Unexpected performance of systematically derived one-step chemistry in describing rich hydrogen-air pulsating flames

A one-step reduced chemical-kinetic mechanism describing near-critical hydrogen combustion, recently derived by assuming that all chemical intermediates maintain steady state, is used to investigate numer-ically the pulsating dynamics of fuel-rich hydrogen-air flames. The computations, considering pressures of up to 20 atmospheres, address the flame evolution for increasing values of the equivalence ratio phi, a relevant bifurcation parameter. Besides critical conditions associated with the Hopf bifurcation occur-ring at a critical value phi(c) of phi, supercritical dynamics for phi > phi(c) is investigated, including the nonlinear gradual growth of the oscillation amplitude with increasing phi, the occurrence of a period-doubling bi-furcation, and the emergence of nonlinear relaxation oscillations. Comparisons with results of numerical calculations employing detailed chemistry reveal that the one-step description is able to predict with un-expectedly good accuracy the flame dynamics, including the critical conditions at the bifurcations as well as the nonlinear dynamics encountered for phi > phi(c). (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

A simplified chemical-kinetic mechanism is used to numerically investigate the pulsating dynamics of fuel-rich hydrogen-air flames, showing unexpectedly good accuracy in predicting flame dynamics, critical conditions at bifurcations, and nonlinear dynamics encountered for phi > phi(c).