Effects of Mixture Distribution on Exhaust Emissions as Indicated by Engine Data and the Hydraulic Analogy

The objectives of this study are twofold. First, engine data are presented which indicate how the three major automotive exhaust pollutants are affected by the distribution of the inducted fuel. Nonuniform fuel distribution prohibits lean engine operation without increasing hydrocarbon emissions. Nitrogen oxide emissions are lower at a given fuel-air ratio with nonuniform fuel distribution, this condition being particularly true near stoichiometric conditions. Carbon monoxide emissions are lower with more uniform fuel distribution.

The primary objective of this paper is to demonstrate a new method of studying the mixing conditions that take place in an induction system. This method involves the use of a conventional water table, a facility to demonstrate pictorially the salient flow field characteristics and mixing patterns that were encountered at typical engine operating conditions. Also, several different geometric configurations and their resultant flow patterns are included. Some of these configurations were duplicated in an experimental induction system and were shown to have similar flow field patterns.