Combustion Analysis in an Optical Access Engine

Abstract

The ever more strict pollutant emissions regulations urge to make further steps in the evolution of the internal combustion engines, in particular as far as the emissions generation. A direct observation of the phaenomena taking place inside the cylinder can hence help in better understanding the effects obtainable by using different solutions (injection systems, ignition systems,…).To this end, the use of an optical access engine can be very helpful. This paper presents the first step made at the Department of Industrial Engineering of the University of Perugia for the set-up of an experimental line to be used for the analysis of combustion events observed in a single cylinder optical access engine.The combustion was characterized by using different techniques: thermodynamic (heat release) based on in-cylinder pressure measurements, and non intrusive optical observations by means of images acquisition. The flame images collected by a synchronized CCD camera were post-processed in order to evaluate the rates of the in-cylinder flame front evolution, observing the combustion process from the flame kernel formation on.Different fuels were used in the spark ignition, four valves, optical access engine: pure gasoline, pure ethanol, a 50% gasoline/ethanol blend. The experimental tests were carried out at 900rpm engine speed, in rich and lean conditions, the latter being of interest for the achievement of significant CO2 reduction.