Evaluating upper flammability limit of low hydrocarbon diluted with an inert gas using threshold temperature

•Theoretical model based on temperature threshold has been developed.•A priority hypothesis for the consumption of the available oxygen was introduced.•A general standard temperature was suggested for low hydrocarbons.•The R2-value of the model is 0.9951 for nitrogen as diluent.

This paper proposed a method using threshold temperature to evaluate upper flammability limit of a hydrocarbon diluted with an inert gas. A priority hypothesis for the consumption of the available oxygen was introduced. A linear relation model that could be applied for evaluating upper flammability limit of any low hydrocarbon diluted with a specific inert gas was founded theoretically. Examination of the model has been conducted on existing experimental data, including the cases of methane, propane, propylene, ethylene and isobutane. Results show that, given an inert gas, there may be a general critical temperature that could fit to any low hydrocarbon in case that the inert gas is not involved in combustion kinetics. The threshold temperatures recommended for carbon dioxide and nitrogen are 1700 K and 1650 K, respectively. The model is further compared to a similar published model and is shown to be far more accurate.