Influence of temperature inhomogeneities on knocking combustion

The use of a rapid compression and expansion machine (RCEM) provides the possibility of investigating the fundamental kinetic behavior of combustion. The aim of this work is the investigation of the influence of temperature inhomogeneities on the reaction kinetics of knocking combustion under well-known conditions without having random fluctuations. In the RCEM a clearly defined temperature distribution was generated that covers a large area and facilitates the investigation of the influence of a temperature gradient on knocking combustion. The paper deals with the analysis and characterization of the different phases of low-temperature kinetics during knocking as well as nonknocking combustion. Combustion was controlled by ignition timing, variation of the spark plug position, compression ratio, and temperature distribution. The results show the formation of a fast-propagating flame due to local and sequentially progressing autoignitions, which initiate a detonation as a consequence of pressure waves, which progress into an already reacting gas mixture enriched with intermediate species and radicals.