct-injection gasoline engine. A fuel spray, mixture formation and combustion were observed with a simultaneous measurement of in-cylinder pressure. The shape of the fuel spray and subsequent mixture formation process are drastically changed with the injection timing. The images of luminous flame were also taken with the schlieren images during the combustion period. Stable combustion, misfire and abnormal combustion are discussed with the comparison between the observed results and in-cylinder pressure analysis.

A square piston engine and a side-view collimating (SVC) cylinder engine are developed for side-view schlieren visualization of in-cylinder processes. The square piston engine has a square cylinder with two flat quartz windows permitting optical access to the entire cylinder volume. Compression sealing is provided by three polyimide ring assemblies which maintain the windows clean during the actual observation. In contrast with the square piston engine, the SVC cylinder engine permits to take schlieren photographs in practical engine geometries. This is made possible by designing the SVC cylinder so that it does not disperse parallel light rays. The physical principle and optical property of this cylinder are described. High speed schlieren movies were taken with these two transparent cylinder engines. Typical pictures, such as those of flame propagation, unburned gas motion, and formation of fuel and air mixture, are presented.

A television viewing system with a high speed shutter TV camera has been developed for viewing and recording combustion processes in internal combustion engines. The technique has been applied to the study of combustion events in an engine with a transparent piston. The recorded combustion images were analyzed and statistically processed by a microcomputer for summation, averaging, and contour forming. The averaged flame propagation patterns are discussed in comparison with the gas flow motion and cylinder pressure data obtained by conventional methods. This TV technique is easy and effective in obtaining combustion data for various operating conditions and engine geometries.