Steady and pulsating propagation and extinction of rich hydrogen/air flames at elevated pressures

Effect of pressure on counterflow H2–air partially premixed flames

“…The maximum and minimum burning rates correspond to the transitions between first and second reaction limits, and second and third limits, respectively. The results show that the locations of both the local maximum and minimum mass-burning rates shift toward higher pressures as φ decreases in accord with the numerical investigation of Christiansen et al [18]. The quantitative differences with the results of Christiansen et al [18] are attributed to the modification of reaction (R9) in Mueller et al [23] from its predecessor [29] through the change in the low-pressure rate constant, k N 2 9,o .…”

“…The results show that the locations of both the local maximum and minimum mass-burning rates shift toward higher pressures as φ decreases in accord with the numerical investigation of Christiansen et al [18]. The quantitative differences with the results of Christiansen et al [18] are attributed to the modification of reaction (R9) in Mueller et al [23] from its predecessor [29] through the change in the low-pressure rate constant, k N 2 9,o . The effective reaction rate constant, k 9 , is now determined by the Troe fit [32,33] instead of the Lindemann-Hinshelwood fit [34] used in Kim et al [29], which was the mechanism used by Christiansen et al [18] with F N 2 c = 0.5.…”

“…For H 2 /air mixtures, it is important for a mechanism not only to predict the flame speed and structure, but also to reproduce the well-known reaction limits 2 [18]. Christiansen et al [18] have shown the existence of three reaction limits for freely propagating H 2 /air flames at φ = 7.0 by plotting the mass-burning rate as a function of pressure.…”

“…Christiansen et al [18] have shown the existence of three reaction limits for freely propagating H 2 /air flames at φ = 7.0 by plotting the mass-burning rate as a function of pressure. Recently, Zheng and Law [31] determined the temperatures of inert jets that ignited counterflowing lean premixed hydrogen/air jets 2 Reaction limits refer to the stages of chain-branching and chain-terminating reactions that control the characteristics of a flame, while ignition limits refer to the different chain reactions that control autoignition.…”

“…In contrast, the effect of pressure on diluted hydrogen counterflow nonpremixed flames has been extensively investigated to examine ignition [14][15][16] and extinction characteristics [17]. Pressure effects on rich premixed hydrogen/air flames have also been characterized [18].…”