Determination of the Speed of Flames and the Temperature Distribution in a Spherical Bomb from Time-Pressure Explosion Records

Abstract

A method has been developed for determining the velocity of flame relative to the mass movement of the gases, in a closed spherical bomb from an analysis of the time-pressure record of the explosion. The speed of the flame can be evaluated at any moment during its progress from the center to the periphery of the bomb, as well as the temperature existing in the unburned phase, the temperature immediately behind the flame front, the temperature gradient from the latter point to the center of the bomb, and the pressure in the bomb at the same moment. Given a certain fraction burned of the total amount of gas, the volume occupied by the products can be determined for three conditions: (1) Before it has expanded against the rest of the unburned gas; (2) after it has expanded; and (3) when combustion is complete and it has been compressed by subsequent burning of gas nearer the periphery. Calculations of flame speeds, temperatures, etc., have been made and tabulated for explosions of mixtures of ozone and oxygen. The speed of flame increases from the center of the bomb to the wall. At the same time the pressure and temperature of the gas about to be burned increases. The temperature gradient in the gas from the center to the wall has been calculated when the combustion is complete. A complete diagrammatic description is given for one explosion. It is shown that the temperature gradient actually existing in the bomb does not affect the specific heat results obtained by the usual method of calculating the final temperature from the maximum pressure by means of the gas law. It is pointed out that the practical coincidence of the pressure curve with the zero line in the first part of the time-pressure record is not due to a time lag between passage of the spark and ignition, but to the small fraction of gas which has burned during this time.

On the Decomposition Flame of Ozone at High Pressure

“…The first wave in the polarographic reduction is due to an adsorption phenomenon which results from the 1-electron reduction to a free radical (1, 2, 6) according to [3], which is evidently stabilized a t the mercury electrode.…”

Performance of a Plasma Jet Igniter

“…15. According to the data correlated from the literature by Andrews and Bradley (19), laminar burning velocities for methane-air mixtures at an F. 16 equivalence ratio of 0.6 are in the range of 6 to 17 em/sec. The asymptotic values of the curves presented in Fig.…”

Experimental assessment of various methods of determination of laminar flame speed in experiments with expanding spherical flames with positive Markstein lengths

“…It is worth noting, however, that u m is affected by dilatation, but such effects are not taken into account by theories of stretched flames, thus, impeding accurate extrapolation of raw data on S u u [16,27]. The compression perturbations (v) were of substantial importance in earlier experiments [15,29] when pressure history PðtÞ was recorded during an explosion and R f ðtÞ was calculated by processing the measured PðtÞ-curves. In contemporary studies, flame radius is measured using an optical diagnostic, e.g.…”

“…Various types of experimental facilities such as Bunsen, flat burner-stabilized, stagnation, or expanding spherical flames were developed in order to measure S 0 u , as reviewed recently by Egolfopoulos et al [1]. Historically, expanding spherical flames were most widely used to measure S 0 u for a long time starting from experiments by Lewis and von Elbe [15]. Moreover, such flames are currently considered to be the sole experimental approach to measuring S 0 u at pressures higher than 10 atm, e.g.…”