2-D Visualization of liquid and Vapor Fuel in an I.C. Engine 880521

A sheet of laser light from a frequency tripled Nd-YAG laser approximately 200μm thick is shone through the combustion chamber of a single cylinder, direct injection internal combustion engine. The injected decane contains exciplex—forming dopants which produce spectrally separated fluorescence from the liquid and vapor phases. The fluorescence signal is collected through a quartz window in the cylinder head and is imaged onto a diode array camera. The camera is interfaced to a microcomputer for data acquisition and processing. The laser and camera are synchronized with the crankshaft of the engine so that 2—D images of the liquid and vapor phase fuel distributions can be obtained at different times during the engine cycle. Results are presented at 600, 1200 and 1800 rpm, and from the beginning to just after the end of injection. The liquid fuel traverses the cylinder in a straight line in the form of a narrow cone, but does not reach the far wall in the plane of the laser sheet. The vapor fuel penetrates further in a broader cone, and reaches the far wall, where it is deflected and convected by the swirling flow. Quenching of the vapor phase fluorescence by oxygen is examined and found to be very strong at the high pressures in the engine cylinder. Consequently, all the data reported are for a motored engine using nitrogen rather than air.