2-D visualization of liquid fuel injection in an internal combustion engine

A sheet of laser light from a frequency-doubled Nd-YAG laser (λ = 532 nm) approximately 150 μm thick is shone through the cylinder of a single cylinder internal combustion engine. The light scattered by the fuel spray is collected through a quartz window in the cylinder and is imaged on a 100 × 100 diode array camera. The signal from the diode array is then sent to a microcomputer for background subtraction and image enhancement. The laser pulse is synchronized with the crank shaft of the engine so that a picture of the spray distribution within the engine at different times during injection and the pe'etration and development of the spray may be observed. The extent of the spray at different positions within the chamber is determined by varying the position and angle of the laser sheet with respect to the piston and the injector. Results are presented for two injector configurations, one where the spray impinges normally on the opposite cylinder wall, and another where the spray impinges on the piston crown at an acute angle. In both cases an engine speed of 600 rpm was used. Elements of the structure of these sprays, from beginning of injection through past its end, are discussed.