Measurement of flame speeds by a nozzle burner method

Abstract

The literature records a great many meas urements, using stationary flames on burners of the speed with which flame moves through combustible mixtures of gases. D espite th~ fact that the method itself seems reasonably simple, the results obtained by various invcstigato:s often are not in good agreement. One of the phases of a program of research on combustIOn has been a study of some of the r easons for the differences among recorded values of flame speed measured by the burner method. The primary objective of this task has been to develop the precautions t hat should be observed in applying t he method, rather than to e volve numerical values of flame speed . This paper describes progress that has been made since the apparatus was described originally in 1951, and presents val ues of flame speeds of methane-air mixtures obtained s ince then, together with comparisons of these val ues with those obtained by two flame theories.

Effect of perchloryl fluoride additions on the flame speed of methane

“…Since these variations are small, they may be due to experimental difficulties, such as locating the flame front in the enlargements of the flame photographs, and thus they may fall within the experimental error. However, the trends seem to be consistent and, since a similar variation of flame speed with gas velocity had been found for methane-air flames previously [ 7 ], it is felt that the variation does exist. Conditions of the gas flow in the throat of the nozzle, e.g., the presence or absence, and the extent, of a boundary layer, are the most likely cause.…”

“…As may be noted from the data listed in table 2 , the addition of perchloryl fluoride to the combustible mixture shifted the mixture ratio at which maximum flame speed occurs. It had been found previously [ 7 ] that maximum flame speed, 1.233 fps, for methane-air at a temperature of 84.4 °F occurred at mixture ratio of 0.062. The addition of 2 percent by volume of perchloryl fluoride moved the maximum flame speed to a mixture ratio for methane to air plus perchloryl fluoride of 0.072.…”

“…A description of the apparatus and the method used to measure flame speeds has been presented earlier [ 7 ]. Briefly, this apparatus comprises drying and metering systems for both air and fuel, a conditioning chamber for the mixture of fuel and oxidant, and a nozzle, the exit of which is the burner port.…”

“…The winter temperature was about 80–85 °F, while the summer temperature was about 95–100 °F. The variation of flame speed with mixture temperature for methane-air flames had been found to be 0.0048 ft/°F [ 7 ]. The effect of temperature on methane-air-perchloryl fluoride and methane-air-oxygen flames, especially at low concentration of additives, should be of similar magnitude.…”

Influence of coal dust on premixed turbulent methane–air flames

“…Strehlow et al [41] published results from a steady state-burner in 1974. The basic objective of the burner design was to obtain two relatively large-area coaxial streams with flat laminar velocity profiles, such that the central stream could be completely surrounded by hot products from the combustion of a gaseous fuel in the outer stream.…”