The effect of the hydrogen presence on combustion-induced rapid phase transition of CO/O2/N2 mixtures

•Explosion of CO/H2/O2/N2 mixtures was studied at different O2 and H2 contents.•Experimental tests were performed in a tubular closed vessel.•In the presence of H2, combustion-induced Rapid Phase Transition (cRPT) was found.•Water plays a key role in driving the cRPT phenomenon.

The explosion behavior of CO/O2/N2 mixtures was experimentally studied in a tubular closed vessel at different oxygen contents, in the presence and in the absence of hydrogen.We found that CO/O2/N2 mixture explosion does not exhibit cRPT whatever the oxygen content thus demonstrating that this phenomenon is strictly connected to the water produced by the combustion reaction. Conversely, the addition of even very small amounts of hydrogen, triggers the cRPT phenomenon eventually leading to over-adiabatic peak pressures. The obtained results confirm the key role of water in driving the cRPT phenomenon.In the presence of hydrogen (even small amounts), an intense explosion, the combustion-induced Rapid Phase Transition (cRPT), was found. This highlights the key role of water in driving the cRPT phenomenon.