In cylinder liquid fuel visualization during cold start

Abstract

In recent years carburetor injection systems in spark ignited (SI) engines have been replaced with port-fuel injection systems, and as a result there has been a significant increase in the levels of hydrocarbon (HC) emissions from SI engines during their cold start period. The presence of liquid fuel in the combustion chamber, during a cold start, is believed to contribute significantly to the increased levels. This work uses planar laser induced fluorescence to visualize the development of liquid fuel in the cylinder of a firing SI engine. A closed valve injection strategy was used, as this is the strategy most commonly found in practice. Fluorescence from indolene and iso-octane doped with acetone and 3-pentanone was used to examine volatility effects. Images were taken on three planes through the cylinder and a number of post-processing techniques were used to analyze the results. The results were analyzed on both a time and crank-angle (CA) basis. Analysis on a crank-angle basis relates the location of liquid fuel entering the cylinder to engine events, and shows a maximum in the quantity of liquid fuel coming from the back of the intake valve at the crank angle position closest to the position of maximum valve lift. A semi-quantitative analysis based on the integration of the image intensities shows the time development of liquid fuel in the cylinder, and highlights the volatility effects.