Two-dimensional visualization of liquid layers on transparent walls

Abstract

A new two-dimensional visualization technique based on laser-induced fluorescence for investigation of liquid-fuel films on transparent walls was applied in an SI engine. For optical access the upper part of the engine cylinder is replaced with a quartz ring. An UV laser beam is coupled into the ring, forcing total reflection at quartz-air interfaces. Because of the similar indices of refraction of quartz and fuel, laser light penetrates into the liquid. The corresponding fluorescence signal visualizes areas where wall film is present. It is shown that the technique is an excellent tool for investigation of wall-film development in combustion engines.