A lower flammability limit prediction model of alkane-CO2 mixtures based on flame phenomenon simulation

In the present study, a novel model is proposed to evaluate the lower flammability limit(LFL) of alkane diluted with CO2. The LFL model is based on flame phenomenon simulation(FS-LFL). The model consists of combustion, turbulence, and igniter models, which are used to characterise the combustion based on the chemical kinetics and CFD, which is not feasible with traditional methods. The flame simulation phenomenon was validated by contrast with experiment and same criterion of flammability limit in the experiment was adopted. The FS-LFL model was used to predict the LFLs of a propane-CO2 mixture and propane at various temperatures. The model performance was analysed by comparing the results with experimental data and predictions obtained from existing methods. The AARDs between the predicted and experimentally determined LFLs of the propane-CO2 mixture are 0.34%, 1.19%, and 1.35% at 30℃, 50℃, and 70℃, respectively. The model also has a good predictive power with respect to the LFLs of propane at initial temperatures ranging from 30℃–300℃, with an AARD of 2.10%. When the dilution of CO2 is 90%, the model yields a better result due to the utilisation of the chemical kinetics mechanism. This result is instructive for the use of this method in the prediction of upper flammability limits.