Search Results

Video imaging has been used to investigate the evolution of liquid fuel films on combustion chamber walls during a simulated cold start of a port fuel-injected engine. The experiments were performed in a single-cylinder research engine with a production, four-valve head and a window in the piston crown. Flood-illuminated laser-induced fluorescence was used to observe the fuel films directly, and color video recording of visible emission from pool fires due to burning fuel films was used as an indirect measure of film location. The imaging techniques were applied to a comparative study of open and closed valve injection, for coolant temperatures of 20, 40 and 60 °C. In general, for all cases it is shown that fuel films form in the vicinity of the intake valve seats.

Video imaging has been used to investigate the evolution of liquid fuel films on combustion chamber walls during a simulated cold start of a port fuel-injected engine. The experiments were performed in a single-cylinder research engine with a production, four-valve head and a window in the piston crown. Flood-illuminated laser-induced fluorescence was used to observe the fuel films directly, and color video recording of visible emission from pool fires due to burning fuel films was used as an indirect measure of film location. The imaging techniques were applied to a comparative study of single and dual spray fuel injectors for both open and closed valve injection, for coolant temperatures of 20, 40 and 60°C. In general, for all cases it is shown that fuel films form in the vicinity of the intake valve seats.

An experiment designed to quantify probe-induced aerodynamic perturbations to in-cylinder sampling measurements in a motored engine is discussed. Good agreement was observed between concentration measurements obtained with a sampling probe utilizing a flame ionization detector and those obtained by laser Raman scattering at the probe tip. However, large differences were found between the Raman-measured concentration profiles obtained with and without the probe installed in the engine. These differences occurred because of probe-induced perturbations to the in-cylinder air motion which decreased the mean velocity and increased local mixing rates. Effects due to probe orientation in the flow, probe insertion depth, probe inflow, and far-field flow perturbations are reported.

A two dimensional flame front visualisation technique, based on Mie scattering from particles dispersed in the combusting mixture, has been developed. The technique was used in an I.C. engine simulator to study the freely propagating flame in premised combustion. It is shown that flame front structures can be resolved for scales as low as 2×10−4 m. These scales were observed at 1500 RPM where velocity fluctuations are known to be on the order of 6 m/s. For lean propane combustion, peninsulas and pockets of unburned mixture are observed in the postflame regions at 600 RPM. Higher turbulence levels increase the global flame front area by creating flame front corrugations of various length scales. Evidence of flame front wrinkles having sizes comparable to previously reported flame thickness in engines suggests that I.C. engine models should take into account the interaction between the velocity field and the detailed structure of the diffusive-reactive flame front zone.