Adaptive control of the ignition timing of spark ignition engines utilising the combustion flame light emissions
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
An examination has been made to determine whether the ignition timing in Spark Ignition engines can be accurately controlled from the combustion flame light emissions. In order to accurately set the ignition advance for optimum engine performance under all conditions of engine operation, an adaptive closed loop spark advance controller is required. Investigations of visible and infra-red electromagnetic radiation emitted from the combustion flame of four stroke petrol engines have been made. The light emissions were transmitted to light detection equipment through the use of a quartz glass window assembly or through a combination fibre optic cable and spark plug configuration constructed for light emission analysis. The detection equipment was used to produce either photographic records of the light emissions spectrum or flame light intensity curves as a function of time from photodetector output voltages. The results of these investigations showed that the combustion flame light emissions were strongly influenced by the ignition advance setting and they could be expected to form a suitable input to a spark advance control system. An electronic knock detection system was constructed using the light emissions intensity as the criteria for determining whether knocking combustion was occurring. The system proved capable of resolving the ignition advance to within 2° crankangle of the limit for knock. Further testing was completed in order to determine how the combustion product buildup on the inner glass surface would affect the light transmitted to the photo-detectors over a long period of engine operation. The photo-detectors were able to respond to the light levels transmitted through the glass for medium periods of engine operation (up to 100 hours). Finally, guidelines are given for further work in this field.