Development of diagnostic techniques for the spark discharge and the flame characteristics, applied in a lean burn spark ignition engine to examine the relations between the spark discharge, the flame, the heat release and the fluid flow

摘要

This thesis deals with the development of measurement systems for a research SI-engine, operating with lean air-fuel mixture, to examine the causes of cycle to cycle variations. The data acquisition system consists of four major parts: A flame imaging system and measurement systems for spark ignition parameters, in cylinder fluid flow and cylinder pressure. This report deals with the designing of the flame imaging and spark ignition measurement systems. Measurements have been performed of a single cylinder research engine. The purpose of the flame imaging system was to extend the heat release analyses to a much lower degree than the pressure measurement allows. To achieve information about the combustion start, the supplied voltage and current to the spark plug was measured and analysed. The data, achieved from the entire acquisition system, have been statistically analysed to investigate the correlation between the combustion parameters, i.e. the mean velocity and turbulence of the air-fuel mixture in the vicinity of the spark plug, the breakdown voltage and supplied current to the spark plug, the flame development from the imaging system and the heat release parameters from the pressure analyses. The flame imaging system consists of two single shot CCD-cameras and they have been used with schlieren technique in two configurations, one time resolving and one 'two-view' arrangement. The spark current was measured during five decades of time. To achieve this, it was necessary to use a very fast digital storage oscilloscope to resolve the first micro second and extended with an ordinary storage oscilloscope to measure the entire spark duration. 23 refs., 9 tabs., 160 figs