Technical Paper
Detection of Knocking Combustion Using Simultaneously High-Speed Schlieren Cinematography and Multi Optical Fiber Technique
1991-10-01
912312
Flame propagation as well as the special role of detonation waves during knocking combustion are still unsolved questions. In order to examine these phenomena during cyclic resolved knocking combustion, high-speed schlieren photography and multi optical fiber technique were applied simultaneously. The pictures were taken at a rate of 200 000 frames per second, whereas the flame radiation signals of the knocking combustion, detected with the multi optical fiber technique at 49 measuring points, were recorded with a sampling frequency of 500 kHz. The exact correlation between schlieren photography and optical fiber technique shows that knocking combustion is initiated by self ignitions in the unburned regions, clearly separated from the spark ignited flame. The complete autoignition (i.e. knocking combustion) proceeds in two stages thus showing distinct prereactions.