Hidetaka Nohira

Evaluation of Burned Gas Ratio (BGR) as a Predominant Factor to NOx

Experiments were conducted with four cylinder production engines to evaluate the effect of EGR and mixture stoichiometry on NOx by measuring the burned gas ratio in the cylinder (BGR) by using a gas sampling valve and CO//2 gas analyzer. The total gas fuel ratio (G/F) in the cylinder, which is a function of air-fuel ratio (A/F) and BGR and is some measure of adiabatic combustion peak temperature of charge, was introduced as a new measure to evaluate the combustion in the cylinder. G/F ratio coupled with A/F could be utilized to evaluate the combustion characteristics such as NOx emission, misfire limit, etc. in various combustion chamber configurations. NOx emission and misfire limit are strongly affected by the BGR in the cylinder. Stoichiometrically burned gas EGR has the best potential to reduce NOx together with power for a fixed engine displacement, but from the point of view of fuel economy and misfire limit indicated by G/F, its mixture is the second to leanest A/F, when the critical constraint of NOx and better fuel economy were considered.

STATISTICAL ANALYSIS OF PRESSURE INDICATOR DATA OF AN INTERNAL COMBUSTION ENGINE

A statistical indicator data analyzer has been developed, which is able to analyze various combustion characteristics such as rate of pressure increase, heat release rate, etc., from indicator data of four hundred combustion cycles of each cylinder of a multicylinder engine. Statistical analyses on cycle-by-cycle variation of indicated mean effective pressure (imep) were made under various combinations of fuel systems and combustion chamber configurations to clarify those effects. The contribution of characteristics on the variation of imep was made clear to some extent. /SASI/