A Complete Pressure−Temperature Diagram for Air Oxidation of Hydrogen in a Continuous-Flow Stirred Tank Reactor

We report the temperature and pressure dependence of the dynamics at short residence times of a fuel-lean hydrogen−air mixture in an isothermal continuous-flow stirred tank reactor. The reaction between hydrogen and oxygen is modeled by a set of twenty reversible reactions involving nine species over the temperature and pressure ranges 300−1100 K and 10 -3 −10 bar, respectively. Boundaries of dynamically distinct regions in a complete pressure−temperature diagram are calculated with a path-following algorithm based on pseudo-arclength continuation. We find a region of birhythmicity, thus showing that chain-branching alone can account for the coexistence of stable oscillatory states, and a region containing a periodic-orbit isola, a new feature for this system. Although infinite-period orbits exist just a few degrees below the ignition curve, oscillatory ignition does not occur under the conditions of our simulations.