Youkichi Urano

Prediction of flammability of gases by using F-number analysis.

A novel method of predicting flammability limits has been proposed. This method utilizes a new flammability index called F-number. For this purpose, an empirical expression of F-number has been derived to account for the flammability characteristics of various organic substances. The analysis has been done by fitting to the observed values of F-number for a wide variety of organic gases and vapors. As a result, it has been found that F-number is an excellent tool to analyze the flammability characteristics of various substances. It has also been shown that the values of upper and lower flammability limits can be derived from F-number together with the stoichiometric concentration corrected for the effect of selective diffusion.

Premixed silaneoxygennitrogen flames

Abstract The burning velocities of lean premixed silaneoxygennitrogen flames were measured in the silane and oxygen concentration ranges from 1.6% to 2.9% and from 4% to 24%, respectively. Combustion product analyses and flame temperature measurements were also carried out. The burning velocity of a silaneair flame is around 55 cm/s at a silane concentration of 2%. For lean mixtures, when the oxygen concentration is reduced, dependence of burning velocity upon silane concentration decreases but does not significantly affect the flame temperature. For extremely lean flames, the degree of hydrogen production increases with decreasing silane, although silane is consumed almost completely. On the other hand, if the silane concentration exceeds stoichiometric, the burning velocity increases gradually with increasing silane concentration. In that case, silane as well as oxygen are consumed completely and, at the same time, hydrogen rather than water production becomes dominant. The mechanism of silane combustion is discussed, based on numerical calculations, where the mechanism used in the calculation is assembled by analogy of silane to methane combustion.

Incineration of CFC-12 by Burner Methods

Abstract A method of incinerating dichlorodifluoromethane (CFC-12) in the premised and diffusion flames has been developed. In the case of premixed CFC-12/methane/air flames, the burning velocity decreases with addition of CFC-12, but the amount of unreacted CFC-12 in Ihe burned gas is lower than the detection limit of the gas-chromatograph for molar ratios of CFC-12/methane smaller than around 0.2 when methane/air ratio is stoichiometric. The degree of destruction of CFC-12 decreases with increase of the CFC-12/methane ratio. No soot formation is observed in the range examined for the premixed flame experiments. On the other hand, in the case of CFC-12/methane diffusion flames in air, a large amount of soot formation is observed, although CFC-12 is also destructed almost completely in the range examined. These results indicate that the incineration melhod is useful and practical for the destruction of chloro-fluorocarbons.

Reinvestigation of Flammability Limits Measurement of Methane by the Conventional Vessel Method with AC Discharge Ignition

The flammability limits of methane have been reinvestigated by using the AC discharge ignition method. This work has partly been motivated by the necessity of evaluating the flammability characteristics of CFC alternatives. In the study, the effects of spark duration time and spark gap on the flammability limits of methane have extensively been explored. The resulting flammable range tends to become wide if the spark duration time is too long and/or the spark gap is too large. The effects of inadequate spark duration time and spark gap are exaggerated if the height of the experimental vessel is too small. As a result, the spark duration time of 0·1–0·2 sec combined with the spark gap of 6–8  mm has been found to make an optimum condition for the correct measurement of the flammability limits by the AC discharge ignition method.

Flammability limits of arsine and phosphine

Abstract Flammability limits of arsine (AsH 3 ) and phosphine (PH 3 ) in air and the dilution effect of nitrogen on the flammability limits were investigated experimentally. Experiments were done in a closed cylindrical vessel at atmospheric pressure. Mixtures were ignited by fusing a nichrome wire by electric current at the center of the vessel. Occurrence of explosion was determined from pressure history after ignition. Solid power deposit on the inner wall was also useful for the decision in the case of arsine test. The flammability limits were determined as follows. The flammability limit of arsine in air is 5.1–78%. The lower flammability limit of phosphine in air is 1.6%. Although the upper flammability limit of phosphine in air could not be determined experimentally because of its autoignitability, it was considered to be close to 100%.

Premixed disilane-oxygennitrogen flames

Abstract The burning velocity of lean premixed disilane-oxygennitrogen flames has been measured at disilane and oxygen concentrations ranging from 0.55% to 1.05% and from 2% to 21%, respectively. The general trend of burning velocities has been found to be very similar to those for silane flames. However, a few different points have also been noted; above stoichiometric concentrations part of the oxygen remains unconsumed through the reaction zone, though disilane is consumed almost completely. Even in oxygen-rich flames, oxygen consumption is always less than is required for complete combustion of disilane. Further, the general trend in hydrogen production is remarkably different from that of silane flames. A large number of compounds containing SiH and SiH 2 bonds are found in the solid products. The difference between disilane and silane combustion seems to be caused by the difference in the flame temperature.