Experimental studies of the role of chemical kinetics in turbulent flames

Abstract

Flames of di-t-butyl-peroxide (DTBP) decomposition in a 0.376DTBP + 1.0N 2 mixture are studied in laminar and turbulent media. The observed values of unstretched laminar burning velocity are in reasonable agreement with the value obtained from the Zel'dovich-Semenov-Frank-Kamenetsky theory. Turbulent explosions in this particular mixture are characterized by a number of features that are believed to be common for all developing turbulent flames and have relevance to spark-ignition engine combustion of lean mixtures. Flame propagation is unsteady and is characterized by a mass burning rate that increases in time. The rate of the flame acceleration varies from one explosion to another. If the burning rate is related to the average flame radius, however, it exhibits much smaller variations. This phenomenon bears a striking resemblance to cycle-to-cycle variations in a spark-ignition engine. Comparisons of the present results with mixtures of significantly different composition, chemical kinetics, and exothermicity, but with similar laminar flame speed and Lewis number show that the data obtained in closed-volume explosions are in good agreement if the unsteady character of the flame is taken into account. The differences in details of the kinetic mechanisms and thermochemistry appear to be responsible for the flame behaviour only near the limit of extinction by turbulence.

Turbulent Combustion of Hydrogen–CO Mixtures

“…4 presents is the temporal development of the laminar burning rate u nr . For a spherical flame propagating outwards, the burning rate, as determined from the pressure record [26,37] and shown with lines in Fig. 4, equals the flame speed relative to the moving fresh gas.…”

Does Density Ratio Significantly Affect Turbulent Flame Speed?

“…The present authors are aware on a single attempt to address the issue by substantially changing the density ratio in experiments. To do so, Burluka et al [43] measured speeds of flames of di-t-butyl-peroxide (DTBP) decomposition in a 0.376DTBP + 1.0N2 mixture in the well-known Leeds fan-stirred bomb. In spite of a low value of σ = 3.57, the documented dependencies of S t on were “in good agreement” with experimental data obtained by other research groups from hydrocarbon-air mixtures “with similar laminar flame speed and Lewis number” [43], thus, implying a minor effect of σ on S t .…”

“…To do so, Burluka et al [43] measured speeds of flames of di-t-butyl-peroxide (DTBP) decomposition in a 0.376DTBP + 1.0N2 mixture in the well-known Leeds fan-stirred bomb. In spite of a low value of σ = 3.57, the documented dependencies of S t on were “in good agreement” with experimental data obtained by other research groups from hydrocarbon-air mixtures “with similar laminar flame speed and Lewis number” [43], thus, implying a minor effect of σ on S t . However, such a conclusion appears to be insufficiently solid, because it was drawn by comparing the Leeds DTBP data with data obtained using other techniques in other laboratories.…”

Opposing Propagation Characteristics of Methane-Air Deflagrations in an End-to-End Pipe

“…Many researchers have already carried out in-depth studies on combustible gas explosions and shock wave damage [3][4][5][6][7][8][9][10]. A brief introduction to gas explosion safety was presented by Bjerketvedt et al [11], and the body of knowledge about flame acceleration and the deflagration-to-detonation transition (DDT) in smooth ducts, as well as ducts equipped with turbulence-producing obstacles, was reviewed by Ciccarelli and Dorofeev [12].…”