Determination of the CO2 and N2 dilution influence on flame flashback limits of methane and propane combustible mixtures

International audience ; The flashback phenomenon in tubes has been known and studied for several decades. The classical analysis of this phenomenon is based on the determination of a critical velocity gradient that delimits the boundaries of flame flashback as a function of the mixture properties. However, significant knowledge gaps remain, particularly with regard to the effect of CO 2 dilution, which is important for predicting the safety of Brazilian pre-salt facilities. Accordingly, the general objective of this work is to experimentally determine the influence of CO 2 dilution on the flame flashback of gaseous air/hydrocarbon mixtures. In particular, the critical velocity gradient was determined for CH 4 /air mixtures with CO 2-diluted fuel (0, 10 and 30%). For comparison purposes, measurements were also performed on propane/air mixtures diluted by CO 2 or by N 2. For both diluent species, a reduction in the maximum value of the critical velocity gradient was observed with the increase of the dilution. Such as behavior was associated to the corresponding decrease with dilution of the laminar flame speed, which was computed using two chemical kinetics models.