Experimental Study on Behavior of Unburned Hydrocarbons on Combustion Chamber Wall of Spark Ignition Engine.

Abstract

It is known that exhaust HC emissions from spark ignition engines play an important role in photochemical reactions. Sources of unburned HCs from engines are considered to be quench crevices in the combustion chamber, and oil layer and deposits on the surface of the combustion chamber wall. The behavior of unburned HCs on the surface of the combustion chamber wall was investigated with using a high-speed gas sampling technique during expansion and exhaust processes. The shape and the volume of the sampling gas in the combustion chamber were calculated to obtain the thickness of the HC layers on the surface of the combustion chamber wall. Two models of the HC concentration profiles on the surface of combustion chamber are proposed. One is a two layer model and the other is a homogeneous model. The mass of HCs on the surface of combustion chamber was estimated according to the models. It was found that mass of HCs was gradually increased in the expansion and early exhaust strokes.