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Abstract
In the present experimental study, some examples of hysteresis phenomena in combustion systems are described. In particular, the onset of acoustic instability of premixed flames in stagnation-point flow is investigated. It is found that for a given nozzle speed, transition from acoustic to non-acoustic burning regime is history dependent. The critical molar fuel concentrations X FU and X FL corresponding to the onset and termination of acoustic flames as a function of the mean exit velocity of the gas at the nozzle are determined which show the hysteresis band. In the study, additional example of such hysteresis effects in terms of the extinction and re-establishment of combustion of premixed flames in the stagnation-point flow is examined. Finally, the hysteresis effects associated with the onset and termination of rotation of polyhedral butane Bunsen flames as a function of the velocity of a co-flowing nitrogen stream is investigated. The possible significance of the results to the modeling of flamelet dynamics in turbulent combustion is discussed.